[PATCH 2/3] ARM: fix BUG() detection
Dave Martin
Dave.Martin at arm.com
Fri Aug 16 09:24:51 EDT 2013
On Fri, Aug 16, 2013 at 09:31:48AM +0100, Ben Dooks wrote:
> On 15/08/13 16:09, Dave Martin wrote:
> >On Wed, Aug 14, 2013 at 05:42:42PM +0100, Ben Dooks wrote:
> >>The detection of the instruction used by BUG() did not take into account
> >>the differences in endian-ness between instruction and data. Change the
> >>code to use the relevant helpers in<asm/opcodes.h> to translate the
> >>endian-ness of the instructions.
> >>
> >>Fixes issue reported by Dave Martin<Dave.Martin at arm.com>
> >
> >It probably makes sense to fold this with the preceding patch.
> >
> >>
> >>Signed-off-by: Ben Dooks<ben.dooks at codethink.co.uk>
> >>---
> >> arch/arm/include/asm/bug.h | 10 ++++++----
> >> arch/arm/kernel/traps.c | 8 +++++---
> >> 2 files changed, 11 insertions(+), 7 deletions(-)
> >>
> >>diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h
> >>index b95da52..b274bde 100644
> >>--- a/arch/arm/include/asm/bug.h
> >>+++ b/arch/arm/include/asm/bug.h
> >>@@ -2,6 +2,8 @@
> >> #define _ASMARM_BUG_H
> >>
> >> #include<linux/linkage.h>
> >>+#include<linux/types.h>
> >>+#include<asm/opcodes.h>
> >>
> >> #ifdef CONFIG_BUG
> >>
> >>@@ -12,10 +14,10 @@
> >> */
> >> #ifdef CONFIG_THUMB2_KERNEL
> >> #define BUG_INSTR_VALUE 0xde02
> >>-#define BUG_INSTR_TYPE ".inst.w "
> >>+#define BUG_INSTR(__value) __inst_thumb16(__value)
> >> #else
> >> #define BUG_INSTR_VALUE 0xe7f001f2
> >>-#define BUG_INSTR_TYPE ".inst "
> >>+#define BUG_INSTR(__value) __inst_arm(__value)
> >> #endif
> >
> >Looks OK. You could make things a bit less verbose by
> >
> > #define BUG_INSTR __inst_thumb16(BUG_INSTR_VALUE)
> >#else
> >...
> > #define BUG_INSTR __inst_arm(BUG_INSTR_VALUE)
>
> I was trying to keep the macro as similar as possible, although
> there is only one bug instruction value at the moment the __BUG()
> code seems to assume that in the future there may be more of them
> and that it should be able to handle them.
No problem, it should work fine your way.
Cheers
---Dave
>
> >>
> >>@@ -33,7 +35,7 @@
> >>
> >> #define __BUG(__file, __line, __value) \
> >> do { \
> >>- asm volatile("1:\t" BUG_INSTR_TYPE #__value "\n" \
> >>+ asm volatile("1:\t" BUG_INSTR(__value) "\n" \
> >> ".pushsection .rodata.str, \"aMS\", %progbits, 1\n" \
> >> "2:\t.asciz " #__file "\n" \
> >> ".popsection\n" \
> >>@@ -48,7 +50,7 @@ do { \
> >>
> >> #define __BUG(__file, __line, __value) \
> >> do { \
> >>- asm volatile(BUG_INSTR_TYPE #__value); \
> >>+ asm volatile(BUG_INSTR(__value) "\n"); \
> >> unreachable(); \
> >> } while (0)
> >> #endif /* CONFIG_DEBUG_BUGVERBOSE */
> >>diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
> >>index cb67b04..ae2d828 100644
> >>--- a/arch/arm/kernel/traps.c
> >>+++ b/arch/arm/kernel/traps.c
> >>@@ -344,15 +344,17 @@ void arm_notify_die(const char *str, struct pt_regs *regs,
> >> int is_valid_bugaddr(unsigned long pc)
> >> {
> >> #ifdef CONFIG_THUMB2_KERNEL
> >>- unsigned short bkpt;
> >>+ u16 bkpt;
> >>+ u16 insn = __opcode_to_mem_thumb16(BUG_INSTR_VALUE);
> >> #else
> >>- unsigned long bkpt;
> >>+ u32 bkpt;
> >>+ u32 insn = __opcode_to_mem_arm(BUG_INSTR_VALUE);
> >> #endif
> >>
> >> if (probe_kernel_address((unsigned *)pc, bkpt))
> >
> >Hmm, the (unsigned *) actually looks weird here now I look at it.
> >
> >probe_kernel_address does (__force typeof(bkpt) __user *) on it anyway,
> >so I guess that's harmless. void * might make more sense, though this
> >patch may not be the place to fix it.
> >
> >Cheers
> >---Dave
> >
> >> return 0;
> >>
> >>- return bkpt == BUG_INSTR_VALUE;
> >>+ return bkpt == insn;
> >> }
> >>
> >> #endif
> >>--
> >>1.7.10.4
> >>
> >>
> >>_______________________________________________
> >>linux-arm-kernel mailing list
> >>linux-arm-kernel at lists.infradead.org
> >>http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
>
> --
> Ben Dooks http://www.codethink.co.uk/
> Senior Engineer Codethink - Providing Genius
>
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