include/stap-probe.h

   1 /* Macros for defining Systemtap <sys/sdt.h> static probe points.
   2    Copyright (C) 2012-2022 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    <https://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 <stap-probe-machine.h>
  25 # include <sys/sdt.h>
  26
  27 /* Our code uses one macro LIBC_PROBE (name, n, arg1, ..., argn).
  28
  29    Without USE_STAP_PROBE, that does nothing but evaluates all
  30    its arguments (to prevent bit rot, unlike e.g. assert).
  31
  32    Systemtap's header defines the macros STAP_PROBE (provider, name) and
  33    STAP_PROBEn (provider, name, arg1, ..., argn).  For "provider" we paste
  34    in MODULE_NAME (libc, libpthread, etc.) automagically.
  35
  36    The format of the arg parameters is discussed here:
  37
  38    https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
  39
  40    The precise details of how register names are specified is
  41    architecture specific and can be found in the gdb and SystemTap
  42    source code.  */
  43
  44 # define LIBC_PROBE(name, n, ...)       \
  45   LIBC_PROBE_1 (MODULE_NAME, name, n, ## __VA_ARGS__)
  46
  47 # define LIBC_PROBE_1(lib, name, n, ...) \
  48   STAP_PROBE##n (lib, name, ## __VA_ARGS__)
  49
  50 # define STAP_PROBE0            STAP_PROBE
  51
  52 # define LIBC_PROBE_ASM(name, template) \
  53   STAP_PROBE_ASM (MODULE_NAME, name, template)
  54
  55 # define LIBC_PROBE_ASM_OPERANDS STAP_PROBE_ASM_OPERANDS
  56
  57 #else  /* Not USE_STAP_PROBE.  */
  58
  59 # ifndef __ASSEMBLER__
  60 /* Evaluate all the arguments and verify that N matches their number.  */
  61 #  define LIBC_PROBE(name, n, ...) STAP_PROBE##n (__VA_ARGS__)
  62
  63 #  define STAP_PROBE0()                         do {} while (0)
  64 #  define STAP_PROBE1(a1)                       do {} while (0)
  65 #  define STAP_PROBE2(a1, a2)                   do {} while (0)
  66 #  define STAP_PROBE3(a1, a2, a3)               do {} while (0)
  67 #  define STAP_PROBE4(a1, a2, a3, a4)           do {} while (0)
  68
  69 # else
  70 #  define LIBC_PROBE(name, n, ...)              /* Nothing.  */
  71 # endif
  72
  73 # define LIBC_PROBE_ASM(name, template)         /* Nothing.  */
  74 # define LIBC_PROBE_ASM_OPERANDS(n, ...)        /* Nothing.  */
  75
  76 #endif  /* USE_STAP_PROBE.  */
  77
  78 #endif  /* stap-probe.h */