Re: [PATCH v10 7/8] LoongArch: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

[Huacai Chen]

Reviewed-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>

On Fri, Mar 31, 2023 at 8:48 PM Donglin Peng <pengdonglin@xxxxxxxxxxxxxx> 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 LoongArch platform.
>
> We introduce a new structure called fgraph_ret_regs for the LoongArch
> 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@xxxxxxxxxxxxxx>
> ---
> v10:
>  - Fix code style issues for LoongArch
>  - Use CONFIG_FUNCTION_GRAPH_TRACER to control fgraph_ret_regs definition
>
> v9:
>  - Fix stack pointer align issues
>  - Update the commit message
>
> v8:
>  - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> ---
>  arch/loongarch/Kconfig              |  1 +
>  arch/loongarch/include/asm/ftrace.h | 22 ++++++++++++++++++++++
>  arch/loongarch/kernel/asm-offsets.c | 15 ++++++++++++++-
>  arch/loongarch/kernel/mcount.S      | 14 ++++++++------
>  arch/loongarch/kernel/mcount_dyn.S  | 15 ++++++++-------
>  5 files changed, 53 insertions(+), 14 deletions(-)
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 7fd51257e0ed..4bf60132869b 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -99,6 +99,7 @@ config LOONGARCH
>         select HAVE_FAST_GUP
>         select HAVE_FTRACE_MCOUNT_RECORD
>         select HAVE_FUNCTION_ARG_ACCESS_API
> +       select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
>         select HAVE_FUNCTION_GRAPH_TRACER
>         select HAVE_FUNCTION_TRACER
>         select HAVE_GENERIC_VDSO
> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
> index 3418d32d4fc7..22797b7504b5 100644
> --- a/arch/loongarch/include/asm/ftrace.h
> +++ b/arch/loongarch/include/asm/ftrace.h
> @@ -63,4 +63,26 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
>
>  #endif /* CONFIG_FUNCTION_TRACER */
>
> +#ifndef __ASSEMBLY__
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +struct fgraph_ret_regs {
> +       /* a0 - a1 */
> +       unsigned long regs[2];
> +
> +       unsigned long fp;
> +       unsigned long __unused;
> +};
> +
> +static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
> +{
> +       return ret_regs->regs[0];
> +}
> +
> +static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
> +{
> +       return ret_regs->fp;
> +}
> +#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
> +#endif
> +
>  #endif /* _ASM_LOONGARCH_FTRACE_H */
> diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
> index 4bdb203fc66e..505e4bf59603 100644
> --- a/arch/loongarch/kernel/asm-offsets.c
> +++ b/arch/loongarch/kernel/asm-offsets.c
> @@ -12,6 +12,7 @@
>  #include <asm/cpu-info.h>
>  #include <asm/ptrace.h>
>  #include <asm/processor.h>
> +#include <asm/ftrace.h>
>
>  void output_ptreg_defines(void)
>  {
> @@ -264,7 +265,7 @@ void output_smpboot_defines(void)
>  #ifdef CONFIG_HIBERNATION
>  void output_pbe_defines(void)
>  {
> -       COMMENT(" Linux struct pbe offsets. ");
> +       COMMENT("Linux struct pbe offsets.");
>         OFFSET(PBE_ADDRESS, pbe, address);
>         OFFSET(PBE_ORIG_ADDRESS, pbe, orig_address);
>         OFFSET(PBE_NEXT, pbe, next);
> @@ -272,3 +273,15 @@ void output_pbe_defines(void)
>         BLANK();
>  }
>  #endif
> +
> +#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> +void output_fgraph_ret_regs_defines(void)
> +{
> +       COMMENT("LoongArch fgraph_ret_regs offsets.");
> +       OFFSET(FGRET_REGS_A0, fgraph_ret_regs, regs[0]);
> +       OFFSET(FGRET_REGS_A1, fgraph_ret_regs, regs[1]);
> +       OFFSET(FGRET_REGS_FP, fgraph_ret_regs, fp);
> +       DEFINE(FGRET_REGS_SIZE, sizeof(struct fgraph_ret_regs));
> +       BLANK();
> +}
> +#endif
> diff --git a/arch/loongarch/kernel/mcount.S b/arch/loongarch/kernel/mcount.S
> index 8cdc1563cd33..cb8e5803de4b 100644
> --- a/arch/loongarch/kernel/mcount.S
> +++ b/arch/loongarch/kernel/mcount.S
> @@ -79,18 +79,20 @@ SYM_FUNC_START(ftrace_graph_caller)
>  SYM_FUNC_END(ftrace_graph_caller)
>
>  SYM_FUNC_START(return_to_handler)
> -       PTR_ADDI        sp, sp, -2 * SZREG
> -       PTR_S           a0, sp, 0
> -       PTR_S           a1, sp, SZREG
> +       PTR_ADDI        sp, sp, -FGRET_REGS_SIZE
> +       PTR_S           a0, sp, FGRET_REGS_A0
> +       PTR_S           a1, sp, FGRET_REGS_A1
> +       PTR_S           zero, sp, FGRET_REGS_FP
>
> +       move            a0, sp
>         bl              ftrace_return_to_handler
>
>         /* Restore the real parent address: a0 -> ra */
>         move            ra, a0
>
> -       PTR_L           a0, sp, 0
> -       PTR_L           a1, sp, SZREG
> -       PTR_ADDI        sp, sp, 2 * SZREG
> +       PTR_L           a0, sp, FGRET_REGS_A0
> +       PTR_L           a1, sp, FGRET_REGS_A1
> +       PTR_ADDI        sp, sp, FGRET_REGS_SIZE
>         jr              ra
>  SYM_FUNC_END(return_to_handler)
>  #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
> diff --git a/arch/loongarch/kernel/mcount_dyn.S b/arch/loongarch/kernel/mcount_dyn.S
> index bbabf06244c2..ec24ae1de741 100644
> --- a/arch/loongarch/kernel/mcount_dyn.S
> +++ b/arch/loongarch/kernel/mcount_dyn.S
> @@ -131,18 +131,19 @@ SYM_CODE_END(ftrace_graph_caller)
>
>  SYM_CODE_START(return_to_handler)
>         /* Save return value regs */
> -       PTR_ADDI        sp, sp, -2 * SZREG
> -       PTR_S           a0, sp, 0
> -       PTR_S           a1, sp, SZREG
> +       PTR_ADDI        sp, sp, -FGRET_REGS_SIZE
> +       PTR_S           a0, sp, FGRET_REGS_A0
> +       PTR_S           a1, sp, FGRET_REGS_A1
> +       PTR_S           zero, sp, FGRET_REGS_FP
>
> -       move            a0, zero
> +       move            a0, sp
>         bl              ftrace_return_to_handler
>         move            ra, a0
>
>         /* Restore return value regs */
> -       PTR_L           a0, sp, 0
> -       PTR_L           a1, sp, SZREG
> -       PTR_ADDI        sp, sp, 2 * SZREG
> +       PTR_L           a0, sp, FGRET_REGS_A0
> +       PTR_L           a1, sp, FGRET_REGS_A1
> +       PTR_ADDI        sp, sp, FGRET_REGS_SIZE
>
>         jr              ra
>  SYM_CODE_END(return_to_handler)
> --
> 2.25.1
>