only use reserved memory for regions hash table
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c3a4829d77
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e93d039214
@ -72,7 +72,9 @@ allocation and then unmapped on free.
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* [in-progress] Some slab locations are skipped and remain memory protected,
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leaving slab size class regions interspersed with guard pages
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* Zero size allocations are memory protected
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* [mostly in-progress] Protected allocator metadata
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* Protected allocator metadata
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* Address space for metadata is never used for allocations and vice versa
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* [implementing stronger protection is in-progress]
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* Extension for retrieving the size of allocations with fallback
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to a sentinel for pointers not managed by the allocator
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* Can also return accurate values for pointers *within* small allocations
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26
malloc.c
26
malloc.c
@ -104,6 +104,7 @@ static union {
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struct {
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void *slab_region_start;
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void *slab_region_end;
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struct region_info *regions[2];
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atomic_bool initialized;
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};
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char padding[PAGE_SIZE];
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@ -502,6 +503,7 @@ struct region_info {
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};
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static const size_t initial_region_table_size = 256;
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static const size_t max_region_table_size = class_region_size / PAGE_SIZE;
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static struct random_state regions_rng;
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static struct region_info *regions;
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@ -527,8 +529,14 @@ static int regions_grow(void) {
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size_t newsize = newtotal * sizeof(struct region_info);
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size_t mask = newtotal - 1;
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struct region_info *p = allocate_pages(newsize, PAGE_SIZE, true);
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if (p == NULL) {
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if (newtotal > max_region_table_size) {
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return 1;
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}
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struct region_info *p = regions == ro.regions[0] ?
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ro.regions[1] : ro.regions[0];
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if (memory_protect_rw(p, newsize)) {
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return 1;
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}
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@ -543,7 +551,7 @@ static int regions_grow(void) {
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}
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}
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deallocate_pages(regions, regions_total * sizeof(struct region_info), PAGE_SIZE);
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memory_map_fixed(regions, regions_total * sizeof(struct region_info));
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regions_free = regions_free + regions_total;
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regions_total = newtotal;
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regions = p;
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@ -656,9 +664,15 @@ COLD static void init_slow_path(void) {
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struct random_state rng;
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random_state_init(&rng);
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regions = allocate_pages(regions_total * sizeof(struct region_info), PAGE_SIZE, true);
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if (regions == NULL) {
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fatal_error("failed to set up allocator");
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for (unsigned i = 0; i < 2; i++) {
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ro.regions[i] = allocate_pages(max_region_table_size, PAGE_SIZE, false);
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if (ro.regions[i] == NULL) {
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fatal_error("failed to reserve memory for regions table");
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}
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}
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regions = ro.regions[0];
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if (memory_protect_rw(regions, regions_total * sizeof(struct region_info))) {
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fatal_error("failed to unprotect memory for regions table");
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}
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random_state_init(®ions_rng);
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