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-rw-r--r--src/cpu/x86/64bit/mode_switch.S70
1 files changed, 70 insertions, 0 deletions
diff --git a/src/cpu/x86/64bit/mode_switch.S b/src/cpu/x86/64bit/mode_switch.S
new file mode 100644
index 0000000000..eea104bcf3
--- /dev/null
+++ b/src/cpu/x86/64bit/mode_switch.S
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+.text
+.code64
+ .section ".text.protected_mode_call", "ax", @progbits
+ .globl protected_mode_call_narg
+protected_mode_call_narg:
+
+ push %rbp
+ mov %rsp, %rbp
+ /* Preserve registers */
+ push %rbx
+ push %r12
+ push %r13
+ push %r14
+ push %r15
+
+ /* Arguments to stack */
+ push %rdi
+ push %rsi
+ push %rdx
+ push %rcx
+
+ #include <cpu/x86/64bit/exit32.inc>
+
+ movl -48(%ebp), %eax /* Argument count */
+ movl -64(%ebp), %edx /* Argument 0 */
+ movl -72(%ebp), %ecx /* Argument 1 */
+
+ /* Align the stack */
+ andl $0xFFFFFFF0, %esp
+ test %eax, %eax
+ je 1f /* Zero arguments */
+
+ subl $1, %eax
+ test %eax, %eax
+ je 2f /* One argument */
+
+ /* Two arguments */
+ subl $8, %esp
+ pushl %ecx /* Argument 1 */
+ pushl %edx /* Argument 0 */
+ jmp 1f
+2:
+ subl $12, %esp
+ pushl %edx /* Argument 0 */
+
+1:
+ movl -56(%ebp), %ebx /* Function to call */
+ call *%ebx
+ movl %eax, %ebx
+
+ /* Preserves ebx */
+ #include <cpu/x86/64bit/entry64.inc>
+
+ /* Place return value in rax */
+ movl %ebx, %eax
+
+ /* Restore registers */
+ mov -40(%rbp), %r15
+ mov -32(%rbp), %r14
+ mov -24(%rbp), %r13
+ mov -16(%rbp), %r12
+ mov -8(%rbp), %rbx
+
+ /* Restore stack pointer */
+ mov %rbp, %rsp
+ pop %rbp
+
+ ret