implement va_list - variable arguments

arch/x86_64.S

@@ -6,6 +6,8 @@
 .globl _cu_memset
 .globl cu_memzero
 .globl cu_memtest
+.globl cu_va_start
+.globl cu_va_arg
 
 .text
 
@@ -113,4 +115,42 @@ cu_memtest:
     ret
 .testfail:
     mov %rsi, %rax
-    ret
+    ret
+
+
+cu_va_start:
+    // RDI - va
+    mov %rsp, %rax
+    mov %rdi, %rsp
+    add $0x30, %rsp
+
+    push %r9
+    push %r8
+    push %rcx
+    push %rdx
+    push %rsi
+    push %rdi
+
+    mov %rax, %rsp
+    ret
+
+cu_va_arg:
+    // RDI - va, RSI - index
+    push %rbx
+    mov %rsi, %rbx
+    shl $3, %rbx
+
+    cmp $6, %rsi
+    jge .va_stack
+
+    mov (%rbx,%rdi),%rax
+
+    pop %rbx
+    ret
+.va_stack:
+    sub $0x30, %rbx
+    add $0x10, %rbx
+    mov (%rbx,%rbp),%rax
+
+    pop %rbx
+    ret

test.c

@@ -8,6 +8,7 @@
 #include "bitmap.h"
 #include "endian.h"
 #include "struct.h"
+#include "va_list.h"
 
 typedef uint8_t item_t[14];
 
@@ -35,6 +36,16 @@ CU_VALUE_INT64()
 CU_VALUE_ARRAY_ZERO(sizeof(char))
 CU_STRUCT_END()
 
+void va_test(int fixed, ...)
+{
+    cu_va_list va;
+    cu_va_start(&va);
+    
+    printf("va_test\n");
+    for (unsigned i = 0; i < 6; i++)
+        printf("\t%lu\n", cu_va_arg(&va, i));
+}
+
 int main()
 {
     cutil_init();
@@ -147,6 +158,9 @@ int main()
     printf("value_offset\t%u\n", value_offset(CU_STRUCT(test_s), 5, &test));
     printf("value_size\t%u\n", value_size(CU_STRUCT(test_s), 5, &test));
 
+    printf("[va_list]\n");
+    va_test(1337, 1, 2, 3, 4, 5);
+
     cutil_exit();
     return 0;
-}
+}

va_list.h

@@ -0,0 +1,19 @@
+#ifndef __VA_LIST_H
+#define __VA_LIST_H
+
+#include "cutypes.h"
+
+#if (CU_ARCH == x86_64)
+#   define VA_NUM   6
+#else
+#   define VA_NUM   0
+#endif
+
+typedef struct {
+    uword args[VA_NUM];
+} cu_va_list;
+
+extern void cu_va_start(cu_va_list* va);
+extern uword cu_va_arg(cu_va_list* va, unsigned idx);
+
+#endif