From 3705cf387ec9a87f0330766ccc933ff53f0bf530 Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Fri, 8 Sep 2017 19:52:17 +0200
Subject: Add syscalls to x86-64 linux

---
 arch/x64/linux/syscall.S | 65 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 arch/x64/linux/syscall.S

(limited to 'arch/x64/linux/syscall.S')

diff --git a/arch/x64/linux/syscall.S b/arch/x64/linux/syscall.S
new file mode 100644
index 0000000..9261d87
--- /dev/null
+++ b/arch/x64/linux/syscall.S
@@ -0,0 +1,65 @@
+/*
+The kernel uses the following registers:
+%rdi, %rsi, %rdx, %r8, %r9, %r10
+
+The number of the syscall is passed in %rax.
+
+A syscall clobbers:
+%rax, %rcx, %r11
+
+The returned value is placed in %rax.
+*/
+	.text
+
+	.globl syscall1
+	.type syscall1, @function
+
+syscall1:
+	movq %rsi, %rax // Syscall number.
+
+	syscall
+
+	ret
+
+
+	.globl syscall2
+	.type syscall2, @function
+
+syscall2:
+	// Store registers.
+	movq %rdi, %r8
+
+	movq %rdx, %rax // Syscall number.
+
+	// Syscall arguments.
+	movq %rsi, %rdi
+	movq %r8, %rsi
+
+	syscall
+
+	// Restore registers.
+	movq %rdi, %rsi
+	movq %r8, %rdi
+
+	ret
+
+
+	.globl syscall3
+	.type syscall3, @function
+
+syscall3:
+	// Store registers.
+	movq %rdi, %r8
+
+	movq %rcx, %rax // Syscall number.
+
+	// Syscall arguments.
+	movq %rdx, %rdi
+	movq %r8, %rdx
+
+	syscall
+
+	// Restore registers.
+	movq %r8, %rdi
+
+	ret
-- 
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