[PATCH] riscv: tracing: Fix __write_overflow_field in ftrace_partial_regs()

[Alexandre Ghiti]

Hi Charlie,

On 25/02/2025 18:53, Charlie Jenkins wrote:
> On Tue, Feb 25, 2025 at 09:36:04AM +0100, Alexandre Ghiti wrote:
>> Hi Charlie,
>>
>> On 25/02/2025 03:42, Charlie Jenkins wrote:
>>> The size of &regs->a0 is unknown, causing the error:
>>>
>>> ../include/linux/fortify-string.h:571:25: warning: call to
>>> '__write_overflow_field' declared with attribute warning: detected write
>>> beyond size of field (1st parameter); maybe use struct_group()?
>>> [-Wattribute-warning]
>>
>> I can't reproduce this warning with gcc and llvm, even when setting by hand
>> -Wattribute-warning when compiling bpf_trace.c (which is the user of
>> ftrace_partial_regs()).
>>
>> Which toolchain did you use?
> You need to have the configs:
> CONFIG_BPF_SYSCALL=y
> CONFIG_FORTIFY_SOURCE=y
> CONFIG_FUNCTION_TRACER=y
> CONFIG_FPROBE=y
> CONFIG_DYNAMIC_FTRACE=y
>
> I used gcc 14.2.0


I was missing FPROBE!

Reviewed-by: Alexandre Ghiti <alexghiti at rivosinc.com>

Tested-by: Alexandre Ghiti <alexghiti at rivosinc.com>

Thanks,

Alex


>
> - Charlie
>
>> Thanks,
>>
>> Alex
>>
>>
>>> Fix this by wrapping the required registers in pt_regs with
>>> struct_group() and reference the group when doing the offending
>>> memcpy().
>>>
>>> Signed-off-by: Charlie Jenkins <charlie at rivosinc.com>
>>> ---
>>>    arch/riscv/include/asm/ftrace.h |  2 +-
>>>    arch/riscv/include/asm/ptrace.h | 18 ++++++++++--------
>>>    2 files changed, 11 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
>>> index c4721ce44ca474654b37b3d51bc0a63d46bc1eff..ec6db1162021fbf4fa48fc87e7984266040aa7d9 100644
>>> --- a/arch/riscv/include/asm/ftrace.h
>>> +++ b/arch/riscv/include/asm/ftrace.h
>>> @@ -207,7 +207,7 @@ ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
>>>    {
>>>    	struct __arch_ftrace_regs *afregs = arch_ftrace_regs(fregs);
>>> -	memcpy(&regs->a0, afregs->args, sizeof(afregs->args));
>>> +	memcpy(&regs->a_regs, afregs->args, sizeof(afregs->args));
>>>    	regs->epc = afregs->epc;
>>>    	regs->ra = afregs->ra;
>>>    	regs->sp = afregs->sp;
>>> diff --git a/arch/riscv/include/asm/ptrace.h b/arch/riscv/include/asm/ptrace.h
>>> index b5b0adcc85c18e15c156de11172a5d7f03ada037..2910231977cb71dac3cc42f2dc32590284204057 100644
>>> --- a/arch/riscv/include/asm/ptrace.h
>>> +++ b/arch/riscv/include/asm/ptrace.h
>>> @@ -23,14 +23,16 @@ struct pt_regs {
>>>    	unsigned long t2;
>>>    	unsigned long s0;
>>>    	unsigned long s1;
>>> -	unsigned long a0;
>>> -	unsigned long a1;
>>> -	unsigned long a2;
>>> -	unsigned long a3;
>>> -	unsigned long a4;
>>> -	unsigned long a5;
>>> -	unsigned long a6;
>>> -	unsigned long a7;
>>> +	struct_group(a_regs,
>>> +		unsigned long a0;
>>> +		unsigned long a1;
>>> +		unsigned long a2;
>>> +		unsigned long a3;
>>> +		unsigned long a4;
>>> +		unsigned long a5;
>>> +		unsigned long a6;
>>> +		unsigned long a7;
>>> +	);
>>>    	unsigned long s2;
>>>    	unsigned long s3;
>>>    	unsigned long s4;
>>>
>>> ---
>>> base-commit: d082ecbc71e9e0bf49883ee4afd435a77a5101b6
>>> change-id: 20250224-fix_ftrace_partial_regs-eddaf4a7e5ed
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