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  1. 30 Jun, 2017 4 commits
    • James Hogan's avatar
      MIPS: Avoid accidental raw backtrace · 85423636
      James Hogan authored 
      Since commit 81a76d71 ("MIPS: Avoid using unwind_stack() with
usermode") show_backtrace() invokes the raw backtracer when
cp0_status & ST0_KSU indicates user mode to fix issues on EVA kernels
where user and kernel address spaces overlap.

However this is used by show_stack() which creates its own pt_regs on
the stack and leaves cp0_status uninitialised in most of the code paths.
This results in the non deterministic use of the raw back tracer
depending on the previous stack content.

show_stack() deals exclusively with kernel mode stacks anyway, so
explicitly initialise regs.cp0_status to KSU_KERNEL (i.e. 0) to ensure
we get a useful backtrace.

Fixes: 81a76d71 ("MIPS: Avoid using unwind_stack() with usermode")
Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 3.15+
Patchwork: https://patchwork.linux-mips.org/patch/16656/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
      85423636
    • Paul Burton's avatar
      MIPS: Perform post-DMA cache flushes on systems with MAARs · cad482c1
      Paul Burton authored 
      Recent CPUs from Imagination Technologies such as the I6400 or P6600 are
able to speculatively fetch data from memory into caches. This means
that if used in a system with non-coherent DMA they require that caches
be invalidated after a device performs DMA, and before the CPU reads the
DMA'd data, in order to ensure that stale values weren't speculatively
prefetched.

Such CPUs also introduced Memory Accessibility Attribute Registers
(MAARs) in order to control the regions in which they are allowed to
speculate. Thus we can use the presence of MAARs as a good indication
that the CPU requires the above cache maintenance. Use the presence of
MAARs to determine the result of cpu_needs_post_dma_flush() in the
default case, in order to handle these recent CPUs correctly.

Note that the return type of cpu_needs_post_dma_flush() is changed to
bool, such that it's clearer what's happening when cpu_has_maar is cast
to bool for the return value. If this patch were backported to a
pre-v4.7 kernel then MIPS_CPU_MAAR was 1ull<<34, so when cast to an int
we would incorrectly return 0. It so happens that MIPS_CPU_MAAR is
currently 1ull<<30, so when truncated to an int gives a non-zero value
anyway, but even so the implicit conversion from long long int to bool
makes it clearer to understand what will happen than the implicit
conversion from long long int to int would. The bool return type also
fits this usage better semantically, so seems like an all-round win.

Thanks to Ed for spotting the issue for pre-v4.7 kernels & suggesting
the return type change.
Signed-off-by: default avatarPaul Burton <paul.burton@imgtec.com>
Reviewed-by: default avatarBryan O'Donoghue <pure.logic@nexus-software.ie>
Tested-by: default avatarBryan O'Donoghue <pure.logic@nexus-software.ie>
Cc: Ed Blake <ed.blake@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16363/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
      cad482c1
    • Paul Burton's avatar
      MIPS: Fix IRQ tracing & lockdep when rescheduling · d8550860
      Paul Burton authored 
      When the scheduler sets TIF_NEED_RESCHED & we call into the scheduler
from arch/mips/kernel/entry.S we disable interrupts. This is true
regardless of whether we reach work_resched from syscall_exit_work,
resume_userspace or by looping after calling schedule(). Although we
disable interrupts in these paths we don't call trace_hardirqs_off()
before calling into C code which may acquire locks, and we therefore
leave lockdep with an inconsistent view of whether interrupts are
disabled or not when CONFIG_PROVE_LOCKING & CONFIG_DEBUG_LOCKDEP are
both enabled.

Without tracing this interrupt state lockdep will print warnings such
as the following once a task returns from a syscall via
syscall_exit_partial with TIF_NEED_RESCHED set:

[   49.927678] ------------[ cut here ]------------
[   49.934445] WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:3687 check_flags.part.41+0x1dc/0x1e8
[   49.946031] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)
[   49.946355] CPU: 0 PID: 1 Comm: init Not tainted 4.10.0-00439-gc9fd5d362289-dirty #197
[   49.963505] Stack : 0000000000000000 ffffffff81bb5d6a 0000000000000006 ffffffff801ce9c4
[   49.974431]         0000000000000000 0000000000000000 0000000000000000 000000000000004a
[   49.985300]         ffffffff80b7e487 ffffffff80a24498 a8000000ff160000 ffffffff80ede8b8
[   49.996194]         0000000000000001 0000000000000000 0000000000000000 0000000077c8030c
[   50.007063]         000000007fd8a510 ffffffff801cd45c 0000000000000000 a8000000ff127c88
[   50.017945]         0000000000000000 ffffffff801cf928 0000000000000001 ffffffff80a24498
[   50.028827]         0000000000000000 0000000000000001 0000000000000000 0000000000000000
[   50.039688]         0000000000000000 a8000000ff127bd0 0000000000000000 ffffffff805509bc
[   50.050575]         00000000140084e0 0000000000000000 0000000000000000 0000000000040a00
[   50.061448]         0000000000000000 ffffffff8010e1b0 0000000000000000 ffffffff805509bc
[   50.072327]         ...
[   50.076087] Call Trace:
[   50.079869] [<ffffffff8010e1b0>] show_stack+0x80/0xa8
[   50.086577] [<ffffffff805509bc>] dump_stack+0x10c/0x190
[   50.093498] [<ffffffff8015dde0>] __warn+0xf0/0x108
[   50.099889] [<ffffffff8015de34>] warn_slowpath_fmt+0x3c/0x48
[   50.107241] [<ffffffff801c15b4>] check_flags.part.41+0x1dc/0x1e8
[   50.114961] [<ffffffff801c239c>] lock_is_held_type+0x8c/0xb0
[   50.122291] [<ffffffff809461b8>] __schedule+0x8c0/0x10f8
[   50.129221] [<ffffffff80946a60>] schedule+0x30/0x98
[   50.135659] [<ffffffff80106278>] work_resched+0x8/0x34
[   50.142397] ---[ end trace 0cb4f6ef5b99fe21 ]---
[   50.148405] possible reason: unannotated irqs-off.
[   50.154600] irq event stamp: 400463
[   50.159566] hardirqs last  enabled at (400463): [<ffffffff8094edc8>] _raw_spin_unlock_irqrestore+0x40/0xa8
[   50.171981] hardirqs last disabled at (400462): [<ffffffff8094eb98>] _raw_spin_lock_irqsave+0x30/0xb0
[   50.183897] softirqs last  enabled at (400450): [<ffffffff8016580c>] __do_softirq+0x4ac/0x6a8
[   50.195015] softirqs last disabled at (400425): [<ffffffff80165e78>] irq_exit+0x110/0x128

Fix this by using the TRACE_IRQS_OFF macro to call trace_hardirqs_off()
when CONFIG_TRACE_IRQFLAGS is enabled. This is done before invoking
schedule() following the work_resched label because:

 1) Interrupts are disabled regardless of the path we take to reach
    work_resched() & schedule().

 2) Performing the tracing here avoids the need to do it in paths which
    disable interrupts but don't call out to C code before hitting a
    path which uses the RESTORE_SOME macro that will call
    trace_hardirqs_on() or trace_hardirqs_off() as appropriate.

We call trace_hardirqs_on() using the TRACE_IRQS_ON macro before calling
syscall_trace_leave() for similar reasons, ensuring that lockdep has a
consistent view of state after we re-enable interrupts.
Signed-off-by: default avatarPaul Burton <paul.burton@imgtec.com>
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Cc: linux-mips@linux-mips.org
Cc: stable <stable@vger.kernel.org>
Patchwork: https://patchwork.linux-mips.org/patch/15385/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
      d8550860
    • Paul Burton's avatar
      MIPS: pm-cps: Drop manual cache-line alignment of ready_count · 161c51cc
      Paul Burton authored 
      We allocate memory for a ready_count variable per-CPU, which is accessed
via a cached non-coherent TLB mapping to perform synchronisation between
threads within the core using LL/SC instructions. In order to ensure
that the variable is contained within its own data cache line we
allocate 2 lines worth of memory & align the resulting pointer to a line
boundary. This is however unnecessary, since kmalloc is guaranteed to
return memory which is at least cache-line aligned (see
ARCH_DMA_MINALIGN). Stop the redundant manual alignment.

Besides cleaning up the code & avoiding needless work, this has the side
effect of avoiding an arithmetic error found by Bryan on 64 bit systems
due to the 32 bit size of the former dlinesz. This led the ready_count
variable to have its upper 32b cleared erroneously for MIPS64 kernels,
causing problems when ready_count was later used on MIPS64 via cpuidle.
Signed-off-by: default avatarPaul Burton <paul.burton@imgtec.com>
Fixes: 3179d37e ("MIPS: pm-cps: add PM state entry code for CPS systems")
Reported-by: default avatarBryan O'Donoghue <bryan.odonoghue@imgtec.com>
Reviewed-by: default avatarBryan O'Donoghue <bryan.odonoghue@imgtec.com>
Tested-by: default avatarBryan O'Donoghue <bryan.odonoghue@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: stable <stable@vger.kernel.org> # v3.16+
Patchwork: https://patchwork.linux-mips.org/patch/15383/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
      161c51cc
  3. 28 Jun, 2017 1 commit
  5. 27 Jun, 2017 1 commit
  7. 26 Jun, 2017 1 commit
  9. 25 Jun, 2017 6 commits
  11. 24 Jun, 2017 11 commits
  13. 23 Jun, 2017 15 commits
  15. 22 Jun, 2017 1 commit
    • Randy Dunlap's avatar
      kconfig: fix sparse warnings in nconfig · ad818106
      Randy Dunlap authored 
      Fix sparse warnings in scripts/kconfig/nconf* ('make nconfig'):

../scripts/kconfig/nconf.c:1071:32: warning: Using plain integer as NULL pointer
../scripts/kconfig/nconf.c:1238:30: warning: Using plain integer as NULL pointer
../scripts/kconfig/nconf.c:511:51: warning: Using plain integer as NULL pointer
../scripts/kconfig/nconf.c:1460:6: warning: symbol 'setup_windows' was not declared. Should it be static?
../scripts/kconfig/nconf.c:274:12: warning: symbol 'current_instructions' was not declared. Should it be static?
../scripts/kconfig/nconf.c:308:22: warning: symbol 'function_keys' was not declared. Should it be static?
../scripts/kconfig/nconf.gui.c:132:17: warning: non-ANSI function declaration of function 'set_colors'
../scripts/kconfig/nconf.gui.c:195:24: warning: Using plain integer as NULL pointer

nconf.gui.o before/after files are the same.
nconf.o before/after files are the same until the 'static' function
declarations are added.
Signed-off-by: default avatarRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
      ad818106
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