[RFC 1/5] elf: Add SFrame support to _dl_find_object function

[Claudiu Zissulescu-Ianculescu]

Hi Florian,


On 3/20/25 10:03 AM, Florian Weimer wrote:
> * claudiu zissulescu-ianculescu:
> 
>> diff --git a/bits/dl_find_object.h b/bits/dl_find_object.h
>> index b9f796dc2b..162ef00615 100644
>> --- a/bits/dl_find_object.h
>> +++ b/bits/dl_find_object.h
>> @@ -30,3 +30,9 @@
>>  
>>  /* The ELF segment which contains the exception handling data.  */
>>  #define DLFO_EH_SEGMENT_TYPE PT_GNU_EH_FRAME
>> +
>> +/* The ELF segment which contains the SFrame data.  */
>> +#define DLFO_SFRAME_SEGMENT_TYPE PT_GNU_SFRAME
>> +
>> +/* This implementation does not have SFrame data.  */
>> +#define DLFO_STRUCT_HAS_SFRAME 0
> 
> Is there any technical reason why an architecture would not add SFrame
> data?

Not really, unless the maintainers of an architecture don't want to deal
with SFrame.

> 
> I think we shoul define this unconditionally …
> 
>> diff --git a/dlfcn/dlfcn.h b/dlfcn/dlfcn.h
>> index 5747962611..dd4113a757 100644
>> --- a/dlfcn/dlfcn.h
>> +++ b/dlfcn/dlfcn.h
>> @@ -216,6 +216,9 @@ struct dl_find_object
>>  # if DLFO_STRUCT_HAS_EH_COUNT
>>    int dlfo_eh_count;		/* Number of exception handling entries.  */
>>    unsigned int __dlfo_eh_count_pad;
>> +# endif
>> +# if DLFO_STRUCT_HAS_SFRAME
>> +  void *dlfo_sframe;		/* SFrame stack trace data of the object.  */
>>  # endif
>>    __extension__ unsigned long long int __dflo_reserved[7];
>>  };
> 
> … and always define this field.
> 
>> diff --git a/elf/dl-find_object.h b/elf/dl-find_object.h
>> index 0915065be0..e43c3212c2 100644
>> --- a/elf/dl-find_object.h
>> +++ b/elf/dl-find_object.h
>> @@ -43,6 +43,9 @@ struct dl_find_object_internal
>>  #if DLFO_STRUCT_HAS_EH_COUNT
>>    int eh_count;
>>  #endif
>> +#if DLFO_STRUCT_HAS_SFRAME
>> +  void *sframe;
>> +#endif
>>  };
> 
> And here.
> 
> You need to add a flag to dlfo_flags that indicates that the dlfo_sframe
> field is valid.
> 

Thank you for the input. I'll address all of them in my second round,
Claudiu