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// Test that tagging a large region to 0 reduces RSS.
// RUN: %clang_hwasan -mllvm -hwasan-instrument-stack=0 %s -o %t && %run %t 2>&1
#include <assert.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <sanitizer/hwasan_interface.h>
const unsigned char kTag = 42;
const size_t kNumShadowPages = 256;
const size_t kNumPages = 16 * kNumShadowPages;
const size_t kPageSize = 4096;
const size_t kMapSize = kNumPages * kPageSize;
void sync_rss() {
char *page = (char *)mmap(0, kPageSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
// Linux kernel updates RSS counters after a set number of page faults.
for (int i = 0; i < 1000; ++i) {
page[0] = 42;
madvise(page, kPageSize, MADV_DONTNEED);
}
munmap(page, kPageSize);
}
size_t current_rss() {
sync_rss();
int statm_fd = open("/proc/self/statm", O_RDONLY);
assert(statm_fd >= 0);
char buf[100];
assert(read(statm_fd, &buf, sizeof(buf)) > 0);
size_t size, rss;
assert(sscanf(buf, "%zu %zu", &size, &rss) == 2);
close(statm_fd);
return rss;
}
void test_rss_difference(void *p) {
__hwasan_tag_memory(p, kTag, kMapSize);
size_t rss_before = current_rss();
__hwasan_tag_memory(p, 0, kMapSize);
size_t rss_after = current_rss();
fprintf(stderr, "%zu -> %zu\n", rss_before, rss_after);
assert(rss_before > rss_after);
size_t diff = rss_before - rss_after;
fprintf(stderr, "diff %zu\n", diff);
// Check that the difference is at least close to kNumShadowPages.
assert(diff > kNumShadowPages / 4 * 3);
}
int main() {
fprintf(stderr, "starting rss %zu\n", current_rss());
fprintf(stderr, "shadow pages: %zu\n", kNumShadowPages);
void *p = mmap(0, kMapSize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
fprintf(stderr, "p = %p\n", p);
test_rss_difference(p);
test_rss_difference(p);
test_rss_difference(p);
return 0;
}
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