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Subject: Re: [PATCH v6 5/9] LoongArch/ftrace: Add DYNAMIC_FTRACE_WITH_REGS
 support
To:     Huacai Chen <chenhuacai@kernel.org>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>, loongarch@lists.linux.dev,
        linux-kernel@vger.kernel.org, Jinyang He <hejinyang@loongson.cn>
References: <20221115025527.13382-1-zhangqing@loongson.cn>
 <20221115025527.13382-6-zhangqing@loongson.cn>
 <CAAhV-H6ceu-UfSNBEpBJOvOtvuS8hufoiEtjAT1fXdQX+T11Kg@mail.gmail.com>
From:   Qing Zhang <zhangqing@loongson.cn>
Message-ID: <1288f936-7e43-592a-8061-d9df94573c4d@loongson.cn>
Date:   Tue, 15 Nov 2022 17:22:49 +0800
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Hi, Huacai

On 2022/11/15 下午4:41, Huacai Chen wrote:
> Hi, Qing,
> 
> Patch5 and Patch6 are small and related, maybe they can be combined
> with a name "LoongArch/ftrace: Add DYNAMIC_FTRACE_WITH_{ARGS,REGS}
> support"
I think they should be independent due to different use scenarios.

Thanks,
-Qing
> 
> Huacai
> 
> On Tue, Nov 15, 2022 at 10:55 AM Qing Zhang <zhangqing@loongson.cn> wrote:
>>
>> This patch implements DYNAMIC_FTRACE_WITH_REGS on LoongArch, which allows
>> a traced function's arguments (and some other registers) to be captured
>> into a struct pt_regs, allowing these to be inspected and modified.
>>
>> Co-developed-by: Jinyang He <hejinyang@loongson.cn>
>> Signed-off-by: Jinyang He <hejinyang@loongson.cn>
>> Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
>> ---
>>   arch/loongarch/Kconfig              |  1 +
>>   arch/loongarch/include/asm/ftrace.h |  3 +++
>>   arch/loongarch/kernel/ftrace_dyn.c  | 17 ++++++++++++++
>>   arch/loongarch/kernel/mcount-dyn.S  | 36 +++++++++++++++++++++++++++--
>>   4 files changed, 55 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
>> index 615ce62422b8..12e3e91a68ae 100644
>> --- a/arch/loongarch/Kconfig
>> +++ b/arch/loongarch/Kconfig
>> @@ -90,6 +90,7 @@ config LOONGARCH
>>          select HAVE_DEBUG_STACKOVERFLOW
>>          select HAVE_DMA_CONTIGUOUS
>>          select HAVE_DYNAMIC_FTRACE
>> +       select HAVE_DYNAMIC_FTRACE_WITH_REGS
>>          select HAVE_EBPF_JIT
>>          select HAVE_EXIT_THREAD
>>          select HAVE_FAST_GUP
>> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
>> index 76ca58767f4d..a3f974a7a5ce 100644
>> --- a/arch/loongarch/include/asm/ftrace.h
>> +++ b/arch/loongarch/include/asm/ftrace.h
>> @@ -28,6 +28,9 @@ struct dyn_ftrace;
>>   int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
>>   #define ftrace_init_nop ftrace_init_nop
>>
>> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
>> +#define ARCH_SUPPORTS_FTRACE_OPS 1
>> +#endif
>>   #endif /* CONFIG_DYNAMIC_FTRACE */
>>   #endif /* __ASSEMBLY__ */
>>   #endif /* CONFIG_FUNCTION_TRACER */
>> diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c
>> index 3fe791b6783e..ec3d951be50c 100644
>> --- a/arch/loongarch/kernel/ftrace_dyn.c
>> +++ b/arch/loongarch/kernel/ftrace_dyn.c
>> @@ -99,6 +99,23 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
>>          return ftrace_modify_code(pc, old, new, true);
>>   }
>>
>> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
>> +int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
>> +                       unsigned long addr)
>> +{
>> +       unsigned long pc;
>> +       long offset;
>> +       u32 old, new;
>> +
>> +       pc = rec->ip + LOONGARCH_INSN_SIZE;
>> +
>> +       old = larch_insn_gen_bl(pc, old_addr);
>> +       new = larch_insn_gen_bl(pc, addr);
>> +
>> +       return ftrace_modify_code(pc, old, new, true);
>> +}
>> +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
>> +
>>   void arch_ftrace_update_code(int command)
>>   {
>>          command |= FTRACE_MAY_SLEEP;
>> diff --git a/arch/loongarch/kernel/mcount-dyn.S b/arch/loongarch/kernel/mcount-dyn.S
>> index 0c12cc108e6f..02835186b463 100644
>> --- a/arch/loongarch/kernel/mcount-dyn.S
>> +++ b/arch/loongarch/kernel/mcount-dyn.S
>> @@ -27,7 +27,7 @@
>>    * follows the LoongArch psABI well.
>>    */
>>
>> -       .macro  ftrace_regs_entry
>> +       .macro  ftrace_regs_entry allregs=0
>>          PTR_ADDI sp, sp, -PT_SIZE
>>          /* Save trace function ra at PT_ERA */
>>          PTR_S   ra, sp, PT_ERA
>> @@ -43,16 +43,48 @@
>>          PTR_S   a7, sp, PT_R11
>>          PTR_S   fp, sp, PT_R22
>>
>> +       .if \allregs
>> +       PTR_S   t0, sp, PT_R12
>> +       PTR_S   t1, sp, PT_R13
>> +       PTR_S   t2, sp, PT_R14
>> +       PTR_S   t3, sp, PT_R15
>> +       PTR_S   t4, sp, PT_R16
>> +       PTR_S   t5, sp, PT_R17
>> +       PTR_S   t6, sp, PT_R18
>> +       PTR_S   t7, sp, PT_R19
>> +       PTR_S   t8, sp, PT_R20
>> +       PTR_S   s0, sp, PT_R23
>> +       PTR_S   s1, sp, PT_R24
>> +       PTR_S   s2, sp, PT_R25
>> +       PTR_S   s3, sp, PT_R26
>> +       PTR_S   s4, sp, PT_R27
>> +       PTR_S   s5, sp, PT_R28
>> +       PTR_S   s6, sp, PT_R29
>> +       PTR_S   s7, sp, PT_R30
>> +       PTR_S   s8, sp, PT_R31
>> +       PTR_S   tp, sp, PT_R2
>> +       /* Clear it for later use as a flag sometimes. */
>> +       PTR_S   zero, sp, PT_R0
>> +       PTR_S   $r21, sp, PT_R21
>> +       .endif
>> +
>>          PTR_ADDI t8, sp, PT_SIZE
>>          PTR_S   t8, sp, PT_R3
>>
>>          .endm
>>
>>   SYM_CODE_START(ftrace_caller)
>> -       ftrace_regs_entry
>> +       ftrace_regs_entry allregs=0
>>          b       ftrace_common
>>   SYM_CODE_END(ftrace_caller)
>>
>> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
>> +SYM_CODE_START(ftrace_regs_caller)
>> +       ftrace_regs_entry allregs=1
>> +       b       ftrace_common
>> +SYM_CODE_END(ftrace_regs_caller)
>> +#endif
>> +
>>   SYM_CODE_START(ftrace_common)
>>          PTR_ADDI        a0, ra, -8      /* arg0: ip */
>>          move            a1, t0          /* arg1: parent_ip */
>> --
>> 2.36.0
>>
>>