- Added first-fit free-list allocator with block splitting and coalescing.
Provides kmalloc(), kfree(), and kcalloc() for kernel-space dynamic memory.
- Each block carries an inline header with a magic value (0xCAFEBABE) for
heap corruption detection, plus double-free checking.
- Memory is obtained from the paging subsystem in 4 KiB page increments.
All allocations are 8-byte aligned with a 16-byte minimum block size.
- Created freestanding string.c with memset, memcpy, memmove, memcmp,
strlen, strcmp, strncmp, strcpy, strncpy — replacing the unavailable
libc implementations.
- Added documentation in docs/kmalloc.md.
Tested: kmalloc(64) returns 0xD0001010 (in kernel heap) and kfree succeeds.
Works with both 4 MiB and 128 MiB RAM.
- Created two-level x86 paging (page directory + page tables) with 4 KiB pages.
- Identity maps all detected physical memory in two phases:
1) Static: first 16 MiB using 4 BSS-allocated page tables (avoids
chicken-and-egg with PMM bitmap in BSS).
2) Dynamic: memory above 16 MiB using PMM-allocated page tables,
created before paging is enabled so physical addresses still work.
- Provides kernel heap at 0xD0000000–0xF0000000 for virtual page allocation.
- API: paging_map_page, paging_unmap_page, paging_alloc_page, paging_free_page,
paging_get_physical.
- Added pmm_get_memory_size() to expose detected RAM for paging init.
- Kernel tests paging by allocating a virtual page, writing 0xDEADBEEF, and
reading it back, then freeing it.
- Added documentation in docs/paging.md.
Tested: boots and passes paging test with both 4 MiB and 128 MiB RAM in QEMU.
- Changed grub.cfg from 'multiboot' to 'multiboot2' command. The PMM parses
Multiboot2 tag structures, but GRUB was booting with Multiboot1 protocol,
causing the memory map parsing to silently fail (all memory stayed marked
as used, leading to OOM on every allocation).
- Fixed BITMAP_SIZE calculation to properly round up instead of truncating,
ensuring the last few pages of the address space are covered.
- Fixed sign comparison warning in bitmap init loop.
- Added debug output to PMM init (mem_upper, region count) for diagnostics.
- Removed stale Multiboot1 magic constant and (void)addr cast from kernel.c.
- Added documentation for the interrupt subsystem and PMM in docs/.
- Checked off 'Implement a PIC handler' and 'Create a physical memory
allocator' in the task list.
Tested: kernel boots in QEMU with both 4MB and 128MB RAM, PMM correctly
allocates from NORMAL zone (0x01000000) and DMA zone (0x00001000).
