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better handling of mmap() with MAP_FIXED or address hint

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This commit is contained in:
Don Porter
2017-01-28 09:21:23 -05:00
parent 5a5a7e4eb5
commit c0830fbc03
1 changed files with 25 additions and 7 deletions
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LibOS/shim/src/sys/shim_mmap.c
+25 -7
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@@ -45,6 +45,10 @@ void * shim_do_mmap (void * addr, size_t length, int prot, int flags, int fd,
long ret = -ENOMEM;
bool reserved = false;
if (addr + length < addr) {
return (void *) -EINVAL;
}
assert(!(flags & (VMA_UNMAPPED|VMA_TAINTED)));
if (flags & MAP_32BIT)
@@ -52,15 +56,29 @@ void * shim_do_mmap (void * addr, size_t length, int prot, int flags, int fd,
int pal_alloc_type = 0;
if (!addr) {
addr = get_unmapped_vma(ALIGN_UP(length), flags);
if (addr)
reserved = true;
if ((flags & MAP_FIXED) && (addr != NULL)) {
struct shim_vma * tmp = NULL;
if (lookup_overlap_vma(addr, length, &tmp) == 0) {
debug("mmap: allowing overlapping MAP_FIXED allocation at %p with length %lu\n",
addr, length);
}
} else {
/* For calls without MAP_FIXED, don't even attempt to honor the
* caller's requested address. Such requests are likely to be assuming
* things about the address space that aren't valid in graphene. */
addr = NULL;
}
if (addr) {
void * cur_stack = current_stack();
assert(cur_stack < addr || cur_stack > addr + length);
if (!addr) {
addr = get_unmapped_vma(ALIGN_UP(length), flags);
if (addr) {
reserved = true;
// Approximate check only, to help root out bugs.
void * cur_stack = current_stack();
assert(cur_stack < addr || cur_stack > addr + length);
}
}
void * mapped = ALIGN_DOWN((void *) addr);