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authorJakob Kaivo <jkk@ung.org>2020-06-30 13:18:23 -0400
committerJakob Kaivo <jkk@ung.org>2020-06-30 13:18:23 -0400
commitbd7dee4575e43e097abc1f129179c61869c3fce9 (patch)
treea2cbe325e300de15a882b0b9e9540c9b009b7309 /src
parent49ad475df150584a9e59649b48dec1f3bed2bffb (diff)
extract page_alloc() so it can be reused by get_bucket()
Diffstat (limited to 'src')
-rw-r--r--src/mapalloc.c99
1 files changed, 71 insertions, 28 deletions
diff --git a/src/mapalloc.c b/src/mapalloc.c
index 5becc59..0744ebf 100644
--- a/src/mapalloc.c
+++ b/src/mapalloc.c
@@ -28,9 +28,44 @@ struct bucket {
size_t allocated;
};
-static struct bucket *get_bucket(void *ptr)
+static void *page_alloc(size_t npages)
{
+ int fd = -1;
+ int prot = PROT_READ | PROT_WRITE;
+ int flags = MAP_PRIVATE;
+
+ #ifdef MAP_ANONYMOUS
+ flags = MAP_ANONYMOUS;
+ #else
+ fd = open("/dev/zero", O_RDONLY);
+ #endif
+
+ void *pages = mmap(NULL, npages * PAGESIZE, prot, flags, fd, 0);
+
+ if (fd != -1) {
+ close(fd);
+ }
+
+ return pages;
+}
+
+static struct bucket *get_bucket(void *ptr, int allocate)
+{
+ static uintptr_t *trie_top = NULL;
+ if (trie_top == NULL) {
+ trie_top = page_alloc(1);
+ }
+
+ uintptr_t *trie = trie_top;
uintptr_t addr = (uintptr_t)ptr;
+ for (size_t i = 0; i < sizeof(addr); i++) {
+ if (trie == NULL && allocate == 0) {
+ return NULL;
+ }
+
+ uintptr_t next = (addr >> (i * CHAR_BIT)) & UCHAR_MAX;
+ trie = (uintptr_t*)trie[next];
+ }
return addr ? NULL : NULL;
}
@@ -46,38 +81,22 @@ void *map_calloc(size_t nelem, size_t elsize)
return ptr;
}
-void *map_malloc(size_t n)
+void *map_malloc(size_t nbytes)
{
- int fd = -1;
- int prot = PROT_READ | PROT_WRITE;
- int flags = MAP_PRIVATE;
-
- size_t alloc = n;
- if (n % PAGESIZE != 0) {
- alloc += PAGESIZE - (n % PAGESIZE);
+ size_t pages = 2 + (nbytes / PAGESIZE);
+ if (nbytes % PAGESIZE != 0) {
+ pages++;
}
- alloc += 2 * PAGESIZE;
-
- #ifdef MAP_ANONYMOUS
- flags = MAP_ANONYMOUS;
- #else
- fd = open("/dev/zero", O_RDONLY);
- #endif
- /* declare as char* so simple pointer arithmetic is possible */
- char *ptr = mmap(NULL, alloc, prot, flags, fd, 0);
-
- if (fd != -1) {
- close(fd);
- }
+ char *ptr = page_alloc(pages);
mprotect(ptr, PAGESIZE, PROT_NONE);
- mprotect(ptr + alloc - PAGESIZE, PAGESIZE, PROT_NONE);
+ mprotect(ptr + ((pages - 1) * PAGESIZE), PAGESIZE, PROT_NONE);
/*
- struct bucket *b = get_bucket(ptr);
- b->used = n;
- b->allocated = alloc;
+ struct bucket *b = get_bucket(ptr, 1);
+ b->used = nbytes;
+ b->allocated = pages * PAGESIZE;
*/
return ptr + PAGESIZE;
@@ -88,7 +107,25 @@ void *map_realloc(void *ptr, size_t n)
if (ptr == NULL) {
return map_malloc(n);
}
- return NULL;
+
+ struct bucket *b = get_bucket(ptr, 0);
+ if (b == NULL) {
+ fprintf(stderr, "attempt to realloc() invalid pointer %p\n", ptr);
+ abort();
+ }
+
+ if (n < (b->allocated - (PAGESIZE * 2))) {
+ b->used = n;
+ /* munmap() and mprotect() as necessary */
+ return ptr;
+ }
+
+ void *newptr = map_malloc(n);
+ if (newptr != NULL) {
+ memcpy(newptr, ptr, n);
+ map_free(ptr);
+ }
+ return newptr;
}
void map_free(void *ptr)
@@ -97,9 +134,15 @@ void map_free(void *ptr)
return;
}
- struct bucket *b = get_bucket(ptr);
+ struct bucket *b = get_bucket(ptr, 0);
if (b == NULL) {
fprintf(stderr, "attempt to free() invalid pointer %p\n", ptr);
abort();
}
+
+ char *base = ptr;
+ base -= PAGESIZE;
+ munmap(base, b->allocated);
+
+ /* clear bucket */
}