Commit b70842df authored by David Wilder's avatar David Wilder Committed by Heiko Carstens

[S390] kprobes: Align probe address.

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: default avatarDavid Wilder <dwilder@us.ibm.com>
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
parent afbc1e99
...@@ -167,7 +167,7 @@ static int __kprobes swap_instruction(void *aref) ...@@ -167,7 +167,7 @@ static int __kprobes swap_instruction(void *aref)
* shall not cross any page boundaries (vmalloc area!) when writing * shall not cross any page boundaries (vmalloc area!) when writing
* the new instruction. * the new instruction.
*/ */
addr = (u32 *)ALIGN((unsigned long)args->ptr, 4); addr = (u32 *)((unsigned long)args->ptr & -4UL);
if ((unsigned long)args->ptr & 2) if ((unsigned long)args->ptr & 2)
instr = ((*addr) & 0xffff0000) | args->new; instr = ((*addr) & 0xffff0000) | args->new;
else else
......
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