Currently if you are doing a global perf recording with hardware
breakpoints (ie perf record -e mem:0xdeadbeef -a), you can oops with:
Faulting instruction address: 0xc000000000738890
cpu 0xc: Vector: 300 (Data Access) at [c0000003f76af8d0]
pc: c000000000738890: .hw_breakpoint_handler+0xa0/0x1e0
lr: c000000000738830: .hw_breakpoint_handler+0x40/0x1e0
sp: c0000003f76afb50
msr: 8000000000001032
dar: 6f0
dsisr: 42000000
current = 0xc0000003f765ac00
paca = 0xc00000000f262a00 softe: 0 irq_happened: 0x01
pid = 6810, comm = loop-read
enter ? for help
[c0000003f76afbe0] c00000000073cd04 .notifier_call_chain.isra.0+0x84/0xe0
[c0000003f76afc80] c00000000073cdbc .notify_die+0x3c/0x60
[c0000003f76afd20] c0000000000139f0 .do_dabr+0x40/0xf0
[c0000003f76afe30] c000000000005a9c handle_dabr_fault+0x14/0x48
--- Exception: 300 (Data Access) at 0000000010000480
SP (ff8679e0) is in userspace
This is because we don't check to see if the break point is associated
with task before we deference the task_struct pointer.
This changes the update to use current.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
If arch_validate_hwbkpt_settings() fails, bp->ctx won't be valid and the
kernel panics. Add a check to fix this.
Reported-by: Edjunior Barbosa Machado <emachado@linux.vnet.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
None of the files touched here are modules, and they are not
exporting any symbols either -- so there is no need to be including
the module.h. Builds of all the files remains successful.
Even kernel/module.c does not need to include it, since it includes
linux/moduleloader.h instead.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
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>
The code we had to clear the MSR_SE bit was not doing anything because
the caller (ultimately single_step_exception() in traps.c) had already
cleared. Instead of trying to leave MSR_SE set if the TIF_SINGLESTEP
flag is set (which indicates that the process is being single-stepped
by ptrace), we instead return NOTIFY_DONE in that case, which means
the caller will generate a SIGTRAP for the process.
Signed-off-by: Paul Mackerras <paulus@samba.org>
The code would accept an access to an address one byte past the end
of the requested range as legitimate, due to having a "<=" rather than
a "<". This fixes that and cleans up the code a bit.
Signed-off-by: Paul Mackerras <paulus@samba.org>
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>
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>
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>
