linux-stable.git/arch/x86/kernel/time.c, branch linux-5.4.y Linux kernel stable tree x86: stop playing stack games in profile_pc() 2024-07-05T07:08:28+00:00 Linus Torvalds torvalds@linux-foundation.org 2024-06-28T21:27:22+00:00 27c3be840911b15a3f24ed623f86153c825b6b29 [ Upstream commit 093d9603b60093a9aaae942db56107f6432a5dca ] The 'profile_pc()' function is used for timer-based profiling, which isn't really all that relevant any more to begin with, but it also ends up making assumptions based on the stack layout that aren't necessarily valid. Basically, the code tries to account the time spent in spinlocks to the caller rather than the spinlock, and while I support that as a concept, it's not worth the code complexity or the KASAN warnings when no serious profiling is done using timers anyway these days. And the code really does depend on stack layout that is only true in the simplest of cases. We've lost the comment at some point (I think when the 32-bit and 64-bit code was unified), but it used to say: Assume the lock function has either no stack frame or a copy of eflags from PUSHF. which explains why it just blindly loads a word or two straight off the stack pointer and then takes a minimal look at the values to just check if they might be eflags or the return pc: Eflags always has bits 22 and up cleared unlike kernel addresses but that basic stack layout assumption assumes that there isn't any lock debugging etc going on that would complicate the code and cause a stack frame. It causes KASAN unhappiness reported for years by syzkaller [1] and others [2]. With no real practical reason for this any more, just remove the code. Just for historical interest, here's some background commits relating to this code from 2006: 0cb91a229364 ("i386: Account spinlocks to the caller during profiling for !FP kernels") 31679f38d886 ("Simplify profile_pc on x86-64") and a code unification from 2009: ef4512882dbe ("x86: time_32/64.c unify profile_pc") but the basics of this thing actually goes back to before the git tree. Link: https://syzkaller.appspot.com/bug?extid=84fe685c02cd112a2ac3 [1] Link: https://lore.kernel.org/all/CAK55_s7Xyq=nh97=K=G1sxueOFrJDAvPOJAL4TPTCAYvmxO9_A@mail.gmail.com/ [2] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 093d9603b60093a9aaae942db56107f6432a5dca ]

The 'profile_pc()' function is used for timer-based profiling, which
isn't really all that relevant any more to begin with, but it also ends
up making assumptions based on the stack layout that aren't necessarily
valid.

Basically, the code tries to account the time spent in spinlocks to the
caller rather than the spinlock, and while I support that as a concept,
it's not worth the code complexity or the KASAN warnings when no serious
profiling is done using timers anyway these days.

And the code really does depend on stack layout that is only true in the
simplest of cases.  We've lost the comment at some point (I think when
the 32-bit and 64-bit code was unified), but it used to say:

	Assume the lock function has either no stack frame or a copy
	of eflags from PUSHF.

which explains why it just blindly loads a word or two straight off the
stack pointer and then takes a minimal look at the values to just check
if they might be eflags or the return pc:

	Eflags always has bits 22 and up cleared unlike kernel addresses

but that basic stack layout assumption assumes that there isn't any lock
debugging etc going on that would complicate the code and cause a stack
frame.

It causes KASAN unhappiness reported for years by syzkaller [1] and
others [2].

With no real practical reason for this any more, just remove the code.

Just for historical interest, here's some background commits relating to
this code from 2006:

  0cb91a229364 ("i386: Account spinlocks to the caller during profiling for !FP kernels")
  31679f38d886 ("Simplify profile_pc on x86-64")

and a code unification from 2009:

  ef4512882dbe ("x86: time_32/64.c unify profile_pc")

but the basics of this thing actually goes back to before the git tree.

Link: https://syzkaller.appspot.com/bug?extid=84fe685c02cd112a2ac3 [1]
Link: https://lore.kernel.org/all/CAK55_s7Xyq=nh97=K=G1sxueOFrJDAvPOJAL4TPTCAYvmxO9_A@mail.gmail.com/ [2]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
x86_64: Fix jiffies ODR violation 2020-06-17T14:40:24+00:00 Bob Haarman inglorion@google.com 2020-06-02T19:30:59+00:00 e8652fef53364ad412dfa0b63d56c9de3a1af09f commit d8ad6d39c35d2b44b3d48b787df7f3359381dcbf upstream. 'jiffies' and 'jiffies_64' are meant to alias (two different symbols that share the same address). Most architectures make the symbols alias to the same address via a linker script assignment in their arch/<arch>/kernel/vmlinux.lds.S: jiffies = jiffies_64; which is effectively a definition of jiffies. jiffies and jiffies_64 are both forward declared for all architectures in include/linux/jiffies.h. jiffies_64 is defined in kernel/time/timer.c. x86_64 was peculiar in that it wasn't doing the above linker script assignment, but rather was: 1. defining jiffies in arch/x86/kernel/time.c instead via the linker script. 2. overriding the symbol jiffies_64 from kernel/time/timer.c in arch/x86/kernel/vmlinux.lds.s via 'jiffies_64 = jiffies;'. As Fangrui notes: In LLD, symbol assignments in linker scripts override definitions in object files. GNU ld appears to have the same behavior. It would probably make sense for LLD to error "duplicate symbol" but GNU ld is unlikely to adopt for compatibility reasons. This results in an ODR violation (UB), which seems to have survived thus far. Where it becomes harmful is when; 1. -fno-semantic-interposition is used: As Fangrui notes: Clang after LLVM commit 5b22bcc2b70d ("[X86][ELF] Prefer to lower MC_GlobalAddress operands to .Lfoo$local") defaults to -fno-semantic-interposition similar semantics which help -fpic/-fPIC code avoid GOT/PLT when the referenced symbol is defined within the same translation unit. Unlike GCC -fno-semantic-interposition, Clang emits such relocations referencing local symbols for non-pic code as well. This causes references to jiffies to refer to '.Ljiffies$local' when jiffies is defined in the same translation unit. Likewise, references to jiffies_64 become references to '.Ljiffies_64$local' in translation units that define jiffies_64. Because these differ from the names used in the linker script, they will not be rewritten to alias one another. 2. Full LTO Full LTO effectively treats all source files as one translation unit, causing these local references to be produced everywhere. When the linker processes the linker script, there are no longer any references to jiffies_64' anywhere to replace with 'jiffies'. And thus '.Ljiffies$local' and '.Ljiffies_64$local' no longer alias at all. In the process of porting patches enabling Full LTO from arm64 to x86_64, spooky bugs have been observed where the kernel appeared to boot, but init doesn't get scheduled. Avoid the ODR violation by matching other architectures and define jiffies only by linker script. For -fno-semantic-interposition + Full LTO, there is no longer a global definition of jiffies for the compiler to produce a local symbol which the linker script won't ensure aliases to jiffies_64. Fixes: 40747ffa5aa8 ("asmlinkage: Make jiffies visible") Reported-by: Nathan Chancellor <natechancellor@gmail.com> Reported-by: Alistair Delva <adelva@google.com> Debugged-by: Nick Desaulniers <ndesaulniers@google.com> Debugged-by: Sami Tolvanen <samitolvanen@google.com> Suggested-by: Fangrui Song <maskray@google.com> Signed-off-by: Bob Haarman <inglorion@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # build+boot on Reviewed-by: Andi Kleen <ak@linux.intel.com> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: stable@vger.kernel.org Link: https://github.com/ClangBuiltLinux/linux/issues/852 Link: https://lkml.kernel.org/r/20200602193100.229287-1-inglorion@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit d8ad6d39c35d2b44b3d48b787df7f3359381dcbf upstream.

'jiffies' and 'jiffies_64' are meant to alias (two different symbols that
share the same address).  Most architectures make the symbols alias to the
same address via a linker script assignment in their
arch/<arch>/kernel/vmlinux.lds.S:

jiffies = jiffies_64;

which is effectively a definition of jiffies.

jiffies and jiffies_64 are both forward declared for all architectures in
include/linux/jiffies.h. jiffies_64 is defined in kernel/time/timer.c.

x86_64 was peculiar in that it wasn't doing the above linker script
assignment, but rather was:
1. defining jiffies in arch/x86/kernel/time.c instead via the linker script.
2. overriding the symbol jiffies_64 from kernel/time/timer.c in
arch/x86/kernel/vmlinux.lds.s via 'jiffies_64 = jiffies;'.

As Fangrui notes:

  In LLD, symbol assignments in linker scripts override definitions in
  object files. GNU ld appears to have the same behavior. It would
  probably make sense for LLD to error "duplicate symbol" but GNU ld
  is unlikely to adopt for compatibility reasons.

This results in an ODR violation (UB), which seems to have survived
thus far. Where it becomes harmful is when;

1. -fno-semantic-interposition is used:

As Fangrui notes:

  Clang after LLVM commit 5b22bcc2b70d
  ("[X86][ELF] Prefer to lower MC_GlobalAddress operands to .Lfoo$local")
  defaults to -fno-semantic-interposition similar semantics which help
  -fpic/-fPIC code avoid GOT/PLT when the referenced symbol is defined
  within the same translation unit. Unlike GCC
  -fno-semantic-interposition, Clang emits such relocations referencing
  local symbols for non-pic code as well.

This causes references to jiffies to refer to '.Ljiffies$local' when
jiffies is defined in the same translation unit. Likewise, references to
jiffies_64 become references to '.Ljiffies_64$local' in translation units
that define jiffies_64.  Because these differ from the names used in the
linker script, they will not be rewritten to alias one another.

2. Full LTO

Full LTO effectively treats all source files as one translation
unit, causing these local references to be produced everywhere.  When
the linker processes the linker script, there are no longer any
references to jiffies_64' anywhere to replace with 'jiffies'.  And
thus '.Ljiffies$local' and '.Ljiffies_64$local' no longer alias
at all.

In the process of porting patches enabling Full LTO from arm64 to x86_64,
spooky bugs have been observed where the kernel appeared to boot, but init
doesn't get scheduled.

Avoid the ODR violation by matching other architectures and define jiffies
only by linker script.  For -fno-semantic-interposition + Full LTO, there
is no longer a global definition of jiffies for the compiler to produce a
local symbol which the linker script won't ensure aliases to jiffies_64.

Fixes: 40747ffa5aa8 ("asmlinkage: Make jiffies visible")
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Reported-by: Alistair Delva <adelva@google.com>
Debugged-by: Nick Desaulniers <ndesaulniers@google.com>
Debugged-by: Sami Tolvanen <samitolvanen@google.com>
Suggested-by: Fangrui Song <maskray@google.com>
Signed-off-by: Bob Haarman <inglorion@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # build+boot on
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: stable@vger.kernel.org
Link: https://github.com/ClangBuiltLinux/linux/issues/852
Link: https://lkml.kernel.org/r/20200602193100.229287-1-inglorion@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
x86/timer: Don't skip PIT setup when APIC is disabled or in legacy mode 2020-02-11T12:35:52+00:00 Thomas Gleixner tglx@linutronix.de 2020-01-23T11:54:53+00:00 d0d327fe37cceb44db0ba9623018ddab9be22059 commit 979923871f69a4dc926658f9f9a1a4c1bde57552 upstream. Tony reported a boot regression caused by the recent workaround for systems which have a disabled (clock gate off) PIT. On his machine the kernel fails to initialize the PIT because apic_needs_pit() does not take into account whether the local APIC interrupt delivery mode will actually allow to setup and use the local APIC timer. This should be easy to reproduce with acpi=off on the command line which also disables HPET. Due to the way the PIT/HPET and APIC setup ordering works (APIC setup can require working PIT/HPET) the information is not available at the point where apic_needs_pit() makes this decision. To address this, split out the interrupt mode selection from apic_intr_mode_init(), invoke the selection before making the decision whether PIT is required or not, and add the missing checks into apic_needs_pit(). Fixes: c8c4076723da ("x86/timer: Skip PIT initialization on modern chipsets") Reported-by: Anthony Buckley <tony.buckley000@gmail.com> Tested-by: Anthony Buckley <tony.buckley000@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Daniel Drake <drake@endlessm.com> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206125 Link: https://lore.kernel.org/r/87sgk6tmk2.fsf@nanos.tec.linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 979923871f69a4dc926658f9f9a1a4c1bde57552 upstream.

Tony reported a boot regression caused by the recent workaround for systems
which have a disabled (clock gate off) PIT.

On his machine the kernel fails to initialize the PIT because
apic_needs_pit() does not take into account whether the local APIC
interrupt delivery mode will actually allow to setup and use the local
APIC timer. This should be easy to reproduce with acpi=off on the
command line which also disables HPET.

Due to the way the PIT/HPET and APIC setup ordering works (APIC setup can
require working PIT/HPET) the information is not available at the point
where apic_needs_pit() makes this decision.

To address this, split out the interrupt mode selection from
apic_intr_mode_init(), invoke the selection before making the decision
whether PIT is required or not, and add the missing checks into
apic_needs_pit().

Fixes: c8c4076723da ("x86/timer: Skip PIT initialization on modern chipsets")
Reported-by: Anthony Buckley <tony.buckley000@gmail.com>
Tested-by: Anthony Buckley <tony.buckley000@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Daniel Drake <drake@endlessm.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206125
Link: https://lore.kernel.org/r/87sgk6tmk2.fsf@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08T23:59:34+00:00 Linus Torvalds torvalds@linux-foundation.org 2019-07-08T23:59:34+00:00 a1aab6f3d295f078c008893ee7fa2c011626c46f Pull x86 asm updates from Ingo Molnar: "Most of the changes relate to Peter Zijlstra's cleanup of ptregs handling, in particular the i386 part is now much simplified and standardized - no more partial ptregs stack frames via the esp/ss oddity. This simplifies ftrace, kprobes, the unwinder, ptrace, kdump and kgdb. There's also a CR4 hardening enhancements by Kees Cook, to make the generic platform functions such as native_write_cr4() less useful as ROP gadgets that disable SMEP/SMAP. Also protect the WP bit of CR0 against similar attacks. The rest is smaller cleanups/fixes" * 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/alternatives: Add int3_emulate_call() selftest x86/stackframe/32: Allow int3_emulate_push() x86/stackframe/32: Provide consistent pt_regs x86/stackframe, x86/ftrace: Add pt_regs frame annotations x86/stackframe, x86/kprobes: Fix frame pointer annotations x86/stackframe: Move ENCODE_FRAME_POINTER to asm/frame.h x86/entry/32: Clean up return from interrupt preemption path x86/asm: Pin sensitive CR0 bits x86/asm: Pin sensitive CR4 bits Documentation/x86: Fix path to entry_32.S x86/asm: Remove unused TASK_TI_flags from asm-offsets.c 
Pull x86 asm updates from Ingo Molnar:
 "Most of the changes relate to Peter Zijlstra's cleanup of ptregs
  handling, in particular the i386 part is now much simplified and
  standardized - no more partial ptregs stack frames via the esp/ss
  oddity. This simplifies ftrace, kprobes, the unwinder, ptrace, kdump
  and kgdb.

  There's also a CR4 hardening enhancements by Kees Cook, to make the
  generic platform functions such as native_write_cr4() less useful as
  ROP gadgets that disable SMEP/SMAP. Also protect the WP bit of CR0
  against similar attacks.

  The rest is smaller cleanups/fixes"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/alternatives: Add int3_emulate_call() selftest
  x86/stackframe/32: Allow int3_emulate_push()
  x86/stackframe/32: Provide consistent pt_regs
  x86/stackframe, x86/ftrace: Add pt_regs frame annotations
  x86/stackframe, x86/kprobes: Fix frame pointer annotations
  x86/stackframe: Move ENCODE_FRAME_POINTER to asm/frame.h
  x86/entry/32: Clean up return from interrupt preemption path
  x86/asm: Pin sensitive CR0 bits
  x86/asm: Pin sensitive CR4 bits
  Documentation/x86: Fix path to entry_32.S
  x86/asm: Remove unused TASK_TI_flags from asm-offsets.c
x86/timer: Skip PIT initialization on modern chipsets 2019-06-29T09:35:35+00:00 Thomas Gleixner tglx@linutronix.de 2019-06-28T07:23:07+00:00 c8c4076723daca08bf35ccd68f22ea1c6219e207 Recent Intel chipsets including Skylake and ApolloLake have a special ITSSPRC register which allows the 8254 PIT to be gated. When gated, the 8254 registers can still be programmed as normal, but there are no IRQ0 timer interrupts. Some products such as the Connex L1430 and exone go Rugged E11 use this register to ship with the PIT gated by default. This causes Linux to fail to boot: Kernel panic - not syncing: IO-APIC + timer doesn't work! Boot with apic=debug and send a report. The panic happens before the framebuffer is initialized, so to the user, it appears as an early boot hang on a black screen. Affected products typically have a BIOS option that can be used to enable the 8254 and make Linux work (Chipset -> South Cluster Configuration -> Miscellaneous Configuration -> 8254 Clock Gating), however it would be best to make Linux support the no-8254 case. Modern sytems allow to discover the TSC and local APIC timer frequencies, so the calibration against the PIT is not required. These systems have always running timers and the local APIC timer works also in deep power states. So the setup of the PIT including the IO-APIC timer interrupt delivery checks are a pointless exercise. Skip the PIT setup and the IO-APIC timer interrupt checks on these systems, which avoids the panic caused by non ticking PITs and also speeds up the boot process. Thanks to Daniel for providing the changelog, initial analysis of the problem and testing against a variety of machines. Reported-by: Daniel Drake <drake@endlessm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Daniel Drake <drake@endlessm.com> Cc: bp@alien8.de Cc: hpa@zytor.com Cc: linux@endlessm.com Cc: rafael.j.wysocki@intel.com Cc: hdegoede@redhat.com Link: https://lkml.kernel.org/r/20190628072307.24678-1-drake@endlessm.com 
Recent Intel chipsets including Skylake and ApolloLake have a special
ITSSPRC register which allows the 8254 PIT to be gated.  When gated, the
8254 registers can still be programmed as normal, but there are no IRQ0
timer interrupts.

Some products such as the Connex L1430 and exone go Rugged E11 use this
register to ship with the PIT gated by default. This causes Linux to fail
to boot:

  Kernel panic - not syncing: IO-APIC + timer doesn't work! Boot with
  apic=debug and send a report.

The panic happens before the framebuffer is initialized, so to the user, it
appears as an early boot hang on a black screen.

Affected products typically have a BIOS option that can be used to enable
the 8254 and make Linux work (Chipset -> South Cluster Configuration ->
Miscellaneous Configuration -> 8254 Clock Gating), however it would be best
to make Linux support the no-8254 case.

Modern sytems allow to discover the TSC and local APIC timer frequencies,
so the calibration against the PIT is not required. These systems have
always running timers and the local APIC timer works also in deep power
states.

So the setup of the PIT including the IO-APIC timer interrupt delivery
checks are a pointless exercise.

Skip the PIT setup and the IO-APIC timer interrupt checks on these systems,
which avoids the panic caused by non ticking PITs and also speeds up the
boot process.

Thanks to Daniel for providing the changelog, initial analysis of the
problem and testing against a variety of machines.

Reported-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Daniel Drake <drake@endlessm.com>
Cc: bp@alien8.de
Cc: hpa@zytor.com
Cc: linux@endlessm.com
Cc: rafael.j.wysocki@intel.com
Cc: hdegoede@redhat.com
Link: https://lkml.kernel.org/r/20190628072307.24678-1-drake@endlessm.com
x86/stackframe/32: Provide consistent pt_regs 2019-06-25T08:23:47+00:00 Peter Zijlstra peterz@infradead.org 2019-05-07T21:25:54+00:00 3c88c692c28746473791276f8b42d2c989d6cbe6 Currently pt_regs on x86_32 has an oddity in that kernel regs (!user_mode(regs)) are short two entries (esp/ss). This means that any code trying to use them (typically: regs->sp) needs to jump through some unfortunate hoops. Change the entry code to fix this up and create a full pt_regs frame. This then simplifies various trampolines in ftrace and kprobes, the stack unwinder, ptrace, kdump and kgdb. Much thanks to Josh for help with the cleanups! Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> 
Currently pt_regs on x86_32 has an oddity in that kernel regs
(!user_mode(regs)) are short two entries (esp/ss). This means that any
code trying to use them (typically: regs->sp) needs to jump through
some unfortunate hoops.

Change the entry code to fix this up and create a full pt_regs frame.

This then simplifies various trampolines in ftrace and kprobes, the
stack unwinder, ptrace, kdump and kgdb.

Much thanks to Josh for help with the cleanups!

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-10-23T18:07:25+00:00 Linus Torvalds torvalds@linux-foundation.org 2018-10-23T18:07:25+00:00 034bda1cd5abbe7b170ce76b618768d164030bbd Pull x86 vdso updates from Ingo Molnar: "Two main changes: - Cleanups, simplifications and CLOCK_TAI support (Thomas Gleixner) - Improve code generation (Andy Lutomirski)" * 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/vdso: Rearrange do_hres() to improve code generation x86/vdso: Document vgtod_ts better x86/vdso: Remove "memory" clobbers in the vDSO syscall fallbacks x66/vdso: Add CLOCK_TAI support x86/vdso: Move cycle_last handling into the caller x86/vdso: Simplify the invalid vclock case x86/vdso: Replace the clockid switch case x86/vdso: Collapse coarse functions x86/vdso: Collapse high resolution functions x86/vdso: Introduce and use vgtod_ts x86/vdso: Use unsigned int consistently for vsyscall_gtod_data:: Seq x86/vdso: Enforce 64bit clocksource x86/time: Implement clocksource_arch_init() clocksource: Provide clocksource_arch_init() 
Pull x86 vdso updates from Ingo Molnar:
 "Two main changes:

   - Cleanups, simplifications and CLOCK_TAI support (Thomas Gleixner)

   - Improve code generation (Andy Lutomirski)"

* 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/vdso: Rearrange do_hres() to improve code generation
  x86/vdso: Document vgtod_ts better
  x86/vdso: Remove "memory" clobbers in the vDSO syscall fallbacks
  x66/vdso: Add CLOCK_TAI support
  x86/vdso: Move cycle_last handling into the caller
  x86/vdso: Simplify the invalid vclock case
  x86/vdso: Replace the clockid switch case
  x86/vdso: Collapse coarse functions
  x86/vdso: Collapse high resolution functions
  x86/vdso: Introduce and use vgtod_ts
  x86/vdso: Use unsigned int consistently for vsyscall_gtod_data:: Seq
  x86/vdso: Enforce 64bit clocksource
  x86/time: Implement clocksource_arch_init()
  clocksource: Provide clocksource_arch_init()
x86/time: Correct the attribute on jiffies' definition 2018-10-14T09:11:23+00:00 Nathan Chancellor natechancellor@gmail.com 2018-10-13T00:53:12+00:00 53c13ba8ed39e89f21a0b98f4c8a241bb44e483d Clang warns that the declaration of jiffies in include/linux/jiffies.h doesn't match the definition in arch/x86/time/kernel.c: arch/x86/kernel/time.c:29:42: warning: section does not match previous declaration [-Wsection] __visible volatile unsigned long jiffies __cacheline_aligned = INITIAL_JIFFIES; ^ ./include/linux/cache.h:49:4: note: expanded from macro '__cacheline_aligned' __section__(".data..cacheline_aligned"))) ^ ./include/linux/jiffies.h:81:31: note: previous attribute is here extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies; ^ ./arch/x86/include/asm/cache.h:20:2: note: expanded from macro '__cacheline_aligned_in_smp' __page_aligned_data ^ ./include/linux/linkage.h:39:29: note: expanded from macro '__page_aligned_data' #define __page_aligned_data __section(.data..page_aligned) __aligned(PAGE_SIZE) ^ ./include/linux/compiler_attributes.h:233:56: note: expanded from macro '__section' #define __section(S) __attribute__((__section__(#S))) ^ 1 warning generated. The declaration was changed in commit 7c30f352c852 ("jiffies.h: declare jiffies and jiffies_64 with ____cacheline_aligned_in_smp") but wasn't updated here. Make them match so Clang no longer warns. Fixes: 7c30f352c852 ("jiffies.h: declare jiffies and jiffies_64 with ____cacheline_aligned_in_smp") Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181013005311.28617-1-natechancellor@gmail.com 
Clang warns that the declaration of jiffies in include/linux/jiffies.h
doesn't match the definition in arch/x86/time/kernel.c:

arch/x86/kernel/time.c:29:42: warning: section does not match previous declaration [-Wsection]
__visible volatile unsigned long jiffies __cacheline_aligned = INITIAL_JIFFIES;
                                         ^
./include/linux/cache.h:49:4: note: expanded from macro '__cacheline_aligned'
                 __section__(".data..cacheline_aligned")))
                 ^
./include/linux/jiffies.h:81:31: note: previous attribute is here
extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies;
                              ^
./arch/x86/include/asm/cache.h:20:2: note: expanded from macro '__cacheline_aligned_in_smp'
        __page_aligned_data
        ^
./include/linux/linkage.h:39:29: note: expanded from macro '__page_aligned_data'
#define __page_aligned_data     __section(.data..page_aligned) __aligned(PAGE_SIZE)
                                ^
./include/linux/compiler_attributes.h:233:56: note: expanded from macro '__section'
#define __section(S)                    __attribute__((__section__(#S)))
                                                       ^
1 warning generated.

The declaration was changed in commit 7c30f352c852 ("jiffies.h: declare
jiffies and jiffies_64 with ____cacheline_aligned_in_smp") but wasn't
updated here. Make them match so Clang no longer warns.

Fixes: 7c30f352c852 ("jiffies.h: declare jiffies and jiffies_64 with ____cacheline_aligned_in_smp")
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181013005311.28617-1-natechancellor@gmail.com
x86/vdso: Enforce 64bit clocksource 2018-10-04T21:00:25+00:00 Thomas Gleixner tglx@linutronix.de 2018-09-17T12:45:36+00:00 a51e996d48ac9fa0a1260a3822a14f3d570d3be7 All VDSO clock sources are TSC based and use CLOCKSOURCE_MASK(64). There is no point in masking with all FF. Get rid of it and enforce the mask in the sanity checker. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Matt Rickard <matt@softrans.com.au> Cc: Stephen Boyd <sboyd@kernel.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Florian Weimer <fweimer@redhat.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: devel@linuxdriverproject.org Cc: virtualization@lists.linux-foundation.org Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Juergen Gross <jgross@suse.com> Link: https://lkml.kernel.org/r/20180917130707.151963007@linutronix.de 
All VDSO clock sources are TSC based and use CLOCKSOURCE_MASK(64). There is
no point in masking with all FF. Get rid of it and enforce the mask in the
sanity checker.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Rickard <matt@softrans.com.au>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: devel@linuxdriverproject.org
Cc: virtualization@lists.linux-foundation.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Juergen Gross <jgross@suse.com>
Link: https://lkml.kernel.org/r/20180917130707.151963007@linutronix.de
x86/time: Implement clocksource_arch_init() 2018-10-04T21:00:24+00:00 Thomas Gleixner tglx@linutronix.de 2018-09-17T12:45:35+00:00 2a21ad571b62440a4ad66d70b4b5d09c00029af4 Runtime validate the VCLOCK_MODE in clocksource::archdata and disable VCLOCK if invalid, which disables the VDSO but keeps the system running. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Matt Rickard <matt@softrans.com.au> Cc: Stephen Boyd <sboyd@kernel.org> Cc: John Stultz <john.stultz@linaro.org> Cc: Florian Weimer <fweimer@redhat.com> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: devel@linuxdriverproject.org Cc: virtualization@lists.linux-foundation.org Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Juergen Gross <jgross@suse.com> Link: https://lkml.kernel.org/r/20180917130707.069167446@linutronix.de 
Runtime validate the VCLOCK_MODE in clocksource::archdata and disable
VCLOCK if invalid, which disables the VDSO but keeps the system running.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Rickard <matt@softrans.com.au>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: devel@linuxdriverproject.org
Cc: virtualization@lists.linux-foundation.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Juergen Gross <jgross@suse.com>
Link: https://lkml.kernel.org/r/20180917130707.069167446@linutronix.de