While most of a task's FPU state is only needed in user space, the
protection keys need to be in place immediately after a context switch.
The reason is that any access to userspace memory while running in
kernel mode also needs to abide by the memory permissions specified in
the protection keys.
The "eager switch" is a preparation for loading the FPU state on return
to userland. Instead of decoupling PKRU state from xstate, update PKRU
within xstate on write operations by the kernel.
For user tasks the PKRU should be always read from the xsave area and it
should not change anything because the PKRU value was loaded as part of
FPU restore.
For kernel threads the default "init_pkru_value" will be written. Before
this commit, the kernel thread would end up with a random value which it
inherited from the previous user task.
[ bigeasy: save pkru to xstate, no cache, don't use __raw_xsave_addr() ]
[ bp: update commit message, sort headers properly in asm/fpu/xstate.h ]
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aubrey Li <aubrey.li@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Juergen Gross <jgross@suse.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-16-bigeasy@linutronix.de
user_fpu_begin() sets fpu_fpregs_owner_ctx to task's fpu struct. This is
always the case since there is no lazy FPU anymore.
fpu_fpregs_owner_ctx is used during context switch to decide if it needs
to load the saved registers or if the currently loaded registers are
valid. It could be skipped during a
taskA -> kernel thread -> taskA
switch because the switch to the kernel thread would not alter the CPU's
sFPU tate.
Since this field is always updated during context switch and
never invalidated, setting it manually (in user context) makes no
difference. A kernel thread with kernel_fpu_begin() block could
set fpu_fpregs_owner_ctx to NULL but a kernel thread does not use
user_fpu_begin().
This is a leftover from the lazy-FPU time.
Remove user_fpu_begin(), it does not change fpu_fpregs_owner_ctx's
content.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aubrey Li <aubrey.li@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-9-bigeasy@linutronix.de
The struct fpu.initialized member is always set to one for user tasks
and zero for kernel tasks. This avoids saving/restoring the FPU
registers for kernel threads.
The ->initialized = 0 case for user tasks has been removed in previous
changes, for instance, by doing an explicit unconditional init at fork()
time for FPU-less systems which was otherwise delayed until the emulated
opcode.
The context switch code (switch_fpu_prepare() + switch_fpu_finish())
can't unconditionally save/restore registers for kernel threads. Not
only would it slow down the switch but also load a zeroed xcomp_bv for
XSAVES.
For kernel_fpu_begin() (+end) the situation is similar: EFI with runtime
services uses this before alternatives_patched is true. Which means that
this function is used too early and it wasn't the case before.
For those two cases, use current->mm to distinguish between user and
kernel thread. For kernel_fpu_begin() skip save/restore of the FPU
registers.
During the context switch into a kernel thread don't do anything. There
is no reason to save the FPU state of a kernel thread.
The reordering in __switch_to() is important because the current()
pointer needs to be valid before switch_fpu_finish() is invoked so ->mm
is seen of the new task instead the old one.
N.B.: fpu__save() doesn't need to check ->mm because it is called by
user tasks only.
[ bp: Massage. ]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aubrey Li <aubrey.li@intel.com>
Cc: Babu Moger <Babu.Moger@amd.com>
Cc: "Chang S. Bae" <chang.seok.bae@intel.com>
Cc: Dmitry Safonov <dima@arista.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-8-bigeasy@linutronix.de
In commit
72a671ced6 ("x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels")
the 32bit and 64bit path of the signal delivery code were merged.
The 32bit version:
int save_i387_xstate_ia32(void __user *buf)
…
if (cpu_has_xsave)
return save_i387_xsave(fp);
if (cpu_has_fxsr)
return save_i387_fxsave(fp);
The 64bit version:
int save_i387_xstate(void __user *buf)
…
if (user_has_fpu()) {
if (use_xsave())
err = xsave_user(buf);
else
err = fxsave_user(buf);
if (unlikely(err)) {
__clear_user(buf, xstate_size);
return err;
The merge:
int save_xstate_sig(void __user *buf, void __user *buf_fx, int size)
…
if (user_has_fpu()) {
/* Save the live register state to the user directly. */
if (save_user_xstate(buf_fx))
return -1;
/* Update the thread's fxstate to save the fsave header. */
if (ia32_fxstate)
fpu_fxsave(&tsk->thread.fpu);
I don't think that we needed to save the FPU registers to ->thread.fpu
because the registers were stored in buf_fx. Today the state will be
restored from buf_fx after the signal was handled (I assume that this
was also the case with lazy-FPU).
Since commit
66463db4fc ("x86, fpu: shift drop_init_fpu() from save_xstate_sig() to handle_signal()")
it is ensured that the signal handler starts with clear/fresh set of FPU
registers which means that the previous store is futile.
Remove the copy_fxregs_to_kernel() call because task's FPU state is
cleared later in handle_signal() via fpu__clear().
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-7-bigeasy@linutronix.de
With lazy-FPU support the (now named variable) ->initialized was set to
true if the CPU's FPU registers were holding a valid state of the
FPU registers for the active process. If it was set to false then the
FPU state was saved in fpu->state and the FPU was deactivated.
With lazy-FPU gone, ->initialized is always true for user threads and
kernel threads never call this function so ->initialized is always true
in copy_fpstate_to_sigframe().
The using_compacted_format() check is also a leftover from the lazy-FPU
time. In the
->initialized == false
case copy_to_user() would copy the compacted buffer while userland would
expect the non-compacted format instead. So in order to save the FPU
state in the non-compacted form it issues XSAVE to save the *current*
FPU state.
If the FPU is not enabled, the attempt raises the FPU trap, the trap
restores the FPU contents and re-enables the FPU and XSAVE is invoked
again and succeeds.
*This* does not longer work since commit
bef8b6da95 ("x86/fpu: Handle #NM without FPU emulation as an error")
Remove the check for ->initialized because it is always true and remove
the false condition. Update the comment to reflect that the state is
always live.
[ bp: Massage. ]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-6-bigeasy@linutronix.de
The preempt_disable() section was introduced in commit
a10b6a16cd ("x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic")
and it was said to be temporary.
fpu__initialize() initializes the FPU struct to its initial value and
then sets ->initialized to 1. The last part is the important one.
The content of the state does not matter because it gets set via
copy_init_fpstate_to_fpregs().
A preemption here has little meaning because the registers will always be
set to the same content after copy_init_fpstate_to_fpregs(). A softirq
with a kernel_fpu_begin() could also force to save FPU's registers after
fpu__initialize() without changing the outcome here.
Remove the preempt_disable() section in fpu__clear(), preemption here
does not hurt.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-4-bigeasy@linutronix.de
This is a preparation for the removal of the ->initialized member in the
fpu struct.
__fpu__restore_sig() is deactivating the FPU via fpu__drop() and then
setting manually ->initialized followed by fpu__restore(). The result is
that it is possible to manipulate fpu->state and the state of registers
won't be saved/restored on a context switch which would overwrite
fpu->state:
fpu__drop(fpu):
...
fpu->initialized = 0;
preempt_enable();
<--- context switch
Don't access the fpu->state while the content is read from user space
and examined/sanitized. Use a temporary kmalloc() buffer for the
preparation of the FPU registers and once the state is considered okay,
load it. Should something go wrong, return with an error and without
altering the original FPU registers.
The removal of fpu__initialize() is a nop because fpu->initialized is
already set for the user task.
[ bp: Massage a bit. ]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-2-bigeasy@linutronix.de
Pull KVM fixes from Paolo Bonzini:
"A collection of x86 and ARM bugfixes, and some improvements to
documentation.
On top of this, a cleanup of kvm_para.h headers, which were exported
by some architectures even though they not support KVM at all. This is
responsible for all the Kbuild changes in the diffstat"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (28 commits)
Documentation: kvm: clarify KVM_SET_USER_MEMORY_REGION
KVM: doc: Document the life cycle of a VM and its resources
KVM: selftests: complete IO before migrating guest state
KVM: selftests: disable stack protector for all KVM tests
KVM: selftests: explicitly disable PIE for tests
KVM: selftests: assert on exit reason in CR4/cpuid sync test
KVM: x86: update %rip after emulating IO
x86/kvm/hyper-v: avoid spurious pending stimer on vCPU init
kvm/x86: Move MSR_IA32_ARCH_CAPABILITIES to array emulated_msrs
KVM: x86: Emulate MSR_IA32_ARCH_CAPABILITIES on AMD hosts
kvm: don't redefine flags as something else
kvm: mmu: Used range based flushing in slot_handle_level_range
KVM: export <linux/kvm_para.h> and <asm/kvm_para.h> iif KVM is supported
KVM: x86: remove check on nr_mmu_pages in kvm_arch_commit_memory_region()
kvm: nVMX: Add a vmentry check for HOST_SYSENTER_ESP and HOST_SYSENTER_EIP fields
KVM: SVM: Workaround errata#1096 (insn_len maybe zero on SMAP violation)
KVM: Reject device ioctls from processes other than the VM's creator
KVM: doc: Fix incorrect word ordering regarding supported use of APIs
KVM: x86: fix handling of role.cr4_pae and rename it to 'gpte_size'
KVM: nVMX: Do not inherit quadrant and invalid for the root shadow EPT
...
Pull x86 fixes from Thomas Gleixner:
"A pile of x86 updates:
- Prevent exceeding he valid physical address space in the /dev/mem
limit checks.
- Move all header content inside the header guard to prevent compile
failures.
- Fix the bogus __percpu annotation in this_cpu_has() which makes
sparse very noisy.
- Disable switch jump tables completely when retpolines are enabled.
- Prevent leaking the trampoline address"
* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/realmode: Make set_real_mode_mem() static inline
x86/cpufeature: Fix __percpu annotation in this_cpu_has()
x86/mm: Don't exceed the valid physical address space
x86/retpolines: Disable switch jump tables when retpolines are enabled
x86/realmode: Don't leak the trampoline kernel address
x86/boot: Fix incorrect ifdeffery scope
x86/resctrl: Remove unused variable
Pull perf tooling fixes from Thomas Gleixner:
"Core libraries:
- Fix max perf_event_attr.precise_ip detection.
- Fix parser error for uncore event alias
- Fixup ordering of kernel maps after obtaining the main kernel map
address.
Intel PT:
- Fix TSC slip where A TSC packet can slip past MTC packets so that
the timestamp appears to go backwards.
- Fixes for exported-sql-viewer GUI conversion to python3.
ARM coresight:
- Fix the build by adding a missing case value for enumeration value
introduced in newer library, that now is the required one.
tool headers:
- Syncronize kernel headers with the kernel, getting new io_uring and
pidfd_send_signal syscalls so that 'perf trace' can handle them"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf pmu: Fix parser error for uncore event alias
perf scripts python: exported-sql-viewer.py: Fix python3 support
perf scripts python: exported-sql-viewer.py: Fix never-ending loop
perf machine: Update kernel map address and re-order properly
tools headers uapi: Sync powerpc's asm/kvm.h copy with the kernel sources
tools headers: Update x86's syscall_64.tbl and uapi/asm-generic/unistd
tools headers uapi: Update drm/i915_drm.h
tools arch x86: Sync asm/cpufeatures.h with the kernel sources
tools headers uapi: Sync linux/fcntl.h to get the F_SEAL_FUTURE_WRITE addition
tools headers uapi: Sync asm-generic/mman-common.h and linux/mman.h
perf evsel: Fix max perf_event_attr.precise_ip detection
perf intel-pt: Fix TSC slip
perf cs-etm: Add missing case value
Pull CPU hotplug fixes from Thomas Gleixner:
"Two SMT/hotplug related fixes:
- Prevent crash when HOTPLUG_CPU is disabled and the CPU bringup
aborts. This is triggered with the 'nosmt' command line option, but
can happen by any abort condition. As the real unplug code is not
compiled in, prevent the fail by keeping the CPU in zombie state.
- Enforce HOTPLUG_CPU for SMP on x86 to avoid the above situation
completely. With 'nosmt' being a popular option it's required to
unplug the half brought up sibling CPUs (due to the MCE wreckage)
completely"
* 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/smp: Enforce CONFIG_HOTPLUG_CPU when SMP=y
cpu/hotplug: Prevent crash when CPU bringup fails on CONFIG_HOTPLUG_CPU=n
Pull locking fixlet from Thomas Gleixner:
"Trivial update to the maintainers file"
* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
MAINTAINERS: Remove deleted file from futex file pattern
Pull core fixes from Thomas Gleixner:
"A small set of core updates:
- Make the watchdog respect the selected CPU mask again. That was
broken by the rework of the watchdog thread management and caused
inconsistent state and NMI watchdog being unstoppable.
- Ensure that the objtool build can find the libelf location.
- Remove dead kcore stub code"
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
watchdog: Respect watchdog cpumask on CPU hotplug
objtool: Query pkg-config for libelf location
proc/kcore: Remove unused kclist_add_remap()
Pull powerpc fixes from Michael Ellerman:
"Three non-regression fixes.
- Our optimised memcmp could read past the end of one of the buffers
and potentially trigger a page fault leading to an oops.
- Some of our code to read energy management data on PowerVM had an
endian bug leading to bogus results.
- When reporting a machine check exception we incorrectly reported
TLB multihits as D-Cache multhits due to a missing entry in the
array of causes.
Thanks to: Chandan Rajendra, Gautham R. Shenoy, Mahesh Salgaonkar,
Segher Boessenkool, Vaidyanathan Srinivasan"
* tag 'powerpc-5.1-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/pseries/mce: Fix misleading print for TLB mutlihit
powerpc/pseries/energy: Use OF accessor functions to read ibm,drc-indexes
powerpc/64: Fix memcmp reading past the end of src/dest
