masterclass le dementor

malloc/src/helpers/allocate.c

@@ -12,7 +12,7 @@ void *allocate_block(struct bucket *biquette, int block_number)
         return NULL;
 
     // Update header
-    unsigned char byte_mask = 1 << (8 - 1 - (block_number % 8));
+    unsigned char byte_mask = 1 << (block_number % 8);
     biquette->alloc_blk_cnt++;
     biquette->free_map[block_number / 8] |= byte_mask;
 
@@ -22,17 +22,24 @@ void *allocate_block(struct bucket *biquette, int block_number)
 
 struct bucket *create_bucket(size_t min_alloc_size)
 {
-    // Round up
+    size_t page_alloc_size;
-    size_t alloc_size;
+    size_t block_alloc_size;
+
     if (min_alloc_size > PAGE_SIZE - sizeof(struct bucket))
+    {
         // Huge page
-        alloc_size = min_alloc_size;
+        page_alloc_size = min_alloc_size + sizeof(struct bucket);
+        block_alloc_size = page_alloc_size;
+    }
     else
+    {
         // Regular page
-        alloc_size = s2p(min_alloc_size);
+        page_alloc_size = PAGE_SIZE;
+        block_alloc_size = s2p(min_alloc_size);
+    }
 
     // Get page
-    void *page = mmap(NULL, alloc_size, PROT_READ | PROT_WRITE,
+    void *page = mmap(NULL, page_alloc_size, PROT_READ | PROT_WRITE,
                       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 
     if (page == NULL)
@@ -40,9 +47,9 @@ struct bucket *create_bucket(size_t min_alloc_size)
 
     // Init bucket
     struct bucket *header = page;
-    header->block_size = alloc_size;
+    header->block_size = block_alloc_size;
     header->alloc_blk_cnt = 0;
-    header->alloc_size = alloc_size;
+    header->alloc_size = page_alloc_size;
     memset(header->free_map, 0, FREE_LIST_SIZE);
 
     return header;
@@ -73,14 +80,11 @@ void free_block(void *ptr, struct bucket **list)
     if (block_number == -1)
         return;
 
-    unsigned char byte_mask = 1 << ((block_number % 8) - 1);
+    unsigned char byte_mask = 1 << ((block_number % 8));
     header->free_map[block_number / 8] &= ~byte_mask;
+    header->alloc_blk_cnt--;
 
     // Huge page
-    if (header->block_size > BUCKET_SIZE)
-        // Delete bucket
-        header->alloc_blk_cnt = 0;
-
     // free bucket if necessary
     if (header->alloc_blk_cnt == 0)
     {

malloc/src/helpers/helpers.c

@@ -32,19 +32,32 @@ size_t s2p(size_t s)
 
 int find_free_block(struct bucket *buck)
 {
-    unsigned maplength = PAGE_SIZE / buck->block_size / 8;
+    // Huge pages
-    // for each block
+    if (buck->block_size > BUCKET_SIZE)
+    {
+        // Check block 0
+        if (!(buck->free_map[0] & (1 << 0)))
+            return 0;
+        return -1;
+    }
+
+    size_t num_blocks_in_page =
+        (PAGE_SIZE - sizeof(struct bucket)) / buck->block_size;
+    size_t maplength = (num_blocks_in_page + 7)
+        / 8; // +7 for ceiling division (oui c'est moche mais ça marche)
+
+    // Foreach byte
     for (unsigned i = 0; i < maplength; i++)
     {
         unsigned char map_byte = buck->free_map[i];
-        unsigned char bit = 1;
+        if (map_byte == 0xFF) // Skip if used
-        // Test byte
+            continue;
-        for (unsigned j = 0; j < 8; j <<= 1)
-        {
-            if (map_byte ^ bit) // Test if free
-                return i * 8 + j;
 
-            bit <<= 1;
+        for (unsigned j = 0; j < 8; j++)
+        {
+            if ((i * 8 + j) < num_blocks_in_page
+                && !(map_byte & (1 << j))) // Check if free
+                return i * 8 + j;
         }
     }
 
@@ -68,11 +81,20 @@ int get_block_number(struct bucket *biquette, void *block)
         return -1;
 
     char *block_nul = block;
-    void *biquetteounette = biquette;
+    char *bibiche =
-    char *biquette_cherie = biquetteounette;
+        get_data_begin(biquette); // Célèbre bar Capcinois, venez à l'occasion
 
-    return (block_nul - biquette_cherie - sizeof(struct bucket))
+    return (block_nul - bibiche) / biquette->block_size;
-        / biquette->block_size;
+
+    // Au revoir mes belles
+    // Vous manquerez à papa
+    // (mais fallait marcher, là ça marche pas)
+
+    // void *biquetteounette = biquette;
+    // char *biquette_cherie = biquetteounette;
+
+    // return (block_nul - biquette_cherie - sizeof(struct bucket))
+    //     / biquette->block_size;
 }
 
 // Gets a bucket with at least a block_size of size
@@ -93,7 +115,9 @@ struct bucket *get_bucket(struct bucket *head, size_t size)
 // Computes the buckets first block address
 void *get_data_begin(struct bucket *biquette)
 {
-    return biquette + sizeof(struct bucket);
+    void *maisqueltrucdemerde = biquette;
+    char *biquettas = maisqueltrucdemerde;
+    return biquettas + sizeof(struct bucket);
 }
 
 // Computes the beginning address of the page containing ptr
@@ -130,7 +154,7 @@ void bucket_list_remove(struct bucket **head, struct bucket *elt)
 
     if (*head == elt)
     {
-        *head = NULL;
+        *head = elt->next;
         return;
     }
 

malloc/src/malloc.c

@@ -28,7 +28,8 @@ __attribute__((visibility("default"))) void *malloc(size_t size)
 
     buck = create_bucket(size);
     bucket_list_append(&head, buck);
-    return allocate_block(buck, 1);
+    int first_free_buche = find_free_block(buck); // De noel (pas la mienne)
+    return allocate_block(buck, first_free_buche);
 }
 
 __attribute__((visibility("default"))) void free(void *ptr)
@@ -56,6 +57,8 @@ __attribute__((visibility("default"))) void *realloc(void *ptr, size_t size)
     else
     {
         void *new_ptr = malloc(size);
+        if (new_ptr == NULL)
+            return NULL;
         memcpy(new_ptr, ptr, header->block_size);
         free(ptr);
         return new_ptr;
@@ -66,7 +69,14 @@ __attribute__((visibility("default"))) void *realloc(void *ptr, size_t size)
 
 __attribute__((visibility("default"))) void *calloc(size_t nmemb, size_t size)
 {
-    char *res = malloc(nmemb * size);
+    // Check overflow
+    size_t c;
+    if (__builtin_mul_overflow(nmemb, size, &c))
+        return NULL;
+
+    char *res = malloc(c);
+    if (res == NULL)
+        return NULL;
     memset(res, 0, nmemb * size);
     return res;
 }

malloc/tests/test-cmd.sh

@@ -15,7 +15,7 @@ LD_PRELOAD=./libmalloc.so ls 1> /dev/null
 check
 LD_PRELOAD=./libmalloc.so ip a 1> /dev/null
 check
-LD_PRELOAD=./libmalloc.so grep 1> /dev/null
+LD_PRELOAD=./libmalloc.so grep --help 1> /dev/null
 check
 LD_PRELOAD=./libmalloc.so find 1> /dev/null
 check