[ 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>
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
'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
TPAUSE instructs the processor to enter an implementation-dependent optimized state. The instruction execution wakes up when the time-stamp counter reaches or exceeds the implicit EDX:EAX 64-bit input value. The instruction execution also wakes up due to the expiration of the operating system time-limit or by an external interrupt or exceptions such as a debug exception or a machine check exception. TPAUSE offers a choice of two lower power states: 1. Light-weight power/performance optimized state C0.1 2. Improved power/performance optimized state C0.2 This way, it can save power with low wake-up latency in comparison to spinloop based delay. The selection between the two is governed by the input register. TPAUSE is available on processors with X86_FEATURE_WAITPKG. Co-developed-by: Fenghua Yu <fenghua.yu@intel.com> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> Signed-off-by: Kyung Min Park <kyung.min.park@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Tony Luck <tony.luck@intel.com> Link: https://lkml.kernel.org/r/1587757076-30337-4-git-send-email-kyung.min.park@intel.com
Pull x86 cleanups from Ingo Molnar:
"This topic tree contains more commits than usual:
- most of it are uaccess cleanups/reorganization by Al
- there's a bunch of prototype declaration (--Wmissing-prototypes)
cleanups
- misc other cleanups all around the map"
* 'x86-cleanups-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
x86/mm/set_memory: Fix -Wmissing-prototypes warnings
x86/efi: Add a prototype for efi_arch_mem_reserve()
x86/mm: Mark setup_emu2phys_nid() static
x86/jump_label: Move 'inline' keyword placement
x86/platform/uv: Add a missing prototype for uv_bau_message_interrupt()
kill uaccess_try()
x86: unsafe_put-style macro for sigmask
x86: x32_setup_rt_frame(): consolidate uaccess areas
x86: __setup_rt_frame(): consolidate uaccess areas
x86: __setup_frame(): consolidate uaccess areas
x86: setup_sigcontext(): list user_access_{begin,end}() into callers
x86: get rid of put_user_try in __setup_rt_frame() (both 32bit and 64bit)
x86: ia32_setup_rt_frame(): consolidate uaccess areas
x86: ia32_setup_frame(): consolidate uaccess areas
x86: ia32_setup_sigcontext(): lift user_access_{begin,end}() into the callers
x86/alternatives: Mark text_poke_loc_init() static
x86/cpu: Fix a -Wmissing-prototypes warning for init_ia32_feat_ctl()
x86/mm: Drop pud_mknotpresent()
x86: Replace setup_irq() by request_irq()
x86/configs: Slightly reduce defconfigs
...
request_irq() is preferred over setup_irq(). The early boot setup_irq() invocations happen either via 'init_IRQ()' or 'time_init()', while memory allocators are ready by 'mm_init()'. setup_irq() was required in old kernels when allocators were not ready by the time early interrupts were initialized. Hence replace setup_irq() by request_irq(). [ tglx: Use a local variable and get rid of the line break. Tweak the comment a bit ] Signed-off-by: afzal mohammed <afzal.mohd.ma@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/17f85021f6877650a5b09e0212d88323e6a30fd0.1582471508.git.afzal.mohd.ma@gmail.com
Switch to the generic VDSO clock mode storage. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> (VDSO parts) Acked-by: Juergen Gross <jgross@suse.com> (Xen parts) Acked-by: Paolo Bonzini <pbonzini@redhat.com> (KVM parts) Link: https://lkml.kernel.org/r/20200207124403.152039903@linutronix.de
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
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
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