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x86,objtool: Split UNWIND_HINT_EMPTY in two

PATCH Applied Josh Poimboeuf 4 participants 15 messages Mar 1, 2023 – Mar 25, 2023

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Josh Poimboeuf

author maintainer
#0 lore raw

cover x86,objtool: Split UNWIND_HINT_EMPTY in two

Based on tip/objtool/core.

Mark reported that the ORC unwinder incorrectly marks an unwind as reliable when the unwind terminates prematurely in the dark corners of return_to_handler() due to lack of information about the next frame.

The problem is UNWIND_HINT_EMPTY is used in two different situations:
end-of-stack marker and undefined stack state.

Split it up into UNWIND_HINT_END_OF_STACK and UNWIND_HINT_UNDEFINED.

Josh Poimboeuf (6):
objtool: Add objtool_types.h
objtool: Use relative pointers for annotations
objtool: Change UNWIND_HINT() argument order x86,objtool: Introduce ORC_TYPE_*
x86,objtool: Separate unret validation from unwind hints x86,objtool: Split UNWIND_HINT_EMPTY in two

 .../livepatch/reliable-stacktrace.rst         |   2 +-
 MAINTAINERS                                   |   2 +-
 arch/x86/entry/entry_64.S                     |  26 +--
 arch/x86/include/asm/nospec-branch.h          |  14 +-
 arch/x86/include/asm/orc_types.h              |  12 +-
 arch/x86/include/asm/unwind_hints.h           |  18 +-
 arch/x86/kernel/ftrace_64.S                   |   2 +-
 arch/x86/kernel/head_64.S                     |  17 +-
 arch/x86/kernel/relocate_kernel_64.S          |  10 +-
 arch/x86/kernel/unwind_orc.c                  |  27 ++-
 arch/x86/lib/retpoline.S                      |   6 +-
 arch/x86/platform/pvh/head.S                  |   2 +-
 arch/x86/xen/xen-asm.S                        |   4 +-
 arch/x86/xen/xen-head.S                       |   4 +-
 include/linux/objtool.h                       |  81 +++----
 include/linux/objtool_types.h                 |  57 +++++
 scripts/sorttable.h                           |   2 +-
 tools/arch/x86/include/asm/orc_types.h        |  12 +-
 tools/include/linux/objtool.h                 | 200 ------------------
 tools/include/linux/objtool_types.h           |  57 +++++
 tools/objtool/check.c                         |  69 ++++--
 tools/objtool/include/objtool/check.h         |   4 +-
 tools/objtool/orc_dump.c                      |  15 +-
 tools/objtool/orc_gen.c                       |  43 ++--
 tools/objtool/sync-check.sh                   |   2 +-
 25 files changed, 314 insertions(+), 374 deletions(-)
 create mode 100644 include/linux/objtool_types.h
 delete mode 100644 tools/include/linux/objtool.h
 create mode 100644 tools/include/linux/objtool_types.h
Signature · 1 line
2.39.1
author maintainer
#1 lore raw

PATCH 1/6 objtool: Add objtool_types.h

Reduce the amount of header sync churn by splitting the shared objtool.h types into a new file.

Signed-off-by Josh Poimboeuf <[email protected]>
---
 MAINTAINERS                         |   2 +-
 include/linux/objtool.h             |  42 +-----
 include/linux/objtool_types.h       |  48 +++++++
 tools/include/linux/objtool.h       | 200 ----------------------------
 tools/include/linux/objtool_types.h |  48 +++++++
 tools/objtool/check.c               |   2 +-
 tools/objtool/orc_dump.c            |   2 +-
 tools/objtool/orc_gen.c             |   2 +-
 tools/objtool/sync-check.sh         |   2 +-
 9 files changed, 102 insertions(+), 246 deletions(-)
 create mode 100644 include/linux/objtool_types.h
 delete mode 100644 tools/include/linux/objtool.h
 create mode 100644 tools/include/linux/objtool_types.h
MAINTAINERS +1 -1
index 2368a813e7ae..0873a33c3af9 100644
@@ -14988,8 +14988,8 @@ OBJTOOL
 M:	Josh Poimboeuf <[email protected]>
 M:	Peter Zijlstra <[email protected]>
 S:	Supported
+F:	include/linux/objtool*.h
 F:	tools/objtool/
-F:	include/linux/objtool.h
 
 OCELOT ETHERNET SWITCH DRIVER
 M:	Vladimir Oltean <[email protected]>
include/linux/objtool.h +1 -41

48 lines not on this page · raw message

include/linux/objtool_types.h new file +48 -0

48 lines not on this page · raw message

tools/include/linux/objtool.h deleted +0 -200

200 lines not on this page · raw message

tools/include/linux/objtool_types.h new file +48 -0

48 lines not on this page · raw message

tools/objtool/check.c +1 -1
index 5822de376d9a..3d4b650d3284 100644
@@ -17,7 +17,7 @@
 #include <objtool/warn.h>
 #include <objtool/endianness.h>
 
-#include <linux/objtool.h>
+#include <linux/objtool_types.h>
 #include <linux/hashtable.h>
 #include <linux/kernel.h>
 #include <linux/static_call_types.h>
tools/objtool/orc_dump.c +1 -1
index 2d8ebdcd1db3..9f6c528c26f2 100644
@@ -4,7 +4,7 @@
  */
 
 #include <unistd.h>
-#include <linux/objtool.h>
+#include <linux/objtool_types.h>
 #include <asm/orc_types.h>
 #include <objtool/objtool.h>
 #include <objtool/warn.h>
tools/objtool/orc_gen.c +1 -1
index 57a4527d5988..f49630a21e0f 100644
@@ -6,7 +6,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include <linux/objtool.h>
+#include <linux/objtool_types.h>
 #include <asm/orc_types.h>
 
 #include <objtool/check.h>
tools/objtool/sync-check.sh +1 -1
index 105a291ff8e7..81d120d05442 100755
@@ -6,7 +6,7 @@ if [ -z "$SRCARCH" ]; then
 	exit 1
 fi
 
-FILES="include/linux/objtool.h"
+FILES="include/linux/objtool_types.h"
 
 if [ "$SRCARCH" = "x86" ]; then
 FILES="$FILES
Signature · 1 line
2.39.1
merge bot Applied
#2 lore raw

[tip: objtool/core] objtool: Add objtool_types.h

The following commit has been merged into the objtool/core branch of tip:

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     f7515d9fe8fc4b80754cd4d98a5fcaee84adeebb
Gitweb:        https://git.kernel.org/tip/f7515d9fe8fc4b80754cd4d98a5fcaee84adeebb
Author:        Josh Poimboeuf <[email protected]>
AuthorDate:    Wed, 01 Mar 2023 07:13:07 -08:00
Committer:     Peter Zijlstra <[email protected]>
CommitterDate: Thu, 23 Mar 2023 23:18:56 +01:00

objtool: Add objtool_types.h

Reduce the amount of header sync churn by splitting the shared objtool.h types into a new file.

Signed-off-by Josh Poimboeuf <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Acked-by Peter Zijlstra (Intel) <[email protected]>
Link https://lore.kernel.org/r/dec622720851210ceafa12d4f4c5f9e73c832152.1677683419.git.jpoimboe@kernel.org open here
---
 MAINTAINERS                         |   2 +-
 include/linux/objtool.h             |  42 +------
 include/linux/objtool_types.h       |  48 ++++++-
 tools/include/linux/objtool.h       | 200 +---------------------------
 tools/include/linux/objtool_types.h |  48 ++++++-
 tools/objtool/check.c               |   2 +-
 tools/objtool/orc_dump.c            |   2 +-
 tools/objtool/orc_gen.c             |   2 +-
 tools/objtool/sync-check.sh         |   2 +-
 9 files changed, 102 insertions(+), 246 deletions(-)
 create mode 100644 include/linux/objtool_types.h
 delete mode 100644 tools/include/linux/objtool.h
 create mode 100644 tools/include/linux/objtool_types.h
MAINTAINERS +1 -1
index 8d5bc22..36e9e64 100644
@@ -15090,8 +15090,8 @@ OBJTOOL
 M:	Josh Poimboeuf <[email protected]>
 M:	Peter Zijlstra <[email protected]>
 S:	Supported
+F:	include/linux/objtool*.h
 F:	tools/objtool/
-F:	include/linux/objtool.h
 
 OCELOT ETHERNET SWITCH DRIVER
 M:	Vladimir Oltean <[email protected]>
include/linux/objtool.h +1 -41

48 lines not on this page · raw message

include/linux/objtool_types.h new file +48 -0

48 lines not on this page · raw message

tools/include/linux/objtool.h deleted +0 -200

200 lines not on this page · raw message

tools/include/linux/objtool_types.h new file +48 -0

48 lines not on this page · raw message

tools/objtool/check.c +1 -1
index 37c36dc..efc2baa 100644
@@ -17,7 +17,7 @@
 #include <objtool/warn.h>
 #include <objtool/endianness.h>
 
-#include <linux/objtool.h>
+#include <linux/objtool_types.h>
 #include <linux/hashtable.h>
 #include <linux/kernel.h>
 #include <linux/static_call_types.h>
tools/objtool/orc_dump.c +1 -1
index 2d8ebdc..9f6c528 100644
@@ -4,7 +4,7 @@
  */
 
 #include <unistd.h>
-#include <linux/objtool.h>
+#include <linux/objtool_types.h>
 #include <asm/orc_types.h>
 #include <objtool/objtool.h>
 #include <objtool/warn.h>
tools/objtool/orc_gen.c +1 -1
index 57a4527..f49630a 100644
@@ -6,7 +6,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include <linux/objtool.h>
+#include <linux/objtool_types.h>
 #include <asm/orc_types.h>
 
 #include <objtool/check.h>
tools/objtool/sync-check.sh +1 -1
index 105a291..81d120d 100755
@@ -6,7 +6,7 @@ if [ -z "$SRCARCH" ]; then
 	exit 1
 fi
 
-FILES="include/linux/objtool.h"
+FILES="include/linux/objtool_types.h"
 
 if [ "$SRCARCH" = "x86" ]; then
 FILES="$FILES
author maintainer
#3 lore raw

PATCH 2/6 objtool: Use relative pointers for annotations

In reply to Josh Poimboeuf

They produce the needed relocations while using half the space.

Signed-off-by Josh Poimboeuf <[email protected]>
---
 arch/x86/include/asm/nospec-branch.h |  6 +++---
 include/linux/objtool.h              | 12 ++++++------
 2 files changed, 9 insertions(+), 9 deletions(-)
arch/x86/include/asm/nospec-branch.h +3 -3
index 3ef70e54a858..78ed1546b775 100644
@@ -194,9 +194,9 @@
  * builds.
  */
 .macro ANNOTATE_RETPOLINE_SAFE
-	.Lannotate_\@:
+.Lhere_\@:
 	.pushsection .discard.retpoline_safe
-	_ASM_PTR .Lannotate_\@
+	.long .Lhere_\@ - .
 	.popsection
 .endm
 

@@ -318,7 +318,7 @@
 #define ANNOTATE_RETPOLINE_SAFE					\
 	"999:\n\t"						\
 	".pushsection .discard.retpoline_safe\n\t"		\
-	_ASM_PTR " 999b\n\t"					\
+	".long 999b - .\n\t"					\
 	".popsection\n\t"
 
 typedef u8 retpoline_thunk_t[RETPOLINE_THUNK_SIZE];
include/linux/objtool.h +6 -6
index 8375792acfc0..2b0258d273fc 100644
@@ -49,7 +49,7 @@
 #define ANNOTATE_NOENDBR					\
 	"986: \n\t"						\
 	".pushsection .discard.noendbr\n\t"			\
-	_ASM_PTR " 986b\n\t"					\
+	".long 986b - .\n\t"					\
 	".popsection\n\t"
 
 #define ASM_REACHABLE							\

@@ -67,7 +67,7 @@
 #define ANNOTATE_INTRA_FUNCTION_CALL				\
 	999:							\
 	.pushsection .discard.intra_function_calls;		\
-	.long 999b;						\
+	.long 999b - .;						\
 	.popsection;
 
 /*

@@ -92,10 +92,10 @@
  * inconsistencies.
  */
 .macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
-.Lunwind_hint_ip_\@:
+.Lhere_\@:
 	.pushsection .discard.unwind_hints
 		/* struct unwind_hint */
-		.long .Lunwind_hint_ip_\@ - .
+		.long .Lhere_\@ - .
 		.short \sp_offset
 		.byte \sp_reg
 		.byte \type

@@ -107,7 +107,7 @@
 
 .macro STACK_FRAME_NON_STANDARD func:req
 	.pushsection .discard.func_stack_frame_non_standard, "aw"
-	_ASM_PTR \func
+	.long \func - .
 	.popsection
 .endm
 

@@ -120,7 +120,7 @@
 .macro ANNOTATE_NOENDBR
 .Lhere_\@:
 	.pushsection .discard.noendbr
-	.quad	.Lhere_\@
+	.long	.Lhere_\@ - .
 	.popsection
 .endm
Signature · 1 line
2.39.1
merge bot Applied
#4 lore raw

[tip: objtool/core] objtool: Use relative pointers for annotations

The following commit has been merged into the objtool/core branch of tip:

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     1c0c1faf5692c18c127d044ecc0cc92c7bab3477
Gitweb:        https://git.kernel.org/tip/1c0c1faf5692c18c127d044ecc0cc92c7bab3477
Author:        Josh Poimboeuf <[email protected]>
AuthorDate:    Wed, 01 Mar 2023 07:13:08 -08:00
Committer:     Peter Zijlstra <[email protected]>
CommitterDate: Thu, 23 Mar 2023 23:18:56 +01:00

objtool: Use relative pointers for annotations

They produce the needed relocations while using half the space.

Signed-off-by Josh Poimboeuf <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Acked-by Peter Zijlstra (Intel) <[email protected]>
Link https://lore.kernel.org/r/bed05c64e28200220c9b1754a2f3ce71f73076ea.1677683419.git.jpoimboe@kernel.org open here
---
 arch/x86/include/asm/nospec-branch.h |  6 +++---
 include/linux/objtool.h              | 12 ++++++------
 2 files changed, 9 insertions(+), 9 deletions(-)
arch/x86/include/asm/nospec-branch.h +3 -3
index 3ef70e5..78ed154 100644
@@ -194,9 +194,9 @@
  * builds.
  */
 .macro ANNOTATE_RETPOLINE_SAFE
-	.Lannotate_\@:
+.Lhere_\@:
 	.pushsection .discard.retpoline_safe
-	_ASM_PTR .Lannotate_\@
+	.long .Lhere_\@ - .
 	.popsection
 .endm
 

@@ -318,7 +318,7 @@
 #define ANNOTATE_RETPOLINE_SAFE					\
 	"999:\n\t"						\
 	".pushsection .discard.retpoline_safe\n\t"		\
-	_ASM_PTR " 999b\n\t"					\
+	".long 999b - .\n\t"					\
 	".popsection\n\t"
 
 typedef u8 retpoline_thunk_t[RETPOLINE_THUNK_SIZE];
include/linux/objtool.h +6 -6
index 8375792..2b0258d 100644
@@ -49,7 +49,7 @@
 #define ANNOTATE_NOENDBR					\
 	"986: \n\t"						\
 	".pushsection .discard.noendbr\n\t"			\
-	_ASM_PTR " 986b\n\t"					\
+	".long 986b - .\n\t"					\
 	".popsection\n\t"
 
 #define ASM_REACHABLE							\

@@ -67,7 +67,7 @@
 #define ANNOTATE_INTRA_FUNCTION_CALL				\
 	999:							\
 	.pushsection .discard.intra_function_calls;		\
-	.long 999b;						\
+	.long 999b - .;						\
 	.popsection;
 
 /*

@@ -92,10 +92,10 @@
  * inconsistencies.
  */
 .macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
-.Lunwind_hint_ip_\@:
+.Lhere_\@:
 	.pushsection .discard.unwind_hints
 		/* struct unwind_hint */
-		.long .Lunwind_hint_ip_\@ - .
+		.long .Lhere_\@ - .
 		.short \sp_offset
 		.byte \sp_reg
 		.byte \type

@@ -107,7 +107,7 @@
 
 .macro STACK_FRAME_NON_STANDARD func:req
 	.pushsection .discard.func_stack_frame_non_standard, "aw"
-	_ASM_PTR \func
+	.long \func - .
 	.popsection
 .endm
 

@@ -120,7 +120,7 @@
 .macro ANNOTATE_NOENDBR
 .Lhere_\@:
 	.pushsection .discard.noendbr
-	.quad	.Lhere_\@
+	.long	.Lhere_\@ - .
 	.popsection
 .endm
author maintainer
#5 lore raw

PATCH 3/6 objtool: Change UNWIND_HINT() argument order

In reply to Josh Poimboeuf

The most important argument is 'type', make that one first.

Signed-off-by Josh Poimboeuf <[email protected]>
---
 arch/x86/include/asm/unwind_hints.h | 2 +-
 include/linux/objtool.h             | 5 ++---
 2 files changed, 3 insertions(+), 4 deletions(-)
arch/x86/include/asm/unwind_hints.h +1 -1
index e7c71750b309..97b392217c0f 100644
@@ -67,7 +67,7 @@
 #else
 
 #define UNWIND_HINT_FUNC \
-	UNWIND_HINT(ORC_REG_SP, 8, UNWIND_HINT_TYPE_FUNC, 0, 0)
+	UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0, 0)
 
 #endif /* __ASSEMBLY__ */
include/linux/objtool.h +2 -3
index 2b0258d273fc..725d7f0b6748 100644
@@ -10,7 +10,7 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(sp_reg, sp_offset, type, signal, end)	\
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end)	\
 	"987: \n\t"						\
 	".pushsection .discard.unwind_hints\n\t"		\
 	/* struct unwind_hint */				\

@@ -137,8 +137,7 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(sp_reg, sp_offset, type, signal, end) \
-	"\n\t"
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end) "\n\t"
 #define STACK_FRAME_NON_STANDARD(func)
 #define STACK_FRAME_NON_STANDARD_FP(func)
 #define ANNOTATE_NOENDBR
Signature · 1 line
2.39.1
merge bot Applied
#6 lore raw

[tip: objtool/core] objtool: Change UNWIND_HINT() argument order

The following commit has been merged into the objtool/core branch of tip:

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     d88ebba45dfe67114a6ac8c6514f2c65b6ed64c7
Gitweb:        https://git.kernel.org/tip/d88ebba45dfe67114a6ac8c6514f2c65b6ed64c7
Author:        Josh Poimboeuf <[email protected]>
AuthorDate:    Wed, 01 Mar 2023 07:13:09 -08:00
Committer:     Peter Zijlstra <[email protected]>
CommitterDate: Thu, 23 Mar 2023 23:18:57 +01:00

objtool: Change UNWIND_HINT() argument order

The most important argument is 'type', make that one first.

Signed-off-by Josh Poimboeuf <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Acked-by Peter Zijlstra (Intel) <[email protected]>
Link https://lore.kernel.org/r/d994f8c29376c5618c75698df28fc03b52d3a868.1677683419.git.jpoimboe@kernel.org open here
---
 arch/x86/include/asm/unwind_hints.h | 2 +-
 include/linux/objtool.h             | 5 ++---
 2 files changed, 3 insertions(+), 4 deletions(-)
arch/x86/include/asm/unwind_hints.h +1 -1
index e7c7175..97b3922 100644
@@ -67,7 +67,7 @@
 #else
 
 #define UNWIND_HINT_FUNC \
-	UNWIND_HINT(ORC_REG_SP, 8, UNWIND_HINT_TYPE_FUNC, 0, 0)
+	UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0, 0)
 
 #endif /* __ASSEMBLY__ */
include/linux/objtool.h +2 -3
index 2b0258d..725d7f0 100644
@@ -10,7 +10,7 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(sp_reg, sp_offset, type, signal, end)	\
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end)	\
 	"987: \n\t"						\
 	".pushsection .discard.unwind_hints\n\t"		\
 	/* struct unwind_hint */				\

@@ -137,8 +137,7 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(sp_reg, sp_offset, type, signal, end) \
-	"\n\t"
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end) "\n\t"
 #define STACK_FRAME_NON_STANDARD(func)
 #define STACK_FRAME_NON_STANDARD_FP(func)
 #define ANNOTATE_NOENDBR
author maintainer
#7 lore raw

PATCH 4/6 x86,objtool: Introduce ORC_TYPE_*

In reply to Josh Poimboeuf

Unwind hints and ORC entry types are two distinct things. Separate them out more explicitly.

Signed-off-by Josh Poimboeuf <[email protected]>
---
 arch/x86/include/asm/orc_types.h       |  4 ++++
 arch/x86/kernel/unwind_orc.c           | 12 ++++++------
 include/linux/objtool_types.h          |  1 +
 tools/arch/x86/include/asm/orc_types.h |  4 ++++
 tools/include/linux/objtool_types.h    |  1 +
 tools/objtool/orc_dump.c               |  7 +++----
 tools/objtool/orc_gen.c                | 19 +++++++++++++++++--
 7 files changed, 36 insertions(+), 12 deletions(-)
arch/x86/include/asm/orc_types.h +4 -0
index 1343a62106de..b4d4ec78589e 100644
@@ -39,6 +39,10 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
+#define ORC_TYPE_CALL			0
+#define ORC_TYPE_REGS			1
+#define ORC_TYPE_REGS_PARTIAL		2
+
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>
arch/x86/kernel/unwind_orc.c +6 -6
index 37307b40f8da..8348ac581de3 100644
@@ -133,7 +133,7 @@ static struct orc_entry null_orc_entry = {
 	.sp_offset = sizeof(long),
 	.sp_reg = ORC_REG_SP,
 	.bp_reg = ORC_REG_UNDEFINED,
-	.type = UNWIND_HINT_TYPE_CALL
+	.type = ORC_TYPE_CALL
 };
 
 #ifdef CONFIG_CALL_THUNKS

@@ -153,7 +153,7 @@ static struct orc_entry *orc_callthunk_find(unsigned long ip)
 
 /* Fake frame pointer entry -- used as a fallback for generated code */
 static struct orc_entry orc_fp_entry = {
-	.type		= UNWIND_HINT_TYPE_CALL,
+	.type		= ORC_TYPE_CALL,
 	.sp_reg		= ORC_REG_BP,
 	.sp_offset	= 16,
 	.bp_reg		= ORC_REG_PREV_SP,

@@ -554,7 +554,7 @@ bool unwind_next_frame(struct unwind_state *state)
 
 	/* Find IP, SP and possibly regs: */
 	switch (orc->type) {
-	case UNWIND_HINT_TYPE_CALL:
+	case ORC_TYPE_CALL:
 		ip_p = sp - sizeof(long);
 
 		if (!deref_stack_reg(state, ip_p, &state->ip))

@@ -567,7 +567,7 @@ bool unwind_next_frame(struct unwind_state *state)
 		state->prev_regs = NULL;
 		break;
 
-	case UNWIND_HINT_TYPE_REGS:
+	case ORC_TYPE_REGS:
 		if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
 			orc_warn_current("can't access registers at %pB\n",
 					 (void *)orig_ip);

@@ -590,13 +590,13 @@ bool unwind_next_frame(struct unwind_state *state)
 		state->full_regs = true;
 		break;
 
-	case UNWIND_HINT_TYPE_REGS_PARTIAL:
+	case ORC_TYPE_REGS_PARTIAL:
 		if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
 			orc_warn_current("can't access iret registers at %pB\n",
 					 (void *)orig_ip);
 			goto err;
 		}
-		/* See UNWIND_HINT_TYPE_REGS case comment. */
+		/* See ORC_TYPE_REGS case comment. */
 		state->ip = unwind_recover_rethook(state, state->ip,
 				(unsigned long *)(state->sp - sizeof(long)));
include/linux/objtool_types.h +1 -0
index 8513537a30ed..9a83468c0039 100644
@@ -40,6 +40,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_CALL		0
 #define UNWIND_HINT_TYPE_REGS		1
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+/* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
 #define UNWIND_HINT_TYPE_ENTRY		4
 #define UNWIND_HINT_TYPE_SAVE		5
tools/arch/x86/include/asm/orc_types.h +4 -0
index 1343a62106de..b4d4ec78589e 100644
@@ -39,6 +39,10 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
+#define ORC_TYPE_CALL			0
+#define ORC_TYPE_REGS			1
+#define ORC_TYPE_REGS_PARTIAL		2
+
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>
tools/include/linux/objtool_types.h +1 -0
index 8513537a30ed..9a83468c0039 100644
@@ -40,6 +40,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_CALL		0
 #define UNWIND_HINT_TYPE_REGS		1
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+/* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
 #define UNWIND_HINT_TYPE_ENTRY		4
 #define UNWIND_HINT_TYPE_SAVE		5
tools/objtool/orc_dump.c +3 -4
index 9f6c528c26f2..97ecbb8b9034 100644
@@ -4,7 +4,6 @@
  */
 
 #include <unistd.h>
-#include <linux/objtool_types.h>
 #include <asm/orc_types.h>
 #include <objtool/objtool.h>
 #include <objtool/warn.h>

@@ -39,11 +38,11 @@ static const char *reg_name(unsigned int reg)
 static const char *orc_type_name(unsigned int type)
 {
 	switch (type) {
-	case UNWIND_HINT_TYPE_CALL:
+	case ORC_TYPE_CALL:
 		return "call";
-	case UNWIND_HINT_TYPE_REGS:
+	case ORC_TYPE_REGS:
 		return "regs";
-	case UNWIND_HINT_TYPE_REGS_PARTIAL:
+	case ORC_TYPE_REGS_PARTIAL:
 		return "regs (partial)";
 	default:
 		return "?";
tools/objtool/orc_gen.c +17 -2
index f49630a21e0f..e85bbb996f6c 100644
@@ -26,6 +26,22 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 		return 0;
 	}
 
+	switch (cfi->type) {
+	case UNWIND_HINT_TYPE_CALL:
+		orc->type = ORC_TYPE_CALL;
+		break;
+	case UNWIND_HINT_TYPE_REGS:
+		orc->type = ORC_TYPE_REGS;
+		break;
+	case UNWIND_HINT_TYPE_REGS_PARTIAL:
+		orc->type = ORC_TYPE_REGS_PARTIAL;
+		break;
+	default:
+		WARN_FUNC("unknown unwind hint type %d",
+			  insn->sec, insn->offset, cfi->type);
+		return -1;
+	}
+
 	orc->end = cfi->end;
 	orc->signal = cfi->signal;
 

@@ -83,7 +99,6 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 
 	orc->sp_offset = cfi->cfa.offset;
 	orc->bp_offset = bp->offset;
-	orc->type = cfi->type;
 
 	return 0;
 }

@@ -151,7 +166,7 @@ int orc_create(struct objtool_file *file)
 	struct orc_entry null = {
 		.sp_reg  = ORC_REG_UNDEFINED,
 		.bp_reg  = ORC_REG_UNDEFINED,
-		.type    = UNWIND_HINT_TYPE_CALL,
+		.type    = ORC_TYPE_CALL,
 	};
 
 	/* Build a deduplicated list of ORC entries: */
Signature · 1 line
2.39.1
merge bot Applied
#8 lore raw

[tip: objtool/core] x86,objtool: Introduce ORC_TYPE_*

The following commit has been merged into the objtool/core branch of tip:

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     f902cfdd46aedd2afb3e8033223312dbf5fbb675
Gitweb:        https://git.kernel.org/tip/f902cfdd46aedd2afb3e8033223312dbf5fbb675
Author:        Josh Poimboeuf <[email protected]>
AuthorDate:    Wed, 01 Mar 2023 07:13:10 -08:00
Committer:     Peter Zijlstra <[email protected]>
CommitterDate: Thu, 23 Mar 2023 23:18:57 +01:00

x86,objtool: Introduce ORC_TYPE_*

Unwind hints and ORC entry types are two distinct things. Separate them out more explicitly.

Signed-off-by Josh Poimboeuf <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Acked-by Peter Zijlstra (Intel) <[email protected]>
Link https://lore.kernel.org/r/cc879d38fff8a43f8f7beb2fd56e35a5a384d7cd.1677683419.git.jpoimboe@kernel.org open here
---
 arch/x86/include/asm/orc_types.h       |  4 ++++
 arch/x86/kernel/unwind_orc.c           | 12 ++++++------
 include/linux/objtool_types.h          |  1 +
 tools/arch/x86/include/asm/orc_types.h |  4 ++++
 tools/include/linux/objtool_types.h    |  1 +
 tools/objtool/orc_dump.c               |  7 +++----
 tools/objtool/orc_gen.c                | 19 +++++++++++++++++--
 7 files changed, 36 insertions(+), 12 deletions(-)
arch/x86/include/asm/orc_types.h +4 -0
index 1343a62..b4d4ec7 100644
@@ -39,6 +39,10 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
+#define ORC_TYPE_CALL			0
+#define ORC_TYPE_REGS			1
+#define ORC_TYPE_REGS_PARTIAL		2
+
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>
arch/x86/kernel/unwind_orc.c +6 -6
index 37307b4..8348ac5 100644
@@ -133,7 +133,7 @@ static struct orc_entry null_orc_entry = {
 	.sp_offset = sizeof(long),
 	.sp_reg = ORC_REG_SP,
 	.bp_reg = ORC_REG_UNDEFINED,
-	.type = UNWIND_HINT_TYPE_CALL
+	.type = ORC_TYPE_CALL
 };
 
 #ifdef CONFIG_CALL_THUNKS

@@ -153,7 +153,7 @@ static struct orc_entry *orc_callthunk_find(unsigned long ip)
 
 /* Fake frame pointer entry -- used as a fallback for generated code */
 static struct orc_entry orc_fp_entry = {
-	.type		= UNWIND_HINT_TYPE_CALL,
+	.type		= ORC_TYPE_CALL,
 	.sp_reg		= ORC_REG_BP,
 	.sp_offset	= 16,
 	.bp_reg		= ORC_REG_PREV_SP,

@@ -554,7 +554,7 @@ bool unwind_next_frame(struct unwind_state *state)
 
 	/* Find IP, SP and possibly regs: */
 	switch (orc->type) {
-	case UNWIND_HINT_TYPE_CALL:
+	case ORC_TYPE_CALL:
 		ip_p = sp - sizeof(long);
 
 		if (!deref_stack_reg(state, ip_p, &state->ip))

@@ -567,7 +567,7 @@ bool unwind_next_frame(struct unwind_state *state)
 		state->prev_regs = NULL;
 		break;
 
-	case UNWIND_HINT_TYPE_REGS:
+	case ORC_TYPE_REGS:
 		if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {
 			orc_warn_current("can't access registers at %pB\n",
 					 (void *)orig_ip);

@@ -590,13 +590,13 @@ bool unwind_next_frame(struct unwind_state *state)
 		state->full_regs = true;
 		break;
 
-	case UNWIND_HINT_TYPE_REGS_PARTIAL:
+	case ORC_TYPE_REGS_PARTIAL:
 		if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {
 			orc_warn_current("can't access iret registers at %pB\n",
 					 (void *)orig_ip);
 			goto err;
 		}
-		/* See UNWIND_HINT_TYPE_REGS case comment. */
+		/* See ORC_TYPE_REGS case comment. */
 		state->ip = unwind_recover_rethook(state, state->ip,
 				(unsigned long *)(state->sp - sizeof(long)));
include/linux/objtool_types.h +1 -0
index 8513537..9a83468 100644
@@ -40,6 +40,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_CALL		0
 #define UNWIND_HINT_TYPE_REGS		1
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+/* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
 #define UNWIND_HINT_TYPE_ENTRY		4
 #define UNWIND_HINT_TYPE_SAVE		5
tools/arch/x86/include/asm/orc_types.h +4 -0
index 1343a62..b4d4ec7 100644
@@ -39,6 +39,10 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
+#define ORC_TYPE_CALL			0
+#define ORC_TYPE_REGS			1
+#define ORC_TYPE_REGS_PARTIAL		2
+
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>
tools/include/linux/objtool_types.h +1 -0
index 8513537..9a83468 100644
@@ -40,6 +40,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_CALL		0
 #define UNWIND_HINT_TYPE_REGS		1
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+/* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
 #define UNWIND_HINT_TYPE_ENTRY		4
 #define UNWIND_HINT_TYPE_SAVE		5
tools/objtool/orc_dump.c +3 -4
index 9f6c528..97ecbb8 100644
@@ -4,7 +4,6 @@
  */
 
 #include <unistd.h>
-#include <linux/objtool_types.h>
 #include <asm/orc_types.h>
 #include <objtool/objtool.h>
 #include <objtool/warn.h>

@@ -39,11 +38,11 @@ static const char *reg_name(unsigned int reg)
 static const char *orc_type_name(unsigned int type)
 {
 	switch (type) {
-	case UNWIND_HINT_TYPE_CALL:
+	case ORC_TYPE_CALL:
 		return "call";
-	case UNWIND_HINT_TYPE_REGS:
+	case ORC_TYPE_REGS:
 		return "regs";
-	case UNWIND_HINT_TYPE_REGS_PARTIAL:
+	case ORC_TYPE_REGS_PARTIAL:
 		return "regs (partial)";
 	default:
 		return "?";
tools/objtool/orc_gen.c +17 -2
index f49630a..e85bbb9 100644
@@ -26,6 +26,22 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 		return 0;
 	}
 
+	switch (cfi->type) {
+	case UNWIND_HINT_TYPE_CALL:
+		orc->type = ORC_TYPE_CALL;
+		break;
+	case UNWIND_HINT_TYPE_REGS:
+		orc->type = ORC_TYPE_REGS;
+		break;
+	case UNWIND_HINT_TYPE_REGS_PARTIAL:
+		orc->type = ORC_TYPE_REGS_PARTIAL;
+		break;
+	default:
+		WARN_FUNC("unknown unwind hint type %d",
+			  insn->sec, insn->offset, cfi->type);
+		return -1;
+	}
+
 	orc->end = cfi->end;
 	orc->signal = cfi->signal;
 

@@ -83,7 +99,6 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 
 	orc->sp_offset = cfi->cfa.offset;
 	orc->bp_offset = bp->offset;
-	orc->type = cfi->type;
 
 	return 0;
 }

@@ -151,7 +166,7 @@ int orc_create(struct objtool_file *file)
 	struct orc_entry null = {
 		.sp_reg  = ORC_REG_UNDEFINED,
 		.bp_reg  = ORC_REG_UNDEFINED,
-		.type    = UNWIND_HINT_TYPE_CALL,
+		.type    = ORC_TYPE_CALL,
 	};
 
 	/* Build a deduplicated list of ORC entries: */
author maintainer
#9 lore raw

PATCH 5/6 x86,objtool: Separate unret validation from unwind hints

In reply to Josh Poimboeuf

The ENTRY unwind hint type is serving double duty as both an empty unwind hint and an unret validation annotation.

Unret validation is unrelated to unwinding. Separate it out into its own annotation.

Signed-off-by Josh Poimboeuf <[email protected]>
---
 arch/x86/entry/entry_64.S             | 14 +++---
 arch/x86/include/asm/nospec-branch.h  |  8 ++--
 arch/x86/include/asm/unwind_hints.h   |  8 +++-
 arch/x86/kernel/head_64.S             |  5 ---
 include/linux/objtool.h               | 16 +++++++
 include/linux/objtool_types.h         |  5 +--
 tools/include/linux/objtool_types.h   |  5 +--
 tools/objtool/check.c                 | 65 ++++++++++++++++++---------
 tools/objtool/include/objtool/check.h |  4 +-
 9 files changed, 85 insertions(+), 45 deletions(-)
arch/x86/entry/entry_64.S +7 -7
index eccc3431e515..5b93eb7db0ab 100644
@@ -388,9 +388,9 @@ SYM_CODE_START(\asmsym)
 
 	.if \vector == X86_TRAP_BP
 		/* #BP advances %rip to the next instruction */
-		UNWIND_HINT_IRET_REGS offset=\has_error_code*8 signal=0
+		UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8 signal=0
 	.else
-		UNWIND_HINT_IRET_REGS offset=\has_error_code*8
+		UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8
 	.endif
 
 	ENDBR

@@ -461,7 +461,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_mce_db vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-	UNWIND_HINT_IRET_REGS
+	UNWIND_HINT_IRET_ENTRY
 	ENDBR
 	ASM_CLAC
 	cld

@@ -518,7 +518,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_vc vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-	UNWIND_HINT_IRET_REGS
+	UNWIND_HINT_IRET_ENTRY
 	ENDBR
 	ASM_CLAC
 	cld

@@ -582,7 +582,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_df vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-	UNWIND_HINT_IRET_REGS offset=8
+	UNWIND_HINT_IRET_ENTRY offset=8
 	ENDBR
 	ASM_CLAC
 	cld

@@ -1107,7 +1107,7 @@ SYM_CODE_START(error_entry)
 	FENCE_SWAPGS_KERNEL_ENTRY
 	CALL_DEPTH_ACCOUNT
 	leaq	8(%rsp), %rax			/* return pt_regs pointer */
-	ANNOTATE_UNRET_END
+	VALIDATE_UNRET_END
 	RET
 
 .Lbstep_iret:

@@ -1153,7 +1153,7 @@ SYM_CODE_END(error_return)
  *	      when PAGE_TABLE_ISOLATION is in use.  Do not clobber.
  */
 SYM_CODE_START(asm_exc_nmi)
-	UNWIND_HINT_IRET_REGS
+	UNWIND_HINT_IRET_ENTRY
 	ENDBR
 
 	/*
arch/x86/include/asm/nospec-branch.h +4 -4
index 78ed1546b775..edb2b0cb8efe 100644
@@ -210,8 +210,8 @@
  * Abuse ANNOTATE_RETPOLINE_SAFE on a NOP to indicate UNRET_END, should
  * eventually turn into it's own annotation.
  */
-.macro ANNOTATE_UNRET_END
-#ifdef CONFIG_DEBUG_ENTRY
+.macro VALIDATE_UNRET_END
+#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
 	ANNOTATE_RETPOLINE_SAFE
 	nop
 #endif

@@ -286,7 +286,7 @@
 .macro UNTRAIN_RET
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
 	defined(CONFIG_CALL_DEPTH_TRACKING)
-	ANNOTATE_UNRET_END
+	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\

@@ -297,7 +297,7 @@
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
 	defined(CONFIG_CALL_DEPTH_TRACKING)
-	ANNOTATE_UNRET_END
+	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
arch/x86/include/asm/unwind_hints.h +7 -1
index 97b392217c0f..4c0f28d665eb 100644
@@ -12,7 +12,8 @@
 .endm
 
 .macro UNWIND_HINT_ENTRY
-	UNWIND_HINT type=UNWIND_HINT_TYPE_ENTRY end=1
+	VALIDATE_UNRET_BEGIN
+	UNWIND_HINT_EMPTY
 .endm
 
 .macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 partial=0 signal=1

@@ -52,6 +53,11 @@
 	UNWIND_HINT_REGS base=\base offset=\offset partial=1 signal=\signal
 .endm
 
+.macro UNWIND_HINT_IRET_ENTRY base=%rsp offset=0 signal=1
+	VALIDATE_UNRET_BEGIN
+	UNWIND_HINT_IRET_REGS base=\base offset=\offset signal=\signal
+.endm
+
 .macro UNWIND_HINT_FUNC
 	UNWIND_HINT sp_reg=ORC_REG_SP sp_offset=8 type=UNWIND_HINT_TYPE_FUNC
 .endm
arch/x86/kernel/head_64.S +0 -5
index 222efd4a09bc..ee3ed15ee1f8 100644
@@ -390,8 +390,6 @@ SYM_CODE_START_NOALIGN(vc_boot_ghcb)
 	UNWIND_HINT_IRET_REGS offset=8
 	ENDBR
 
-	ANNOTATE_UNRET_END
-
 	/* Build pt_regs */
 	PUSH_AND_CLEAR_REGS
 

@@ -451,7 +449,6 @@ SYM_CODE_END(early_idt_handler_array)
 
 SYM_CODE_START_LOCAL(early_idt_handler_common)
 	UNWIND_HINT_IRET_REGS offset=16
-	ANNOTATE_UNRET_END
 	/*
 	 * The stack is the hardware frame, an error code or zero, and the
 	 * vector number.

@@ -501,8 +498,6 @@ SYM_CODE_START_NOALIGN(vc_no_ghcb)
 	UNWIND_HINT_IRET_REGS offset=8
 	ENDBR
 
-	ANNOTATE_UNRET_END
-
 	/* Build pt_regs */
 	PUSH_AND_CLEAR_REGS
include/linux/objtool.h +16 -0
index 725d7f0b6748..5aa475118820 100644
@@ -124,6 +124,22 @@
 	.popsection
 .endm
 
+/*
+ * Use objtool to validate the entry requirement that all code paths do
+ * VALIDATE_UNRET_END before RET.
+ *
+ * NOTE: The macro must be used at the beginning of a global symbol, otherwise
+ * it will be ignored.
+ */
+.macro VALIDATE_UNRET_BEGIN
+#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
+.Lhere_\@:
+	.pushsection .discard.validate_unret
+	.long	.Lhere_\@ - .
+	.popsection
+#endif
+.endm
+
 .macro REACHABLE
 .Lhere_\@:
 	.pushsection .discard.reachable
include/linux/objtool_types.h +2 -3
index 9a83468c0039..9787ad0f2ef4 100644
@@ -42,8 +42,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
 /* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_ENTRY		4
-#define UNWIND_HINT_TYPE_SAVE		5
-#define UNWIND_HINT_TYPE_RESTORE	6
+#define UNWIND_HINT_TYPE_SAVE		4
+#define UNWIND_HINT_TYPE_RESTORE	5
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
tools/include/linux/objtool_types.h +2 -3
index 9a83468c0039..9787ad0f2ef4 100644
@@ -42,8 +42,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
 /* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_ENTRY		4
-#define UNWIND_HINT_TYPE_SAVE		5
-#define UNWIND_HINT_TYPE_RESTORE	6
+#define UNWIND_HINT_TYPE_SAVE		4
+#define UNWIND_HINT_TYPE_RESTORE	5
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
tools/objtool/check.c +45 -20

140 lines not on this page · raw message

tools/objtool/include/objtool/check.h +2 -2
index 3e7c7004f7df..daa46f1f0965 100644
@@ -61,7 +61,7 @@ struct instruction {
 	    restore		: 1,
 	    retpoline_safe	: 1,
 	    noendbr		: 1,
-	    entry		: 1,
+	    unret		: 1,
 	    visited		: 4,
 	    no_reloc		: 1;
 		/* 10 bit hole */

@@ -92,7 +92,7 @@ static inline struct symbol *insn_func(struct instruction *insn)
 #define VISITED_BRANCH		0x01
 #define VISITED_BRANCH_UACCESS	0x02
 #define VISITED_BRANCH_MASK	0x03
-#define VISITED_ENTRY		0x04
+#define VISITED_UNRET		0x04
 
 static inline bool is_static_jump(struct instruction *insn)
 {
Signature · 1 line
2.39.1
merge bot Applied
#10 lore raw

[tip: objtool/core] x86,objtool: Separate unret validation from unwind hints

The following commit has been merged into the objtool/core branch of tip:

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     4708ea14bef314fc901857eefd65678236a9f2d9
Gitweb:        https://git.kernel.org/tip/4708ea14bef314fc901857eefd65678236a9f2d9
Author:        Josh Poimboeuf <[email protected]>
AuthorDate:    Wed, 01 Mar 2023 07:13:11 -08:00
Committer:     Peter Zijlstra <[email protected]>
CommitterDate: Thu, 23 Mar 2023 23:18:58 +01:00

x86,objtool: Separate unret validation from unwind hints

The ENTRY unwind hint type is serving double duty as both an empty unwind hint and an unret validation annotation.

Unret validation is unrelated to unwinding. Separate it out into its own annotation.

Signed-off-by Josh Poimboeuf <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Acked-by Peter Zijlstra (Intel) <[email protected]>
Link https://lore.kernel.org/r/ff7448d492ea21b86d8a90264b105fbd0d751077.1677683419.git.jpoimboe@kernel.org open here
---
 arch/x86/entry/entry_64.S             | 14 +++---
 arch/x86/include/asm/nospec-branch.h  |  8 +--
 arch/x86/include/asm/unwind_hints.h   |  8 ++-
 arch/x86/kernel/head_64.S             |  5 +--
 include/linux/objtool.h               | 16 ++++++-
 include/linux/objtool_types.h         |  5 +--
 tools/include/linux/objtool_types.h   |  5 +--
 tools/objtool/check.c                 | 65 ++++++++++++++++++--------
 tools/objtool/include/objtool/check.h |  4 +-
 9 files changed, 85 insertions(+), 45 deletions(-)
arch/x86/entry/entry_64.S +7 -7
index eccc343..5b93eb7 100644
@@ -388,9 +388,9 @@ SYM_CODE_START(\asmsym)
 
 	.if \vector == X86_TRAP_BP
 		/* #BP advances %rip to the next instruction */
-		UNWIND_HINT_IRET_REGS offset=\has_error_code*8 signal=0
+		UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8 signal=0
 	.else
-		UNWIND_HINT_IRET_REGS offset=\has_error_code*8
+		UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8
 	.endif
 
 	ENDBR

@@ -461,7 +461,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_mce_db vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-	UNWIND_HINT_IRET_REGS
+	UNWIND_HINT_IRET_ENTRY
 	ENDBR
 	ASM_CLAC
 	cld

@@ -518,7 +518,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_vc vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-	UNWIND_HINT_IRET_REGS
+	UNWIND_HINT_IRET_ENTRY
 	ENDBR
 	ASM_CLAC
 	cld

@@ -582,7 +582,7 @@ SYM_CODE_END(\asmsym)
  */
 .macro idtentry_df vector asmsym cfunc
 SYM_CODE_START(\asmsym)
-	UNWIND_HINT_IRET_REGS offset=8
+	UNWIND_HINT_IRET_ENTRY offset=8
 	ENDBR
 	ASM_CLAC
 	cld

@@ -1107,7 +1107,7 @@ SYM_CODE_START(error_entry)
 	FENCE_SWAPGS_KERNEL_ENTRY
 	CALL_DEPTH_ACCOUNT
 	leaq	8(%rsp), %rax			/* return pt_regs pointer */
-	ANNOTATE_UNRET_END
+	VALIDATE_UNRET_END
 	RET
 
 .Lbstep_iret:

@@ -1153,7 +1153,7 @@ SYM_CODE_END(error_return)
  *	      when PAGE_TABLE_ISOLATION is in use.  Do not clobber.
  */
 SYM_CODE_START(asm_exc_nmi)
-	UNWIND_HINT_IRET_REGS
+	UNWIND_HINT_IRET_ENTRY
 	ENDBR
 
 	/*
arch/x86/include/asm/nospec-branch.h +4 -4
index 78ed154..edb2b0c 100644
@@ -210,8 +210,8 @@
  * Abuse ANNOTATE_RETPOLINE_SAFE on a NOP to indicate UNRET_END, should
  * eventually turn into it's own annotation.
  */
-.macro ANNOTATE_UNRET_END
-#ifdef CONFIG_DEBUG_ENTRY
+.macro VALIDATE_UNRET_END
+#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
 	ANNOTATE_RETPOLINE_SAFE
 	nop
 #endif

@@ -286,7 +286,7 @@
 .macro UNTRAIN_RET
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
 	defined(CONFIG_CALL_DEPTH_TRACKING)
-	ANNOTATE_UNRET_END
+	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\

@@ -297,7 +297,7 @@
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
 	defined(CONFIG_CALL_DEPTH_TRACKING)
-	ANNOTATE_UNRET_END
+	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
arch/x86/include/asm/unwind_hints.h +7 -1
index 97b3922..4c0f28d 100644
@@ -12,7 +12,8 @@
 .endm
 
 .macro UNWIND_HINT_ENTRY
-	UNWIND_HINT type=UNWIND_HINT_TYPE_ENTRY end=1
+	VALIDATE_UNRET_BEGIN
+	UNWIND_HINT_EMPTY
 .endm
 
 .macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 partial=0 signal=1

@@ -52,6 +53,11 @@
 	UNWIND_HINT_REGS base=\base offset=\offset partial=1 signal=\signal
 .endm
 
+.macro UNWIND_HINT_IRET_ENTRY base=%rsp offset=0 signal=1
+	VALIDATE_UNRET_BEGIN
+	UNWIND_HINT_IRET_REGS base=\base offset=\offset signal=\signal
+.endm
+
 .macro UNWIND_HINT_FUNC
 	UNWIND_HINT sp_reg=ORC_REG_SP sp_offset=8 type=UNWIND_HINT_TYPE_FUNC
 .endm
arch/x86/kernel/head_64.S +0 -5
index 222efd4..ee3ed15 100644
@@ -390,8 +390,6 @@ SYM_CODE_START_NOALIGN(vc_boot_ghcb)
 	UNWIND_HINT_IRET_REGS offset=8
 	ENDBR
 
-	ANNOTATE_UNRET_END
-
 	/* Build pt_regs */
 	PUSH_AND_CLEAR_REGS
 

@@ -451,7 +449,6 @@ SYM_CODE_END(early_idt_handler_array)
 
 SYM_CODE_START_LOCAL(early_idt_handler_common)
 	UNWIND_HINT_IRET_REGS offset=16
-	ANNOTATE_UNRET_END
 	/*
 	 * The stack is the hardware frame, an error code or zero, and the
 	 * vector number.

@@ -501,8 +498,6 @@ SYM_CODE_START_NOALIGN(vc_no_ghcb)
 	UNWIND_HINT_IRET_REGS offset=8
 	ENDBR
 
-	ANNOTATE_UNRET_END
-
 	/* Build pt_regs */
 	PUSH_AND_CLEAR_REGS
include/linux/objtool.h +16 -0
index 725d7f0..5aa4751 100644
@@ -124,6 +124,22 @@
 	.popsection
 .endm
 
+/*
+ * Use objtool to validate the entry requirement that all code paths do
+ * VALIDATE_UNRET_END before RET.
+ *
+ * NOTE: The macro must be used at the beginning of a global symbol, otherwise
+ * it will be ignored.
+ */
+.macro VALIDATE_UNRET_BEGIN
+#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
+.Lhere_\@:
+	.pushsection .discard.validate_unret
+	.long	.Lhere_\@ - .
+	.popsection
+#endif
+.endm
+
 .macro REACHABLE
 .Lhere_\@:
 	.pushsection .discard.reachable
include/linux/objtool_types.h +2 -3
index 9a83468..9787ad0 100644
@@ -42,8 +42,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
 /* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_ENTRY		4
-#define UNWIND_HINT_TYPE_SAVE		5
-#define UNWIND_HINT_TYPE_RESTORE	6
+#define UNWIND_HINT_TYPE_SAVE		4
+#define UNWIND_HINT_TYPE_RESTORE	5
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
tools/include/linux/objtool_types.h +2 -3
index 9a83468..9787ad0 100644
@@ -42,8 +42,7 @@ struct unwind_hint {
 #define UNWIND_HINT_TYPE_REGS_PARTIAL	2
 /* The below hint types don't have corresponding ORC types */
 #define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_ENTRY		4
-#define UNWIND_HINT_TYPE_SAVE		5
-#define UNWIND_HINT_TYPE_RESTORE	6
+#define UNWIND_HINT_TYPE_SAVE		4
+#define UNWIND_HINT_TYPE_RESTORE	5
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
tools/objtool/check.c +45 -20

140 lines not on this page · raw message

tools/objtool/include/objtool/check.h +2 -2
index 3e7c700..daa46f1 100644
@@ -61,7 +61,7 @@ struct instruction {
 	    restore		: 1,
 	    retpoline_safe	: 1,
 	    noendbr		: 1,
-	    entry		: 1,
+	    unret		: 1,
 	    visited		: 4,
 	    no_reloc		: 1;
 		/* 10 bit hole */

@@ -92,7 +92,7 @@ static inline struct symbol *insn_func(struct instruction *insn)
 #define VISITED_BRANCH		0x01
 #define VISITED_BRANCH_UACCESS	0x02
 #define VISITED_BRANCH_MASK	0x03
-#define VISITED_ENTRY		0x04
+#define VISITED_UNRET		0x04
 
 static inline bool is_static_jump(struct instruction *insn)
 {
author maintainer
#11 lore raw

PATCH 6/6 x86,objtool: Split UNWIND_HINT_EMPTY in two

In reply to Josh Poimboeuf

Mark reported that the ORC unwinder incorrectly marks an unwind as reliable when the unwind terminates prematurely in the dark corners of return_to_handler() due to lack of information about the next frame.

The problem is UNWIND_HINT_EMPTY is used in two different situations:

1) The end of the kernel stack unwind before hitting user entry, boot code, or fork entry

2) A blind spot in ORC coverage where the unwinder has to bail due to lack of information about the next frame

The ORC unwinder has no way to tell the difference between the two. When it encounters an undefined stack state with 'end=1', it blindly marks the stack reliable, which can break the livepatch consistency model.

Fix it by splitting UNWIND_HINT_EMPTY into UNWIND_HINT_UNDEFINED and UNWIND_HINT_END_OF_STACK.

Reported-by Mark Rutland <[email protected]>
Signed-off-by Josh Poimboeuf <[email protected]>
---
 .../livepatch/reliable-stacktrace.rst         |  2 +-
 arch/x86/entry/entry_64.S                     | 12 ++++-----
 arch/x86/include/asm/orc_types.h              | 14 +++++-----
 arch/x86/include/asm/unwind_hints.h           | 12 ++++++---
 arch/x86/kernel/ftrace_64.S                   |  2 +-
 arch/x86/kernel/head_64.S                     | 12 ++++-----
 arch/x86/kernel/relocate_kernel_64.S          | 10 +++----
 arch/x86/kernel/unwind_orc.c                  | 15 +++++------
 arch/x86/lib/retpoline.S                      |  6 ++---
 arch/x86/platform/pvh/head.S                  |  2 +-
 arch/x86/xen/xen-asm.S                        |  4 +--
 arch/x86/xen/xen-head.S                       |  4 +--
 include/linux/objtool.h                       | 10 +++----
 include/linux/objtool_types.h                 | 27 ++++++++++++-------
 scripts/sorttable.h                           |  2 +-
 tools/arch/x86/include/asm/orc_types.h        | 14 +++++-----
 tools/include/linux/objtool_types.h           | 27 ++++++++++++-------
 tools/objtool/check.c                         |  2 +-
 tools/objtool/orc_dump.c                      |  8 ++++--
 tools/objtool/orc_gen.c                       | 26 +++++++++---------
 20 files changed, 116 insertions(+), 95 deletions(-)
Documentation/livepatch/reliable-stacktrace.rst +1 -1
index 67459d2ca2af..d56bb706172f 100644
@@ -183,7 +183,7 @@ trampoline or return trampoline. For example, considering the x86_64
 .. code-block:: none
 
    SYM_CODE_START(return_to_handler)
-           UNWIND_HINT_EMPTY
+           UNWIND_HINT_UNDEFINED
            subq  $24, %rsp
 
            /* Save the return values */
arch/x86/entry/entry_64.S +6 -6
index 5b93eb7db0ab..45e135be2a9f 100644
@@ -205,7 +205,7 @@ syscall_return_via_sysret:
 	 */
 	movq	%rsp, %rdi
 	movq	PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 
 	pushq	RSP-RDI(%rdi)	/* RSP */
 	pushq	(%rdi)		/* RDI */

@@ -286,7 +286,7 @@ SYM_FUNC_END(__switch_to_asm)
 .pushsection .text, "ax"
 	__FUNC_ALIGN
 SYM_CODE_START_NOALIGN(ret_from_fork)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR // copy_thread
 	CALL_DEPTH_ACCOUNT
 	movq	%rax, %rdi

@@ -303,7 +303,7 @@ SYM_CODE_START_NOALIGN(ret_from_fork)
 
 1:
 	/* kernel thread */
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	movq	%r12, %rdi
 	CALL_NOSPEC rbx
 	/*

@@ -643,7 +643,7 @@ SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL)
 	 */
 	movq	%rsp, %rdi
 	movq	PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 
 	/* Copy the IRET frame to the trampoline stack. */
 	pushq	6*8(%rdi)	/* SS */

@@ -869,7 +869,7 @@ SYM_CODE_END(exc_xen_hypervisor_callback)
  */
 	__FUNC_ALIGN
 SYM_CODE_START_NOALIGN(xen_failsafe_callback)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ENDBR
 	movl	%ds, %ecx
 	cmpw	%cx, 0x10(%rsp)

@@ -1520,7 +1520,7 @@ SYM_CODE_END(asm_exc_nmi)
  * MSRs to fully disable 32-bit SYSCALL.
  */
 SYM_CODE_START(ignore_sysret)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ENDBR
 	mov	$-ENOSYS, %eax
 	sysretl
arch/x86/include/asm/orc_types.h +7 -7
index b4d4ec78589e..46d7e06763c9 100644
@@ -39,9 +39,11 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
-#define ORC_TYPE_CALL			0
-#define ORC_TYPE_REGS			1
-#define ORC_TYPE_REGS_PARTIAL		2
+#define ORC_TYPE_UNDEFINED		0
+#define ORC_TYPE_END_OF_STACK		1
+#define ORC_TYPE_CALL			2
+#define ORC_TYPE_REGS			3
+#define ORC_TYPE_REGS_PARTIAL		4
 
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>

@@ -60,16 +62,14 @@ struct orc_entry {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	unsigned	sp_reg:4;
 	unsigned	bp_reg:4;
-	unsigned	type:2;
+	unsigned	type:3;
 	unsigned	signal:1;
-	unsigned	end:1;
 #elif defined(__BIG_ENDIAN_BITFIELD)
 	unsigned	bp_reg:4;
 	unsigned	sp_reg:4;
 	unsigned	unused:4;
-	unsigned	end:1;
 	unsigned	signal:1;
-	unsigned	type:2;
+	unsigned	type:3;
 #endif
 } __packed;
arch/x86/include/asm/unwind_hints.h +8 -4
index 4c0f28d665eb..01cb9692b160 100644
@@ -7,13 +7,17 @@
 
 #ifdef __ASSEMBLY__
 
-.macro UNWIND_HINT_EMPTY
-	UNWIND_HINT type=UNWIND_HINT_TYPE_CALL end=1
+.macro UNWIND_HINT_END_OF_STACK
+	UNWIND_HINT type=UNWIND_HINT_TYPE_END_OF_STACK
+.endm
+
+.macro UNWIND_HINT_UNDEFINED
+	UNWIND_HINT type=UNWIND_HINT_TYPE_UNDEFINED
 .endm
 
 .macro UNWIND_HINT_ENTRY
 	VALIDATE_UNRET_BEGIN
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 .endm
 
 .macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 partial=0 signal=1

@@ -73,7 +77,7 @@
 #else
 
 #define UNWIND_HINT_FUNC \
-	UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0, 0)
+	UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0)
 
 #endif /* __ASSEMBLY__ */
arch/x86/kernel/ftrace_64.S +1 -1
index 1265ad519249..0387732e9c3f 100644
@@ -340,7 +340,7 @@ STACK_FRAME_NON_STANDARD_FP(__fentry__)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 SYM_CODE_START(return_to_handler)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 	subq  $16, %rsp
arch/x86/kernel/head_64.S +6 -6
index ee3ed15ee1f8..8d8d25c64827 100644
@@ -42,7 +42,7 @@ L3_START_KERNEL = pud_index(__START_KERNEL_map)
 	__HEAD
 	.code64
 SYM_CODE_START_NOALIGN(startup_64)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	/*
 	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
 	 * and someone has loaded an identity mapped page table

@@ -105,7 +105,7 @@ SYM_CODE_START_NOALIGN(startup_64)
 	lretq
 
 .Lon_kernel_cs:
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 
 	/* Sanitize CPU configuration */
 	call verify_cpu

@@ -127,7 +127,7 @@ SYM_CODE_START_NOALIGN(startup_64)
 SYM_CODE_END(startup_64)
 
 SYM_CODE_START(secondary_startup_64)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 	/*
 	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,

@@ -156,7 +156,7 @@ SYM_CODE_START(secondary_startup_64)
 	 * verify_cpu() above to make sure NX is enabled.
 	 */
 SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 
 	/*

@@ -238,7 +238,7 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
 	ANNOTATE_RETPOLINE_SAFE
 	jmp	*%rax
 1:
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR // above
 
 	/*

@@ -371,7 +371,7 @@ SYM_CODE_END(secondary_startup_64)
  */
 SYM_CODE_START(start_cpu0)
 	ANNOTATE_NOENDBR
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	movq	initial_stack(%rip), %rsp
 	jmp	.Ljump_to_C_code
 SYM_CODE_END(start_cpu0)
arch/x86/kernel/relocate_kernel_64.S +5 -5
index 4a73351f87f8..56cab1bb25f5 100644
@@ -43,7 +43,7 @@
 	.code64
 SYM_CODE_START_NOALIGN(relocate_range)
 SYM_CODE_START_NOALIGN(relocate_kernel)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 	/*
 	 * %rdi indirection_page

@@ -113,7 +113,7 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
 SYM_CODE_END(relocate_kernel)
 
 SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	/* set return address to 0 if not preserving context */
 	pushq	$0
 	/* store the start address on the stack */

@@ -231,7 +231,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 SYM_CODE_END(identity_mapped)
 
 SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR // RET target, above
 	movq	RSP(%r8), %rsp
 	movq	CR4(%r8), %rax

@@ -256,8 +256,8 @@ SYM_CODE_END(virtual_mapped)
 
 	/* Do the copies */
 SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
-	UNWIND_HINT_EMPTY
-	movq	%rdi, %rcx 	/* Put the page_list in %rcx */
+	UNWIND_HINT_END_OF_STACK
+	movq	%rdi, %rcx	/* Put the page_list in %rcx */
 	xorl	%edi, %edi
 	xorl	%esi, %esi
 	jmp	1f
arch/x86/kernel/unwind_orc.c +6 -9
index 8348ac581de3..3ac50b7298d1 100644
@@ -158,7 +158,6 @@ static struct orc_entry orc_fp_entry = {
 	.sp_offset	= 16,
 	.bp_reg		= ORC_REG_PREV_SP,
 	.bp_offset	= -16,
-	.end		= 0,
 };
 
 static struct orc_entry *orc_find(unsigned long ip)

@@ -250,13 +249,13 @@ static int orc_sort_cmp(const void *_a, const void *_b)
 		return -1;
 
 	/*
-	 * The "weak" section terminator entries need to always be on the left
+	 * The "weak" section terminator entries need to always be first
 	 * to ensure the lookup code skips them in favor of real entries.
 	 * These terminator entries exist to handle any gaps created by
 	 * whitelisted .o files which didn't get objtool generation.
 	 */
 	orc_a = cur_orc_table + (a - cur_orc_ip_table);
-	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
+	return orc_a->type == ORC_TYPE_UNDEFINED ? -1 : 1;
 }
 
 void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,

@@ -474,14 +473,12 @@ bool unwind_next_frame(struct unwind_state *state)
 		 */
 		orc = &orc_fp_entry;
 		state->error = true;
-	}
-
-	/* End-of-stack check for kernel threads: */
-	if (orc->sp_reg == ORC_REG_UNDEFINED) {
-		if (!orc->end)
+	} else {
+		if (orc->type == ORC_TYPE_UNDEFINED)
 			goto err;
 
-		goto the_end;
+		if (orc->type == ORC_TYPE_END_OF_STACK)
+			goto the_end;
 	}
 
 	state->signal = orc->signal;
arch/x86/lib/retpoline.S +3 -3
index 5f61c65322be..27ef53fab6bd 100644
@@ -33,7 +33,7 @@
 
 	.align RETPOLINE_THUNK_SIZE
 SYM_INNER_LABEL(__x86_indirect_thunk_\reg, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 
 	ALTERNATIVE_2 __stringify(RETPOLINE \reg), \

@@ -75,7 +75,7 @@ SYM_CODE_END(__x86_indirect_thunk_array)
 	.align RETPOLINE_THUNK_SIZE
 
 SYM_INNER_LABEL(__x86_indirect_call_thunk_\reg, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 
 	CALL_DEPTH_ACCOUNT

@@ -103,7 +103,7 @@ SYM_CODE_END(__x86_indirect_call_thunk_array)
 	.align RETPOLINE_THUNK_SIZE
 
 SYM_INNER_LABEL(__x86_indirect_jump_thunk_\reg, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 	POLINE \reg
 	ANNOTATE_UNRET_SAFE
arch/x86/platform/pvh/head.S +1 -1
index 7fe564eaf228..c4365a05ab83 100644
@@ -50,7 +50,7 @@
 #define PVH_DS_SEL		(PVH_GDT_ENTRY_DS * 8)
 
 SYM_CODE_START_LOCAL(pvh_start_xen)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	cld
 
 	lgdt (_pa(gdt))
arch/x86/xen/xen-asm.S +2 -2
index 4a184f6e4e4d..08f1ceb9eb81 100644
@@ -165,7 +165,7 @@ xen_pv_trap asm_exc_xen_hypervisor_callback
 SYM_CODE_START(xen_early_idt_handler_array)
 	i = 0
 	.rept NUM_EXCEPTION_VECTORS
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ENDBR
 	pop %rcx
 	pop %r11

@@ -193,7 +193,7 @@ hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
  * rsp->rax		}
  */
 SYM_CODE_START(xen_iret)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 	pushq $0
 	jmp hypercall_iret
arch/x86/xen/xen-head.S +2 -2
index e36ea4268bd2..6eafdd17c242 100644
@@ -45,7 +45,7 @@ SYM_CODE_END(hypercall_page)
 #ifdef CONFIG_XEN_PV
 	__INIT
 SYM_CODE_START(startup_xen)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 	cld
 

@@ -71,7 +71,7 @@ SYM_CODE_END(startup_xen)
 #ifdef CONFIG_XEN_PV_SMP
 .pushsection .text
 SYM_CODE_START(asm_cpu_bringup_and_idle)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ENDBR
 
 	call cpu_bringup_and_idle
include/linux/objtool.h +4 -6
index 5aa475118820..03f82c2c2ebf 100644
@@ -10,7 +10,7 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end)	\
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal)	\
 	"987: \n\t"						\
 	".pushsection .discard.unwind_hints\n\t"		\
 	/* struct unwind_hint */				\

@@ -19,7 +19,6 @@
 	".byte " __stringify(sp_reg) "\n\t"			\
 	".byte " __stringify(type) "\n\t"			\
 	".byte " __stringify(signal) "\n\t"			\
-	".byte " __stringify(end) "\n\t"			\
 	".balign 4 \n\t"					\
 	".popsection\n\t"
 

@@ -91,7 +90,7 @@
  * the debuginfo as necessary.  It will also warn if it sees any
  * inconsistencies.
  */
-.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
+.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
 .Lhere_\@:
 	.pushsection .discard.unwind_hints
 		/* struct unwind_hint */

@@ -100,7 +99,6 @@
 		.byte \sp_reg
 		.byte \type
 		.byte \signal
-		.byte \end
 		.balign 4
 	.popsection
 .endm

@@ -153,14 +151,14 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end) "\n\t"
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal) "\n\t"
 #define STACK_FRAME_NON_STANDARD(func)
 #define STACK_FRAME_NON_STANDARD_FP(func)
 #define ANNOTATE_NOENDBR
 #define ASM_REACHABLE
 #else
 #define ANNOTATE_INTRA_FUNCTION_CALL
-.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
+.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
 .endm
 .macro STACK_FRAME_NON_STANDARD func:req
 .endm
include/linux/objtool_types.h +18 -9
index 9787ad0f2ef4..453a4f4ef39d 100644
@@ -16,12 +16,18 @@ struct unwind_hint {
 	u8		sp_reg;
 	u8		type;
 	u8		signal;
-	u8		end;
 };
 
 #endif /* __ASSEMBLY__ */
 
 /*
+ * UNWIND_HINT_TYPE_UNDEFINED: A blind spot in ORC coverage which can result in
+ * a truncated and unreliable stack unwind.
+ *
+ * UNWIND_HINT_TYPE_END_OF_STACK: The end of the kernel stack unwind before
+ * hitting user entry, boot code, or fork entry (when there are no pt_regs
+ * available).
+ *
  * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
  * (the caller's SP right before it made the call).  Used for all callable
  * functions, i.e. all C code and all callable asm functions.

@@ -32,17 +38,20 @@ struct unwind_hint {
  * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
  * sp_reg+sp_offset points to the iret return frame.
  *
- * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
+ * UNWIND_HINT_TYPE_FUNC: Generate the unwind metadata of a callable function.
  * Useful for code which doesn't have an ELF function annotation.
  *
- * UNWIND_HINT_ENTRY: machine entry without stack, SYSCALL/SYSENTER etc.
+ * UNWIND_HINT_TYPE_{SAVE,RESTORE}: Save the unwind metadata at a certain
+ * location so that it can be restored later.
  */
-#define UNWIND_HINT_TYPE_CALL		0
-#define UNWIND_HINT_TYPE_REGS		1
-#define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+#define UNWIND_HINT_TYPE_UNDEFINED	0
+#define UNWIND_HINT_TYPE_END_OF_STACK	1
+#define UNWIND_HINT_TYPE_CALL		2
+#define UNWIND_HINT_TYPE_REGS		3
+#define UNWIND_HINT_TYPE_REGS_PARTIAL	4
 /* The below hint types don't have corresponding ORC types */
-#define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_SAVE		4
-#define UNWIND_HINT_TYPE_RESTORE	5
+#define UNWIND_HINT_TYPE_FUNC		5
+#define UNWIND_HINT_TYPE_SAVE		6
+#define UNWIND_HINT_TYPE_RESTORE	7
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
scripts/sorttable.h +1 -1
index deb7c1d3e979..7bd0184380d3 100644
@@ -128,7 +128,7 @@ static int orc_sort_cmp(const void *_a, const void *_b)
 	 * whitelisted .o files which didn't get objtool generation.
 	 */
 	orc_a = g_orc_table + (a - g_orc_ip_table);
-	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
+	return orc_a->type == ORC_TYPE_UNDEFINED ? -1 : 1;
 }
 
 static void *sort_orctable(void *arg)
tools/arch/x86/include/asm/orc_types.h +7 -7
index b4d4ec78589e..46d7e06763c9 100644
@@ -39,9 +39,11 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
-#define ORC_TYPE_CALL			0
-#define ORC_TYPE_REGS			1
-#define ORC_TYPE_REGS_PARTIAL		2
+#define ORC_TYPE_UNDEFINED		0
+#define ORC_TYPE_END_OF_STACK		1
+#define ORC_TYPE_CALL			2
+#define ORC_TYPE_REGS			3
+#define ORC_TYPE_REGS_PARTIAL		4
 
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>

@@ -60,16 +62,14 @@ struct orc_entry {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	unsigned	sp_reg:4;
 	unsigned	bp_reg:4;
-	unsigned	type:2;
+	unsigned	type:3;
 	unsigned	signal:1;
-	unsigned	end:1;
 #elif defined(__BIG_ENDIAN_BITFIELD)
 	unsigned	bp_reg:4;
 	unsigned	sp_reg:4;
 	unsigned	unused:4;
-	unsigned	end:1;
 	unsigned	signal:1;
-	unsigned	type:2;
+	unsigned	type:3;
 #endif
 } __packed;
tools/include/linux/objtool_types.h +18 -9
index 9787ad0f2ef4..453a4f4ef39d 100644
@@ -16,12 +16,18 @@ struct unwind_hint {
 	u8		sp_reg;
 	u8		type;
 	u8		signal;
-	u8		end;
 };
 
 #endif /* __ASSEMBLY__ */
 
 /*
+ * UNWIND_HINT_TYPE_UNDEFINED: A blind spot in ORC coverage which can result in
+ * a truncated and unreliable stack unwind.
+ *
+ * UNWIND_HINT_TYPE_END_OF_STACK: The end of the kernel stack unwind before
+ * hitting user entry, boot code, or fork entry (when there are no pt_regs
+ * available).
+ *
  * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
  * (the caller's SP right before it made the call).  Used for all callable
  * functions, i.e. all C code and all callable asm functions.

@@ -32,17 +38,20 @@ struct unwind_hint {
  * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
  * sp_reg+sp_offset points to the iret return frame.
  *
- * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
+ * UNWIND_HINT_TYPE_FUNC: Generate the unwind metadata of a callable function.
  * Useful for code which doesn't have an ELF function annotation.
  *
- * UNWIND_HINT_ENTRY: machine entry without stack, SYSCALL/SYSENTER etc.
+ * UNWIND_HINT_TYPE_{SAVE,RESTORE}: Save the unwind metadata at a certain
+ * location so that it can be restored later.
  */
-#define UNWIND_HINT_TYPE_CALL		0
-#define UNWIND_HINT_TYPE_REGS		1
-#define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+#define UNWIND_HINT_TYPE_UNDEFINED	0
+#define UNWIND_HINT_TYPE_END_OF_STACK	1
+#define UNWIND_HINT_TYPE_CALL		2
+#define UNWIND_HINT_TYPE_REGS		3
+#define UNWIND_HINT_TYPE_REGS_PARTIAL	4
 /* The below hint types don't have corresponding ORC types */
-#define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_SAVE		4
-#define UNWIND_HINT_TYPE_RESTORE	5
+#define UNWIND_HINT_TYPE_FUNC		5
+#define UNWIND_HINT_TYPE_SAVE		6
+#define UNWIND_HINT_TYPE_RESTORE	7
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
tools/objtool/check.c +1 -1
index 226c2db3df89..d04711d4b2cd 100644
@@ -2240,6 +2240,7 @@ static void set_func_state(struct cfi_state *state)
 	memcpy(&state->regs, &initial_func_cfi.regs,
 	       CFI_NUM_REGS * sizeof(struct cfi_reg));
 	state->stack_size = initial_func_cfi.cfa.offset;
+	state->type = UNWIND_HINT_TYPE_CALL;
 }
 
 static int read_unwind_hints(struct objtool_file *file)

@@ -2324,7 +2325,6 @@ static int read_unwind_hints(struct objtool_file *file)
 		cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
 		cfi.type = hint->type;
 		cfi.signal = hint->signal;
-		cfi.end = hint->end;
 
 		insn->cfi = cfi_hash_find_or_add(&cfi);
 	}
tools/objtool/orc_dump.c +6 -2
index 97ecbb8b9034..0e183bb1c720 100644
@@ -38,6 +38,10 @@ static const char *reg_name(unsigned int reg)
 static const char *orc_type_name(unsigned int type)
 {
 	switch (type) {
+	case ORC_TYPE_UNDEFINED:
+		return "(und)";
+	case ORC_TYPE_END_OF_STACK:
+		return "end";
 	case ORC_TYPE_CALL:
 		return "call";
 	case ORC_TYPE_REGS:

@@ -201,6 +205,7 @@ int orc_dump(const char *_objname)
 			printf("%llx:", (unsigned long long)(orc_ip_addr + (i * sizeof(int)) + orc_ip[i]));
 		}
 
+		printf("type:%s", orc_type_name(orc[i].type));
 
 		printf(" sp:");
 

@@ -210,8 +215,7 @@ int orc_dump(const char *_objname)
 
 		print_reg(orc[i].bp_reg, bswap_if_needed(&dummy_elf, orc[i].bp_offset));
 
-		printf(" type:%s signal:%d end:%d\n",
-		       orc_type_name(orc[i].type), orc[i].signal, orc[i].end);
+		printf(" signal:%d\n", orc[i].signal);
 	}
 
 	elf_end(elf);
tools/objtool/orc_gen.c +13 -13
index e85bbb996f6c..b327f9ccfe73 100644
@@ -21,12 +21,22 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 	memset(orc, 0, sizeof(*orc));
 
 	if (!cfi) {
-		orc->end = 0;
-		orc->sp_reg = ORC_REG_UNDEFINED;
+		/*
+		 * This is usually either unreachable nops/traps (which don't
+		 * trigger unreachable instruction warnings), or
+		 * STACK_FRAME_NON_STANDARD functions.
+		 */
+		orc->type = ORC_TYPE_UNDEFINED;
 		return 0;
 	}
 
 	switch (cfi->type) {
+	case UNWIND_HINT_TYPE_UNDEFINED:
+		orc->type = ORC_TYPE_UNDEFINED;
+		return 0;
+	case UNWIND_HINT_TYPE_END_OF_STACK:
+		orc->type = ORC_TYPE_END_OF_STACK;
+		return 0;
 	case UNWIND_HINT_TYPE_CALL:
 		orc->type = ORC_TYPE_CALL;
 		break;

@@ -42,14 +52,8 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 		return -1;
 	}
 
-	orc->end = cfi->end;
 	orc->signal = cfi->signal;
 
-	if (cfi->cfa.base == CFI_UNDEFINED) {
-		orc->sp_reg = ORC_REG_UNDEFINED;
-		return 0;
-	}
-
 	switch (cfi->cfa.base) {
 	case CFI_SP:
 		orc->sp_reg = ORC_REG_SP;

@@ -163,11 +167,7 @@ int orc_create(struct objtool_file *file)
 	struct orc_list_entry *entry;
 	struct list_head orc_list;
 
-	struct orc_entry null = {
-		.sp_reg  = ORC_REG_UNDEFINED,
-		.bp_reg  = ORC_REG_UNDEFINED,
-		.type    = ORC_TYPE_CALL,
-	};
+	struct orc_entry null = { .type = ORC_TYPE_UNDEFINED };
 
 	/* Build a deduplicated list of ORC entries: */
 	INIT_LIST_HEAD(&orc_list);
Signature · 1 line
2.39.1
maintainer Acked-by on v1 6/6
#12 lore raw

arch/x86/kernel/ftrace_64.S STACK_FRAME_NON_STANDARD_FP(__fentry__) · line 346

Quoted 13 lines · On Wed, 1 Mar 2023 07:13:12 -0800 Josh Poimboeuf <[email protected]> wrote:
arch/x86/kernel/ftrace_64.S +1 -1
index 1265ad519249..0387732e9c3f 100644
@@ -340,7 +340,7 @@ STACK_FRAME_NON_STANDARD_FP(__fentry__)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 SYM_CODE_START(return_to_handler)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 	subq  $16, %rsp
Acked-by Steven Rostedt (Google) <[email protected]>

-- Steve

merge bot Applied
#13 lore raw
In reply to Josh Poimboeuf
The following commit has been merged into the objtool/core branch of tip:

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     fb799447ae2974a07907906dff5bd4b9e47b7123
Gitweb:        https://git.kernel.org/tip/fb799447ae2974a07907906dff5bd4b9e47b7123
Author:        Josh Poimboeuf <[email protected]>
AuthorDate:    Wed, 01 Mar 2023 07:13:12 -08:00
Committer:     Peter Zijlstra <[email protected]>
CommitterDate: Thu, 23 Mar 2023 23:18:58 +01:00

x86,objtool: Split UNWIND_HINT_EMPTY in two

Mark reported that the ORC unwinder incorrectly marks an unwind as reliable when the unwind terminates prematurely in the dark corners of return_to_handler() due to lack of information about the next frame.

The problem is UNWIND_HINT_EMPTY is used in two different situations:

1) The end of the kernel stack unwind before hitting user entry, boot code, or fork entry

2) A blind spot in ORC coverage where the unwinder has to bail due to lack of information about the next frame

The ORC unwinder has no way to tell the difference between the two. When it encounters an undefined stack state with 'end=1', it blindly marks the stack reliable, which can break the livepatch consistency model.

Fix it by splitting UNWIND_HINT_EMPTY into UNWIND_HINT_UNDEFINED and UNWIND_HINT_END_OF_STACK.

Reported-by Mark Rutland <[email protected]>
Signed-off-by Josh Poimboeuf <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Acked-by Steven Rostedt (Google) <[email protected]>
Acked-by Peter Zijlstra (Intel) <[email protected]>
Link https://lore.kernel.org/r/fd6212c8b450d3564b855e1cb48404d6277b4d9f.1677683419.git.jpoimboe@kernel.org open here
---
 Documentation/livepatch/reliable-stacktrace.rst |  2 +-
 arch/x86/entry/entry_64.S                       | 12 +++----
 arch/x86/include/asm/orc_types.h                | 14 ++++----
 arch/x86/include/asm/unwind_hints.h             | 12 ++++---
 arch/x86/kernel/ftrace_64.S                     |  2 +-
 arch/x86/kernel/head_64.S                       | 12 +++----
 arch/x86/kernel/relocate_kernel_64.S            | 10 +++---
 arch/x86/kernel/unwind_orc.c                    | 15 +++------
 arch/x86/lib/retpoline.S                        |  6 ++--
 arch/x86/platform/pvh/head.S                    |  2 +-
 arch/x86/xen/xen-asm.S                          |  4 +-
 arch/x86/xen/xen-head.S                         |  4 +-
 include/linux/objtool.h                         | 10 ++----
 include/linux/objtool_types.h                   | 27 ++++++++++------
 scripts/sorttable.h                             |  2 +-
 tools/arch/x86/include/asm/orc_types.h          | 14 ++++----
 tools/include/linux/objtool_types.h             | 27 ++++++++++------
 tools/objtool/check.c                           |  2 +-
 tools/objtool/orc_dump.c                        |  8 +++--
 tools/objtool/orc_gen.c                         | 26 +++++++--------
 20 files changed, 116 insertions(+), 95 deletions(-)
Documentation/livepatch/reliable-stacktrace.rst +1 -1
index 67459d2..d56bb70 100644
@@ -183,7 +183,7 @@ trampoline or return trampoline. For example, considering the x86_64
 .. code-block:: none
 
    SYM_CODE_START(return_to_handler)
-           UNWIND_HINT_EMPTY
+           UNWIND_HINT_UNDEFINED
            subq  $24, %rsp
 
            /* Save the return values */
arch/x86/entry/entry_64.S +6 -6
index 5b93eb7..45e135b 100644
@@ -205,7 +205,7 @@ syscall_return_via_sysret:
 	 */
 	movq	%rsp, %rdi
 	movq	PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 
 	pushq	RSP-RDI(%rdi)	/* RSP */
 	pushq	(%rdi)		/* RDI */

@@ -286,7 +286,7 @@ SYM_FUNC_END(__switch_to_asm)
 .pushsection .text, "ax"
 	__FUNC_ALIGN
 SYM_CODE_START_NOALIGN(ret_from_fork)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR // copy_thread
 	CALL_DEPTH_ACCOUNT
 	movq	%rax, %rdi

@@ -303,7 +303,7 @@ SYM_CODE_START_NOALIGN(ret_from_fork)
 
 1:
 	/* kernel thread */
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	movq	%r12, %rdi
 	CALL_NOSPEC rbx
 	/*

@@ -643,7 +643,7 @@ SYM_INNER_LABEL(swapgs_restore_regs_and_return_to_usermode, SYM_L_GLOBAL)
 	 */
 	movq	%rsp, %rdi
 	movq	PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 
 	/* Copy the IRET frame to the trampoline stack. */
 	pushq	6*8(%rdi)	/* SS */

@@ -869,7 +869,7 @@ SYM_CODE_END(exc_xen_hypervisor_callback)
  */
 	__FUNC_ALIGN
 SYM_CODE_START_NOALIGN(xen_failsafe_callback)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ENDBR
 	movl	%ds, %ecx
 	cmpw	%cx, 0x10(%rsp)

@@ -1520,7 +1520,7 @@ SYM_CODE_END(asm_exc_nmi)
  * MSRs to fully disable 32-bit SYSCALL.
  */
 SYM_CODE_START(ignore_sysret)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ENDBR
 	mov	$-ENOSYS, %eax
 	sysretl
arch/x86/include/asm/orc_types.h +7 -7
index b4d4ec7..46d7e06 100644
@@ -39,9 +39,11 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
-#define ORC_TYPE_CALL			0
-#define ORC_TYPE_REGS			1
-#define ORC_TYPE_REGS_PARTIAL		2
+#define ORC_TYPE_UNDEFINED		0
+#define ORC_TYPE_END_OF_STACK		1
+#define ORC_TYPE_CALL			2
+#define ORC_TYPE_REGS			3
+#define ORC_TYPE_REGS_PARTIAL		4
 
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>

@@ -60,16 +62,14 @@ struct orc_entry {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	unsigned	sp_reg:4;
 	unsigned	bp_reg:4;
-	unsigned	type:2;
+	unsigned	type:3;
 	unsigned	signal:1;
-	unsigned	end:1;
 #elif defined(__BIG_ENDIAN_BITFIELD)
 	unsigned	bp_reg:4;
 	unsigned	sp_reg:4;
 	unsigned	unused:4;
-	unsigned	end:1;
 	unsigned	signal:1;
-	unsigned	type:2;
+	unsigned	type:3;
 #endif
 } __packed;
arch/x86/include/asm/unwind_hints.h +8 -4
index 4c0f28d..01cb969 100644
@@ -7,13 +7,17 @@
 
 #ifdef __ASSEMBLY__
 
-.macro UNWIND_HINT_EMPTY
-	UNWIND_HINT type=UNWIND_HINT_TYPE_CALL end=1
+.macro UNWIND_HINT_END_OF_STACK
+	UNWIND_HINT type=UNWIND_HINT_TYPE_END_OF_STACK
+.endm
+
+.macro UNWIND_HINT_UNDEFINED
+	UNWIND_HINT type=UNWIND_HINT_TYPE_UNDEFINED
 .endm
 
 .macro UNWIND_HINT_ENTRY
 	VALIDATE_UNRET_BEGIN
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 .endm
 
 .macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 partial=0 signal=1

@@ -73,7 +77,7 @@
 #else
 
 #define UNWIND_HINT_FUNC \
-	UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0, 0)
+	UNWIND_HINT(UNWIND_HINT_TYPE_FUNC, ORC_REG_SP, 8, 0)
 
 #endif /* __ASSEMBLY__ */
arch/x86/kernel/ftrace_64.S +1 -1
index 1265ad5..0387732 100644
@@ -340,7 +340,7 @@ STACK_FRAME_NON_STANDARD_FP(__fentry__)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 SYM_CODE_START(return_to_handler)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 	subq  $16, %rsp
arch/x86/kernel/head_64.S +6 -6
index ee3ed15..8d8d25c 100644
@@ -42,7 +42,7 @@ L3_START_KERNEL = pud_index(__START_KERNEL_map)
 	__HEAD
 	.code64
 SYM_CODE_START_NOALIGN(startup_64)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	/*
 	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
 	 * and someone has loaded an identity mapped page table

@@ -105,7 +105,7 @@ SYM_CODE_START_NOALIGN(startup_64)
 	lretq
 
 .Lon_kernel_cs:
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 
 	/* Sanitize CPU configuration */
 	call verify_cpu

@@ -127,7 +127,7 @@ SYM_CODE_START_NOALIGN(startup_64)
 SYM_CODE_END(startup_64)
 
 SYM_CODE_START(secondary_startup_64)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 	/*
 	 * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,

@@ -156,7 +156,7 @@ SYM_CODE_START(secondary_startup_64)
 	 * verify_cpu() above to make sure NX is enabled.
 	 */
 SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 
 	/*

@@ -238,7 +238,7 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
 	ANNOTATE_RETPOLINE_SAFE
 	jmp	*%rax
 1:
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR // above
 
 	/*

@@ -371,7 +371,7 @@ SYM_CODE_END(secondary_startup_64)
  */
 SYM_CODE_START(start_cpu0)
 	ANNOTATE_NOENDBR
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	movq	initial_stack(%rip), %rsp
 	jmp	.Ljump_to_C_code
 SYM_CODE_END(start_cpu0)
arch/x86/kernel/relocate_kernel_64.S +5 -5
index 4a73351..56cab1b 100644
@@ -43,7 +43,7 @@
 	.code64
 SYM_CODE_START_NOALIGN(relocate_range)
 SYM_CODE_START_NOALIGN(relocate_kernel)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 	/*
 	 * %rdi indirection_page

@@ -113,7 +113,7 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
 SYM_CODE_END(relocate_kernel)
 
 SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	/* set return address to 0 if not preserving context */
 	pushq	$0
 	/* store the start address on the stack */

@@ -231,7 +231,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 SYM_CODE_END(identity_mapped)
 
 SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR // RET target, above
 	movq	RSP(%r8), %rsp
 	movq	CR4(%r8), %rax

@@ -256,8 +256,8 @@ SYM_CODE_END(virtual_mapped)
 
 	/* Do the copies */
 SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
-	UNWIND_HINT_EMPTY
-	movq	%rdi, %rcx 	/* Put the page_list in %rcx */
+	UNWIND_HINT_END_OF_STACK
+	movq	%rdi, %rcx	/* Put the page_list in %rcx */
 	xorl	%edi, %edi
 	xorl	%esi, %esi
 	jmp	1f
arch/x86/kernel/unwind_orc.c +6 -9
index 8348ac5..3ac50b7 100644
@@ -158,7 +158,6 @@ static struct orc_entry orc_fp_entry = {
 	.sp_offset	= 16,
 	.bp_reg		= ORC_REG_PREV_SP,
 	.bp_offset	= -16,
-	.end		= 0,
 };
 
 static struct orc_entry *orc_find(unsigned long ip)

@@ -250,13 +249,13 @@ static int orc_sort_cmp(const void *_a, const void *_b)
 		return -1;
 
 	/*
-	 * The "weak" section terminator entries need to always be on the left
+	 * The "weak" section terminator entries need to always be first
 	 * to ensure the lookup code skips them in favor of real entries.
 	 * These terminator entries exist to handle any gaps created by
 	 * whitelisted .o files which didn't get objtool generation.
 	 */
 	orc_a = cur_orc_table + (a - cur_orc_ip_table);
-	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
+	return orc_a->type == ORC_TYPE_UNDEFINED ? -1 : 1;
 }
 
 void unwind_module_init(struct module *mod, void *_orc_ip, size_t orc_ip_size,

@@ -474,14 +473,12 @@ bool unwind_next_frame(struct unwind_state *state)
 		 */
 		orc = &orc_fp_entry;
 		state->error = true;
-	}
-
-	/* End-of-stack check for kernel threads: */
-	if (orc->sp_reg == ORC_REG_UNDEFINED) {
-		if (!orc->end)
+	} else {
+		if (orc->type == ORC_TYPE_UNDEFINED)
 			goto err;
 
-		goto the_end;
+		if (orc->type == ORC_TYPE_END_OF_STACK)
+			goto the_end;
 	}
 
 	state->signal = orc->signal;
arch/x86/lib/retpoline.S +3 -3
index 5f61c65..27ef53f 100644
@@ -33,7 +33,7 @@
 
 	.align RETPOLINE_THUNK_SIZE
 SYM_INNER_LABEL(__x86_indirect_thunk_\reg, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 
 	ALTERNATIVE_2 __stringify(RETPOLINE \reg), \

@@ -75,7 +75,7 @@ SYM_CODE_END(__x86_indirect_thunk_array)
 	.align RETPOLINE_THUNK_SIZE
 
 SYM_INNER_LABEL(__x86_indirect_call_thunk_\reg, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 
 	CALL_DEPTH_ACCOUNT

@@ -103,7 +103,7 @@ SYM_CODE_END(__x86_indirect_call_thunk_array)
 	.align RETPOLINE_THUNK_SIZE
 
 SYM_INNER_LABEL(__x86_indirect_jump_thunk_\reg, SYM_L_GLOBAL)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 	POLINE \reg
 	ANNOTATE_UNRET_SAFE
arch/x86/platform/pvh/head.S +1 -1
index 7fe564e..c4365a0 100644
@@ -50,7 +50,7 @@
 #define PVH_DS_SEL		(PVH_GDT_ENTRY_DS * 8)
 
 SYM_CODE_START_LOCAL(pvh_start_xen)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	cld
 
 	lgdt (_pa(gdt))
arch/x86/xen/xen-asm.S +2 -2
index 4a184f6..08f1ceb 100644
@@ -165,7 +165,7 @@ xen_pv_trap asm_exc_xen_hypervisor_callback
 SYM_CODE_START(xen_early_idt_handler_array)
 	i = 0
 	.rept NUM_EXCEPTION_VECTORS
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ENDBR
 	pop %rcx
 	pop %r11

@@ -193,7 +193,7 @@ hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
  * rsp->rax		}
  */
 SYM_CODE_START(xen_iret)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_UNDEFINED
 	ANNOTATE_NOENDBR
 	pushq $0
 	jmp hypercall_iret
arch/x86/xen/xen-head.S +2 -2
index e36ea42..6eafdd1 100644
@@ -45,7 +45,7 @@ SYM_CODE_END(hypercall_page)
 #ifdef CONFIG_XEN_PV
 	__INIT
 SYM_CODE_START(startup_xen)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ANNOTATE_NOENDBR
 	cld
 

@@ -71,7 +71,7 @@ SYM_CODE_END(startup_xen)
 #ifdef CONFIG_XEN_PV_SMP
 .pushsection .text
 SYM_CODE_START(asm_cpu_bringup_and_idle)
-	UNWIND_HINT_EMPTY
+	UNWIND_HINT_END_OF_STACK
 	ENDBR
 
 	call cpu_bringup_and_idle
include/linux/objtool.h +4 -6
index 5aa4751..03f82c2 100644
@@ -10,7 +10,7 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end)	\
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal)	\
 	"987: \n\t"						\
 	".pushsection .discard.unwind_hints\n\t"		\
 	/* struct unwind_hint */				\

@@ -19,7 +19,6 @@
 	".byte " __stringify(sp_reg) "\n\t"			\
 	".byte " __stringify(type) "\n\t"			\
 	".byte " __stringify(signal) "\n\t"			\
-	".byte " __stringify(end) "\n\t"			\
 	".balign 4 \n\t"					\
 	".popsection\n\t"
 

@@ -91,7 +90,7 @@
  * the debuginfo as necessary.  It will also warn if it sees any
  * inconsistencies.
  */
-.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
+.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
 .Lhere_\@:
 	.pushsection .discard.unwind_hints
 		/* struct unwind_hint */

@@ -100,7 +99,6 @@
 		.byte \sp_reg
 		.byte \type
 		.byte \signal
-		.byte \end
 		.balign 4
 	.popsection
 .endm

@@ -153,14 +151,14 @@
 
 #ifndef __ASSEMBLY__
 
-#define UNWIND_HINT(type, sp_reg, sp_offset, signal, end) "\n\t"
+#define UNWIND_HINT(type, sp_reg, sp_offset, signal) "\n\t"
 #define STACK_FRAME_NON_STANDARD(func)
 #define STACK_FRAME_NON_STANDARD_FP(func)
 #define ANNOTATE_NOENDBR
 #define ASM_REACHABLE
 #else
 #define ANNOTATE_INTRA_FUNCTION_CALL
-.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0 end=0
+.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
 .endm
 .macro STACK_FRAME_NON_STANDARD func:req
 .endm
include/linux/objtool_types.h +18 -9
index 9787ad0..453a4f4 100644
@@ -16,12 +16,18 @@ struct unwind_hint {
 	u8		sp_reg;
 	u8		type;
 	u8		signal;
-	u8		end;
 };
 
 #endif /* __ASSEMBLY__ */
 
 /*
+ * UNWIND_HINT_TYPE_UNDEFINED: A blind spot in ORC coverage which can result in
+ * a truncated and unreliable stack unwind.
+ *
+ * UNWIND_HINT_TYPE_END_OF_STACK: The end of the kernel stack unwind before
+ * hitting user entry, boot code, or fork entry (when there are no pt_regs
+ * available).
+ *
  * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
  * (the caller's SP right before it made the call).  Used for all callable
  * functions, i.e. all C code and all callable asm functions.

@@ -32,17 +38,20 @@ struct unwind_hint {
  * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
  * sp_reg+sp_offset points to the iret return frame.
  *
- * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
+ * UNWIND_HINT_TYPE_FUNC: Generate the unwind metadata of a callable function.
  * Useful for code which doesn't have an ELF function annotation.
  *
- * UNWIND_HINT_ENTRY: machine entry without stack, SYSCALL/SYSENTER etc.
+ * UNWIND_HINT_TYPE_{SAVE,RESTORE}: Save the unwind metadata at a certain
+ * location so that it can be restored later.
  */
-#define UNWIND_HINT_TYPE_CALL		0
-#define UNWIND_HINT_TYPE_REGS		1
-#define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+#define UNWIND_HINT_TYPE_UNDEFINED	0
+#define UNWIND_HINT_TYPE_END_OF_STACK	1
+#define UNWIND_HINT_TYPE_CALL		2
+#define UNWIND_HINT_TYPE_REGS		3
+#define UNWIND_HINT_TYPE_REGS_PARTIAL	4
 /* The below hint types don't have corresponding ORC types */
-#define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_SAVE		4
-#define UNWIND_HINT_TYPE_RESTORE	5
+#define UNWIND_HINT_TYPE_FUNC		5
+#define UNWIND_HINT_TYPE_SAVE		6
+#define UNWIND_HINT_TYPE_RESTORE	7
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
scripts/sorttable.h +1 -1
index deb7c1d..7bd0184 100644
@@ -128,7 +128,7 @@ static int orc_sort_cmp(const void *_a, const void *_b)
 	 * whitelisted .o files which didn't get objtool generation.
 	 */
 	orc_a = g_orc_table + (a - g_orc_ip_table);
-	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;
+	return orc_a->type == ORC_TYPE_UNDEFINED ? -1 : 1;
 }
 
 static void *sort_orctable(void *arg)
tools/arch/x86/include/asm/orc_types.h +7 -7
index b4d4ec7..46d7e06 100644
@@ -39,9 +39,11 @@
 #define ORC_REG_SP_INDIRECT		9
 #define ORC_REG_MAX			15
 
-#define ORC_TYPE_CALL			0
-#define ORC_TYPE_REGS			1
-#define ORC_TYPE_REGS_PARTIAL		2
+#define ORC_TYPE_UNDEFINED		0
+#define ORC_TYPE_END_OF_STACK		1
+#define ORC_TYPE_CALL			2
+#define ORC_TYPE_REGS			3
+#define ORC_TYPE_REGS_PARTIAL		4
 
 #ifndef __ASSEMBLY__
 #include <asm/byteorder.h>

@@ -60,16 +62,14 @@ struct orc_entry {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	unsigned	sp_reg:4;
 	unsigned	bp_reg:4;
-	unsigned	type:2;
+	unsigned	type:3;
 	unsigned	signal:1;
-	unsigned	end:1;
 #elif defined(__BIG_ENDIAN_BITFIELD)
 	unsigned	bp_reg:4;
 	unsigned	sp_reg:4;
 	unsigned	unused:4;
-	unsigned	end:1;
 	unsigned	signal:1;
-	unsigned	type:2;
+	unsigned	type:3;
 #endif
 } __packed;
tools/include/linux/objtool_types.h +18 -9
index 9787ad0..453a4f4 100644
@@ -16,12 +16,18 @@ struct unwind_hint {
 	u8		sp_reg;
 	u8		type;
 	u8		signal;
-	u8		end;
 };
 
 #endif /* __ASSEMBLY__ */
 
 /*
+ * UNWIND_HINT_TYPE_UNDEFINED: A blind spot in ORC coverage which can result in
+ * a truncated and unreliable stack unwind.
+ *
+ * UNWIND_HINT_TYPE_END_OF_STACK: The end of the kernel stack unwind before
+ * hitting user entry, boot code, or fork entry (when there are no pt_regs
+ * available).
+ *
  * UNWIND_HINT_TYPE_CALL: Indicates that sp_reg+sp_offset resolves to PREV_SP
  * (the caller's SP right before it made the call).  Used for all callable
  * functions, i.e. all C code and all callable asm functions.

@@ -32,17 +38,20 @@ struct unwind_hint {
  * UNWIND_HINT_TYPE_REGS_PARTIAL: Used in entry code to indicate that
  * sp_reg+sp_offset points to the iret return frame.
  *
- * UNWIND_HINT_FUNC: Generate the unwind metadata of a callable function.
+ * UNWIND_HINT_TYPE_FUNC: Generate the unwind metadata of a callable function.
  * Useful for code which doesn't have an ELF function annotation.
  *
- * UNWIND_HINT_ENTRY: machine entry without stack, SYSCALL/SYSENTER etc.
+ * UNWIND_HINT_TYPE_{SAVE,RESTORE}: Save the unwind metadata at a certain
+ * location so that it can be restored later.
  */
-#define UNWIND_HINT_TYPE_CALL		0
-#define UNWIND_HINT_TYPE_REGS		1
-#define UNWIND_HINT_TYPE_REGS_PARTIAL	2
+#define UNWIND_HINT_TYPE_UNDEFINED	0
+#define UNWIND_HINT_TYPE_END_OF_STACK	1
+#define UNWIND_HINT_TYPE_CALL		2
+#define UNWIND_HINT_TYPE_REGS		3
+#define UNWIND_HINT_TYPE_REGS_PARTIAL	4
 /* The below hint types don't have corresponding ORC types */
-#define UNWIND_HINT_TYPE_FUNC		3
-#define UNWIND_HINT_TYPE_SAVE		4
-#define UNWIND_HINT_TYPE_RESTORE	5
+#define UNWIND_HINT_TYPE_FUNC		5
+#define UNWIND_HINT_TYPE_SAVE		6
+#define UNWIND_HINT_TYPE_RESTORE	7
 
 #endif /* _LINUX_OBJTOOL_TYPES_H */
tools/objtool/check.c +1 -1
index 10be80b..cae6ac6 100644
@@ -2243,6 +2243,7 @@ static void set_func_state(struct cfi_state *state)
 	memcpy(&state->regs, &initial_func_cfi.regs,
 	       CFI_NUM_REGS * sizeof(struct cfi_reg));
 	state->stack_size = initial_func_cfi.cfa.offset;
+	state->type = UNWIND_HINT_TYPE_CALL;
 }
 
 static int read_unwind_hints(struct objtool_file *file)

@@ -2327,7 +2328,6 @@ static int read_unwind_hints(struct objtool_file *file)
 		cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
 		cfi.type = hint->type;
 		cfi.signal = hint->signal;
-		cfi.end = hint->end;
 
 		insn->cfi = cfi_hash_find_or_add(&cfi);
 	}
tools/objtool/orc_dump.c +6 -2
index 97ecbb8..0e183bb 100644
@@ -38,6 +38,10 @@ static const char *reg_name(unsigned int reg)
 static const char *orc_type_name(unsigned int type)
 {
 	switch (type) {
+	case ORC_TYPE_UNDEFINED:
+		return "(und)";
+	case ORC_TYPE_END_OF_STACK:
+		return "end";
 	case ORC_TYPE_CALL:
 		return "call";
 	case ORC_TYPE_REGS:

@@ -201,6 +205,7 @@ int orc_dump(const char *_objname)
 			printf("%llx:", (unsigned long long)(orc_ip_addr + (i * sizeof(int)) + orc_ip[i]));
 		}
 
+		printf("type:%s", orc_type_name(orc[i].type));
 
 		printf(" sp:");
 

@@ -210,8 +215,7 @@ int orc_dump(const char *_objname)
 
 		print_reg(orc[i].bp_reg, bswap_if_needed(&dummy_elf, orc[i].bp_offset));
 
-		printf(" type:%s signal:%d end:%d\n",
-		       orc_type_name(orc[i].type), orc[i].signal, orc[i].end);
+		printf(" signal:%d\n", orc[i].signal);
 	}
 
 	elf_end(elf);
tools/objtool/orc_gen.c +13 -13
index e85bbb9..b327f9c 100644
@@ -21,12 +21,22 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 	memset(orc, 0, sizeof(*orc));
 
 	if (!cfi) {
-		orc->end = 0;
-		orc->sp_reg = ORC_REG_UNDEFINED;
+		/*
+		 * This is usually either unreachable nops/traps (which don't
+		 * trigger unreachable instruction warnings), or
+		 * STACK_FRAME_NON_STANDARD functions.
+		 */
+		orc->type = ORC_TYPE_UNDEFINED;
 		return 0;
 	}
 
 	switch (cfi->type) {
+	case UNWIND_HINT_TYPE_UNDEFINED:
+		orc->type = ORC_TYPE_UNDEFINED;
+		return 0;
+	case UNWIND_HINT_TYPE_END_OF_STACK:
+		orc->type = ORC_TYPE_END_OF_STACK;
+		return 0;
 	case UNWIND_HINT_TYPE_CALL:
 		orc->type = ORC_TYPE_CALL;
 		break;

@@ -42,14 +52,8 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 		return -1;
 	}
 
-	orc->end = cfi->end;
 	orc->signal = cfi->signal;
 
-	if (cfi->cfa.base == CFI_UNDEFINED) {
-		orc->sp_reg = ORC_REG_UNDEFINED;
-		return 0;
-	}
-
 	switch (cfi->cfa.base) {
 	case CFI_SP:
 		orc->sp_reg = ORC_REG_SP;

@@ -163,11 +167,7 @@ int orc_create(struct objtool_file *file)
 	struct orc_list_entry *entry;
 	struct list_head orc_list;
 
-	struct orc_entry null = {
-		.sp_reg  = ORC_REG_UNDEFINED,
-		.bp_reg  = ORC_REG_UNDEFINED,
-		.type    = ORC_TYPE_CALL,
-	};
+	struct orc_entry null = { .type = ORC_TYPE_UNDEFINED };
 
 	/* Build a deduplicated list of ORC entries: */
 	INIT_LIST_HEAD(&orc_list);
maintainer Acked-by on the v1 series
#14 lore raw
In reply to Josh Poimboeuf
Quoted 11 lines · Josh Poimboeuf

Based on tip/objtool/core.

Mark reported that the ORC unwinder incorrectly marks an unwind as reliable when the unwind terminates prematurely in the dark corners of return_to_handler() due to lack of information about the next frame.

The problem is UNWIND_HINT_EMPTY is used in two different situations:
end-of-stack marker and undefined stack state.

Split it up into UNWIND_HINT_END_OF_STACK and UNWIND_HINT_UNDEFINED.

Quoted 7 lines

Josh Poimboeuf (6):
objtool: Add objtool_types.h
objtool: Use relative pointers for annotations
objtool: Change UNWIND_HINT() argument order x86,objtool: Introduce ORC_TYPE_*
x86,objtool: Separate unret validation from unwind hints x86,objtool: Split UNWIND_HINT_EMPTY in two

Quite a bit of churn, but the end result does seem cleaner.

Acked-by Peter Zijlstra (Intel) <[email protected]>