scripts

commit fcacada2e7f64a6bee74dec823fd82377e16e170
parent 4a6c259f4a924d5fc7ad60fa7ee742037e194e47
Author: sin <sin@2f30.org>
Date:   Tue, 30 Jul 2013 10:35:51 +0100

Use mmap() instead of sbrk()

Diffstat:
M
alloc.c
 | 
32
+++++++++++++++++++++++++++++---

1 file changed, 29 insertions(+), 3 deletions(-)
diff --git a/alloc.c b/alloc.c
@@ -1,3 +1,4 @@
+#include <sys/mman.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -10,7 +11,7 @@ enum chunk_state {
 
 /* A maximum of `NALLOC' allocations possible */
 enum {
-	NALLOC = 65536 * 64,
+	NALLOC = 65536 * 128,
 };
 
 /* Only needed because we have to implement
@@ -22,6 +23,29 @@ struct chunk {
 } chunks[NALLOC];
 
 void *
+mmap_page_aligned(size_t nbytes)
+{
+	void *addr;
+	int ret;
+
+	if (nbytes % 0x1000)
+		nbytes = (nbytes + 0x1000) & ~(0x1000 - 1);
+
+	addr = mmap(0, nbytes + 0x1000,
+		    PROT_READ | PROT_WRITE,
+		    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (addr == MAP_FAILED)
+		return NULL;
+	ret = mprotect((char *)addr + nbytes, 0x1000,
+		       PROT_NONE);
+	if (ret < 0) {
+		munmap(addr, nbytes + 0x1000);
+		return NULL;
+	}
+	return addr;
+}
+
+void *
 malloc(size_t nbytes)
 {
 	void *p;
@@ -29,8 +53,8 @@ malloc(size_t nbytes)
 
 	if (!nbytes)
 		return NULL;
-	p = sbrk(nbytes);
-	if (p == (void *)-1)
+	p = mmap_page_aligned(nbytes);
+	if (!p)
 		return NULL;
 	for (i = 0; i < NALLOC; i++) {
 		if (chunks[i].state == FREE) {
@@ -62,6 +86,7 @@ realloc(void *oldp, size_t nbytes)
 			n = chunks[i].size < nbytes ? chunks[i].size : nbytes;
 			memcpy(p, chunks[i].base, n);
 			chunks[i].state = FREE;
+			munmap(chunks[i].base, chunks[i].size + 0x1000);
 			return p;
 		}
 	}
@@ -90,6 +115,7 @@ free(void *p)
 	for (i = 0; i < NALLOC; i++) {
 		if (chunks[i].base == p) {
 			chunks[i].state = FREE;
+			munmap(chunks[i].base, chunks[i].size + 0x1000);
 			break;
 		}
 	}