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hwasan: Collect ring buffer statistics and include in dev note. 

These statistics are intended to help us tune the scudo MTE
implementation.

Differential Revision: https://reviews.llvm.org/D79913
This commit is contained in:
Peter Collingbourne 2020-05-13 16:38:31 -07:00
parent 54a335a2f6
commit d2a26ad0dc
1 changed files with 38 additions and 10 deletions
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48
compiler-rt/lib/hwasan/hwasan_report.cpp
View File

@ -122,21 +122,43 @@ class Decorator: public __sanitizer::SanitizerCommonDecorator {
const char *Thread() { return Green(); }
};
// Returns the index of the rb element that matches tagged_addr (plus one),
// or zero if found nothing.
uptr FindHeapAllocation(HeapAllocationsRingBuffer *rb,
uptr tagged_addr,
HeapAllocationRecord *har) {
if (!rb) return 0;
static bool FindHeapAllocation(HeapAllocationsRingBuffer *rb, uptr tagged_addr,
HeapAllocationRecord *har, uptr *ring_index,
uptr *num_matching_addrs,
uptr *num_matching_addrs_4b) {
if (!rb) return false;
*num_matching_addrs = 0;
*num_matching_addrs_4b = 0;
for (uptr i = 0, size = rb->size(); i < size; i++) {
auto h = (*rb)[i];
if (h.tagged_addr <= tagged_addr &&
h.tagged_addr + h.requested_size > tagged_addr) {
*har = h;
return i + 1;
*ring_index = i;
return true;
}
// Measure the number of heap ring buffer entries that would have matched
// if we had only one entry per address (e.g. if the ring buffer data was
// stored at the address itself). This will help us tune the allocator
// implementation for MTE.
if (UntagAddr(h.tagged_addr) <= UntagAddr(tagged_addr) &&
UntagAddr(h.tagged_addr) + h.requested_size > UntagAddr(tagged_addr)) {
++*num_matching_addrs;
}
// Measure the number of heap ring buffer entries that would have matched
// if we only had 4 tag bits, which is the case for MTE.
auto untag_4b = [](uptr p) {
return p & ((1ULL << 60) - 1);
};
if (untag_4b(h.tagged_addr) <= untag_4b(tagged_addr) &&
untag_4b(h.tagged_addr) + h.requested_size > untag_4b(tagged_addr)) {
++*num_matching_addrs_4b;
}
}
return 0;
return false;
}
static void PrintStackAllocations(StackAllocationsRingBuffer *sa,
@ -309,7 +331,10 @@ void PrintAddressDescription(
hwasanThreadList().VisitAllLiveThreads([&](Thread *t) {
// Scan all threads' ring buffers to find if it's a heap-use-after-free.
HeapAllocationRecord har;
if (uptr D = FindHeapAllocation(t->heap_allocations(), tagged_addr, &har)) {
uptr ring_index, num_matching_addrs, num_matching_addrs_4b;
if (FindHeapAllocation(t->heap_allocations(), tagged_addr, &har,
&ring_index, &num_matching_addrs,
&num_matching_addrs_4b)) {
Printf("%s", d.Location());
Printf("%p is located %zd bytes inside of %zd-byte region [%p,%p)\n",
untagged_addr, untagged_addr - UntagAddr(har.tagged_addr),
@ -327,8 +352,11 @@ void PrintAddressDescription(
// Print a developer note: the index of this heap object
// in the thread's deallocation ring buffer.
Printf("hwasan_dev_note_heap_rb_distance: %zd %zd\n", D,
Printf("hwasan_dev_note_heap_rb_distance: %zd %zd\n", ring_index + 1,
flags()->heap_history_size);
Printf("hwasan_dev_note_num_matching_addrs: %zd\n", num_matching_addrs);
Printf("hwasan_dev_note_num_matching_addrs_4b: %zd\n",
num_matching_addrs_4b);
t->Announce();
num_descriptions_printed++;