m68k: Fix spinlock race in kernel thread creation

Context switching does take care to retain the correct lock owner across
the switch from 'prev' to 'next' tasks. This does rely on interrupts
remai

m68k: Fix spinlock race in kernel thread creation

Context switching does take care to retain the correct lock owner across
the switch from 'prev' to 'next' tasks. This does rely on interrupts
remaining disabled for the entire duration of the switch.

This condition is guaranteed for normal process creation and context
switching between already running processes, because both 'prev' and
'next' already have interrupts disabled in their saved copies of the
status register.

The situation is different for newly created kernel threads. The status
register is set to PS_S in copy_thread(), which does leave the IPL at 0.
Upon restoring the 'next' thread's status register in switch_to() aka
resume(), interrupts then become enabled prematurely. resume() then
returns via ret_from_kernel_thread() and schedule_tail() where run queue
lock is released (see finish_task_switch() and finish_lock_switch()).

A timer interrupt calling scheduler_tick() before the lock is released
in finish_task_switch() will find the lock already taken, with the
current task as lock owner. This causes a spinlock recursion warning as
reported by Guenter Roeck.

As far as I can ascertain, this race has been opened in commit
533e6903bea0 ("m68k: split ret_from_fork(), simplify kernel_thread()")
but I haven't done a detailed study of kernel history so it may well
predate that commit.

Interrupts cannot be disabled in the saved status register copy for
kernel threads (init will complain about interrupts disabled when
finally starting user space). Disable interrupts temporarily when
switching the tasks' register sets in resume().

Note that a simple oriw 0x700,%sr after restoring sr is not enough here
- this leaves enough of a race for the 'spinlock recursion' warning to
still be observed.

Tested on ARAnyM and qemu (Quadra 800 emulation).

Fixes: 533e6903bea0 ("m68k: split ret_from_fork(), simplify kernel_thread()")
Reported-by: Guenter Roeck <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]
Signed-off-by: Michael Schmitz <[email protected]>
Tested-by: Guenter Roeck <[email protected]>
Reviewed-by: Geert Uytterhoeven <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Geert Uytterhoeven <[email protected]>

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m68k: Replace GPL 2.0+ README.legal boilerplate with SPDX

Upstream Linux never had a "README.legal" file, but it was present
in early source releases of Linux/m68k. It contained a simple copyright

m68k: Replace GPL 2.0+ README.legal boilerplate with SPDX

Upstream Linux never had a "README.legal" file, but it was present
in early source releases of Linux/m68k. It contained a simple copyright
notice and a link to a version of the "COPYING" file that predated the
addition of the "only valid GPL version is v2" clause.

Get rid of the references to non-existent files by replacing the
boilerplate with SPDX license identifiers.

Signed-off-by: Geert Uytterhoeven <[email protected]>
Acked-by: Greg Ungerer <[email protected]>
Link: https://lore.kernel.org/r/23430c233728ab02ec0af8e714994398d383137a.1695031668.git.geert@linux-m68k.org

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m68k: Add kernel seccomp support

Add secure_computing() call to syscall_trace_enter to actually
filter system calls.

Add necessary arch Kconfig options, define TIF_SECCOMP trace
flag and provide ba

m68k: Add kernel seccomp support

Add secure_computing() call to syscall_trace_enter to actually
filter system calls.

Add necessary arch Kconfig options, define TIF_SECCOMP trace
flag and provide basic seccomp filter support in asm/syscall.h

syscall_get_nr currently uses the syscall nr stored in orig_d0
because we change d0 to a default return code before starting a
syscall trace. This may be inconsistent with syscall_rollback
copying orig_d0 to d0 (which we never check upon return from
trace). We use d0 for the return code from syscall_trace_enter
in entry.S currently, and could perhaps expand that to store
a new syscall number returned by the seccomp filter before
executing the syscall. This clearly needs some discussion.

seccomp_bpf self test on ARAnyM passes 81 out of 94 tests.

Signed-off-by: Michael Schmitz <[email protected]>
Reviewed-by: Geert Uytterhoeven <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Geert Uytterhoeven <[email protected]>

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m68k: Check syscall_trace_enter() return code

Check return code of syscall_trace_enter(), and skip syscall
if -1. Return code will be left at what had been set by
ptrace or seccomp (in regs->d0).

N

m68k: Check syscall_trace_enter() return code

Check return code of syscall_trace_enter(), and skip syscall
if -1. Return code will be left at what had been set by
ptrace or seccomp (in regs->d0).

No regression seen in testing with strace on ARAnyM.

Signed-off-by: Michael Schmitz <[email protected]>
Reviewed-by: Geert Uytterhoeven <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Geert Uytterhoeven <[email protected]>

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m68k: Wire up syscall_trace_enter/leave for m68k

m68k (other than Coldfire) uses syscall_trace for both trace entry
and trace exit. Seccomp support requires separate entry points for
trace entry and

m68k: Wire up syscall_trace_enter/leave for m68k

m68k (other than Coldfire) uses syscall_trace for both trace entry
and trace exit. Seccomp support requires separate entry points for
trace entry and exit which are already provided for Coldfire.

Replace syscall_trace by syscall_trace_enter and syscall_trace_leave
in preparation for seccomp support.

No regression seen in testing with strace on ARAnyM.

Signed-off-by: Michael Schmitz <[email protected]>
Acked-by: "Eric W. Biederman" <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Geert Uytterhoeven <[email protected]>

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m68k: Remove set_fs()

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 ke

m68k: Remove set_fs()

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 <[email protected]>.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Michael Schmitz <[email protected]>
Tested-by: Michael Schmitz <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Geert Uytterhoeven <[email protected]>

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

sigreturn has to deal with an unpleasant problem - exception stack frames
have different sizes, depending upon the exception (and processor m

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

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 <[email protected]>
Tested-by: Michael Schmitz <[email protected]>
Reviewed-by: Michael Schmitz <[email protected]>
Tested-by: Finn Thain <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Geert Uytterhoeven <[email protected]>

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

We get there when sigreturn has performed obscene acts on kernel stack;
in particular, the location of pt_regs has shifte

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

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 <[email protected]>
Fixes: bd6f56a75bb2 ("m68k: Missing syscall_trace() on sigreturn")
Signed-off-by: Al Viro <[email protected]>
Tested-by: Michael Schmitz <[email protected]>
Reviewed-by: Michael Schmitz <[email protected]>
Tested-by: Finn Thain <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Geert Uytterhoeven <[email protected]>

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m68k: Wire up clone3() syscall

Wire up the clone3() syscall for m68k. The special entry point is done in
assembler as was done for clone() as well. This is needed because all
registers need to be sa

m68k: Wire up clone3() syscall

Wire up the clone3() syscall for m68k. The special entry point is done in
assembler as was done for clone() as well. This is needed because all
registers need to be saved. The C wrapper then calls the generic
sys_clone3() with the correct arguments.

Tested on A1200 using the simple test program from:

https://lore.kernel.org/lkml/[email protected]/

Signed-off-by: Kars de Jong <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Geert Uytterhoeven <[email protected]>

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m68k: Use conventional function parameters for do_sigreturn

Create conventional stack parameters for the calls to do_sigreturn and
do_rt_sigreturn. The current C code for do_sigreturn and do_rt_sigr

m68k: Use conventional function parameters for do_sigreturn

Create conventional stack parameters for the calls to do_sigreturn and
do_rt_sigreturn. The current C code for do_sigreturn and do_rt_sigreturn
dig into the stack to create local pointers to the saved switch stack
and the pt_regs structs.

The motivation for this change is a problem with non-MMU targets that
have broken signal return paths on newer versions of gcc. It appears as
though gcc has determined that the pointers into the saved stack structs,
and the saved structs themselves, are function parameters and updates to
them will be lost on function return, so they are optimized away. This
results in large parts of restore_sigcontext() and mangle_kernel_stack()
functions being removed. Of course this results in non-functional code
causing kernel oops. This problem has been observed with gcc version
5.2 and 5.3, and probably exists in earlier versions as well.

Using conventional stack parameter pointers passed to these functions has
the advantage of the code here not needing to know the exact details of
how the underlying entry handler layed these structs out on the stack.
So the rather ugly pointer setup casting and arg referencing can be
removed.

The resulting code after this change is a few bytes larger (due to the
overhead of creating the stack args and their tear down). Not being hot
paths I don't think this is too much of a problem here.

An alternative solution is to put a barrier() in the do_sigreturn() code,
but this doesn't feel quite as clean as this solution.

This change has been compile tested on all defconfigs, and run tested on
Atari (through aranym), ColdFire with MMU (M5407EVB) and ColdFire with
no-MMU (QEMU and M5208EVB).

Signed-off-by: Greg Ungerer <[email protected]>
Acked-by: Andreas Schwab <[email protected]>
Signed-off-by: Geert Uytterhoeven <[email protected]>

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m68k: Simplify low level interrupt handling code

The low level interrupt entry code of m68k contains the following:

add_preempt_count(HARDIRQ_OFFSET);

do_IRQ();
irq_enter();
add_pree

m68k: Simplify low level interrupt handling code

The low level interrupt entry code of m68k contains the following:

add_preempt_count(HARDIRQ_OFFSET);

do_IRQ();
irq_enter();
add_preempt_count(HARDIRQ_OFFSET);
handle_interrupt();
irq_exit();
sub_preempt_count(HARDIRQ_OFFSET);
if (in_interrupt())
return; <---- On m68k always taken!
if (local_softirq_pending())
do_softirq();

sub_preempt_count(HARDIRQ_OFFSET);
if (in_hardirq())
return;
if (status_on_stack_has_interrupt_priority_mask > 0)
return;
if (local_softirq_pending())
do_softirq();

ret_from_exception:
if (interrupted_context_is_kernel)
return:
....

I tried to find a proper explanation for this, but the changelog is
sparse and there are no mails explaining it further. But obviously
this relates to the interrupt priority levels of the m68k and tries to
be extra clever with nested interrupts. Though this cleverness just
adds code bloat to the interrupt hotpath.

For the common case of non nested interrupts the code runs through two
extra conditionals to the only important one, which checks whether the
return is to kernel or user space.

For the nested case the checks for in_hardirq() and the priority mask
value on stack catch only the case where the nested interrupt happens
inside the hard irq context of the first interrupt. If the nested
interrupt happens while the first interrupt handles soft interrupts,
then these extra checks buy nothing. The nested interrupt will fall
through to the final kernel/user space return check at
ret_from_exception.

Changing the code flow in the following way:

do_IRQ();
irq_enter();
add_preempt_count(HARDIRQ_OFFSET);
handle_interrupt();
irq_exit();
sub_preempt_count(HARDIRQ_OFFSET);
if (in_interrupt())
return;
if (local_softirq_pending())
do_softirq();

ret_from_exception:
if (interrupted_context_is_kernel)
return:

makes the region protected by the hardirq count slightly smaller and
the softirq handling is invoked with a minimal deeper stack. But
otherwise it's completely functional equivalent and saves 104 bytes of
text in arch/m68k/kernel/entry.o.

This modification allows us further to get rid of the limitations
which m68k puts on the preempt_count layout, so we can make the
preempt count bits completely generic.

Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Michael Schmitz <[email protected]>
Acked-by: Geert Uytterhoeven <[email protected]>
Cc: Linux/m68k <[email protected]>
Cc: Andreas Schwab <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]

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m68k: sanitize copy_thread(), fork/vfork/clone wrappers, switch to generic fork/vfork

Signed-off-by: Al Viro <[email protected]>

m68k: switch to saner kernel_execve() semantics

Acked-by: Greg Ungerer <[email protected]>
Signed-off-by: Al Viro <[email protected]>

m68k: switch to generic sys_execve()/kernel_execve()

The tricky part here is that task_pt_regs() on m68k works *only* for
process inside do_signal(). However, we need something much simpler -
pt_re

m68k: switch to generic sys_execve()/kernel_execve()

The tricky part here is that task_pt_regs() on m68k works *only* for
process inside do_signal(). However, we need something much simpler -
pt_regs of a process inside do_signal() may be at different offsets
from the stack bottom, depending on the way we'd entered the kernel,
but for a task inside sys_execve() it *is* at constant offset.
Moreover, for a kernel thread about to become a userland process the
same location is also fine - setting sp to that will leave the kernel
stack pointer at the very bottom of the kernel stack when we finally
switch to userland.

Signed-off-by: Al Viro <[email protected]>

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m68k: split ret_from_fork(), simplify kernel_thread()

Signed-off-by: Al Viro <[email protected]>

m68k: merge the MMU and non-MMU versions of the entry.S code

Some of the entry.S code is common to both MMU and non-MMU builds.
So merge the entry_no.S and entry_mm.S files back into a single file.

m68k: merge the MMU and non-MMU versions of the entry.S code

Some of the entry.S code is common to both MMU and non-MMU builds.
So merge the entry_no.S and entry_mm.S files back into a single file.
With a little code movement we only need a single #ifdef.

Signed-off-by: Greg Ungerer <[email protected]>
Acked-by: Geert Uytterhoeven <[email protected]>

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m68k: use non-MMU entry.S code when compiling for ColdFire CPU

No matter whether we are configured for non-MMU or MMU enabled if we are
compiling for ColdFire CPU we always use the entry_no.S code.

m68k: use non-MMU entry.S code when compiling for ColdFire CPU

No matter whether we are configured for non-MMU or MMU enabled if we are
compiling for ColdFire CPU we always use the entry_no.S code.

Signed-off-by: Greg Ungerer <[email protected]>
Acked-by: Geert Uytterhoeven <[email protected]>
Acked-by: Matt Waddel <[email protected]>
Acked-by: Kurt Mahan <[email protected]>

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m68k: merge m68k and m68knommu arch directories

There is a lot of common code that could be shared between the m68k
and m68knommu arch branches. It makes sense to merge the two branches
into a singl

m68k: merge m68k and m68knommu arch directories

There is a lot of common code that could be shared between the m68k
and m68knommu arch branches. It makes sense to merge the two branches
into a single directory structure so that we can more easily share
that common code.

This is a brute force merge, based on a script from Stephen King
<[email protected]>, which was originally written by Arnd Bergmann
<[email protected]>.

> The script was inspired by the script Sam Ravnborg used to merge the
> includes from m68knommu. For those files common to both arches but
> differing in content, the m68k version of the file is renamed to
> <file>_mm.<ext> and the m68knommu version of the file is moved into the
> corresponding m68k directory and renamed <file>_no.<ext> and a small
> wrapper file <file>.<ext> is used to select between the two version. Files
> that are common to both but don't differ are removed from the m68knommu
> tree and files and directories that are unique to the m68knommu tree are
> moved to the m68k tree. Finally, the arch/m68knommu tree is removed.
>
> To select between the the versions of the files, the wrapper uses
>
> #ifdef CONFIG_MMU
> #include <file>_mm.<ext>
> #else
> #include <file>_no.<ext>
> #endif

On top of this file merge I have done a simplistic merge of m68k and
m68knommu Kconfig, which primarily attempts to keep existing options and
menus in place. Other than a handful of options being moved it produces
identical .config outputs on m68k and m68knommu targets I tested it on.

With this in place there is now quite a bit of scope for merge cleanups
in future patches.

Signed-off-by: Greg Ungerer <[email protected]>

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m68k: Missing syscall_trace() on sigreturn

If we leave sigreturn via ret_from_signal, we end up with syscall
trace only on entry, leading to very unhappy strace, among other
things. Note that this

m68k: Missing syscall_trace() on sigreturn

If we leave sigreturn via ret_from_signal, we end up with syscall
trace only on entry, leading to very unhappy strace, among other
things. Note that this means different behaviours for signals
delivered while we were in pagefault and for ones delivered while
we were in interrupt...

Signed-off-by: Al Viro <[email protected]>
Signed-off-by: Geert Uytterhoeven <[email protected]>

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m68k: Simplify the singlestepping handling in signals

Instead of checking the return value of do_signal() we can just do
the work (raise SIGTRAP and clear SR.T1) directly in handle_signal(),
when se

m68k: Simplify the singlestepping handling in signals

Instead of checking the return value of do_signal() we can just do
the work (raise SIGTRAP and clear SR.T1) directly in handle_signal(),
when setting the sigframe up. Simplifies the assembler glue and is
closer to the way we do it on other targets.

Note that do_delayed_trace does *not* disappear; it's still needed
to deal with single-stepping through syscall, since 68040 doesn't
raise the trace exception at all if the trap exception is pending.
We hit it after returning from sys_...() if TIF_DELAYED_TRACE is
set; all that has changed is that we don't reuse it for "single-step
into the handler" codepath.

As the result, do_signal() doesn't need to return anything anymore.

Signed-off-by: Al Viro <[email protected]>
Signed-off-by: Geert Uytterhoeven <[email protected]>

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m68k: Switch to saner sigsuspend()

and saner do_signal() arguments, while we are at it

Signed-off-by: Al Viro <[email protected]>
Signed-off-by: Geert Uytterhoeven <[email protected]>

m68k,m68knommu: Wire up fanotify_init, fanotify_mark, and prlimit64

Signed-off-by: Geert Uytterhoeven <[email protected]>
Acked-by: Greg Ungerer <[email protected]>

Add generic sys_old_mmap()

Add a generic implementation of the old mmap() syscall, which expects its
argument in a memory block and switch all architectures over to use it.

Signed-off-by: Christoph

Add generic sys_old_mmap()

Add a generic implementation of the old mmap() syscall, which expects its
argument in a memory block and switch all architectures over to use it.

Signed-off-by: Christoph Hellwig <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: Jeff Dike <[email protected]>
Cc: Hirokazu Takata <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Reviewed-by: H. Peter Anvin <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: "Luck, Tony" <[email protected]>
Cc: James Morris <[email protected]>
Cc: Andreas Schwab <[email protected]>
Acked-by: Jesper Nilsson <[email protected]>
Acked-by: Russell King <[email protected]>
Acked-by: Greg Ungerer <[email protected]>
Acked-by: David Howells <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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Add generic sys_old_select()

Add a generic implementation of the old select() syscall, which expects
its argument in a memory block and switch all architectures over to use
it.

Signed-off-by: Chris

Add generic sys_old_select()

Add a generic implementation of the old select() syscall, which expects
its argument in a memory block and switch all architectures over to use
it.

Signed-off-by: Christoph Hellwig <[email protected]>
Cc: Ralf Baechle <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: Jeff Dike <[email protected]>
Cc: Hirokazu Takata <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Reviewed-by: H. Peter Anvin <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: "Luck, Tony" <[email protected]>
Cc: James Morris <[email protected]>
Acked-by: Andreas Schwab <[email protected]>
Acked-by: Russell King <[email protected]>
Acked-by: Greg Ungerer <[email protected]>
Acked-by: David Howells <[email protected]>
Cc: Andreas Schwab <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

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m68k: Add NPTL support

This patch adds several syscalls, that provide necessary
functionality to support NPTL on m68k/ColdFire.
The syscalls are get_thread_area, set_thread_area, atomic_cmpxchg_32 a

m68k: Add NPTL support

This patch adds several syscalls, that provide necessary
functionality to support NPTL on m68k/ColdFire.
The syscalls are get_thread_area, set_thread_area, atomic_cmpxchg_32 and
atomic_barrier.
The cmpxchg syscall is required for ColdFire as it doesn't support 'cas'
instruction.

Also a ptrace call PTRACE_GET_THREAD_AREA is added to allow debugger to
inspect the TLS storage.

Signed-off-by: Maxim Kuvyrkov <[email protected]>
Signed-off-by: Geert Uytterhoeven <[email protected]>

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