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Merge pull request #12663 from mrc0mmand/clang-asan-improvements

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test: improve handling of ASan under clang
This commit is contained in:
Evgeny Vereshchagin
2019-05-27 19:59:53 +03:00
committed by GitHub
parent 2fc1afca59 c9a95378ec
commit 75e4c768e2
3 changed files with 148 additions and 4 deletions
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docs/CODE_QUALITY.md
+5
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@@ -64,5 +64,10 @@ available functionality:
of active alerts can be found
[here](https://lgtm.com/projects/g/systemd/systemd/alerts/?mode=list).
15. Each PR is automatically tested with [Address Sanitizer](https://clang.llvm.org/docs/AddressSanitizer.html)
and [Undefined Behavior Sanitizer](https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html).
See [Testing systemd using sanitizers](https://systemd.io/TESTING_WITH_SANITIZERS)
for more information.
Access to Coverity and oss-fuzz reports is limited. Please reach out to the
maintainers if you need access.
docs/TESTING_WITH_SANITIZERS.md
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@@ -0,0 +1,88 @@
---
title: Testing systemd using sanitizers
---
# Testing systemd using sanitizers
To catch the *nastier* kind of bugs, you can run your code with [Address Sanitizer](https://clang.llvm.org/docs/AddressSanitizer.html)
and [Undefined Behavior Sanitizer](https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html).
This is mostly done automagically by various CI systems for each PR, but you may
want to do it locally as well. The process slightly varies depending on the
compiler you want to use and which part of the test suite you want to run.
## gcc
gcc compiles in sanitizer libraries dynamically by default, so you need to get
the shared libraries first - on Fedora these are shipped as a separate packages
(`libasan` for Address Sanitizer and `libubsan` for Undefined Behavior Sanitizer).
The compilation itself is then a matter of simply adding `-Db_sanitize=address,undefined`
to `meson`. That's it - following executions of `meson test` and integrations tests
under `test/` subdirectory will run with sanitizers enabled. However, to get
truly useful results, you should tweak the runtime configuration of respective
sanitizers; e.g. in systemd we set the following environment variables:
```bash
ASAN_OPTIONS=strict_string_checks=1:detect_stack_use_after_return=1:check_initialization_order=1:strict_init_order=1
UBSAN_OPTIONS=print_stacktrace=1:print_summary=1:halt_on_error=1
```
## clang
In case of clang things are somewhat different - the sanitizer libraries are
compiled in statically by default. This is not an issue if you plan to run
only the unit tests, but for integration tests you'll need to convince clang
to use the dynamic versions of sanitizer libraries.
First of all, pass `-shared-libsan` to both `clang` and `clang++`:
```bash
CFLAGS=-shared-libasan
CXXFLAGS=-shared-libasan
```
The `CXXFLAGS` are necessary for `src/libsystemd/sd-bus/test-bus-vtable-cc.c`. Compilation
is then the same as in case of gcc, simply add `-Db_sanitize=address,undefined`
to the `meson` call and use the same environment variables for runtime configuration.
```bash
ASAN_OPTIONS=strict_string_checks=1:detect_stack_use_after_return=1:check_initialization_order=1:strict_init_order=1
UBSAN_OPTIONS=print_stacktrace=1:print_summary=1:halt_on_error=1
```
After this, you'll probably notice that all compiled binaries complain about
missing `libclang_rt.asan*` library. To fix this, you have to install clang's
runtime libraries, usually shipped in the `compiler-rt` package. As these libraries
are installed in a non-standard location (non-standard for `ldconfig`), you'll
need to manually direct binaries to the respective runtime libraries.
```
# Optionally locate the respective runtime DSO
$ ldd build/systemd | grep libclang_rt.asan
libclang_rt.asan-x86_64.so => not found
libclang_rt.asan-x86_64.so => not found
$ find /usr/lib* /usr/local/lib* -type f -name libclang_rt.asan-x86_64.so 2>/dev/null
/usr/lib64/clang/7.0.1/lib/libclang_rt.asan-x86_64.so
# Set the LD_LIBRARY_PATH accordingly
export LD_LIBRARY_PATH=/usr/lib64/clang/7.0.1/lib/
# If the path is correct, the "not found" message should change to an actual path
$ ldd build/systemd | grep libclang_rt.asan
libclang_rt.asan-x86_64.so => /usr/lib64/clang/7.0.1/lib/libclang_rt.asan-x86_64.so (0x00007fa9752fc000)
```
This should help binaries to correctly find necessary sanitizer DSOs.
Also, to make the reports useful, `llvm-symbolizer` tool is required (usually
part of the `llvm` package).
## Background notes
The reason why you need to force dynamic linking in case of `clang` is that some
applications make use of `libsystemd`, which is compiled with sanitizers as well.
However, if a *standard* (uninstrumented) application loads an instrumented library,
it will immediately fail due to unresolved symbols. To fix/workaround this, you
need to pre-load the ASan DSO using `LD_PRELOAD=/path/to/asan/dso`, which will
make things work as expected in most cases. This will, obviously, not work with
statically linked sanitizer libraries.
These shenanigans are performed automatically when running the integration test
suite (i.e. `test/TEST-??-*`) and are located in `test/test-functions` (mainly,
but not only, in the `create_asan_wrapper` function).
test/test-functions
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@@ -54,6 +54,30 @@ if [[ "$IS_BUILT_WITH_ASAN" = "yes" ]]; then
PATH_TO_INIT=$ROOTLIBDIR/systemd-under-asan
QEMU_MEM="1536M"
QEMU_SMP=4
# We need to correctly distinguish between gcc's and clang's ASan DSOs.
if ldd $BUILD_DIR/systemd | grep -q libasan.so; then
ASAN_COMPILER=gcc
elif ldd $BUILD_DIR/systemd | grep -q libclang_rt.asan; then
ASAN_COMPILER=clang
# As clang's ASan DSO is usually in a non-standard path, let's check if
# the environment is set accordingly. If not, warn the user and exit.
# We're not setting the LD_LIBRARY_PATH automagically here, because
# user should encounter (and fix) the same issue when running the unit
# tests (meson test)
if ldd "$BUILD_DIR/systemd" | grep -q "libclang_rt.asan.*not found"; then
_asan_rt_name="$(ldd $BUILD_DIR/systemd | awk '/libclang_rt.asan/ {print $1; exit}')"
_asan_rt_path="$(find /usr/lib* /usr/local/lib* -type f -name "$_asan_rt_name" 2>/dev/null | sed 1q)"
echo >&2 "clang's ASan DSO ($_asan_rt_name) is not present in the runtime library path"
echo >&2 "Consider setting LD_LIBRARY_PATH=${_asan_rt_path%/*}"
exit 1
fi
else
echo >&2 "systemd is not linked against the ASan DSO"
echo >&2 "gcc does this by default, for clang compile with -shared-libasan"
exit 1
fi
fi
function find_qemu_bin() {
@@ -268,7 +292,7 @@ setup_basic_environment() {
install_depmod_files
generate_module_dependencies
if [[ "$IS_BUILT_WITH_ASAN" = "yes" ]]; then
create_asan_wrapper
create_asan_wrapper
fi
}
@@ -348,7 +372,24 @@ EOF
create_asan_wrapper() {
local _asan_wrapper=$initdir/$ROOTLIBDIR/systemd-under-asan
local _asan_rt_pattern
ddebug "Create $_asan_wrapper"
case "$ASAN_COMPILER" in
gcc)
_asan_rt_pattern="*libasan*"
;;
clang)
_asan_rt_pattern="libclang_rt.asan-*"
# Install llvm-symbolizer to generate useful reports
# See: https://clang.llvm.org/docs/AddressSanitizer.html#symbolizing-the-reports
dracut_install "llvm-symbolizer"
;;
*)
dfail "Unsupported compiler: $ASAN_COMPILER"
exit 1
esac
cat >$_asan_wrapper <<EOF
#!/bin/bash
@@ -358,18 +399,28 @@ DEFAULT_ASAN_OPTIONS=strict_string_checks=1:detect_stack_use_after_return=1:chec
DEFAULT_UBSAN_OPTIONS=print_stacktrace=1:print_summary=1:halt_on_error=1
DEFAULT_ENVIRONMENT="ASAN_OPTIONS=\$DEFAULT_ASAN_OPTIONS UBSAN_OPTIONS=\$DEFAULT_UBSAN_OPTIONS"
# As right now bash is the PID 1, we can't expect PATH to have a sane value.
# Let's make one to prevent unexpected "<bin> not found" issues in the future
export PATH="/sbin:/bin:/usr/sbin:/usr/bin"
mount -t proc proc /proc
mount -t sysfs sysfs /sys
mount -o remount,rw /
PATH_TO_ASAN=\$(find / -name '*libasan*' | sed 1q)
PATH_TO_ASAN=\$(find / -name '$_asan_rt_pattern' | sed 1q)
if [[ "\$PATH_TO_ASAN" ]]; then
# A lot of services (most notably dbus) won't start without preloading libasan
# See https://github.com/systemd/systemd/issues/5004
DEFAULT_ENVIRONMENT="\$DEFAULT_ENVIRONMENT LD_PRELOAD=\$PATH_TO_ASAN"
# Let's add the ASan DSO's path to the dynamic linker's cache. This is pretty
# unnecessary for gcc & libasan, however, for clang this is crucial, as its
# runtime ASan DSO is in a non-standard (library) path.
echo \${PATH_TO_ASAN%/*} > /etc/ld.so.conf.d/asan-path-override.conf
ldconfig
fi
echo DefaultEnvironment=\$DEFAULT_ENVIRONMENT >>/etc/systemd/system.conf
echo DefaultTimeoutStartSec=180s >>/etc/systemd/system.conf
echo DefaultStandardOutput=journal+console >>/etc/systemd/system.conf
# ASAN and syscall filters aren't compatible with each other.
find / -name '*.service' -type f | xargs sed -i 's/^\\(MemoryDeny\\|SystemCall\\)/#\\1/'
@@ -475,14 +526,14 @@ get_ldpath() {
install_missing_libraries() {
# install possible missing libraries
for i in $initdir{,/usr}/{sbin,bin}/* $initdir{,/usr}/lib/systemd/{,tests/{,manual/,unsafe/}}*; do
LD_LIBRARY_PATH=$(get_ldpath $i) inst_libs $i
LD_LIBRARY_PATH="${LD_LIBRARY_PATH:+$LD_LIBRARY_PATH:}$(get_ldpath $i)" inst_libs $i
done
}
create_empty_image() {
local _size=500
if [[ "$STRIP_BINARIES" = "no" ]]; then
_size=$((2*_size))
_size=$((4*_size))
fi
rm -f "$TESTDIR/rootdisk.img"
# Create the blank file to use as a root filesystem