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| author |   Wang Nan <wangnan0@huawei.com> | 2015-01-09 14:37:36 +0800 |
|---|---|---|
| committer |   Jon Medhurst <tixy@linaro.org> | 2015-01-13 16:10:17 +0000 |
| commit | 0dc016dbd820260b8ea74337980735b8c88d4ef2 (patch) | |
| tree | 0a6408b4181016d41858afec026cc4e93455f852 /arch/arm/include/asm/kprobes.h | |
| parent | kprobes: Pass the original kprobe for preparing optimized kprobe (diff) | |
| download | linux-dev-0dc016dbd820260b8ea74337980735b8c88d4ef2.tar.xz linux-dev-0dc016dbd820260b8ea74337980735b8c88d4ef2.zip | |
ARM: kprobes: enable OPTPROBES for ARM 32
This patch introduce kprobeopt for ARM 32.
Limitations:
- Currently only kernel compiled with ARM ISA is supported.
- Offset between probe point and optinsn slot must not larger than
32MiB. Masami Hiramatsu suggests replacing 2 words, it will make
things complex. Futher patch can make such optimization.
Kprobe opt on ARM is relatively simpler than kprobe opt on x86 because
ARM instruction is always 4 bytes aligned and 4 bytes long. This patch
replace probed instruction by a 'b', branch to trampoline code and then
calls optimized_callback(). optimized_callback() calls opt_pre_handler()
to execute kprobe handler. It also emulate/simulate replaced instruction.
When unregistering kprobe, the deferred manner of unoptimizer may leave
branch instruction before optimizer is called. Different from x86_64,
which only copy the probed insn after optprobe_template_end and
reexecute them, this patch call singlestep to emulate/simulate the insn
directly. Futher patch can optimize this behavior.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: Jon Medhurst (Tixy) <tixy@linaro.org>
Signed-off-by: Jon Medhurst <tixy@linaro.org>
Diffstat (limited to 'arch/arm/include/asm/kprobes.h')
| -rw-r--r-- | arch/arm/include/asm/kprobes.h | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/arch/arm/include/asm/kprobes.h b/arch/arm/include/asm/kprobes.h index 56f9ac68fbd1..50ff3bc7928e 100644 --- a/arch/arm/include/asm/kprobes.h +++ b/arch/arm/include/asm/kprobes.h @@ -50,5 +50,34 @@ int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr); int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, void *data); +/* optinsn template addresses */ +extern __visible kprobe_opcode_t optprobe_template_entry; +extern __visible kprobe_opcode_t optprobe_template_val; +extern __visible kprobe_opcode_t optprobe_template_call; +extern __visible kprobe_opcode_t optprobe_template_end; +extern __visible kprobe_opcode_t optprobe_template_sub_sp; +extern __visible kprobe_opcode_t optprobe_template_add_sp; + +#define MAX_OPTIMIZED_LENGTH 4 +#define MAX_OPTINSN_SIZE \ + ((unsigned long)&optprobe_template_end - \ + (unsigned long)&optprobe_template_entry) +#define RELATIVEJUMP_SIZE 4 + +struct arch_optimized_insn { + /* + * copy of the original instructions. + * Different from x86, ARM kprobe_opcode_t is u32. + */ +#define MAX_COPIED_INSN DIV_ROUND_UP(RELATIVEJUMP_SIZE, sizeof(kprobe_opcode_t)) + kprobe_opcode_t copied_insn[MAX_COPIED_INSN]; + /* detour code buffer */ + kprobe_opcode_t *insn; + /* + * We always copy one instruction on ARM, + * so size will always be 4, and unlike x86, there is no + * need for a size field. + */ +}; #endif /* _ARM_KPROBES_H */ |