Messages in this thread | | | Date | Tue, 17 Jan 2023 16:16:54 +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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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.
> > 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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