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commit81291383ffupstream. A e5500 machine running a 32-bit kernel sometimes hangs at boot, seemingly going into an infinite loop of instruction storage interrupts. The ESR (Exception Syndrome Register) has a value of 0x800000 (store) when this happens, which is likely set by a previous store. An instruction TLB miss interrupt would then leave ESR unchanged, and if no PTE exists it calls directly to the instruction storage interrupt handler without changing ESR. access_error() does not cause a segfault due to a store to a read-only vma because is_exec is true. Most subsequent fault handling does not check for a write fault on a read-only vma, and might do strange things like create a writeable PTE or call page_mkwrite on a read only vma or file. It's not clear what happens here to cause the infinite faulting in this case, a fault handler failure or low level PTE or TLB handling. In any case this can be fixed by having the instruction storage interrupt zero regs->dsisr rather than storing the ESR value to it. Fixes:a01a3f2ddb("powerpc: remove arguments from fault handler functions") Cc: stable@vger.kernel.org # v5.12+ Reported-by: Jacques de Laval <jacques.delaval@protonmail.com> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Tested-by: Jacques de Laval <jacques.delaval@protonmail.com> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211028133043.4159501-1-npiggin@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
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.