Re: [PATCH v14 04/19] function_graph: Replace fgraph_ret_regs with ftrace_regs

[Steven Rostedt]

Can I get an Acked-by from the X86 maintainers for this patch?

Thanks!

-- Steve


On Fri, 13 Sep 2024 00:08:51 +0900
"Masami Hiramatsu (Google)" <mhiramat@xxxxxxxxxx> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
> 
> 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@xxxxxxxxxx>
> ---
>  Changes in v8:
>   - Newly added.
> ---
>  arch/arm64/Kconfig                  |    1 +
>  arch/arm64/include/asm/ftrace.h     |   23 ++++++-----------------
>  arch/arm64/kernel/asm-offsets.c     |   12 ------------
>  arch/arm64/kernel/entry-ftrace.S    |   32 ++++++++++++++++++--------------
>  arch/loongarch/Kconfig              |    2 +-
>  arch/loongarch/include/asm/ftrace.h |   24 ++----------------------
>  arch/loongarch/kernel/asm-offsets.c |   12 ------------
>  arch/loongarch/kernel/mcount.S      |   17 ++++++++++-------
>  arch/loongarch/kernel/mcount_dyn.S  |   14 +++++++-------
>  arch/riscv/Kconfig                  |    2 +-
>  arch/riscv/include/asm/ftrace.h     |   26 +++++---------------------
>  arch/riscv/kernel/mcount.S          |   24 +++++++++++++-----------
>  arch/s390/Kconfig                   |    2 +-
>  arch/s390/include/asm/ftrace.h      |   26 +++++++++-----------------
>  arch/s390/kernel/asm-offsets.c      |    6 ------
>  arch/s390/kernel/mcount.S           |    9 +++++----
>  arch/x86/Kconfig                    |    2 +-
>  arch/x86/include/asm/ftrace.h       |   22 ++--------------------
>  arch/x86/kernel/ftrace_32.S         |   15 +++++++++------
>  arch/x86/kernel/ftrace_64.S         |   17 +++++++++--------
>  include/linux/ftrace.h              |   14 +++++++++++---
>  kernel/trace/Kconfig                |    4 ++--
>  kernel/trace/fgraph.c               |   21 +++++++++------------
>  23 files changed, 122 insertions(+), 205 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index a2f8ff354ca6..17947f625b06 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -211,6 +211,7 @@ config ARM64
>  	select HAVE_FTRACE_MCOUNT_RECORD
>  	select HAVE_FUNCTION_TRACER
>  	select HAVE_FUNCTION_ERROR_INJECTION
> +	select HAVE_FUNCTION_GRAPH_FREGS
>  	select HAVE_FUNCTION_GRAPH_TRACER
>  	select HAVE_FUNCTION_GRAPH_RETVAL
>  	select HAVE_GCC_PLUGINS
> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
> index dc9cf0bd2a4c..dffaab3dd1f1 100644
> --- a/arch/arm64/include/asm/ftrace.h
> +++ b/arch/arm64/include/asm/ftrace.h
> @@ -126,6 +126,12 @@ ftrace_override_function_with_return(struct ftrace_regs *fregs)
>  	fregs->pc = fregs->lr;
>  }
>  
> +static __always_inline unsigned long
> +ftrace_regs_get_frame_pointer(const struct ftrace_regs *fregs)
> +{
> +	return fregs->fp;
> +}
> +
>  int ftrace_regs_query_register_offset(const char *name);
>  
>  int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
> @@ -183,23 +189,6 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
>  
>  #ifndef __ASSEMBLY__
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -struct fgraph_ret_regs {
> -	/* x0 - x7 */
> -	unsigned long regs[8];
> -
> -	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;
> -}
>  
>  void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
>  			   unsigned long frame_pointer);
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 27de1dddb0ab..9e03c9a7e5c3 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -201,18 +201,6 @@ int main(void)
>    DEFINE(FTRACE_OPS_FUNC,		offsetof(struct ftrace_ops, func));
>  #endif
>    BLANK();
> -#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -  DEFINE(FGRET_REGS_X0,			offsetof(struct fgraph_ret_regs, regs[0]));
> -  DEFINE(FGRET_REGS_X1,			offsetof(struct fgraph_ret_regs, regs[1]));
> -  DEFINE(FGRET_REGS_X2,			offsetof(struct fgraph_ret_regs, regs[2]));
> -  DEFINE(FGRET_REGS_X3,			offsetof(struct fgraph_ret_regs, regs[3]));
> -  DEFINE(FGRET_REGS_X4,			offsetof(struct fgraph_ret_regs, regs[4]));
> -  DEFINE(FGRET_REGS_X5,			offsetof(struct fgraph_ret_regs, regs[5]));
> -  DEFINE(FGRET_REGS_X6,			offsetof(struct fgraph_ret_regs, regs[6]));
> -  DEFINE(FGRET_REGS_X7,			offsetof(struct fgraph_ret_regs, regs[7]));
> -  DEFINE(FGRET_REGS_FP,			offsetof(struct fgraph_ret_regs, fp));
> -  DEFINE(FGRET_REGS_SIZE,		sizeof(struct fgraph_ret_regs));
> -#endif
>  #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
>    DEFINE(FTRACE_OPS_DIRECT_CALL,	offsetof(struct ftrace_ops, direct_call));
>  #endif
> diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
> index f0c16640ef21..169ccf600066 100644
> --- a/arch/arm64/kernel/entry-ftrace.S
> +++ b/arch/arm64/kernel/entry-ftrace.S
> @@ -329,24 +329,28 @@ SYM_FUNC_END(ftrace_stub_graph)
>   * @fp is checked against the value passed by ftrace_graph_caller().
>   */
>  SYM_CODE_START(return_to_handler)
> -	/* save return value regs */
> -	sub sp, sp, #FGRET_REGS_SIZE
> -	stp x0, x1, [sp, #FGRET_REGS_X0]
> -	stp x2, x3, [sp, #FGRET_REGS_X2]
> -	stp x4, x5, [sp, #FGRET_REGS_X4]
> -	stp x6, x7, [sp, #FGRET_REGS_X6]
> -	str x29,    [sp, #FGRET_REGS_FP]	// parent's fp
> +	/* Make room for ftrace_regs */
> +	sub	sp, sp, #FREGS_SIZE
> +
> +	/* Save return value regs */
> +	stp	x0, x1, [sp, #FREGS_X0]
> +	stp	x2, x3, [sp, #FREGS_X2]
> +	stp	x4, x5, [sp, #FREGS_X4]
> +	stp	x6, x7, [sp, #FREGS_X6]
> +
> +	/* Save the callsite's FP */
> +	str	x29, [sp, #FREGS_FP]
>  
>  	mov	x0, sp
> -	bl	ftrace_return_to_handler	// addr = ftrace_return_to_hander(regs);
> +	bl	ftrace_return_to_handler	// addr = ftrace_return_to_hander(fregs);
>  	mov	x30, x0				// restore the original return address
>  
> -	/* restore return value regs */
> -	ldp x0, x1, [sp, #FGRET_REGS_X0]
> -	ldp x2, x3, [sp, #FGRET_REGS_X2]
> -	ldp x4, x5, [sp, #FGRET_REGS_X4]
> -	ldp x6, x7, [sp, #FGRET_REGS_X6]
> -	add sp, sp, #FGRET_REGS_SIZE
> +	/* Restore return value regs */
> +	ldp	x0, x1, [sp, #FREGS_X0]
> +	ldp	x2, x3, [sp, #FREGS_X2]
> +	ldp	x4, x5, [sp, #FREGS_X4]
> +	ldp	x6, x7, [sp, #FREGS_X6]
> +	add	sp, sp, #FREGS_SIZE
>  
>  	ret
>  SYM_CODE_END(return_to_handler)
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 70f169210b52..974f08f65f63 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -131,7 +131,7 @@ config LOONGARCH
>  	select HAVE_FTRACE_MCOUNT_RECORD
>  	select HAVE_FUNCTION_ARG_ACCESS_API
>  	select HAVE_FUNCTION_ERROR_INJECTION
> -	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
> +	select HAVE_FUNCTION_GRAPH_FREGS
>  	select HAVE_FUNCTION_GRAPH_TRACER
>  	select HAVE_FUNCTION_TRACER
>  	select HAVE_GCC_PLUGINS
> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
> index 6f8517d59954..1a73f35ea9af 100644
> --- a/arch/loongarch/include/asm/ftrace.h
> +++ b/arch/loongarch/include/asm/ftrace.h
> @@ -77,6 +77,8 @@ ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs, unsigned long ip)
>  	override_function_with_return(&(fregs)->regs)
>  #define ftrace_regs_query_register_offset(name) \
>  	regs_query_register_offset(name)
> +#define ftrace_regs_get_frame_pointer(fregs) \
> +	((fregs)->regs.regs[22])
>  
>  #define ftrace_graph_func ftrace_graph_func
>  void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
> @@ -99,26 +101,4 @@ __arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr)
>  
>  #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 bee9f7a3108f..714f5b5f1956 100644
> --- a/arch/loongarch/kernel/asm-offsets.c
> +++ b/arch/loongarch/kernel/asm-offsets.c
> @@ -279,18 +279,6 @@ static void __used output_pbe_defines(void)
>  }
>  #endif
>  
> -#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -static void __used 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
> -
>  static void __used output_kvm_defines(void)
>  {
>  	COMMENT("KVM/LoongArch Specific offsets.");
> diff --git a/arch/loongarch/kernel/mcount.S b/arch/loongarch/kernel/mcount.S
> index 3015896016a0..b6850503e061 100644
> --- a/arch/loongarch/kernel/mcount.S
> +++ b/arch/loongarch/kernel/mcount.S
> @@ -79,10 +79,11 @@ SYM_FUNC_START(ftrace_graph_caller)
>  SYM_FUNC_END(ftrace_graph_caller)
>  
>  SYM_FUNC_START(return_to_handler)
> -	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
> +	/* Save return value regs */
> +	PTR_ADDI	sp, sp, -PT_SIZE
> +	PTR_S		a0, sp, PT_R4
> +	PTR_S		a1, sp, PT_R5
> +	PTR_S		zero, sp, PT_R22
>  
>  	move		a0, sp
>  	bl		ftrace_return_to_handler
> @@ -90,9 +91,11 @@ SYM_FUNC_START(return_to_handler)
>  	/* Restore the real parent address: a0 -> ra */
>  	move		ra, a0
>  
> -	PTR_L		a0, sp, FGRET_REGS_A0
> -	PTR_L		a1, sp, FGRET_REGS_A1
> -	PTR_ADDI	sp, sp, FGRET_REGS_SIZE
> +	/* Restore return value regs */
> +	PTR_L		a0, sp, PT_R4
> +	PTR_L		a1, sp, PT_R5
> +	PTR_ADDI	sp, sp, PT_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 0c65cf09110c..d6b474ad1d5e 100644
> --- a/arch/loongarch/kernel/mcount_dyn.S
> +++ b/arch/loongarch/kernel/mcount_dyn.S
> @@ -140,19 +140,19 @@ SYM_CODE_END(ftrace_graph_caller)
>  SYM_CODE_START(return_to_handler)
>  	UNWIND_HINT_UNDEFINED
>  	/* Save return value regs */
> -	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
> +	PTR_ADDI	sp, sp, -PT_SIZE
> +	PTR_S		a0, sp, PT_R4
> +	PTR_S		a1, sp, PT_R5
> +	PTR_S		zero, sp, PT_R22
>  
>  	move		a0, sp
>  	bl		ftrace_return_to_handler
>  	move		ra, a0
>  
>  	/* Restore return value regs */
> -	PTR_L		a0, sp, FGRET_REGS_A0
> -	PTR_L		a1, sp, FGRET_REGS_A1
> -	PTR_ADDI	sp, sp, FGRET_REGS_SIZE
> +	PTR_L		a0, sp, PT_R4
> +	PTR_L		a1, sp, PT_R5
> +	PTR_ADDI	sp, sp, PT_SIZE
>  
>  	jr		ra
>  SYM_CODE_END(return_to_handler)
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 0f3cd7c3a436..6e8422269ba4 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -140,7 +140,7 @@ config RISCV
>  	select HAVE_DYNAMIC_FTRACE_WITH_ARGS if HAVE_DYNAMIC_FTRACE
>  	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
>  	select HAVE_FUNCTION_GRAPH_TRACER
> -	select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
> +	select HAVE_FUNCTION_GRAPH_FREGS
>  	select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION
>  	select HAVE_EBPF_JIT if MMU
>  	select HAVE_GUP_FAST if MMU
> diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
> index 2cddd79ff21b..e9f364ce9fe8 100644
> --- a/arch/riscv/include/asm/ftrace.h
> +++ b/arch/riscv/include/asm/ftrace.h
> @@ -164,6 +164,11 @@ static __always_inline unsigned long ftrace_regs_get_stack_pointer(const struct
>  	return fregs->sp;
>  }
>  
> +static __always_inline unsigned long ftrace_regs_get_frame_pointer(const struct ftrace_regs *fregs)
> +{
> +	return fregs->s0;
> +}
> +
>  static __always_inline unsigned long ftrace_regs_get_argument(struct ftrace_regs *fregs,
>  							      unsigned int n)
>  {
> @@ -204,25 +209,4 @@ static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs, unsi
>  
>  #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 3a42f6287909..068168046e0e 100644
> --- a/arch/riscv/kernel/mcount.S
> +++ b/arch/riscv/kernel/mcount.S
> @@ -12,6 +12,8 @@
>  #include <asm/asm-offsets.h>
>  #include <asm/ftrace.h>
>  
> +#define ABI_SIZE_ON_STACK	80
> +
>  	.text
>  
>  	.macro SAVE_ABI_STATE
> @@ -26,12 +28,12 @@
>  	 * register if a0 was not saved.
>  	 */
>  	.macro SAVE_RET_ABI_STATE
> -	addi	sp, sp, -4*SZREG
> -	REG_S	s0, 2*SZREG(sp)
> -	REG_S	ra, 3*SZREG(sp)
> -	REG_S	a0, 1*SZREG(sp)
> -	REG_S	a1, 0*SZREG(sp)
> -	addi	s0, sp, 4*SZREG
> +	addi	sp, sp, -ABI_SIZE_ON_STACK
> +	REG_S	ra, 1*SZREG(sp)
> +	REG_S	s0, 8*SZREG(sp)
> +	REG_S	a0, 10*SZREG(sp)
> +	REG_S	a1, 11*SZREG(sp)
> +	addi	s0, sp, ABI_SIZE_ON_STACK
>  	.endm
>  
>  	.macro RESTORE_ABI_STATE
> @@ -41,11 +43,11 @@
>  	.endm
>  
>  	.macro RESTORE_RET_ABI_STATE
> -	REG_L	ra, 3*SZREG(sp)
> -	REG_L	s0, 2*SZREG(sp)
> -	REG_L	a0, 1*SZREG(sp)
> -	REG_L	a1, 0*SZREG(sp)
> -	addi	sp, sp, 4*SZREG
> +	REG_L	ra, 1*SZREG(sp)
> +	REG_L	s0, 8*SZREG(sp)
> +	REG_L	a0, 10*SZREG(sp)
> +	REG_L	a1, 11*SZREG(sp)
> +	addi	sp, sp, ABI_SIZE_ON_STACK
>  	.endm
>  
>  SYM_TYPED_FUNC_START(ftrace_stub)
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index a822f952f64a..12e942cfbcde 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -184,7 +184,7 @@ 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 de76c21eb4a3..9cdd48a46bf7 100644
> --- a/arch/s390/include/asm/ftrace.h
> +++ b/arch/s390/include/asm/ftrace.h
> @@ -49,23 +49,6 @@ 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 unsigned long
>  ftrace_regs_get_instruction_pointer(const struct ftrace_regs *fregs)
>  {
> @@ -92,6 +75,15 @@ ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs,
>  #define ftrace_regs_query_register_offset(name) \
>  	regs_query_register_offset(name)
>  
> +static __always_inline unsigned long
> +ftrace_regs_get_frame_pointer(struct ftrace_regs *fregs)
> +{
> +	unsigned long *sp;
> +
> +	sp = (void *)ftrace_regs_get_stack_pointer(fregs);
> +	return sp[0];	/* return backchain */
> +}
> +
>  #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 ffa0dd2dbaac..d38ed80615d5 100644
> --- a/arch/s390/kernel/asm-offsets.c
> +++ b/arch/s390/kernel/asm-offsets.c
> @@ -179,12 +179,6 @@ 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, ftrace_regs, regs);
>  	DEFINE(__FTRACE_REGS_SIZE, sizeof(struct ftrace_regs));
>  
> diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
> index ae4d4fd9afcd..cda798b976de 100644
> --- a/arch/s390/kernel/mcount.S
> +++ b/arch/s390/kernel/mcount.S
> @@ -133,14 +133,15 @@ 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 + backchain on the stack
> +	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)
> +	stg	%r2,(__SF_GPRS+2*8)(%r15)
> +	stg	%r15,(__SF_GPRS+15*8)(%r15)
>  	lgr	%r2,%r3
>  	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
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 007bab9f2a0e..047384e4d93a 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -228,7 +228,7 @@ config X86
>  	select HAVE_GUP_FAST
>  	select HAVE_FENTRY			if X86_64 || DYNAMIC_FTRACE
>  	select HAVE_FTRACE_MCOUNT_RECORD
> -	select HAVE_FUNCTION_GRAPH_RETVAL	if HAVE_FUNCTION_GRAPH_TRACER
> +	select HAVE_FUNCTION_GRAPH_FREGS	if HAVE_FUNCTION_GRAPH_TRACER
>  	select HAVE_FUNCTION_GRAPH_TRACER	if X86_32 || (X86_64 && DYNAMIC_FTRACE)
>  	select HAVE_FUNCTION_TRACER
>  	select HAVE_GCC_PLUGINS
> diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
> index 78f6a200e15b..669771ef3b5b 100644
> --- a/arch/x86/include/asm/ftrace.h
> +++ b/arch/x86/include/asm/ftrace.h
> @@ -64,6 +64,8 @@ arch_ftrace_get_regs(struct ftrace_regs *fregs)
>  	override_function_with_return(&(fregs)->regs)
>  #define ftrace_regs_query_register_offset(name) \
>  	regs_query_register_offset(name)
> +#define ftrace_regs_get_frame_pointer(fregs) \
> +	frame_pointer(&(fregs)->regs)
>  
>  struct ftrace_ops;
>  #define ftrace_graph_func ftrace_graph_func
> @@ -148,24 +150,4 @@ static inline bool arch_trace_is_compat_syscall(struct pt_regs *regs)
>  #endif /* !COMPILE_OFFSETS */
>  #endif /* !__ASSEMBLY__ */
>  
> -#ifndef __ASSEMBLY__
> -#ifdef CONFIG_FUNCTION_GRAPH_TRACER
> -struct fgraph_ret_regs {
> -	unsigned long ax;
> -	unsigned long dx;
> -	unsigned long bp;
> -};
> -
> -static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
> -{
> -	return ret_regs->ax;
> -}
> -
> -static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
> -{
> -	return ret_regs->bp;
> -}
> -#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
> -#endif
> -
>  #endif /* _ASM_X86_FTRACE_H */
> diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S
> index 58d9ed50fe61..4b265884d06c 100644
> --- a/arch/x86/kernel/ftrace_32.S
> +++ b/arch/x86/kernel/ftrace_32.S
> @@ -23,6 +23,8 @@ SYM_FUNC_START(__fentry__)
>  SYM_FUNC_END(__fentry__)
>  EXPORT_SYMBOL(__fentry__)
>  
> +#define FRAME_SIZE	PT_OLDSS+4
> +
>  SYM_CODE_START(ftrace_caller)
>  
>  #ifdef CONFIG_FRAME_POINTER
> @@ -187,14 +189,15 @@ SYM_CODE_END(ftrace_graph_caller)
>  
>  .globl return_to_handler
>  return_to_handler:
> -	pushl	$0
> -	pushl	%edx
> -	pushl	%eax
> +	subl	$(FRAME_SIZE), %esp
> +	movl	$0, PT_EBP(%esp)
> +	movl	%edx, PT_EDX(%esp)
> +	movl	%eax, PT_EAX(%esp)
>  	movl	%esp, %eax
>  	call	ftrace_return_to_handler
>  	movl	%eax, %ecx
> -	popl	%eax
> -	popl	%edx
> -	addl	$4, %esp		# skip ebp
> +	movl	%eax, PT_EAX(%esp)
> +	movl	%edx, PT_EDX(%esp)
> +	addl	$(FRAME_SIZE), %esp
>  	JMP_NOSPEC ecx
>  #endif
> diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
> index 214f30e9f0c0..d51647228596 100644
> --- a/arch/x86/kernel/ftrace_64.S
> +++ b/arch/x86/kernel/ftrace_64.S
> @@ -348,21 +348,22 @@ STACK_FRAME_NON_STANDARD_FP(__fentry__)
>  SYM_CODE_START(return_to_handler)
>  	UNWIND_HINT_UNDEFINED
>  	ANNOTATE_NOENDBR
> -	subq  $24, %rsp
>  
> -	/* Save the return values */
> -	movq %rax, (%rsp)
> -	movq %rdx, 8(%rsp)
> -	movq %rbp, 16(%rsp)
> +	/* Save ftrace_regs for function exit context  */
> +	subq $(FRAME_SIZE), %rsp
> +
> +	movq %rax, RAX(%rsp)
> +	movq %rdx, RDX(%rsp)
> +	movq %rbp, RBP(%rsp)
>  	movq %rsp, %rdi
>  
>  	call ftrace_return_to_handler
>  
>  	movq %rax, %rdi
> -	movq 8(%rsp), %rdx
> -	movq (%rsp), %rax
> +	movq RDX(%rsp), %rdx
> +	movq RAX(%rsp), %rax
>  
> -	addq $24, %rsp
> +	addq $(FRAME_SIZE), %rsp
>  	/*
>  	 * Jump back to the old return address. This cannot be JMP_NOSPEC rdi
>  	 * since IBT would demand that contain ENDBR, which simply isn't so for
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 1fe49a28de2d..13987cd63553 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -43,9 +43,8 @@ struct dyn_ftrace;
>  
>  char *arch_ftrace_match_adjust(char *str, const char *search);
>  
> -#ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> -struct fgraph_ret_regs;
> -unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs);
> +#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FREGS
> +unsigned long ftrace_return_to_handler(struct ftrace_regs *fregs);
>  #else
>  unsigned long ftrace_return_to_handler(unsigned long frame_pointer);
>  #endif
> @@ -134,6 +133,13 @@ extern int ftrace_enabled;
>   * Also, architecture dependent fields can be used for internal process.
>   * (e.g. orig_ax on x86_64)
>   *
> + * Basically, ftrace_regs stores the registers related to the context.
> + * On function entry, registers for function parameters and hooking the
> + * function call are stored, and on function exit, registers for function
> + * return value and frame pointers are stored.
> + *
> + * And also, it dpends on the context that which registers are restored
> + * from the ftrace_regs.
>   * On the function entry, those registers will be restored except for
>   * the stack pointer, so that user can change the function parameters
>   * and instruction pointer (e.g. live patching.)
> @@ -191,6 +197,8 @@ static __always_inline bool ftrace_regs_has_args(struct ftrace_regs *fregs)
>  	override_function_with_return(ftrace_get_regs(fregs))
>  #define ftrace_regs_query_register_offset(name) \
>  	regs_query_register_offset(name)
> +#define ftrace_regs_get_frame_pointer(fregs) \
> +	frame_pointer(&(fregs)->regs)
>  #endif
>  
>  typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip,
> diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
> index 721c3b221048..ab277eff80dc 100644
> --- a/kernel/trace/Kconfig
> +++ b/kernel/trace/Kconfig
> @@ -31,7 +31,7 @@ config HAVE_FUNCTION_GRAPH_TRACER
>  	help
>  	  See Documentation/trace/ftrace-design.rst
>  
> -config HAVE_FUNCTION_GRAPH_RETVAL
> +config HAVE_FUNCTION_GRAPH_FREGS
>  	bool
>  
>  config HAVE_DYNAMIC_FTRACE
> @@ -232,7 +232,7 @@ config FUNCTION_GRAPH_TRACER
>  
>  config FUNCTION_GRAPH_RETVAL
>  	bool "Kernel Function Graph Return Value"
> -	depends on HAVE_FUNCTION_GRAPH_RETVAL
> +	depends on HAVE_FUNCTION_GRAPH_FREGS
>  	depends on FUNCTION_GRAPH_TRACER
>  	default n
>  	help
> diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
> index 0322c5723748..30bebe43607d 100644
> --- a/kernel/trace/fgraph.c
> +++ b/kernel/trace/fgraph.c
> @@ -763,15 +763,12 @@ static struct notifier_block ftrace_suspend_notifier = {
>  	.notifier_call = ftrace_suspend_notifier_call,
>  };
>  
> -/* fgraph_ret_regs is not defined without CONFIG_FUNCTION_GRAPH_RETVAL */
> -struct fgraph_ret_regs;
> -
>  /*
>   * Send the trace to the ring-buffer.
>   * @return the original return address.
>   */
> -static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs,
> -						unsigned long frame_pointer)
> +static inline unsigned long
> +__ftrace_return_to_handler(struct ftrace_regs *fregs, unsigned long frame_pointer)
>  {
>  	struct ftrace_ret_stack *ret_stack;
>  	struct ftrace_graph_ret trace;
> @@ -791,7 +788,7 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
>  
>  	trace.rettime = trace_clock_local();
>  #ifdef CONFIG_FUNCTION_GRAPH_RETVAL
> -	trace.retval = fgraph_ret_regs_return_value(ret_regs);
> +	trace.retval = ftrace_regs_get_return_value(fregs);
>  #endif
>  
>  	bitmap = get_bitmap_bits(current, offset);
> @@ -826,14 +823,14 @@ static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs
>  }
>  
>  /*
> - * After all architecures have selected HAVE_FUNCTION_GRAPH_RETVAL, we can
> - * leave only ftrace_return_to_handler(ret_regs).
> + * After all architecures have selected HAVE_FUNCTION_GRAPH_FREGS, we can
> + * leave only ftrace_return_to_handler(fregs).
>   */
> -#ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> -unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs)
> +#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FREGS
> +unsigned long ftrace_return_to_handler(struct ftrace_regs *fregs)
>  {
> -	return __ftrace_return_to_handler(ret_regs,
> -				fgraph_ret_regs_frame_pointer(ret_regs));
> +	return __ftrace_return_to_handler(fregs,
> +				ftrace_regs_get_frame_pointer(fregs));
>  }
>  #else
>  unsigned long ftrace_return_to_handler(unsigned long frame_pointer)