[RFC PATCH v2 6/6] uprobes/x86: Emulate rip-relative conditional "near" jmp's

[Oleg Nesterov <oleg@redhat.com>]

It seems that 16bit condi jmp is just 0x0f + short_jump_opc_plus_0x10.

Reported-by: Jonathan Lebon <jlebon@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 arch/x86/kernel/uprobes.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index ab9342a..cdad38d 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -588,6 +588,14 @@ static int ttt_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
 		ttt_clear_displacement(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;
-- 
1.5.5.1