mirrors/mimalloc
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

ensure addresses of large aligned allocations are randomized

Browse Source
This commit is contained in:
daan 2019-09-06 09:19:26 -07:00
parent 1a7b1783fa
commit f38fcf79eb
1 changed files with 48 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

74
src/os.c
View File

@ -193,6 +193,8 @@ static bool mi_os_mem_free(void* addr, size_t size, bool was_committed, mi_stats
}
}
static void* mi_os_get_aligned_hint(size_t try_alignment, size_t size);
#ifdef _WIN32
static void* mi_win_virtual_allocx(void* addr, size_t size, size_t try_alignment, DWORD flags) {
#if defined(MEM_EXTENDED_PARAMETER_TYPE_BITS)
@ -221,19 +223,10 @@ static void* mi_win_virtual_allocx(void* addr, size_t size, size_t try_alignment
}
#endif
#if (MI_INTPTR_SIZE >= 8)
// on 64-bit systems, use the virtual address area after 4TiB for 4MiB aligned allocations
#define MI_HINT_START ((intptr_t)4 << 40)
static volatile _Atomic(intptr_t) aligned_base = ATOMIC_VAR_INIT(MI_HINT_START); // starting at 4TiB
if (addr == NULL && try_alignment > 0 &&
try_alignment <= MI_SEGMENT_SIZE && (size%MI_SEGMENT_SIZE) == 0)
{
intptr_t hint = mi_atomic_add(&aligned_base, size);
if (hint > ((intptr_t)30<<40)) { // try to wrap around after 30TiB (area after 32TiB is used for huge OS pages)
mi_atomic_cas_strong(mi_atomic_cast(uintptr_t,&aligned_base),MI_HINT_START,hint + size);
}
if (hint%try_alignment == 0) {
return VirtualAlloc((void*)hint, size, flags, PAGE_READWRITE);
}
// on 64-bit systems, try to use the virtual address area after 4TiB for 4MiB aligned allocations
void* hint;
if (addr == NULL && (hint = mi_os_get_aligned_hint(try_alignment,size)) != NULL) {
return VirtualAlloc(hint, size, flags, PAGE_READWRITE);
}
#endif
#if defined(MEM_EXTENDED_PARAMETER_TYPE_BITS)
@ -302,17 +295,10 @@ static void* mi_unix_mmapx(void* addr, size_t size, size_t try_alignment, int pr
void* p = NULL;
#if (MI_INTPTR_SIZE >= 8) && !defined(MAP_ALIGNED)
// on 64-bit systems, use the virtual address area after 4TiB for 4MiB aligned allocations
#define MI_HINT_START ((intptr_t)4 << 40)
static volatile _Atomic(intptr_t) aligned_base = ATOMIC_VAR_INIT(MI_HINT_START); // starting at 4TiB
if (addr==NULL && try_alignment <= MI_SEGMENT_SIZE && (size%MI_SEGMENT_SIZE)==0) {
intptr_t hint = mi_atomic_add(&aligned_base,size);
if (hint > ((intptr_t)30<<40)) { // try to wrap around after 30TiB (area after 32TiB is used for huge OS pages)
mi_atomic_cas_strong(mi_atomic_cast(uintptr_t,&aligned_base), MI_HINT_START, hint + size);
}
if (hint%try_alignment == 0) {
p = mmap((void*)hint,size,protect_flags,flags,fd,0);
if (p==MAP_FAILED) p = NULL; // fall back to regular mmap
}
void* hint;
if (addr == NULL && (hint = mi_os_get_aligned_hint(try_alignment, size)) != NULL) {
p = mmap(hint,size,protect_flags,flags,fd,0);
if (p==MAP_FAILED) p = NULL; // fall back to regular mmap
}
#else
UNUSED(try_alignment);
@ -420,6 +406,36 @@ static void* mi_unix_mmap(void* addr, size_t size, size_t try_alignment, int pro
}
#endif
// On 64-bit systems, we can do efficient aligned allocation by using
// the 4TiB to 30TiB area to allocate them.
#if (MI_INTPTR_SIZE >= 8) && (defined(_WIN32) || (defined(MI_OS_USE_MMAP) && !defined(MAP_ALIGNED)))
static volatile _Atomic(intptr_t) aligned_base;
// Return a 4MiB aligned address that is probably available
static void* mi_os_get_aligned_hint(size_t try_alignment, size_t size) {
if (try_alignment == 0 || try_alignment > MI_SEGMENT_SIZE) return NULL;
if ((size%MI_SEGMENT_SIZE) != 0) return NULL;
intptr_t hint = mi_atomic_add(&aligned_base, size);
if (hint == 0 || hint > ((intptr_t)30<<40)) { // try to wrap around after 30TiB (area after 32TiB is used for huge OS pages)
intptr_t init = ((intptr_t)4 << 40); // start at 4TiB area
#if (MI_SECURE>0 || MI_DEBUG==0) // security: randomize start of aligned allocations unless in debug mode
uintptr_t r = _mi_random_init((uintptr_t)&mi_os_get_aligned_hint ^ hint);
init = init + (MI_SEGMENT_SIZE * ((r>>17) & 0xFFFF)); // (randomly 0-64k)*4MiB == 0 to 256GiB
#endif
mi_atomic_cas_strong(mi_atomic_cast(uintptr_t, &aligned_base), init, hint + size);
hint = mi_atomic_add(&aligned_base, size); // this may still give 0 or > 30TiB but that is ok, it is a hint after all
}
if (hint%try_alignment != 0) return NULL;
return (void*)hint;
}
#else
static void* mi_os_get_aligned_hint(size_t try_alignment, size_t size) {
UNUSED(try_alignment); UNUSED(size);
return NULL;
}
#endif
// Primitive allocation from the OS.
// Note: the `try_alignment` is just a hint and the returned pointer is not guaranteed to be aligned.
static void* mi_os_mem_alloc(size_t size, size_t try_alignment, bool commit, bool allow_large, bool* is_large, mi_stats_t* stats) {
@ -850,10 +866,16 @@ int mi_reserve_huge_os_pages( size_t pages, double max_secs, size_t* pages_reser
if (pages==0) return 0; // ok
if (!mi_atomic_cas_ptr_strong(&os_huge_reserved.start,(void*)1,NULL)) return ETIMEDOUT; // already reserved
// Set the start address after the 32TiB area
uint8_t* start = (uint8_t*)((uintptr_t)32 << 40); // 32TiB virtual start address
#if (MI_SECURE>0 || MI_DEBUG==0) // security: randomize start of huge pages unless in debug mode
uintptr_t r = _mi_random_init((uintptr_t)&mi_reserve_huge_os_pages);
start = start + ((uintptr_t)MI_SEGMENT_SIZE * ((r>>17) & 0xFFFF)); // (randomly 0-64k)*4MiB == 0 to 256GiB
#endif
// Allocate one page at the time but try to place them contiguously
// We allocate one page at the time to be able to abort if it takes too long
double start_t = _mi_clock_start();
uint8_t* start = (uint8_t*)((uintptr_t)32 << 40); // 32TiB virtual start address
uint8_t* addr = start; // current top of the allocations
for (size_t page = 0; page < pages; page++, addr += MI_HUGE_OS_PAGE_SIZE ) {
// allocate a page
@ -886,7 +908,7 @@ int mi_reserve_huge_os_pages( size_t pages, double max_secs, size_t* pages_reser
}
// success, record it
if (page==0) {
mi_atomic_write_ptr(&os_huge_reserved.start, addr);
mi_atomic_write_ptr(&os_huge_reserved.start, addr); // don't switch the order of these writes
mi_atomic_write(&os_huge_reserved.reserved, MI_HUGE_OS_PAGE_SIZE);
}
else {