Re: [PATCH] Simplify note processing

["Dmitry V. Levin" <ldv at altlinux dot org>]

On Thu, Oct 10, 2019 at 12:26:37PM +0200, Andreas Schwab wrote:
> On Okt 10 2019, "Dmitry V. Levin" <ldv@altlinux.org> wrote:
> 
> > On Thu, Oct 10, 2019 at 10:48:29AM +0200, Andreas Schwab wrote:
> >> This removes dead code during note processing.
> >> 
> >> * elf/dl-load.c (open_verify): Remove dead code.
> >> ---
> >>  elf/dl-load.c | 17 +++--------------
> >>  1 file changed, 3 insertions(+), 14 deletions(-)
> >> 
> >> diff --git a/elf/dl-load.c b/elf/dl-load.c
> >> index 24e2819345..1ed7a7bbd6 100644
> >> --- a/elf/dl-load.c
> >> +++ b/elf/dl-load.c
> >> @@ -1682,21 +1682,10 @@ open_verify (const char *name, int fd,
> >>  
> >>        /* Check .note.ABI-tag if present.  */
> >>        for (ph = phdr; ph < &phdr[ehdr->e_phnum]; ++ph)
> >> -	if (ph->p_type == PT_NOTE && ph->p_filesz >= 32 && ph->p_align >= 4)
> >> +	if (ph->p_type == PT_NOTE && ph->p_filesz >= 32
> >> +	    && (ph->p_align == 4 || ph->p_align == 8))
> >>  	  {
> >>  	    ElfW(Addr) size = ph->p_filesz;
> >> -	    /* NB: Some PT_NOTE segment may have alignment value of 0
> >> -	       or 1.  gABI specifies that PT_NOTE segments should be
> >> -	       aligned to 4 bytes in 32-bit objects and to 8 bytes in
> >> -	       64-bit objects.  As a Linux extension, we also support
> >> -	       4 byte alignment in 64-bit objects.  If p_align is less
> >> -	       than 4, we treate alignment as 4 bytes since some note
> >> -	       segments have 0 or 1 byte alignment.   */
> >> -	    ElfW(Addr) align = ph->p_align;
> >> -	    if (align < 4)
> >> -	      align = 4;
> >> -	    else if (align != 4 && align != 8)
> >> -	      continue;
> >
> > This effectively removes support of ph->p_align < 4.
> 
> No.  It was never supported.  The condition ph->p_align >= 4 has been
> there from the beginning.

Indeed, and the "free (abi_note_malloced)" is actually outside the loop,
I must've completely misread the code, sorry for the noise.

The change is fine then.


-- 
ldv

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