linux.git/arch/powerpc/kernel/process.c, branch v3.16.35

powerpc/tm: Check for already reclaimed tasks

2015-12-18T16:06:31+00:00

commit 7f821fc9c77a9b01fe7b1d6e72717b33d8d64142 upstream.

Currently we can hit a scenario where we'll tm_reclaim() twice.  This
results in a TM bad thing exception because the second reclaim occurs
when not in suspend mode.

The scenario in which this can happen is the following.  We attempt to
deliver a signal to userspace.  To do this we need obtain the stack
pointer to write the signal context.  To get this stack pointer we
must tm_reclaim() in case we need to use the checkpointed stack
pointer (see get_tm_stackpointer()).  Normally we'd then return
directly to userspace to deliver the signal without going through
__switch_to().

Unfortunatley, if at this point we get an error (such as a bad
userspace stack pointer), we need to exit the process.  The exit will
result in a __switch_to().  __switch_to() will attempt to save the
process state which results in another tm_reclaim().  This
tm_reclaim() now causes a TM Bad Thing exception as this state has
already been saved and the processor is no longer in TM suspend mode.
Whee!

This patch checks the state of the MSR to ensure we are TM suspended
before we attempt the tm_reclaim().  If we've already saved the state
away, we should no longer be in TM suspend mode.  This has the
additional advantage of checking for a potential TM Bad Thing
exception.

Found using syscall fuzzer.

Fixes: fb09692e71f1 ("powerpc: Add reclaim and recheckpoint functions for context switching transactional memory processes")
Signed-off-by: Michael Neuling 
Signed-off-by: Michael Ellerman 
Signed-off-by: Luis Henriques

powerpc: Correct DSCR during TM context switch

2014-06-11T07:02:56+00:00

Correct the DSCR SPR becoming temporarily corrupted if a task is
context switched during a transaction.

The problem occurs while suspending the task and is caused by saving
the DSCR to thread.dscr after it has already been set to the CPU's
default value:

__switch_to() calls __switch_to_tm()
	which calls tm_reclaim_task()
	which calls tm_reclaim_thread()
	which calls tm_reclaim()
		where the DSCR is set to the CPU's default
__switch_to() calls _switch()
		where thread.dscr is set to the DSCR

When the task is resumed, it's transaction will be doomed (as usual)
and the DSCR SPR will be corrupted, although the checkpointed value
will be correct. Therefore the DSCR will be immediately corrected by
the transaction aborting, unless it has been suspended. In that case
the incorrect value can be seen by the task until it resumes the
transaction.

The fix is to treat the DSCR similarly to the TAR and save it early
in __switch_to().

A program exposing the problem is added to the kernel self tests as:
tools/testing/selftests/powerpc/tm/tm-resched-dscr.

Signed-off-by: Sam Bobroff 
CC:  [v3.10+]
Signed-off-by: Benjamin Herrenschmidt

powerpc: Fix smp_processor_id() in preemptible splat in set_breakpoint

2014-05-20T00:54:06+00:00

Currently, on 8641D, which doesn't set CONFIG_HAVE_HW_BREAKPOINT
we get the following splat:

BUG: using smp_processor_id() in preemptible [00000000] code: login/1382
caller is set_breakpoint+0x1c/0xa0
CPU: 0 PID: 1382 Comm: login Not tainted 3.15.0-rc3-00041-g2aafe1a4d451 #1
Call Trace:
[decd5d80] [c0008dc4] show_stack+0x50/0x158 (unreliable)
[decd5dc0] [c03c6fa0] dump_stack+0x7c/0xdc
[decd5de0] [c01f8818] check_preemption_disabled+0xf4/0x104
[decd5e00] [c00086b8] set_breakpoint+0x1c/0xa0
[decd5e10] [c00d4530] flush_old_exec+0x2bc/0x588
[decd5e40] [c011c468] load_elf_binary+0x2ac/0x1164
[decd5ec0] [c00d35f8] search_binary_handler+0xc4/0x1f8
[decd5ef0] [c00d4ee8] do_execve+0x3d8/0x4b8
[decd5f40] [c001185c] ret_from_syscall+0x0/0x38
 --- Exception: c01 at 0xfeee554
    LR = 0xfeee7d4

The call path in this case is:

	flush_thread
	   --> set_debug_reg_defaults
	     --> set_breakpoint
	       --> __get_cpu_var

Since preemption is enabled in the cleanup of flush thread, and
there is no need to disable it, introduce the distinction between
set_breakpoint and __set_breakpoint, leaving only the flush_thread
instance as the current user of set_breakpoint.

Signed-off-by: Paul Gortmaker 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Drop return value from set_breakpoint as it is unused

2014-05-20T00:54:05+00:00

None of the callers check the return value, so it might as
well not have one at all.

Signed-off-by: Paul Gortmaker 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Fix kernel thread creation on ABIv2

2014-04-23T00:05:23+00:00

Change how we setup registers for ret_from_kernel_thread. In
ABIv1, instead of passing a function descriptor in, dereference
it and pass the target in directly.

Use ppc_global_function_entry to get it right on both ABIv1 and ABIv2.

Signed-off-by: Anton Blanchard

powerpc/tm: Disable IRQ in tm_recheckpoint

2014-04-07T00:33:13+00:00

We can't take an IRQ when we're about to do a trechkpt as our GPR state is set
to user GPR values.

We've hit this when running some IBM Java stress tests in the lab resulting in
the following dump:

  cpu 0x3f: Vector: 700 (Program Check) at [c000000007eb3d40]
      pc: c000000000050074: restore_gprs+0xc0/0x148
      lr: 00000000b52a8184
      sp: ac57d360
     msr: 8000000100201030
    current = 0xc00000002c500000
    paca    = 0xc000000007dbfc00     softe: 0     irq_happened: 0x00
      pid   = 34535, comm = Pooled Thread #
  R00 = 00000000b52a8184   R16 = 00000000b3e48fda
  R01 = 00000000ac57d360   R17 = 00000000ade79bd8
  R02 = 00000000ac586930   R18 = 000000000fac9bcc
  R03 = 00000000ade60000   R19 = 00000000ac57f930
  R04 = 00000000f6624918   R20 = 00000000ade79be8
  R05 = 00000000f663f238   R21 = 00000000ac218a54
  R06 = 0000000000000002   R22 = 000000000f956280
  R07 = 0000000000000008   R23 = 000000000000007e
  R08 = 000000000000000a   R24 = 000000000000000c
  R09 = 00000000b6e69160   R25 = 00000000b424cf00
  R10 = 0000000000000181   R26 = 00000000f66256d4
  R11 = 000000000f365ec0   R27 = 00000000b6fdcdd0
  R12 = 00000000f66400f0   R28 = 0000000000000001
  R13 = 00000000ada71900   R29 = 00000000ade5a300
  R14 = 00000000ac2185a8   R30 = 00000000f663f238
  R15 = 0000000000000004   R31 = 00000000f6624918
  pc  = c000000000050074 restore_gprs+0xc0/0x148
  cfar= c00000000004fe28 dont_restore_vec+0x1c/0x1a4
  lr  = 00000000b52a8184
  msr = 8000000100201030   cr  = 24804888
  ctr = 0000000000000000   xer = 0000000000000000   trap =  700

This moves tm_recheckpoint to a C function and moves the tm_restore_sprs into
that function.  It then adds IRQ disabling over the trechkpt critical section.
It also sets the TEXASR FS in the signals code to ensure this is never set now
that we explictly write the TM sprs in tm_recheckpoint.

Signed-off-by: Michael Neuling 
cc: stable@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt

powerpc/tm: Fix crash when forking inside a transaction

2014-03-07T02:50:15+00:00

When we fork/clone we currently don't copy any of the TM state to the new
thread.  This results in a TM bad thing (program check) when the new process is
switched in as the kernel does a tmrechkpt with TEXASR FS not set.  Also, since
R1 is from userspace, we trigger the bad kernel stack pointer detection.  So we
end up with something like this:

   Bad kernel stack pointer 0 at c0000000000404fc
   cpu 0x2: Vector: 700 (Program Check) at [c00000003ffefd40]
       pc: c0000000000404fc: restore_gprs+0xc0/0x148
       lr: 0000000000000000
       sp: 0
      msr: 9000000100201030
     current = 0xc000001dd1417c30
     paca    = 0xc00000000fe00800   softe: 0        irq_happened: 0x01
       pid   = 0, comm = swapper/2
   WARNING: exception is not recoverable, can't continue

The below fixes this by flushing the TM state before we copy the task_struct to
the clone.  To do this we go through the tmreclaim patch, which removes the
checkpointed registers from the CPU and transitions the CPU out of TM suspend
mode.  Hence we need to call tmrechkpt after to restore the checkpointed state
and the TM mode for the current task.

To make this fail from userspace is simply:
	tbegin
	li	r0, 2
	sc
	

Kudos to Adhemerval Zanella Neto for finding this.

Signed-off-by: Michael Neuling 
cc: Adhemerval Zanella Neto 
cc: stable@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt

powerpc: Fix hw breakpoints on !HAVE_HW_BREAKPOINT configurations

2014-01-29T05:58:47+00:00

This fixes a logic error that caused a failure to update the hw breakpoint
registers when not using the hw-breakpoint interface.

Signed-off-by: Andreas Schwab 
Signed-off-by: Benjamin Herrenschmidt

Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc

2014-01-28T05:11:26+00:00

Pull powerpc updates from Ben Herrenschmidt:
 "So here's my next branch for powerpc.  A bit late as I was on vacation
  last week.  It's mostly the same stuff that was in next already, I
  just added two patches today which are the wiring up of lockref for
  powerpc, which for some reason fell through the cracks last time and
  is trivial.

  The highlights are, in addition to a bunch of bug fixes:

   - Reworked Machine Check handling on kernels running without a
     hypervisor (or acting as a hypervisor).  Provides hooks to handle
     some errors in real mode such as TLB errors, handle SLB errors,
     etc...

   - Support for retrieving memory error information from the service
     processor on IBM servers running without a hypervisor and routing
     them to the memory poison infrastructure.

   - _PAGE_NUMA support on server processors

   - 32-bit BookE relocatable kernel support

   - FSL e6500 hardware tablewalk support

   - A bunch of new/revived board support

   - FSL e6500 deeper idle states and altivec powerdown support

  You'll notice a generic mm change here, it has been acked by the
  relevant authorities and is a pre-req for our _PAGE_NUMA support"

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc: (121 commits)
  powerpc: Implement arch_spin_is_locked() using arch_spin_value_unlocked()
  powerpc: Add support for the optimised lockref implementation
  powerpc/powernv: Call OPAL sync before kexec'ing
  powerpc/eeh: Escalate error on non-existing PE
  powerpc/eeh: Handle multiple EEH errors
  powerpc: Fix transactional FP/VMX/VSX unavailable handlers
  powerpc: Don't corrupt transactional state when using FP/VMX in kernel
  powerpc: Reclaim two unused thread_info flag bits
  powerpc: Fix races with irq_work
  Move precessing of MCE queued event out from syscall exit path.
  pseries/cpuidle: Remove redundant call to ppc64_runlatch_off() in cpu idle routines
  powerpc: Make add_system_ram_resources() __init
  powerpc: add SATA_MV to ppc64_defconfig
  powerpc/powernv: Increase candidate fw image size
  powerpc: Add debug checks to catch invalid cpu-to-node mappings
  powerpc: Fix the setup of CPU-to-Node mappings during CPU online
  powerpc/iommu: Don't detach device without IOMMU group
  powerpc/eeh: Hotplug improvement
  powerpc/eeh: Call opal_pci_reinit() on powernv for restoring config space
  powerpc/eeh: Add restore_config operation
  ...

Merge remote-tracking branch 'scott/next' into next

2014-01-15T03:22:35+00:00

Freescale updates from Scott:

<<
Highlights include 32-bit booke relocatable support, e6500 hardware
tablewalk support, various e500 SPE fixes, some new/revived boards, and
e6500 deeper idle and altivec powerdown modes.
>>