powerpc/watchpoints: Track perf single step directly on the breakpoint

There is a bug in the current watchpoint tracking logic, where the
teardown in arch_unregister_hw_breakpoint() uses bp->ctx->task, which it
does not have a reference of and parallel threads may be in the process
of destroying. This was partially addressed in commit fb822e6076d9
("powerpc/hw_breakpoint: Fix oops when destroying hw_breakpoint event"),
but the underlying issue of accessing a struct member in an unknown
state still remained. Syzkaller managed to trigger a null pointer
derefernce due to the race between the task destructor and checking the
pointer and dereferencing it in the loop.

While this null pointer dereference could be fixed by using READ_ONCE
to access the task up front, that just changes the error to manipulating
possbily freed memory.

Instead, the breakpoint logic needs to be reworked to remove any
dependency on a context or task struct during breakpoint removal.

The reason we have this currently is to clear thread.last_hit_ubp. This
member is used to differentiate the perf DAWR single-step sequence from
other causes of single-step, such as userspace just calling
ptrace(PTRACE_SINGLESTEP, ...). We need to differentiate them because,
when the single step interrupt is received, we need to know whether to
re-insert the DAWR breakpoint (perf) or not (ptrace / other).

arch_unregister_hw_breakpoint() needs to clear this information to
prevent dangling pointers to possibly freed memory. These pointers are
dereferenced in single_step_dabr_instruction() without a way to check
their validity.

This patch moves the tracking of this information to the breakpoint
itself. This means we no longer have to do anything special to clean up.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230801011744.153973-4-bgray@linux.ibm.com

powerpc/inst: Move ppc_inst_t definition in asm/reg.h

Because of circular inclusion of asm/hw_breakpoint.h, we
need to move definition of asm/reg.h outside of inst.h
so that asm/hw_breakpoint.h gets it without including
asm/inst.h

Also remove asm/inst.h from asm/uprobes.h as it's not
needed anymore.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/4b79f1491118af96b1ac0735e74aeca02ea4c04e.1638208156.git.christophe.leroy@csgroup.eu

powerpc/inst: Define ppc_inst_t

In order to stop using 'struct ppc_inst' on PPC32,
define a ppc_inst_t typedef.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/fe5baa2c66fea9db05a8b300b3e8d2880a42596c.1638208156.git.christophe.leroy@csgroup.eu

powerpc/watchpoint: Fix exception handling for CONFIG_HAVE_HW_BREAKPOINT=N

On powerpc, ptrace watchpoint works in one-shot mode. i.e. kernel
disables event every time it fires and user has to re-enable it.
Also, in case of ptrace watchpoint, kernel notifies ptrace user
before executing instruction.

With CONFIG_HAVE_HW_BREAKPOINT=N, kernel is missing to disable
ptrace event and thus it's causing infinite loop of exceptions.
This is especially harmful when user watches on a data which is
also read/written by kernel, eg syscall parameters. In such case,
infinite exceptions happens in kernel mode which causes soft-lockup.

Fixes: 9422de3e953d ("powerpc: Hardware breakpoints rewrite to handle non DABR breakpoint registers")
Reported-by: Pedro Miraglia Franco de Carvalho <pedromfc@linux.ibm.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200902042945.129369-6-ravi.bangoria@linux.ibm.com

powerpc/watchpoint: Move DAWR detection logic outside of hw_breakpoint.c

Power10 hw has multiple DAWRs but hw doesn't tell which DAWR caused
the exception. So we have a sw logic to detect that in hw_breakpoint.c.
But hw_breakpoint.c gets compiled only with CONFIG_HAVE_HW_BREAKPOINT=Y.
Move DAWR detection logic outside of hw_breakpoint.c so that it can be
reused when CONFIG_HAVE_HW_BREAKPOINT is not set.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200902042945.129369-5-ravi.bangoria@linux.ibm.com

powerpc/watchpoint: Fix quadword instruction handling on p10 predecessors

On p10 predecessors, watchpoint with quadword access is compared at
quadword length. If the watch range is doubleword or less than that
in a first half of quadword aligned 16 bytes, and if there is any
unaligned quadword access which will access only the 2nd half, the
handler should consider it as extraneous and emulate/single-step it
before continuing.

Fixes: 74c6881019b7 ("powerpc/watchpoint: Prepare handler to handle more than one watchpoint")
Reported-by: Pedro Miraglia Franco de Carvalho <pedromfc@linux.ibm.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200902042945.129369-2-ravi.bangoria@linux.ibm.com

powerpc/hw_breakpoint.h: delete duplicated word

Drop the repeated word "the".

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200726003809.20454-6-rdunlap@infradead.org

powerpc/watchpoint: Return available watchpoints dynamically

So far Book3S Powerpc supported only one watchpoint. Power10 is
introducing 2nd DAWR. Enable 2nd DAWR support for Power10.
Availability of 2nd DAWR will depend on CPU_FTR_DAWR1.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200723090813.303838-10-ravi.bangoria@linux.ibm.com

hw-breakpoints: Fix build warnings with clang

kbuild test robot reported some build warnings in the hw_breakpoint
code when compiled with clang[1]. Some of them were introduced by the
recent powerpc change to add arch_reserve_bp_slot() and
arch_release_bp_slot(). Fix them all.

kernel/events/hw_breakpoint.c:71:12: warning: no previous prototype for function 'hw_breakpoint_weight'
kernel/events/hw_breakpoint.c:216:12: warning: no previous prototype for function 'arch_reserve_bp_slot'
kernel/events/hw_breakpoint.c:221:13: warning: no previous prototype for function 'arch_release_bp_slot'
kernel/events/hw_breakpoint.c:228:13: warning: no previous prototype for function 'arch_unregister_hw_breakpoint'

[1]: https://lore.kernel.org/linuxppc-dev/202005192233.oi9CjRtA%25lkp@intel.com/

Fixes: 29da4f91c0c1 ("powerpc/watchpoint: Don't allow concurrent perf and ptrace events")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
[mpe: Drop extern, flesh out change log, add Fixes tag]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200602041208.128913-1-ravi.bangoria@linux.ibm.com

powerpc/watchpoint: Don't allow concurrent perf and ptrace events

With Book3s DAWR, ptrace and perf watchpoints on powerpc behaves
differently. Ptrace watchpoint works in one-shot mode and generates
signal before executing instruction. It's ptrace user's job to
single-step the instruction and re-enable the watchpoint. OTOH, in
case of perf watchpoint, kernel emulates/single-steps the instruction
and then generates event. If perf and ptrace creates two events with
same or overlapping address ranges, it's ambiguous to decide who
should single-step the instruction. Because of this issue, don't
allow perf and ptrace watchpoint at the same time if their address
range overlaps.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Michael Neuling <mikey@neuling.org>
Link: https://lore.kernel.org/r/20200514111741.97993-15-ravi.bangoria@linux.ibm.com

powerpc/watchpoint: Use builtin ALIGN*() macros

Currently we calculate hw aligned start and end addresses manually.
Replace them with builtin ALIGN_DOWN() and ALIGN() macros.

So far end_addr was inclusive but this patch makes it exclusive (by
avoiding -1) for better readability.

Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Michael Neuling <mikey@neuling.org>
Link: https://lore.kernel.org/r/20200514111741.97993-13-ravi.bangoria@linux.ibm.com

powerpc/watchpoint: Get watchpoint count dynamically while disabling them

Instead of disabling only one watchpoint, get num of available
watchpoints dynamically and disable all of them.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Michael Neuling <mikey@neuling.org>
Link: https://lore.kernel.org/r/20200514111741.97993-8-ravi.bangoria@linux.ibm.com

powerpc/watchpoint: Provide DAWR number to __set_breakpoint

Introduce new parameter 'nr' to __set_breakpoint() which indicates
which DAWR should be programed. Also convert current_brk variable
to an array.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Michael Neuling <mikey@neuling.org>
Link: https://lore.kernel.org/r/20200514111741.97993-7-ravi.bangoria@linux.ibm.com

powerpc/watchpoint: Provide DAWR number to set_dawr

Introduce new parameter 'nr' to set_dawr() which indicates which DAWR
should be programed.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Michael Neuling <mikey@neuling.org>
Link: https://lore.kernel.org/r/20200514111741.97993-6-ravi.bangoria@linux.ibm.com

powerpc/watchpoint: Introduce function to get nr watchpoints dynamically

So far we had only one watchpoint, so we have hardcoded HBP_NUM to 1.
But Power10 is introducing 2nd DAWR and thus kernel should be able to
dynamically find actual number of watchpoints supported by hw it's
running on. Introduce function for the same. Also convert HBP_NUM macro
to HBP_NUM_MAX, which will now represent maximum number of watchpoints
supported by Powerpc.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Michael Neuling <mikey@neuling.org>
Link: https://lore.kernel.org/r/20200514111741.97993-4-ravi.bangoria@linux.ibm.com

powerpc/hw_breakpoints: Rewrite 8xx breakpoints to allow any address range size.

Unlike standard powerpc, Powerpc 8xx doesn't have SPRN_DABR, but
it has a breakpoint support based on a set of comparators which
allow more flexibility.

Commit 4ad8622dc548 ("powerpc/8xx: Implement hw_breakpoint")
implemented breakpoints by emulating the DABR behaviour. It did
this by setting one comparator the match 4 bytes at breakpoint address
and the other comparator to match 4 bytes at breakpoint address + 4.

Rewrite 8xx hw_breakpoint to make breakpoints match all addresses
defined by the breakpoint address and length by making full use of
comparators.

Now, comparator E is set to match any address greater than breakpoint
address minus one. Comparator F is set to match any address lower than
breakpoint address plus breakpoint length. Addresses are aligned
to 32 bits.

When the breakpoint range starts at address 0, the breakpoint is set
to match comparator F only. When the breakpoint range end at address
0xffffffff, the breakpoint is set to match comparator E only.
Otherwise the breakpoint is set to match comparator E and F.

At the same time, use registers bit names instead of hardcoded values.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/05105deeaf63bc02151aea2cdeaf525534e0e9d4.1574790198.git.christophe.leroy@c-s.fr

powerpc/watchpoint: Fix ptrace code that muck around with address/len

ptrace_set_debugreg() does not consider new length while overwriting
the watchpoint. Fix that. ppc_set_hwdebug() aligns watchpoint address
to doubleword boundary but does not change the length. If address
range is crossing doubleword boundary and length is less then 8, we
will lose samples from second doubleword. So fix that as well.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191017093204.7511-4-ravi.bangoria@linux.ibm.com

powerpc/watchpoint: Fix length calculation for unaligned target

Watchpoint match range is always doubleword(8 bytes) aligned on
powerpc. If the given range is crossing doubleword boundary, we need
to increase the length such that next doubleword also get
covered. Ex,

address len = 6 bytes
|=========.
|------------v--|------v--------|
| | | | | | | | | | | | | | | | |
|---------------|---------------|
<---8 bytes--->

In such case, current code configures hw as:
start_addr = address & ~HW_BREAKPOINT_ALIGN
len = 8 bytes

And thus read/write in last 4 bytes of the given range is ignored.
Fix this by including next doubleword in the length.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191017093204.7511-3-ravi.bangoria@linux.ibm.com

powerpc/watchpoint: Introduce macros for watchpoint length

We are hadrcoding length everywhere in the watchpoint code. Introduce
macros for the length and use them.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191017093204.7511-2-ravi.bangoria@linux.ibm.com

powerpc: Fix compile issue with force DAWR

If you compile with KVM but without CONFIG_HAVE_HW_BREAKPOINT you fail
at linking with:
arch/powerpc/kvm/book3s_hv_rmhandlers.o:(.text+0x708): undefined reference to `dawr_force_enable'

This was caused by commit c1fe190c0672 ("powerpc: Add force enable of
DAWR on P9 option").

This moves a bunch of code around to fix this. It moves a lot of the
DAWR code in a new file and creates a new CONFIG_PPC_DAWR to enable
compiling it.

Fixes: c1fe190c0672 ("powerpc: Add force enable of DAWR on P9 option")
Signed-off-by: Michael Neuling <mikey@neuling.org>
[mpe: Minor formatting in set_dawr()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version this program is distributed in the
hope that it will be useful but without any warranty without even
the implied warranty of merchantability or fitness for a particular
purpose see the gnu general public license for more details you
should have received a copy of the gnu general public license along
with this program if not write to the free software foundation inc
59 temple place suite 330 boston ma 02111 1307 usa

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 1334 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.113240726@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

powerpc: Add force enable of DAWR on P9 option

This adds a flag so that the DAWR can be enabled on P9 via:
echo Y > /sys/kernel/debug/powerpc/dawr_enable_dangerous

The DAWR was previously force disabled on POWER9 in:
9654153158 powerpc: Disable DAWR in the base POWER9 CPU features
Also see Documentation/powerpc/DAWR-POWER9.txt

This is a dangerous setting, USE AT YOUR OWN RISK.

Some users may not care about a bad user crashing their box
(ie. single user/desktop systems) and really want the DAWR. This
allows them to force enable DAWR.

This flag can also be used to disable DAWR access. Once this is
cleared, all DAWR access should be cleared immediately and your
machine once again safe from crashing.

Userspace may get confused by toggling this. If DAWR is force
enabled/disabled between getting the number of breakpoints (via
PTRACE_GETHWDBGINFO) and setting the breakpoint, userspace will get an
inconsistent view of what's available. Similarly for guests.

For the DAWR to be enabled in a KVM guest, the DAWR needs to be force
enabled in the host AND the guest. For this reason, this won't work on
POWERVM as it doesn't allow the HCALL to work. Writes of 'Y' to the
dawr_enable_dangerous file will fail if the hypervisor doesn't support
writing the DAWR.

To double check the DAWR is working, run this kernel selftest:
tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c
Any errors/failures/skips mean something is wrong.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

powerpc: fix includes in asm/processor.h

Remove superflous includes and add missing ones

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

perf/hw_breakpoint: Remove default hw_breakpoint_arch_parse()

All architectures have implemented it, we can now remove the poor weak
version.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joel Fernandes <joel.opensrc@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/1529981939-8231-11-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

perf/arch/powerpc: Implement hw_breakpoint_arch_parse()

Migrate to the new API in order to remove arch_validate_hwbkpt_settings()
that clumsily mixes up architecture validation and commit

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joel Fernandes <joel.opensrc@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/1529981939-8231-5-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

perf/hw_breakpoint: Pass arch breakpoint struct to arch_check_bp_in_kernelspace()

We can't pass the breakpoint directly on arch_check_bp_in_kernelspace()
anymore because its architecture internal datas (struct arch_hw_breakpoint)
are not yet filled by the time we call the function, and most
implementation need this backend to be up to date. So arrange the
function to take the probing struct instead.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joel Fernandes <joel.opensrc@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/1529981939-8231-3-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

powerpc/hw_breakpoint: Only disable hw breakpoint if cpu supports it

We get the below warning if we try to use kexec on P9:
kexec_core: Starting new kernel
WARNING: CPU: 0 PID: 1223 at arch/powerpc/kernel/process.c:826 __set_breakpoint+0xb4/0x140
[snip]
NIP __set_breakpoint+0xb4/0x140
LR kexec_prepare_cpus_wait+0x58/0x150
Call Trace:
0xc0000000ee70fb20 (unreliable)
0xc0000000ee70fb20
default_machine_kexec+0x234/0x2c0
machine_kexec+0x84/0x90
kernel_kexec+0xd8/0xe0
SyS_reboot+0x214/0x2c0
system_call+0x58/0x6c

This happens since we are trying to clear hw breakpoint on POWER9,
though we don't have CPU_FTR_DAWR enabled. Guard __set_breakpoint()
within hw_breakpoint_disable() with ppc_breakpoint_available() to
address this.

Fixes: 9654153158d3 ("powerpc: Disable DAWR in the base POWER9 CPU features")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

powerpc: Add missing prototypes for hw_breakpoint_handler() & arch_unregister_hw_breakpoint()

In commit 5aae8a537080 ("powerpc, hw_breakpoints: Implement
hw_breakpoints for 64-bit server processors") function
hw_breakpoint_handler() and arch_unregister_hw_breakpoint() were added
without function prototypes in hw_breakpoint.h header.

Fix the following warning(s) (treated as error in W=1):
arch/powerpc/kernel/hw_breakpoint.c:106:6: error: no previous prototype for ‘arch_unregister_hw_breakpoint’
arch/powerpc/kernel/hw_breakpoint.c:209:5: error: no previous prototype for ‘hw_breakpoint_handler’

Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

powerpc: Fix smp_processor_id() in preemptible splat in set_breakpoint

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 <paul.gortmaker@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

powerpc: Change hardware breakpoint to allow longer ranges

Change the hardware breakpoint code so that we can support wider ranged
breakpoints.

This means both ptrace and perf hardware breakpoints can use upto 512 byte long
breakpoints when using the DAWR and only 8 byte when using the DABR.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

powerpc: Rename set_break to avoid naming conflict

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 <mikey@neuling.org>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

powerpc: Hardware breakpoints rewrite to handle non DABR breakpoint registers

This is a rewrite so that we don't assume we are using the DABR throughout the
code. We now use the arch_hw_breakpoint to store the breakpoint in a generic
manner in the thread_struct, rather than storing the raw DABR value.

The ptrace GET/SET_DEBUGREG interface currently passes the raw DABR in from
userspace. We keep this functionality, so that future changes (like the POWER8
DAWR), will still fake the DABR to userspace.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

powerpc: Dynamically calculate the dabrx based on kernel/user/hypervisor

Currently we mark the DABRX to interrupt on all matches
(hypervisor/kernel/user and then filter in software. We can be a lot
smarter now that we can set the DABRX dynamically.

This sets the DABRX based on the flags passed by the user.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

powerpc: Rework set_dabr so it can take a DABRX value as well

Rework set_dabr to take a DABRX value as well.

Both the pseries and PS3 hypervisors do some checks on the DABRX
values that are passed in the hcall. This patch stops bogus values
from being passed to hypervisor. Also, in the case where we are
clearing the breakpoint, where DABR and DABRX are zero, we modify the
DABRX value to make it valid so that the hcall won't fail.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

powerpc: Pack arch_hw_breakpoint to avoid holes in struct

No functional change

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Disintegrate asm/system.h for PowerPC

Disintegrate asm/system.h for PowerPC.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
cc: linuxppc-dev@lists.ozlabs.org

perf, powerpc: Fix build borkage

The patch a8b0ca17b80e ("perf: Remove the nmi parameter from the swevent
and overflow interface") missed a spot in the ppc hw_breakpoint code,
fix this up so things compile again.

Reported-by: Ingo Molnar <mingo@elte.hu>
Cc: Anton Blanchard <anton@samba.org>
Cc: Eric B Munson <emunson@mgebm.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-09pfip95g88s70iwkxu6nnbt@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

powerpc, hw_breakpoint: Tell generic code we have no instruction breakpoints

At present, hw_breakpoint_slots() returns 1 regardless of what
type of breakpoint is specified in the type argument. Since we
don't define CONFIG_HAVE_MIXED_BREAKPOINTS_REGS, there are
separate values for TYPE_INST and TYPE_DATA, and hw_breakpoint_slots()
returns 1 for both, effectively advertising instruction breakpoint
support which doesn't exist.

This fixes it by making hw_breakpoint_slots return 1 for TYPE_DATA
and 0 for TYPE_INST. This moves hw_breakpoint_slots() from the
powerpc hw_breakpoint.h to hw_breakpoint.c because the definitions
of TYPE_INST and TYPE_DATA aren't available in <asm/hw_breakpoint.h>.
They are defined in <linux/hw_breakpoint.h> but we can't include
that header in <asm/hw_breakpoint.h>, and nor can we rely on
<linux/hw_breakpoint.h> being included before <asm/hw_breakpoint.h>.
Since hw_breakpoint_slots() is only called at boot time, there is
no performance impact from making it a real function rather than
a static inline.

Signed-off-by: Paul Mackerras <paulus@samba.org>

powerpc, hw_breakpoint: Discard extraneous interrupt due to accesses outside symbol length

Many a times, the requested breakpoint length can be less than the
fixed breakpoint length i.e. 8 bytes supported by PowerPC 64-bit
server (Book III S) processors. This could lead to extraneous
interrupts resulting in false breakpoint notifications. This
detects and discards such interrupts for non-ptrace requests.
We don't change ptrace behaviour to avoid breaking compatability.

[Suggestion from Paul Mackerras <paulus@samba.org> to add a new flag in
'struct arch_hw_breakpoint' to identify extraneous interrupts]

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

powerpc, hw_breakpoint: Enable hw-breakpoints while handling intervening signals

A signal delivered between a hw_breakpoint_handler() and the
single_step_dabr_instruction() will not have the breakpoint active
while the signal handler is running -- the signal delivery will
set up a new MSR value which will not have MSR_SE set, so we
won't get the signal step interrupt until and unless the signal
handler returns (which it may never do).

To fix this, we restore the breakpoint when delivering a signal --
we clear the MSR_SE bit and set the DABR again. If the signal
handler returns, the DABR interrupt will occur again when the
instruction that we were originally trying to single-step gets
re-executed.

[Paul Mackerras <paulus@samba.org> pointed out the need to do this.]

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

powerpc, hw_breakpoints: Implement hw_breakpoints for 64-bit server processors

Implement perf-events based hw-breakpoint interfaces for PowerPC
64-bit server (Book III S) processors. This allows access to a
given location to be used as an event that can be counted or
profiled by the perf_events subsystem.

This is done using the DABR (data breakpoint register), which can
also be used for process debugging via ptrace. When perf_event
hw_breakpoint support is configured in, the perf_event subsystem
manages the DABR and arbitrates access to it, and ptrace then
creates a perf_event when it is requested to set a data breakpoint.

[Adopted suggestions from Paul Mackerras <paulus@samba.org> to
- emulate_step() all system-wide breakpoints and single-step only the
per-task breakpoints
- perform arch-specific cleanup before unregistration through
arch_unregister_hw_breakpoint()
]

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>