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uprobes/x86: Emulate relative conditional "near" jmp's

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Change branch_setup_xol_ops() to simply use opc1 = OPCODE2(insn) - 0x10
if OPCODE1() == 0x0f; this matches the "short" jmp which checks the same
condition.

Thanks to lib/insn.c, it does the rest correctly. branch->ilen/offs are
correct no matter if this jmp is "near" or "short".

Reported-by: Jonathan Lebon <jlebon@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
This commit is contained in:
Oleg Nesterov 2014-04-07 16:22:58 +02:00
parent 8f95505bc1
commit 6cc5e7ff2c
1 changed files with 8 additions and 0 deletions
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8
arch/x86/kernel/uprobes.c
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@ -599,6 +599,14 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
branch_clear_offset(auprobe, insn);
break;
case 0x0f:
if (insn->opcode.nbytes != 2)
return -ENOSYS;
/*
* If it is a "near" conditional jmp, OPCODE2() - 0x10 matches
* OPCODE1() of the "short" jmp which checks the same condition.
*/
opc1 = OPCODE2(insn) - 0x10;
default:
if (!is_cond_jmp_opcode(opc1))
return -ENOSYS;