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Ingo Molnar 47f01e8cc2 x86/fpu: Fix FPU register read access to the current task 
Bobby Powers reported the following FPU warning during ELF coredumping:

   WARNING: CPU: 0 PID: 27452 at arch/x86/kernel/fpu/core.c:324 fpu__activate_stopped+0x8a/0xa0()

This warning unearthed an invalid assumption about fpu__activate_stopped()
that I added in:

  67e97fc2ec ("x86/fpu: Rename init_fpu() to fpu__unlazy_stopped() and add debugging check")

the old init_fpu() function had an (intentional but obscure) side effect:
when FPU registers are accessed for the current task, for reading, then
it synchronized live in-register FPU state with the fpstate by saving it.

So fix this bug by saving the FPU if we are the current task. We'll
still warn in fpu__save() if this is called for not yet stopped
child tasks, so the debugging check is still preserved.

Also rename the function to fpu__activate_fpstate(), because it's not
exclusively used for stopped tasks, but for the current task as well.

( Note that this bug calls for a cleaner separation of access-for-read
  and access-for-modification FPU methods, but we'll do that in separate
  patches. )

Reported-by: Bobby Powers <bobbypowers@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-05-27 12:40:18 +02:00
..
boot * Avoid garbage names in efivarfs due to buggy firmware by zero'ing 2015-05-06 08:30:24 +02:00
configs
crypto x86/fpu, crypto: Fix AVX2 feature tests 2015-05-22 10:58:45 +02:00
ia32 x86/fpu: Split out fpu/signal.h from fpu/internal.h for signal frame handling functions 2015-05-19 15:48:05 +02:00
include x86/fpu: Fix FPU register read access to the current task 2015-05-27 12:40:18 +02:00
kernel x86/fpu: Fix FPU register read access to the current task 2015-05-27 12:40:18 +02:00
kvm Linux 4.1-rc5 2015-05-25 09:39:19 +02:00
lguest x86/fpu: Rename i387.h to fpu/api.h 2015-05-19 15:47:30 +02:00
lib x86/fpu: Rename i387.h to fpu/api.h 2015-05-19 15:47:30 +02:00
math-emu x86/fpu: Harmonize FPU register state types 2015-05-19 15:48:09 +02:00
mm x86/fpu: Harmonize FPU register state types 2015-05-19 15:48:09 +02:00
net x86: bpf_jit: fix FROM_BE16 and FROM_LE16/32 instructions 2015-05-12 23:13:08 -04:00
oprofile
pci x86/PCI/ACPI: Make all resources except [io 0xcf8-0xcff] available on PCI bus 2015-04-30 22:17:34 +02:00
platform TTY/Serial patches for 4.1-rc1 2015-04-21 09:33:10 -07:00
power x86/fpu: Move various internal function prototypes to fpu/internal.h 2015-05-19 15:47:48 +02:00
purgatory
realmode
syscalls xen: features and fixes for 4.1-rc0 2015-04-16 14:01:03 -05:00
tools
um Merge branch 'exec_domain_rip_v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/misc 2015-04-15 13:53:55 -07:00
vdso x86/vdso: Fix 'make bzImage' on older distros 2015-05-11 10:25:02 +02:00
video
xen x86/fpu: Simplify fpu__cpu_init() 2015-05-19 15:47:44 +02:00
.gitignore
Kbuild
Kconfig Initial ACPI support for arm64: 2015-04-24 08:23:45 -07:00
Kconfig.cpu
Kconfig.debug x86/fpu: Add CONFIG_X86_DEBUG_FPU=y FPU debugging code 2015-05-19 15:48:12 +02:00
Makefile
Makefile.um
Makefile_32.cpu