Messages in this thread | | | From | Guo Ren <> | Date | Sun, 21 May 2023 23:22:50 +0800 | Subject | Re: [PATCH V9 3/4] riscv: ftrace: Add DYNAMIC_FTRACE_WITH_DIRECT_CALLS support |
| |
On Thu, May 11, 2023 at 9:30 PM Evgenii Shatokhin <e.shatokhin@yadro.com> wrote: > > Hi, > > On 11.05.2023 10:19, Björn Töpel wrote: > > Song Shuai <suagrfillet@gmail.com> writes: > > > >> 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> > >> Tested-by: Guo Ren <guoren@kernel.org> > >> Signed-off-by: Guo Ren <guoren@kernel.org> > >> --- > >> arch/riscv/Kconfig | 1 + > >> arch/riscv/include/asm/ftrace.h | 8 ++++++++ > >> arch/riscv/kernel/mcount-dyn.S | 10 ++++++++++ > >> 3 files changed, 19 insertions(+) > >> > >> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > >> index e0632493482f..fdf0b219a02c 100644 > >> --- a/arch/riscv/Kconfig > >> +++ b/arch/riscv/Kconfig > >> @@ -144,6 +144,7 @@ config RISCV > >> select UACCESS_MEMCPY if !MMU > >> select ZONE_DMA32 if 64BIT > >> select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && MMU && (CLANG_SUPPORTS_DYNAMIC_FTRACE || GCC_SUPPORTS_DYNAMIC_FTRACE) > >> + select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > >> select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE > >> select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL > >> select HAVE_FUNCTION_GRAPH_TRACER > >> diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h > >> index 84f856a3286e..84904c1e4369 100644 > >> --- a/arch/riscv/include/asm/ftrace.h > >> +++ b/arch/riscv/include/asm/ftrace.h > >> @@ -114,6 +114,14 @@ 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; > >> +} > >> +#define arch_ftrace_set_direct_caller(fregs, addr) \ > >> + __arch_ftrace_set_direct_caller(&(fregs)->regs, addr) > >> #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 f26e9f6e2fed..9d405baedb52 100644 > >> --- a/arch/riscv/kernel/mcount-dyn.S > >> +++ b/arch/riscv/kernel/mcount-dyn.S > >> @@ -231,6 +231,7 @@ ENDPROC(ftrace_caller) > >> > >> #else /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */ > >> ENTRY(ftrace_regs_caller) > >> + move t1, zero > > > > Please use "mv", and not "move" [1]. > > > >> SAVE_ABI_REGS 1 > >> PREPARE_ARGS > >> > >> @@ -239,7 +240,10 @@ ftrace_regs_call: > >> call ftrace_stub > >> > >> RESTORE_ABI_REGS 1 > >> + bnez t1,.Ldirect > >> jr t0 > >> +.Ldirect: > >> + jr t1 > > > > Again, while you're doing changes here, please try to align op/operands. > > > > Wearing my BPF hat, I'm happy to finally get DIRECT_CALLS support! > > > > This does not take the WITH_CALL_OPS approach Mark suggested in the v7 > > threads, but given that text patching story on RISC-V is still a bit sad > > (inconsistency in the RV tree, no specification, cannot work with > > preempt, ...) I'd say this approach is OK for now, and we can change to > > WITH_CALL_OPS later in a wider "let's improve RISC-V textpatching" work. > > > > Thoughts? > > The WITH_CALL_OPS approach seems to need much more time and effort, so, > yes, I'd also use this implementation of DIRECT_CALLS for now. Other > improvements could wait for the future "big patching rework". I agree to make DIRECT_CALLS merged first, WITH_CALL_OPS is another "big patching rework".
> > FWIW, the implementation of kprobes for RISC-V has been improving > gradually too, not everything was done in the first very patchset, but > it was usable nonetheless. > > I have not tested this particular version of this > DYNAMIC_FTRACE_WITH_DIRECT_CALLS series, only some previous ones - there > were no outstanding problems there. The code looks sane to me. > > > > > > > Björn > > > > [1] https://github.com/riscv-non-isa/riscv-asm-manual/blob/master/riscv-asm.md#-a-listing-of-standard-risc-v-pseudoinstructions > > > > Regards, > Evgenii > >
-- Best Regards Guo Ren
| |