x86: introduce REX prefix helper for kprobes
Fold some small ifdefs into a helper function.
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 4e33329..b1804e4 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -171,6 +171,19 @@
}
/*
+ * Check for the REX prefix which can only exist on X86_64
+ * X86_32 always returns 0
+ */
+static int __kprobes is_REX_prefix(kprobe_opcode_t *insn)
+{
+#ifdef CONFIG_X86_64
+ if ((*insn & 0xf0) == 0x40)
+ return 1;
+#endif
+ return 0;
+}
+
+/*
* Returns non-zero if opcode is boostable.
* RIP relative instructions are adjusted at copying time in 64 bits mode
*/
@@ -239,14 +252,14 @@
case 0x9d: /* popf/popfd */
return 1;
}
-#ifdef CONFIG_X86_64
+
/*
- * on 64 bit x86, 0x40-0x4f are prefixes so we need to look
+ * on X86_64, 0x40-0x4f are REX prefixes so we need to look
* at the next byte instead.. but of course not recurse infinitely
*/
- if (*insn >= 0x40 && *insn <= 0x4f)
+ if (is_REX_prefix(insn))
return is_IF_modifier(++insn);
-#endif
+
return 0;
}
@@ -284,7 +297,7 @@
}
/* Skip REX instruction prefix. */
- if ((*insn & 0xf0) == 0x40)
+ if (is_REX_prefix(insn))
++insn;
if (*insn == 0x0f) {
@@ -748,11 +761,9 @@
unsigned long orig_ip = (unsigned long)p->addr;
kprobe_opcode_t *insn = p->ainsn.insn;
-#ifdef CONFIG_X86_64
/*skip the REX prefix*/
- if (*insn >= 0x40 && *insn <= 0x4f)
+ if (is_REX_prefix(insn))
insn++;
-#endif
regs->flags &= ~X86_EFLAGS_TF;
switch (*insn) {