From 6533334824e70c57ca281ee8406326a05beedc09 Mon Sep 17 00:00:00 2001
From: Starnakin <camille@chauvet.pro>
Date: Wed, 30 Oct 2024 21:26:00 +0100
Subject: [PATCH] fix: free: use the new pt system

---
 src/kernel.c       |  5 +++--
 src/memory/frame.c | 23 ++++++++++-------------
 src/memory/page.c  | 24 +++++++++++++++++-------
 3 files changed, 30 insertions(+), 22 deletions(-)

diff --git a/src/kernel.c b/src/kernel.c
index c336db2..5a5081d 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -36,10 +36,11 @@ void kernel_main(void)
 	        "I see no way to confuse an array of 256 seg:off pairs with a "
 	        "complex 8*unknown quantity -byte descriptor table. -- Troy "
 	        "Martin 03:50, 22 March 2009 (UTC)\n");
-	while (true) {
+	for (uint16_t i = 0;; i++) {
 		void *ptr = alloc_pages(4096);
-		memset(ptr, ~0, 4096);
 		PRINT_PTR(ptr);
+		memset(ptr, ~0, 4096);
+		free_pages(ptr, 4096);
 	}
 	/* int i = 0; */
 	/* while (vmalloc(10)) */
diff --git a/src/memory/frame.c b/src/memory/frame.c
index 1703e55..08caa96 100644
--- a/src/memory/frame.c
+++ b/src/memory/frame.c
@@ -9,15 +9,19 @@
 
 #define MAX_FRAMES (HEAP_END / PAGE_SIZE)
 
+enum {
+	FREE,
+	USED,
+};
+
 static uint8_t frame_table[MAX_FRAMES];
-static uint32_t remaining_frames = MAX_FRAMES;
 
 static int32_t find_next_block(size_t nb_frames)
 {
 	for (uint32_t i = CEIL(HEAP_START, PAGE_SIZE);
 	     i + nb_frames < MAX_FRAMES; i++) {
 		uint32_t j;
-		for (j = 0; frame_table[i + j] == 0 && j < nb_frames; j++)
+		for (j = 0; frame_table[i + j] == FREE && j < nb_frames; j++)
 			;
 		if (j == nb_frames)
 			return i;
@@ -29,28 +33,22 @@ static int32_t find_next_block(size_t nb_frames)
 void *alloc_frames(size_t size)
 {
 	const uint32_t nb_frames = CEIL(size, PAGE_SIZE);
-	if (nb_frames > remaining_frames) {
-		kprintf(KERN_CRIT "Not enough frames (max: %d)\n", MAX_FRAMES);
-		return NULL;
-	}
-	int i = find_next_block(nb_frames);
+	const int i = find_next_block(nb_frames);
 	if (i < 0) {
 		kprintf(KERN_WARNING "Not enough frames available\n");
 		return NULL;
 	}
 	for (size_t j = 0; j < nb_frames; j++) {
 		assert(j + i < MAX_FRAMES);
-		frame_table[j + i] = 1;
+		frame_table[j + i] = USED;
 	}
-	assert(remaining_frames >= nb_frames);
-	remaining_frames -= nb_frames;
 	return (void *)(i * PAGE_SIZE);
 }
 
 int free_frames(void *frame_ptr, size_t size)
 {
 	const uint32_t nb_frames = CEIL(size, PAGE_SIZE);
-	const uint32_t start = (uint32_t)(frame_ptr + HEAP_END) / PAGE_SIZE;
+	const uint32_t start = (uint32_t)frame_ptr / PAGE_SIZE;
 
 	if (start > MAX_FRAMES) {
 		kprintf(KERN_WARNING "Address out of range\n");
@@ -63,7 +61,6 @@ int free_frames(void *frame_ptr, size_t size)
 		return -1;
 	}
 	for (size_t i = start; i < start + nb_frames; i++)
-		frame_table[i] = 0;
-	remaining_frames += nb_frames;
+		frame_table[i] = FREE;
 	return 0;
 }
diff --git a/src/memory/page.c b/src/memory/page.c
index a77d419..fc5f261 100644
--- a/src/memory/page.c
+++ b/src/memory/page.c
@@ -60,22 +60,32 @@ void *alloc_pages(size_t size)
 
 int free_pages(void *page_ptr, size_t size)
 {
+	const uint32_t page_addr = (uint32_t)page_ptr;
 	const uint32_t nb_pages = CEIL(size, PAGE_SIZE);
-	const uint32_t page_index = (uint32_t)page_ptr / PAGE_SIZE;
+	const uint32_t page_index = page_addr / PAGE_SIZE;
+	const uint32_t pd_index = page_index / PD_SIZE;
+	const uint32_t pt_index = page_index % PD_SIZE;
 
-	if ((uint32_t)page_ptr > PT_SIZE * PAGE_SIZE) {
+	if ((uint32_t)pd_index > 0x300) {
 		kprintf(KERN_WARNING "Address out of range\n");
 		return -1;
-	} else if ((uint32_t)page_ptr % PAGE_SIZE) {
+	} else if (page_addr % PAGE_SIZE) {
 		kprintf(KERN_WARNING "Invalid address\n");
 		return -1;
-	} else if (page_index + nb_pages > PT_SIZE) {
+	} else if (pt_index + nb_pages > PT_SIZE) {
 		kprintf(KERN_WARNING "Invalid number of frames\n");
 		return -1;
 	}
-	for (size_t i = page_index; i < page_index + nb_pages; i++) {
-		free_frames((void *)(i >> 12), PAGE_SIZE);
-		i = i << 12 | INIT_FLAGS;
+	uint32_t *page_table =
+	    (uint32_t *)GET_PAGE_ADDR(0, PT_START + pd_index);
+	for (uint16_t i = pt_index; i < pt_index + nb_pages; i++) {
+		if (page_table[i] >> 12 == i) {
+			kprintf(KERN_WARNING "Page already free\n");
+			return -2;
+		}
+		free_frames((void *)(page_table[i] & PAGE_MASK), PAGE_SIZE);
+		page_table[i] = i << 12;
 	}
+
 	return 0;
 }