ARM: unwind: add unwind directives to bitops assembly macros

PATCH New Will Deacon 2 participants 2 messages Nov 21, 2011 Arm (32-bit)

Share & tools

Will Deacon

author

2011-11-21 10:23 UTC #0 lore raw

PATCH v2 1/1 ARM: unwind: add unwind directives to bitops assembly macros

The bitops functions (e.g. _test_and_set_bit) on ARM do not have unwind annotations and therefore the kernel cannot backtrace out of them on a fatal error (for example, NULL pointer dereference).

This patch annotates the bitops assembly macros with UNWIND annotations so that we can produce a meaningful backtrace on error. Callers of the macros are modified to pass their function name as a macro parameter, enforcing that the macros are used as standalone function implementations.

Cc Dave Martin <[email protected]>

Signed-off-by Will Deacon <[email protected]>

---

v2: Added function name argument to bitops macros, as suggested by Dave.

 arch/arm/lib/bitops.h        |   26 ++++++++++++++++++++++----
 arch/arm/lib/changebit.S     |    4 +---
 arch/arm/lib/clearbit.S      |    4 +---
 arch/arm/lib/setbit.S        |    4 +---
 arch/arm/lib/testchangebit.S |    4 +---
 arch/arm/lib/testclearbit.S  |    4 +---
 arch/arm/lib/testsetbit.S    |    4 +---
 7 files changed, 28 insertions(+), 22 deletions(-)

arch/arm/lib/bitops.h +22 -4

index 10d868a..d6408d1 100644
@@ -1,5 +1,9 @@
+#include <asm/unwind.h>
+
 #if __LINUX_ARM_ARCH__ >= 6
-	.macro	bitop, instr
+	.macro	bitop, name, instr
+ENTRY(	\name		)
+UNWIND(	.fnstart	)
 	ands	ip, r1, #3
 	strneb	r1, [ip]		@ assert word-aligned
 	mov	r2, #1

@@ -13,9 +17,13 @@
 	cmp	r0, #0
 	bne	1b
 	bx	lr
+UNWIND(	.fnend		)
+ENDPROC(\name		)
 	.endm
 
-	.macro	testop, instr, store
+	.macro	testop, name, instr, store
+ENTRY(	\name		)
+UNWIND(	.fnstart	)
 	ands	ip, r1, #3
 	strneb	r1, [ip]		@ assert word-aligned
 	mov	r2, #1

@@ -34,9 +42,13 @@
 	cmp	r0, #0
 	movne	r0, #1
 2:	bx	lr
+UNWIND(	.fnend		)
+ENDPROC(\name		)
 	.endm
 #else
-	.macro	bitop, instr
+	.macro	bitop, name, instr
+ENTRY(	\name		)
+UNWIND(	.fnstart	)
 	ands	ip, r1, #3
 	strneb	r1, [ip]		@ assert word-aligned
 	and	r2, r0, #31

@@ -49,6 +61,8 @@
 	str	r2, [r1, r0, lsl #2]
 	restore_irqs ip
 	mov	pc, lr
+UNWIND(	.fnend		)
+ENDPROC(\name		)
 	.endm
 
 /**

@@ -59,7 +73,9 @@
  * Note: we can trivially conditionalise the store instruction
  * to avoid dirtying the data cache.
  */
-	.macro	testop, instr, store
+	.macro	testop, name, instr, store
+ENTRY(	\name		)
+UNWIND(	.fnstart	)
 	ands	ip, r1, #3
 	strneb	r1, [ip]		@ assert word-aligned
 	and	r3, r0, #31

@@ -73,5 +89,7 @@
 	moveq	r0, #0
 	restore_irqs ip
 	mov	pc, lr
+UNWIND(	.fnend		)
+ENDPROC(\name		)
 	.endm
 #endif

arch/arm/lib/changebit.S +1 -3

index 68ed5b6..f402786 100644
@@ -12,6 +12,4 @@
 #include "bitops.h"
                 .text
 
-ENTRY(_change_bit)
-	bitop	eor
-ENDPROC(_change_bit)
+bitop	_change_bit, eor

arch/arm/lib/clearbit.S +1 -3

index 4c04c3b..f6b75fb 100644
@@ -12,6 +12,4 @@
 #include "bitops.h"
                 .text
 
-ENTRY(_clear_bit)
-	bitop	bic
-ENDPROC(_clear_bit)
+bitop	_clear_bit, bic

arch/arm/lib/setbit.S +1 -3

index bbee5c6..618feda 100644
@@ -12,6 +12,4 @@
 #include "bitops.h"
 		.text
 
-ENTRY(_set_bit)
-	bitop	orr
-ENDPROC(_set_bit)
+bitop	_set_bit, orr

arch/arm/lib/testchangebit.S +1 -3

index 15a4d43..4becdc3 100644
@@ -12,6 +12,4 @@
 #include "bitops.h"
                 .text
 
-ENTRY(_test_and_change_bit)
-	testop	eor, str
-ENDPROC(_test_and_change_bit)
+testop	_test_and_change_bit, eor, str

arch/arm/lib/testclearbit.S +1 -3

index 521b66b..918841d 100644
@@ -12,6 +12,4 @@
 #include "bitops.h"
                 .text
 
-ENTRY(_test_and_clear_bit)
-	testop	bicne, strne
-ENDPROC(_test_and_clear_bit)
+testop	_test_and_clear_bit, bicne, strne

arch/arm/lib/testsetbit.S +1 -3

index 1c98cc2..8d1b2fe 100644
@@ -12,6 +12,4 @@
 #include "bitops.h"
                 .text
 
-ENTRY(_test_and_set_bit)
-	testop	orreq, streq
-ENDPROC(_test_and_set_bit)
+testop	_test_and_set_bit, orreq, streq

Signature · 1 line

1.7.4.1

Dave Martin

2011-11-21 14:21 UTC #1 lore raw

PATCH v2 1/1 ARM: unwind: add unwind directives to bitops assembly macros

Quoted 11 lines · Will Deacon

The bitops functions (e.g. _test_and_set_bit) on ARM do not have unwind annotations and therefore the kernel cannot backtrace out of them on a fatal error (for example, NULL pointer dereference).
This patch annotates the bitops assembly macros with UNWIND annotations so that we can produce a meaningful backtrace on error. Callers of the macros are modified to pass their function name as a macro parameter, enforcing that the macros are used as standalone function implementations.
Cc Dave Martin <[email protected]>
Signed-off-by Will Deacon <[email protected]>

Acked-by Dave Martin <[email protected]>

It turns out that readelf -u prints out garbage for the unwind tables if you try to use it the resulting .o files... but that seems to be a bug in binutils, where some invalid assumptions are made about how to relocate the unwind information.

readelf -u vmlinux looks sensible though.

Cheers
---Dave

Quoted 161 lines

---