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tcmalloc page fences: add TCMALLOC_PAGE_FENCE_READABLE option

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Robert Scott 2020-02-22 18:55:46 +00:00 committed by Aliaksey Kandratsenka
parent d57a9ea8bc
commit 43504ab709
1 changed files with 6 additions and 1 deletions
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7
src/debugallocation.cc
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@ -112,6 +112,9 @@ DEFINE_bool(malloc_page_fence_never_reclaim,
EnvToBool("TCMALLOC_PAGE_FENCE_NEVER_RECLAIM", false),
"Enables making the virtual address space inaccessible "
"upon a deallocation instead of returning it and reusing later.");
DEFINE_bool(malloc_page_fence_readable,
EnvToBool("TCMALLOC_PAGE_FENCE_READABLE", false),
"Permits reads to the page fence.");
#else
DEFINE_bool(malloc_page_fence, false, "Not usable (requires mmap)");
DEFINE_bool(malloc_page_fence_never_reclaim, false, "Not usable (required mmap)");
@ -508,6 +511,7 @@ class MallocBlock {
}
MallocBlock* b = NULL;
const bool use_malloc_page_fence = FLAGS_malloc_page_fence;
const bool malloc_page_fence_readable = FLAGS_malloc_page_fence_readable;
#ifdef HAVE_MMAP
if (use_malloc_page_fence) {
// Put the block towards the end of the page and make the next page
@ -526,7 +530,8 @@ class MallocBlock {
strerror(errno));
}
// Mark the page after the block inaccessible
if (mprotect(p + (num_pages - 1) * pagesize, pagesize, PROT_NONE)) {
if (mprotect(p + (num_pages - 1) * pagesize, pagesize,
PROT_NONE|(malloc_page_fence_readable ? PROT_READ : 0))) {
RAW_LOG(FATAL, "Guard page setup failed: %s", strerror(errno));
}
b = (MallocBlock*) (p + (num_pages - 1) * pagesize - sz);