Re: [PATCH v2 4/6] elf: Move note processing after l_phdr is updated

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 27/11/2020 10:20, Szabolcs Nagy via Libc-alpha wrote:
> Program headers are processed in two pass: after the first pass
> load segments are mmapped so in the second pass target specific
> note processing logic can access the notes.
> 
> The second pass is moved later so various link_map fields are
> set up that may be useful for note processing such as l_phdr.
> The second pass should be before the fd is closed so that is
> available.

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  elf/dl-load.c | 30 +++++++++++++++---------------
>  1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/elf/dl-load.c b/elf/dl-load.c
> index 9c71b7562c..b0d65f32cc 100644
> --- a/elf/dl-load.c
> +++ b/elf/dl-load.c
> @@ -1268,21 +1268,6 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
>  	l->l_map_start = l->l_map_end = 0;
>  	goto call_lose;
>        }
> -
> -    /* Process program headers again after load segments are mapped in
> -       case processing requires accessing those segments.  Scan program
> -       headers backward so that PT_NOTE can be skipped if PT_GNU_PROPERTY
> -       exits.  */
> -    for (ph = &phdr[l->l_phnum]; ph != phdr; --ph)
> -      switch (ph[-1].p_type)
> -	{
> -	case PT_NOTE:
> -	  _dl_process_pt_note (l, &ph[-1]);
> -	  break;
> -	case PT_GNU_PROPERTY:
> -	  _dl_process_pt_gnu_property (l, &ph[-1]);
> -	  break;
> -	}
>    }
>  
>    if (l->l_ld == 0)
> @@ -1386,6 +1371,21 @@ cannot enable executable stack as shared object requires");
>    if (l->l_tls_initimage != NULL)
>      l->l_tls_initimage = (char *) l->l_tls_initimage + l->l_addr;
>  
> +  /* Process program headers again after load segments are mapped in
> +     case processing requires accessing those segments.  Scan program
> +     headers backward so that PT_NOTE can be skipped if PT_GNU_PROPERTY
> +     exits.  */
> +  for (ph = &l->l_phdr[l->l_phnum]; ph != l->l_phdr; --ph)
> +    switch (ph[-1].p_type)
> +      {
> +      case PT_NOTE:
> +	_dl_process_pt_note (l, &ph[-1]);
> +	break;
> +      case PT_GNU_PROPERTY:
> +	_dl_process_pt_gnu_property (l, &ph[-1]);
> +	break;
> +      }
> +
>    /* We are done mapping in the file.  We no longer need the descriptor.  */
>    if (__glibc_unlikely (__close_nocancel (fd) != 0))
>      {
>