[PATCH -next V7 6/7] samples: ftrace: Add riscv support for SAMPLE_FTRACE_DIRECT[_MULTI]
Evgenii Shatokhin
e.shatokhin at yadro.com
Tue Jan 17 05:16:54 PST 2023
Hi, Song,
On 17.01.2023 12:32, Song Shuai wrote:
>
> Hi, Evgenii:
>
> Evgenii Shatokhin <e.shatokhin at yadro.com> 于2023年1月16日周一 14:30写道：
>
>>
>> Hi,
>>
>> On 12.01.2023 12:06, guoren at kernel.org wrote:
>>> From: Song Shuai <suagrfillet at gmail.com>
>>>
>>> select HAVE_SAMPLE_FTRACE_DIRECT and HAVE_SAMPLE_FTRACE_DIRECT_MULTI
>>> for ARCH_RV64I in arch/riscv/Kconfig. And add riscv asm code for
>>> the ftrace-direct*.c files in samples/ftrace/.
>>>
>>> Signed-off-by: Song Shuai <suagrfillet at gmail.com>
>>> Tested-by: Guo Ren <guoren at kernel.org>
>>> Signed-off-by: Guo Ren <guoren at kernel.org>
>>> ---
>>> arch/riscv/Kconfig | 2 ++
>>> samples/ftrace/ftrace-direct-modify.c | 33 ++++++++++++++++++
>>> samples/ftrace/ftrace-direct-multi-modify.c | 37 +++++++++++++++++++++
>>> samples/ftrace/ftrace-direct-multi.c | 22 ++++++++++++
>>> samples/ftrace/ftrace-direct-too.c | 26 +++++++++++++++
>>> samples/ftrace/ftrace-direct.c | 22 ++++++++++++
>>> 6 files changed, 142 insertions(+)
>>
>> The samples were built OK now, but ftrace-direct-multi and
>> ftrace-direct-multi-modify report incorrect values of ip/pc it seems.
>>
>> I ran 'insmod ftrace-direct-multi.ko', waited a little and then checked
>> the messages in the trace:
>>
>> # TASK-PID CPU# ||||| TIMESTAMP FUNCTION
>> # | | | ||||| | |
>> migration/1-19 [001] ..... 3858.532131: my_direct_func1: my
>> direct func1 ip 0
>> migration/0-15 [000] d.s2. 3858.532136: my_direct_func1: my
>> direct func1 ip ff60000001ba9600
>> migration/0-15 [000] d..2. 3858.532204: my_direct_func1: my
>> direct func1 ip ff60000003334d00
>> migration/0-15 [000] ..... 3858.532232: my_direct_func1: my
>> direct func1 ip 0
>> rcu_sched-14 [001] ..... 3858.532257: my_direct_func1: my
>> direct func1 ip 0
>> insmod-415 [000] ..... 3858.532270: my_direct_func1: my
>> direct func1 ip 7fffffffffffffff
>> <idle>-0 [001] ..s1. 3858.539051: my_direct_func1: my
>> direct func1 ip ff60000001ba9600
>> <idle>-0 [001] dns2. 3858.539124: my_direct_func1: my
>> direct func1 ip ff60000001ba9600
>> rcu_sched-14 [001] ..... 3858.539208: my_direct_func1: my
>> direct func1 ip 0
>> [...]
>>
>> If I understand it right, my_direct_func1() should print the address of
>> some location in the code, probably - at the beginning of the traced
>> functions.
>>
>> The printed values (0x0, 0x7fffffffffffffff, ...) are not valid code
>> addresses.
>>
> The invalid code address is only printed by accessing the schedule()
> function's first argument whose address stores in a0 register.
> While schedule() actually has no parameter declared, so my_direct_func
> just prints the a0 in the context of the schedule()'s caller and
> the address maybe varies depending on the caller.
>
> I can't really understand why tracing the first argument of the
> schedule() function, but it seems nonsense at this point.
The question is, what should be passed as the argument(s) of
my_direct_func() in this particular sample module. The kernel docs and
commit logs seem to contain no info on that.
With direct functions, I suppose, the trampoline can pass anything it
wants to my_direct_func(), not just the arguments of the traced function.
I'd check what these sample modules do on x86 and would try to match
that behaviour on RISC-V.
>
> As for this patch, it just impls a simple mcount (direct_caller) to
> trace kernel functions, and basically saves the necessary ABI,
> call the tracing function, and restores the ABI, just like other arches do.
> so It shouldn't be blamed.
>
> I started an independent patch to replace schedule with kick_process
> to make these samples more reasonable. And It has no conflict with the
> current patch, so we can go on.
>
> Link: https://lore.kernel.org/linux-kernel/20230117091101.3669996-1-suagrfillet@gmail.com/T/#u
>
>> The same issue is with ftrace-direct-multi-modify.ko.
>>
>> Is anything missing here?
>>
>>>
>>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>>> index 307a9f413edd..e944af44f681 100644
>>> --- a/arch/riscv/Kconfig
>>> +++ b/arch/riscv/Kconfig
>>> @@ -112,6 +112,8 @@ config RISCV
>>> select HAVE_POSIX_CPU_TIMERS_TASK_WORK
>>> select HAVE_REGS_AND_STACK_ACCESS_API
>>> select HAVE_FUNCTION_ARG_ACCESS_API
>>> + select HAVE_SAMPLE_FTRACE_DIRECT
>>> + select HAVE_SAMPLE_FTRACE_DIRECT_MULTI
>>> select HAVE_STACKPROTECTOR
>>> select HAVE_SYSCALL_TRACEPOINTS
>>> select HAVE_RSEQ
>>> diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c
>>> index de5a0f67f320..be7bf472c3c7 100644
>>> --- a/samples/ftrace/ftrace-direct-modify.c
>>> +++ b/samples/ftrace/ftrace-direct-modify.c
>>> @@ -23,6 +23,39 @@ extern void my_tramp2(void *);
>>>
>>> static unsigned long my_ip = (unsigned long)schedule;
>>>
>>> +#ifdef CONFIG_RISCV
>>> +
>>> +asm (" .pushsection .text, \"ax\", @progbits\n"
>>> +" .type my_tramp1, @function\n"
>>> +" .globl my_tramp1\n"
>>> +" my_tramp1:\n"
>>> +" addi sp,sp,-16\n"
>>> +" sd t0,0(sp)\n"
>>> +" sd ra,8(sp)\n"
>>> +" call my_direct_func1\n"
>>> +" ld t0,0(sp)\n"
>>> +" ld ra,8(sp)\n"
>>> +" addi sp,sp,16\n"
>>> +" jr t0\n"
>>> +" .size my_tramp1, .-my_tramp1\n"
>>> +
>>> +" .type my_tramp2, @function\n"
>>> +" .globl my_tramp2\n"
>>> +" my_tramp2:\n"
>>> +" addi sp,sp,-16\n"
>>> +" sd t0,0(sp)\n"
>>> +" sd ra,8(sp)\n"
>>> +" call my_direct_func2\n"
>>> +" ld t0,0(sp)\n"
>>> +" ld ra,8(sp)\n"
>>> +" addi sp,sp,16\n"
>>> +" jr t0\n"
>>> +" .size my_tramp2, .-my_tramp2\n"
>>> +" .popsection\n"
>>> +);
>>> +
>>> +#endif /* CONFIG_RISCV */
>>> +
>>> #ifdef CONFIG_X86_64
>>>
>>> #include <asm/ibt.h>
>>> diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c
>>> index d52370cad0b6..10884bf418f7 100644
>>> --- a/samples/ftrace/ftrace-direct-multi-modify.c
>>> +++ b/samples/ftrace/ftrace-direct-multi-modify.c
>>> @@ -21,6 +21,43 @@ void my_direct_func2(unsigned long ip)
>>> extern void my_tramp1(void *);
>>> extern void my_tramp2(void *);
>>>
>>> +#ifdef CONFIG_RISCV
>>> +
>>> +asm (" .pushsection .text, \"ax\", @progbits\n"
>>> +" .type my_tramp1, @function\n"
>>> +" .globl my_tramp1\n"
>>> +" my_tramp1:\n"
>>> +" addi sp,sp,-24\n"
>>> +" sd a0,0(sp)\n"
>>> +" sd t0,8(sp)\n"
>>> +" sd ra,16(sp)\n"
>>> +" call my_direct_func1\n"
>>> +" ld a0,0(sp)\n"
>>> +" ld t0,8(sp)\n"
>>> +" ld ra,16(sp)\n"
>>> +" addi sp,sp,24\n"
>>> +" jr t0\n"
>>> +" .size my_tramp1, .-my_tramp1\n"
>>> +
>>> +" .type my_tramp2, @function\n"
>>> +" .globl my_tramp2\n"
>>> +" my_tramp2:\n"
>>> +" addi sp,sp,-24\n"
>>> +" sd a0,0(sp)\n"
>>> +" sd t0,8(sp)\n"
>>> +" sd ra,16(sp)\n"
>>> +" call my_direct_func2\n"
>>> +" ld a0,0(sp)\n"
>>> +" ld t0,8(sp)\n"
>>> +" ld ra,16(sp)\n"
>>> +" addi sp,sp,24\n"
>>> +" jr t0\n"
>>> +" .size my_tramp2, .-my_tramp2\n"
>>> +" .popsection\n"
>>> +);
>>> +
>>> +#endif /* CONFIG_RISCV */
>>> +
>>> #ifdef CONFIG_X86_64
>>>
>>> #include <asm/ibt.h>
>>> diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
>>> index ec1088922517..a35bf43bf6d7 100644
>>> --- a/samples/ftrace/ftrace-direct-multi.c
>>> +++ b/samples/ftrace/ftrace-direct-multi.c
>>> @@ -16,6 +16,28 @@ void my_direct_func(unsigned long ip)
>>>
>>> extern void my_tramp(void *);
>>>
>>> +#ifdef CONFIG_RISCV
>>> +
>>> +asm (" .pushsection .text, \"ax\", @progbits\n"
>>> +" .type my_tramp, @function\n"
>>> +" .globl my_tramp\n"
>>> +" my_tramp:\n"
>>> +" addi sp,sp,-24\n"
>>> +" sd a0,0(sp)\n"
>>> +" sd t0,8(sp)\n"
>>> +" sd ra,16(sp)\n"
>>> +" call my_direct_func\n"
>>> +" ld a0,0(sp)\n"
>>> +" ld t0,8(sp)\n"
>>> +" ld ra,16(sp)\n"
>>> +" addi sp,sp,24\n"
>>> +" jr t0\n"
>>> +" .size my_tramp, .-my_tramp\n"
>>> +" .popsection\n"
>>> +);
>>> +
>>> +#endif /* CONFIG_RISCV */
>>> +
>>> #ifdef CONFIG_X86_64
>>>
>>> #include <asm/ibt.h>
>>> diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
>>> index e13fb59a2b47..3b62e33c2e6d 100644
>>> --- a/samples/ftrace/ftrace-direct-too.c
>>> +++ b/samples/ftrace/ftrace-direct-too.c
>>> @@ -18,6 +18,32 @@ void my_direct_func(struct vm_area_struct *vma,
>>>
>>> extern void my_tramp(void *);
>>>
>>> +#ifdef CONFIG_RISCV
>>> +
>>> +asm (" .pushsection .text, \"ax\", @progbits\n"
>>> +" .type my_tramp, @function\n"
>>> +" .globl my_tramp\n"
>>> +" my_tramp:\n"
>>> +" addi sp,sp,-40\n"
>>> +" sd a0,0(sp)\n"
>>> +" sd a1,8(sp)\n"
>>> +" sd a2,16(sp)\n"
>>> +" sd t0,24(sp)\n"
>>> +" sd ra,32(sp)\n"
>>> +" call my_direct_func\n"
>>> +" ld a0,0(sp)\n"
>>> +" ld a1,8(sp)\n"
>>> +" ld a2,16(sp)\n"
>>> +" ld t0,24(sp)\n"
>>> +" ld ra,32(sp)\n"
>>> +" addi sp,sp,40\n"
>>> +" jr t0\n"
>>> +" .size my_tramp, .-my_tramp\n"
>>> +" .popsection\n"
>>> +);
>>> +
>>> +#endif /* CONFIG_RISCV */
>>> +
>>> #ifdef CONFIG_X86_64
>>>
>>> #include <asm/ibt.h>
>>> diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
>>> index 1f769d0db20f..2cfe5a7d2d70 100644
>>> --- a/samples/ftrace/ftrace-direct.c
>>> +++ b/samples/ftrace/ftrace-direct.c
>>> @@ -15,6 +15,28 @@ void my_direct_func(struct task_struct *p)
>>>
>>> extern void my_tramp(void *);
>>>
>>> +#ifdef CONFIG_RISCV
>>> +
>>> +asm (" .pushsection .text, \"ax\", @progbits\n"
>>> +" .type my_tramp, @function\n"
>>> +" .globl my_tramp\n"
>>> +" my_tramp:\n"
>>> +" addi sp,sp,-24\n"
>>> +" sd a0,0(sp)\n"
>>> +" sd t0,8(sp)\n"
>>> +" sd ra,16(sp)\n"
>>> +" call my_direct_func\n"
>>> +" ld a0,0(sp)\n"
>>> +" ld t0,8(sp)\n"
>>> +" ld ra,16(sp)\n"
>>> +" addi sp,sp,24\n"
>>> +" jr t0\n"
>>> +" .size my_tramp, .-my_tramp\n"
>>> +" .popsection\n"
>>> +);
>>> +
>>> +#endif /* CONFIG_RISCV */
>>> +
>>> #ifdef CONFIG_X86_64
>>>
>>> #include <asm/ibt.h>
>>> --
>>> 2.36.1
>
> --
> Thanks,
> Song
>
Regards,
Evgenii
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