powerpc: Add an in memory udbg console

This patch adds a new udbg early debug console which utilises
statically defined input and output buffers stored within the kernel
BSS. It is primarily designed to assist with bring up of new hardware
which may not have a working console but which has a method of
reading/writing kernel memory.

This version incorporates comments made by Ben H (thanks!).

Changes from v1:
	- Add memory barriers.
	- Ensure updating of read/write positions is atomic.

Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc/powernv: Properly drop characters if console is closed

If the firmware returns an error such as "closed" (or hardware
error), we should drop characters.

Currently we only do that when a firmware compatible with OPAL v2
APIs is detected, in the code that calls opal_console_write_buffer_space(),
which didn't exist with OPAL v1 (or didn't work).

However, when enabling early debug consoles, the flag indicating
that v2 is supported isn't set yet, causing us, in case of errors
or closed console, to spin forever.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc/powernv: Improve kexec reliability

We add a machine_shutdown hook that frees the OPAL interrupts
(so they get masked at the source and don't fire while kexec'ing)
and which triggers an IODA reset on all the PCIe host bridges
which will have the effect of blocking all DMAs and subsequent
PCIs interrupts.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: hard_irq_disable(): Call trace_hardirqs_off after disabling

lockdep.c has this:
        /*
         * So we're supposed to get called after you mask local IRQs,
         * but for some reason the hardware doesn't quite think you did
         * a proper job.
         */
	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
		return;

Since irqs_disabled() is based on soft_enabled(), that (not just the
hard EE bit) needs to be 0 before we call trace_hardirqs_off.

Signed-off-by: Scott Wood <scottwood@freescale.com>
powerpc/mm: Use the correct mask value when looking at pgtable address

Our pgtable are 2*sizeof(pte_t)*PTRS_PER_PTE which is PTE_FRAG_SIZE.
Instead of depending on frag size, mask with PMD_MASKED_BITS.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: Fix build errors STRICT_MM_TYPECHECKS

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc/kexec: Fix kexec when using VMX optimised memcpy

commit b3f271e86e5a (powerpc: POWER7 optimised memcpy using VMX and
enhanced prefetch) uses VMX when it is safe to do so (ie not in
interrupt). It also looks at the task struct to decide if we have to
save the current tasks' VMX state.

kexec calls memcpy() at a point where the task struct may have been
overwritten by the new kexec segments. If it has been overwritten
then when memcpy -> enable_altivec looks up current->thread.regs->msr
we get a cryptic oops or lockup.

I also notice we aren't initialising thread_info->cpu, which means
smp_processor_id is broken. Fix that too.

Signed-off-by: Anton Blanchard <anton@samba.org>
Cc: <stable@vger.kernel.org> # 3.6+
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc/rtas_flash: Fix validate_flash buffer overflow issue

ibm,validate-flash-image RTAS call output buffer contains 150 - 200
bytes of data on latest system. Presently we have output
buffer size as 64 bytes and we use sprintf to copy data from
RTAS buffer to local buffer. This causes kernel oops (see below
call trace).

This patch increases local buffer size to 256 and also uses
snprintf instead of sprintf to copy data from RTAS buffer.

Kernel call trace :
-------------------
Oops: Kernel access of bad area, sig: 11 [#1]
SMP NR_CPUS=1024 NUMA pSeries
Modules linked in: nfs fscache lockd auth_rpcgss nfs_acl sunrpc fuse loop dm_mod ipv6 ipv6_lib usb_storage ehea(X) sr_mod qlge ses cdrom enclosure st be2net sg ext3 jbd mbcache usbhid hid ohci_hcd ehci_hcd usbcore qla2xxx usb_common sd_mod crc_t10dif scsi_dh_hp_sw scsi_dh_rdac scsi_dh_alua scsi_dh_emc scsi_dh lpfc scsi_transport_fc scsi_tgt ipr(X) libata scsi_mod
Supported: Yes
NIP: 4520323031333130 LR: 4520323031333130 CTR: 0000000000000000
REGS: c0000001b91779b0 TRAP: 0400   Tainted: G            X  (3.0.13-0.27-ppc64)
MSR: 8000000040009032 <EE,ME,IR,DR>  CR: 44022488  XER: 20000018
TASK = c0000001bca1aba0[4736] 'cat' THREAD: c0000001b9174000 CPU: 36
GPR00: 4520323031333130 c0000001b9177c30 c000000000f87c98 000000000000009b
GPR04: c0000001b9177c4a 000000000000000b 3520323031333130 2032303133313031
GPR08: 3133313031350a4d 000000000000009b 0000000000000000 c0000000003664a4
GPR12: 0000000022022448 c000000003ee6c00 0000000000000002 00000000100e8a90
GPR16: 00000000100cb9d8 0000000010093370 000000001001d310 0000000000000000
GPR20: 0000000000008000 00000000100fae60 000000000000005e 0000000000000000
GPR24: 0000000010129350 46573738302e3030 2046573738302e30 300a4d4720323031
GPR28: 333130313520554e 4b4e4f574e0a4d47 2032303133313031 3520323031333130
NIP [4520323031333130] 0x4520323031333130
LR [4520323031333130] 0x4520323031333130
Call Trace:
[c0000001b9177c30] [4520323031333130] 0x4520323031333130 (unreliable)
Instruction dump:
XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX

Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: Bring all threads online prior to migration/hibernation

This patch brings online all threads which are present but not online
prior to migration/hibernation.  After migration/hibernation those
threads are taken back offline.

During migration/hibernation all online CPUs must call H_JOIN, this is
required by the hypervisor.  Without this patch, threads that are offline
(H_CEDE'd) will not be woken to make the H_JOIN call and the OS will be
deadlocked (all threads either JOIN'd or CEDE'd).

Cc: <stable@kernel.org>
Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: Make CONFIG_RTAS_PROC depend on CONFIG_PROC_FS

We are getting build errors with CONFIG_PROC_FS=n:

arch/powerpc/kernel/rtas_flash.c
   In function 'rtas_flash_init':
  745:33: error: unused variable 'f' [-Werror=unused-variable]

But rtas_flash.c should not be built when CONFIG_PROC_FS=n, beacause all
it does is provide a /proc interface to the RTAS flash routines.

CONFIG_RTAS_FLASH already depends on CONFIG_RTAS_PROC, to indicate that
it depends on the RTAS proc support, but CONFIG_RTAS_PROC does not
depend on CONFIG_PROC_FS. So fix that.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: Fix MAX_STACK_TRACE_ENTRIES too low warning again

Saw this warning again, and this time from the ret_from_fork path.

It seems we could clear the back chain earlier in copy_thread(), which
could cover both path, and also fix potential lockdep usage in
schedule_tail(), or exception occurred before we clear the back chain.

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc/powernv: Detect OPAL v3 API version

Future firmwares will support that new version

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc/powernv: Fix starting of secondary CPUs on OPALv2 and v3

The current code fails to handle kexec on OPALv2. This fixes it
and adds code to improve the situation on OPALv3 where we can
query the CPU status from the firmware and decide what to do
based on that.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: Provide __bswapdi2

Some versions of GCC apparently expect this to be provided by libgcc.

Updates from Mikey to fix 32 bit version and adding "r" to registers.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: Fix irq_set_affinity() return values

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc/booke64: Fix kernel hangs at kernel_dbg_exc

MSR_DE is not cleared on entry to the kernel, and we don't clear it
explicitly outside of debug code.  If we have MSR_DE set in
prime_debug_regs(), and the new thread has events enabled in DBCR0
(e.g.  ICMP is set in thread->dbsr0, even though it was cleared in the
real DBCR0 when the thread got scheduled out), we'll end up taking a
debug exception in the kernel when DBCR0 is loaded.  DSRR0 will not
point to an exception vector, and the kernel ends up hanging at
kernel_dbg_exc.  Fix this by always clearing MSR_DE when we load new
debug state.

Another observed source of kernel_dbg_exc hangs is with the branch
taken event.  If this event is active, but we take a non-debug trap
(e.g. a TLB miss or an asynchronous interrupt) before the next branch.
We end up taking a branch-taken debug exception on the initial branch
instruction of the exception vector, but because the debug exception is
DBSR_BT rather than DBSR_IC we branch to kernel_dbg_exc before even
checking the DSRR0 address.  Fix this by checking for DBSR_BT as well
as DBSR_IC, which is what 32-bit does and what the comments suggest was
intended in the 64-bit code as well.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: Syscall hooks for context tracking subsystem

This is the syscall slow path hooks for context tracking subsystem,
corresponding to
[PATCH] x86: Syscall hooks for userspace RCU extended QS
  commit bf5a3c13b939813d28ce26c01425054c740d6731

TIF_MEMDIE is moved to the second 16-bits (with value 17), as it seems there
is no asm code using it. TIF_NOHZ is added to _TIF_SYCALL_T_OR_A, so it is
better for it to be in the same 16 bits with others in the group, so in the
asm code, andi. with this group could work.

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: Exception hooks for context tracking subsystem

This is the exception hooks for context tracking subsystem, including
data access, program check, single step, instruction breakpoint, machine check,
alignment, fp unavailable, altivec assist, unknown exception, whose handlers
might use RCU.

This patch corresponds to
[PATCH] x86: Exception hooks for userspace RCU extended QS
  commit 6ba3c97a38803883c2eee489505796cb0a727122

But after the exception handling moved to generic code, and some changes in
following two commits:
56dd9470d7c8734f055da2a6bac553caf4a468eb
  context_tracking: Move exception handling to generic code
6c1e0256fad84a843d915414e4b5973b7443d48d
  context_tracking: Restore correct previous context state on exception exit

it is able for exception hooks to use the generic code above instead of a
redundant arch implementation.

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: Exit user context on notify resume

This patch allows RCU usage in do_notify_resume, e.g. signal handling.
It corresponds to
[PATCH] x86: Exit RCU extended QS on notify resume
  commit edf55fda35c7dc7f2d9241c3abaddaf759b457c6

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
powerpc: Use the new schedule_user API on userspace preemption

This patch corresponds to
[PATCH] x86: Use the new schedule_user API on userspace preemption
  commit 0430499ce9d78691f3985962021b16bf8f8a8048

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>