Messages in this thread Patch in this message | | | From | Guo Ren <> | Date | Fri, 25 Nov 2022 11:10:24 +0800 | Subject | Re: [PATCH 1/2] riscv/ftrace: add DYNAMIC_FTRACE_WITH_DIRECT_CALLS support |
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On Fri, Nov 25, 2022 at 9:53 AM Song Shuai <suagrfillet@gmail.com> wrote: > > Guo Ren <guoren@kernel.org> 于2022年11月24日周四 15:31写道: > > > > On Thu, Nov 24, 2022 at 1:27 AM Song Shuai <suagrfillet@gmail.com> wrote: > > > > > > Guo Ren <guoren@kernel.org> 于2022年11月23日周三 23:02写道: > > > > > > > > Cool job, thx. > > > > > > > > On Wed, Nov 23, 2022 at 10:20 PM Song Shuai <suagrfillet@gmail.com> wrote: > > > >> > > > >> This patch adds DYNAMIC_FTRACE_WITH_DIRECT_CALLS support for RISC-V. > > > >> > > > >> select the DYNAMIC_FTRACE_WITH_DIRECT_CALLS to provide the > > > >> register_ftrace_direct[_multi] interfaces allowing users to register > > > >> the customed trampoline (direct_caller) as the mcount for one or > > > >> more target functions. And modify_ftrace_direct[_multi] are also > > > >> provided for modifying direct_caller. > > > >> > > > >> To make the direct_caller and the other ftrace hooks (eg. function/fgraph > > > >> tracer, k[ret]probes) co-exist, a temporary register is nominated to > > > >> store the address of direct_caller in ftrace_regs_caller. After the > > > >> setting of the address direct_caller by direct_ops->func and the > > > >> RESTORE_REGS in ftrace_regs_caller, direct_caller will be jumped to > > > >> by the `jr` inst. > > > >> > > > >> Signed-off-by: Song Shuai <suagrfillet@gmail.com> > > > >> --- > > > >> arch/riscv/Kconfig | 1 + > > > >> arch/riscv/include/asm/ftrace.h | 6 ++++++ > > > >> arch/riscv/kernel/mcount-dyn.S | 4 ++++ > > > >> 3 files changed, 11 insertions(+) > > > >> > > > >> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > > > >> index 39ec8d628cf6..d083ec08d0b6 100644 > > > >> --- a/arch/riscv/Kconfig > > > >> +++ b/arch/riscv/Kconfig > > > >> @@ -278,6 +278,7 @@ config ARCH_RV64I > > > >> select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 > > > >> select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && MMU && $(cc-option,-fpatchable-function-entry=8) > > > >> select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE > > > >> + select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > > > >> select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL > > > >> select HAVE_FUNCTION_GRAPH_TRACER > > > >> select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION > > > >> diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h > > > >> index 01bebb28eabe..be4d57566139 100644 > > > >> --- a/arch/riscv/include/asm/ftrace.h > > > >> +++ b/arch/riscv/include/asm/ftrace.h > > > >> @@ -114,6 +114,12 @@ struct ftrace_regs; > > > >> void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, > > > >> struct ftrace_ops *op, struct ftrace_regs *fregs); > > > >> #define ftrace_graph_func ftrace_graph_func > > > >> + > > > >> +static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr) > > > >> +{ > > > >> + regs->t1 = addr; > > > > > > > > How about regs->t0 = addr; ? > > > > And delete all mcount-dyn.S modification. > > > > > > > The direct_caller has the same program layout as the ftrace_caller, which means > > > the reg t0 will never be changed when direct_caller returns. > > > > > > If regs->t0 changes here and ftrace_regs_caller executes `jr t0`, > > > direct_caller will enter the dead loop. > > > > > > Actually the reg t0 always saves the address of function entry with 8B > > > offset, it should only > > > changed by the IPMODIFY ops instead of the direct_ops. > > How about: > > static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs, > > unsigned long addr) > > { > > regs->t1 = regs->t0; > > regs->t0 = addr; > > > > direct_caller: > > add sp,sp,-? > > sd t1,?(sp) > direct_caller also serves as the first trampoline as ftrace_caller, like this: > ``` > func -- direct_caller > -- ftrace_[regs]_caller > ``` > So the t1 in this line has to be t0 to save the PC.
direct_caller: add sp,sp,-? sd t1,?(sp) sd t0, ?(so) sd ra,?(sp) mov t0, t1 call foo ld t0,?(sp) ld t1,?(sp) ld ra,?(sp) add sp,sp,? jr t1 // <- back to function entry
> > sd ra,?(sp) > > call foo > > ld t1,?(sp) > And this line. > > ld ra,?(sp) > > add sp,sp,? > > jr t1 // <- back to function entry > > > > And delete all mcount-dyn.S modification. > > > > > >> > > > >> +} > > > >> + > > > >> #endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */ > > > >> > > > >> #endif /* __ASSEMBLY__ */ > > > >> diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S > > > >> index 466c6ef217b1..b89c85a58569 100644 > > > >> --- a/arch/riscv/kernel/mcount-dyn.S > > > >> +++ b/arch/riscv/kernel/mcount-dyn.S > > > >> @@ -233,6 +233,7 @@ ENDPROC(ftrace_caller) > > > >> #else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */ > > > >> ENTRY(ftrace_regs_caller) > > > >> SAVE_ABI_REGS 1 > > > >> + REG_S x0, PT_T1(sp) > > > >> PREPARE_ARGS > > > >> > > > >> ftrace_regs_call: > > > >> @@ -241,7 +242,10 @@ ftrace_regs_call: > > > >> > > > >> > > > >> RESTORE_ABI_REGS 1 > > > >> + bnez t1,.Ldirect > > > >> jr t0 > > > >> +.Ldirect: > > > >> + jr t1 > > > >> ENDPROC(ftrace_regs_caller) > > > >> > > > >> ENTRY(ftrace_caller) > > > >> -- > > > >> 2.20.1 > > > >> > > > > > > > > > > > > -- > > > > Best Regards > > > > Guo Ren > > > > > > > > -- > > Best Regards > > Guo Ren > Thanks, > Song
-- Best Regards Guo Ren
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