1 files changed, 28 insertions, 0 deletions
diff --git a/usr/klibc/arch/x86_64/syscall.S b/usr/klibc/arch/x86_64/syscall.S
new file mode 100644
index 0000000..1797797
--- /dev/null
+++ b/usr/klibc/arch/x86_64/syscall.S
@@ -0,0 +1,28 @@
+/*
+ * arch/x86-64/syscall.S
+ *
+ * Common tail-handling code for system calls.
+ *
+ * The arguments are in the standard argument registers; the system
+ * call number in %eax.
+ */
+	.text
+	.align	4
+	.globl	__syscall_common
+	.type	__syscall_common,@function
+__syscall_common:
+	movq	%rcx,%r10		# The kernel uses %r10 istf %rcx
+	syscall
+
+	cmpq	$-4095,%rax
+	jnb	1f
+	ret
+
+	# Error return, must set errno
+1:
+	negl	%eax
+	movl	%eax,errno(%rip)	# errno is type int, so 32 bits
+	orq	$-1,%rax		# orq $-1 smaller than movq $-1
+	ret
+
+	.size	__syscall_common,.-__syscall_common