linux-toradex.git/kernel/kprobes.c, branch v4.12

kprobes/x86: Fix to set RWX bits correctly before releasing trampoline

2017-05-27T02:37:00+00:00

Fix kprobes to set(recover) RWX bits correctly on trampoline
buffer before releasing it. Releasing readonly page to
module_memfree() crash the kernel.

Without this fix, if kprobes user register a bunch of kprobes
in function body (since kprobes on function entry usually
use ftrace) and unregister it, kernel hits a BUG and crash.

Link: http://lkml.kernel.org/r/149570868652.3518.14120169373590420503.stgit@devbox

Signed-off-by: Masami Hiramatsu 
Fixes: d0381c81c2f7 ("kprobes/x86: Set kprobes pages read-only")
Signed-off-by: Steven Rostedt (VMware)

kprobes: Document how optimized kprobes are removed from module unload

2017-05-18T01:55:58+00:00

Thomas discovered a bug where the kprobe trace tests had a race
condition where the kprobe_optimizer called from a delayed work queue
that does the optimizing and "unoptimizing" of a kprobe, can try to
modify the text after it has been freed by the init code.

The kprobe trace selftest is a special case, and Thomas and myself
investigated to see if there's a chance that this could also be a bug
with module unloading, as the code is not obvious to how it handles
this. After adding lots of printks, I figured it out. Thomas suggested
that this should be commented so that others will not have to go
through this exercise again.

Link: http://lkml.kernel.org/r/20170516145835.3827d3aa@gandalf.local.home

Acked-by: Masami Hiramatsu 
Suggested-by: Thomas Gleixner 
Signed-off-by: Steven Rostedt (VMware)

tracing/kprobes: Enforce kprobes teardown after testing

2017-05-18T01:50:27+00:00

Enabling the tracer selftest triggers occasionally the warning in
text_poke(), which warns when the to be modified page is not marked
reserved.

The reason is that the tracer selftest installs kprobes on functions marked
__init for testing. These probes are removed after the tests, but that
removal schedules the delayed kprobes_optimizer work, which will do the
actual text poke. If the work is executed after the init text is freed,
then the warning triggers. The bug can be reproduced reliably when the work
delay is increased.

Flush the optimizer work and wait for the optimizing/unoptimizing lists to
become empty before returning from the kprobes tracer selftest. That
ensures that all operations which were queued due to the probes removal
have completed.

Link: http://lkml.kernel.org/r/20170516094802.76a468bb@gandalf.local.home

Signed-off-by: Thomas Gleixner 
Acked-by: Masami Hiramatsu 
Cc: stable@vger.kernel.org
Fixes: 6274de498 ("kprobes: Support delayed unoptimizing")
Signed-off-by: Steven Rostedt (VMware)

Merge tag 'powerpc-4.12-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

2017-05-05T18:36:44+00:00

Pull powerpc updates from Michael Ellerman:
 "Highlights include:

   - Larger virtual address space on 64-bit server CPUs. By default we
     use a 128TB virtual address space, but a process can request access
     to the full 512TB by passing a hint to mmap().

   - Support for the new Power9 "XIVE" interrupt controller.

   - TLB flushing optimisations for the radix MMU on Power9.

   - Support for CAPI cards on Power9, using the "Coherent Accelerator
     Interface Architecture 2.0".

   - The ability to configure the mmap randomisation limits at build and
     runtime.

   - Several small fixes and cleanups to the kprobes code, as well as
     support for KPROBES_ON_FTRACE.

   - Major improvements to handling of system reset interrupts,
     correctly treating them as NMIs, giving them a dedicated stack and
     using a new hypervisor call to trigger them, all of which should
     aid debugging and robustness.

   - Many fixes and other minor enhancements.

  Thanks to: Alastair D'Silva, Alexey Kardashevskiy, Alistair Popple,
  Andrew Donnellan, Aneesh Kumar K.V, Anshuman Khandual, Anton
  Blanchard, Balbir Singh, Ben Hutchings, Benjamin Herrenschmidt,
  Bhupesh Sharma, Chris Packham, Christian Zigotzky, Christophe Leroy,
  Christophe Lombard, Daniel Axtens, David Gibson, Gautham R. Shenoy,
  Gavin Shan, Geert Uytterhoeven, Guilherme G. Piccoli, Hamish Martin,
  Hari Bathini, Kees Cook, Laurent Dufour, Madhavan Srinivasan, Mahesh J
  Salgaonkar, Mahesh Salgaonkar, Masami Hiramatsu, Matt Brown, Matthew
  R. Ochs, Michael Neuling, Naveen N. Rao, Nicholas Piggin, Oliver
  O'Halloran, Pan Xinhui, Paul Mackerras, Rashmica Gupta, Russell
  Currey, Sukadev Bhattiprolu, Thadeu Lima de Souza Cascardo, Tobin C.
  Harding, Tyrel Datwyler, Uma Krishnan, Vaibhav Jain, Vipin K Parashar,
  Yang Shi"

* tag 'powerpc-4.12-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (214 commits)
  powerpc/64s: Power9 has no LPCR[VRMASD] field so don't set it
  powerpc/powernv: Fix TCE kill on NVLink2
  powerpc/mm/radix: Drop support for CPUs without lockless tlbie
  powerpc/book3s/mce: Move add_taint() later in virtual mode
  powerpc/sysfs: Move #ifdef CONFIG_HOTPLUG_CPU out of the function body
  powerpc/smp: Document irq enable/disable after migrating IRQs
  powerpc/mpc52xx: Don't select user-visible RTAS_PROC
  powerpc/powernv: Document cxl dependency on special case in pnv_eeh_reset()
  powerpc/eeh: Clean up and document event handling functions
  powerpc/eeh: Avoid use after free in eeh_handle_special_event()
  cxl: Mask slice error interrupts after first occurrence
  cxl: Route eeh events to all drivers in cxl_pci_error_detected()
  cxl: Force context lock during EEH flow
  powerpc/64: Allow CONFIG_RELOCATABLE if COMPILE_TEST
  powerpc/xmon: Teach xmon oops about radix vectors
  powerpc/mm/hash: Fix off-by-one in comment about kernel contexts ids
  powerpc/pseries: Enable VFIO
  powerpc/powernv: Fix iommu table size calculation hook for small tables
  powerpc/powernv: Check kzalloc() return value in pnv_pci_table_alloc
  powerpc: Add arch/powerpc/tools directory
  ...

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

kprobes: Skip preparing optprobe if the probe is ftrace-based

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

Skip preparing optprobe if the probe is ftrace-based, since anyway, it
must not be optimized (or already optimized by ftrace).

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

trace/kprobes: Fix check for kretprobe offset within function entry

2017-03-15T20:48:37+00:00

perf specifies an offset from _text and since this offset is fed
directly into the arch-specific helper, kprobes tracer rejects
installation of kretprobes through perf. Fix this by looking up the
actual offset from a function for the specified sym+offset.

Refactor and reuse existing routines to limit code duplication -- we
repurpose kprobe_addr() for determining final kprobe address and we
split out the function entry offset determination into a separate
generic helper.

Before patch:

  naveen@ubuntu:~/linux/tools/perf$ sudo ./perf probe -v do_open%return
  probe-definition(0): do_open%return
  symbol:do_open file:(null) line:0 offset:0 return:1 lazy:(null)
  0 arguments
  Looking at the vmlinux_path (8 entries long)
  Using /boot/vmlinux for symbols
  Open Debuginfo file: /boot/vmlinux
  Try to find probe point from debuginfo.
  Matched function: do_open [2d0c7ff]
  Probe point found: do_open+0
  Matched function: do_open [35d76dc]
  found inline addr: 0xc0000000004ba9c4
  Failed to find "do_open%return",
   because do_open is an inlined function and has no return point.
  An error occurred in debuginfo analysis (-22).
  Trying to use symbols.
  Opening /sys/kernel/debug/tracing//README write=0
  Opening /sys/kernel/debug/tracing//kprobe_events write=1
  Writing event: r:probe/do_open _text+4469776
  Failed to write event: Invalid argument
    Error: Failed to add events. Reason: Invalid argument (Code: -22)
  naveen@ubuntu:~/linux/tools/perf$ dmesg | tail
  
  [   33.568656] Given offset is not valid for return probe.

After patch:

  naveen@ubuntu:~/linux/tools/perf$ sudo ./perf probe -v do_open%return
  probe-definition(0): do_open%return
  symbol:do_open file:(null) line:0 offset:0 return:1 lazy:(null)
  0 arguments
  Looking at the vmlinux_path (8 entries long)
  Using /boot/vmlinux for symbols
  Open Debuginfo file: /boot/vmlinux
  Try to find probe point from debuginfo.
  Matched function: do_open [2d0c7d6]
  Probe point found: do_open+0
  Matched function: do_open [35d76b3]
  found inline addr: 0xc0000000004ba9e4
  Failed to find "do_open%return",
   because do_open is an inlined function and has no return point.
  An error occurred in debuginfo analysis (-22).
  Trying to use symbols.
  Opening /sys/kernel/debug/tracing//README write=0
  Opening /sys/kernel/debug/tracing//kprobe_events write=1
  Writing event: r:probe/do_open _text+4469808
  Writing event: r:probe/do_open_1 _text+4956344
  Added new events:
    probe:do_open        (on do_open%return)
    probe:do_open_1      (on do_open%return)

  You can now use it in all perf tools, such as:

	  perf record -e probe:do_open_1 -aR sleep 1

  naveen@ubuntu:~/linux/tools/perf$ sudo cat /sys/kernel/debug/kprobes/list
  c000000000041370  k  kretprobe_trampoline+0x0    [OPTIMIZED]
  c0000000004ba0b8  r  do_open+0x8    [DISABLED]
  c000000000443430  r  do_open+0x0    [DISABLED]

Signed-off-by: Naveen N. Rao 
Acked-by: Masami Hiramatsu 
Cc: Ananth N Mavinakayanahalli 
Cc: Michael Ellerman 
Cc: Steven Rostedt 
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/d8cd1ef420ec22e3643ac332fdabcffc77319a42.1488961018.git.naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo

kprobes: Convert kprobe_exceptions_notify to use NOKPROBE_SYMBOL

2017-03-14T18:17:40+00:00

commit fc62d0207ae0 ("kprobes: Introduce weak variant of
kprobe_exceptions_notify()") used the __kprobes annotation to exclude
kprobe_exceptions_notify from being probed. Since NOKPROBE_SYMBOL() is a
better way to do this enabling the symbol to be discovered as being
blacklisted, change over to using NOKPROBE_SYMBOL().

Signed-off-by: Naveen N. Rao 
Acked-by: Masami Hiramatsu 
Cc: Ananth N Mavinakayanahalli 
Link: http://lkml.kernel.org/r/3f25bf400da5c222cd9b10eec6ded2d6b58209f8.1488991670.git.naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo

kretprobes: Ensure probe location is at function entry

2017-03-03T22:07:17+00:00

kretprobes can be registered by specifying an absolute address or by
specifying offset to a symbol. However, we need to ensure this falls at
function entry so as to be able to determine the return address.

Validate the same during kretprobe registration. By default, there
should not be any offset from a function entry, as determined through a
kallsyms_lookup(). Introduce arch_function_offset_within_entry() as a
way for architectures to override this.

Signed-off-by: Naveen N. Rao 
Acked-by: Masami Hiramatsu 
Cc: Ananth N Mavinakayanahalli 
Cc: Michael Ellerman 
Cc: Steven Rostedt 
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/f1583bc4839a3862cfc2acefcc56f9c8837fa2ba.1487770934.git.naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo