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Subject[tip:perf/core] kprobes/x86: Use instruction decoder for booster
Commit-ID:  17880e4d5777df4770081ecf0750471cda57f86b
Gitweb: http://git.kernel.org/tip/17880e4d5777df4770081ecf0750471cda57f86b
Author: Masami Hiramatsu <mhiramat@kernel.org>
AuthorDate: Wed, 29 Mar 2017 13:59:15 +0900
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 12 Apr 2017 09:23:45 +0200

kprobes/x86: Use instruction decoder for booster

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>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ye Xiaolong <xiaolong.ye@intel.com>
Link: http://lkml.kernel.org/r/149076354563.22469.13379472209338986858.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@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 @@ retry:
/* 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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