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coprocessor_flush_all may be called from a context of a thread that is different from the thread being flushed. In that case contents of the cpenable special register may not match ti->cpenable of the target thread, resulting in unhandled coprocessor exception in the kernel context. Set cpenable special register to the ti->cpenable of the target register for the duration of the flush and restore it afterwards. This fixes the following crash caused by coprocessor register inspection in native gdb: (gdb) p/x $w0 Illegal instruction in kernel: sig: 9 [#1] PREEMPT Call Trace: ___might_sleep+0x184/0x1a4 __might_sleep+0x41/0xac exit_signals+0x14/0x218 do_exit+0xc9/0x8b8 die+0x99/0xa0 do_illegal_instruction+0x18/0x6c common_exception+0x77/0x77 coprocessor_flush+0x16/0x3c arch_ptrace+0x46c/0x674 sys_ptrace+0x2ce/0x3b4 system_call+0x54/0x80 common_exception+0x77/0x77 note: gdb[100] exited with preempt_count 1 Killed Cc: stable@vger.kernel.org Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
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.