Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

In the hv-24x7 code there is a function memord() which tries to
implement a sort function return -1, 0, 1. However one of the
conditions is incorrect, such that it can never be true, because we
will have already returned.

I don't believe there is a bug in practice though, because the
comparisons are an optimisation prior to calling memcmp().

Fix it by swapping the second comparision, so it can be true.
Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Back in 2008 we added support for "fast little-endian switch" in the
syscall path. This added a special case syscall number 0x1ebe, which
is caught very early in the system call exception and switches endian
with as little overhead as possible. See commit 745a14cc
("[POWERPC] Add fast little-endian switch system call") for full
details.

Although it is fast, it's also completely non standard. The "syscall
number" is out of the range of normal syscalls, it can't be traced or
audited, and it's a bit of a wart. To the best of our knowledge it was
only used by one program, now long since discontinued.

So in an effort to shake out any current users, put it behind a config
option, and make it default n. If anyone *is* using it they can
quickly reinstate it with a rebuild, and we can flip it to default y.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

So we can #ifdef them in the next patch.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

When dumping the paca in xmon we currently show kstack. Although it's
not hard it's a bit fiddly to work out what the bounds of the kernel
stack should be based on the kstack value.

To make life easier and "kstack_base" which is the base (lowest
address) of the kernel stack, eg:

 kstack               = 0xc0000000f1a7be30      (0x258)
 kstack_base          = 0xc0000000f1a78000
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

i2c-dev provides an interface for userspace programs to interact with I2C
devices, and is very helpful for I2C-related debugging.

Enable it in pseries_defconfig and powernv_defconfig. It's already enabled
in many other powerpc defconfigs.
Signed-off-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

We call these functions with non-NULL mm or vma. Hence we can skip the
NULL check in these functions. We also remove now unused function
__local_flush_hugetlb_page().
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
[mpe: Drop the checks with is_vm_hugetlb_page() as noticed by Nick]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Currently xmon could call XIVE functions from OPAL even if the XIVE is
disabled or does not exist in the system, as in POWER8 machines. This
causes the following exception:

 1:mon> dx
 cpu 0x1: Vector: 700 (Program Check) at [c000000423c93450]
     pc: c00000000009cfa4: opal_xive_dump+0x50/0x68
     lr: c0000000000997b8: opal_return+0x0/0x50

This patch simply checks if XIVE is enabled before calling XIVE
functions.

Fixes: 243e2511 ("powerpc/xive: Native exploitation of the XIVE interrupt controller")
Suggested-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Access to PSL/XSL_DEBUG registers on the adapter provides easy access
to the debug facilities provided by PSL/XSL. So this patch adds two
new files (debug, xsl-debug) to the cxl-adapter specific debugfs
folder located at /sys/kernel/debugfs/cxl/card<n>, which will provide
direct r/w access to corrosponding debug registers in the adapter
config-space.
Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Unfortunately userspace can construct a sigcontext which enables
suspend. Thus userspace can force Linux into a path where trechkpt is
executed.

This patch blocks this from happening on POWER9 by sanity checking
sigcontexts passed in.

ptrace doesn't have this problem as only MSR SE and BE can be changed
via ptrace.

This patch also adds a number of WARN_ON()s in case we ever enter
suspend when we shouldn't. This should not happen, but if it does the
symptoms are soft lockup warnings which are not obviously TM related,
so the WARN_ON()s should make it obvious what's happening.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Some Power9 revisions can run in a mode where TM operates without
suspended state. If we find ourself on a CPU that might be in this
mode, we query OPAL to check, and if so we reenable TM in CPU
features, and enable a new user feature to signal to userspace that we
are in this mode.

We do not enable the "normal" user feature, PPC_FEATURE2_HTM, but we
do enable PPC_FEATURE2_HTM_NOSC because that indicates to userspace
that the kernel will abort transactions on syscall entry, which is
true regardless of the suspend mode.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Some CPUs can operate in a mode where TM (Transactional Memory) is
enabled but the suspended state of TM is disabled. In this mode
tsuspend does not enter suspended state, instead the transaction is
aborted. Similarly any other event that would lead to suspended state
instead aborts the transaction.

There is also an ABI change, in that in this mode processes are not
allowed to sigreturn with an MSR that would lead to suspended state,
Linux will instead return an error to the sigreturn syscall.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Currently the kernel relies on firmware to inform it whether or not the
CPU supports HTM and as long as the kernel was built with
CONFIG_PPC_TRANSACTIONAL_MEM=y then it will allow userspace to make
use of the facility.

There may be situations where it would be advantageous for the kernel
to not allow userspace to use HTM, currently the only way to achieve
this is to recompile the kernel with CONFIG_PPC_TRANSACTIONAL_MEM=n.

This patch adds a simple commandline option so that HTM can be
disabled at boot time.
Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
[mpe: Simplify to a bool, move to prom.c, put doco in the right place.
 Always disable, regardless of initial state, to avoid user confusion.]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Bring in some KVM commits we need (the TM one in particular).

Currently we use CPU_FTR_TM to decide if the CPU/kernel can support
TM (Transactional Memory), and if it's true we advertise that to
Qemu (or similar) via KVM_CAP_PPC_HTM.

PPC_FEATURE2_HTM is the user-visible feature bit, which indicates that
the CPU and kernel can support TM. Currently CPU_FTR_TM and
PPC_FEATURE2_HTM always have the same value, either true or false, so
using the former for KVM_CAP_PPC_HTM is correct.

However some Power9 CPUs can operate in a mode where TM is enabled but
TM suspended state is disabled. In this mode CPU_FTR_TM is true, but
PPC_FEATURE2_HTM is false. Instead a different PPC_FEATURE2 bit is
set, to indicate that this different mode of TM is available.

It is not safe to let guests use TM as-is, when the CPU is in this
mode. So to prevent that from happening, use PPC_FEATURE2_HTM to
determine the value of KVM_CAP_PPC_HTM.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

This reverts commit 94a04bc2.

In order to run HPT guests on a radix POWER9 host, we will have to run
the host in single-threaded mode, because POWER9 processors do not
currently support running some threads of a core in HPT mode while
others are in radix mode ("mixed mode").

That means that we will need the same mechanisms that are used on
POWER8 to make the secondary threads available to KVM, which were
disabled on POWER9 by commit 94a04bc2.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

powerpc/vphn: On Power systems with shared configurations of CPUs
and memory, there are some issues with the association of additional
CPUs and memory to nodes when hot-adding resources.  This patch
fixes an end-of-updates processing problem observed occasionally
in numa_update_cpu_topology().
Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

powerpc/hotplug: On Power systems with shared configurations of CPUs
and memory, there are some issues with the association of additional
CPUs and memory to nodes when hot-adding resources.  During hotplug
CPU operations, this patch resets the timer on topology update work
function to a small value to better ensure that the CPU topology is
detected and configured sooner.
Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

powerpc/vphn: On Power systems with shared configurations of CPUs
and memory, there are some issues with the association of additional
CPUs and memory to nodes when hot-adding resources.  This patch
updates the initialization checks to independently recognize PRRN
or VPHN support.
Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

powerpc/vphn: On Power systems with shared configurations of CPUs
and memory, there are some issues with the association of additional
CPUs and memory to nodes when hot-adding resources.  This patch
corrects the currently broken capability to set the topology for
shared CPUs in LPARs.  At boot time for shared CPU lpars, the
topology for each CPU was being set to node zero.  Now when
numa_update_cpu_topology() is called appropriately, the Virtual
Processor Home Node (VPHN) capabilities information provided by the
pHyp allows the appropriate node in the shared configuration to be
selected for the CPU.
Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

If we are in user space and hit a UE error, we now have the
basic infrastructure to walk the page tables and find out
the effective address that was accessed, since the DAR
is not valid.

We use a work_queue content to hookup the bad pfn, any
other context causes problems, since memory_failure itself
can call into schedule() via lru_drain_ bits.

We could probably poison the struct page to avoid a race
between detection and taking corrective action.
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Hookup instruction errors (UE) for memory offling via memory_failure()
in a manner similar to load/store errors (derror). Since we have access
to the NIP, the conversion is a one step process in this case.
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Extract physical_address for UE errors by walking the page
tables for the mm and address at the NIP, to extract the
instruction. Then use the instruction to find the effective
address via analyse_instr().

We might have page table walking races, but we expect them to
be rare, the physical address extraction is best effort. The idea
is to then hook up this infrastructure to memory failure eventually.
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Use the same alignment as Effective address.
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

There are no users of get_mce_fault_addr() since commit
1363875b ("powerpc/64s: fix handling of non-synchronous machine
checks") removed the last usage.
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Use WARN_ON(), while running out of stubs in stub_for_addr()
and abort loading of the module instead of BUG_ON().
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

For PSL9 currently we aren't dumping the PSL FIR register when a
PSL error interrupt is triggered. Contents of this register are useful
in debugging AFU issues.

This patch fixes issue by adding a new service_layer_ops callback
cxl_native_err_irq_dump_regs_psl9() to dump the PSL_FIR registers on a
PSL error interrupt thereby bringing the behavior in line with PSL on
POWER-8. Also the existing service_layer_ops callback
for PSL8 has been renamed to cxl_native_err_irq_dump_regs_psl8().
Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Turns out pthreads returns an errno and doesn't set errno. This doesn't
play well with perror().
Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

PSL9 doesn't have a FIR2 register as was the case with PSL8. However
currently the register definitions in 'cxl.h' have a definition for
PSL9_FIR2 that actually points to PSL9_FIR_MASK register in the P1
area at offset 0x308.

So this patch renames the def PSL9_FIR2 to PSL9_FIR_MASK and updates
the references in the code to point to the new identifier. It also
removes the code to dump contents of FIR2 (FIR_MASK actually) in
cxl_native_irq_dump_regs_psl9().

Fixes: f24be42a ("cxl: Add psl9 specific code")
Reported-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

The PSL initialization sequence has been updated to DD2.
This patch adapts to the changes, retaining compatibility with DD1.
The patch includes some changes to DD1 fix-ups as well.

Tests performed on some of the old/new hardware.

The function is_page_fault(), for POWER9, lists the Translation Checkout
Responses where the page fault will be handled by copro_handle_mm_fault().
This list is too restrictive and not necessary.

This patches removes this restriction and all page faults, whatever the
reason, will be handled. In this case, the interruption is always
acknowledged.

The following features will be added soon:
- phb reset when switching to capi mode.
- cxllib update to support new functions.
Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Reviewed-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Add a check for p->state == TASK_RUNNING so that any wake-ups on
task_struct p in the interim lead to 0 being returned by get_wchan().
Signed-off-by: Kautuk Consul <kautuk.consul.1980@gmail.com>
[mpe: Confirmed other architectures do similar]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Currently sprintf is used, and while paths should never exceed
the size of the buffer it is theoretically possible since
dirent.d_name is 256 bytes. As a result this trips
-Wformat-overflow, and since the test is built with -Wall -Werror
the causes the build to fail. Switch to using snprintf and skip
any paths which are too long for the filename buffer.
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Several callers to epapr_hypercall() pass an uninitialized stack
allocated array for the input arguments, presumably because they
have no input arguments. However this can produce errors like
this one

 arch/powerpc/include/asm/epapr_hcalls.h:470:42: error: 'in' may be used uninitialized in this function [-Werror=maybe-uninitialized]
  unsigned long register r3 asm("r3") = in[0];
                                        ~~^~~

Fix callers to this function to always zero-initialize the input
arguments array to prevent this.
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

This is useful, especially for developers.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

It might be useful to quickly get the uptime of a running system on
xmon, without needing to grab data from memory and doing math on
struct addresses.

For example, it'd be useful to check for how long after a crash a
system is on xmon shell or if some test was started after the first
test crashed (and this 2nd test crashed too into xmon).

This small patch adds the 'U' command, to accomplish this.
Suggested-by: Murilo Fossa Vicentini <muvic@linux.vnet.ibm.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com>
[mpe: Display units (seconds), add sync()/__delay() sequence]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

In opal_event_shutdown() we free all the IRQs hanging off the
opal_event_irqchip. However it's not safe to do so if we're called
from IRQ context, because free_irq() wants to synchronise versus IRQ
context. This can lead to warnings and a stuck system.

For example from sysrq-b:

  Trying to free IRQ 17 from IRQ context!
  ------------[ cut here ]------------
  WARNING: CPU: 0 PID: 0 at kernel/irq/manage.c:1461 __free_irq+0x398/0x8d0
  ...
  NIP __free_irq+0x398/0x8d0
  LR __free_irq+0x394/0x8d0
  Call Trace:
    __free_irq+0x394/0x8d0 (unreliable)
    free_irq+0xa4/0x140
    opal_event_shutdown+0x128/0x180
    opal_shutdown+0x1c/0xb0
    pnv_shutdown+0x20/0x40
    machine_restart+0x38/0x90
    emergency_restart+0x28/0x40
    sysrq_handle_reboot+0x24/0x40
    __handle_sysrq+0x198/0x590
    hvc_poll+0x48c/0x8c0
    hvc_handle_interrupt+0x1c/0x50
    __handle_irq_event_percpu+0xe8/0x6e0
    handle_irq_event_percpu+0x34/0xe0
    handle_irq_event+0xc4/0x210
    handle_level_irq+0x250/0x770
    generic_handle_irq+0x5c/0xa0
    opal_handle_events+0x11c/0x240
    opal_interrupt+0x38/0x50
    __handle_irq_event_percpu+0xe8/0x6e0
    handle_irq_event_percpu+0x34/0xe0
    handle_irq_event+0xc4/0x210
    handle_fasteoi_irq+0x174/0xa10
    generic_handle_irq+0x5c/0xa0
    __do_irq+0xbc/0x4e0
    call_do_irq+0x14/0x24
    do_IRQ+0x18c/0x540
    hardware_interrupt_common+0x158/0x180

We can avoid that by using disable_irq_nosync() rather than
free_irq(). Although it doesn't fully free the IRQ, it should be
sufficient when we're shutting down, particularly in an emergency.

Add an in_interrupt() check and use free_irq() when we're shutting
down normally. It's probably OK to use disable_irq_nosync() in that
case too, but for now it's safer to leave that behaviour as-is.

Fixes: 9f0fd049 ("powerpc/powernv: Add a virtual irqchip for opal events")
Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Fix a circa 2005 FIXME by implementing a check to ensure that we
actually got into the jprobe break handler() due to the trap in
jprobe_return().
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

KPROBES_SANITY_TEST throws the below splat when CONFIG_PREEMPT is
enabled:

  Kprobe smoke test: started
  DEBUG_LOCKS_WARN_ON(val > preempt_count())
  ------------[ cut here ]------------
  WARNING: CPU: 19 PID: 1 at kernel/sched/core.c:3094 preempt_count_sub+0xcc/0x140
  Modules linked in:
  CPU: 19 PID: 1 Comm: swapper/0 Not tainted 4.13.0-rc7-nnr+ #97
  task: c0000000fea80000 task.stack: c0000000feb00000
  NIP:  c00000000011d3dc LR: c00000000011d3d8 CTR: c000000000a090d0
  REGS: c0000000feb03400 TRAP: 0700   Not tainted  (4.13.0-rc7-nnr+)
  MSR:  8000000000021033 <SF,ME,IR,DR,RI,LE>  CR: 28000282  XER: 00000000
  CFAR: c00000000015aa18 SOFTE: 0
  <snip>
  NIP preempt_count_sub+0xcc/0x140
  LR  preempt_count_sub+0xc8/0x140
  Call Trace:
    preempt_count_sub+0xc8/0x140 (unreliable)
    kprobe_handler+0x228/0x4b0
    program_check_exception+0x58/0x3b0
    program_check_common+0x16c/0x170
    --- interrupt: 0 at kprobe_target+0x8/0x20
                     LR = init_test_probes+0x248/0x7d0
    kp+0x0/0x80 (unreliable)
    livepatch_handler+0x38/0x74
    init_kprobes+0x1d8/0x208
    do_one_initcall+0x68/0x1d0
    kernel_init_freeable+0x298/0x374
    kernel_init+0x24/0x160
    ret_from_kernel_thread+0x5c/0x70
  Instruction dump:
  419effdc 3d22001b 39299240 81290000 2f890000 409effc8 3c82ffcb 3c62ffcb
  3884bc68 3863bc18 4803d5fd 60000000 <0fe00000> 4bffffa8 60000000 60000000
  ---[ end trace 432dd46b4ce3d29f ]---
  Kprobe smoke test: passed successfully

The issue is that we aren't disabling preemption in
kprobe_ftrace_handler(). Disable it.

Fixes: ead514d5 ("powerpc/kprobes: Add support for KPROBES_ON_FTRACE")
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
[mpe: Trim oops a little for formatting]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Kamalesh pointed out that we are getting the below call traces with
livepatched functions when we enable CONFIG_PREEMPT:

[  495.470721] BUG: using __this_cpu_read() in preemptible [00000000] code: cat/8394
[  495.471167] caller is is_current_kprobe_addr+0x30/0x90
[  495.471171] CPU: 4 PID: 8394 Comm: cat Tainted: G              K 4.13.0-rc7-nnr+ #95
[  495.471173] Call Trace:
[  495.471178] [c00000008fd9b960] [c0000000009f039c] dump_stack+0xec/0x160 (unreliable)
[  495.471184] [c00000008fd9b9a0] [c00000000059169c] check_preemption_disabled+0x15c/0x170
[  495.471187] [c00000008fd9ba30] [c000000000046460] is_current_kprobe_addr+0x30/0x90
[  495.471191] [c00000008fd9ba60] [c00000000004e9a0] ftrace_call+0x1c/0xb8
[  495.471195] [c00000008fd9bc30] [c000000000376fd8] seq_read+0x238/0x5c0
[  495.471199] [c00000008fd9bcd0] [c0000000003cfd78] proc_reg_read+0x88/0xd0
[  495.471203] [c00000008fd9bd00] [c00000000033e5d4] __vfs_read+0x44/0x1b0
[  495.471206] [c00000008fd9bd90] [c0000000003402ec] vfs_read+0xbc/0x1b0
[  495.471210] [c00000008fd9bde0] [c000000000342138] SyS_read+0x68/0x110
[  495.471214] [c00000008fd9be30] [c00000000000bc6c] system_call+0x58/0x6c

Commit c05b8c44 ("powerpc/kprobes: Skip livepatch_handler() for
jprobes") introduced a helper is_current_kprobe_addr() to help determine
if the current function has been livepatched or if it has a jprobe
installed, both of which modify the NIP. This was subsequently renamed
to __is_active_jprobe().

In the case of a jprobe, kprobe_ftrace_handler() disables pre-emption
before calling into setjmp_pre_handler() which returns without disabling
pre-emption. This is done to ensure that the jprobe handler won't
disappear beneath us if the jprobe is unregistered between the
setjmp_pre_handler() and the subsequent longjmp_break_handler() called
from the jprobe handler. Due to this, we can use __this_cpu_read() in
__is_active_jprobe() with the pre-emption check as we know that
pre-emption will be disabled.

However, if this function has been livepatched, we are still doing this
check and when we do so, pre-emption won't necessarily be disabled. This
results in the call trace shown above.

Fix this by only invoking __is_active_jprobe() when pre-emption is
disabled. And since we now guard this within a pre-emption check, we can
instead use raw_cpu_read() to get the current_kprobe value skipping the
check done by __this_cpu_read().

Fixes: c05b8c44 ("powerpc/kprobes: Skip livepatch_handler() for jprobes")
Reported-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Tested-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

In commit c05b8c44 ("powerpc/kprobes: Skip livepatch_handler() for
jprobes"), we added a helper is_current_kprobe_addr() to help detect if
the modified regs->nip was due to a jprobe or livepatch. Masami felt
that the function name was not quite clear. To that end, this patch
renames is_current_kprobe_addr() to __is_active_jprobe() and adds a
comment to (hopefully) better clarify the purpose of this helper. The
helper has also now been moved to kprobes-ftrace.c so that it is only
available for KPROBES_ON_FTRACE.
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>