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- libsanitizer: enable swapcontext/makecontext interceptor on uClibc-ng
- The swapcontext/makecontext ASan interceptor is gated on
- ASAN_INTERCEPT_SWAPCONTEXT, which until now was only enabled for
- SANITIZER_GLIBC || SANITIZER_SOLARIS. Since 0001-libsanitizer-do-not-
- treat-uClibc-ng-as-glibc.patch forces SANITIZER_GLIBC=0 on uClibc-ng,
- the interceptor is silently dropped on our toolchain. Two consequences:
- 1. asan_interceptors.cpp:399 (INTERCEPTOR(swapcontext, ...)) is not
- compiled, so the runtime never emits the documented
- "WARNING: ASan doesn't fully support makecontext/swapcontext
- functions and may produce false positives in some cases!"
- and the GCC testsuite case c-c++-common/asan/swapcontext-test-1.c
- hits "output pattern test FAIL" for the first dg-output regex.
- 2. ClearShadowMemoryForContextStack() is never called around a
- ucontext switch, so stack bytes that were poisoned by ASan in
- one context stay poisoned after we resume on another stack.
- This is a real runtime bug, not just a missing print:
- coroutine code that touches a previously-poisoned region will
- trip false-positive use-after-scope / stack-use-after-return
- reports.
- The gated code in asan_interceptors.cpp:339-428 and asan_linux.cpp:
- 201-226 only uses the POSIX surface (stack_t::ss_sp, ss_size, ss_flags,
- swapcontext(), makecontext()) plus the libsanitizer-internal INTERCEPTOR
- machinery, none of which is glibc-specific. uClibc-ng provides all of
- these (ss_flags has existed in uClibc since the initial ucontext port,
- swapcontext()/makecontext() are now correct after the 0004-arm-ucontext-
- fix-vfp-save-restore-area.patch in patches/uClibc-ng/), so it is safe
- to flip the gate on for SANITIZER_UCLIBC as well.
- This is the natural follow-up to 0001 once swapcontext on uClibc-ng
- actually works.
- Signed-off-by: Ramin Moussavi <ramin.moussavi@yacoub.de>
- ---
- --- a/libsanitizer/asan/asan_interceptors.h
- +++ b/libsanitizer/asan/asan_interceptors.h
- @@ -50,7 +50,11 @@
- # define ASAN_USE_ALIAS_ATTRIBUTE_FOR_INDEX 0
- #endif
-
- -#if SANITIZER_GLIBC || SANITIZER_SOLARIS
- +/* uClibc-ng provides swapcontext()/makecontext() and the standard
- + stack_t layout, and our 0004-arm-ucontext-fix-vfp-save-restore-area
- + patch in patches/uClibc-ng/ makes context switching actually work,
- + so enable the swapcontext interceptor on uClibc as well. */
- +#if SANITIZER_GLIBC || SANITIZER_SOLARIS || SANITIZER_UCLIBC
- # define ASAN_INTERCEPT_SWAPCONTEXT 1
- #else
- # define ASAN_INTERCEPT_SWAPCONTEXT 0
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