linux.git/arch/m68k, branch v5.15

m68k: Remove set_fs()

2021-09-24T11:35:07+00:00

Add a m68k-only set_fc helper to set the SFC and DFC registers for the
few places that need to override it for special MM operations, but
disconnect that from the deprecated kernel-wide set_fs() API.

Note that the SFC/DFC registers are context switched, so there is no need
to disable preemption.

Partially based on an earlier patch from
Linus Torvalds .

Signed-off-by: Christoph Hellwig 
Reviewed-by: Michael Schmitz 
Tested-by: Michael Schmitz 
Link: https://lore.kernel.org/r/20210916070405.52750-7-hch@lst.de
Signed-off-by: Geert Uytterhoeven

m68k: Provide __{get,put}_kernel_nofault

2021-09-24T11:35:07+00:00

Allow non-faulting access to kernel addresses without overriding the
address space.  Implemented by passing the instruction name to the
low-level assembly macros as an argument, and force the use of the
normal move instructions for kernel access.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Michael Schmitz 
Tested-by: Michael Schmitz 
Link: https://lore.kernel.org/r/20210916070405.52750-6-hch@lst.de
Signed-off-by: Geert Uytterhoeven

m68k: Factor the 8-byte lowlevel {get,put}_user code into helpers

2021-09-24T11:35:06+00:00

Add new helpers for doing the grunt work of the 8-byte {get,put}_user
routines to allow for better reuse.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Michael Schmitz 
Tested-by: Michael Schmitz 
Link: https://lore.kernel.org/r/20210916070405.52750-5-hch@lst.de
Signed-off-by: Geert Uytterhoeven

m68k: Use BUILD_BUG for passing invalid sizes to get_user/put_user

2021-09-24T11:35:06+00:00

Simplify the handling a bit by using the common helper instead of
referencing undefined symbols.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Michael Schmitz 
Tested-by: Michael Schmitz 
Link: https://lore.kernel.org/r/20210916070405.52750-4-hch@lst.de
Signed-off-by: Geert Uytterhoeven

m68k: Remove the 030 case in virt_to_phys_slow

2021-09-24T11:35:06+00:00

The 030 case in virt_to_phys_slow can't ever be reached, so remove it.

Suggested-by: Michael Schmitz 
Signed-off-by: Christoph Hellwig 
Reviewed-by: Michael Schmitz 
Tested-by: Michael Schmitz 
Link: https://lore.kernel.org/r/20210916070405.52750-3-hch@lst.de
Signed-off-by: Geert Uytterhoeven

m68k: Document that access_ok is broken for !CONFIG_CPU_HAS_ADDRESS_SPACES

2021-09-24T11:35:06+00:00

Document that access_ok is completely broken for coldfire and friends at
the moment.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Michael Schmitz 
Tested-by: Michael Schmitz 
Link: https://lore.kernel.org/r/20210916070405.52750-2-hch@lst.de
Signed-off-by: Geert Uytterhoeven

m68k: Leave stack mangling to asm wrapper of sigreturn()

2021-09-24T11:35:03+00:00

sigreturn has to deal with an unpleasant problem - exception stack frames
have different sizes, depending upon the exception (and processor model, as
well) and variable-sized part of exception frame may contain information
needed for instruction restart.  So when signal handler terminates and calls
sigreturn to resume the execution at the place where we'd been when we caught
the signal, it has to rearrange the frame at the bottom of kernel stack.
Worse, it might need to open a gap in the kernel stack, shifting pt_regs
towards lower addresses.

Doing that from C is insane - we'd need to shift stack frames (return addresses,
local variables, etc.) of C call chain, right under the nose of compiler and
hope it won't fall apart horribly.  What had been actually done is only slightly
less insane - an inline asm in mangle_kernel_stack() moved the stuff around,
then reset stack pointer and jumped to label in asm glue.

However, we can avoid all that mess if the asm wrapper we have to use anyway
would reserve some space on the stack between switch_stack and the C stack
frame of do_{rt_,}sigreturn().   Then C part can simply memmove() pt_regs +
switch_stack, memcpy() the variable part of exception frame into the opened
gap - all of that without inline asm, buggering C call chain, magical jumps
to asm labels, etc.

Asm wrapper would need to know where the moved switch_stack has ended up -
it might have been shifted into the gap we'd reserved before do_rt_sigreturn()
call.  That's where it needs to set the stack pointer to.  So let the C part
return just that and be done with that.

While we are at it, the call of berr_040cleanup() we need to do when
returning via 68040 bus error exception frame can be moved into C part
as well.

Signed-off-by: Al Viro 
Tested-by: Michael Schmitz 
Reviewed-by: Michael Schmitz 
Tested-by: Finn Thain 
Link: https://lore.kernel.org/r/YP2dTQPm1wGPWFgD@zeniv-ca.linux.org.uk
Signed-off-by: Geert Uytterhoeven

m68k: Update ->thread.esp0 before calling syscall_trace() in ret_from_signal

2021-09-24T11:35:01+00:00

We get there when sigreturn has performed obscene acts on kernel stack;
in particular, the location of pt_regs has shifted.  We are about to call
syscall_trace(), which might stop for tracer.  If that happens, we'd better
have task_pt_regs() returning correct result...

Fucked-up-by: Al Viro 
Fixes: bd6f56a75bb2 ("m68k: Missing syscall_trace() on sigreturn")
Signed-off-by: Al Viro 
Tested-by: Michael Schmitz 
Reviewed-by: Michael Schmitz 
Tested-by: Finn Thain 
Link: https://lore.kernel.org/r/YP2dMWeV1LkHiOpr@zeniv-ca.linux.org.uk
Signed-off-by: Geert Uytterhoeven

m68k: Handle arrivals of multiple signals correctly

2021-09-24T11:34:46+00:00

When we have several pending signals, have entered with the kernel
with large exception frame *and* have already built at least one
sigframe, regs->stkadj is going to be non-zero and regs->format/sr/pc
are going to be junk - the real values are in shifted exception stack
frame we'd built when putting together the first sigframe.

If that happens, subsequent sigframes are going to be garbage.
Not hard to fix - just need to find the "adjusted" frame first
and look for format/vector/sr/pc in it.

Signed-off-by: Al Viro 
Tested-by: Michael Schmitz 
Reviewed-by: Michael Schmitz 
Tested-by: Finn Thain 
Link: https://lore.kernel.org/r/YP2dBIAPTaVvHiZ6@zeniv-ca.linux.org.uk
Signed-off-by: Geert Uytterhoeven

m68k: mvme: Remove overdue #warnings in RTC handling

2021-09-13T09:19:05+00:00

The warnings were introduced when converting the MVME147 and MVME16x
RTC handling from gettod to hwclk.  Replace the #warning by a comment,
and return an error to inform the upper layer that writing to the RTC is
not yet supported.

Signed-off-by: Geert Uytterhoeven 
Reviewed-by: Guenter Roeck 
Link: https://lore.kernel.org/r/20210907124511.2723414-1-geert@linux-m68k.org