[PATCH v7 07/14] rtld: Clean up PT_NOTE and add PT_GNU_PROPERTY handling

[H.J. Lu]

On Wed, Jul 8, 2020 at 5:14 AM Szabolcs Nagy <szabolcs.nagy@arm.com> wrote:
>
> Add generic code to handle PT_GNU_PROPERTY notes. Invalid
> content is ignored, _dl_process_pt_gnu_property is always called
> after PT_LOAD segments are mapped and it has no failure modes.
> Currently only one NT_GNU_PROPERTY_TYPE_0 note is handled, which
> contains target specific properties: the _dl_process_gnu_property
> hook is called for each property.
>
> The old _dl_process_pt_note and _rtld_process_pt_note differ in how
> the program header is read.  The old _dl_process_pt_note is called
> before PT_LOAD segments are mapped and _rtld_process_pt_note is called
> after PT_LOAD segments are mapped. The old _rtld_process_pt_note is
> removed and _dl_process_pt_note is always called after PT_LOAD
> segments are mapped and now it has no failure modes.
>
> The program headers are scanned backwards so that PT_NOTE can be
> skipped if PT_GNU_PROPERTY exists.
>
> Co-Authored-By: H.J. Lu <hjl.tools@gmail.com>
> Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

The previous patch:

https://sourceware.org/pipermail/libc-alpha/2020-July/115636.html

has been acked by

https://sourceware.org/pipermail/libc-alpha/2020-July/115831.html


>  elf/dl-load.c              | 94 ++++++++++++++++++++++++++++++++++----
>  elf/rtld.c                 | 14 ++++--
>  sysdeps/generic/dl-prop.h  | 23 +++++-----
>  sysdeps/generic/ldsodefs.h |  4 ++
>  sysdeps/x86/dl-prop.h      | 47 +++----------------
>  5 files changed, 118 insertions(+), 64 deletions(-)
>
> diff --git a/elf/dl-load.c b/elf/dl-load.c
> index 06f2ba7264..e39980fb19 100644
> --- a/elf/dl-load.c
> +++ b/elf/dl-load.c
> @@ -853,6 +853,77 @@ lose (int code, int fd, const char *name, char *realname, struct link_map *l,
>  }
>
>
> +/* Process PT_GNU_PROPERTY program header PH in module L after
> +   PT_LOAD segments are mapped.  Only one NT_GNU_PROPERTY_TYPE_0
> +   note is handled which contains processor specific properties.  */
> +
> +void
> +_dl_process_pt_gnu_property (struct link_map *l, const ElfW(Phdr) *ph)
> +{
> +  const ElfW(Nhdr) *note = (const void *) (ph->p_vaddr + l->l_addr);
> +  const ElfW(Addr) size = ph->p_memsz;
> +  const ElfW(Addr) align = ph->p_align;
> +
> +  /* The NT_GNU_PROPERTY_TYPE_0 note must be aligned to 4 bytes in
> +     32-bit objects and to 8 bytes in 64-bit objects.  Skip notes
> +     with incorrect alignment.  */
> +  if (align != (__ELF_NATIVE_CLASS / 8))
> +    return;
> +
> +  const ElfW(Addr) start = (ElfW(Addr)) note;
> +  unsigned int last_type = 0;
> +
> +  while ((ElfW(Addr)) (note + 1) - start < size)
> +    {
> +      /* Find the NT_GNU_PROPERTY_TYPE_0 note.  */
> +      if (note->n_namesz == 4
> +         && note->n_type == NT_GNU_PROPERTY_TYPE_0
> +         && memcmp (note + 1, "GNU", 4) == 0)
> +       {
> +         /* Check for invalid property.  */
> +         if (note->n_descsz < 8
> +             || (note->n_descsz % sizeof (ElfW(Addr))) != 0)
> +           return;
> +
> +         /* Start and end of property array.  */
> +         unsigned char *ptr = (unsigned char *) (note + 1) + 4;
> +         unsigned char *ptr_end = ptr + note->n_descsz;
> +
> +         do
> +           {
> +             unsigned int type = *(unsigned int *) ptr;
> +             unsigned int datasz = *(unsigned int *) (ptr + 4);
> +
> +             /* Property type must be in ascending order.  */
> +             if (type < last_type)
> +               return;
> +
> +             ptr += 8;
> +             if ((ptr + datasz) > ptr_end)
> +               return;
> +
> +             last_type = type;
> +
> +             /* Target specific property processing.  */
> +             if (_dl_process_gnu_property (l, type, datasz, ptr) == 0)
> +               return;
> +

A space is added.

Does this patch require other patches? If not, it can go in now.

Thanks.

-- 
H.J.