Wire up the generic support for managing task stack allocations via vmalloc,
and implement the entry code that detects whether we faulted because of a
stack overrun (or future stack overrun caused by pushing the pt_regs array)

While this adds a fair amount of tricky entry asm code, it should be
noted that it only adds a TST + branch to the svc_entry path. The code
implementing the non-trivial handling of the overflow stack is emitted
out-of-line into the .text section.

Since on ARM, we rely on do_translation_fault() to keep PMD level page
table entries that cover the vmalloc region up to date, we need to
ensure that we don't hit such a stale PMD entry when accessing the
stack. So we do a dummy read from the new stack while still running from
the old one on the context switch path, and bump the vmalloc_seq counter
when PMD level entries in the vmalloc range are modified, so that the MM
switch fetches the latest version of the entries.

Note that we need to increase the per-mode stack by 1 word, to gain some
space to stash a GPR until we know it is safe to touch the stack.
However, due to the cacheline alignment of the struct, this does not
actually increase the memory footprint of the struct stack array at all.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

The original Thumb-2 enablement patches updated the stack realignment
code in svc_entry to work around the lack of a STMIB instruction in
Thumb-2, by subtracting 4 from the frame size, inverting the sense of
the misaligment check, and changing to a STMIA instruction and a final
stack push of a 4 byte quantity that results in the stack becoming
aligned at the end of the sequence. It also pushes and pops R0 to the
stack in order to have a temp register that Thumb-2 allows in general
purpose ALU instructions, as TST using SP is not permitted.

Both are a bit problematic for vmap'ed stacks, as using the stack is
only permitted after we decide that we did not overflow the stack, or
have already switched to the overflow stack.

As for the alignment check: the current approach creates a corner case
where, if the initial SUB of SP ends up right at the start of the stack,
we will end up subtracting another 8 bytes and overflowing it.  This
means we would need to add the overflow check *after* the SUB that
deliberately misaligns the stack. However, this would require us to keep
local state (i.e., whether we performed the subtract or not) across the
overflow check, but without any GPRs or stack available.

So let's switch to an approach where we don't use the stack, and where
the alignment check of the stack pointer occurs in the usual way, as
this is guaranteed not to result in overflow. This means we will be able
to do the overflow check first.

While at it, switch to R1 so the mode stack pointer in R0 remains
accessible.
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

The load-multiple instruction that essentially performs the switch_to
operation in ARM mode, by loading all callee save registers as well the
stack pointer and the program counter, is split into 3 separate loads
for Thumb-2, with the IP register used as a temporary to capture the
value of R4 before it gets overwritten.

We can clean this up a bit, by sticking with a single LDMIA instruction,
but one that pops SP and PC into IP and LR, respectively, and by using
ordinary move register and branch instructions to get those values into
SP and PC. This also allows us to move the set_current call closer to
the assignment of SP, reducing the window where those are mutually out
of sync. This is especially relevant for CONFIG_VMAP_STACK, which is
being introduced in a subsequent patch, where we need to issue a load
that might fault from the new stack while running from the old one, to
ensure that stale PMD entries in the VMALLOC space are synced up.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

When unwinding the stack from a stack overflow, we are likely to start
from a stack push instruction, given that this is the most common way to
grow the stack for compiler emitted code. This push instruction rarely
appears anywhere else than at offset 0x0 of the function, and if it
doesn't, the compiler tends to split up the unwind annotations, given
that the stack frame layout is apparently not the same throughout the
function.

This means that, in the general case, if the frame's PC points at the
first instruction covered by a certain unwind entry, there is no way the
stack frame that the unwind entry describes could have been created yet,
and so we are still on the stack frame of the caller in that case. So
treat this as a special case, and return with the new PC taken from the
frame's LR, without applying the unwind transformations to the virtual
register set.

This permits us to unwind the call stack on stack overflow when the
overflow was caused by a stack push on function entry.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

The memset implementation carves up the code in different sections, each
covered with their own unwind info. In this case, it is done in a way
similar to how the compiler might do it, to disambiguate between parts
where the return address is in LR and the SP is unmodified, and parts
where a stack frame is live, and the unwinder needs to know the size of
the stack frame and the location of the return address within it.

Only the placement of the unwind directives is slightly odd: the stack
pushes are placed in the wrong sections, which may confuse the unwinder
when attempting to unwind with PC pointing at the stack push in
question.

So let's fix this up, by reordering the directives and instructions as
appropriate.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

The memmove routine is a bit unusual in the way it manages the stack
pointer: depending on the execution path through the function, the SP
assumes different values as different subsets of the register file are
preserved and restored again. This is problematic when it comes to EHABI
unwind info, as it is not instruction accurate, and does not allow
tracking the SP value as it changes.

Commit 207a6cb0 ("ARM: 8224/1: Add unwinding support for memmove
function") addressed this by carving up the function in different chunks
as far as the unwinder is concerned, and keeping a set of unwind
directives for each of them, each corresponding with the state of the
stack pointer during execution of the chunk in question. This not only
duplicates unwind info unnecessarily, but it also complicates unwinding
the stack upon overflow.

Instead, let's do what the compiler does when the SP is updated halfway
through a function, which is to use a frame pointer and emit the
appropriate unwind directives to communicate this to the unwinder.

Note that Thumb-2 uses R7 for this, while ARM uses R11 aka FP. So let's
avoid touching R7 in the body of the function, so that Thumb-2 can use
it as the frame pointer. R11 was not modified in the first place.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

The memcpy template is a bit unusual in the way it manages the stack
pointer: depending on the execution path through the function, the SP
assumes different values as different subsets of the register file are
preserved and restored again. This is problematic when it comes to EHABI
unwind info, as it is not instruction accurate, and does not allow
tracking the SP value as it changes.

Commit 279f487e ("ARM: 8225/1: Add unwinding support for memory
copy functions") addressed this by carving up the function in different
chunks as far as the unwinder is concerned, and keeping a set of unwind
directives for each of them, each corresponding with the state of the
stack pointer during execution of the chunk in question. This not only
duplicates unwind info unnecessarily, but it also complicates unwinding
the stack upon overflow.

Instead, let's do what the compiler does when the SP is updated halfway
through a function, which is to use a frame pointer and emit the
appropriate unwind directives to communicate this to the unwinder.

Note that Thumb-2 uses R7 for this, while ARM uses R11 aka FP. So let's
avoid touching R7 in the body of the template, so that Thumb-2 can use
it as the frame pointer. R11 was not modified in the first place.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

Now that we have enabled IRQ stacks, any softIRQs that are handled over
the back of a hard IRQ will run from the IRQ stack as well. However, any
synchronous softirq processing that happens when re-enabling softIRQs
from task context will still execute on that task's stack.

Since any call to local_bh_enable() at any level in the task's call
stack may trigger a softIRQ processing run, which could potentially
cause a task stack overflow if the combined stack footprints exceed the
stack's size, let's run these synchronous invocations of do_softirq() on
the IRQ stack as well.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

Restructure the code and add the unwind annotations so that both the
frame pointer unwinder as well as the EHABI unwind info based unwinder
will be able to follow the call stack through call_with_stack().

Since GCC and Clang use different formats for the stack frame, two
methods are implemented: a GCC version that pushes fp, sp, lr and pc for
compatibility with the frame pointer unwinder, and a second version that
works with Clang, as well as with the EHABI unwinder both in ARM and
Thumb2 modes.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

Now that we no longer rely on the stack pointer to access the current
task struct or thread info, we can implement support for IRQ stacks
cleanly as well.

Define a per-CPU IRQ stack and switch to this stack when taking an IRQ,
provided that we were not already using that stack in the interrupted
context. This is never the case for IRQs taken from user space, but ones
taken while running in the kernel could fire while one taken from user
space has not completed yet.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

The Clang backtrace code dereferences the link register value pulled
from the stack to decide whether the caller was a branch-and-link
instruction, in order to subsequently decode the offset to find the
start of the calling function. Unlike other loads in this routine, this
one is not protected by a fixup, and may therefore cause a crash if the
address in question is bogus.

So let's fix this, by treating the fault as a failure to decode the 'bl'
instruction. To avoid a label renum, reuse a fixup label that guards an
instruction that cannot fault to begin with.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

The existing code that dumps the contents of the pt_regs structure
passed to __entry routines does so while unwinding the callee frame, and
dereferences the stack pointer as a struct pt_regs*. This will no longer
work when we enable support for IRQ or overflow stacks, because the
struct pt_regs may live on the task stack, while we are executing from
another stack.

The unwinder has access to this information, but only while unwinding
the calling frame. So let's combine the exception stack dumping code
with the handling of the calling frame as well. By printing it before
dumping the caller/callee addresses, the output order is preserved.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

The unwind info based stack unwinder will make its own call to
dump_mem() to dump the exception stack, so give it external linkage.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

Implement support in the unwinder for dealing with multiple stacks.
This will be needed once we add support for IRQ stacks, or for the
overflow stack used by the vmap'ed stacks code.

This involves tracking the unwind opcodes that either update the virtual
stack pointer from another virtual register, or perform an explicit
subtract on the virtual stack pointer, and updating the low and high
bounds that we use to sanitize the stack pointer accordingly.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

Add a bl_r macro that abstract the difference between the ways indirect
calls are performed on older and newer ARM architecture revisions.

The main difference is to prefer blx instructions over explicit LR
assignments when possible, as these tend to confuse the prediction logic
in out-of-order cores when speculating across a function return.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

This code appears to be no longer used so let's get rid of it.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

Currently, we implement the per-task stack protector for ARM using a GCC
plugin, due to lack of native compiler support. However, work is
underway to get this implemented in the compiler, which means we will be
able to deprecate the GCC plugin at some point.

In the meantime, we will need to support both, where the native compiler
implementation is obviously preferred. So let's wire this up in Kconfig
and the Makefile.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M

Enabling the stack protector in the decompressor is of dubious value,
given that it uses a fixed value for the canary, cannot print any output
unless CONFIG_DEBUG_LL is enabled (which relies on board specific build
time settings), and is already disabled for a good chunk of the code
(libfdt).

So let's just disable it in the decompressor. This will make it easier
in the future to manage the command line options that would need to be
removed again in this context for the TLS register based stack
protector.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Add Kconfig support for -Wimplicit-fallthrough for both GCC and Clang.

The compiler option is under configuration CC_IMPLICIT_FALLTHROUGH,
which is enabled by default.

Special thanks to Nathan Chancellor who fixed the Clang bug[1][2]. This
bugfix only appears in Clang 14.0.0, so older versions still contain
the bug and -Wimplicit-fallthrough won't be enabled for them, for now.

This concludes a long journey and now we are finally getting rid
of the unintentional fallthrough bug-class in the kernel, entirely. :)

Link: https://github.com/llvm/llvm-project/commit/9ed4a94d6451046a51ef393cd62f00710820a7e8 [1]
Link: https://bugs.llvm.org/show_bug.cgi?id=51094 [2]
Link: https://github.com/KSPP/linux/issues/115
Link: https://github.com/ClangBuiltLinux/linux/issues/236Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Co-developed-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull xfs cleanups from Darrick Wong:
 "The most 'exciting' aspect of this branch is that the xfsprogs
  maintainer and I have worked through the last of the code
  discrepancies between kernel and userspace libxfs such that there are
  no code differences between the two except for #includes.

  IOWs, diff suffices to demonstrate that the userspace tools behave the
  same as the kernel, and kernel-only bits are clearly marked in the
  /kernel/ source code instead of just the userspace source.

  Summary:

   - Clean up open-coded swap() calls.

   - A little bit of #ifdef golf to complete the reunification of the
     kernel and userspace libxfs source code"

* tag 'xfs-5.16-merge-5' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: sync xfs_btree_split macros with userspace libxfs
  xfs: #ifdef out perag code for userspace
  xfs: use swap() to make dabtree code cleaner

Pull more parisc fixes from Helge Deller:
 "Fix a build error in stracktrace.c, fix resolving of addresses to
  function names in backtraces, fix single-stepping in assembly code and
  flush userspace pte's when using set_pte_at()"

* tag 'for-5.16/parisc-3' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc/entry: fix trace test in syscall exit path
  parisc: Flush kernel data mapping in set_pte_at() when installing pte for user page
  parisc: Fix implicit declaration of function '__kernel_text_address'
  parisc: Fix backtrace to always include init funtion names

Pull arch/sh updates from Rich Felker.

* tag 'sh-for-5.16' of git://git.libc.org/linux-sh:
  sh: pgtable-3level: Fix cast to pointer from integer of different size
  sh: fix READ/WRITE redefinition warnings
  sh: define __BIG_ENDIAN for math-emu
  sh: math-emu: drop unused functions
  sh: fix kconfig unmet dependency warning for FRAME_POINTER
  sh: Cleanup about SPARSE_IRQ
  sh: kdump: add some attribute to function
  maple: fix wrong return value of maple_bus_init().
  sh: boot: avoid unneeded rebuilds under arch/sh/boot/compressed/
  sh: boot: add intermediate vmlinux.bin* to targets instead of extra-y
  sh: boards: Fix the cacography in irq.c
  sh: check return code of request_irq
  sh: fix trivial misannotations

Pull ARM fixes from Russell King:

 - Fix early_iounmap

 - Drop cc-option fallbacks for architecture selection

* tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm:
  ARM: 9156/1: drop cc-option fallbacks for architecture selection
  ARM: 9155/1: fix early early_iounmap()

Pull devicetree fixes from Rob Herring:

 - Two fixes due to DT node name changes on Arm, Ltd. boards

 - Treewide rename of Ingenic CGU headers

 - Update ST email addresses

 - Remove Netlogic DT bindings

 - Dropping few more cases of redundant 'maxItems' in schemas

 - Convert toshiba,tc358767 bridge binding to schema

* tag 'devicetree-fixes-for-5.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux:
  dt-bindings: watchdog: sunxi: fix error in schema
  bindings: media: venus: Drop redundant maxItems for power-domain-names
  dt-bindings: Remove Netlogic bindings
  clk: versatile: clk-icst: Ensure clock names are unique
  of: Support using 'mask' in making device bus id
  dt-bindings: treewide: Update @st.com email address to @foss.st.com
  dt-bindings: media: Update maintainers for st,stm32-hwspinlock.yaml
  dt-bindings: media: Update maintainers for st,stm32-cec.yaml
  dt-bindings: mfd: timers: Update maintainers for st,stm32-timers
  dt-bindings: timer: Update maintainers for st,stm32-timer
  dt-bindings: i2c: imx: hardware do not restrict clock-frequency to only 100 and 400 kHz
  dt-bindings: display: bridge: Convert toshiba,tc358767.txt to yaml
  dt-bindings: Rename Ingenic CGU headers to ingenic,*.h

Pull timer fix from Thomas Gleixner:
 "A single fix for POSIX CPU timers to address a problem where POSIX CPU
  timer delivery stops working for a new child task because
  copy_process() copies state information which is only valid for the
  parent task"

* tag 'timers-urgent-2021-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  posix-cpu-timers: Clear task::posix_cputimers_work in copy_process()

Pull irq fixes from Thomas Gleixner:
 "A set of fixes for the interrupt subsystem

  Core code:

   - A regression fix for the Open Firmware interrupt mapping code where
     a interrupt controller property in a node caused a map property in
     the same node to be ignored.

  Interrupt chip drivers:

   - Workaround a limitation in SiFive PLIC interrupt chip which
     silently ignores an EOI when the interrupt line is masked.

   - Provide the missing mask/unmask implementation for the CSKY MP
     interrupt controller.

  PCI/MSI:

   - Prevent a use after free when PCI/MSI interrupts are released by
     destroying the sysfs entries before freeing the memory which is
     accessed in the sysfs show() function.

   - Implement a mask quirk for the Nvidia ION AHCI chip which does not
     advertise masking capability despite implementing it. Even worse
     the chip comes out of reset with all MSI entries masked, which due
     to the missing masking capability never get unmasked.

   - Move the check which prevents accessing the MSI[X] masking for XEN
     back into the low level accessors. The recent consolidation missed
     that these accessors can be invoked from places which do not have
     that check which broke XEN. Move them back to he original place
     instead of sprinkling tons of these checks all over the code"

* tag 'irq-urgent-2021-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  of/irq: Don't ignore interrupt-controller when interrupt-map failed
  irqchip/sifive-plic: Fixup EOI failed when masked
  irqchip/csky-mpintc: Fixup mask/unmask implementation
  PCI/MSI: Destroy sysfs before freeing entries
  PCI: Add MSI masking quirk for Nvidia ION AHCI
  PCI/MSI: Deal with devices lying about their MSI mask capability
  PCI/MSI: Move non-mask check back into low level accessors

Pull x86 static call update from Thomas Gleixner:
 "A single fix for static calls to make the trampoline patching more
  robust by placing explicit signature bytes after the call trampoline
  to prevent patching random other jumps like the CFI jump table
  entries"

* tag 'locking-urgent-2021-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  static_call,x86: Robustify trampoline patching

Pull scheduler fixes from Borislav Petkov:

 - Avoid touching ~100 config files in order to be able to select the
   preemption model

 - clear cluster CPU masks too, on the CPU unplug path

 - prevent use-after-free in cfs

 - Prevent a race condition when updating CPU cache domains

 - Factor out common shared part of smp_prepare_cpus() into a common
   helper which can be called by both baremetal and Xen, in order to fix
   a booting of Xen PV guests

* tag 'sched_urgent_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  preempt: Restore preemption model selection configs
  arch_topology: Fix missing clear cluster_cpumask in remove_cpu_topology()
  sched/fair: Prevent dead task groups from regaining cfs_rq's
  sched/core: Mitigate race cpus_share_cache()/update_top_cache_domain()
  x86/smp: Factor out parts of native_smp_prepare_cpus()

Pull perf fixes from Borislav Petkov:

 - Prevent unintentional page sharing by checking whether a page
   reference to a PMU samples page has been acquired properly before
   that

 - Make sure the LBR_SELECT MSR is saved/restored too

 - Reset the LBR_SELECT MSR when resetting the LBR PMU to clear any
   residual data left

* tag 'perf_urgent_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/core: Avoid put_page() when GUP fails
  perf/x86/vlbr: Add c->flags to vlbr event constraints
  perf/x86/lbr: Reset LBR_SELECT during vlbr reset

Pull x86 fixes from Borislav Petkov:

 - Add the model number of a new, Raptor Lake CPU, to intel-family.h

 - Do not log spurious corrected MCEs on SKL too, due to an erratum

 - Clarify the path of paravirt ops patches upstream

 - Add an optimization to avoid writing out AMX components to sigframes
   when former are in init state

* tag 'x86_urgent_for_v5.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/cpu: Add Raptor Lake to Intel family
  x86/mce: Add errata workaround for Skylake SKX37
  MAINTAINERS: Add some information to PARAVIRT_OPS entry
  x86/fpu: Optimize out sigframe xfeatures when in init state

Merge tag 'perf-tools-for-v5.16-2021-11-13' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux

Pull more perf tools updates from Arnaldo Carvalho de Melo:
 "Hardware tracing:

   - ARM:
      * Print the size of the buffer size consistently in hexadecimal in
        ARM Coresight.
      * Add Coresight snapshot mode support.
      * Update --switch-events docs in 'perf record'.
      * Support hardware-based PID tracing.
      * Track task context switch for cpu-mode events.

   - Vendor events:
      * Add metric events JSON file for power10 platform

  perf test:

   - Get 'perf test' unit tests closer to kunit.

   - Topology tests improvements.

   - Remove bashisms from some tests.

  perf bench:

   - Fix memory leak of perf_cpu_map__new() in the futex benchmarks.

  libbpf:

   - Add some more weak libbpf functions o allow building with the
     libbpf versions, old ones, present in distros.

  libbeauty:

   - Translate [gs]setsockopt 'level' argument integer values to
     strings.

  tools headers UAPI:

   - Sync futex_waitv, arch prctl, sound, i195_drm and msr-index files
     with the kernel sources.

  Documentation:

   - Add documentation to 'struct symbol'.

   - Synchronize the definition of enum perf_hw_id with code in
     tools/perf/design.txt"

* tag 'perf-tools-for-v5.16-2021-11-13' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux: (67 commits)
  perf tests: Remove bash constructs from stat_all_pmu.sh
  perf tests: Remove bash construct from record+zstd_comp_decomp.sh
  perf test: Remove bash construct from stat_bpf_counters.sh test
  perf bench futex: Fix memory leak of perf_cpu_map__new()
  tools arch x86: Sync the msr-index.h copy with the kernel sources
  tools headers UAPI: Sync drm/i915_drm.h with the kernel sources
  tools headers UAPI: Sync sound/asound.h with the kernel sources
  tools headers UAPI: Sync linux/prctl.h with the kernel sources
  tools headers UAPI: Sync arch prctl headers with the kernel sources
  perf tools: Add more weak libbpf functions
  perf bpf: Avoid memory leak from perf_env__insert_btf()
  perf symbols: Factor out annotation init/exit
  perf symbols: Bit pack to save a byte
  perf symbols: Add documentation to 'struct symbol'
  tools headers UAPI: Sync files changed by new futex_waitv syscall
  perf test bpf: Use ARRAY_CHECK() instead of ad-hoc equivalent, addressing array_size.cocci warning
  perf arm-spe: Support hardware-based PID tracing
  perf arm-spe: Save context ID in record
  perf arm-spe: Update --switch-events docs in 'perf record'
  perf arm-spe: Track task context switch for cpu-mode events
  ...

Merge tag 'irqchip-fixes-5.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/urgent

Pull irqchip fixes from Marc Zyngier:

  - Address an issue with the SiFive PLIC being unable to EOI
    a masked interrupt

  - Move the disable/enable methods in the CSky mpintc to
    mask/unmask

  - Fix a regression in the OF irq code where an interrupt-controller
    property in the same node as an interrupt-map property would get
    ignored

Link: https://lore.kernel.org/all/20211112173459.4015233-1-maz@kernel.org

Pull zstd update from Nick Terrell:
 "Update to zstd-1.4.10.

  Add myself as the maintainer of zstd and update the zstd version in
  the kernel, which is now 4 years out of date, to a much more recent
  zstd release. This includes bug fixes, much more extensive fuzzing,
  and performance improvements. And generates the kernel zstd
  automatically from upstream zstd, so it is easier to keep the zstd
  verison up to date, and we don't fall so far out of date again.

  This includes 5 commits that update the zstd library version:

   - Adds a new kernel-style wrapper around zstd.

     This wrapper API is functionally equivalent to the subset of the
     current zstd API that is currently used. The wrapper API changes to
     be kernel style so that the symbols don't collide with zstd's
     symbols. The update to zstd-1.4.10 maintains the same API and
     preserves the semantics, so that none of the callers need to be
     updated. All callers are updated in the commit, because there are
     zero functional changes.

   - Adds an indirection for `lib/decompress_unzstd.c` so it doesn't
     depend on the layout of `lib/zstd/` to include every source file.
     This allows the next patch to be automatically generated.

   - Imports the zstd-1.4.10 source code. This commit is automatically
     generated from upstream zstd (https://github.com/facebook/zstd).

   - Adds me (terrelln@fb.com) as the maintainer of `lib/zstd`.

   - Fixes a newly added build warning for clang.

  The discussion around this patchset has been pretty long, so I've
  included a FAQ-style summary of the history of the patchset, and why
  we are taking this approach.

  Why do we need to update?
  -------------------------

  The zstd version in the kernel is based off of zstd-1.3.1, which is
  was released August 20, 2017. Since then zstd has seen many bug fixes
  and performance improvements. And, importantly, upstream zstd is
  continuously fuzzed by OSS-Fuzz, and bug fixes aren't backported to
  older versions. So the only way to sanely get these fixes is to keep
  up to date with upstream zstd.

  There are no known security issues that affect the kernel, but we need
  to be able to update in case there are. And while there are no known
  security issues, there are relevant bug fixes. For example the problem
  with large kernel decompression has been fixed upstream for over 2
  years [1]

  Additionally the performance improvements for kernel use cases are
  significant. Measured for x86_64 on my Intel i9-9900k @ 3.6 GHz:

   - BtrFS zstd compression at levels 1 and 3 is 5% faster

   - BtrFS zstd decompression+read is 15% faster

   - SquashFS zstd decompression+read is 15% faster

   - F2FS zstd compression+write at level 3 is 8% faster

   - F2FS zstd decompression+read is 20% faster

   - ZRAM decompression+read is 30% faster

   - Kernel zstd decompression is 35% faster

   - Initramfs zstd decompression+build is 5% faster

  On top of this, there are significant performance improvements coming
  down the line in the next zstd release, and the new automated update
  patch generation will allow us to pull them easily.

  How is the update patch generated?
  ----------------------------------

  The first two patches are preparation for updating the zstd version.
  Then the 3rd patch in the series imports upstream zstd into the
  kernel. This patch is automatically generated from upstream. A script
  makes the necessary changes and imports it into the kernel. The
  changes are:

   - Replace all libc dependencies with kernel replacements and rewrite
     includes.

   - Remove unncessary portability macros like: #if defined(_MSC_VER).

   - Use the kernel xxhash instead of bundling it.

  This automation gets tested every commit by upstream's continuous
  integration. When we cut a new zstd release, we will submit a patch to
  the kernel to update the zstd version in the kernel.

  The automated process makes it easy to keep the kernel version of zstd
  up to date. The current zstd in the kernel shares the guts of the
  code, but has a lot of API and minor changes to work in the kernel.
  This is because at the time upstream zstd was not ready to be used in
  the kernel envrionment as-is. But, since then upstream zstd has
  evolved to support being used in the kernel as-is.

  Why are we updating in one big patch?
  -------------------------------------

  The 3rd patch in the series is very large. This is because it is
  restructuring the code, so it both deletes the existing zstd, and
  re-adds the new structure. Future updates will be directly
  proportional to the changes in upstream zstd since the last import.
  They will admittidly be large, as zstd is an actively developed
  project, and has hundreds of commits between every release. However,
  there is no other great alternative.

  One option ruled out is to replay every upstream zstd commit. This is
  not feasible for several reasons:

   - There are over 3500 upstream commits since the zstd version in the
     kernel.

   - The automation to automatically generate the kernel update was only
     added recently, so older commits cannot easily be imported.

   - Not every upstream zstd commit builds.

   - Only zstd releases are "supported", and individual commits may have
     bugs that were fixed before a release.

  Another option to reduce the patch size would be to first reorganize
  to the new file structure, and then apply the patch. However, the
  current kernel zstd is formatted with clang-format to be more
  "kernel-like". But, the new method imports zstd as-is, without
  additional formatting, to allow for closer correlation with upstream,
  and easier debugging. So the patch wouldn't be any smaller.

  It also doesn't make sense to import upstream zstd commit by commit
  going forward. Upstream zstd doesn't support production use cases
  running of the development branch. We have a lot of post-commit
  fuzzing that catches many bugs, so indiviudal commits may be buggy,
  but fixed before a release. So going forward, I intend to import every
  (important) zstd release into the Kernel.

  So, while it isn't ideal, updating in one big patch is the only patch
  I see forward.

  Who is responsible for this code?
  ---------------------------------

  I am. This patchset adds me as the maintainer for zstd. Previously,
  there was no tree for zstd patches. Because of that, there were
  several patches that either got ignored, or took a long time to merge,
  since it wasn't clear which tree should pick them up. I'm officially
  stepping up as maintainer, and setting up my tree as the path through
  which zstd patches get merged. I'll make sure that patches to the
  kernel zstd get ported upstream, so they aren't erased when the next
  version update happens.

  How is this code tested?
  ------------------------

  I tested every caller of zstd on x86_64 (BtrFS, ZRAM, SquashFS, F2FS,
  Kernel, InitRAMFS). I also tested Kernel & InitRAMFS on i386 and
  aarch64. I checked both performance and correctness.

  Also, thanks to many people in the community who have tested these
  patches locally.

  Lastly, this code will bake in linux-next before being merged into
  v5.16.

  Why update to zstd-1.4.10 when zstd-1.5.0 has been released?
  ------------------------------------------------------------

  This patchset has been outstanding since 2020, and zstd-1.4.10 was the
  latest release when it was created. Since the update patch is
  automatically generated from upstream, I could generate it from
  zstd-1.5.0.

  However, there were some large stack usage regressions in zstd-1.5.0,
  and are only fixed in the latest development branch. And the latest
  development branch contains some new code that needs to bake in the
  fuzzer before I would feel comfortable releasing to the kernel.

  Once this patchset has been merged, and we've released zstd-1.5.1, we
  can update the kernel to zstd-1.5.1, and exercise the update process.

  You may notice that zstd-1.4.10 doesn't exist upstream. This release
  is an artifical release based off of zstd-1.4.9, with some fixes for
  the kernel backported from the development branch. I will tag the
  zstd-1.4.10 release after this patchset is merged, so the Linux Kernel
  is running a known version of zstd that can be debugged upstream.

  Why was a wrapper API added?
  ----------------------------

  The first versions of this patchset migrated the kernel to the
  upstream zstd API. It first added a shim API that supported the new
  upstream API with the old code, then updated callers to use the new
  shim API, then transitioned to the new code and deleted the shim API.
  However, Cristoph Hellwig suggested that we transition to a kernel
  style API, and hide zstd's upstream API behind that. This is because
  zstd's upstream API is supports many other use cases, and does not
  follow the kernel style guide, while the kernel API is focused on the
  kernel's use cases, and follows the kernel style guide.

  Where is the previous discussion?
  ---------------------------------

  Links for the discussions of the previous versions of the patch set
  below. The largest changes in the design of the patchset are driven by
  the discussions in v11, v5, and v1. Sorry for the mix of links, I
  couldn't find most of the the threads on lkml.org"

Link: https://lkml.org/lkml/2020/9/29/27 [1]
Link: https://www.spinics.net/lists/linux-crypto/msg58189.html [v12]
Link: https://lore.kernel.org/linux-btrfs/20210430013157.747152-1-nickrterrell@gmail.com/ [v11]
Link: https://lore.kernel.org/lkml/20210426234621.870684-2-nickrterrell@gmail.com/ [v10]
Link: https://lore.kernel.org/linux-btrfs/20210330225112.496213-1-nickrterrell@gmail.com/ [v9]
Link: https://lore.kernel.org/linux-f2fs-devel/20210326191859.1542272-1-nickrterrell@gmail.com/ [v8]
Link: https://lkml.org/lkml/2020/12/3/1195 [v7]
Link: https://lkml.org/lkml/2020/12/2/1245 [v6]
Link: https://lore.kernel.org/linux-btrfs/20200916034307.2092020-1-nickrterrell@gmail.com/ [v5]
Link: https://www.spinics.net/lists/linux-btrfs/msg105783.html [v4]
Link: https://lkml.org/lkml/2020/9/23/1074 [v3]
Link: https://www.spinics.net/lists/linux-btrfs/msg105505.html [v2]
Link: https://lore.kernel.org/linux-btrfs/20200916034307.2092020-1-nickrterrell@gmail.com/ [v1]
Signed-off-by: Nick Terrell <terrelln@fb.com>
Tested By: Paul Jones <paul@pauljones.id.au>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang v13.0.0 on x86-64
Tested-by: Jean-Denis Girard <jd.girard@sysnux.pf>

* tag 'zstd-for-linus-v5.16' of git://github.com/terrelln/linux:
  lib: zstd: Add cast to silence clang's -Wbitwise-instead-of-logical
  MAINTAINERS: Add maintainer entry for zstd
  lib: zstd: Upgrade to latest upstream zstd version 1.4.10
  lib: zstd: Add decompress_sources.h for decompress_unzstd
  lib: zstd: Add kernel-specific API

Pull virtio-mem update from David Hildenbrand:
 "Support the VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE feature in virtio-mem,
  now that "accidential" access to logically unplugged memory inside
  added Linux memory blocks is no longer possible, because we:

   - Removed /dev/kmem in commit bbcd53c9 ("drivers/char: remove
     /dev/kmem for good")

   - Disallowed access to virtio-mem device memory via /dev/mem in
     commit 2128f4e2 ("virtio-mem: disallow mapping virtio-mem memory
     via /dev/mem")

   - Sanitized access to virtio-mem device memory via /proc/kcore in
     commit 0daa322b ("fs/proc/kcore: don't read offline sections,
     logically offline pages and hwpoisoned pages")

   - Sanitized access to virtio-mem device memory via /proc/vmcore in
     commit ce281462 ("virtio-mem: kdump mode to sanitize
     /proc/vmcore access")

  The new VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE feature that will be
  required by some hypervisors implementing virtio-mem in the near
  future, so let's support it now that we safely can"

* tag 'virtio-mem-for-5.16' of git://github.com/davidhildenbrand/linux:
  virtio-mem: support VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE

The tests were passing but without testing and were printing the
following:

  $ ./perf test -v 90
  90: perf all PMU test                                               :
  --- start ---
  test child forked, pid 51650
  Testing cpu/branch-instructions/
  ./tests/shell/stat_all_pmu.sh: 10: [:
   Performance counter stats for 'true':

             137,307      cpu/branch-instructions/

         0.001686672 seconds time elapsed

         0.001376000 seconds user
         0.000000000 seconds sys: unexpected operator

Changing the regexes to a grep works in sh and prints this:

  $ ./perf test -v 90
  90: perf all PMU test                                               :
  --- start ---
  test child forked, pid 60186
  [...]
  Testing tlb_flush.stlb_any
  test child finished with 0
  ---- end ----
  perf all PMU test: Ok
Signed-off-by: James Clark <james.clark@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org
Link: https://lore.kernel.org/r/20211028134828.65774-4-james.clark@arm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Commit 463538a3 ("perf tests: Fix test 68 zstd compression for
s390") inadvertently removed the -g flag from all platforms rather than
just s390, because the [[ ]] construct fails in sh. Changing to single
brackets restores testing of call graphs and removes the following error
from the output:

  $ ./perf test -v 85
  85: Zstd perf.data compression/decompression                        :
  --- start ---
  test child forked, pid 50643
  Collecting compressed record file:
  ./tests/shell/record+zstd_comp_decomp.sh: 15: [[: not found

Fixes: 463538a3 ("perf tests: Fix test 68 zstd compression for s390")
Signed-off-by: James Clark <james.clark@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org
Link: https://lore.kernel.org/r/20211028134828.65774-3-james.clark@arm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Currently the test skips with an error because == only works in bash:

  $ ./perf test 91 -v
  Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc
  91: perf stat --bpf-counters test                                   :
  --- start ---
  test child forked, pid 44586
  ./tests/shell/stat_bpf_counters.sh: 26: [: -v: unexpected operator
  test child finished with -2
  ---- end ----
  perf stat --bpf-counters test: Skip

Changing == to = does the same thing, but doesn't result in an error:

  ./perf test 91 -v
  Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc
  91: perf stat --bpf-counters test                                   :
  --- start ---
  test child forked, pid 45833
  Skipping: --bpf-counters not supported
    Error: unknown option `bpf-counters'
  [...]
  test child finished with -2
  ---- end ----
  perf stat --bpf-counters test: Skip
Signed-off-by: James Clark <james.clark@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org
Link: https://lore.kernel.org/r/20211028134828.65774-2-james.clark@arm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

ASan reports memory leaks while running:

  $ sudo ./perf bench futex all

The leaks are caused by perf_cpu_map__new not being freed.
This patch adds the missing perf_cpu_map__put since it calls
cpu_map_delete implicitly.

Fixes: 9c3516d1 ("libperf: Add perf_cpu_map__new()/perf_cpu_map__read() functions")
Signed-off-by: Sohaib Mohamed <sohaib.amhmd@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: André Almeida <andrealmeid@collabora.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sohaib Mohamed <sohaib.amhmd@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lore.kernel.org/lkml/20211112201134.77892-1-sohaib.amhmd@gmail.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

To pick up the changes in:

  dae1bd58 ("x86/msr-index: Add MSRs for XFD")

Addressing these tools/perf build warnings:

    diff -u tools/arch/x86/include/asm/msr-index.h arch/x86/include/asm/msr-index.h
    Warning: Kernel ABI header at 'tools/arch/x86/include/asm/msr-index.h' differs from latest version at 'arch/x86/include/asm/msr-index.h'

That makes the beautification scripts to pick some new entries:

  $ diff -u tools/arch/x86/include/asm/msr-index.h arch/x86/include/asm/msr-index.h
  --- tools/arch/x86/include/asm/msr-index.h	2021-07-15 16:17:01.819817827 -0300
  +++ arch/x86/include/asm/msr-index.h	2021-11-06 15:49:33.738517311 -0300
  @@ -625,6 +625,8 @@

   #define MSR_IA32_BNDCFGS_RSVD		0x00000ffc

  +#define MSR_IA32_XFD			0x000001c4
  +#define MSR_IA32_XFD_ERR		0x000001c5
   #define MSR_IA32_XSS			0x00000da0

   #define MSR_IA32_APICBASE		0x0000001b
  $ tools/perf/trace/beauty/tracepoints/x86_msr.sh > /tmp/before
  $ cp arch/x86/include/asm/msr-index.h tools/arch/x86/include/asm/msr-index.h
  $ tools/perf/trace/beauty/tracepoints/x86_msr.sh > /tmp/after
  $ diff -u /tmp/before /tmp/after
  --- /tmp/before	2021-11-13 11:10:39.964201505 -0300
  +++ /tmp/after	2021-11-13 11:10:47.902410873 -0300
  @@ -93,6 +93,8 @@
   	[0x000001b0] = "IA32_ENERGY_PERF_BIAS",
   	[0x000001b1] = "IA32_PACKAGE_THERM_STATUS",
   	[0x000001b2] = "IA32_PACKAGE_THERM_INTERRUPT",
  +	[0x000001c4] = "IA32_XFD",
  +	[0x000001c5] = "IA32_XFD_ERR",
   	[0x000001c8] = "LBR_SELECT",
   	[0x000001c9] = "LBR_TOS",
   	[0x000001d9] = "IA32_DEBUGCTLMSR",
  $

And this gets rebuilt:

  CC       /tmp/build/perf/trace/beauty/tracepoints/x86_msr.o
  INSTALL  trace_plugins
  LD       /tmp/build/perf/trace/beauty/tracepoints/perf-in.o
  LD       /tmp/build/perf/trace/beauty/perf-in.o
  LD       /tmp/build/perf/perf-in.o
  LINK     /tmp/build/perf/perf

Now one can trace systemwide asking to see backtraces to where those
MSRs are being read/written with:

  # perf trace -e msr:*_msr/max-stack=32/ --filter="msr==IA32_XFD || msr==IA32_XFD_ERR"
  ^C#
  #

If we use -v (verbose mode) we can see what it does behind the scenes:

  # perf trace -v -e msr:*_msr/max-stack=32/ --filter="msr==IA32_XFD || msr==IA32_XFD_ERR"
  <SNIP>
  New filter for msr:read_msr: (msr==0x1c4 || msr==0x1c5) && (common_pid != 44489516 && common_pid != 8781)
  New filter for msr:write_msr: (msr==0x1c4 || msr==0x1c5) && (common_pid != 44489516 && common_pid != 8781)
  <SNIP>
  ^C#

Example with a frequent msr:

  # perf trace -v -e msr:*_msr/max-stack=32/ --filter="msr==IA32_SPEC_CTRL" --max-events 2
  Using CPUID AuthenticAMD-25-21-0
  0x48
  New filter for msr:read_msr: (msr==0x48) && (common_pid != 3738351 && common_pid != 3564)
  0x48
  New filter for msr:write_msr: (msr==0x48) && (common_pid != 3738351 && common_pid != 3564)
  mmap size 528384B
  Looking at the vmlinux_path (8 entries long)
  symsrc__init: build id mismatch for vmlinux.
  Using /proc/kcore for kernel data
  Using /proc/kallsyms for symbols
       0.000 pipewire/2479 msr:write_msr(msr: IA32_SPEC_CTRL, val: 6)
                                         do_trace_write_msr ([kernel.kallsyms])
                                         do_trace_write_msr ([kernel.kallsyms])
                                         __switch_to_xtra ([kernel.kallsyms])
                                         __switch_to ([kernel.kallsyms])
                                         __schedule ([kernel.kallsyms])
                                         schedule ([kernel.kallsyms])
                                         schedule_hrtimeout_range_clock ([kernel.kallsyms])
                                         do_epoll_wait ([kernel.kallsyms])
                                         __x64_sys_epoll_wait ([kernel.kallsyms])
                                         do_syscall_64 ([kernel.kallsyms])
                                         entry_SYSCALL_64_after_hwframe ([kernel.kallsyms])
                                         epoll_wait (/usr/lib64/libc-2.33.so)
                                         [0x76c4] (/usr/lib64/spa-0.2/support/libspa-support.so)
                                         [0x4cf0] (/usr/lib64/spa-0.2/support/libspa-support.so)
       0.027 :0/0 msr:write_msr(msr: IA32_SPEC_CTRL, val: 2)
                                         do_trace_write_msr ([kernel.kallsyms])
                                         do_trace_write_msr ([kernel.kallsyms])
                                         __switch_to_xtra ([kernel.kallsyms])
                                         __switch_to ([kernel.kallsyms])
                                         __schedule ([kernel.kallsyms])
                                         schedule_idle ([kernel.kallsyms])
                                         do_idle ([kernel.kallsyms])
                                         cpu_startup_entry ([kernel.kallsyms])
                                         start_kernel ([kernel.kallsyms])
                                         secondary_startup_64_no_verify ([kernel.kallsyms])
  #

Cc: Borislav Petkov <bp@suse.de>
Cc: Chang S. Bae <chang.seok.bae@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/YY%2FJdb6on7swsn+C@kernel.org/Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>