; Calcite, src/kernel/process.asm
 ; Copyright 2025 Benji Dial
 ;
 ; This program is free software: you can redistribute it and/or modify
 ; it under the terms of the GNU General Public License as published by
 ; the Free Software Foundation, either version 3 of the License, or
 ; (at your option) any later version.
 ;
 ; This program is distributed in the hope that it will be useful, but
 ; WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 ; or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 ; for more details.
 ;
 ; You should have received a copy of the GNU General Public License along
 ; with this program. If not, see <https://www.gnu.org/licenses/>.


bits 64

extern running_thread

section .text

;referenced in process.c
global thread_start
thread_start:

  mov rax, qword [running_thread]
  test rax, rax
  jnz .assert_fail

  mov qword [running_thread], rbx

  mov cr3, rbp
  mov rcx, r12
  mov r11, 0x200

  xor rax, rax
  xor rbx, rbx
  xor rdx, rdx
  xor rdi, rdi
  xor rsi, rsi
  xor rbp, rbp
  xor r8, r8
  xor r9, r9
  xor r10, r10
  xor r12, r12
  xor r13, r13
  xor r14, r14
  xor r15, r15

  o64 sysret

.assert_fail:
  ;could be nice to handle this more gracefully in the future
  ud2