linux/arch/x86/kernel/fpu
Ingo Molnar b96fecbfa8 x86/fpu: Fix boot crash in the early FPU code
Jan Kara and Thomas Gleixner reported boot crashes in the FPU
code:

  general protection fault: 0000 [#1] SMP
  RIP: 0010:[<ffffffff81048a6c>]  [<ffffffff81048a6c>] mxcsr_feature_mask_init+0x1c/0x40

  2b:*  0f ae 85 00 fe ff ff    fxsave -0x200(%rbp)

and bisected it down to the following FPU commit:

   91a8c2a5b4 ("x86/fpu: Clean up and fix MXCSR handling")

The reason is that the on-stack FPU registers state variable,
used by the FXSAVE instruction, did not have the required
minimum alignment of 16 bytes, causing the general protection
fault.

This is most likely a GCC bug in older GCC versions, but the
offending commit also added a bogus extra 32-byte alignment
(which GCC ignored too).

So fix this bug by making the variable static again, but also
mark it __initdata this time, because fpu__init_system_mxcsr()
is now an __init function.

Reported-and-bisected-by: Jan Kara <jack@suse.cz>
Reported-bisected-and-tested-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150704075819.GA9201@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-07-04 10:05:56 +02:00
..
Makefile x86/fpu: Factor out the FPU regset code into fpu/regset.c 2015-05-19 15:48:09 +02:00
bugs.c x86/fpu/init: Propagate __init annotations 2015-05-19 15:48:11 +02:00
core.c x86/fpu: Standardize the parameter type of copy_kernel_to_fpregs() 2015-05-27 14:11:32 +02:00
init.c x86/fpu: Fix boot crash in the early FPU code 2015-07-04 10:05:56 +02:00
regset.c x86/fpu: Rename fpu__activate_fpstate() to fpu__activate_fpstate_write() 2015-05-27 14:11:26 +02:00
signal.c x86/fpu: Pass 'struct fpu' to fpu__restore() 2015-05-19 15:48:11 +02:00
xstate.c x86/fpu: Fix double-increment in setup_xstate_features() 2015-06-12 10:48:12 +02:00