aarch64: simplify calls to __libc_arm_za_disable in assembly

There is no functional change in this patch.

We remove stores and loads to stack, return address signing, and redundant
CFI directives before and after call to __libc_arm_za_disable().

The __libc_arm_za_disable implementation follows special calling convention
that allows to avoid most of the operations that would be necessary for a
call to a normal function (see [1] for details).

First, we rely on __libc_arm_za_disable() not clobbering certain registers,
and we put return address into one of these registers. Now we don't need
to store it on stack, so we don't need to sign return address using PAC.

Second, as a result of the above, we don't need to update the CFI offset.

This patch provides small optimisation avoiding unnecessary store and load
on stack also simplifies assembly code and CFI directives.

[1]: https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

0 files changed, 0 insertions, 0 deletions