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[S390] kprobes: Align probe address.

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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.

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David Wilder <dwilder@us.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
This commit is contained in:
David Wilder 2007-03-26 20:42:40 +02:00 committed by Heiko Carstens
parent afbc1e994d
commit b70842df77
1 changed files with 1 additions and 1 deletions
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2
arch/s390/kernel/kprobes.c
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@ -167,7 +167,7 @@ static int __kprobes swap_instruction(void *aref)
* 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