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Linus Torvalds 15d8791cae i387: fix x86-64 preemption-unsafe user stack save/restore 
Commit 5b1cbac377 ("i387: make irq_fpu_usable() tests more robust")
added a sanity check to the #NM handler to verify that we never cause
the "Device Not Available" exception in kernel mode.

However, that check actually pinpointed a (fundamental) race where we do
cause that exception as part of the signal stack FPU state save/restore
code.

Because we use the floating point instructions themselves to save and
restore state directly from user mode, we cannot do that atomically with
testing the TS_USEDFPU bit: the user mode access itself may cause a page
fault, which causes a task switch, which saves and restores the FP/MMX
state from the kernel buffers.

This kind of "recursive" FP state save is fine per se, but it means that
when the signal stack save/restore gets restarted, it will now take the
'#NM' exception we originally tried to avoid.  With preemption this can
happen even without the page fault - but because of the user access, we
cannot just disable preemption around the save/restore instruction.

There are various ways to solve this, including using the
"enable/disable_page_fault()" helpers to not allow page faults at all
during the sequence, and fall back to copying things by hand without the
use of the native FP state save/restore instructions.

However, the simplest thing to do is to just allow the #NM from kernel
space, but fix the race in setting and clearing CR0.TS that this all
exposed: the TS bit changes and the TS_USEDFPU bit absolutely have to be
atomic wrt scheduling, so while the actual state save/restore can be
interrupted and restarted, the act of actually clearing/setting CR0.TS
and the TS_USEDFPU bit together must not.

Instead of just adding random "preempt_disable/enable()" calls to what
is already excessively ugly code, this introduces some helper functions
that mostly mirror the "kernel_fpu_begin/end()" functionality, just for
the user state instead.

Those helper functions should probably eventually replace the other
ad-hoc CR0.TS and TS_USEDFPU tests too, but I'll need to think about it
some more: the task switching functionality in particular needs to
expose the difference between the 'prev' and 'next' threads, while the
new helper functions intentionally were written to only work with
'current'.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-02-16 09:15:04 -08:00
..
acpi x86, acpi: Skip acpi x2apic entries if the x2apic feature is not present 2011-12-23 11:00:50 -08:00
apic x86, UV: Update Boot messages for SGI UV2 platform 2012-01-08 12:35:44 +01:00
cpu perf: Fix double start/stop in x86_pmu_start() 2012-02-07 16:58:56 +01:00
.gitignore
alternative.c x86: Call stop_machine_text_poke() on all CPUs 2011-11-14 13:05:15 +01:00
amd_gart_64.c doc: fix broken references 2011-09-27 18:08:04 +02:00
amd_nb.c Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci 2012-01-11 18:50:26 -08:00
apb_timer.c Merge branch 'timers-clocksource-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-07-23 10:34:47 -07:00
aperture_64.c memblock, x86: Replace memblock_x86_reserve/free_range() with generic ones 2011-07-14 11:47:53 -07:00
apm_32.c module_param: make bool parameters really bool (arch) 2012-01-13 09:32:18 +10:30
asm-offsets.c x86, efi: EFI boot stub support 2011-12-12 14:26:10 -08:00
asm-offsets_32.c x86: Generate system call tables and unistd_*.h from tables 2011-11-17 13:35:37 -08:00
asm-offsets_64.c x86: Generate system call tables and unistd_*.h from tables 2011-11-17 13:35:37 -08:00
audit_64.c
bootflag.c
check.c memblock, x86: Replace memblock_x86_reserve/free_range() with generic ones 2011-07-14 11:47:53 -07:00
cpuid.c switch device_get_devnode() and ->devnode() to umode_t * 2012-01-03 22:54:55 -05:00
crash.c x86, nmi: Wire up NMI handlers to new routines 2011-10-10 06:56:57 +02:00
crash_dump_32.c crash_dump: export is_kdump_kernel to modules, consolidate elfcorehdr_addr, setup_elfcorehdr and saved_max_pfn 2011-03-23 19:47:19 -07:00
crash_dump_64.c crash_dump: export is_kdump_kernel to modules, consolidate elfcorehdr_addr, setup_elfcorehdr and saved_max_pfn 2011-03-23 19:47:19 -07:00
devicetree.c x86: Fix files explicitly requiring export.h for EXPORT_SYMBOL/THIS_MODULE 2011-10-31 19:30:35 -04:00
doublefault_32.c
dumpstack.c bugs, x86: Fix printk levels for panic, softlockups and stack dumps 2012-01-26 21:28:45 +01:00
dumpstack_32.c x86, dumpstack: Fix code bytes breakage due to missing KERN_CONT 2011-12-19 13:09:56 -08:00
dumpstack_64.c Merge branches 'core-urgent-for-linus', 'perf-urgent-for-linus', 'sched-urgent-for-linus' and 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-02-02 11:11:13 -08:00
e820.c Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux 2012-01-18 15:51:48 -08:00
early-quirks.c x86, quirk: Fix SB600 revision check 2011-03-16 14:03:32 +01:00
early_printk.c Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-11 19:13:40 -08:00
entry_32.S Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit 2012-01-17 16:41:31 -08:00
entry_64.S Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit 2012-01-17 16:41:31 -08:00
ftrace.c x86/ftrace: Fix compiler warning in ftrace.c 2011-05-25 19:56:26 -04:00
head.c memblock, x86: Replace memblock_x86_reserve/free_range() with generic ones 2011-07-14 11:47:53 -07:00
head32.c memblock: Kill memblock_init() 2011-12-08 10:22:07 -08:00
head64.c memblock: Kill memblock_init() 2011-12-08 10:22:07 -08:00
head_32.S Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-03-15 20:01:36 -07:00
head_64.S x86: Keep current stack in NMI breakpoints 2011-12-21 15:38:55 -05:00
hpet.c Merge branch 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core 2012-01-07 12:03:30 -08:00
hw_breakpoint.c
i386_ksyms_32.c
i387.c treewide: fix potentially dangerous trailing ';' in #defined values/expressions 2011-07-21 14:10:00 +02:00
i8237.c x86: Use syscore_ops instead of sysdev classes and sysdevs 2011-03-23 22:15:54 +01:00
i8253.c x86: Use common i8253 clockevent 2011-07-01 10:37:14 +02:00
i8259.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
init_task.c
io_delay.c
ioport.c
irq.c Merge branch 'x86-apic-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-06 13:58:21 -08:00
irq_32.c x86: Fix the 32-bit stackoverflow-debug build 2011-12-05 12:25:44 +01:00
irq_64.c x86: Add stack top margin for stack overflow checking 2011-12-07 09:27:11 +01:00
irq_work.c
irqinit.c driver-core: remove sysdev.h usage. 2011-12-21 16:26:03 -08:00
jump_label.c jump_label, x86: Fix section mismatch 2011-12-06 20:41:02 +01:00
kdebugfs.c
kgdb.c x86, nmi: Wire up NMI handlers to new routines 2011-10-10 06:56:57 +02:00
kprobes.c Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2011-10-26 17:03:38 +02:00
kvm.c KVM guest: remove KVM guest pv mmu support 2011-12-27 11:17:08 +02:00
kvmclock.c KVM guest: prevent tracing recursion with kvmclock 2011-11-20 10:53:48 +02:00
ldt.c
machine_kexec_32.c
machine_kexec_64.c
Makefile Merge branch 'x86-syscall-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-16 18:19:19 -08:00
mca_32.c x86: Fix common misspellings 2011-03-18 10:39:30 +01:00
microcode_amd.c x86/microcode_amd: Add support for CPU family specific container files 2012-01-26 12:06:39 +01:00
microcode_core.c Merge branch 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core 2012-01-07 12:03:30 -08:00
microcode_intel.c x86, intel: Output microcode revision in /proc/cpuinfo 2011-10-14 13:16:35 +02:00
mmconf-fam10h_64.c
module.c modules: make arch's use default loader hooks 2011-07-24 22:06:04 +09:30
mpparse.c Merge branch 'memblock-kill-early_node_map' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc into core/memblock 2011-12-20 12:14:26 +01:00
msr.c switch device_get_devnode() and ->devnode() to umode_t * 2012-01-03 22:54:55 -05:00
nmi.c x86: Allow NMIs to hit breakpoints in i386 2011-12-21 15:38:55 -05:00
nmi_selftest.c x86, NMI: Add to_cpumask() to silence compile warning 2011-12-07 23:26:57 +01:00
paravirt-spinlocks.c
paravirt.c Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-tip 2011-08-12 20:46:24 -07:00
paravirt_patch_32.c
paravirt_patch_64.c
pci-calgary_64.c treewide: Convert uses of struct resource to resource_size(ptr) 2011-06-10 14:55:36 +02:00
pci-dma.c iommu: Add option to group multi-function devices 2011-11-15 12:22:31 +01:00
pci-iommu_table.c arch/x86/kernel/pci-iommu_table.c: Convert sprintf_symbol to %pS 2011-05-10 10:21:35 +02:00
pci-nommu.c
pci-swiotlb.c
pcspeaker.c
probe_roms.c x86: Fix files explicitly requiring export.h for EXPORT_SYMBOL/THIS_MODULE 2011-10-31 19:30:35 -04:00
process.c x86: Fix rflags in FAKE_STACK_FRAME 2011-12-06 10:02:38 +01:00
process_32.c nohz: Remove tick_nohz_idle_enter_norcu() / tick_nohz_idle_exit_norcu() 2011-12-11 10:31:57 -08:00
process_64.c Merge branch 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-06 14:00:12 -08:00
ptrace.c audit: inline audit_syscall_entry to reduce burden on archs 2012-01-17 16:16:56 -05:00
pvclock.c
quirks.c x86, amd: Fix up numa_node information for AMD CPU family 15h model 0-0fh northbridge functions 2011-12-05 18:13:11 +01:00
reboot.c x86/reboot: Remove VersaLogic Menlow reboot quirk 2012-01-30 10:52:33 +01:00
reboot_32.S x86, reboot: Fix relocations in reboot_32.S 2011-05-02 14:44:46 -07:00
reboot_fixups_32.c
relocate_kernel_32.S kexec, x86: Fix incorrect jump back address if not preserving context 2011-07-21 11:19:28 +02:00
relocate_kernel_64.S kexec, x86: Fix incorrect jump back address if not preserving context 2011-07-21 11:19:28 +02:00
resource.c
rtc.c x86/rtc, mrst: Don't register a platform RTC device for for Intel MID platforms 2011-12-05 17:09:21 +01:00
setup.c Merge branch 'x86-efi-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-11 19:12:33 -08:00
setup_percpu.c
signal.c signal: add block_sigmask() for adding sigmask to current->blocked 2012-01-10 16:30:54 -08:00
smp.c x86, reboot: Fix typo in nmi reboot path 2012-01-07 12:19:37 +01:00
smpboot.c Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-01-11 19:13:40 -08:00
stacktrace.c x86: Swap save_stack_trace_regs parameters 2011-06-14 22:48:51 -04:00
step.c x86-64: Add user_64bit_mode paravirt op 2011-08-04 16:13:49 -07:00
sys_i386_32.c
sys_x86_64.c x86, amd: Include linux/elf.h since we use stuff from asm/elf.h 2011-09-28 10:34:31 +02:00
syscall_32.c x86, syscall: Re-fix typo in comment 2011-11-18 16:25:07 -08:00
syscall_64.c x86: Generate system call tables and unistd_*.h from tables 2011-11-17 13:35:37 -08:00
tboot.c x86: Fix files explicitly requiring export.h for EXPORT_SYMBOL/THIS_MODULE 2011-10-31 19:30:35 -04:00
tce_64.c
test_nx.c x86: Eliminate various 'set but not used' warnings 2011-05-21 19:10:33 +02:00
test_rodata.c
time.c x86: Fix files explicitly requiring export.h for EXPORT_SYMBOL/THIS_MODULE 2011-10-31 19:30:35 -04:00
tls.c
tls.h
topology.c x86: Fix files explicitly requiring export.h for EXPORT_SYMBOL/THIS_MODULE 2011-10-31 19:30:35 -04:00
trampoline.c memblock, x86: Replace memblock_x86_reserve/free_range() with generic ones 2011-07-14 11:47:53 -07:00
trampoline_32.S
trampoline_64.S
traps.c i387: fix x86-64 preemption-unsafe user stack save/restore 2012-02-16 09:15:04 -08:00
tsc.c Merge remote-tracking branch 'linus/master' into x86/urgent 2012-01-19 12:56:50 -08:00
tsc_sync.c x86, tsc: Skip TSC synchronization checks for tsc=reliable 2011-12-05 18:00:31 +01:00
verify_cpu.S x86: Fix common misspellings 2011-03-18 10:39:30 +01:00
vm86_32.c x86-32: Fix build failure with AUDIT=y, AUDITSYSCALL=n 2012-01-17 18:10:11 -08:00
vmlinux.lds.S x86-64: Rework vsyscall emulation and add vsyscall= parameter 2011-08-10 19:26:46 -05:00
vsmp_64.c
vsyscall_64.c x86: Default to vsyscall=emulate 2011-12-05 12:17:29 +01:00
vsyscall_emu_64.S x86-64: Rework vsyscall emulation and add vsyscall= parameter 2011-08-10 19:26:46 -05:00
vsyscall_trace.h x86-64: Add vsyscall:emulate_vsyscall trace event 2011-08-04 16:13:53 -07:00
x86_init.c Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci 2012-01-11 18:50:26 -08:00
x8664_ksyms_64.c
xsave.c i387: fix x86-64 preemption-unsafe user stack save/restore 2012-02-16 09:15:04 -08:00