• Naveen N. Rao's avatar
    trace/kprobes: Fix check for kretprobe offset within function entry · 1d585e70
    Naveen N. Rao authored
    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
      <snip>
      [   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: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
    Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
    Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
    Cc: Michael Ellerman <mpe@ellerman.id.au>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: linuxppc-dev@lists.ozlabs.org
    Link: http://lkml.kernel.org/r/d8cd1ef420ec22e3643ac332fdabcffc77319a42.1488961018.git.naveen.n.rao@linux.vnet.ibm.comSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    1d585e70
trace_kprobe.c 37.2 KB