1// Test that tagging a large region to 0 reduces RSS.
2// RUN: %clang_hwasan -mllvm -hwasan-globals=0 -mllvm -hwasan-instrument-stack=0 %s -o %t && %run %t 2>&1
3
4// REQUIRES: pointer-tagging
5
6#include <assert.h>
7#include <fcntl.h>
8#include <stdio.h>
9#include <stdlib.h>
10#include <sys/auxv.h>
11#include <sys/mman.h>
12#include <sys/stat.h>
13#include <sys/types.h>
14#include <unistd.h>
15
16#include <sanitizer/hwasan_interface.h>
17
18const unsigned char kTag = 42;
19const size_t kNumShadowPages = 1024;
20const size_t kNumPages = 16 * kNumShadowPages;
21
22size_t page_size, map_size;
23
24void sync_rss() {
25 char *page = (char *)mmap(addr: 0, len: page_size, PROT_READ | PROT_WRITE,
26 MAP_PRIVATE | MAP_ANONYMOUS, fd: 0, offset: 0);
27 // Linux kernel updates RSS counters after a set number of page faults.
28 for (int i = 0; i < 100; ++i) {
29 page[0] = 42;
30 madvise(addr: page, len: page_size, MADV_DONTNEED);
31 }
32 munmap(addr: page, len: page_size);
33}
34
35size_t current_rss() {
36 sync_rss();
37 int statm_fd = open(file: "/proc/self/statm", O_RDONLY);
38 assert(statm_fd >= 0);
39
40 char buf[100];
41 assert(read(statm_fd, &buf, sizeof(buf)) > 0);
42 size_t size, rss;
43 assert(sscanf(buf, "%zu %zu", &size, &rss) == 2);
44
45 close(fd: statm_fd);
46 return rss;
47}
48
49int test_rss_difference(void *p) {
50 __hwasan_tag_memory(p, tag: kTag, size: map_size);
51 size_t rss_before = current_rss();
52 __hwasan_tag_memory(p, tag: 0, size: map_size);
53 size_t rss_after = current_rss();
54 fprintf(stderr, format: "%zu -> %zu\n", rss_before, rss_after);
55 if (rss_before <= rss_after)
56 return 0;
57 size_t diff = rss_before - rss_after;
58 fprintf(stderr, format: "diff %zu\n", diff);
59 // Check that the difference is at least close to kNumShadowPages.
60 return diff > kNumShadowPages / 2;
61}
62
63int main() {
64 page_size = getauxval(AT_PAGESZ);
65 map_size = kNumPages * page_size;
66
67 fprintf(stderr, format: "starting rss %zu\n", current_rss());
68 fprintf(stderr, format: "shadow pages: %zu\n", kNumShadowPages);
69
70 void *p = mmap(addr: 0, len: map_size, PROT_READ | PROT_WRITE,
71 MAP_PRIVATE | MAP_ANONYMOUS, fd: 0, offset: 0);
72 fprintf(stderr, format: "p = %p\n", p);
73
74 size_t total_count = 10;
75 size_t success_count = 0;
76 for (size_t i = 0; i < total_count; ++i)
77 success_count += test_rss_difference(p);
78
79 fprintf(stderr, format: "p = %p\n", p);
80 fprintf(stderr, format: "passed %zu out of %zu\n", success_count, total_count);
81 assert(success_count > total_count * 0.8);
82
83 return 0;
84}
85

source code of compiler-rt/test/hwasan/TestCases/Linux/release-shadow.c