include/stap-probe.h

   1 /* Macros for defining Systemtap <sys/sdt.h> static probe points.
   2    Copyright (C) 2012-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _STAP_PROBE_H
  20 #define _STAP_PROBE_H 1
  21
  22 #ifdef USE_STAP_PROBE
  23
  24 # include <sys/sdt.h>
  25
  26 /* Our code uses one macro LIBC_PROBE (name, n, arg1, ..., argn).
  27
  28    Without USE_STAP_PROBE, that does nothing but evaluates all
  29    its arguments (to prevent bit rot, unlike e.g. assert).
  30
  31    Systemtap's header defines the macros STAP_PROBE (provider, name) and
  32    STAP_PROBEn (provider, name, arg1, ..., argn).  For "provider" we paste
  33    in the IN_LIB name (libc, libpthread, etc.) automagically.
  34
  35    The format of the arg parameters is discussed here:
  36
  37    https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
  38
  39    The precise details of how register names are specified is
  40    architecture specific and can be found in the gdb and SystemTap
  41    source code.  */
  42
  43 # ifndef NOT_IN_libc
  44 #  define IN_LIB        libc
  45 # elif !defined IN_LIB
  46 /* This is intentionally defined with extra unquoted commas in it so
  47    that macro substitution will bomb out when it is used.  We don't
  48    just use #error here, so that this header can be included by
  49    other headers that use LIBC_PROBE inside their own macros.  We
  50    only want such headers to fail to compile if those macros are
  51    actually used in a context where IN_LIB has not been defined.  */
  52 #  define IN_LIB        ,,,missing -DIN_LIB=... -- not extra-lib.mk?,,,
  53 # endif
  54
  55 # define LIBC_PROBE(name, n, ...)       \
  56   LIBC_PROBE_1 (IN_LIB, name, n, ## __VA_ARGS__)
  57
  58 # define LIBC_PROBE_1(lib, name, n, ...) \
  59   STAP_PROBE##n (lib, name, ## __VA_ARGS__)
  60
  61 # define STAP_PROBE0            STAP_PROBE
  62
  63 # define LIBC_PROBE_ASM(name, template) \
  64   STAP_PROBE_ASM (IN_LIB, name, template)
  65
  66 # define LIBC_PROBE_ASM_OPERANDS STAP_PROBE_ASM_OPERANDS
  67
  68 #else  /* Not USE_STAP_PROBE.  */
  69
  70 # ifndef __ASSEMBLER__
  71 /* Evaluate all the arguments and verify that N matches their number.  */
  72 #define LIBC_PROBE(name, n, ...) STAP_PROBE##n (__VA_ARGS__)
  73
  74 #define STAP_PROBE0()
  75 #define STAP_PROBE1(a1)
  76 #define STAP_PROBE2(a1, a2)
  77 #define STAP_PROBE3(a1, a2, a3)
  78 #define STAP_PROBE4(a1, a2, a3, a4)
  79
  80 # else
  81 #  define LIBC_PROBE(name, n, ...)              /* Nothing.  */
  82 # endif
  83
  84 # define LIBC_PROBE_ASM(name, template)         /* Nothing.  */
  85 # define LIBC_PROBE_ASM_OPERANDS(n, ...)        /* Nothing.  */
  86
  87 #endif  /* USE_STAP_PROBE.  */
  88
  89 #endif  /* stap-probe.h */