Re: ELF's DT_ENCODING

[Fangrui Song <maskray@google.com>]

On Mon, May 22, 2023 at 1:03 AM Alan Modra <amodra@gmail.com> wrote:
>
> On Mon, May 22, 2023 at 08:57:00AM +0200, Jan Beulich wrote:
> > I think that part of the change wants reverting
>
> Yes, I think it was probably bumped without consulting the spec.  ;-)
> ie. it was changed just for readelf.  I'm going to commit the
> following after running my normal regression tests.
>
> include/
>         * elf/common.h (DT_ENCODING): Set back to 32.
> binutils/
>         * readelf.c (struct filedata): Don't size dynamic_info array
>         using DT_ENCODING.
>
> diff --git a/binutils/readelf.c b/binutils/readelf.c
> index b872876a8b6..d8ad58b15dc 100644
> --- a/binutils/readelf.c
> +++ b/binutils/readelf.c
> @@ -304,7 +304,7 @@ typedef struct filedata
>    uint64_t *           mipsxlat;
>    uint64_t             gnusymidx;
>    char *               program_interpreter;
> -  uint64_t             dynamic_info[DT_ENCODING];
> +  uint64_t             dynamic_info[DT_RELRENT + 1];
>    uint64_t             dynamic_info_DT_GNU_HASH;
>    uint64_t             dynamic_info_DT_MIPS_XHASH;
>    elf_section_list *   symtab_shndx_list;
> diff --git a/include/elf/common.h b/include/elf/common.h
> index 6f64f05890c..ffa6b60bd2b 100644
> --- a/include/elf/common.h
> +++ b/include/elf/common.h
> @@ -1135,13 +1135,16 @@
>  #define DT_FINI_ARRAYSZ 28
>  #define DT_RUNPATH     29
>  #define DT_FLAGS       30
> +
> +/* Values in the range [DT_ENCODING, DT_LOOS) use d_un.d_ptr if the
> +   value is even, d_un.d_val if odd.  */
> +#define DT_ENCODING    32
>  #define DT_PREINIT_ARRAY   32
>  #define DT_PREINIT_ARRAYSZ 33
>  #define DT_SYMTAB_SHNDX    34
>  #define DT_RELRSZ      35
>  #define DT_RELR                36
>  #define DT_RELRENT     37
> -#define DT_ENCODING    38
>
>  /* Note, the Oct 4, 1999 draft of the ELF ABI changed the values
>     for DT_LOOS and DT_HIOS.  Some implementations however, use
>
> --
> Alan Modra
> Australia Development Lab, IBM

Thanks to Jan for spotting my mistake and Alan for fixing the issue in
commit bc227f4ccb0778a56ca3d9f27652fd9e5e2747ea (Re: readelf: Support
SHT_RELR/DT_RELR for -r).
Apologies for not taking a closer look at the spec that DT_ENCODING is
defined, when that RELR patch was prepared.



-- 
宋方睿