Fix can_boost() to identify indirect jmp and others using range case
correctly.
Since the condition in switch statement is opcode & 0xf0, it can not
evaluate to 0xff case. This should be under the 0xf0 case. However,
there is no reason to use the conbinations of the bit-masked condition
and lower bit checking.
Use range case to clean up the switch statement too.
Fixes: 6256e668b7 ("x86/kprobes: Use int3 instead of debug trap for single-step")
Reported-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
arch/x86/kernel/kprobes/core.c | 44 ++++++++++++++++++----------------------
1 file changed, 20 insertions(+), 24 deletions(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 503958f15cf9..c1c763840d6e 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -164,32 +164,28 @@ int can_boost(struct insn *insn, void *addr)
opcode = insn->opcode.bytes[0];
- switch (opcode & 0xf0) {
- case 0x60:
- /* can't boost "bound" */
- return (opcode != 0x62);
- case 0x70:
- return 0; /* can't boost conditional jump */
- case 0x90:
- return opcode != 0x9a; /* can't boost call far */
- case 0xc0:
- /* can't boost software-interruptions */
- return (0xc1 < opcode && opcode < 0xcc) || opcode == 0xcf;
- case 0xd0:
- /* can boost AA* and XLAT */
- return (opcode == 0xd4 || opcode == 0xd5 || opcode == 0xd7);
- case 0xe0:
- /* can boost in/out and absolute jmps */
- return ((opcode & 0x04) || opcode == 0xea);
- case 0xf0:
- /* clear and set flags are boostable */
- return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
- case 0xff:
- /* indirect jmp is boostable */
+ switch (opcode) {
+ case 0x62: /* bound */
+ case 0x70 ... 0x7f: /* Conditional jumps */
+ case 0x9a: /* Call far */
+ case 0xc0 ... 0xc1: /* Grp2 */
+ case 0xcc ... 0xce: /* software exceptions */
+ case 0xd0 ... 0xd3: /* Grp2 */
+ case 0xd6: /* (UD) */
+ case 0xd8 ... 0xdf: /* ESC */
+ case 0xe0 ... 0xe3: /* LOOP*, JCXZ */
+ case 0xe8 ... 0xe9: /* near Call, JMP */
+ case 0xeb: /* Short JMP */
+ case 0xf0 ... 0xf4: /* LOCK/REP, HLT */
+ case 0xf6 ... 0xf7: /* Grp3 */
+ case 0xfe: /* Grp4 */
+ /* ... are not boostable */
+ return 0;
+ case 0xff: /* Grp5 */
+ /* Only indirect jmp is boostable */
return X86_MODRM_REG(insn->modrm.bytes[0]) == 4;
default:
- /* call is not boostable */
- return opcode != 0x9a;
+ return 1;
}
}
