Merge tag 'v6.6.37' into dev-6.6

This is the 6.6.37 stable release

x86: stop playing stack games in profile_pc()

[ Upstream commit 093d9603b60093a9aaae942db56107f6432a5dca ]

The 'profile_pc()' function is used for timer-based profiling, which
isn't really all that

x86: stop playing stack games in profile_pc()

[ 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>

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Merge branch 'next' into for-linus

Prepare input updates for 5.11 merge window.

Merge tag 'v5.9' into next

Sync up with mainline to bring in the latest DTS files.

Merge branch 'master' into for-next

Sync with Linus' branch in order to be able to apply fixups
of more recent patches.

Merge branch 'next' into for-linus

Prepare input updates for 5.9 merge window.

Merge branch 'for-next' into for-linus

Merge branch 'elan-i2c' into next

Bring in update to Elan touchpad driver to support newer touchpads with
higher resolution.

Merge tag 'irqchip-fixes-5.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/urgent

Pull irqchip fixes from Marc Zyngier:

- Fix atomicity of affinity update in the G

Merge tag 'irqchip-fixes-5.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/urgent

Pull irqchip fixes from Marc Zyngier:

- Fix atomicity of affinity update in the GIC driver
- Don't sleep in atomic when waiting for a GICv4.1 RD to respond
- Fix a couple of typos in user-visible messages

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Merge tag 'v5.8-rc3' into arm/qcom

Linux 5.8-rc3

Backmerge remote-tracking branch 'drm/drm-next' into drm-misc-next

Some conflicts with ttm_bo->offset removal, but drm-misc-next needs updating to v5.8.

Signed-off-by: Maarten Lankhorst <maarten.la

Backmerge remote-tracking branch 'drm/drm-next' into drm-misc-next

Some conflicts with ttm_bo->offset removal, but drm-misc-next needs updating to v5.8.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

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Merge drm/drm-next into drm-intel-next-queued

Catch up with upstream, in particular to get c1e8d7c6a7a6 ("mmap locking
API: convert mmap_sem comments").

Signed-off-by: Jani Nikula <jani.nikula@inte

Merge drm/drm-next into drm-intel-next-queued

Catch up with upstream, in particular to get c1e8d7c6a7a6 ("mmap locking
API: convert mmap_sem comments").

Signed-off-by: Jani Nikula <jani.nikula@intel.com>

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Merge remote-tracking branch 'torvalds/master' into perf/urgent

To get some newer headers that got out of sync with the copies in tools/
so that we can try to have the tools/perf/ build clean for v5

Merge remote-tracking branch 'torvalds/master' into perf/urgent

To get some newer headers that got out of sync with the copies in tools/
so that we can try to have the tools/perf/ build clean for v5.8 with
fewer pull requests.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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Merge tag 'v5.8-rc1' into regulator-5.8

Linux 5.8-rc1

Merge tag 'v5.8-rc1' into fixes

Linux 5.8-rc1

Merge v5.8-rc1 into drm-misc-fixes

Beginning a new release cycles for what will become v5.8. Updating
drm-misc-fixes accordingly.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

Merge branch 'dt/schema-cleanups' into dt/linus

Merge tag 'x86-urgent-2020-06-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull more x86 updates from Thomas Gleixner:
"A set of fixes and updates for x86:

- Unbreak paravirt VD

Merge tag 'x86-urgent-2020-06-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull more x86 updates from Thomas Gleixner:
"A set of fixes and updates for x86:

- Unbreak paravirt VDSO clocks.

While the VDSO code was moved into lib for sharing a subtle check
for the validity of paravirt clocks got replaced. While the
replacement works perfectly fine for bare metal as the update of
the VDSO clock mode is synchronous, it fails for paravirt clocks
because the hypervisor can invalidate them asynchronously.

Bring it back as an optional function so it does not inflict this
on architectures which are free of PV damage.

- Fix the jiffies to jiffies64 mapping on 64bit so it does not
trigger an ODR violation on newer compilers

- Three fixes for the SSBD and *IB* speculation mitigation maze to
ensure consistency, not disabling of some *IB* variants wrongly and
to prevent a rogue cross process shutdown of SSBD. All marked for
stable.

- Add yet more CPU models to the splitlock detection capable list
!@#%$!

- Bring the pr_info() back which tells that TSC deadline timer is
enabled.

- Reboot quirk for MacBook6,1"

* tag 'x86-urgent-2020-06-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/vdso: Unbreak paravirt VDSO clocks
lib/vdso: Provide sanity check for cycles (again)
clocksource: Remove obsolete ifdef
x86_64: Fix jiffies ODR violation
x86/speculation: PR_SPEC_FORCE_DISABLE enforcement for indirect branches.
x86/speculation: Prevent rogue cross-process SSBD shutdown
x86/speculation: Avoid force-disabling IBPB based on STIBP and enhanced IBRS.
x86/cpu: Add Sapphire Rapids CPU model number
x86/split_lock: Add Icelake microserver and Tigerlake CPU models
x86/apic: Make TSC deadline timer detection message visible
x86/reboot/quirks: Add MacBook6,1 reboot quirk

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Merge branch 'x86/entry' into ras/core

to fixup conflicts in arch/x86/kernel/cpu/mce/core.c so MCE specific follow
up patches can be applied without creating a horrible merge conflict
afterwards.

x86_64: Fix jiffies ODR violation

'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 vi

x86_64: Fix jiffies ODR violation

'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

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Merge branch 'next' into for-linus

Prepare input updates for 5.8 merge window.

Merge tag 'x86-timers-2020-06-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 timer updates from Thomas Gleixner:
"X86 timer specific updates:

- Add TPAUSE based delay whi

Merge tag 'x86-timers-2020-06-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 timer updates from Thomas Gleixner:
"X86 timer specific updates:

- Add TPAUSE based delay which allows the CPU to enter an optimized
power state while waiting for the delay to pass. The delay is based
on TSC cycles.

- Add tsc_early_khz command line parameter to workaround the problem
that overclocked CPUs can report the wrong frequency via CPUID.16h
which causes the refined calibration to fail because the delta to
the initial frequency value is too big. With the parameter users
can provide an halfways accurate initial value"

* tag 'x86-timers-2020-06-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/tsc: Add tsc_early_khz command line parameter
x86/delay: Introduce TPAUSE delay
x86/delay: Refactor delay_mwaitx() for TPAUSE support
x86/delay: Preparatory code cleanup

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Merge branch 'for-5.8' into for-linus

Merge branch 'timers/drivers/timer-ti' into timers/drivers/next

Merge tag 'v5.6' into next

Sync up with mainline to get device tree and other changes.