Re: [PATCH v10 23/40] arm64/signal: Set up and restore the GCS context for signal handlers

On Wed, Aug 21, 2024 at 07:03:13PM +0100, Mark Brown wrote:

On Wed, Aug 21, 2024 at 06:28:49PM +0100, Catalin Marinas wrote:

...

On Thu, Aug 01, 2024 at 01:06:50PM +0100, Mark Brown wrote:

...

• /*

• * Push a cap and the GCS entry for the trampoline onto the GCS.
  

• */
  

• put_user_gcs((unsigned long)sigtramp, gcspr_el0 - 2, &ret);
• put_user_gcs(GCS_SIGNAL_CAP(gcspr_el0 - 1), gcspr_el0 - 1, &ret);
• if (ret != 0)

• return ret;
  

...

Doesn't the second put_user_gcs() override the previous ret?

No, we only set ret on error - if the first one faults it'll set ret then the second one will either leave it unchanged or write the same error code depending on if it fails. This idiom is used quite a lot in the signal code.

You are right, I missed that it's called 'err' in put_user_gcs(), thought it's overridden.