Re: [PATCH v3 03/13] Rewrite abi-note.S in C.

[Florian Weimer via Libc-alpha <libc-alpha@sourceware.org>]

* Szabolcs Nagy:

> The 05/18/2020 17:28, Florian Weimer wrote:
>> * Szabolcs Nagy:
>> 
>> > +/* Note: Custom type is used as ElfW(Nhdr) is wrong on 64 bit targets.  */
>> 
>> Are you sure about that?
>> 
>> typedef struct
>> {
>>   Elf32_Word n_namesz;			/* Length of the note's name.  */
>>   Elf32_Word n_descsz;			/* Length of the note's descriptor.  */
>>   Elf32_Word n_type;			/* Type of the note.  */
>> } Elf32_Nhdr;
>> 
>> typedef struct
>> {
>>   Elf64_Word n_namesz;			/* Length of the note's name.  */
>>   Elf64_Word n_descsz;			/* Length of the note's descriptor.  */
>>   Elf64_Word n_type;			/* Type of the note.  */
>> } Elf64_Nhdr;
>> 
>> The types are the same:
>> 
>> typedef uint32_t Elf32_Word;
>> typedef uint32_t Elf64_Word;
>> 
>> I admit this is super-confusing.
>
> aah i missed this, then the struct can be
>
> #include <elf.h>
>
> __attribute__ ((used, aligned (4), section (".note.ABI-tag")))
> static const struct
> {
>   ElfW(Nhdr) nhdr;
>   char name[4];
>   int32_t desc[4];
> } __abi_tag = {
>   { .n_namesz = 4, .n_descsz = 16, .n_type = 1 },
>   "GNU",
>   { __ABI_TAG_OS, __ABI_TAG_VERSION }
> };
>
> i think the aligned attribute is still needed in case on
> some target uint32_t has smaller alignemnt than 4.

Agreed, I think it's needed for m68k.

> i can change this if it is considered to be better
> or just remove the incorrect comment.

I slightly prefer using the type from <elf.h>.

Thanks,
Florian