uprobes/x86: Only rep+nop can be emulated correctly (b64b9c93) · Commits · 戴 / test

__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>

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;

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