diff options
| author | Ingo Molnar <mingo@kernel.org> | 2015-07-04 09:58:19 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-07-04 10:05:56 +0200 |
| commit | b96fecbfa8c88b057e2bbf10021521c232bb3650 (patch) | |
| tree | 9b5d855085336ae9ab5b9c5ff7f6972b13f181de | |
| parent | 864d5bb957138d1ed9641a5eff7849a56ddadc16 (diff) | |
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:
91a8c2a5b43f ("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>
| -rw-r--r-- | arch/x86/kernel/fpu/init.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c index fc878fee6a51..32826791e675 100644 --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -95,11 +95,12 @@ static void __init fpu__init_system_mxcsr(void) unsigned int mask = 0; if (cpu_has_fxsr) { - struct fxregs_state fx_tmp __aligned(32) = { }; + /* Static because GCC does not get 16-byte stack alignment right: */ + static struct fxregs_state fxregs __initdata; - asm volatile("fxsave %0" : "+m" (fx_tmp)); + asm volatile("fxsave %0" : "+m" (fxregs)); - mask = fx_tmp.mxcsr_mask; + mask = fxregs.mxcsr_mask; /* * If zero then use the default features mask, |