Messages in this thread Patch in this message | | | Date | Tue, 17 Jan 2023 19:22:30 +0300 | Subject | Re: [PATCH -next V7 6/7] samples: ftrace: Add riscv support for SAMPLE_FTRACE_DIRECT[_MULTI] | From | Evgenii Shatokhin <> |
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On 17.01.2023 16:16, Evgenii Shatokhin wrote: > Hi, Song, > > On 17.01.2023 12:32, Song Shuai wrote: >> >> Hi, Evgenii: >> >> Evgenii Shatokhin <e.shatokhin@yadro.com> 于2023年1月16日周一 14:30写道: >> >>> >>> Hi, >>> >>> On 12.01.2023 12:06, guoren@kernel.org wrote: >>>> From: Song Shuai <suagrfillet@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@gmail.com> >>>> Tested-by: Guo Ren <guoren@kernel.org> >>>> Signed-off-by: Guo Ren <guoren@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.
I have checked ftrace-direct-multi.ko and ftrace-direct-multi-modify.ko on 6.2-rc4 built for x86-64 - yes, ip/pc in the traced function should be passed to my_direct_func().
ftrace-direct-multi.ko: # TASK-PID CPU# ||||| TIMESTAMP FUNCTION # | | | ||||| | | insmod-10829 [000] d.h1. 1719.518535: my_direct_func: ip ffffffff87332f45 // wake_up_process+0x5 rcu_tasks_kthre-11 [000] ..... 1719.518696: my_direct_func: ip ffffffff8828d935 // schedule+0x5 insmod-10829 [000] ..... 1719.518708: my_direct_func: ip ffffffff8828d935 systemd-journal-293 [001] ..... 1719.518823: my_direct_func: ip ffffffff8828d935 systemd-1 [000] ..... 1719.519141: my_direct_func: ip ffffffff8828d935 <idle>-0 [001] ..s1. 1719.521889: my_direct_func: ip ffffffff87332f45 <idle>-0 [000] d.s2. 1719.521901: my_direct_func: ip ffffffff87332f45 rcu_preempt-15 [001] ..... 1719.521917: my_direct_func: ip ffffffff8828d935 [...]
The ip values are wake_up_process+0x5 and schedule+0x5, the locations where the execution of the traced functions resumes after the Ftrace trampoline has finished.
The results with ftrace-direct-multi-modify.ko are similar to that.
The samples look like a demonstration, that one can pass anything necessary to the handler in case of "direct" functions.
I suppose, the RISC-V-specific asm code in these two sample modules could be updated to pass the saved pc value to my_direct_func() in a0.
> >> >> 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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