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Mark Rutland
dc55daff90
kcov: prefault the kcov_area
On many architectures the vmalloc area is lazily faulted in upon first access. This is problematic for KCOV, as __sanitizer_cov_trace_pc accesses the (vmalloc'd) kcov_area, and fault handling code may be instrumented. If an access to kcov_area faults, this will result in mutual recursion through the fault handling code and __sanitizer_cov_trace_pc(), eventually leading to stack corruption and/or overflow. We can avoid this by faulting in the kcov_area before __sanitizer_cov_trace_pc() is permitted to access it. Once it has been faulted in, it will remain present in the process page tables, and will not fault again. [akpm@linux-foundation.org: code cleanup] [akpm@linux-foundation.org: add comment explaining kcov_fault_in_area()] [akpm@linux-foundation.org: fancier code comment from Mark] Link: http://lkml.kernel.org/r/20180504135535.53744-3-mark.rutland@arm.com Signed-off-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Linux kernel ============ There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. The formatted documentation can also be read online at: https://www.kernel.org/doc/html/latest/ 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.
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