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[asan] Move instrumented null-terminated strings to a special section, compiler-rt part 

On Darwin, simple C null-terminated constant strings normally end up in the __TEXT,__cstring section of the resulting Mach-O binary. When instrumented with ASan, these strings are transformed in a way that they cannot be in __cstring (the linker unifies the content of this section and strips extra NUL bytes, which would break instrumentation), and are put into a generic __const section. This breaks some of the tools that we have: Some tools need to scan all C null-terminated strings in Mach-O binaries, and scanning all the contents of __const has a large performance penalty. This patch instead introduces a special section, __asan_cstring which will now hold the instrumented null-terminated strings.

Differential Revision: https://reviews.llvm.org/D25026

llvm-svn: 285620
This commit is contained in:
Kuba Brecka 2016-10-31 18:52:32 +00:00
parent a28c9e8f09
commit bf6e7848a0
2 changed files with 23 additions and 2 deletions
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17
compiler-rt/test/asan/TestCases/Darwin/cstring_section.c Normal file
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@ -0,0 +1,17 @@
// Test that AddressSanitizer moves constant strings into a separate section.
// RUN: %clang_asan -c -o %t %s
// RUN: llvm-objdump -s %t | FileCheck %s
// Check that "Hello.\n" is in __asan_cstring and not in __cstring.
// CHECK: Contents of section __asan_cstring:
// CHECK: 48656c6c {{.*}} Hello.
// CHECK: Contents of section __const:
// CHECK-NOT: 48656c6c {{.*}} Hello.
// CHECK: Contents of section __cstring:
// CHECK-NOT: 48656c6c {{.*}} Hello.
int main(int argc, char *argv[]) {
argv[0] = "Hello.\n";
return 0;
}

8
compiler-rt/test/asan/TestCases/Darwin/odr-lto.cc
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@ -19,9 +19,11 @@ void putstest();
#if PART == 1
static const char *my_global = "test\n\00abc";
int main()
{
fputs("test\n", stderr);
fputs(my_global, stderr);
putstest();
fprintf(stderr, "Done.\n");
return 0;
@ -29,9 +31,11 @@ int main()
#else // PART == 1
static const char *my_other_global = "test\n\00abc";
void putstest()
{
fputs("test\n", stderr);
fputs(my_other_global, stderr);
}
#endif // PART == 1