Re: [PATCH v21 03/20] fgraph: Replace fgraph_ret_regs with ftrace_regs

Steven Rostedt
2024-12-19T21:34:11Z

On Tue, 10 Dec 2024 11:09:26 +0900
"Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> Use ftrace_regs instead of fgraph_ret_regs for tracing return value
> on function_graph tracer because of simplifying the callback interface.
>
> The CONFIG_HAVE_FUNCTION_GRAPH_RETVAL is also replaced by
> CONFIG_HAVE_FUNCTION_GRAPH_FREGS.
>
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> Acked-by: Heiko Carstens <hca@linux.ibm.com>

Did Heiko ack this? I don't see it in my inbox.

> ---
> Changes in v18:
> - Use PTREGS_SIZE instead of redefining FRAME_SIZE on i386.
> Changes in v17:
> - Fixes s390 return_to_handler according to Heiko's advice.

I see the comments, but I want to make sure Heiko is happy with this.

> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 0077969170e8..102029e56cf0 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -192,7 +192,7 @@ config S390
> select HAVE_FTRACE_MCOUNT_RECORD
> select HAVE_FUNCTION_ARG_ACCESS_API
> select HAVE_FUNCTION_ERROR_INJECTION
> - select HAVE_FUNCTION_GRAPH_RETVAL
> + select HAVE_FUNCTION_GRAPH_FREGS
> select HAVE_FUNCTION_GRAPH_TRACER
> select HAVE_FUNCTION_TRACER
> select HAVE_GCC_PLUGINS
> diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
> index fc97d75dc752..5c94c1fc1bc1 100644
> --- a/arch/s390/include/asm/ftrace.h
> +++ b/arch/s390/include/asm/ftrace.h
> @@ -62,23 +62,6 @@ static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs *
> return NULL;
> }
>
> -#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -struct fgraph_ret_regs {
> - unsigned long gpr2;
> - unsigned long fp;
> -};
> -
> -static __always_inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
> -{
> - return ret_regs->gpr2;
> -}
> -
> -static __always_inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
> -{
> - return ret_regs->fp;
> -}
> -#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
> -
> static __always_inline void
> ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs,
> unsigned long ip)
> @@ -86,6 +69,13 @@ ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs,
> arch_ftrace_regs(fregs)->regs.psw.addr = ip;
> }
>
> +#undef ftrace_regs_get_frame_pointer
> +static __always_inline unsigned long
> +ftrace_regs_get_frame_pointer(struct ftrace_regs *fregs)
> +{
> + return ftrace_regs_get_stack_pointer(fregs);
> +}
> +
> #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> /*
> * When an ftrace registered caller is tracing a function that is
> diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
> index 862a9140528e..36709112ae7a 100644
> --- a/arch/s390/kernel/asm-offsets.c
> +++ b/arch/s390/kernel/asm-offsets.c
> @@ -175,12 +175,6 @@ int main(void)
> DEFINE(OLDMEM_SIZE, PARMAREA + offsetof(struct parmarea, oldmem_size));
> DEFINE(COMMAND_LINE, PARMAREA + offsetof(struct parmarea, command_line));
> DEFINE(MAX_COMMAND_LINE_SIZE, PARMAREA + offsetof(struct parmarea, max_command_line_size));
> -#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> - /* function graph return value tracing */
> - OFFSET(__FGRAPH_RET_GPR2, fgraph_ret_regs, gpr2);
> - OFFSET(__FGRAPH_RET_FP, fgraph_ret_regs, fp);
> - DEFINE(__FGRAPH_RET_SIZE, sizeof(struct fgraph_ret_regs));
> -#endif
> OFFSET(__FTRACE_REGS_PT_REGS, __arch_ftrace_regs, regs);
> DEFINE(__FTRACE_REGS_SIZE, sizeof(struct __arch_ftrace_regs));
>
> diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
> index 7e267ef63a7f..2b628aa3d809 100644
> --- a/arch/s390/kernel/mcount.S
> +++ b/arch/s390/kernel/mcount.S
> @@ -134,14 +134,14 @@ SYM_CODE_END(ftrace_common)
> SYM_FUNC_START(return_to_handler)
> stmg %r2,%r5,32(%r15)
> lgr %r1,%r15
> - aghi %r15,-(STACK_FRAME_OVERHEAD+__FGRAPH_RET_SIZE)
> + # allocate ftrace_regs and stack frame for ftrace_return_to_handler
> + aghi %r15,-STACK_FRAME_SIZE_FREGS
> stg %r1,__SF_BACKCHAIN(%r15)
> - la %r3,STACK_FRAME_OVERHEAD(%r15)
> - stg %r1,__FGRAPH_RET_FP(%r3)
> - stg %r2,__FGRAPH_RET_GPR2(%r3)
> - lgr %r2,%r3
> + stg %r2,(STACK_FREGS_PTREGS_GPRS+2*8)(%r15)
> + stg %r1,(STACK_FREGS_PTREGS_GPRS+15*8)(%r15)
> + la %r2,STACK_FRAME_OVERHEAD(%r15)
> brasl %r14,ftrace_return_to_handler
> - aghi %r15,STACK_FRAME_OVERHEAD+__FGRAPH_RET_SIZE
> + aghi %r15,STACK_FRAME_SIZE_FREGS
> lgr %r14,%r2
> lmg %r2,%r5,32(%r15)
> BR_EX %r14

Heiko,

Does the above look OK to you?

Thanks,

-- Steve