Messages in this thread | | | Date | Tue, 22 Feb 2022 15:54:44 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH] arm64/ftrace: Make function graph use ftrace directly |
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On Tue, Feb 22, 2022 at 09:00:49PM +0800, Chengming Zhou wrote: > As we do in commit 0c0593b45c9b ("x86/ftrace: Make function graph > use ftrace directly"), we don't need special hook for graph tracer, > but instead we use graph_ops:func function to install return_hooker. > > Since commit 3b23e4991fb6 ("arm64: implement ftrace with regs") add > implementation for FTRACE_WITH_REGS on arm64, we can easily adopt > the same optimization on arm64.
This is a nice cleanup/refactoring, but I don't think this is an optimization as such; we're still doing the same work, just in marginally different place. So I'd suggest s/optimization/cleanup/ here.
It's probably worth noting that this *only* changes the FTRACE_WITH_REGS implementation, and the mcount-based implementation is unaffected by this patch.
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> > --- > arch/arm64/include/asm/ftrace.h | 7 +++++++ > arch/arm64/kernel/entry-ftrace.S | 6 ------ > arch/arm64/kernel/ftrace.c | 21 +++++++++++++++++++++ > 3 files changed, 28 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index 1494cfa8639b..dbc45a4157fa 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -80,8 +80,15 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) > > #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > struct dyn_ftrace; > +struct ftrace_ops; > +struct ftrace_regs; > + > int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec); > #define ftrace_init_nop ftrace_init_nop > + > +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 > #endif > > #define ftrace_return_address(n) return_address(n) > diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S > index e535480a4069..eb4a69b1f84d 100644 > --- a/arch/arm64/kernel/entry-ftrace.S > +++ b/arch/arm64/kernel/entry-ftrace.S > @@ -97,12 +97,6 @@ SYM_CODE_START(ftrace_common) > SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) > bl ftrace_stub > > -#ifdef CONFIG_FUNCTION_GRAPH_TRACER > -SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL) // ftrace_graph_caller(); > - nop // If enabled, this will be replaced > - // "b ftrace_graph_caller" > -#endif > -
You should also be able to delete the FTRACE_WITH_REGS implementation of ftrace_graph_caller since that's now unused.
Having that in the diff would also make it easier to compare to the logic in ftrace_graph_func().
> /* > * At the callsite x0-x8 and x19-x30 were live. Any C code will have preserved > * x19-x29 per the AAPCS, and we created frame records upon entry, so we need > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > index 4506c4a90ac1..1b5da231b1de 100644 > --- a/arch/arm64/kernel/ftrace.c > +++ b/arch/arm64/kernel/ftrace.c > @@ -268,6 +268,26 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent, > } > > #ifdef CONFIG_DYNAMIC_FTRACE > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS > +int ftrace_enable_ftrace_graph_caller(void) > +{ > + return 0; > +} > + > +int ftrace_disable_ftrace_graph_caller(void) > +{ > + return 0; > +}
It's a shame the core code doesn't provide this if we provide an implementation of ftrace_graph_func.
> + > +void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, > + struct ftrace_ops *op, struct ftrace_regs *fregs) > +{ > + struct pt_regs *regs = arch_ftrace_get_regs(fregs); > + unsigned long *parent = (unsigned long *)&procedure_link_pointer(regs); > + > + prepare_ftrace_return(ip, parent, frame_pointer(regs)); > +}
Other than my comments above, this looks about right, but I'd like to give this some testing before I give any tags.
Could you respin this with the FTRACE_WITH_REGS ftrace_graph_caller asm removed?
Thanks, Mark.
> +#else > /* > * Turn on/off the call to ftrace_graph_caller() in ftrace_caller() > * depending on @enable. > @@ -297,5 +317,6 @@ int ftrace_disable_ftrace_graph_caller(void) > { > return ftrace_modify_graph_caller(false); > } > +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */ > #endif /* CONFIG_DYNAMIC_FTRACE */ > #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ > -- > 2.20.1 >
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