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[msan] Change track-origins default mode from 1 to 2. 

Change -fsanitize-memory-track-origins to be equivalent to
-fsanitize-memory-track-origins=2.

Track-origins=2 provides a lot more detailed reports at the cost of
some additional slowdown (ranging from none to, sometimes, 3x; ~3% average on
SPEC2006).

llvm-svn: 230644
This commit is contained in:
Evgeniy Stepanov 2015-02-26 15:59:30 +00:00
parent 0b57fc3147
commit 6e09bca0ef
4 changed files with 23 additions and 31 deletions
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33
clang/docs/MemorySanitizer.rst
View File

@ -110,30 +110,10 @@ Origin Tracking
MemorySanitizer can track origins of unitialized values, similar to
Valgrind's --track-origins option. This feature is enabled by
``-fsanitize-memory-track-origins`` Clang option. With the code from
``-fsanitize-memory-track-origins=2`` (or simply
``-fsanitize-memory-track-origins``) Clang option. With the code from
the example above,
.. code-block:: console
% clang -fsanitize=memory -fsanitize-memory-track-origins -fno-omit-frame-pointer -g -O2 umr.cc
% ./a.out
WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x7f7893912f0b in main umr2.cc:6
#1 0x7f789249b76c in __libc_start_main libc-start.c:226
Uninitialized value was created by a heap allocation
#0 0x7f7893901cbd in operator new[](unsigned long) msan_new_delete.cc:44
#1 0x7f7893912e06 in main umr2.cc:4
Origin tracking has proved to be very useful for debugging MemorySanitizer
reports. It slows down program execution by a factor of 1.5x-2x on top
of the usual MemorySanitizer slowdown.
MemorySanitizer can provide even more information with
``-fsanitize-memory-track-origins=2`` flag. In this mode reports
include information about intermediate stores the uninitialized value went
through.
.. code-block:: console
% cat umr2.cc
@ -162,6 +142,15 @@ through.
#0 0x7f7893901cbd in operator new[](unsigned long) msan_new_delete.cc:44
#1 0x7f7893912e06 in main umr2.cc:4
By default, MemorySanitizer collects both allocation points and all
intermediate stores the uninitialized value went through. Origin
tracking has proved to be very useful for debugging MemorySanitizer
reports. It slows down program execution by a factor of 1.5x-2x on top
of the usual MemorySanitizer slowdown.
Clang option ``-fsanitize-memory-track-origins=1`` enabled a slightly
faster mode when MemorySanitizer collects only allocation points but
not intermediate stores.
Handling external code
============================

9
clang/docs/UsersManual.rst
View File

@ -1030,10 +1030,11 @@ are listed below.
uninitialized bits came from. Slows down execution by additional
1.5x-2x.
Possible values for level are 0 (off), 1 (default), 2. Level 2 adds more
sections to MemorySanitizer reports describing the order of memory stores
the uninitialized value went through. Beware, this mode may use a lot of
extra memory.
Possible values for level are 0 (off), 1, 2 (default). Level 2
adds more sections to MemorySanitizer reports describing the
order of memory stores the uninitialized value went
through. This mode may use extra memory in programs that copy
uninitialized memory a lot.
Extra features of UndefinedBehaviorSanitizer:

2
clang/lib/Driver/SanitizerArgs.cpp
View File

@ -360,7 +360,7 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
options::OPT_fsanitize_memory_track_origins,
options::OPT_fno_sanitize_memory_track_origins)) {
if (A->getOption().matches(options::OPT_fsanitize_memory_track_origins)) {
MsanTrackOrigins = 1;
MsanTrackOrigins = 2;
} else if (A->getOption().matches(
options::OPT_fno_sanitize_memory_track_origins)) {
MsanTrackOrigins = 0;

10
clang/test/Driver/fsanitize.c
View File

@ -66,11 +66,13 @@
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -pie %s -### 2>&1
// OK
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-1
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-2
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins=1 -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-1
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins=2 -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-1
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fno-sanitize-memory-track-origins -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-1
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins=0 -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-1
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins=1 -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-2
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins=2 -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-2
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fno-sanitize-memory-track-origins -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-2
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins=0 -fsanitize-memory-track-origins=1 -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-1
// RUN: %clang -target x86_64-linux-gnu -fsanitize=memory -fsanitize-memory-track-origins=0 -fsanitize-memory-track-origins -pie %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-TRACK-ORIGINS-2
// CHECK-TRACK-ORIGINS-1: -fsanitize-memory-track-origins=1