1/* Profile PC and write result to FIFO.
2 Copyright (C) 1999-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1999.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <https://www.gnu.org/licenses/>. */
19
20#include <errno.h>
21#include <fcntl.h>
22#include <stdint.h>
23#include <stdlib.h>
24#include <unistd.h>
25
26/* Nonzero if we are actually doing something. */
27static int active;
28
29/* The file descriptor of the FIFO. */
30static int fd;
31
32
33static void
34__attribute__ ((constructor))
35install (void)
36{
37 /* See whether the environment variable `PCPROFILE_OUTPUT' is defined.
38 If yes, it should name a FIFO. We open it and mark ourself as active. */
39 const char *outfile = getenv ("PCPROFILE_OUTPUT");
40
41 if (outfile != NULL && *outfile != '\0')
42 {
43 fd = open (outfile, O_RDWR | O_CREAT, 0666);
44
45 if (fd != -1)
46 {
47 uint32_t word;
48
49 active = 1;
50
51 /* Write a magic word which tells the reader about the byte
52 order and the size of the following entries. */
53 word = 0xdeb00000 | sizeof (void *);
54 if (TEMP_FAILURE_RETRY (write (fd, &word, 4)) != 4)
55 {
56 /* If even this fails we shouldn't try further. */
57 close (fd);
58 fd = -1;
59 active = 0;
60 }
61 }
62 }
63}
64
65
66static void
67__attribute__ ((destructor))
68uninstall (void)
69{
70 if (active)
71 close (fd);
72}
73
74
75void
76__cyg_profile_func_enter (void *this_fn, void *call_site)
77{
78 void *buf[2];
79
80 if (! active)
81 return;
82
83 /* Now write out the current position and that of the caller. We do
84 this now, and don't cache the because we want real-time output. */
85 buf[0] = this_fn;
86 buf[1] = call_site;
87
88 write (fd, buf, sizeof buf);
89}
90/* We don't handle entry and exit differently here. */
91strong_alias (__cyg_profile_func_enter, __cyg_profile_func_exit)
92