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Date:   Thu, 8 Jun 2023 21:58:34 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Donglin Peng <pengdonglin@sangfor.com.cn>
Cc:     mhiramat@kernel.org, linux@armlinux.org.uk, mark.rutland@arm.com,
        will@kernel.org, catalin.marinas@arm.com,
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        paul.walmsley@sifive.com, aou@eecs.berkeley.edu,
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        zhangqing@loongson.cn, kernel@xen0n.name, mingo@redhat.com,
        peterz@infradead.org, xiehuan09@gmail.com, dinghui@sangfor.com.cn,
        huangcun@sangfor.com.cn, dolinux.peng@gmail.com,
        linux-trace-kernel@vger.kernel.org, loongarch@lists.linux.dev,
        linux-riscv@lists.infradead.org,
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Subject: Re: [PATCH v11 5/8] riscv: ftrace: Enable
 HAVE_FUNCTION_GRAPH_RETVAL
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        <a8d71b12259f90e7e63d0ea654fcac95b0232bbc.1680954589.git.pengdonglin@sangfor.com.cn>
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Can I get an ack from a RISC-V maintainer?

-- Steve


On Sat,  8 Apr 2023 05:42:19 -0700
Donglin Peng <pengdonglin@sangfor.com.cn> wrote:

> The previous patch ("function_graph: Support recording and printing
> the return value of function") has laid the groundwork for the for
> the funcgraph-retval, and this modification makes it available on
> the RISC-V platform.
> 
> We introduce a new structure called fgraph_ret_regs for the RISC-V
> platform to hold return registers and the frame pointer. We then
> fill its content in the return_to_handler and pass its address to
> the function ftrace_return_to_handler to record the return value.
> 
> Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
> ---
> v10:
>  - Use CONFIG_FUNCTION_GRAPH_TRACER to control fgraph_ret_regs definition
> 
> v9:
>  - Update the commit message
> 
> v8:
>  - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> ---
>  arch/riscv/Kconfig              |  1 +
>  arch/riscv/include/asm/ftrace.h | 21 +++++++++++++++++++++
>  arch/riscv/kernel/mcount.S      |  7 +------
>  3 files changed, 23 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index eb7f29a412f8..108538815309 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -139,6 +139,7 @@ config RISCV
>  	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_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
> +	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
>  	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 d47d87c2d7e3..740a979171e5 100644
> --- a/arch/riscv/include/asm/ftrace.h
> +++ b/arch/riscv/include/asm/ftrace.h
> @@ -111,4 +111,25 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
>  
>  #endif /* CONFIG_DYNAMIC_FTRACE */
>  
> +#ifndef __ASSEMBLY__
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +struct fgraph_ret_regs {
> +	unsigned long a1;
> +	unsigned long a0;
> +	unsigned long s0;
> +	unsigned long ra;
> +};
> +
> +static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
> +{
> +	return ret_regs->a0;
> +}
> +
> +static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
> +{
> +	return ret_regs->s0;
> +}
> +#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
> +#endif
> +
>  #endif /* _ASM_RISCV_FTRACE_H */
> diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
> index 30102aadc4d7..8a6e5a9e842a 100644
> --- a/arch/riscv/kernel/mcount.S
> +++ b/arch/riscv/kernel/mcount.S
> @@ -65,13 +65,8 @@ ENTRY(return_to_handler)
>   * So alternatively we check the *old* frame pointer position, that is, the
>   * value stored in -16(s0) on entry, and the s0 on return.
>   */
> -#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
> -	mv	t6, s0
> -#endif
>  	SAVE_RET_ABI_STATE
> -#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
> -	mv	a0, t6
> -#endif
> +	mv	a0, sp
>  	call	ftrace_return_to_handler
>  	mv	a2, a0
>  	RESTORE_RET_ABI_STATE