Re: [PATCH] btf_encoder: Add extra checks for symbol names

[Tom Stellard <tstellar@redhat.com>]

On 1/21/21 5:38 AM, Arnaldo Carvalho de Melo wrote:
> Em Tue, Jan 12, 2021 at 04:27:59PM -0800, Tom Stellard escreveu:
>> On 1/12/21 10:40 AM, Jiri Olsa wrote:
>>> When processing kernel image build by clang we can
>>> find some functions without the name, which causes
>>> pahole to segfault.
>>>
>>> Adding extra checks to make sure we always have
>>> function's name defined before using it.
>>>
>>
>> I backported this patch to pahole 1.19, and I can confirm it fixes the
>> segfault for me.
> 
> I'm applying v2 for this patch and based on your above statement I'm
> adding a:
> 
> Tested-by: Tom Stellard <tstellar@redhat.com>
> 
> Ok?
> 

Yes, this is fine.  I also backported the v2 patch and tested it and it
fixed the issue.

-Tom

> Who originally reported this?
> 
> - Arnaldo
>   
>> -Tom
>>
>>> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
>>> ---
>>>    btf_encoder.c | 8 ++++++--
>>>    1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/btf_encoder.c b/btf_encoder.c
>>> index 333973054b61..17f7a14f2ef0 100644
>>> --- a/btf_encoder.c
>>> +++ b/btf_encoder.c
>>> @@ -72,6 +72,8 @@ static int collect_function(struct btf_elf *btfe, GElf_Sym *sym)
>>>    	if (elf_sym__type(sym) != STT_FUNC)
>>>    		return 0;
>>> +	if (!elf_sym__name(sym, btfe->symtab))
>>> +		return 0;
>>>    	if (functions_cnt == functions_alloc) {
>>>    		functions_alloc = max(1000, functions_alloc * 3 / 2);
>>> @@ -730,9 +732,11 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force,
>>>    		if (!has_arg_names(cu, &fn->proto))
>>>    			continue;
>>>    		if (functions_cnt) {
>>> -			struct elf_function *func;
>>> +			const char *name = function__name(fn, cu);
>>> +			struct elf_function *func = NULL;
>>> -			func = find_function(btfe, function__name(fn, cu));
>>> +			if (name)
>>> +				func = find_function(btfe, name);
>>>    			if (!func || func->generated)
>>>    				continue;
>>>    			func->generated = true;
>>>
>>
>