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Message-ID: <ZCqKoPrqoKwSVsY7@FVFF77S0Q05N>
Date: Mon, 3 Apr 2023 09:13:20 +0100
From: Mark Rutland <mark.rutland@....com>
To: Donglin Peng <pengdonglin@...gfor.com.cn>
Cc: mhiramat@...nel.org, rostedt@...dmis.org, linux@...linux.org.uk,
will@...nel.org, catalin.marinas@....com,
rmk+kernel@...linux.org.uk, palmer@...belt.com,
paul.walmsley@...ive.com, aou@...s.berkeley.edu,
tglx@...utronix.de, dave.hansen@...ux.intel.com, x86@...nel.org,
bp@...en8.de, hpa@...or.com, chenhuacai@...nel.org,
zhangqing@...ngson.cn, kernel@...0n.name, mingo@...hat.com,
peterz@...radead.org, xiehuan09@...il.com, dinghui@...gfor.com.cn,
huangcun@...gfor.com.cn, dolinux.peng@...il.com,
linux-trace-kernel@...r.kernel.org, loongarch@...ts.linux.dev,
linux-riscv@...ts.infradead.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 4/8] arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
On Fri, Mar 31, 2023 at 05:47:40AM -0700, Donglin Peng 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 ARM64 platform.
>
> We introduce a new structure called fgraph_ret_regs for the ARM64
> 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@...gfor.com.cn>
Thanks for working through all the feedback!
The structual changes all look good to me, and I've given this a spin to check
that it doesn't break graph tracing, so:
Reviewed-by: Mark Rutland <mark.rutland@....com>
Tested-by: Mark Rutland <mark.rutland@....com>
Mark.
> ---
> v10:
> - Use CONFIG_FUNCTION_GRAPH_TRACER to control fgraph_ret_regs definition
>
> v9:
> - Update the commit message
>
> v8:
> - Fix issues in ARM64 asm code
> - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/ftrace.h | 22 ++++++++++++++++++++++
> arch/arm64/kernel/asm-offsets.c | 13 +++++++++++++
> arch/arm64/kernel/entry-ftrace.S | 27 ++++++++++++++-------------
> 4 files changed, 50 insertions(+), 13 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 1023e896d46b..48856d230800 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -195,6 +195,7 @@ config ARM64
> select HAVE_FTRACE_MCOUNT_RECORD
> select HAVE_FUNCTION_TRACER
> select HAVE_FUNCTION_ERROR_INJECTION
> + select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
> select HAVE_FUNCTION_GRAPH_TRACER
> select HAVE_GCC_PLUGINS
> select HAVE_HW_BREAKPOINT if PERF_EVENTS
> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
> index 1c2672bbbf37..657adcbd80a4 100644
> --- a/arch/arm64/include/asm/ftrace.h
> +++ b/arch/arm64/include/asm/ftrace.h
> @@ -170,4 +170,26 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
> }
> #endif /* ifndef __ASSEMBLY__ */
>
> +#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;
> +}
> +#endif /* ifdef CONFIG_FUNCTION_GRAPH_TRACER */
> +#endif
> +
> #endif /* __ASM_FTRACE_H */
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index ae345b06e9f7..75082e0409bf 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -197,6 +197,19 @@ int main(void)
> #endif
> #ifdef CONFIG_FUNCTION_TRACER
> 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
> return 0;
> }
> diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
> index 350ed81324ac..da1443bcf776 100644
> --- a/arch/arm64/kernel/entry-ftrace.S
> +++ b/arch/arm64/kernel/entry-ftrace.S
> @@ -270,22 +270,23 @@ SYM_FUNC_END(ftrace_stub_graph)
> */
> SYM_CODE_START(return_to_handler)
> /* save return value regs */
> - sub sp, sp, #64
> - stp x0, x1, [sp]
> - stp x2, x3, [sp, #16]
> - stp x4, x5, [sp, #32]
> - stp x6, x7, [sp, #48]
> + 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
>
> - mov x0, x29 // parent's fp
> - bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);
> - mov x30, x0 // restore the original return address
> + mov x0, sp
> + bl ftrace_return_to_handler // addr = ftrace_return_to_hander(regs);
> + mov x30, x0 // restore the original return address
>
> /* restore return value regs */
> - ldp x0, x1, [sp]
> - ldp x2, x3, [sp, #16]
> - ldp x4, x5, [sp, #32]
> - ldp x6, x7, [sp, #48]
> - add sp, sp, #64
> + 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
>
> ret
> SYM_CODE_END(return_to_handler)
> --
> 2.25.1
>
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