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
---
 src/kdata.asm | 11 +++++++++++
 1 file changed, 11 insertions(+)

(limited to 'src/kdata.asm')

diff --git a/src/kdata.asm b/src/kdata.asm
index efc780a..ba395f1 100644
--- a/src/kdata.asm
+++ b/src/kdata.asm
@@ -20,3 +20,14 @@ wTmpWramB::   DS 1
 wTmpSlot::    DS 1
 wTmpPid::     DS 1
 wTmpSP::      DS 2
+
+; cart-RAM bank allocator (bump; bank 0 taken by the init task)
+wNextRamBank:: DS 1
+
+; scratch used by sys_fork
+wForkUserSP::    DS 2      ; parent user SP at fork entry (= Uafter)
+wForkChildSlot:: DS 1
+wForkChildPid::  DS 1
+wForkParentBank::DS 1
+wForkChildBank:: DS 1
+wCopyBuf::       DS 256    ; bank-copy bounce buffer (WRAM0, always mapped)
-- 
cgit v1.3.1-sl0p