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Subject[RFC PATCH tip/master V3 3/8] kprobes/x86: Use instruction decoder for booster
Date
Use x86 instruction decoder for checking whether the probed
instruction is able to boost or not, instead of hand-written
code.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/x86/kernel/kprobes/core.c | 39 ++++++++++++++++-----------------------
1 file changed, 16 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 81d4dc7..6327f95 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -169,35 +169,33 @@ NOKPROBE_SYMBOL(skip_prefixes);
*/
int can_boost(kprobe_opcode_t *opcodes, void *addr)
{
+ struct insn insn;
kprobe_opcode_t opcode;
- kprobe_opcode_t *orig_opcodes = opcodes;

if (search_exception_tables((unsigned long)addr))
return 0; /* Page fault may occur on this address. */

-retry:
- if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
- return 0;
- opcode = *(opcodes++);
+ kernel_insn_init(&insn, (void *)opcodes, MAX_INSN_SIZE);
+ insn_get_opcode(&insn);

/* 2nd-byte opcode */
- if (opcode == 0x0f) {
- if (opcodes - orig_opcodes > MAX_INSN_SIZE - 1)
- return 0;
- return test_bit(*opcodes,
+ if (insn.opcode.nbytes == 2)
+ return test_bit(insn.opcode.bytes[1],
(unsigned long *)twobyte_is_boostable);
- }
+
+ if (insn.opcode.nbytes != 1)
+ return 0;
+
+ /* Can't boost Address-size override prefix */
+ if (unlikely(inat_is_address_size_prefix(insn.attr)))
+ return 0;
+
+ opcode = insn.opcode.bytes[0];

switch (opcode & 0xf0) {
-#ifdef CONFIG_X86_64
- case 0x40:
- goto retry; /* REX prefix is boostable */
-#endif
case 0x60:
- if (0x63 < opcode && opcode < 0x67)
- goto retry; /* prefixes */
- /* can't boost Address-size override and bound */
- return (opcode != 0x62 && opcode != 0x67);
+ /* can't boost "bound" */
+ return (opcode != 0x62);
case 0x70:
return 0; /* can't boost conditional jump */
case 0x90:
@@ -212,14 +210,9 @@ int can_boost(kprobe_opcode_t *opcodes, void *addr)
/* can boost in/out and absolute jmps */
return ((opcode & 0x04) || opcode == 0xea);
case 0xf0:
- if ((opcode & 0x0c) == 0 && opcode != 0xf1)
- goto retry; /* lock/rep(ne) prefix */
/* clear and set flags are boostable */
return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe));
default:
- /* segment override prefixes are boostable */
- if (opcode == 0x26 || opcode == 0x36 || opcode == 0x3e)
- goto retry; /* prefixes */
/* CS override prefix and call are not boostable */
return (opcode != 0x2e && opcode != 0x9a);
}
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