From: Yury Khrustalev <yury.khrustalev@arm.com>
Date: Thu, 25 Sep 2025 14:51:30 +0000 (+0100)
Subject: aarch64: define macro for calling __libc_arm_za_disable
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b4b713bd8921aff04773557da94fabb5fb9dd705;p=thirdparty%2Fglibc.git

aarch64: define macro for calling __libc_arm_za_disable

A common sequence of instructions is used in several places
in assembly files, so define it in one place as an assembly
macro.

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

diff --git a/sysdeps/aarch64/__longjmp.S b/sysdeps/aarch64/__longjmp.S
index 70ac02c44b..53b42e1bdc 100644
--- a/sysdeps/aarch64/__longjmp.S
+++ b/sysdeps/aarch64/__longjmp.S
@@ -26,16 +26,8 @@
 ENTRY (__longjmp)
 
 #if IS_IN(libc)
-	/* Disable ZA state of SME in libc.a and libc.so, but not in ld.so.
-	   The calling convention of __libc_arm_za_disable allows to do
-	   this thus allowing to avoid saving to and reading from stack.
-	   As a result we also don't need to sign the return address and
-	   check it after returning because it is not stored to stack.  */
-	mov	x13, x30
-	cfi_register (x30, x13)
-	bl	__libc_arm_za_disable
-	mov	x30, x13
-	cfi_register (x13, x30)
+	/* Disable ZA state of SME in libc.a and libc.so, but not in ld.so.  */
+	CALL_LIBC_ARM_ZA_DISABLE
 #endif
 
 	cfi_def_cfa (x0, 0)
diff --git a/sysdeps/aarch64/setjmp.S b/sysdeps/aarch64/setjmp.S
index 53c5e7d8cc..92cedfad83 100644
--- a/sysdeps/aarch64/setjmp.S
+++ b/sysdeps/aarch64/setjmp.S
@@ -37,16 +37,8 @@ ENTRY_ALIGN (__sigsetjmp, 2)
 1:
 
 #if IS_IN(libc)
-	/* Disable ZA state of SME in libc.a and libc.so, but not in ld.so.
-	   The calling convention of __libc_arm_za_disable allows to do
-	   this thus allowing to avoid saving to and reading from stack.
-	   As a result we also don't need to sign the return address and
-	   check it after returning because it is not stored to stack.  */
-	mov	x13, x30
-	cfi_register (x30, x13)
-	bl	__libc_arm_za_disable
-	mov	x30, x13
-	cfi_register (x13, x30)
+	/* Disable ZA state of SME in libc.a and libc.so, but not in ld.so.  */
+	CALL_LIBC_ARM_ZA_DISABLE
 #endif
 
 	stp	x19, x20, [x0, #JB_X19<<3]
diff --git a/sysdeps/unix/sysv/linux/aarch64/setcontext.S b/sysdeps/unix/sysv/linux/aarch64/setcontext.S
index d9716f012e..8e98594663 100644
--- a/sysdeps/unix/sysv/linux/aarch64/setcontext.S
+++ b/sysdeps/unix/sysv/linux/aarch64/setcontext.S
@@ -49,15 +49,7 @@ ENTRY (__setcontext)
 	b	C_SYMBOL_NAME (__syscall_error)
 1:
 	/* Clear ZA state of SME.  */
-	/* The calling convention of __libc_arm_za_disable allows to do
-	   this thus allowing to avoid saving to and reading from stack.
-	   As a result we also don't need to sign the return address and
-	   check it after returning because it is not stored to stack.  */
-	mov	x13, x30
-	cfi_register (x30, x13)
-	bl	__libc_arm_za_disable
-	mov	x30, x13
-	cfi_register (x13, x30)
+	CALL_LIBC_ARM_ZA_DISABLE
 	/* Restore the general purpose registers.  */
 	mov	x0, x9
 	cfi_def_cfa (x0, 0)
diff --git a/sysdeps/unix/sysv/linux/aarch64/sysdep.h b/sysdeps/unix/sysv/linux/aarch64/sysdep.h
index f0e8d64eef..fa01386b25 100644
--- a/sysdeps/unix/sysv/linux/aarch64/sysdep.h
+++ b/sysdeps/unix/sysv/linux/aarch64/sysdep.h
@@ -150,6 +150,18 @@
     mov x8, SYS_ify (syscall_name);		\
     svc 0
 
+/* Clear ZA state of SME (ASM version).  */
+/* The __libc_arm_za_disable function has special calling convention
+   that allows to call it without stack manipulation and preserving
+   most of the registers.  */
+	.macro CALL_LIBC_ARM_ZA_DISABLE
+	mov		x13, x30
+	.cfi_register	x30, x13
+	bl		__libc_arm_za_disable
+	mov		x30, x13
+	.cfi_register	x13, x30
+	.endm
+
 #else /* not __ASSEMBLER__ */
 
 # define VDSO_NAME  "LINUX_2.6.39"