1 files changed, 96 insertions, 0 deletions
diff --git a/tools/testing/selftests/arm64/gcs/gcspushm.S b/tools/testing/selftests/arm64/gcs/gcspushm.S
new file mode 100644
index 000000000000..bbe17c1325ac
--- /dev/null
+++ b/tools/testing/selftests/arm64/gcs/gcspushm.S
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// Copyright 2024 Arm Limited
+//
+// Give ourselves GCS push permissions then use them
+
+#include <asm/unistd.h>
+
+/* Shadow Stack/Guarded Control Stack interface */
+#define PR_GET_SHADOW_STACK_STATUS	74
+#define PR_SET_SHADOW_STACK_STATUS      75
+#define PR_LOCK_SHADOW_STACK_STATUS     76
+
+# define PR_SHADOW_STACK_ENABLE         (1UL << 0)
+# define PR_SHADOW_STACK_WRITE		(1UL << 1)
+# define PR_SHADOW_STACK_PUSH		(1UL << 2)
+
+#define KSFT_SKIP 4
+
+.macro function name
+	.macro endfunction
+		.type \name, @function
+		.purgem endfunction
+	.endm
+\name:
+.endm
+
+// Print a single character x0 to stdout
+// Clobbers x0-x2,x8
+function putc
+	str	x0, [sp, #-16]!
+
+	mov	x0, #1			// STDOUT_FILENO
+	mov	x1, sp
+	mov	x2, #1
+	mov	x8, #__NR_write
+	svc	#0
+
+	add	sp, sp, #16
+	ret
+endfunction
+.globl	putc
+
+// Print a NUL-terminated string starting at address x0 to stdout
+// Clobbers x0-x3,x8
+function puts
+	mov	x1, x0
+
+	mov	x2, #0
+0:	ldrb	w3, [x0], #1
+	cbz	w3, 1f
+	add	x2, x2, #1
+	b	0b
+
+1:	mov	w0, #1			// STDOUT_FILENO
+	mov	x8, #__NR_write
+	svc	#0
+
+	ret
+endfunction
+.globl	puts
+
+// Utility macro to print a literal string
+// Clobbers x0-x4,x8
+.macro puts string
+	.pushsection .rodata.str1.1, "aMS", @progbits, 1
+.L__puts_literal\@: .string "\string"
+	.popsection
+
+	ldr	x0, =.L__puts_literal\@
+	bl	puts
+.endm
+
+.globl _start
+function _start
+	// Run with GCS
+	mov	x0, PR_SET_SHADOW_STACK_STATUS
+	mov	x1, PR_SHADOW_STACK_ENABLE | PR_SHADOW_STACK_PUSH
+	mov	x2, xzr
+	mov	x3, xzr
+	mov	x4, xzr
+	mov	x5, xzr
+	mov	x8, #__NR_prctl
+	svc	#0
+	cbz	x0, 1f
+	puts	"Failed to enable GCS with push permission\n"
+	mov	x0, #KSFT_SKIP
+	b	2f
+1:
+	sys	#3, c7, c7, #0, x0	// GCSPUSHM
+	sysl	x0, #3, c7, c7, #1	// GCSPOPM
+
+	mov	x0, #0
+2:
+	mov	x8, #__NR_exit
+	svc	#0