Messages in this thread | | | Date | Thu, 11 May 2023 16:30:44 +0300 | Subject | Re: [PATCH V9 3/4] riscv: ftrace: Add DYNAMIC_FTRACE_WITH_DIRECT_CALLS support | From | Evgenii Shatokhin <> |
| |
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".
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
| |