Messages in this thread Patch in this message | | | Date | Wed, 21 Mar 2007 18:09:10 -0700 | From | David Wilder <> | Subject | [patch] s390 kprobes: Align probe address |
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[This patch applies to both linux and mm trees. Please send comments off list, thanks] Running a probe on s390 with a probe address that is not 4 byte aligned results in a Kernel BUG. The problem is that the stura instruction used by swap_instruction requires the destination address to be 4 byte aligned. As stura only writes 4 bytes, aligning to the next 4 byte aligned address results in the breakpoint instruction being stored past the probe address. The fix is to align the address backward (to the previous 4 byte aligned address) and writing the two byte breakpoint instruction in the appropriate bytes.
Signed-off-by: David Wilder <dwilder@us.ibm.com> ------------------------ diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c index 8af549e..993f353 100644 --- a/arch/s390/kernel/kprobes.c +++ b/arch/s390/kernel/kprobes.c @@ -167,7 +167,7 @@ static int __kprobes swap_instruction(vo * shall not cross any page boundaries (vmalloc area!) when writing * the new instruction. */ - addr = (u32 *)ALIGN((unsigned long)args->ptr, 4); + addr = (u32 *)((unsigned long)args->ptr & -4UL); if ((unsigned long)args->ptr & 2) instr = ((*addr) & 0xffff0000) | args->new; else | |