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Mark Rutland
7d9e8f71b9
Generally, taking an unexpected exception should be a fatal event, and bad_mode is intended to cater for this. However, it should be possible to contain unexpected synchronous exceptions from EL0 without bringing the kernel down, by sending a SIGILL to the task. We tried to apply this approach in commit9955ac47f4("arm64: don't kill the kernel on a bad esr from el0"), by sending a signal for any bad_mode call resulting from an EL0 exception. However, this also applies to other unexpected exceptions, such as SError and FIQ. The entry paths for these exceptions branch to bad_mode without configuring the link register, and have no kernel_exit. Thus, if we take one of these exceptions from EL0, bad_mode will eventually return to the original user link register value. This patch fixes this by introducing a new bad_el0_sync handler to cater for the recoverable case, and restoring bad_mode to its original state, whereby it calls panic() and never returns. The recoverable case branches to bad_el0_sync with a bl, and returns to userspace via the usual ret_to_user mechanism. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Fixes:9955ac47f4("arm64: don't kill the kernel on a bad esr from el0") Reported-by: Mark Salter <msalter@redhat.com> Cc: Will Deacon <will.deacon@arm.com> Cc: stable@vger.kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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.