[glibc] aarch64: Add longjmp support for SME

[glibc] aarch64: Add longjmp support for SME

[Szabolcs Nagy]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=a7373e457f0b5953d230f7756627036b1711dcc3

commit a7373e457f0b5953d230f7756627036b1711dcc3
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Wed Dec 1 11:37:44 2021 +0000

    aarch64: Add longjmp support for SME
    
    For the ZA lazy saving scheme to work, longjmp has to call
    __libc_arm_za_disable.
    
    In ld.so we assume ZA is not used so longjmp does not need
    special support there.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 sysdeps/aarch64/__longjmp.S | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/sysdeps/aarch64/__longjmp.S b/sysdeps/aarch64/__longjmp.S
index 2c8ff54112..7b6add751e 100644
--- a/sysdeps/aarch64/__longjmp.S
+++ b/sysdeps/aarch64/__longjmp.S
@@ -49,6 +49,28 @@ ENTRY (__longjmp)
 
 	PTR_ARG (0)
 
+#if IS_IN(libc)
+	/* Disable ZA state of SME in libc.a and libc.so, but not in ld.so.  */
+# if HAVE_AARCH64_PAC_RET
+	PACIASP
+	cfi_window_save
+# endif
+	stp	x29, x30, [sp, -16]!
+	cfi_adjust_cfa_offset (16)
+	cfi_rel_offset (x29, 0)
+	cfi_rel_offset (x30, 8)
+	mov	x29, sp
+	bl	__libc_arm_za_disable
+	ldp	x29, x30, [sp], 16
+	cfi_adjust_cfa_offset (-16)
+	cfi_restore (x29)
+	cfi_restore (x30)
+# if HAVE_AARCH64_PAC_RET
+	AUTIASP
+	cfi_window_save
+# endif
+#endif
+
 	ldp	x19, x20, [x0, #JB_X19<<3]
 	ldp	x21, x22, [x0, #JB_X21<<3]
 	ldp	x23, x24, [x0, #JB_X23<<3]