On Wed, Apr 28, 2021 at 12:21 PM Bill Wendling [off-list ref] wrote:

On Wed, Apr 28, 2021 at 10:40 AM Mark Brown [off-list ref] wrote:

quoted

On Wed, Apr 28, 2021 at 06:28:47PM +0100, Catalin Marinas wrote:

quoted

On Fri, Apr 23, 2021 at 01:51:59PM -0700, Bill Wendling wrote:

quoted

quoted

Since the note.gnu.property section in the vDSO is not checked by the
dynamic linker, discard the .note.gnu.property sections in the vDSO.

quoted

Can we not instead fix the linker script to preserve the
.note.gnu.property, correctly aligned? It doesn't take much space and
while we don't use it now, it has the BTI information about the binary.

quoted

Cc'ing a few others who were involved in the BTI support.

Not just BTI, we also flag PAC usage in there too and could add other
extensions going forwards.  While the note isn't actively used by
anything right now due to the kernel mapping the vDSO prior to userspace
starting it is part of the ABI and something could end up wanting to use
it and getting confused if it's not there.  It would be much better to
fix the alignment issue.

If there's only one of the 8-byte aligned sections guaranteed, we
could place it first in the note. Otherwise, we will have to change
the alignment of the note (or somehow merge multiple notes).

I should have clarified that there's only one *entry* in the
.note.gnu.properties section, and if not then is it possible to merge
multiple entries into one. (Excuse my ignorance if this is already the
case.)

-bw

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