From 353647418912b5b6b94473b15bee312ddc4d64a9 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Wed, 25 Jan 2023 22:05:35 +0100
Subject: kernel: move /mem/alloc to /malloc and linker.ld to arch/amd64/

---
 src/kernel/malloc.c | 177 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 177 insertions(+)
 create mode 100644 src/kernel/malloc.c

(limited to 'src/kernel/malloc.c')

diff --git a/src/kernel/malloc.c b/src/kernel/malloc.c
new file mode 100644
index 0000000..8c52b6f
--- /dev/null
+++ b/src/kernel/malloc.c
@@ -0,0 +1,177 @@
+#include <kernel/arch/generic.h>
+#include <kernel/malloc.h>
+#include <kernel/panic.h>
+#include <kernel/util.h>
+#include <shared/mem.h>
+#include <stdbool.h>
+#include <stdint.h>
+
+#define MALLOC_MAGIC 0xA770C666
+
+struct malloc_hdr {
+	uint32_t magic;
+	uint32_t page_amt;
+	struct malloc_hdr *next, *prev;
+	void *stacktrace[4];
+};
+
+struct malloc_hdr *malloc_last = NULL;
+
+extern uint8_t pbitmap[], pbitmap_start[]; /* linker.ld */
+static size_t pbitmap_len;
+static size_t pbitmap_searchstart = 0;
+static size_t pbitmap_taken = 0;
+
+
+static bool bitmap_get(size_t i) {
+	size_t b = i / 8;
+	assert(b < pbitmap_len);
+	return 0 < (pbitmap[b] & (1 << (i&7)));
+}
+
+static void bitmap_set(size_t i, bool v) {
+	size_t b = i / 8;
+	uint8_t m = 1 << (i&7);
+	assert(b < pbitmap_len);
+	if ((pbitmap[b] & m) ^ v) {
+		/* value changes */
+		if (v) pbitmap_taken++;
+		else   pbitmap_taken--;
+	}
+	if (v) pbitmap[b] |=  m;
+	else   pbitmap[b] &= ~m;
+}
+
+void mem_init(void *memtop) {
+	kprintf("memory   %8x -> %8x\n", &_bss_end, memtop);
+	size_t pageamt = ((uintptr_t)memtop - (uintptr_t)pbitmap_start) / PAGE_SIZE;
+	pbitmap_len = pageamt / 8;
+	memset(pbitmap, 0, pbitmap_len);
+	mem_reserve(pbitmap, pbitmap_len);
+}
+
+void mem_reserve(void *addr, size_t len) {
+	kprintf("reserved %8x -> %8x\n", addr, addr + len);
+
+	/* align to the previous page */
+	size_t off = (uintptr_t)addr & PAGE_MASK;
+	addr -= off;
+	len += off;
+	size_t first = ((uintptr_t)addr - (uintptr_t)pbitmap_start) / PAGE_SIZE;
+	for (size_t i = 0; i * PAGE_SIZE < len; i++) {
+		if (first + i >= pbitmap_len) break;
+		if (bitmap_get(first + i))
+			panic_invalid_state();
+		bitmap_set(first + i, true);
+	}
+}
+
+void mem_debugprint(void) {
+	size_t total = 0;
+	kprintf("current kmallocs:\n");
+	kprintf("addr      pages\n");
+	for (struct malloc_hdr *iter = malloc_last; iter; iter = iter->prev) {
+		kprintf("%08x  %05x", iter, iter->page_amt);
+		for (size_t i = 0; i < 4; i++)
+			kprintf("  k/%08x", iter->stacktrace[i]);
+		kprintf("\n    peek 0x%x\n", *(uint32_t*)(&iter[1]));
+		total++;
+	}
+	kprintf("  total 0x%x\n", total);
+	kprintf("pbitmap usage %u/%u\n", pbitmap_taken, pbitmap_len * 8);
+}
+
+void *page_alloc(size_t pages) {
+	/* i do realize how painfully slow this is */
+	size_t streak = 0;
+	for (size_t i = pbitmap_searchstart; i < pbitmap_len * 8; i++) {
+		if (bitmap_get(i)) {
+			streak = 0;
+			continue;
+		}
+		if (++streak >= pages) {
+			/* found hole big enough for this allocation */
+			i = i + 1 - streak;
+			for (size_t j = 0; j < streak; j++)
+				bitmap_set(i + j, true);
+			pbitmap_searchstart = i + streak - 1;
+			return pbitmap_start + i * PAGE_SIZE;
+		}
+	}
+	kprintf("we ran out of memory :(\ngoodbye.\n");
+	panic_unimplemented();
+}
+
+void *page_zalloc(size_t pages) {
+	void *p = page_alloc(pages);
+	memset(p, 0, pages * PAGE_SIZE);
+	return p;
+}
+
+// frees `pages` consecutive pages starting from *first
+void page_free(void *first_addr, size_t pages) {
+	assert(first_addr >= (void*)pbitmap_start);
+	size_t first = ((uintptr_t)first_addr - (uintptr_t)pbitmap_start) / PAGE_SIZE;
+	if (pbitmap_searchstart > first)
+		pbitmap_searchstart = first;
+	for (size_t i = 0; i < pages; i++) {
+		assert(bitmap_get(first + i));
+		bitmap_set(first + i, false);
+	}
+}
+
+void kmalloc_sanity(const void *addr) {
+	assert(addr);
+	const struct malloc_hdr *hdr = addr - sizeof(struct malloc_hdr);
+	assert(hdr->magic == MALLOC_MAGIC);
+	if (hdr->next) assert(hdr->next->prev == hdr);
+	if (hdr->prev) assert(hdr->prev->next == hdr);
+}
+
+void *kmalloc(size_t len) {
+	// TODO better kmalloc
+
+	struct malloc_hdr *hdr;
+	void *addr;
+	uint32_t pages;
+
+	len += sizeof(struct malloc_hdr);
+	pages = len / PAGE_SIZE + 1;
+
+	hdr = page_alloc(pages);
+	hdr->magic = MALLOC_MAGIC;
+	hdr->page_amt = pages;
+
+	hdr->next = NULL;
+	hdr->prev = malloc_last;
+	if (hdr->prev) {
+		assert(!hdr->prev->next);
+		hdr->prev->next = hdr;
+	}
+
+	for (size_t i = 0; i < 4; i++)
+		hdr->stacktrace[i] = debug_caller(i);
+
+	malloc_last = hdr;
+
+	addr = (void*)hdr + sizeof(struct malloc_hdr);
+	kmalloc_sanity(addr);
+	return addr;
+}
+
+void kfree(void *ptr) {
+	struct malloc_hdr *hdr;
+	if (ptr == NULL) return;
+
+	hdr = ptr - sizeof(struct malloc_hdr);
+	kmalloc_sanity(ptr);
+
+	hdr->magic = ~MALLOC_MAGIC; // (hopefully) detect double frees
+	if (hdr->next)
+		hdr->next->prev = hdr->prev;
+	if (hdr->prev)
+		hdr->prev->next = hdr->next;
+	if (malloc_last == hdr)
+		malloc_last = hdr->prev;
+	page_free(hdr, hdr->page_amt);
+}
-- 
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