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Message-ID: <115b1771-8204-749a-0a93-7835e74ea6ba@sangfor.com.cn>
Date: Wed, 29 Mar 2023 12:31:13 +0800
From: Donglin Peng <pengdonglin@...gfor.com.cn>
To: Qing Zhang <zhangqing@...ngson.cn>, mhiramat@...nel.org,
rostedt@...dmis.org, linux@...linux.org.uk, mark.rutland@....com,
will@...nel.org, catalin.marinas@....com, palmer@...belt.com,
paul.walmsley@...ive.com, tglx@...utronix.de,
dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
chenhuacai@...nel.org, kernel@...0n.name, mingo@...hat.com,
peterz@...radead.org, xiehuan09@...il.com, dinghui@...gfor.com.cn,
huangcun@...gfor.com.cn, dolinux.peng@...il.com
Cc: 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 v8 7/8] LoongArch: ftrace: Enable
HAVE_FUNCTION_GRAPH_RETVAL
On 2023/3/29 12:08, Qing Zhang wrote:
> Hi, Donglin
>
> On 2023/3/28 下午9:43, Donglin Peng wrote:
>> The commit d4815c5d1bbd ("function_graph: Support recording and
>> printing the return value of function") 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@...gfor.com.cn>
>> ---
>> v8:
>> - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
>> ---
>> arch/loongarch/Kconfig | 1 +
>> arch/loongarch/include/asm/ftrace.h | 18 ++++++++++++++++++
>> arch/loongarch/kernel/mcount.S | 6 ++++--
>> arch/loongarch/kernel/mcount_dyn.S | 7 ++++---
>> 4 files changed, 27 insertions(+), 5 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..433c6218888b 100644
>> --- a/arch/loongarch/include/asm/ftrace.h
>> +++ b/arch/loongarch/include/asm/ftrace.h
>> @@ -63,4 +63,22 @@ void ftrace_graph_func(unsigned long ip, unsigned
>> long parent_ip,
>> #endif /* CONFIG_FUNCTION_TRACER */
>> +#ifndef __ASSEMBLY__
>> +struct fgraph_ret_regs {
>> + unsigned long a0;
>> + unsigned long a1;
>> + unsigned long fp;
>> +};
>
> This overall looks good, but some places need attention:
>
> This will need to be padded to 16 bytes, as within the kernel,
> loongarch requires the SP to be aligned to 16 bytes at all time.
> Please can you add an `__unused/padding` field to ensure.
Thank you for pointing out this issue, and I will fix it.
>> +
>> +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->fp;
>> +}
>> +#endif
>> +
>> #endif /* _ASM_LOONGARCH_FTRACE_H */
>> diff --git a/arch/loongarch/kernel/mcount.S
>> b/arch/loongarch/kernel/mcount.S
>> index 8cdc1563cd33..3e405c0212c0 100644
>> --- a/arch/loongarch/kernel/mcount.S
>> +++ b/arch/loongarch/kernel/mcount.S
>> @@ -79,10 +79,12 @@ 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_ADDI sp, sp, -3 * SZREG
> As above, this will need to be padded to keep the stack aligned to 16
> bytes.
> PTR_ADDI sp, sp, -4 * SZREG
Thanks.
>
>> PTR_S a0, sp, 0
>> PTR_S a1, sp, SZREG
>> + PTR_S zero, sp, 2 * SZREG
>> + move a0, sp
>> bl ftrace_return_to_handler
>> /* Restore the real parent address: a0 -> ra */
>> @@ -90,7 +92,7 @@ SYM_FUNC_START(return_to_handler)
>> PTR_L a0, sp, 0
>> PTR_L a1, sp, SZREG
>> - PTR_ADDI sp, sp, 2 * SZREG
>> + PTR_ADDI sp, sp, 3 * SZREG
>> 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..ab85a953c6d3 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_ADDI sp, sp, -3 * SZREG
> as above.
Thanks.
>
> Thanks,
> - Qing
>> PTR_S a0, sp, 0
>> PTR_S a1, sp, SZREG
>> + PTR_S zero, sp, 2 * SZREG
>> - 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_ADDI sp, sp, 3 * SZREG
>> jr ra
>> SYM_CODE_END(return_to_handler)
>>
>
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