include/stap-probe.h

   1 /* Macros for defining Systemtap <sys/sdt.h> static probe points.
   2    Copyright (C) 2012-2013 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 # ifndef NOT_IN_libc
  36 #  define IN_LIB        libc
  37 # elif !defined IN_LIB
  38 /* This is intentionally defined with extra unquoted commas in it so
  39    that macro substitution will bomb out when it is used.  We don't
  40    just use #error here, so that this header can be included by
  41    other headers that use LIBC_PROBE inside their own macros.  We
  42    only want such headers to fail to compile if those macros are
  43    actually used in a context where IN_LIB has not been defined.  */
  44 #  define IN_LIB        ,,,missing -DIN_LIB=... -- not extra-lib.mk?,,,
  45 # endif
  46
  47 # define LIBC_PROBE(name, n, ...)       \
  48   LIBC_PROBE_1 (IN_LIB, name, n, ## __VA_ARGS__)
  49
  50 # define LIBC_PROBE_1(lib, name, n, ...) \
  51   STAP_PROBE##n (lib, name, ## __VA_ARGS__)
  52
  53 # define STAP_PROBE0            STAP_PROBE
  54
  55 # define LIBC_PROBE_ASM(name, template) \
  56   STAP_PROBE_ASM (IN_LIB, name, template)
  57
  58 # define LIBC_PROBE_ASM_OPERANDS STAP_PROBE_ASM_OPERANDS
  59
  60 #else  /* Not USE_STAP_PROBE.  */
  61
  62 # ifndef __ASSEMBLER__
  63 /* Evaluate all the arguments and verify that N matches their number.  */
  64 #  define LIBC_PROBE(name, n, ...)                                            \
  65   do {                                                                        \
  66     _Bool __libc_probe_args[] = { 0, ## __VA_ARGS__ };                        \
  67     _Bool __libc_probe_verify_n[(sizeof __libc_probe_args / sizeof (_Bool))   \
  68                                 == n + 1 ? 1 : -1];                           \
  69     (void) __libc_probe_verify_n;                                             \
  70   } while (0)
  71 # else
  72 #  define LIBC_PROBE(name, n, ...)              /* Nothing.  */
  73 # endif
  74
  75 # define LIBC_PROBE_ASM(name, template)         /* Nothing.  */
  76 # define LIBC_PROBE_ASM_OPERANDS(n, ...)        /* Nothing.  */
  77
  78 #endif  /* USE_STAP_PROBE.  */
  79
  80 #endif  /* stap-probe.h */