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A mirror of the official Linux kernel repository just in case
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For live patching and possibly other use cases, a stack trace is only useful if it can be assured that it's completely reliable. Add a new save_stack_trace_tsk_reliable() function to achieve that. Note that if the target task isn't the current task, and the target task is allowed to run, then it could be writing the stack while the unwinder is reading it, resulting in possible corruption. So the caller of save_stack_trace_tsk_reliable() must ensure that the task is either 'current' or inactive. save_stack_trace_tsk_reliable() relies on the x86 unwinder's detection of pt_regs on the stack. If the pt_regs are not user-mode registers from a syscall, then they indicate an in-kernel interrupt or exception (e.g. preemption or a page fault), in which case the stack is considered unreliable due to the nature of frame pointers. It also relies on the x86 unwinder's detection of other issues, such as: - corrupted stack data - stack grows the wrong way - stack walk doesn't reach the bottom - user didn't provide a large enough entries array Such issues are reported by checking unwind_error() and !unwind_done(). Also add CONFIG_HAVE_RELIABLE_STACKTRACE so arch-independent code can determine at build time whether the function is implemented. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Acked-by: Ingo Molnar <mingo@kernel.org> # for the x86 changes Signed-off-by: Jiri Kosina <jkosina@suse.cz> |
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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.