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Commit b64b9c93 authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

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: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
parent ec75fba9

arch/x86/kernel/uprobes.c

+2 −14
Original line number Diff line number Diff line
@@ -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;