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Date: Tue, 15 Nov 2022 18:44:50 +0800
From: Qing Zhang <zhangqing@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>, loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org, Jinyang He <hejinyang@...ngson.cn>
Subject: Re: [PATCH v6 5/9] LoongArch/ftrace: Add DYNAMIC_FTRACE_WITH_REGS
support
Hi, huacai
On 2022/11/15 下午5:24, Huacai Chen wrote:
> On Tue, Nov 15, 2022 at 5:22 PM Qing Zhang <zhangqing@...ngson.cn> wrote:
>>
>> 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.
> From the commit message it seems DYNAMIC_FTRACE_WITH_ARGS depend on
> DYNAMIC_FTRACE_WITH_REGS.
DYNAMIC_FTRACE_WITH_REGS : which allows trace function saved registers,
It means that these registers can be modified, eg: Kprobe、Livepatch.
DYNAMIC_FTRACE_WITH_ARGS: uses pt_regs as a parameter for get sp,
which means it can be used to access registers on the stack, and
use graph_ops::func to install return_hooker to replace the special
hook, eg: Livepatch.
From the following Kconfig, they are reasonable as separate patches.
config LIVEPATCH
bool "Kernel Live Patching"
depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS
Thanks
- Qing
>
> Huacai
>>
>> Thanks,
>> -Qing
>>>
>>> Huacai
>>>
>>> On Tue, Nov 15, 2022 at 10:55 AM Qing Zhang <zhangqing@...ngson.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@...ngson.cn>
>>>> Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
>>>> Signed-off-by: Qing Zhang <zhangqing@...ngson.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
>>>>
>>>>
>>
>>
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