On Wed, Aug 7, 2019 at 1:38 PM Arnaldo Carvalho de Melo <[email protected]> wrote: > > Em Wed, Jul 24, 2019 at 04:44:57PM -0700, Numfor Mbiziwo-Tiapo escreveu: > > These patches are all warnings that the MSAN (Memory Sanitizer) build > > of perf has caught. > > > > To build perf with MSAN enabled run: > > make -C tools/perf CLANG=1 CC=clang EXTRA_CFLAGS="-fsanitize=memory\ > > -fsanitize-memory-track-origins" > > > > (The -fsanitizer-memory-track-origins makes the bugs clearer but > > isn't strictly necessary.) > > > > (Additionally, llvm might have to be installed and clang might have to > > be specified as the compiler - export CC=/usr/bin/clang). > > > > The patches "Fix util.c use of uninitialized value warning" and "Fix > > annotate.c use of uninitialized value error" build on top of each other > > (the changes in Fix util.c use of uninitialized value warning must be > > made first). > > > > When running the commands provided in the repro instructions, MSAN will > > generate false positive uninitialized memory errors. This is happening > > because libc is not MSAN-instrumented. Finding a way to build libc with > > MSAN will get rid of these false positives and allow the real warnings > > mentioned in the patches to be shown. > > So this is because I'm not running a glibc linked with MSAN? Do you have > any pointer to help building glibc with MSAN? I want to do that inside a > container so that I can use these sanitizers, thanks, > > [root@quaco ~]# perf record -o - ls / | perf --no-pager annotate -i - --stdio > ==29732==WARNING: MemorySanitizer: use-of-uninitialized-value > ==29733==WARNING: MemorySanitizer: use-of-uninitialized-value > #0 0xcc136d in add_path > /home/acme/git/perf/tools/lib/subcmd/exec-cmd.c:130:6 > #1 0xcc075e in setup_path > /home/acme/git/perf/tools/lib/subcmd/exec-cmd.c:146:2 > #2 0x71298d in main /home/acme/git/perf/tools/perf/perf.c:512:2 > #0 0xcc136d in add_path > /home/acme/git/perf/tools/lib/subcmd/exec-cmd.c:130:6 > #1 0xcc075e in setup_path > /home/acme/git/perf/tools/lib/subcmd/exec-cmd.c:146:2 > #2 0x71298d in main /home/acme/git/perf/tools/perf/perf.c:512:2 > #3 0x7f45b9e29f32 in __libc_start_main (/lib64/libc.so.6+0x23f32) > #4 0x447dcd in _start (/home/acme/bin/perf+0x447dcd) > > Uninitialized value was created by a heap allocation > #3 0x7fd6433cff32 in __libc_start_main (/lib64/libc.so.6+0x23f32) > #4 0x447dcd in _start (/home/acme/bin/perf+0x447dcd) > > Uninitialized value was created by a heap allocation > #0 0x4507d2 in malloc > /home/acme/git/llvm/projects/compiler-rt/lib/msan/msan_interceptors.cc:916:3 > #1 0x7f45b9e7fc47 in __vasprintf_internal (/lib64/libc.so.6+0x79c47) > > SUMMARY: MemorySanitizer: use-of-uninitialized-value > /home/acme/git/perf/tools/lib/subcmd/exec-cmd.c:130:6 in add_path > Exiting > #0 0x4507d2 in malloc > /home/acme/git/llvm/projects/compiler-rt/lib/msan/msan_interceptors.cc:916:3 > #1 0x7fd643425c47 in __vasprintf_internal (/lib64/libc.so.6+0x79c47) > > SUMMARY: MemorySanitizer: use-of-uninitialized-value > /home/acme/git/perf/tools/lib/subcmd/exec-cmd.c:130:6 in add_path > Exiting > [root@quaco ~]# > > > Numfor Mbiziwo-Tiapo (3): > > Fix util.c use of uninitialized value warning > > Fix annotate.c use of uninitialized value error > > Fix sched-messaging.c use of uninitialized value errors > > > > tools/perf/bench/sched-messaging.c | 3 ++- > > tools/perf/util/annotate.c | 15 +++++++++++---- > > tools/perf/util/header.c | 2 +- > > 3 files changed, 14 insertions(+), 6 deletions(-)
Thanks Arnaldo! Debugging the issue it isn't down glibc, there are interceptors in the sanitizers for asprintf to recognize it as a source of memory allocation. The problem is the sanitizers don't support _FORTIFY_SOURCE [1] and this is causing the false positives. The following patch works to resolve the false-positive issue for me: ----- --- a/tools/lib/subcmd/Makefile +++ b/tools/lib/subcmd/Makefile @@ -20,7 +20,13 @@ MAKEFLAGS += --no-print-directory LIBFILE = $(OUTPUT)libsubcmd.a CFLAGS := $(EXTRA_WARNINGS) $(EXTRA_CFLAGS) -CFLAGS += -ggdb3 -Wall -Wextra -std=gnu99 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fPIC +CFLAGS += -ggdb3 -Wall -Wextra -std=gnu99 -fPIC + +ifeq ($(DEBUG),0) + ifeq ($(feature-fortify-source), 1) + CFLAGS += -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 + endif +endif ifeq ($(CC_NO_CLANG), 0) CFLAGS += -O3 ----- Thanks, Ian [1] https://github.com/google/sanitizers/wiki/AddressSanitizer#faq > > -- > > 2.22.0.657.g960e92d24f-goog > > -- > > - Arnaldo
