[asan] Optimize strchr for strict_string_checks=false

Summary:
strchr interceptor does not need to call strlen if strict_string_checks is not
enabled. Unnecessary strlen calls affect python parser performance.

Reviewers: eugenis, kcc

Subscribers: llvm-commits, kubamracek

Differential Revision: https://reviews.llvm.org/D32264

llvm-svn: 300889

1 files changed, 36 insertions, 0 deletions

diff --git a/compiler-rt/test/asan/TestCases/Posix/strchr.c b/compiler-rt/test/asan/TestCases/Posix/strchr.c
new file mode 100644
index 00000000000..df854d79ec8
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/Posix/strchr.c
@@ -0,0 +1,36 @@
+// Test strchr for strict_string_checks=false does not look beyond necessary
+// char.
+// RUN: %clang_asan %s -o %t
+// RUN: %env_asan_opts=strict_string_checks=false %run %t 2>&1
+// RUN: %env_asan_opts=strict_string_checks=true not %run %t 2>&1 | FileCheck %s
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+int main(int argc, char **argv) {
+  size_t page_size = sysconf(_SC_PAGE_SIZE);
+  size_t size = 2 * page_size;
+  char *s = (char *)mmap(0, size, PROT_READ | PROT_WRITE,
+                         MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+  assert(s);
+  assert(((uintptr_t)s & (page_size - 1)) == 0);
+  memset(s, 'o', size);
+  s[size - 1] = 0;
+
+  char *p = s + page_size - 1;
+  *p = 'x';
+
+  if (mprotect(p + 1, 1, PROT_NONE))
+    return 1;
+  char *r = strchr(s, 'x');
+  // CHECK: AddressSanitizer: SEGV on unknown address
+  // CHECK: The signal is caused by a READ memory access
+  // CHECK: strchr.c:[[@LINE-3]]
+  assert(r == p);
+
+  return 0;
+}