17ad0c18b1
Reason for revert: It is causing breakpad crash reports to be invalid (see the associated bug). Merging empty holes in r-x mappings was originally introduced in https://breakpad.appspot.com/7714003 to deal with the first generation of relro packing, which could introduce holes within a .so mapping: [libchrome.so] [guard region] [libchrome.so] However, the logic is broken for the case of two *different* adjacent .so mappings with a guard region in the middle: [libfoo.so] [guard region] [libchrome.so] In this case the guard region is mistakenly associated with libfoo.so, but that is not the right thing to do. In fact, the second generation of rerlo packing added the guard region to prevent mmaps from overlapping and to give room for the non-zero vaddr of relro-packed libraries, which require an anticipated load bias. As the first generation of relro packing is not used anymore, there is no reason to keep this buggy code, which causes failures in decoding crashes where an arbitrary library is mapped immediately before a rerlo packed library. Original issue's description: > Extend mapping merge to include reserved but unused mappings. > > When parsing /proc/pid/maps, current code merges adjacent entries that > refer to the same library and where the start of the second is equal to > the end of the first, for example: > > 40022000-40025000 r-xp 00000000 b3:11 827 /system/lib/liblog.so > 40025000-40026000 r--p 00002000 b3:11 827 /system/lib/liblog.so > 40026000-40027000 rw-p 00003000 b3:11 827 /system/lib/liblog.so > > When the system linker loads a library it first reserves all the address > space required, from the smallest start to the largest end address, using > an anonymous mapping, and then maps loaded segments inside that reservation. > If the loaded segments do not fully occupy the reservation this leaves > gaps, and these gaps prevent merges that should occur from occurring: > > 40417000-4044a000 r-xp 00000000 b3:11 820 /system/lib/libjpeg.so > > 4044a000-4044b000 ---p 00000000 00:00 0 > 4044b000-4044c000 r--p 00033000 b3:11 820 /system/lib/libjpeg.so > 4044c000-4044d000 rw-p 00034000 b3:11 820 /system/lib/libjpeg.so > > Where the segments that follow this gap do not contain executable code > the failure to merge does not affect breakpad operation. However, where > they do then the merge needs to occur. Packing relocations in a large > library splits the executable segment into two, resulting in: > > 73b0c000-73b21000 r-xp 00000000 b3:19 786460 > /data/.../libchrome.2160.0.so > > 73b21000-73d12000 ---p 00000000 00:00 0 > 73d12000-75a90000 r-xp 00014000 b3:19 786460 > /data/.../libchrome.2160.0.so > 75a90000-75c0d000 rw-p 01d91000 b3:19 786460 > /data/.../libchrome.2160.0.so > > Here the mapping at 73d12000-75a90000 must be merged into 73b0c000-73b21000 > so that breakpad correctly calculates the base address for text. > > This change enables the full merge by also merging anonymous maps which > result from unused reservation, identified as '---p' with offset 0, and > which follow on from an executable mapping, into that executable mapping. > > BUG=chromium:394703 BUG=chromium:499747 R=primiano@chromium.org, rmcilroy@chromium.org Review URL: https://codereview.chromium.org/1923383002 . |
||
|---|---|---|
| android | ||
| autotools | ||
| docs | ||
| m4 | ||
| scripts | ||
| src | ||
| .gitignore | ||
| .travis.yml | ||
| 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.ANDROID | ||
| README.md | ||
Breakpad
Breakpad is a set of client and server components which implement a crash-reporting system.
- Homepage
- Documentation
- Bugs
- Discussion/Questions: google-breakpad-discuss@googlegroups.com
- Developer/Reviews: google-breakpad-dev@googlegroups.com
- Tests:
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.
To request change review:
-
Get a copy of depot_tools repo. http://dev.chromium.org/developers/how-tos/install-depot-tools
-
Create a new directory for checking out the source code. mkdir breakpad && cd breakpad
-
Run the
fetchtool from depot_tools to download all the source repos.fetch breakpad -
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.
-
Commit your changes to your local repo and upload them to the server. http://dev.chromium.org/developers/contributing-code e.g.
git commit ... && git cl upload ...You will be prompted for credential and a description. -
At https://codereview.chromium.org/ 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