From ab3ebbe227c72b745a46f9233fbfbb27477586b8 Mon Sep 17 00:00:00 2001
From: user <user@clank>
Date: Wed, 15 Jul 2026 23:54:13 +0200
Subject: kernel: implement fork()

- sys_fork: switch to a kernel stack, bump-allocate a cart-RAM bank, copy the
  parent's 8 KiB bank via a WRAM bounce buffer, plant a switch-in frame so the
  child returns 0 to the post-fork PC, fill the child PCB (shared ROM text)
- add AllocRamBank (bump allocator) + FindFreeSlot helpers
- demo: init forks; parent prints P, child prints C (PCPC...); nested fork
  gives three distinct pids (123...)
- README: document the fork mechanism, mark syscall status
---
 include/gbos.inc | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'include/gbos.inc')

diff --git a/include/gbos.inc b/include/gbos.inc
index c22344a..0727b02 100644
--- a/include/gbos.inc
+++ b/include/gbos.inc
@@ -46,6 +46,8 @@ DEF KSTACK_TOP      EQU $D000   ; kernel stack top (grows down into WRAM0)
 ; Process table
 ; -----------------------------------------------------------------------------
 DEF MAX_PROCS       EQU 8
+DEF NUM_RAM_BANKS   EQU 4    ; MBC5 cart RAM banks available (-r 3 = 32 KiB)
+DEF KSTACK_TOP2     EQU $D000 ; kernel stack top reused for syscalls (fork)
 
 ; process states
 DEF PS_FREE     EQU 0
-- 
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