lkml.org 
[lkml]   [2014]   [Dec]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v17 11/11] ARM: optprobes: execute instruction during restoring if possible.
On 2014/12/29 6:10, Masami Hiramatsu wrote:
> (2014/12/27 16:36), Wang Nan wrote:
>> This patch removes software emulation or simulation for most of probed
>> instructions. If the instruction doesn't use PC relative addressing,
>> it will be translated into following instructions in the restore code
>> in code template:
>>
>> ldmia {r0 - r14} // restore all instruction except PC
>> <instruction> // direct execute the probed instruction
>> b next_insn // branch to next instruction.
>>
>> Signed-off-by: Wang Nan <wangnan0@huawei.com>
>> ---
>> arch/arm/include/asm/kprobes.h | 3 +++
>> arch/arm/include/asm/probes.h | 1 +
>> arch/arm/probes/kprobes/opt-arm.c | 47 +++++++++++++++++++++++++++++++++++++--
>> 3 files changed, 49 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/kprobes.h b/arch/arm/include/asm/kprobes.h
>> index 50ff3bc..3ea9be5 100644
>> --- a/arch/arm/include/asm/kprobes.h
>> +++ b/arch/arm/include/asm/kprobes.h
>> @@ -57,6 +57,9 @@ 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;
>> +extern __visible kprobe_opcode_t optprobe_template_restore_begin;
>> +extern __visible kprobe_opcode_t optprobe_template_restore_orig_insn;
>> +extern __visible kprobe_opcode_t optprobe_template_restore_end;
>>
>> #define MAX_OPTIMIZED_LENGTH 4
>> #define MAX_OPTINSN_SIZE \
>> diff --git a/arch/arm/include/asm/probes.h b/arch/arm/include/asm/probes.h
>> index ee8725c..8ebbe83 100644
>> --- a/arch/arm/include/asm/probes.h
>> +++ b/arch/arm/include/asm/probes.h
>> @@ -50,6 +50,7 @@ struct arch_probes_insn {
>> #define set_register_nouse(m, n) __clear_register_flag(m, n, REG_NO_USE)
>> #define set_register_use(m, n) __set_register_flag(m, n, REG_USE)
>> int register_usage_mask;
>> + bool kprobe_direct_exec;
>> };
>>
>> #endif /* __ASSEMBLY__ */
>> diff --git a/arch/arm/probes/kprobes/opt-arm.c b/arch/arm/probes/kprobes/opt-arm.c
>> index 6a60df3..f3bd1cc 100644
>> --- a/arch/arm/probes/kprobes/opt-arm.c
>> +++ b/arch/arm/probes/kprobes/opt-arm.c
>> @@ -32,6 +32,13 @@
>> #include "core.h"
>>
>> /*
>> + * See register_usage_mask. If the probed instruction doesn't use PC,
>> + * we can copy it into template and have it executed directly without
>> + * simulation or emulation.
>> + */
>> +#define can_kprobe_direct_exec(m) (!((m) & 0xc0000000UL))
>
> I think you'd better define a macro for this bitmask.
>
>
>> +
>> +/*
>> * NOTE: the first sub and add instruction will be modified according
>> * to the stack cost of the instruction.
>> */
>> @@ -66,7 +73,15 @@ asm (
>> " orrne r2, #1\n"
>> " strne r2, [sp, #60] @ set bit0 of PC for thumb\n"
>> " msr cpsr_cxsf, r1\n"
>> + ".global optprobe_template_restore_begin\n"
>> + "optprobe_template_restore_begin:\n"
>> " ldmia sp, {r0 - r15}\n"
>> + ".global optprobe_template_restore_orig_insn\n"
>> + "optprobe_template_restore_orig_insn:\n"
>> + " nop\n"
>> + ".global optprobe_template_restore_end\n"
>> + "optprobe_template_restore_end:\n"
>> + " ldmia sp, {r13 - r15}\n"
>
> Why this can't be a nop too?
>
> Thank you,
>

Good suggestion. I'll send a new version of patch 10 and 11.

Thank you.





\
 
 \ /
  Last update: 2014-12-29 05:21    [W:0.069 / U:0.280 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site