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[-tip,2/2] x86: kprobes: Prohibit probing on instruction which has Xen prefix

Message ID 156759756944.24473.4664241966878257420.stgit@devnote2 (mailing list archive)
State New, archived
Headers show
Series x86: Prohibit kprobes on XEN_EMULATE_PREFIX | expand

Commit Message

Masami Hiramatsu (Google) Sept. 4, 2019, 11:46 a.m. UTC
Prohibit probing on instruction which has XEN_EMULATE_PREFIX
(it must be cpuid.) Since that prefix is a marker for Xen,
if we modify the marker by kprobe's int3, that doesn't work
as expected.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
 arch/x86/kernel/kprobes/core.c |    4 ++++
 1 file changed, 4 insertions(+)
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diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 43fc13c831af..b1e86af4a985 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -351,6 +351,10 @@  int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn)
 	kernel_insn_init(insn, dest, MAX_INSN_SIZE);
+	/* We can not probe XEN_EMULATE_PREFIX instruction */
+	if (insn_has_xen_prefix(insn))
+		return 0;
 	/* Another subsystem puts a breakpoint, failed to recover */
 	if (insn->opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
 		return 0;