c86860f5e2
> Fix signal propagation logic for Linux/Android exception handler. > > The current code is relying on info->si_pid to figure out whether > the exception handler was triggered by a signal coming from the kernel > (that will re-trigger until the cause that triggered the signal has > been cleared) or from user-space e.g., kill -SIGNAL pid, which will NOT > automatically re-trigger in the next signal handler in the chain. > While the intentions are good (manually re-triggering user-space > signals), the current implementation mistakenly looks at the si_pid > field in siginfo_t, assuming that it is coming from the kernel if > si_pid == 0. > This is wrong. siginfo_t, in fact, is a union and si_pid is meaningful > only for userspace signals. For signals originated by the kernel, > instead, si_pid overlaps with si_addr (the faulting address). > As a matter of facts, the current implementation is mistakenly > re-triggering the signal using tgkill for most of the kernel-space > signals (unless the fault address is exactly 0x0). > This is not completelly correct for the case of SIGSEGV/SIGBUS. The > next handler in the chain will stil see the signal, but the |siginfo| > and the |context| arguments of the handler will be meaningless > (retriggering a signal with tgkill doesn't preserve them). > Therefore, if the next handler in the chain expects those arguments > to be set, it will fail. > Concretelly, this is causing problems to WebView. In some rare > circumstances, the next handler in the chain is a user-space runtime > which does SIGSEGV handling to implement speculative null pointer > managed exceptions (see as an example > http://www.mono-project.com/docs/advanced/runtime/docs/exception-handling/) > > The fix herein proposed consists in using the si_code (see SI_FROMUSER > macros) to determine whether a signal is coming form the kernel > (and therefore just re-establish the next signal handler) or from > userspace (and use the tgkill logic). > > Repro case: > This issue is visible in Chrome for Android with this simple repro case: > - Add a non-null pointer dereference in the codebase: > *((volatile int*)0xbeef) = 42 > Without this change: the next handler (the libc trap) prints: > F/libc ( 595): Fatal signal 11 (SIGSEGV), code 1, fault addr 0x487 > where 0x487 is actually the PID of the process (which is wrong). > With this change: the next handler prints: > F/libc ( 595): Fatal signal 11 (SIGSEGV), code 1, fault addr 0xbeef > which is the correct answer. > > BUG=chromium:481937 > R=mark@chromium.org > > Review URL: https://breakpad.appspot.com/6844002 BUG=chromium:481937 git-svn-id: http://google-breakpad.googlecode.com/svn/branches/chrome_43@1457 4c0a9323-5329-0410-9bdc-e9ce6186880e
Breakpad is a set of client and server components which implement a
crash-reporting system.
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Getting started in 32-bit mode (from trunk)
Configure: CXXFLAGS=-m32 CFLAGS=-m32 CPPFLAGS=-m32 ./configure
Build: make
Test: make check
Install: make install
If you need to reconfigure your build be sure to run "make distclean" first.
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To request change review:
0. Get access to a read-write copy of source.
Owners at http://code.google.com/p/google-breakpad/ are able to grant
this access.
1. Check out a read-write copy of source using instructions at
http://code.google.com/p/google-breakpad/source/checkout
2. Make changes. Build and test your changes.
For core code like processor use methods above.
For linux/mac/windows, there are test targets in each project file.
3. Download http://codereview.appspot.com/static/upload.py
4. Run upload.py from the 'src' directory:
upload.py --server=breakpad.appspot.com
You will be prompted for credential and a description.
5. At http://breakpad.appspot.com you'll find your issue listed; click on it,
and select Publish+Mail, and enter in the code reviewer and CC
google-breakpad-dev@googlegroups.com
6. When applying code review feedback, specify the '-i' option when running
upload.py again and pass the issue number so it updates the existing issue,
rather than creating a new one.
Be sure to rerun upload.py from the same directory as you did for previous
uploads to allow for proper diff calculations.