[Xen-devel] [PATCH -tip v3 2/2] x86: kprobes: Prohibit probing on instruction which has emulate prefix

[Masami Hiramatsu <mhiramat@xxxxxxxxxx>]

Prohibit probing on instruction which has XEN_EMULATE_PREFIX
or KVM's emulate prefix. Since that prefix is a marker for Xen
and KVM, if we modify the marker by kprobe's int3, that doesn't
work as expected.

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
 arch/x86/kernel/kprobes/core.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 43fc13c831af..4f13af7cbcdb 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);
        insn_get_length(insn);
 
+       /* We can not probe force emulate prefixed instruction */
+       if (insn_has_emulate_prefix(insn))
+               return 0;
+
        /* Another subsystem puts a breakpoint, failed to recover */
        if (insn->opcode.bytes[0] == BREAKPOINT_INSTRUCTION)
                return 0;


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