linux-toradex.git/arch/arm/vfp, branch v6.7

Merge branch 'devel-stable' into for-next

2023-08-14T11:18:06+00:00

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

2023-06-27T00:07:53+00:00

Pull ARM updates from Russell King:

 - lots of build cleanups from Arnd spread throughout the arch/arm tree

 - replace strlcpy() with the preferred strscpy()

 - use sign_extend32() in the module linker

 - drop handle_irq() machine descriptor method

* tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm:
  ARM: 9315/1: fiq: include asm/mach/irq.h for prototypes
  ARM: 9314/1: tcm: move tcm_init() prototype to asm/tcm.h
  ARM: 9313/1: vdso: add missing prototypes
  ARM: 9312/1: vfp: include asm/neon.h in vfpmodule.c
  ARM: 9311/1: decompressor: move function prototypes to misc.h
  ARM: 9310/1: xip-kernel: add __inflate_kernel_data prototype
  ARM: 9309/1: add missing syscall prototypes
  ARM: 9308/1: move setup functions to header
  ARM: 9307/1: nommu: include asm/idmap.h
  ARM: 9306/1: cacheflush: avoid __flush_anon_page() missing-prototype warning
  ARM: 9305/1: add clear/copy_user_highpage declarations
  ARM: 9304/1: add prototype for function called only from asm
  ARM: 9303/1: kprobes: avoid missing-declaration warnings
  ARM: 9302/1: traps: hide unused functions on NOMMU
  ARM: 9301/1: dma-mapping: hide unused dma_contiguous_early_fixup function
  ARM: 9300/1: Replace all non-returning strlcpy with strscpy
  ARM: 9299/1: module: use sign_extend32() to extend the signedness
  ARM: 9298/1: Drop custom mdesc->handle_irq()

ARM: 9312/1: vfp: include asm/neon.h in vfpmodule.c

2023-06-19T08:35:58+00:00

Two functions defined here need the declaration in a header
to avoid W=1 warnings:

arch/arm/vfp/vfpmodule.c:735:6: error: no previous prototype for 'kernel_neon_begin' [-Werror=missing-prototypes]
arch/arm/vfp/vfpmodule.c:768:6: error: no previous prototype for 'kernel_neon_end' [-Werror=missing-prototypes]

Reviewed-by: Kees Cook 
Signed-off-by: Arnd Bergmann 
Signed-off-by: Russell King (Oracle)

ARM: vfp: Use undef hook for handling VFP exceptions

2023-05-17T13:08:22+00:00

Now that the VFP support code has been reimplemented as a C function
that takes a struct pt_regs pointer and an opcode, we can use the
existing undef_hook framework to deal with undef exceptions triggered by
VFP instructions instead of having special handling in assembler.

Reviewed-by: Linus Walleij 
Signed-off-by: Ard Biesheuvel

ARM: vfp: Reimplement VFP exception entry in C code

2023-05-17T13:08:14+00:00

En/disabling softirqs from asm code turned out to be trickier than
expected, so vfp_support_entry now returns by tail calling
__local_enable_bh_ip() and passing the same arguments that a C call to
local_bh_enable() would pass. However, this is slightly hacky, as we
don't want to carry our own implementation of local_bh_enable().

So let's bite the bullet, and get rid of the asm logic in
vfp_support_entry that reasons about whether or not to save and/or
reload the VFP state, and about whether or not an FP exception is
pending, and only keep the VFP loading logic as a function that is
callable from C.

Replicate the removed logic in vfp_entry(), and use the exact same
reasoning as in the asm code. To emphasize the correspondence, retain
some of the asm comments in the C version as well.

Signed-off-by: Ard Biesheuvel 
Acked-by: Linus Walleij

ARM: vfp: Remove workaround for Feroceon CPUs

2023-05-17T11:11:38+00:00

Feroceon CPUs have a non-standard implementation of VFP which reports
synchronous VFP exceptions using the async VFP flag. This requires a
workaround which is difficult to reconcile with other implementations,
making it tricky to support both versions in a single image.

Since this is a v5 CPU, it is not supported by armhf and so the
likelihood that anybody is using this with recent distros/kernels and
rely on the VFP at the same time is extremely low. So let's just disable
VFP support on these cores, so we can remove the workaround.

This will help future development to support v5 and v6 CPUs with a
single kernel image.

Reviewed-by: Linus Walleij 
Acked-by: Nicolas Pitre 
Acked-by: Arnd Bergmann 
Signed-off-by: Ard Biesheuvel

ARM: vfp: Record VFP bounces as perf emulation faults

2023-05-16T18:24:08+00:00

VFP 'bouncing' occurs when the VFP unit cannot complete the execution of
a VFP instruction, either because it is not implemented at all, or
because the values of the arguments are out of range for the hardware
implementation, and the software needs to step in to complete the
operation.

To give some insight in how much certain programs rely on this bouncing,
record the emulation of a VFP instruction in perf's emulation-faults
counter.

This can be used like so

  perf stat -e emulation-faults ./testfloat -all2

and the output will be something like

 Performance counter stats for './testfloat -all2':

           259,277      emulation-faults:u

       6.846432176 seconds time elapsed

Reviewed-by: Linus Walleij 
Signed-off-by: Ard Biesheuvel

ARM: 9297/1: vfp: avoid unbalanced stack on 'success' return path

2023-05-10T09:50:25+00:00

Commit c76c6c4ecbec0deb5 ("ARM: 9294/2: vfp: Fix broken softirq handling
with instrumentation enabled") updated the VFP exception entry logic to
go via a C function, so that we get the compiler's version of
local_bh_disable(), which may be instrumented, and isn't generally
callable from assembler.

However, this assumes that passing an alternative 'success' return
address works in C as it does in asm, and this is only the case if the C
calls in question are tail calls, as otherwise, the stack will need some
unwinding as well.

I have already sent patches to the list that replace most of the asm
logic with C code, and so it is preferable to have a minimal fix that
addresses the issue and can be backported along with the commit that it

fixes to v6.3 from v6.4. Hopefully, we can land the C conversion for v6.5.

So instead of passing the 'success' return address as a function
argument, pass the stack address from where to pop it so that both LR
and SP have the expected value.

Fixes: c76c6c4ecbec0deb5 ("ARM: 9294/2: vfp: Fix broken softirq handling with ...")
Reported-by: syzbot+d4b00edc2d0c910d4bf4@syzkaller.appspotmail.com
Tested-by: syzbot+d4b00edc2d0c910d4bf4@syzkaller.appspotmail.com
Reviewed-by: Linus Walleij 
Tested-by: Andrew Lunn 
Signed-off-by: Ard Biesheuvel 
Tested-by: Andre Przywara 
Signed-off-by: Russell King (Oracle)

ARM: 9294/2: vfp: Fix broken softirq handling with instrumentation enabled

2023-04-12T09:04:56+00:00

Commit 62b95a7b44d1 ("ARM: 9282/1: vfp: Manipulate task VFP state with
softirqs disabled") replaced the en/disable preemption calls inside the
VFP state handling code with en/disabling of soft IRQs, which is
necessary to allow kernel use of the VFP/SIMD unit when handling a soft
IRQ.

Unfortunately, when lockdep is enabled (or other instrumentation that
enables TRACE_IRQFLAGS), the disable path implemented in asm fails to
perform the lockdep and RCU related bookkeeping, resulting in spurious
warnings and other badness.

Set let's rework the VFP entry code a little bit so we can make the
local_bh_disable() call from C, with all the instrumentations that
happen to have been configured. Calling local_bh_enable() can be done
from asm, as it is a simple wrapper around __local_bh_enable_ip(), which
is always a callable function.

Link: https://lore.kernel.org/all/ZBBYCSZUJOWBg1s8@localhost.localdomain/

Fixes: 62b95a7b44d1 ("ARM: 9282/1: vfp: Manipulate task VFP state with softirqs disabled")
Signed-off-by: Ard Biesheuvel 
Reviewed-by: Linus Walleij 
Tested-by: Guenter Roeck 
Signed-off-by: Russell King (Oracle)

ARM: 9293/1: vfp: Pass successful return address via register R3

2023-04-11T10:07:10+00:00

In preparation for reimplementing the do_vfp()->vfp_support_entry()
handover in C code, switch to using R3 to pass the 'success' return
address, rather than R9, as it cannot be used for parameter passing.

Signed-off-by: Ard Biesheuvel 
Reviewed-by: Linus Walleij 
Tested-by: Guenter Roeck 
Signed-off-by: Russell King (Oracle)