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powerpc: link error on orphan sections

PATCH In review Nicholas Piggin 4 participants 9 messages Oct 12, 2016 – Oct 19, 2016

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PowerPC Generic include/asm header files
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Nicholas Piggin

author reviewer
#0 lore raw

PATCH 1/1 powerpc: link error on orphan sections

Add --orphan-handling=error to final link flags. This ensures we have to handle all sections. This would have caught subtle breakage such as 7de3b27bac47da9de08409df1d69664acbb72197 at build-time.

Also bring some wayward sections into the fold:
- .text.hot and .text.unlikely are compiler generated sections.
- .sfpr is a linker generated section for register save functions.
- .sdata2, .dynsbss, .plt are used by PPC32
- We previously did not specify DWARF_DEBUG or STABS_DEBUG
- DWARF_DEBUG did not include DWARF3 .debug_ranges
- A number of sections are unused.

I don't know if I've exactly got everything right here, particularly with ppc32, so would appreciate people casting their eye over it.

Signed-off-by Nicholas Piggin <[email protected]>
---
 arch/powerpc/Makefile             |  2 +-
 arch/powerpc/kernel/vmlinux.lds.S | 16 ++++++++++++++--
 include/asm-generic/vmlinux.lds.h |  3 +++
 3 files changed, 18 insertions(+), 3 deletions(-)
arch/powerpc/Makefile +1 -1
index 50d020a..a3f2784 100644
@@ -90,7 +90,7 @@ endif
 
 LDFLAGS_vmlinux-y := -Bstatic
 LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
-LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y)
+LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y) --orphan-handling=error
 
 ifeq ($(CONFIG_PPC64),y)
 ifeq ($(call cc-option-yn,-mcmodel=medium),y)
arch/powerpc/kernel/vmlinux.lds.S +14 -2
index 8295f51..9f4d85e 100644
@@ -97,7 +97,7 @@ SECTIONS
 	.text : AT(ADDR(.text) - LOAD_OFFSET) {
 		ALIGN_FUNCTION();
 		/* careful! __ftr_alt_* sections need to be close to .text */
-		*(.text .fixup __ftr_alt_* .ref.text)
+		*(.text.hot .text .text.fixup .text.unlikely .fixup __ftr_alt_* .ref.text .sfpr) \
 		SCHED_TEXT
 		CPUIDLE_TEXT
 		LOCK_TEXT

@@ -256,7 +256,9 @@ SECTIONS
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {
 		DATA_DATA
 		*(.sdata)
+		*(.sdata2)
 		*(.got.plt) *(.got)
+		*(.plt)
 	}
 #else
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {

@@ -317,6 +319,16 @@ SECTIONS
 	_end = . ;
 	PROVIDE32 (end = .);
 
-	/* Sections to be discarded. */
+	STABS_DEBUG
+
+	DWARF_DEBUG
+
 	DISCARDS
+	/DISCARD/ : {
+		*(*.EMB.apuinfo)
+		*(.glink .iplt .plt .rela* .comment)
+		*(.gnu.version*)
+		*(.gnu.attributes)
+		*(.eh_frame)
+	}
 }
include/asm-generic/vmlinux.lds.h +3 -0
index 3e42bcd..264ebb3 100644
@@ -581,6 +581,7 @@
 #define SBSS(sbss_align)						\
 	. = ALIGN(sbss_align);						\
 	.sbss : AT(ADDR(.sbss) - LOAD_OFFSET) {				\
+		*(.dynsbss)						\
 		*(.sbss)						\
 		*(.scommon)						\
 	}

@@ -627,6 +628,8 @@
 		.debug_str      0 : { *(.debug_str) }			\
 		.debug_loc      0 : { *(.debug_loc) }			\
 		.debug_macinfo  0 : { *(.debug_macinfo) }		\
+		/* DWARF 3 */						\
+		.debug_ranges	0 : { *(.debug_ranges) }		\
 		/* SGI/MIPS DWARF 2 extensions */			\
 		.debug_weaknames 0 : { *(.debug_weaknames) }		\
 		.debug_funcnames 0 : { *(.debug_funcnames) }		\
Signature · 1 line
2.9.3
reviewer
#1 lore raw
Quoted 27 lines · Nicholas Piggin

Add --orphan-handling=error to final link flags. This ensures we have to handle all sections. This would have caught subtle breakage such as 7de3b27bac47da9de08409df1d69664acbb72197 at build-time.

Also bring some wayward sections into the fold:
- .text.hot and .text.unlikely are compiler generated sections.
- .sfpr is a linker generated section for register save functions.
- .sdata2, .dynsbss, .plt are used by PPC32
- We previously did not specify DWARF_DEBUG or STABS_DEBUG
- DWARF_DEBUG did not include DWARF3 .debug_ranges
- A number of sections are unused.

I don't know if I've exactly got everything right here, particularly with ppc32, so would appreciate people casting their eye over it.

Signed-off-by Nicholas Piggin <[email protected]>
---
 arch/powerpc/Makefile             |  2 +-
 arch/powerpc/kernel/vmlinux.lds.S | 16 ++++++++++++++--
 include/asm-generic/vmlinux.lds.h |  3 +++
 3 files changed, 18 insertions(+), 3 deletions(-)
arch/powerpc/Makefile +0 -0
index 50d020a..a3f2784 100644

arch/powerpc/Makefile endif · line 93

Quoted 5 lines
arch/powerpc/Makefile +1 -1
@@ -90,7 +90,7 @@ endif
 
 LDFLAGS_vmlinux-y := -Bstatic
 LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
-LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y)
+LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y) --orphan-handling=error

At least some old(er) toolchains don't support that:

/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-ld: unrecognized option '--orphan-handling=error'

So we'll need an ld-option wrapper around it.

cheers

#2 lore raw

From: Michael Ellerman

Quoted 1 line

Sent: 14 October 2016 01:46

...

Quoted 5 lines
Quoted 1 line

+LDFLAGS_vmlinux :=3D $(LDFLAGS_vmlinux-y) --orphan-handling=3Derror

=20
At least some old(er) toolchains don't support that:
=20
/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-ld: =

unrecognized option '--

Quoted 3 lines

orphan-handling=3Derror'
=20
So we'll need an ld-option wrapper around it.

In the past I've caused orphan sections to error by assigning them to the same address as something that exists.
Works with all linkers, even if the error message isn't as useful.

David

reviewer
#3 lore raw
Quoted 7 lines · David Laight

From: Michael Ellerman

Quoted 1 line

Sent: 14 October 2016 01:46

...

Quoted 4 lines
Quoted 1 line

+LDFLAGS_vmlinux := $(LDFLAGS_vmlinux-y) --orphan-handling=error

At least some old(er) toolchains don't support that:

Quoted 8 lines
Quoted 4 lines

/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-ld: unrecognized option '--
orphan-handling=error'

So we'll need an ld-option wrapper around it.

In the past I've caused orphan sections to error by assigning them to the same address as something that exists.
Works with all linkers, even if the error message isn't as useful.

How do you assign them an address without knowing what they are? With a wild card rule?

Anyway I think I'm happy for this to only work on newer toolchains.

cheers

#4 lore raw

From: Michael Ellerman [mailto:[email protected]]

Quoted 6 lines
Quoted 3 lines

In the past I've caused orphan sections to error by assigning them to the same address as something that exists.
Works with all linkers, even if the error message isn't as useful.

=20
How do you assign them an address without knowing what they are? With a wild card rule?

Right at the end of the ldscript I have:

    /* Anything from any unexpected section ends up here and
     * generates an error because this overlaps another section */
    unwanted _gp : { *(*) }
}

David

#5 lore raw
In reply to Nicholas Piggin
Quoted 40 lines · Nicholas Piggin

Add --orphan-handling=error to final link flags. This ensures we have to handle all sections. This would have caught subtle breakage such as 7de3b27bac47da9de08409df1d69664acbb72197 at build-time.

Also bring some wayward sections into the fold:
- .text.hot and .text.unlikely are compiler generated sections.
- .sfpr is a linker generated section for register save functions.
- .sdata2, .dynsbss, .plt are used by PPC32
- We previously did not specify DWARF_DEBUG or STABS_DEBUG
- DWARF_DEBUG did not include DWARF3 .debug_ranges
- A number of sections are unused.

I don't know if I've exactly got everything right here, particularly with ppc32, so would appreciate people casting their eye over it.

Signed-off-by Nicholas Piggin <[email protected]>
---
 arch/powerpc/Makefile             |  2 +-
 arch/powerpc/kernel/vmlinux.lds.S | 16 ++++++++++++++--
 include/asm-generic/vmlinux.lds.h |  3 +++
 3 files changed, 18 insertions(+), 3 deletions(-)
arch/powerpc/Makefile +1 -1
index 50d020a..a3f2784 100644
@@ -90,7 +90,7 @@ endif
 
 LDFLAGS_vmlinux-y := -Bstatic
 LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
-LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y)
+LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y) --orphan-handling=error
 
 ifeq ($(CONFIG_PPC64),y)
 ifeq ($(call cc-option-yn,-mcmodel=medium),y)
arch/powerpc/kernel/vmlinux.lds.S +0 -0
index 8295f51..9f4d85e 100644

arch/powerpc/kernel/vmlinux.lds.S SECTIONS · line 101

Quoted 6 lines
arch/powerpc/kernel/vmlinux.lds.S +1 -1
@@ -97,7 +97,7 @@ SECTIONS
 	.text : AT(ADDR(.text) - LOAD_OFFSET) {
 		ALIGN_FUNCTION();
 		/* careful! __ftr_alt_* sections need to be close to .text */
-		*(.text .fixup __ftr_alt_* .ref.text)
+		*(.text.hot .text .text.fixup .text.unlikely .fixup __ftr_alt_* .ref.text .sfpr) \
 		SCHED_TEXT

Is the "\" to pack the sched_text with the rest of .text?

Quoted 13 lines
arch/powerpc/kernel/vmlinux.lds.S +2 -0
 		CPUIDLE_TEXT
 		LOCK_TEXT

@@ -256,7 +256,9 @@ SECTIONS
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {
 		DATA_DATA
 		*(.sdata)
+		*(.sdata2)
 		*(.got.plt) *(.got)
+		*(.plt)
 	}
 #else
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {

arch/powerpc/kernel/vmlinux.lds.S SECTIONS · line 325

Quoted 8 lines
arch/powerpc/kernel/vmlinux.lds.S +4 -1
@@ -317,6 +319,16 @@ SECTIONS
 	_end = . ;
 	PROVIDE32 (end = .);
 
-	/* Sections to be discarded. */
+	STABS_DEBUG
+
+	DWARF_DEBUG
+

Are the debug sections discarded or is the above comment misplaced? I guess they are discarded because of them being outside of _end at relocation.

Quoted 25 lines
arch/powerpc/kernel/vmlinux.lds.S +7 -0
 	DISCARDS
+	/DISCARD/ : {
+		*(*.EMB.apuinfo)
+		*(.glink .iplt .plt .rela* .comment)
+		*(.gnu.version*)
+		*(.gnu.attributes)
+		*(.eh_frame)
+	}
 }
include/asm-generic/vmlinux.lds.h +1 -0
index 3e42bcd..264ebb3 100644
@@ -581,6 +581,7 @@
 #define SBSS(sbss_align)						\
 	. = ALIGN(sbss_align);						\
 	.sbss : AT(ADDR(.sbss) - LOAD_OFFSET) {				\
+		*(.dynsbss)						\
 		*(.sbss)						\
 		*(.scommon)						\
 	}

include/asm-generic/vmlinux.lds.h line 635

Quoted 8 lines
include/asm-generic/vmlinux.lds.h +2 -0
@@ -627,6 +628,8 @@
 		.debug_str      0 : { *(.debug_str) }			\
 		.debug_loc      0 : { *(.debug_loc) }			\
 		.debug_macinfo  0 : { *(.debug_macinfo) }		\
+		/* DWARF 3 */						\
+		.debug_ranges	0 : { *(.debug_ranges) }		\
 		/* SGI/MIPS DWARF 2 extensions */			\
 		.debug_weaknames 0 : { *(.debug_weaknames) }		\
 		.debug_funcnames 0 : { *(.debug_funcnames) }		\

Balbir Singh.

author reviewer
#6 lore raw
Quoted 34 lines · On Fri, 14 Oct 2016 13:35:54 +1100 Balbir Singh <[email protected]> wrote:
Quoted 33 lines · Nicholas Piggin

Add --orphan-handling=error to final link flags. This ensures we have to handle all sections. This would have caught subtle breakage such as 7de3b27bac47da9de08409df1d69664acbb72197 at build-time.

Also bring some wayward sections into the fold:
- .text.hot and .text.unlikely are compiler generated sections.
- .sfpr is a linker generated section for register save functions.
- .sdata2, .dynsbss, .plt are used by PPC32
- We previously did not specify DWARF_DEBUG or STABS_DEBUG
- DWARF_DEBUG did not include DWARF3 .debug_ranges
- A number of sections are unused.

I don't know if I've exactly got everything right here, particularly with ppc32, so would appreciate people casting their eye over it.

Signed-off-by Nicholas Piggin <[email protected]>
---
 arch/powerpc/Makefile             |  2 +-
 arch/powerpc/kernel/vmlinux.lds.S | 16 ++++++++++++++--
 include/asm-generic/vmlinux.lds.h |  3 +++
 3 files changed, 18 insertions(+), 3 deletions(-)
arch/powerpc/Makefile +1 -1
index 50d020a..a3f2784 100644
@@ -90,7 +90,7 @@ endif
 
 LDFLAGS_vmlinux-y := -Bstatic
 LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
-LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y)
+LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y) --orphan-handling=error
Quoted 15 lines

arch/powerpc/kernel/vmlinux.lds.S SECTIONS · line 101

Quoted 13 lines
arch/powerpc/Makefile +0 -0
 ifeq ($(CONFIG_PPC64),y)
 ifeq ($(call cc-option-yn,-mcmodel=medium),y)
arch/powerpc/kernel/vmlinux.lds.S +1 -1
index 8295f51..9f4d85e 100644
@@ -97,7 +97,7 @@ SECTIONS
 	.text : AT(ADDR(.text) - LOAD_OFFSET) {
 		ALIGN_FUNCTION();
 		/* careful! __ftr_alt_* sections need to be close to .text */
-		*(.text .fixup __ftr_alt_* .ref.text)
+		*(.text.hot .text .text.fixup .text.unlikely .fixup __ftr_alt_* .ref.text .sfpr) \
 		SCHED_TEXT

Is the "\" to pack the sched_text with the rest of .text?

Actually it looks like a typo that slipped in. Good catch.

Quoted 14 lines
Quoted 14 lines
arch/powerpc/kernel/vmlinux.lds.S +2 -0
@@ -256,7 +256,9 @@ SECTIONS
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {
 		DATA_DATA
 		*(.sdata)
+		*(.sdata2)
 		*(.got.plt) *(.got)
+		*(.plt)
 	}
 #else
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {

@@ -317,6 +319,16 @@ SECTIONS
 	_end = . ;
 	PROVIDE32 (end = .);
Quoted 9 lines

arch/powerpc/kernel/vmlinux.lds.S SECTIONS · line 325

Quoted 5 lines
arch/powerpc/kernel/vmlinux.lds.S +4 -1
-	/* Sections to be discarded. */
+	STABS_DEBUG
+
+	DWARF_DEBUG
+

Are the debug sections discarded or is the above comment misplaced? I guess they are discarded because of them being outside of _end at relocation.

I just got rid of the comment. Having it right above "DISCARDS" seemed redundant.

I believe the debug sections will be linked into the file, because they were not put in the /DISCARD/ output. But they will be outside the _end symbol.

Thanks,
Nick

reviewer
#7 lore raw
In reply to Nicholas Piggin

arch/powerpc/kernel/vmlinux.lds.S SECTIONS · line 324

Quoted 12 lines · Nicholas Piggin
arch/powerpc/kernel/vmlinux.lds.S +3 -1
index 8295f51..9f4d85e 100644
@@ -317,6 +319,16 @@ SECTIONS
 	_end = . ;
 	PROVIDE32 (end = .);
 
-	/* Sections to be discarded. */
+	STABS_DEBUG
+
+	DWARF_DEBUG

With DEBUG_INFO=y I'm seeing:

/opt/toolchains/6/powerpc/bin/ld: error: unplaced orphan section .debug_addr' from arch/powerpc/kernel/prom_init.o'. /opt/toolchains/6/powerpc/bin/ld: error: unplaced orphan section .debug_gnu_pubnames' from arch/powerpc/kernel/prom_init.o'. /opt/toolchains/6/powerpc/bin/ld: error: unplaced orphan section .debug_gnu_pubtypes' from arch/powerpc/kernel/prom_init.o'.

And many more for the same sections from other files.

cheers

author reviewer
#8 lore raw

Cc Alan Modra

Quoted 7 lines · On Fri, 14 Oct 2016 14:27:45 +1100 Michael Ellerman <[email protected]> wrote:

With DEBUG_INFO=y I'm seeing:

/opt/toolchains/6/powerpc/bin/ld: error: unplaced orphan section .debug_addr' from arch/powerpc/kernel/prom_init.o'. /opt/toolchains/6/powerpc/bin/ld: error: unplaced orphan section .debug_gnu_pubnames' from arch/powerpc/kernel/prom_init.o'. /opt/toolchains/6/powerpc/bin/ld: error: unplaced orphan section .debug_gnu_pubtypes' from arch/powerpc/kernel/prom_init.o'.

And many more for the same sections from other files.

How's this? Might take a few iterations to smooth out all toolchains

From: Nicholas Piggin <[email protected]>
Date: Thu, 22 Sep 2016 18:41:14 +1000
Subject: [PATCH] powerpc: link error on orphan sections

Add --orphan-handling=error to final link flags. This ensures we have to handle all sections. This would have caught subtle breakage such as 7de3b27bac47da9de08409df1d69664acbb72197 at build-time.

Also bring some wayward sections into the fold:
- .text.hot and .text.unlikely are compiler generated sections.
- .sfpr is a linker generated section for register save functions.
- .sdata2, .dynsbss, .plt are used by PPC32
- We previously did not specify DWARF_DEBUG or STABS_DEBUG
- DWARF_DEBUG did not include DWARF3 .debug_ranges
- A number of sections are unused.

I don't know if I've exactly got everything right here, particularly with ppc32, so would appreciate people casting their eye over it.

Signed-off-by Nicholas Piggin <[email protected]>
---
 arch/powerpc/Makefile             |  1 +
 arch/powerpc/kernel/vmlinux.lds.S | 16 ++++++++++++++--
 include/asm-generic/vmlinux.lds.h | 11 +++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)
arch/powerpc/Makefile +1 -0
index 50d020a..6883fca 100644
@@ -91,6 +91,7 @@ endif
 LDFLAGS_vmlinux-y := -Bstatic
 LDFLAGS_vmlinux-$(CONFIG_RELOCATABLE) := -pie
 LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-y)
+LDFLAGS_vmlinux += $(call ld-option,--orphan-handling=error)
 
 ifeq ($(CONFIG_PPC64),y)
 ifeq ($(call cc-option-yn,-mcmodel=medium),y)
arch/powerpc/kernel/vmlinux.lds.S +14 -2
index 8295f51..9f4d85e 100644
@@ -97,7 +97,7 @@ SECTIONS
 	.text : AT(ADDR(.text) - LOAD_OFFSET) {
 		ALIGN_FUNCTION();
 		/* careful! __ftr_alt_* sections need to be close to .text */
-		*(.text .fixup __ftr_alt_* .ref.text)
+		*(.text.hot .text .text.fixup .text.unlikely .fixup __ftr_alt_* .ref.text .sfpr) \
 		SCHED_TEXT
 		CPUIDLE_TEXT
 		LOCK_TEXT

@@ -256,7 +256,9 @@ SECTIONS
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {
 		DATA_DATA
 		*(.sdata)
+		*(.sdata2)
 		*(.got.plt) *(.got)
+		*(.plt)
 	}
 #else
 	.data : AT(ADDR(.data) - LOAD_OFFSET) {

@@ -317,6 +319,16 @@ SECTIONS
 	_end = . ;
 	PROVIDE32 (end = .);
 
-	/* Sections to be discarded. */
+	STABS_DEBUG
+
+	DWARF_DEBUG
+
 	DISCARDS
+	/DISCARD/ : {
+		*(*.EMB.apuinfo)
+		*(.glink .iplt .plt .rela* .comment)
+		*(.gnu.version*)
+		*(.gnu.attributes)
+		*(.eh_frame)
+	}
 }
include/asm-generic/vmlinux.lds.h +11 -0
index 3e42bcd..2f825de 100644
@@ -581,6 +581,7 @@
 #define SBSS(sbss_align)						\
 	. = ALIGN(sbss_align);						\
 	.sbss : AT(ADDR(.sbss) - LOAD_OFFSET) {				\
+		*(.dynsbss)						\
 		*(.sbss)						\
 		*(.scommon)						\
 	}

@@ -627,11 +628,21 @@
 		.debug_str      0 : { *(.debug_str) }			\
 		.debug_loc      0 : { *(.debug_loc) }			\
 		.debug_macinfo  0 : { *(.debug_macinfo) }		\
+		.debug_pubtypes 0 : { *(.debug_pubtypes) }		\
+		/* DWARF 3 */						\
+		.debug_ranges	0 : { *(.debug_ranges) }		\
 		/* SGI/MIPS DWARF 2 extensions */			\
 		.debug_weaknames 0 : { *(.debug_weaknames) }		\
 		.debug_funcnames 0 : { *(.debug_funcnames) }		\
 		.debug_typenames 0 : { *(.debug_typenames) }		\
 		.debug_varnames  0 : { *(.debug_varnames) }		\
+		/* GNU DWARF 2 extensions */				\
+		.debug_gnu_pubnames 0 : { *(.debug_gnu_pubnames) }	\
+		.debug_gnu_pubtypes 0 : { *(.debug_gnu_pubtypes) }	\
+		/* DWARF 4 */						\
+		.debug_types	0 : { *(.debug_types) }			\
+		/* DWARF 5 */						\
+		.debug_addr	0 : { *(.debug_addr) }
 
 		/* Stabs debugging sections.  */
 #define STABS_DEBUG							\
Signature · 1 line
2.9.3