From ed1ed2fc98cc795acd9bdc76be6d1df138c505c7 Mon Sep 17 00:00:00 2001
From: Matthew Sotoudeh <matthew@masot.net>
Date: Thu, 16 May 2024 02:23:46 -0700
Subject: no longer require aligned base address

---
 magic_buddy.c |  9 +++++++--
 main.c        | 11 +----------
 2 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/magic_buddy.c b/magic_buddy.c
index 52cf764..18c4e23 100644
--- a/magic_buddy.c
+++ b/magic_buddy.c
@@ -13,6 +13,7 @@ struct free_list {
 
 static struct free_list *(AVAIL[ADDRESS_BITS]);
 static size_t ROOT_LOGSIZE;
+static void *BASE;
 
 // log2 of size rounded up (ceil) or down (!ceil) to the nearest power of 2
 static size_t size2log(size_t size, int ceil) {
@@ -29,9 +30,11 @@ static size_t size2log(size_t size, int ceil) {
 
 void init_buddy(uint8_t *base, size_t size,
                 uint8_t magic[MAGIC_COOKIE_BYTES]) {
+    BASE = base;
+
     size_t logsize = size2log(size, 0);
     ROOT_LOGSIZE = logsize;
-    assert(((size_t)base & ((1 << logsize) - 1)) == 0);
+
     AVAIL[logsize] = (struct free_list *)base;
     AVAIL[logsize]->next = 0;
     AVAIL[logsize]->pprev = &(AVAIL[logsize]);
@@ -39,7 +42,9 @@ void init_buddy(uint8_t *base, size_t size,
 }
 
 static struct free_list *buddy_of(struct free_list *block, size_t logsize) {
-    return (void *)((size_t)block ^ (1 << logsize));
+    size_t virt_block = (size_t)block - (size_t)BASE;
+    size_t virt_buddy = virt_block ^ (1 << logsize);
+    return (void*)((uint8_t*)BASE + virt_buddy);
 }
 
 static int isfree(struct free_list *block) {
diff --git a/main.c b/main.c
index b84e958..e3b62bd 100644
--- a/main.c
+++ b/main.c
@@ -12,21 +12,12 @@ void get_random(uint8_t *dst, size_t count) {
     close(fd);
 }
 
-// helper for getting an aligned allocation
-static void *malloc_aligned(size_t size) {
-    uint8_t *data = malloc(size);
-    if (!((size_t)data % size)) return data;
-    data = realloc(data, size * 2);
-    data = data + (size - ((size_t)data % size));
-    return data;
-}
-
 void main() {
     size_t region_size = 1024 * 1024;
 
     uint8_t magic[MAGIC_COOKIE_BYTES];
     get_random(magic, MAGIC_COOKIE_BYTES);
-    init_buddy(malloc_aligned(region_size), region_size, magic);
+    init_buddy(malloc(region_size), region_size, magic);
     memset(magic, 0, sizeof(magic));
 
     void *x = allocate(1024);
-- 
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