linux.git/arch/powerpc/kernel/optprobes.c, branch v5.4.211

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152

2019-05-30T18:26:32+00:00

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

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 3029 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Allison Randal 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman

powerpc/kprobes: Do not disable interrupts for optprobes and kprobes_on_ftrace

2017-11-12T12:51:41+00:00

Per Documentation/kprobes.txt, we don't necessarily need to disable
interrupts before invoking the kprobe handlers. Masami submitted
similar changes for x86 via commit a19b2e3d783964 ("kprobes/x86: Remove
IRQ disabling from ftrace-based/optimized kprobes"). Do the same for
powerpc.

Signed-off-by: Naveen N. Rao 
Acked-by: Masami Hiramatsu 
Signed-off-by: Michael Ellerman

powerpc/kprobes: Disable preemption before invoking probe handler for optprobes

2017-11-12T12:51:40+00:00

Per Documentation/kprobes.txt, probe handlers need to be invoked with
preemption disabled. Update optimized_callback() to do so. Also move
get_kprobe_ctlblk() invocation post preemption disable, since it
accesses pre-cpu data.

This was not an issue so far since optprobes wasn't selected if
CONFIG_PREEMPT was enabled. Commit a30b85df7d599f ("kprobes: Use
synchronize_rcu_tasks() for optprobe with CONFIG_PREEMPT=y") changes
this.

Signed-off-by: Naveen N. Rao 
Acked-by: Masami Hiramatsu 
Signed-off-by: Michael Ellerman

powerpc/kprobes: Update optprobes to use emulate_update_regs()

2017-09-20T10:21:24+00:00

Optprobes depended on an updated regs->nip from analyse_instr() to
identify the location to branch back from the optprobes trampoline.
However, since commit 3cdfcbfd32b9d ("powerpc: Change analyse_instr so
it doesn't modify *regs"), analyse_instr() doesn't update the registers
anymore.  Due to this, we end up branching back from the optprobes
trampoline to the same branch into the trampoline resulting in a loop.

Fix this by calling out to emulate_update_regs() before using the nip.
Additionally, explicitly compare the return value from analyse_instr()
to 1, rather than just checking for !0 so as to guard against any
future changes to analyse_instr() that may result in -1 being returned
in more scenarios.

Fixes: 3cdfcbfd32b9d ("powerpc: Change analyse_instr so it doesn't modify *regs")
Signed-off-by: Naveen N. Rao 
Signed-off-by: Michael Ellerman

powerpc/kprobes/optprobes: Use patch_instruction()

2017-07-03T13:12:19+00:00

So that we can implement STRICT_RWX, use patch_instruction() in
optprobes.

Signed-off-by: Balbir Singh 
Signed-off-by: Michael Ellerman

powerpc: Introduce a new helper to obtain function entry points

2017-04-24T09:07:58+00:00

kprobe_lookup_name() is specific to the kprobe subsystem and may not always
return the function entry point (in a subsequent patch for KPROBES_ON_FTRACE).
For looking up function entry points, introduce a separate helper and use it
in optprobes.c

Signed-off-by: Naveen N. Rao 
Signed-off-by: Michael Ellerman

powerpc/kprobes: Fix handling of function offsets on ABIv2

2017-04-20T13:18:55+00:00

commit 239aeba76409 ("perf powerpc: Fix kprobe and kretprobe handling with
kallsyms on ppc64le") changed how we use the offset field in struct kprobe on
ABIv2. perf now offsets from the global entry point if an offset is specified
and otherwise chooses the local entry point.

Fix the same in kernel for kprobe API users. We do this by extending
kprobe_lookup_name() to accept an additional parameter to indicate the offset
specified with the kprobe registration. If offset is 0, we return the local
function entry and return the global entry point otherwise.

With:
  # cd /sys/kernel/debug/tracing/
  # echo "p _do_fork" >> kprobe_events
  # echo "p _do_fork+0x10" >> kprobe_events

before this patch:
  # cat ../kprobes/list
  c0000000000d0748  k  _do_fork+0x8    [DISABLED]
  c0000000000d0758  k  _do_fork+0x18    [DISABLED]
  c0000000000412b0  k  kretprobe_trampoline+0x0    [OPTIMIZED]

and after:
  # cat ../kprobes/list
  c0000000000d04c8  k  _do_fork+0x8    [DISABLED]
  c0000000000d04d0  k  _do_fork+0x10    [DISABLED]
  c0000000000412b0  k  kretprobe_trampoline+0x0    [OPTIMIZED]

Acked-by: Ananth N Mavinakayanahalli 
Signed-off-by: Naveen N. Rao 
Signed-off-by: Michael Ellerman

kprobes: Convert kprobe_lookup_name() to a function

2017-04-20T13:18:54+00:00

The macro is now pretty long and ugly on powerpc. In the light of further
changes needed here, convert it to a __weak variant to be over-ridden with a
nicer looking function.

Suggested-by: Masami Hiramatsu 
Acked-by: Masami Hiramatsu 
Signed-off-by: Naveen N. Rao 
Signed-off-by: Michael Ellerman

powerpc/kprobes: Optimize kprobe in kretprobe_trampoline()

2017-02-10T02:28:05+00:00

Kprobe placed on the  kretprobe_trampoline() during boot time can be
optimized, since the instruction at probe point is a 'nop'.

Signed-off-by: Anju T Sudhakar 
Acked-by: Masami Hiramatsu 
Signed-off-by: Michael Ellerman

powerpc/kprobes: Implement Optprobes

2017-02-10T02:28:04+00:00

Current infrastructure of kprobe uses the unconditional trap instruction
to probe a running kernel. Optprobe allows kprobe to replace the trap
with a branch instruction to a detour buffer. Detour buffer contains
instructions to create an in memory pt_regs. Detour buffer also has a
call to optimized_callback() which in turn call the pre_handler(). After
the execution of the pre-handler, a call is made for instruction
emulation. The NIP is determined in advanced through dummy instruction
emulation and a branch instruction is created to the NIP at the end of
the trampoline.

To address the limitation of branch instruction in POWER architecture,
detour buffer slot is allocated from a reserved area. For the time
being, 64KB is reserved in memory for this purpose.

Instructions which can be emulated using analyse_instr() are the
candidates for optimization. Before optimization ensure that the address
range between the detour buffer allocated and the instruction being
probed is within +/- 32MB.

Signed-off-by: Anju T Sudhakar 
Signed-off-by: Naveen N. Rao 
Acked-by: Masami Hiramatsu 
Signed-off-by: Michael Ellerman