[PATCH] arm: Zero/Sign extends for CMSE security

[Richard Ball]

This patch makes the following changes:

1) When calling a secure function from non-secure code then any arguments
   smaller than 32-bits that are passed in registers are zero- or sign-extended.
2) After a non-secure function returns into secure code then any return value
   smaller than 32-bits that is passed in a register is  zero- or sign-extended.

This patch addresses the following CVE-2024-0151.

gcc/ChangeLog:
        PR target/114837
        * config/arm/arm.cc (cmse_nonsecure_call_inline_register_clear):
          Add zero/sign extend.
        (arm_expand_prologue): Add zero/sign extend.

gcc/testsuite/ChangeLog:

        * gcc.target/arm/cmse/extend-param.c: New test.
        * gcc.target/arm/cmse/extend-return.c: New test.
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