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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 git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1454 4c0a9323-5329-0410-9bdc-e9ce6186880e |
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| android | ||
| autotools | ||
| m4 | ||
| src | ||
| .gitignore | ||
| aclocal.m4 | ||
| AUTHORS | ||
| breakpad-client.pc.in | ||
| breakpad.pc.in | ||
| ChangeLog | ||
| codereview.settings | ||
| configure | ||
| configure.ac | ||
| DEPS | ||
| INSTALL | ||
| LICENSE | ||
| Makefile.am | ||
| Makefile.in | ||
| NEWS | ||
| README | ||
| README.ANDROID | ||
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.