linux-toradex.git/arch/arm/kernel/machine_kexec.c, branch v6.12

arch, crash: move arch_crash_save_vmcoreinfo() out to file vmcore_info.c

2024-02-24T01:48:25+00:00

Nathan reported below building error:

=====
$ curl -LSso .config https://git.alpinelinux.org/aports/plain/community/linux-edge/config-edge.armv7
$ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- olddefconfig all
..
arm-linux-gnueabi-ld: arch/arm/kernel/machine_kexec.o: in function `arch_crash_save_vmcoreinfo':
machine_kexec.c:(.text+0x488): undefined reference to `vmcoreinfo_append_str'
====

On architecutres, like arm, s390, ppc, sh, function
arch_crash_save_vmcoreinfo() is located in machine_kexec.c and it can
only be compiled in when CONFIG_KEXEC_CORE=y.

That's not right because arch_crash_save_vmcoreinfo() is used to export
arch specific vmcoreinfo. CONFIG_VMCORE_INFO is supposed to control its
compiling in. However, CONFIG_VMVCORE_INFO could be independent of
CONFIG_KEXEC_CORE, e.g CONFIG_PROC_KCORE=y will select CONFIG_VMVCORE_INFO.
Or CONFIG_KEXEC/CONFIG_KEXEC_FILE is set while CONFIG_CRASH_DUMP is
not set, it will report linking error.

So, on arm, s390, ppc and sh, move arch_crash_save_vmcoreinfo out to
a new file vmcore_info.c. Let CONFIG_VMCORE_INFO decide if compiling in
arch_crash_save_vmcoreinfo().

[akpm@linux-foundation.org: remove stray newlines at eof]
Link: https://lkml.kernel.org/r/20240129135033.157195-3-bhe@redhat.com
Signed-off-by: Baoquan He 
Reported-by: Nathan Chancellor 
Closes: https://lore.kernel.org/all/20240126045551.GA126645@dev-arch.thelio-3990X/T/#u
Cc: Al Viro 
Cc: Eric W. Biederman 
Cc: Hari Bathini 
Cc: Klara Modin 
Cc: Michael Kelley 
Cc: Pingfan Liu 
Cc: Stephen Rothwell 
Cc: Yang Li 
Signed-off-by: Andrew Morton

ARM: 9317/1: kexec: Make smp stop calls asynchronous

2023-08-14T11:16:59+00:00

If a panic is triggered by a hrtimer interrupt all online cpus will be
notified and set offline. But as highlighted by commit 19dbdcb8039c
("smp: Warn on function calls from softirq context") this call should
not be made synchronous with disabled interrupts:

 softdog: Initiating panic
 Kernel panic - not syncing: Software Watchdog Timer expired
 WARNING: CPU: 1 PID: 0 at kernel/smp.c:753 smp_call_function_many_cond
   unwind_backtrace:
     show_stack
     dump_stack_lvl
     __warn
     warn_slowpath_fmt
     smp_call_function_many_cond
     smp_call_function
     crash_smp_send_stop.part.0
     machine_crash_shutdown
     __crash_kexec
     panic
     softdog_fire
     __hrtimer_run_queues
     hrtimer_interrupt

Make the smp call for machine_crash_nonpanic_core() asynchronous.

Signed-off-by: Mårten Lindahl 
Signed-off-by: Russell King (Oracle)

Merge tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm

2022-12-13T23:22:14+00:00

Pull ARM updates from Russell King:

 - update unwinder to cope with module PLTs

 - enable UBSAN on ARM

 - improve kernel fault message

 - update UEFI runtime page tables dump

 - avoid clang's __aeabi_uldivmod generated in NWFPE code

 - disable FIQs on CPU shutdown paths

 - update XOR register usage

 - a number of build updates (using .arch, thread pointer, removal of
   lazy evaluation in Makefile)

 - conversion of stacktrace code to stackwalk

 - findbit assembly updates

 - hwcap feature updates for ARMv8 CPUs

 - instruction dump updates for big-endian platforms

 - support for function error injection

* tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm: (31 commits)
  ARM: 9279/1: support function error injection
  ARM: 9277/1: Make the dumped instructions are consistent with the disassembled ones
  ARM: 9276/1: Refactor dump_instr()
  ARM: 9275/1: Drop '-mthumb' from AFLAGS_ISA
  ARM: 9274/1: Add hwcap for Speculative Store Bypassing Safe
  ARM: 9273/1: Add hwcap for Speculation Barrier(SB)
  ARM: 9272/1: vfp: Add hwcap for FEAT_AA32I8MM
  ARM: 9271/1: vfp: Add hwcap for FEAT_AA32BF16
  ARM: 9270/1: vfp: Add hwcap for FEAT_FHM
  ARM: 9269/1: vfp: Add hwcap for FEAT_DotProd
  ARM: 9268/1: vfp: Add hwcap FPHP and ASIMDHP for FEAT_FP16
  ARM: 9267/1: Define Armv8 registers in AArch32 state
  ARM: findbit: add unwinder information
  ARM: findbit: operate by words
  ARM: findbit: convert to macros
  ARM: findbit: provide more efficient ARMv7 implementation
  ARM: findbit: document ARMv5 bit offset calculation
  ARM: 9259/1: stacktrace: Convert stacktrace to generic ARCH_STACKWALK
  ARM: 9258/1: stacktrace: Make stack walk callback consistent with generic code
  ARM: 9265/1: pass -march= only to compiler
  ...

ARM: kexec: make machine_crash_nonpanic_core() static

2022-11-18T21:55:07+00:00

This symbol is not used outside of the file, so mark it static.

Fixes the following warning:

arch/arm/kernel/machine_kexec.c:76:6: warning: symbol 'machine_crash_nonpanic_core' was not declared. Should it be static?

Link: https://lkml.kernel.org/r/20220929042936.22012-5-bhe@redhat.com
Signed-off-by: Chen Lifu 
Signed-off-by: Baoquan He 
Acked-by: Baoquan He 
Cc: "Eric W . Biederman" 
Cc: Petr Mladek 
Cc: Russell King 
Cc: Benjamin Herrenschmidt 
Cc: Jianglei Nie 
Cc: Li Chen 
Cc: Michael Ellerman 
Cc: Paul Mackerras 
Cc: ye xingchen 
Cc: Zeal Robot 
Signed-off-by: Andrew Morton

ARM: 9257/1: Disable FIQs (but not IRQs) on CPUs shutdown paths

2022-11-07T14:19:02+00:00

Currently the regular CPU shutdown path for ARM disables IRQs/FIQs
in the secondary CPUs - smp_send_stop() calls ipi_cpu_stop(), which
is responsible for that. IRQs are architecturally masked when we
take an interrupt, but FIQs are high priority than IRQs, hence they
aren't masked. With that said, it makes sense to disable FIQs here,
but there's no need for (re-)disabling IRQs.

More than that: there is an alternative path for disabling CPUs,
in the form of function crash_smp_send_stop(), which is used for
kexec/panic path. This function relies on a SMP call that also
triggers a busy-wait loop [at machine_crash_nonpanic_core()], but
without disabling FIQs. This might lead to odd scenarios, like
early interrupts in the boot of kexec'd kernel or even interrupts
in secondary "disabled" CPUs while the main one still works in the
panic path and assumes all secondary CPUs are (really!) off.

So, let's disable FIQs in both paths and *not* disable IRQs a second
time, since they are already masked in both paths by the architecture.
This way, we keep both CPU quiesce paths consistent and safe.

Cc: Marc Zyngier 
Cc: Michael Kelley 
Signed-off-by: Guilherme G. Piccoli 
Signed-off-by: Russell King (Oracle)

ARM: 9060/1: kexec: Remove unused kexec_reinit callback

2021-03-09T10:25:35+00:00

The last (only?) user of this was removed in commit ba364fc752da ("ARM:
Kirkwood: Remove mach-kirkwood"), back in v3.17.

Link: https://lore.kernel.org/r/20210210235243.398810-1-joel@jms.id.au

Signed-off-by: Joel Stanley 
Reviewed-by: Arnd Bergmann 
Signed-off-by: Russell King

ARM: kexec: fix oops after TLB are invalidated

2021-02-05T10:23:29+00:00

Giancarlo Ferrari reports the following oops while trying to use kexec:

 Unable to handle kernel paging request at virtual address 80112f38
 pgd = fd7ef03e
 [80112f38] *pgd=0001141e(bad)
 Internal error: Oops: 80d [#1] PREEMPT SMP ARM
 ...

This is caused by machine_kexec() trying to set the kernel text to be
read/write, so it can poke values into the relocation code before
copying it - and an interrupt occuring which changes the page tables.
The subsequent writes then hit read-only sections that trigger a
data abort resulting in the above oops.

Fix this by copying the relocation code, and then writing the variables
into the destination, thereby avoiding the need to make the kernel text
read/write.

Reported-by: Giancarlo Ferrari 
Tested-by: Giancarlo Ferrari 
Signed-off-by: Russell King

mm: remove unneeded includes of

2020-08-07T18:33:26+00:00

Patch series "mm: cleanup usage of "

Most architectures have very similar versions of pXd_alloc_one() and
pXd_free_one() for intermediate levels of page table.  These patches add
generic versions of these functions in  and enable
use of the generic functions where appropriate.

In addition, functions declared and defined in  headers are
used mostly by core mm and early mm initialization in arch and there is no
actual reason to have the  included all over the place.
The first patch in this series removes unneeded includes of


In the end it didn't work out as neatly as I hoped and moving
pXd_alloc_track() definitions to  would require
unnecessary changes to arches that have custom page table allocations, so
I've decided to move lib/ioremap.c to mm/ and make pgalloc-track.h local
to mm/.

This patch (of 8):

In most cases  header is required only for allocations of
page table memory.  Most of the .c files that include that header do not
use symbols declared in  and do not require that header.

As for the other header files that used to include , it is
possible to move that include into the .c file that actually uses symbols
from  and drop the include from the header file.

The process was somewhat automated using

	sed -i -E '/[<"]asm\/pgalloc\.h/d' \
                $(grep -L -w -f /tmp/xx \
                        $(git grep -E -l '[<"]asm/pgalloc\.h'))

where /tmp/xx contains all the symbols defined in
arch/*/include/asm/pgalloc.h.

[rppt@linux.ibm.com: fix powerpc warning]

Signed-off-by: Mike Rapoport 
Signed-off-by: Andrew Morton 
Reviewed-by: Pekka Enberg 
Acked-by: Geert Uytterhoeven 	[m68k]
Cc: Abdul Haleem 
Cc: Andy Lutomirski 
Cc: Arnd Bergmann 
Cc: Christophe Leroy 
Cc: Joerg Roedel 
Cc: Max Filippov 
Cc: Peter Zijlstra 
Cc: Satheesh Rajendran 
Cc: Stafford Horne 
Cc: Stephen Rothwell 
Cc: Steven Rostedt 
Cc: Joerg Roedel 
Cc: Matthew Wilcox 
Link: http://lkml.kernel.org/r/20200627143453.31835-1-rppt@kernel.org
Link: http://lkml.kernel.org/r/20200627143453.31835-2-rppt@kernel.org
Signed-off-by: Linus Torvalds

mm: don't include asm/pgtable.h if linux/mm.h is already included

2020-06-09T16:39:13+00:00

Patch series "mm: consolidate definitions of page table accessors", v2.

The low level page table accessors (pXY_index(), pXY_offset()) are
duplicated across all architectures and sometimes more than once.  For
instance, we have 31 definition of pgd_offset() for 25 supported
architectures.

Most of these definitions are actually identical and typically it boils
down to, e.g.

static inline unsigned long pmd_index(unsigned long address)
{
        return (address >> PMD_SHIFT) & (PTRS_PER_PMD - 1);
}

static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)
{
        return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(address);
}

These definitions can be shared among 90% of the arches provided
XYZ_SHIFT, PTRS_PER_XYZ and xyz_page_vaddr() are defined.

For architectures that really need a custom version there is always
possibility to override the generic version with the usual ifdefs magic.

These patches introduce include/linux/pgtable.h that replaces
include/asm-generic/pgtable.h and add the definitions of the page table
accessors to the new header.

This patch (of 12):

The linux/mm.h header includes  to allow inlining of the
functions involving page table manipulations, e.g.  pte_alloc() and
pmd_alloc().  So, there is no point to explicitly include 
in the files that include .

The include statements in such cases are remove with a simple loop:

	for f in $(git grep -l "include ") ; do
		sed -i -e '/include / d' $f
	done

Signed-off-by: Mike Rapoport 
Signed-off-by: Andrew Morton 
Cc: Arnd Bergmann 
Cc: Borislav Petkov 
Cc: Brian Cain 
Cc: Catalin Marinas 
Cc: Chris Zankel 
Cc: "David S. Miller" 
Cc: Geert Uytterhoeven 
Cc: Greentime Hu 
Cc: Greg Ungerer 
Cc: Guan Xuetao 
Cc: Guo Ren 
Cc: Heiko Carstens 
Cc: Helge Deller 
Cc: Ingo Molnar 
Cc: Ley Foon Tan 
Cc: Mark Salter 
Cc: Matthew Wilcox 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Ellerman 
Cc: Michal Simek 
Cc: Mike Rapoport 
Cc: Nick Hu 
Cc: Paul Walmsley 
Cc: Richard Weinberger 
Cc: Rich Felker 
Cc: Russell King 
Cc: Stafford Horne 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleixner 
Cc: Tony Luck 
Cc: Vincent Chen 
Cc: Vineet Gupta 
Cc: Will Deacon 
Cc: Yoshinori Sato 
Link: http://lkml.kernel.org/r/20200514170327.31389-1-rppt@kernel.org
Link: http://lkml.kernel.org/r/20200514170327.31389-2-rppt@kernel.org
Signed-off-by: Linus Torvalds

ARM: avoid Cortex-A9 livelock on tight dmb loops

2019-02-01T22:05:50+00:00

machine_crash_nonpanic_core() does this:

	while (1)
		cpu_relax();

because the kernel has crashed, and we have no known safe way to deal
with the CPU.  So, we place the CPU into an infinite loop which we
expect it to never exit - at least not until the system as a whole is
reset by some method.

In the absence of erratum 754327, this code assembles to:

	b	.

In other words, an infinite loop.  When erratum 754327 is enabled,
this becomes:

1:	dmb
	b	1b

It has been observed that on some systems (eg, OMAP4) where, if a
crash is triggered, the system tries to kexec into the panic kernel,
but fails after taking the secondary CPU down - placing it into one
of these loops.  This causes the system to livelock, and the most
noticable effect is the system stops after issuing:

	Loading crashdump kernel...

to the system console.

The tested as working solution I came up with was to add wfe() to
these infinite loops thusly:

	while (1) {
		cpu_relax();
		wfe();
	}

which, without 754327 builds to:

1:	wfe
	b	1b

or with 754327 is enabled:

1:	dmb
	wfe
	b	1b

Adding "wfe" does two things depending on the environment we're running
under:
- where we're running on bare metal, and the processor implements
  "wfe", it stops us spinning endlessly in a loop where we're never
  going to do any useful work.
- if we're running in a VM, it allows the CPU to be given back to the
  hypervisor and rescheduled for other purposes (maybe a different VM)
  rather than wasting CPU cycles inside a crashed VM.

However, in light of erratum 794072, Will Deacon wanted to see 10 nops
as well - which is reasonable to cover the case where we have erratum
754327 enabled _and_ we have a processor that doesn't implement the
wfe hint.

So, we now end up with:

1:      wfe
        b       1b

when erratum 754327 is disabled, or:

1:      dmb
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        nop
        wfe
        b       1b

when erratum 754327 is enabled.  We also get the dmb + 10 nop
sequence elsewhere in the kernel, in terminating loops.

This is reasonable - it means we get the workaround for erratum
794072 when erratum 754327 is enabled, but still relinquish the dead
processor - either by placing it in a lower power mode when wfe is
implemented as such or by returning it to the hypervisior, or in the
case where wfe is a no-op, we use the workaround specified in erratum
794072 to avoid the problem.

These as two entirely orthogonal problems - the 10 nops addresses
erratum 794072, and the wfe is an optimisation that makes the system
more efficient when crashed either in terms of power consumption or
by allowing the host/other VMs to make use of the CPU.

I don't see any reason not to use kexec() inside a VM - it has the
potential to provide automated recovery from a failure of the VMs
kernel with the opportunity for saving a crashdump of the failure.
A panic() with a reboot timeout won't do that, and reading the
libvirt documentation, setting on_reboot to "preserve" won't either
(the documentation states "The preserve action for an on_reboot event
is treated as a destroy".)  Surely it has to be a good thing to
avoiding having CPUs spinning inside a VM that is doing no useful
work.

Acked-by: Will Deacon 
Signed-off-by: Russell King