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uprobes/x86: Only rep+nop can be emulated correctly 

__skip_sstep() correctly detects the "nontrivial" nop insns,
but since it doesn't update regs->ip we can not really skip
"0x0f 0x1f | 0x0f 0x19 | 0x87 0xc0", the probed application
is killed by SIGILL'ed handle_swbp().

Remove these additional checks. If we want to implement this
correctly we need to know the full insn length to update ->ip.

rep* + nop is fine even without updating ->ip.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2012-09-29 21:31:08 +02:00
parent ec75fba93e
commit b64b9c937a
1 changed files with 2 additions and 14 deletions
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16
arch/x86/kernel/uprobes.c
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@ -651,31 +651,19 @@ void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
/*
* Skip these instructions as per the currently known x86 ISA.
* 0x66* { 0x90 | 0x0f 0x1f | 0x0f 0x19 | 0x87 0xc0 }
* rep=0x66*; nop=0x90
*/
static bool __skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
int i;
for (i = 0; i < MAX_UINSN_BYTES; i++) {
if ((auprobe->insn[i] == 0x66))
if (auprobe->insn[i] == 0x66)
continue;
if (auprobe->insn[i] == 0x90)
return true;
if (i == (MAX_UINSN_BYTES - 1))
break;
if ((auprobe->insn[i] == 0x0f) && (auprobe->insn[i+1] == 0x1f))
return true;
if ((auprobe->insn[i] == 0x0f) && (auprobe->insn[i+1] == 0x19))
return true;
if ((auprobe->insn[i] == 0x87) && (auprobe->insn[i+1] == 0xc0))
return true;
break;
}
return false;