glibc/include/stap-probe.h
Will Newton b4f12ca391 include/stap-probe.h: Add comment about SystemTap argument format
Add a comment pointing to the SystemTap wiki page that documents the
format of the arguments. Also add a pointer to the SystemTap and
gdb sources which seem to be the best place to get the architecture
specific details.

ChangeLog:

2014-02-11  Will Newton  <will.newton@linaro.org>

	* include/stap-probe.h: Add comment about probe argument
	format.
2014-02-11 10:17:11 +00:00

90 lines
3.0 KiB
C

/* Macros for defining Systemtap <sys/sdt.h> static probe points.
Copyright (C) 2012-2014 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#ifndef _STAP_PROBE_H
#define _STAP_PROBE_H 1
#ifdef USE_STAP_PROBE
# include <sys/sdt.h>
/* Our code uses one macro LIBC_PROBE (name, n, arg1, ..., argn).
Without USE_STAP_PROBE, that does nothing but evaluates all
its arguments (to prevent bit rot, unlike e.g. assert).
Systemtap's header defines the macros STAP_PROBE (provider, name) and
STAP_PROBEn (provider, name, arg1, ..., argn). For "provider" we paste
in the IN_LIB name (libc, libpthread, etc.) automagically.
The format of the arg parameters is discussed here:
https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
The precise details of how register names are specified is
architecture specific and can be found in the gdb and SystemTap
source code. */
# ifndef NOT_IN_libc
# define IN_LIB libc
# elif !defined IN_LIB
/* This is intentionally defined with extra unquoted commas in it so
that macro substitution will bomb out when it is used. We don't
just use #error here, so that this header can be included by
other headers that use LIBC_PROBE inside their own macros. We
only want such headers to fail to compile if those macros are
actually used in a context where IN_LIB has not been defined. */
# define IN_LIB ,,,missing -DIN_LIB=... -- not extra-lib.mk?,,,
# endif
# define LIBC_PROBE(name, n, ...) \
LIBC_PROBE_1 (IN_LIB, name, n, ## __VA_ARGS__)
# define LIBC_PROBE_1(lib, name, n, ...) \
STAP_PROBE##n (lib, name, ## __VA_ARGS__)
# define STAP_PROBE0 STAP_PROBE
# define LIBC_PROBE_ASM(name, template) \
STAP_PROBE_ASM (IN_LIB, name, template)
# define LIBC_PROBE_ASM_OPERANDS STAP_PROBE_ASM_OPERANDS
#else /* Not USE_STAP_PROBE. */
# ifndef __ASSEMBLER__
/* Evaluate all the arguments and verify that N matches their number. */
#define LIBC_PROBE(name, n, ...) STAP_PROBE##n (__VA_ARGS__)
#define STAP_PROBE0()
#define STAP_PROBE1(a1)
#define STAP_PROBE2(a1, a2)
#define STAP_PROBE3(a1, a2, a3)
#define STAP_PROBE4(a1, a2, a3, a4)
# else
# define LIBC_PROBE(name, n, ...) /* Nothing. */
# endif
# define LIBC_PROBE_ASM(name, template) /* Nothing. */
# define LIBC_PROBE_ASM_OPERANDS(n, ...) /* Nothing. */
#endif /* USE_STAP_PROBE. */
#endif /* stap-probe.h */