kernel/usrspace.s


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global userspace_init
extern _binary_usrbin_bin_size
extern _binary_usrbin_bin_start
extern tss

userspace_init:
  push ebp
  mov ebp, esp
  push esi
  push edi
  mov ecx, _binary_usrbin_bin_size
  mov esi, _binary_usrbin_bin_start
  mov edi, 0x100000
.loop:
  movsb
  dec ecx
  jz .end
  jmp .loop
.end:
  pop edi
  pop esi
  call usrcall
  pop ebp
  ret

usrcall:
  push ebp
  mov ebp, esp
  cli
  mov ax, 0x23
  mov ds, ax
  mov es, ax
  mov fs, ax
  mov gs, ax
  mov eax, esp
  ; save ESP in the TSS
  mov [tss+4], eax
  push dword 0x23
  push dword 0x00180000
  pushf
  push dword 0x1B
  push dword 0x00100000
  iret
  pop ebp
  ret