diff options
Diffstat (limited to 'asm/asm_usermode.S')
| -rw-r--r-- | asm/asm_usermode.S | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/asm/asm_usermode.S b/asm/asm_usermode.S new file mode 100644 index 0000000..a07f480 --- /dev/null +++ b/asm/asm_usermode.S @@ -0,0 +1,39 @@ +.global asm_usermode + +asm_usermode: + + mov 0x4(%esp),%edx //get adress of passed : void func() + //to be called in ring 3 + + // 0x23 is user data segment (|2 low bits) + // 0x1b is user code segment (|2 low bits) + + // set segment registers + mov $0x23, %ax + mov %ax, %ds + mov %ax, %es + mov %ax, %fs + mov %ax, %gs + + // ss is handled by iret + + mov %esp, %eax + + pushl $0x23 // user data segment + //pushl $0x8fff000-3*32 //%eax // current stack + pushl $0xe0000000-3*32 //%eax // current stack (3 values will be poped) we subst 4 to align + pushf // + + // http://x86.renejeschke.de/html/file_module_x86_id_145.html + //mov $0x200, %eax + //push %eax // eflags image + pushl $0x1B // return code segment selector + push %edx // return instruction pointer + + iret + + jmp . // never to be reached + + + + |