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arm64: kgdb: handle read-only text / modules

PATCH Superseded AKASHI Takahiro 2 participants 3 messages Sep 21, 2016 – Sep 23, 2016

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Stable branch arm64
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AKASHI Takahiro

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#0 lore raw

PATCH v2 1/1 arm64: kgdb: handle read-only text / modules

Handle read-only cases (CONFIG_DEBUG_RODATA/CONFIG_DEBUG_SET_MODULE_RONX) by using aarch64_insn_write() instead of probe_kernel_write(). See how this works:

    commit 2f896d586610 ("arm64: use fixmap for text patching")
Signed-off-by AKASHI Takahiro <[email protected]>
Cc Catalin Marinas <[email protected]>
Cc Will Deacon <[email protected]>
Cc Jason Wessel <[email protected]>
Cc <[email protected]> # 3.18-3.19: 2f896d5: arm64: use fixmap
Cc <[email protected]> # 4.0-
---
 arch/arm64/include/asm/debug-monitors.h |  2 --
 arch/arm64/kernel/kgdb.c                | 36 ++++++++++++++++++++++-----------
 2 files changed, 24 insertions(+), 14 deletions(-)
arch/arm64/include/asm/debug-monitors.h +0 -2
index 4b6b3f7..b71420a 100644
@@ -61,8 +61,6 @@
 
 #define AARCH64_BREAK_KGDB_DYN_DBG	\
 	(AARCH64_BREAK_MON | (KGDB_DYN_DBG_BRK_IMM << 5))
-#define KGDB_DYN_BRK_INS_BYTE(x)	\
-	((AARCH64_BREAK_KGDB_DYN_DBG >> (8 * (x))) & 0xff)
 
 #define CACHE_FLUSH_IS_SAFE		1
arch/arm64/kernel/kgdb.c +24 -12
index 6732a27..b06a7a2 100644
@@ -19,6 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/bug.h>
 #include <linux/cpumask.h>
 #include <linux/irq.h>
 #include <linux/irq_work.h>

@@ -26,6 +27,8 @@
 #include <linux/kgdb.h>
 #include <linux/kprobes.h>
 #include <linux/percpu.h>
+#include <asm/debug-monitors.h>
+#include <asm/insn.h>
 #include <asm/ptrace.h>
 #include <asm/traps.h>
 

@@ -370,15 +373,24 @@ void kgdb_arch_exit(void)
 	unregister_die_notifier(&kgdb_notifier);
 }
 
-/*
- * ARM instructions are always in LE.
- * Break instruction is encoded in LE format
- */
-struct kgdb_arch arch_kgdb_ops = {
-	.gdb_bpt_instr = {
-		KGDB_DYN_BRK_INS_BYTE(0),
-		KGDB_DYN_BRK_INS_BYTE(1),
-		KGDB_DYN_BRK_INS_BYTE(2),
-		KGDB_DYN_BRK_INS_BYTE(3),
-	}
-};
+struct kgdb_arch arch_kgdb_ops;
+
+int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
+{
+	int err;
+
+	BUILD_BUG_ON(AARCH64_INSN_SIZE != BREAK_INSTR_SIZE);
+
+	err = aarch64_insn_read((void *)bpt->bpt_addr, (u32 *)bpt->saved_instr);
+	if (err)
+		return err;
+
+	return aarch64_insn_write((void *)bpt->bpt_addr,
+			(u32)AARCH64_BREAK_KGDB_DYN_DBG);
+}
+
+int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
+{
+	return aarch64_insn_write((void *)bpt->bpt_addr,
+			*(u32 *)bpt->saved_instr);
+}
Signature · 1 line
2.10.0
reviewer
#1 lore raw

PATCH v2 1/1 arm64: kgdb: handle read-only text / modules

Quoted 11 lines · AKASHI Takahiro

Handle read-only cases (CONFIG_DEBUG_RODATA/CONFIG_DEBUG_SET_MODULE_RONX) by using aarch64_insn_write() instead of probe_kernel_write(). See how this works:

    commit 2f896d586610 ("arm64: use fixmap for text patching")
Signed-off-by AKASHI Takahiro <[email protected]>
Cc Catalin Marinas <[email protected]>
Cc Will Deacon <[email protected]>
Cc Jason Wessel <[email protected]>
Cc <[email protected]> # 3.18-3.19: 2f896d5: arm64: use fixmap
Cc <[email protected]> # 4.0-

For v3.18-v3.19, we also need commit f6242cac10427c54 ("arm64: Fix text patching logic when using fixmap"), so as to not break the !CONFIG_DEBUG_SET_MODULE_RONX case.

With that:

Reviewed-by Mark Rutland <[email protected]>

Thanks,
Mark.

Quoted 79 lines
---
 arch/arm64/include/asm/debug-monitors.h |  2 --
 arch/arm64/kernel/kgdb.c                | 36 ++++++++++++++++++++++-----------
 2 files changed, 24 insertions(+), 14 deletions(-)
arch/arm64/include/asm/debug-monitors.h +0 -2
index 4b6b3f7..b71420a 100644
@@ -61,8 +61,6 @@
 
 #define AARCH64_BREAK_KGDB_DYN_DBG	\
 	(AARCH64_BREAK_MON | (KGDB_DYN_DBG_BRK_IMM << 5))
-#define KGDB_DYN_BRK_INS_BYTE(x)	\
-	((AARCH64_BREAK_KGDB_DYN_DBG >> (8 * (x))) & 0xff)
 
 #define CACHE_FLUSH_IS_SAFE		1
arch/arm64/kernel/kgdb.c +24 -12
index 6732a27..b06a7a2 100644
@@ -19,6 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/bug.h>
 #include <linux/cpumask.h>
 #include <linux/irq.h>
 #include <linux/irq_work.h>

@@ -26,6 +27,8 @@
 #include <linux/kgdb.h>
 #include <linux/kprobes.h>
 #include <linux/percpu.h>
+#include <asm/debug-monitors.h>
+#include <asm/insn.h>
 #include <asm/ptrace.h>
 #include <asm/traps.h>
 

@@ -370,15 +373,24 @@ void kgdb_arch_exit(void)
 	unregister_die_notifier(&kgdb_notifier);
 }
 
-/*
- * ARM instructions are always in LE.
- * Break instruction is encoded in LE format
- */
-struct kgdb_arch arch_kgdb_ops = {
-	.gdb_bpt_instr = {
-		KGDB_DYN_BRK_INS_BYTE(0),
-		KGDB_DYN_BRK_INS_BYTE(1),
-		KGDB_DYN_BRK_INS_BYTE(2),
-		KGDB_DYN_BRK_INS_BYTE(3),
-	}
-};
+struct kgdb_arch arch_kgdb_ops;
+
+int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
+{
+	int err;
+
+	BUILD_BUG_ON(AARCH64_INSN_SIZE != BREAK_INSTR_SIZE);
+
+	err = aarch64_insn_read((void *)bpt->bpt_addr, (u32 *)bpt->saved_instr);
+	if (err)
+		return err;
+
+	return aarch64_insn_write((void *)bpt->bpt_addr,
+			(u32)AARCH64_BREAK_KGDB_DYN_DBG);
+}
+
+int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
+{
+	return aarch64_insn_write((void *)bpt->bpt_addr,
+			*(u32 *)bpt->saved_instr);
+}
Signature · 1 line
2.10.0
author
#2 lore raw

PATCH v2 1/1 arm64: kgdb: handle read-only text / modules

Quoted 13 lines · Mark Rutland
Quoted 11 lines · AKASHI Takahiro

Handle read-only cases (CONFIG_DEBUG_RODATA/CONFIG_DEBUG_SET_MODULE_RONX) by using aarch64_insn_write() instead of probe_kernel_write(). See how this works:

    commit 2f896d586610 ("arm64: use fixmap for text patching")
Signed-off-by AKASHI Takahiro <[email protected]>
Cc Catalin Marinas <[email protected]>
Cc Will Deacon <[email protected]>
Cc Jason Wessel <[email protected]>
Cc <[email protected]> # 3.18-3.19: 2f896d5: arm64: use fixmap
Cc <[email protected]> # 4.0-
Quoted 3 lines

For v3.18-v3.19, we also need commit f6242cac10427c54 ("arm64: Fix text patching logic when using fixmap"), so as to not break the !CONFIG_DEBUG_SET_MODULE_RONX case.

Ah, thank you.
I will post the patch as v2.1.

-Takahiro AKASHI

Quoted 86 lines

With that:

Reviewed-by Mark Rutland <[email protected]>

Thanks,
Mark.

Quoted 79 lines
---
 arch/arm64/include/asm/debug-monitors.h |  2 --
 arch/arm64/kernel/kgdb.c                | 36 ++++++++++++++++++++++-----------
 2 files changed, 24 insertions(+), 14 deletions(-)
arch/arm64/include/asm/debug-monitors.h +0 -2
index 4b6b3f7..b71420a 100644
@@ -61,8 +61,6 @@
 
 #define AARCH64_BREAK_KGDB_DYN_DBG	\
 	(AARCH64_BREAK_MON | (KGDB_DYN_DBG_BRK_IMM << 5))
-#define KGDB_DYN_BRK_INS_BYTE(x)	\
-	((AARCH64_BREAK_KGDB_DYN_DBG >> (8 * (x))) & 0xff)
 
 #define CACHE_FLUSH_IS_SAFE		1
arch/arm64/kernel/kgdb.c +24 -12
index 6732a27..b06a7a2 100644
@@ -19,6 +19,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/bug.h>
 #include <linux/cpumask.h>
 #include <linux/irq.h>
 #include <linux/irq_work.h>

@@ -26,6 +27,8 @@
 #include <linux/kgdb.h>
 #include <linux/kprobes.h>
 #include <linux/percpu.h>
+#include <asm/debug-monitors.h>
+#include <asm/insn.h>
 #include <asm/ptrace.h>
 #include <asm/traps.h>
 

@@ -370,15 +373,24 @@ void kgdb_arch_exit(void)
 	unregister_die_notifier(&kgdb_notifier);
 }
 
-/*
- * ARM instructions are always in LE.
- * Break instruction is encoded in LE format
- */
-struct kgdb_arch arch_kgdb_ops = {
-	.gdb_bpt_instr = {
-		KGDB_DYN_BRK_INS_BYTE(0),
-		KGDB_DYN_BRK_INS_BYTE(1),
-		KGDB_DYN_BRK_INS_BYTE(2),
-		KGDB_DYN_BRK_INS_BYTE(3),
-	}
-};
+struct kgdb_arch arch_kgdb_ops;
+
+int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
+{
+	int err;
+
+	BUILD_BUG_ON(AARCH64_INSN_SIZE != BREAK_INSTR_SIZE);
+
+	err = aarch64_insn_read((void *)bpt->bpt_addr, (u32 *)bpt->saved_instr);
+	if (err)
+		return err;
+
+	return aarch64_insn_write((void *)bpt->bpt_addr,
+			(u32)AARCH64_BREAK_KGDB_DYN_DBG);
+}
+
+int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
+{
+	return aarch64_insn_write((void *)bpt->bpt_addr,
+			*(u32 *)bpt->saved_instr);
+}
Signature · 1 line
2.10.0