arm64: Handle SME's ZA in setjmp/longjmp.
AAPCS64 requires that setjmp and longjmp turn ZA off:
https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst#setjmp-and-longjmp
__arm_za_disable is provided as a builtin by compiler-rt and check if
SME is available or not. It is described in the AAPCS64:
https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst#81sme-support-routines
New tests are added to make sure this works as expected.
Test: bionic-unit-tests --gtest_filter='setjmp.*'
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:6f106f79b772c007319abec67e47912bb169c08f)
Merged-In: I4e63a26b4719fa6aebf6e87ee90dbe3d7f76769b
Change-Id: I4e63a26b4719fa6aebf6e87ee90dbe3d7f76769b
diff --git a/libc/arch-arm64/bionic/setjmp.S b/libc/arch-arm64/bionic/setjmp.S
index c408998..e94e5f4 100644
--- a/libc/arch-arm64/bionic/setjmp.S
+++ b/libc/arch-arm64/bionic/setjmp.S
@@ -114,6 +114,9 @@
.cfi_rel_offset x0, 0
.cfi_rel_offset x30, 8
+ // Commit SME's ZA lazy save. Note that the call preserves x1.
+ bl __arm_za_disable
+
// Get the cookie and store it along with the signal flag.
mov x0, x1
bl __bionic_setjmp_cookie_get
@@ -183,6 +186,17 @@
// void siglongjmp(sigjmp_buf env, int value);
ENTRY_WEAK_FOR_NATIVE_BRIDGE(siglongjmp)
+ // First of all, disable SME's ZA, so that it does not interfere
+ // with anything else. Note that __arm_za_disable is guaranteed to
+ // preserve x0 and x1.
+ str x30, [sp, #-16]!
+ .cfi_adjust_cfa_offset 16
+ .cfi_rel_offset x30, 0
+ bl __arm_za_disable
+ ldr x30, [sp], #16
+ .cfi_adjust_cfa_offset -16
+ .cfi_restore x30
+
// Check the checksum before doing anything.
m_calculate_checksum x12, x0, x2
ldr x2, [x0, #(_JB_CHECKSUM * 8)]