leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
5fc960380e
linux/arch/x86/kernel/fpu
History
Ingo Molnar 5fc960380e x86/fpu/math-emu: Fix math-emu boot crash 
On a math-emu bootup the following crash occurs:

	Initializing CPU#0
	------------[ cut here ]------------
	kernel BUG at arch/x86/kernel/traps.c:779!
	invalid opcode: 0000 [#1] SMP
	[...]
	EIP is at do_device_not_available+0xe/0x70
	[...]
	Call Trace:
	 [<c18238e6>] error_code+0x5a/0x60
	 [<c1002bd0>] ? math_error+0x140/0x140
	 [<c100bbd9>] ? fpu__init_cpu+0x59/0xa0
	 [<c1012322>] cpu_init+0x202/0x330
	 [<c104509f>] ? __native_set_fixmap+0x1f/0x30
	 [<c1b56ab0>] trap_init+0x305/0x346
	 [<c1b548af>] start_kernel+0x1a5/0x35d
	 [<c1b542b4>] i386_start_kernel+0x82/0x86

The reason is that in the following commit:

  b1276c48e9 ("x86/fpu: Initialize fpregs in fpu__init_cpu_generic()")

I failed to consider math-emu's limitation that it cannot execute the
FNINIT instruction in kernel mode.

The long term fix might be to allow math-emu to execute (certain) kernel
mode FPU instructions, but for now apply the safe (albeit somewhat ugly)
fix: initialize the emulation state explicitly without trapping out to
the FPU emulator.

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: 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>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-08-22 10:02:04 +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/math-emu: Fix math-emu boot crash 2015-08-22 10:02:04 +02:00
Makefile x86/fpu: Factor out the FPU regset code into fpu/regset.c 2015-05-19 15:48:09 +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