From b4ed5b152505ed1dc46d2af083acb19053661787 Mon Sep 17 00:00:00 2001 From: Michael Pavone Date: Sun, 28 Jun 2015 10:12:37 -0700 Subject: Use mmap with a hint rather than sbrk for allocating executable memory within 32-bit displacement range of compiled code --- mem.c | 31 +++++++++---------------------- 1 file changed, 9 insertions(+), 22 deletions(-) (limited to 'mem.c') diff --git a/mem.c b/mem.c index d019c6f..cb3a047 100644 --- a/mem.c +++ b/mem.c @@ -8,33 +8,20 @@ #include #include #include + #include "mem.h" +#ifndef MAP_ANONYMOUS +#define MAP_ANONYMOUS MAP_ANON +#endif -/* void * alloc_code(size_t *size) { + //start at the 1GB mark to allow plenty of room for sbrk based malloc implementations + //while still keeping well within 32-bit displacement range for calling code compiled into the executable + static uint8_t *next = (uint8_t *)0x40000000; *size += PAGE_SIZE - (*size & (PAGE_SIZE - 1)); - return mmap(NULL, *size, PROT_EXEC | PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); -} -*/ - -/* -void * alloc_code(size_t *size) -{ - char * ret = malloc(*size); - char * base = (char *)(((intptr_t)ret) & (~(PAGE_SIZE-1))); - mprotect(base, (ret + *size) - base, PROT_EXEC | PROT_READ | PROT_WRITE); + uint8_t *ret = mmap(NULL, *size, PROT_EXEC | PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + next = ret + *size; return ret; } -*/ -void * alloc_code(size_t *size) -{ - *size += PAGE_SIZE - (*size & (PAGE_SIZE - 1)); - void * ret = sbrk(*size); - if (ret == ((void *)-1)) { - return NULL; - } - mprotect(ret, *size, PROT_EXEC | PROT_READ | PROT_WRITE); - return ret; -} -- cgit v1.2.3