There is a build issue with LD segmentation fault, while
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is not enabled, as bellow.

scripts/link-vmlinux.sh: line 49:  3796 Segmentation fault
 (core dumped) ${ld} ${ldflags} -o ${output} ${wl}--whole-archive
 ${objs} ${wl}--no-whole-archive ${wl}--start-group
 ${libs} ${wl}--end-group ${kallsymso} ${btf_vmlinux_bin_o} ${ldlibs}

The error occurs in older versions of the GNU ld with version earlier
than 2.36. It makes most sense to have a minimum LD version as
a dependency for HAVE_LD_DEAD_CODE_DATA_ELIMINATION and eliminate
the impact of ".reloc  .text, R_ARM_NONE, ." when
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is not enabled.

Fixes: ed0f94102251 ("ARM: 9404/1: arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION")
Reported-by: Harith George <mail2hgg@gmail.com>
Tested-by: Harith George <mail2hgg@gmail.com>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Yuntao Liu <liuyuntao12@huawei.com>
Link: https://lore.kernel.org/all/14e9aefb-88d1-4eee-8288-ef15d4a9b059@gmail.com/
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

Pull ARM updates from Russell King:

 - ftrace: don't assume stack frames are contiguous in memory

 - remove unused mod_inwind_map structure

 - spelling fixes

 - allow use of LD dead code/data elimination

 - fix callchain_trace() return value

 - add support for stackleak gcc plugin

 - correct some reset asm function prototypes for CFI

[ Missed the merge window because Russell forgot to push out ]

* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rmk/linux:
  ARM: 9408/1: mm: CFI: Fix some erroneous reset prototypes
  ARM: 9407/1: Add support for STACKLEAK gcc plugin
  ARM: 9406/1: Fix callchain_trace() return value
  ARM: 9404/1: arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION
  ARM: 9403/1: Alpine: Spelling s/initialiing/initializing/
  ARM: 9402/1: Kconfig: Spelling s/Cortex A-/Cortex-A/
  ARM: 9400/1: Remove unused struct 'mod_unwind_map'

Pull arm64 updates from Catalin Marinas:
 "The biggest part is the virtual CPU hotplug that touches ACPI,
  irqchip. We also have some GICv3 optimisation for pseudo-NMIs that has
  been queued via the arm64 tree. Otherwise the usual perf updates,
  kselftest, various small cleanups.

  Core:

   - Virtual CPU hotplug support for arm64 ACPI systems

   - cpufeature infrastructure cleanups and making the FEAT_ECBHB ID
     bits visible to guests

   - CPU errata: expand the speculative SSBS workaround to more CPUs

   - GICv3, use compile-time PMR values: optimise the way regular IRQs
     are masked/unmasked when GICv3 pseudo-NMIs are used, removing the
     need for a static key in fast paths by using a priority value
     chosen dynamically at boot time

  ACPI:

   - 'acpi=nospcr' option to disable SPCR as default console for arm64

   - Move some ACPI code (cpuidle, FFH) to drivers/acpi/arm64/

  Perf updates:

   - Rework of the IMX PMU driver to enable support for I.MX95

   - Enable support for tertiary match groups in the CMN PMU driver

   - Initial refactoring of the CPU PMU code to prepare for the fixed
     instruction counter introduced by Arm v9.4

   - Add missing PMU driver MODULE_DESCRIPTION() strings

   - Hook up DT compatibles for recent CPU PMUs

  Kselftest updates:

   - Kernel mode NEON fp-stress

   - Cleanups, spelling mistakes

  Miscellaneous:

   - arm64 Documentation update with a minor clarification on TBI

   - Fix missing IPI statistics

   - Implement raw_smp_processor_id() using thread_info rather than a
     per-CPU variable (better code generation)

   - Make MTE checking of in-kernel asynchronous tag faults conditional
     on KASAN being enabled

   - Minor cleanups, typos"

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (69 commits)
  selftests: arm64: tags: remove the result script
  selftests: arm64: tags_test: conform test to TAP output
  perf: add missing MODULE_DESCRIPTION() macros
  arm64: smp: Fix missing IPI statistics
  irqchip/gic-v3: Fix 'broken_rdists' unused warning when !SMP and !ACPI
  ACPI: Add acpi=nospcr to disable ACPI SPCR as default console on ARM64
  Documentation: arm64: Update memory.rst for TBI
  arm64/cpufeature: Replace custom macros with fields from ID_AA64PFR0_EL1
  KVM: arm64: Replace custom macros with fields from ID_AA64PFR0_EL1
  perf: arm_pmuv3: Include asm/arm_pmuv3.h from linux/perf/arm_pmuv3.h
  perf: arm_v6/7_pmu: Drop non-DT probe support
  perf/arm: Move 32-bit PMU drivers to drivers/perf/
  perf: arm_pmuv3: Drop unnecessary IS_ENABLED(CONFIG_ARM64) check
  perf: arm_pmuv3: Avoid assigning fixed cycle counter with threshold
  arm64: Kconfig: Fix dependencies to enable ACPI_HOTPLUG_CPU
  perf: imx_perf: add support for i.MX95 platform
  perf: imx_perf: fix counter start and config sequence
  perf: imx_perf: refactor driver for imx93
  perf: imx_perf: let the driver manage the counter usage rather the user
  perf: imx_perf: add macro definitions for parsing config attr
  ...

It is preferred to put drivers under drivers/ rather than under arch/.
The PMU drivers also depend on arm_pmu.c, so it's better to place them
all together.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20240626-arm-pmu-3-9-icntr-v2-3-c9784b4f4065@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

Add the STACKLEAK gcc plugin to arm32 by adding the helper used by
stackleak common code: on_thread_stack(). It initialize the stack with the
poison value before returning from system calls which improves the kernel
security. Additionally, this disables the plugin in EFI stub code and
decompress code, which are out of scope for the protection.

Before the test on Qemu versatilepb board:
	# echo STACKLEAK_ERASING  > /sys/kernel/debug/provoke-crash/DIRECT
	lkdtm: Performing direct entry STACKLEAK_ERASING
	lkdtm: XFAIL: stackleak is not supported on this arch (HAVE_ARCH_STACKLEAK=n)

After:
	# echo STACKLEAK_ERASING  > /sys/kernel/debug/provoke-crash/DIRECT
	lkdtm: Performing direct entry STACKLEAK_ERASING
	lkdtm: stackleak stack usage:
	  high offset: 80 bytes
	  current:     280 bytes
	  lowest:      696 bytes
	  tracked:     696 bytes
	  untracked:   192 bytes
	  poisoned:    7220 bytes
	  low offset:  4 bytes
	lkdtm: OK: the rest of the thread stack is properly erased

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

perf_callchain_store() return 0 on success, -1 otherwise, fix
callchain_trace() to return correct bool value. So walk_stackframe() can
have a chance to stop walking the stack ahead.

Fixes: 70ccc7c0667b ("ARM: 9258/1: stacktrace: Make stack walk callback consistent with generic code")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

The current arm32 architecture does not yet support the
HAVE_LD_DEAD_CODE_DATA_ELIMINATION feature. arm32 is widely used in
embedded scenarios, and enabling this feature would be beneficial for
reducing the size of the kernel image.

In order to make this work, we keep the necessary tables by annotating
them with KEEP, also it requires further changes to linker script to KEEP
some tables and wildcard compiler generated sections into the right place.
When using ld.lld for linking, KEEP is not recognized within the OVERLAY
command, and Ard proposed a concise method to solve this problem.

It boots normally with defconfig, vexpress_defconfig and tinyconfig.

The size comparison of zImage is as follows:
defconfig       vexpress_defconfig      tinyconfig
5137712         5138024                 424192          no dce
5032560         4997824                 298384          dce
2.0%            2.7%                    29.7%           shrink

When using smaller config file, there is a significant reduction in the
size of the zImage.

We also tested this patch on a commercially available single-board
computer, and the comparison is as follows:
a15eb_config
2161384         no dce
2092240         dce
3.2%            shrink

The zImage size has been reduced by approximately 3.2%, which is 70KB on
2.1M.

Signed-off-by: Yuntao Liu <liuyuntao12@huawei.com>
Tested-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

I think this has been unused since
Commit b6f21d14f1ac ("ARM: 9204/2: module: Add all unwind tables when
load module")

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

The frame pointer unwinder relies on a standard layout of the stack
frame, consisting of (in downward order)

   Calling frame:
     PC   <---------+
     LR             |
     SP             |
     FP             |
     .. locals ..   |
   Callee frame:    |
     PC             |
     LR             |
     SP             |
     FP   ----------+

where after storing its previous value on the stack, FP is made to point
at the location of PC in the callee stack frame, using the canonical
prologue:

   mov     ip, sp
   stmdb   sp!, {fp, ip, lr, pc}
   sub     fp, ip, #4

The ftrace code assumes that this activation record is pushed first, and
that any stack space for locals is allocated below this. Strict
adherence to this would imply that the caller's value of SP at the time
of the function call can always be obtained by adding 4 to FP (which
points to PC in the callee frame).

However, recent versions of GCC appear to deviate from this rule, and so
the only reliable way to obtain the caller's value of SP is to read it
from the activation record. Since this involves a read from memory
rather than simple arithmetic, we need to use the uaccess API here which
protects against inadvertent data aborts resulting from attempts to
dereference bogus FP values.

The plain uaccess API is ftrace instrumented itself, so to avoid
unbounded recursion, use the __get_kernel_nofault() primitive directly.

Closes: https://lore.kernel.org/all/alp44tukzo6mvcwl4ke4ehhmojrqnv6xfcdeuliybxfjfvgd3e@gpjvwj33cc76

Closes: https://lore.kernel.org/all/d870c149-4363-43de-b0ea-7125dec5608e@broadcom.com/

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reported-by: Justin Chen <justin.chen@broadcom.com>
Tested-by: Thorsten Scherer <t.scherer@eckelmann.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>