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LibC: Also mark empty-but-kept-around BigAllocationBlocks as PROT_NONE

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This extends the opportunistic protection of empty-but-kept-around to
also cover BigAllocationBlocks. Since we only cache 4KB BAB's at the
moment, this sees limited use, but it does work.
This commit is contained in:
Andreas Kling 2019-12-02 19:59:53 +01:00
parent 05c65fb4f1
commit d422c46ebb
1 changed files with 10 additions and 0 deletions
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10
Libraries/LibC/malloc.cpp
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@ -161,6 +161,11 @@ void* malloc(size_t size)
if (auto* allocator = big_allocator_for_size(real_size)) { if (auto* allocator = big_allocator_for_size(real_size)) {
if (!allocator->blocks.is_empty()) { if (!allocator->blocks.is_empty()) {
auto* block = allocator->blocks.take_last(); auto* block = allocator->blocks.take_last();
if (mprotect(block, real_size, PROT_READ | PROT_WRITE) < 0) {
perror("mprotect");
ASSERT_NOT_REACHED();
}
set_mmap_name(block, PAGE_SIZE, "malloc: BigAllocationBlock (reused)");
return &block->m_slot[0]; return &block->m_slot[0];
} }
} }
@ -236,6 +241,11 @@ void free(void* ptr)
if (auto* allocator = big_allocator_for_size(block->m_size)) { if (auto* allocator = big_allocator_for_size(block->m_size)) {
if (allocator->blocks.size() < number_of_big_blocks_to_keep_around_per_size_class) { if (allocator->blocks.size() < number_of_big_blocks_to_keep_around_per_size_class) {
allocator->blocks.append(block); allocator->blocks.append(block);
set_mmap_name(block, PAGE_SIZE, "malloc: BigAllocationBlock (free)");
if (mprotect(block, PAGE_SIZE, PROT_NONE) < 0) {
perror("mprotect");
ASSERT_NOT_REACHED();
}
return; return;
} }
} }