This is the mail archive of the mailing list for the glibc project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH] Check multiple NT_GNU_PROPERTY_TYPE_0 notes [BZ #23509]

On 08/15/2018 05:29 PM, H.J. Lu wrote:
On Wed, Aug 15, 2018 at 8:25 AM, Florian Weimer <> wrote:
On 08/15/2018 05:23 PM, H.J. Lu wrote:

On Wed, Aug 15, 2018 at 8:17 AM, Florian Weimer <>

On 08/14/2018 08:12 PM, H.J. Lu wrote:

_dl_process_cet_property_note is called on on each PT_NOTE segment.
We must keep searching until we found a PT_NOTE segment with a

     /* Skip if we have seen a NT_GNU_PROPERTY_TYPE_0 note before.  */
     if (l->l_cet != lc_unknown)

What if there are different segments, each one with its own
NT_GNU_PROPERTY_TYPE_0?  Wouldn't that point to lack of linker support,
So that CET needs to be disabled?

Older linkers puts all NT_GNU_PROPERTY_TYPE_0 notes in one section.  One can certainly create some random notes
which look like NT_GNU_PROPERTY_TYPE_0.  I don't think we need to
check these notes.

I think older BFD ld creates multiple segments.

Which version of ld dos that?

Examples that got me worried look like this:

$ readelf -l /usr/bin/b5i2iso
  NOTE           0x0000000000000334 0x0000000000400334 0x0000000000400334
                 0x0000000000000020 0x0000000000000020  R      0x4
  NOTE           0x0000000000000358 0x0000000000400358 0x0000000000400358
                 0x0000000000000030 0x0000000000000030  R      0x8
  NOTE           0x0000000000000388 0x0000000000400388 0x0000000000400388
                 0x0000000000000024 0x0000000000000024  R      0x4
   07     .note.ABI-tag
$ rpm -qf /usr/bin/b5i2iso

Per <>, this was built with binutils-2.30.90-4.fc29.

I don't know enough about the binutils linker to be certain that allocatable SHT_NOTE sections of the same name always go into the same PT_NOTE segment. In the example above, the sections weren't split.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]