Messages in this thread | | | Date | Sun, 4 Jan 2015 13:16:02 +0800 | From | Wang Nan <> | Subject | Re: [PATCH v18 10/11] ARM: kprobes: check register usage for probed instruction. |
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On 2015/1/4 13:05, Masami Hiramatsu wrote: > Hi Wang, > > (2014/12/29 13:07), Wang Nan wrote: >> This patch utilizes previous introduced checker to check register usage >> for probed ARM instruction and saves it in a mask. Futher patch will >> use such information to avoid simuation or emulation. >> >> Signed-off-by: Wang Nan <wangnan0@huawei.com> >> --- >> arch/arm/include/asm/probes.h | 12 ++++ >> arch/arm/probes/decode.c | 7 ++ >> arch/arm/probes/kprobes/actions-arm.c | 2 +- >> arch/arm/probes/kprobes/checkers-arm.c | 124 +++++++++++++++++++++++++++++++++ >> arch/arm/probes/kprobes/checkers.h | 1 + >> 5 files changed, 145 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm/include/asm/probes.h b/arch/arm/include/asm/probes.h >> index f0a1ee8..ee04067 100644 >> --- a/arch/arm/include/asm/probes.h >> +++ b/arch/arm/include/asm/probes.h >> @@ -41,6 +41,18 @@ struct arch_probes_insn { >> probes_insn_singlestep_t *insn_singlestep; >> probes_insn_fn_t *insn_fn; >> int stack_space; >> + >> + /* Use 2 bits for a register. One more bit for extension */ > > Would you have any concrete idea for the extend bits? If not, we don't need > it at this point. I think we don't need to care about future binary compatibility :) > (moreover, if you need another bitflag, you can add another flag) >
2 bits can describe the read/write direction of a register. With such information, futher code is possible to utilize unused register to do some optimization. However, as you pointed, it is not a very concrete idea.
>> +#define REG_NO_USE (0) >> +#define REG_USE (1) >> +#define REG_MASK (3) >> +#define __register_usage_flag(n, f) ((f) << ((n) * 2)) >> +#define __register_usage_mask(n) (REG_MASK << ((n) * 2)) >> +#define __clean_register_flag(m, n) ((m) & (~(__register_usage_mask(n)))) >> +#define __set_register_flag(m, n, f) (__clean_register_flag(m, n) | __register_usage_flag(n, f)) >> +#define set_register_nouse(m, n) do {(m) = __set_register_flag(m, n, REG_NO_USE);} while(0) >> +#define set_register_use(m, n) do {(m) = __set_register_flag(m, n, REG_USE);} while(0) >> + int register_usage_mask; > > Is this a mask or flag? It seems a bit flag, if so, it should be "register_usage_flag". > > Thank you, >
OK, I'll rename it.
Thanks to your comment.
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