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x86/kprobes: Fix to identify indirect jmp and others using range case 

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@canonical.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/161666692308.1120877.4675552834049546493.stgit@devnote2
This commit is contained in:
Masami Hiramatsu 2021-03-25 19:08:43 +09:00 committed by Ingo Molnar
parent 6dd3b8c9f5
commit 2f706e0e5e
1 changed files with 20 additions and 24 deletions
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44
arch/x86/kernel/kprobes/core.c
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@ -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;
}
}