forked from luck/tmp_suning_uos_patched
dc912c3035
Fengguang Wu's zero day bot triggered a stack unwinder dump. This can
be easily triggered when CONFIG_FRAME_POINTERS is enabled and -mfentry
is in use on x86_32.
># cd /sys/kernel/debug/tracing
># echo 'p:schedule schedule' > kprobe_events
># echo stacktrace > events/kprobes/schedule/trigger
This is because the code that implemented fentry in the ftrace_regs_caller
tried to use the least amount of #ifdefs, and modified ebp when
CC_USE_FENTRY was defined to point to the parent ip as it does when
CC_USE_FENTRY is not defined. But when CONFIG_FRAME_POINTERS is set, it
corrupts the ebp register for this frame while doing the tracing.
NOTE, it does not corrupt ebp in any other way. It is just a bad frame
pointer when calling into the tracing infrastructure. The original ebp is
restored before returning from the fentry call. But if a stack trace is
performed inside the tracing, the unwinder will notice the bad ebp.
Instead of toying with ebp with CC_USING_FENTRY, just slap the parent ip
into the second parameter (%edx), and have an #else that does it the
original way.
The unwinder will unfortunately miss the function being traced, as the
stack frame is not set up yet for it, as it is for x86_64. But fixing that
is a bit more complex and did not work before anyway.
This has been tested with and without FRAME_POINTERS being set while using
-mfentry, as well as using an older compiler that uses mcount.
Analyzed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.