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

[Florian Weimer <fweimer at redhat dot com>]

On 08/16/2018 01:39 PM, H.J. Lu wrote:

> Please show the output of "readelf -n".  I believe that all
> NT_GNU_PROPERTY_TYPE_0
> notes are in a single PT_NOTE segment.

There is just one property note because the linker has property note 
merging support:

Displaying notes found in: .note.ABI-tag
  Owner                 Data size       Description
  GNU                  0x00000010       NT_GNU_ABI_TAG (ABI version tag)
    OS: Linux, ABI: 3.2.0

Displaying notes found in: .note.gnu.property
  Owner                 Data size       Description
  GNU                  0x00000020       NT_GNU_PROPERTY_TYPE_0
      Properties: x86 ISA used:
        x86 ISA needed:

Displaying notes found in: .note.gnu.build-id
  Owner                 Data size       Description
  GNU                  0x00000014       NT_GNU_BUILD_ID (unique build 
ID bitstring)
    Build ID: 5bd43ed7376c4734e49138a6bddb15dc0d0002a6

> My patch checks each PT_LOAD segment
> until a NT_GNU_PROPERTY_TYPE_0 note is found.  If more than one note is found,
> it disables CET since the binary was created by the older linker.

I assumed the patch stopped searching once it finds a segment with a 
single NT_GNU_PROPERTY_TYPE_0 note.  I'm still worried that this might 
be a problem, considering that ld produces multiple segments in some 
cases (but the triggering conditions for that aren't entirely clear to me).

Thanks,
Florian