diff options
| -rw-r--r-- | kernel/usermode.c | 32 | ||||
| -rw-r--r-- | kernel/usermode.h | 46 |
2 files changed, 78 insertions, 0 deletions
diff --git a/kernel/usermode.c b/kernel/usermode.c new file mode 100644 index 0000000..afad9df --- /dev/null +++ b/kernel/usermode.c @@ -0,0 +1,32 @@ +#include "usermode.h" + + +void install_tss(int cpu_no){ + // now fill each value + // set values necessary + sys_tss.ss0 = 0x10; + // now set the IO bitmap (not necessary, so set above limit) + sys_tss.iomap = ( unsigned short ) sizeof( tss_struct ); +} + +void switch_to_user_mode() { + // Set up a stack structure for switching to user mode. + asm volatile(" \ + cli; \ + mov $0x23, %ax; \ + mov %ax, %ds; \ + mov %ax, %es; \ + mov %ax, %fs; \ + mov %ax, %gs; \ + \ + mov %esp, %eax; \ + pushl $0x23; \ + pushl %eax; \ + pushf; \ + mov $0x200, %eax; \ + push %eax; \ + pushl $0x1B; \ + push $1f; \ + iret; \ 1: \ + "); +} diff --git a/kernel/usermode.h b/kernel/usermode.h new file mode 100644 index 0000000..e9195e1 --- /dev/null +++ b/kernel/usermode.h @@ -0,0 +1,46 @@ +// https://xarnze.com/posts/post/Tutorial:%20Entering%20User%20mode +// http://wiki.osdev.org/TSS +// http://wiki.osdev.org/Global_Descriptor_Table + +typedef volatile struct strtss{ + unsigned short link; + unsigned short link_h; + unsigned long esp0; + unsigned short ss0; + unsigned short ss0_h; + unsigned long esp1; + unsigned short ss1; + unsigned short ss1_h; + unsigned long esp2; + unsigned short ss2; + unsigned short ss2_h; + unsigned long cr3; + unsigned long eip; + unsigned long eflags; + unsigned long eax; + unsigned long ecx; + unsigned long edx; + unsigned long ebx; + unsigned long esp; + unsigned long ebp; + unsigned long esi; + unsigned long edi; + unsigned short es; + unsigned short es_h; + unsigned short cs; + unsigned short cs_h; + unsigned short ss; + unsigned short ss_h; + unsigned short ds; + unsigned short ds_h; + unsigned short fs; + unsigned short fs_h; + unsigned short gs; + unsigned short gs_h; + unsigned short ldt; + unsigned short ldt_h; + unsigned short trap; + unsigned short iomap; +}__attribute__((packed)) tss_struct; + +tss_struct sys_tss; //Define the TSS as a global structure |