linux-stable.git/arch/powerpc/kernel/process.c, branch v3.9.7

powerpc: Fix stack overflow crash in resume_kernel when ftracing

2013-06-20T19:01:32+00:00

commit 0e37739b1c96d65e6433998454985de994383019 upstream.

It's possible for us to crash when running with ftrace enabled, eg:

  Bad kernel stack pointer bffffd12 at c00000000000a454
  cpu 0x3: Vector: 300 (Data Access) at [c00000000ffe3d40]
      pc: c00000000000a454: resume_kernel+0x34/0x60
      lr: c00000000000335c: performance_monitor_common+0x15c/0x180
      sp: bffffd12
     msr: 8000000000001032
     dar: bffffd12
   dsisr: 42000000

If we look at current's stack (paca->__current->stack) we see it is
equal to c0000002ecab0000. Our stack is 16K, and comparing to
paca->kstack (c0000002ecab3e30) we can see that we have overflowed our
kernel stack. This leads to us writing over our struct thread_info, and
in this case we have corrupted thread_info->flags and set
_TIF_EMULATE_STACK_STORE.

Dumping the stack we see:

  3:mon> t c0000002ecab0000
  [c0000002ecab0000] c00000000002131c .performance_monitor_exception+0x5c/0x70
  [c0000002ecab0080] c00000000000335c performance_monitor_common+0x15c/0x180
  --- Exception: f01 (Performance Monitor) at c0000000000fb2ec .trace_hardirqs_off+0x1c/0x30
  [c0000002ecab0370] c00000000016fdb0 .trace_graph_entry+0xb0/0x280 (unreliable)
  [c0000002ecab0410] c00000000003d038 .prepare_ftrace_return+0x98/0x130
  [c0000002ecab04b0] c00000000000a920 .ftrace_graph_caller+0x14/0x28
  [c0000002ecab0520] c0000000000d6b58 .idle_cpu+0x18/0x90
  [c0000002ecab05a0] c00000000000a934 .return_to_handler+0x0/0x34
  [c0000002ecab0620] c00000000001e660 .timer_interrupt+0x160/0x300
  [c0000002ecab06d0] c0000000000025dc decrementer_common+0x15c/0x180
  --- Exception: 901 (Decrementer) at c0000000000104d4 .arch_local_irq_restore+0x74/0xa0
  [c0000002ecab09c0] c0000000000fe044 .trace_hardirqs_on+0x14/0x30 (unreliable)
  [c0000002ecab0fb0] c00000000016fe3c .trace_graph_entry+0x13c/0x280
  [c0000002ecab1050] c00000000003d038 .prepare_ftrace_return+0x98/0x130
  [c0000002ecab10f0] c00000000000a920 .ftrace_graph_caller+0x14/0x28
  [c0000002ecab1160] c0000000000161f0 .__ppc64_runlatch_on+0x10/0x40
  [c0000002ecab11d0] c00000000000a934 .return_to_handler+0x0/0x34
  --- Exception: 901 (Decrementer) at c0000000000104d4 .arch_local_irq_restore+0x74/0xa0

  ... and so on

__ppc64_runlatch_on() is called from RUNLATCH_ON in the exception entry
path. At that point the irq state is not consistent, ie. interrupts are
hard disabled (by the exception entry), but the paca soft-enabled flag
may be out of sync.

This leads to the local_irq_restore() in trace_graph_entry() actually
enabling interrupts, which we do not want. Because we have not yet
reprogrammed the decrementer we immediately take another decrementer
exception, and recurse.

The fix is twofold. Firstly make sure we call DISABLE_INTS before
calling RUNLATCH_ON. The badly named DISABLE_INTS actually reconciles
the irq state in the paca with the hardware, making it safe again to
call local_irq_save/restore().

Although that should be sufficient to fix the bug, we also mark the
runlatch routines as notrace. They are called very early in the
exception entry and we are asking for trouble tracing them. They are
also fairly uninteresting and tracing them just adds unnecessary
overhead.

[ This regression was introduced by fe1952fc0afb9a2e4c79f103c08aef5d13db1873
  "powerpc: Rework runlatch code" by myself --BenH
]

Signed-off-by: Michael Ellerman 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc/hw_breakpoints: Add DABRX cpu feature to fix 32-bit regression

2013-06-13T17:49:28+00:00

commit 82a9f16adc12f51c3f8ea59a7c3c120241aff836 upstream.

When introducing support for DABRX in 4474ef0, we broke older 32-bit CPUs
that don't have that register.

Some CPUs have a DABR but not DABRX.  Configuration are:
- No 32bit CPUs have DABRX but some have DABR.
- POWER4+ and below have the DABR but no DABRX.
- 970 and POWER5 and above have DABR and DABRX.
- POWER8 has DAWR, hence no DABRX.

This introduces CPU_FTR_DABRX and sets it on appropriate CPUs.  We use
the top 64 bits for CPU FTR bits since only 64 bit CPUs have this.

Processors that don't have the DABRX will still work as they will fall
back to software filtering these breakpoints via perf_exclude_event().

Signed-off-by: Michael Neuling 
Reported-by: "Gorelik, Jacob (335F)" 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc: fix compiling CONFIG_PPC_TRANSACTIONAL_MEM when CONFIG_ALTIVEC=n

2013-04-09T22:14:39+00:00

We can't compile a kernel with CONFIG_ALTIVEC=n when
CONFIG_PPC_TRANSACTIONAL_MEM=y.  We currently get:

arch/powerpc/kernel/tm.S:320: Error: unsupported relocation against THREAD_VSCR
arch/powerpc/kernel/tm.S:323: Error: unsupported relocation against THREAD_VR0
arch/powerpc/kernel/tm.S:323: Error: unsupported relocation against THREAD_VR0
etc.

The below fixes this with a sprinkling of #ifdefs.

This was found by mpe with kisskb:
  http://kisskb.ellerman.id.au/kisskb/buildresult/8539442/

Signed-off-by: Michael Neuling 
Signed-off-by: Stephen Rothwell

powerpc: Hook in new transactional memory code

2013-02-15T06:02:23+00:00

This hooks the new transactional memory code into context switching, FP/VMX/VMX
unavailable and exception return.

Signed-off-by: Matt Evans 
Signed-off-by: Michael Neuling 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Add reclaim and recheckpoint functions for context switching transactional memory processes

2013-02-15T05:58:53+00:00

When we switch out a task, we need to save both the checkpointed and the
speculated state into the thread struct.

Similarly when we are switching in a task we need to load both the checkpointed
and speculated state.  If the task was using FP, we non-lazily reload both the
original and the speculative FP register states.  This is because the kernel
doesn't see if/when a TM rollback occurs, so if we take an FP unavoidable
later, we are unable to determine which set of FP regs need to be restored.

This simply adds these functions.  It doesn't hook them into the existing code
yet.

Signed-off-by: Matt Evans 
Signed-off-by: Michael Neuling 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Add transactional memory paca scratch register to show_regs

2013-02-15T05:58:51+00:00

Add transactional memory paca scratch register to show_regs.  This is useful
for debugging.

Signed-off-by: Matt Evans 
Signed-off-by: Michael Neuling 
Signed-off-by: Benjamin Herrenschmidt

powerpc: New macros for transactional memory support

2013-02-15T05:58:50+00:00

This adds new macros for saving and restoring checkpointed architected state
from and to the thread_struct.

It also adds some debugging macros for when your brain explodes trying to debug
your transactional memory enabled kernel.

Signed-off-by: Matt Evans 
Signed-off-by: Michael Neuling 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Add length setting to set_dawr

2013-01-29T00:35:07+00:00

Currently we set the length field in the DAWR to 0 which defaults it to one
double word (64bits) which is the same as the DABR.

Change this so that we can set it to longer values as supported by the DAWR.

Signed-off-by: Michael Neuling 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Rename set_break to avoid naming conflict

2013-01-15T18:25:47+00:00

With allmodconfig we are getting:
  drivers/tty/synclink_gt.c:160:12: error: conflicting types for 'set_break'
  arch/powerpc/include/asm/debug.h:49:5: note: previous declaration of 'set_break' was here

  drivers/tty/synclinkmp.c:526:12: error: conflicting types for 'set_break'
  arch/powerpc/include/asm/debug.h:49:5: note: previous declaration of 'set_break' was here

This renames set_break to set_breakpoint to avoid this naming conflict

Signed-off-by: Michael Neuling 
Reported-by: Fengguang Wu 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Add the DAWR support to the set_break()

2013-01-10T06:01:47+00:00

This adds DAWR supoprt to the set_break().

It does both bare metal and PAPR versions of setting the DAWR.

There is still some work we can do to make full use of the watchpoint but that
will come later.

Signed-off-by: Michael Neuling 
Signed-off-by: Benjamin Herrenschmidt