[PATCH v11 5/8] riscv: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL

[Palmer Dabbelt]

On Thu, 08 Jun 2023 18:58:34 PDT (-0700), rostedt at goodmis.org wrote:
>
> Can I get an ack from a RISC-V maintainer?

Sorry I missed this.

Acked-by: Palmer Dabbelt <palmer at rivosinc.com>

>
> -- Steve
>
>
> On Sat,  8 Apr 2023 05:42:19 -0700
> Donglin Peng <pengdonglin at 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 at 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