1/* printf implementation for the dynamic loader.
2 Copyright (C) 1997-2024 Free Software Foundation, Inc.
3 Copyright The GNU Toolchain Authors.
4 This file is part of the GNU C Library.
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 <string.h>
21#if BUILD_PIE_DEFAULT
22# pragma GCC visibility push(hidden)
23#endif
24#include <_itoa.h>
25#include <assert.h>
26#include <dl-writev.h>
27#include <ldsodefs.h>
28#include <limits.h>
29#include <stdarg.h>
30#include <stdint.h>
31#include <stdlib.h>
32#include <sys/uio.h>
33#include <unistd.h>
34#include <intprops.h>
35
36/* The function might be called before the process is self-relocated. */
37static size_t
38_dl_debug_strlen (const char *s)
39{
40 const char *p = s;
41 for (; *s != '\0'; s++);
42 return s - p;
43}
44
45/* Bare-bones printf implementation. This function only knows about
46 the formats and flags needed and can handle only up to 64 stripes in
47 the output. */
48static void
49_dl_debug_vdprintf (int fd, int tag_p, const char *fmt, va_list arg)
50{
51# define NIOVMAX 64
52 struct iovec iov[NIOVMAX];
53 /* Maximum size for 'd', 'u', and 'x' including padding. */
54 enum { IFMTSIZE = INT_STRLEN_BOUND(void *) };
55 char ifmtbuf[NIOVMAX][IFMTSIZE];
56 int niov = 0;
57 pid_t pid = 0;
58 char pidbuf[12];
59
60 while (*fmt != '\0')
61 {
62 const char *startp = fmt;
63
64 if (tag_p > 0)
65 {
66 /* Generate the tag line once. It consists of the PID and a
67 colon followed by a tab. */
68 if (pid == 0)
69 {
70 char *p;
71 pid = __getpid ();
72 assert (pid >= 0 && sizeof (pid_t) <= 4);
73 p = _itoa (pid, &pidbuf[10], 10, 0);
74 while (p > pidbuf)
75 *--p = ' ';
76 pidbuf[10] = ':';
77 pidbuf[11] = '\t';
78 }
79
80 /* Append to the output. */
81 assert (niov < NIOVMAX);
82 iov[niov].iov_len = 12;
83 iov[niov++].iov_base = pidbuf;
84
85 /* No more tags until we see the next newline. */
86 tag_p = -1;
87 }
88
89 /* Skip everything except % and \n (if tags are needed). */
90 while (*fmt != '\0' && *fmt != '%' && (! tag_p || *fmt != '\n'))
91 ++fmt;
92
93 /* Append constant string. */
94 assert (niov < NIOVMAX);
95 if ((iov[niov].iov_len = fmt - startp) != 0)
96 iov[niov++].iov_base = (char *) startp;
97
98 if (*fmt == '%')
99 {
100 /* It is a format specifier. */
101 char fill = ' ';
102 int width = -1;
103 int prec = -1;
104#if LONG_MAX != INT_MAX
105 int long_mod = 0;
106#endif
107
108 /* Recognize zero-digit fill flag. */
109 if (*++fmt == '0')
110 {
111 fill = '0';
112 ++fmt;
113 }
114
115 /* See whether with comes from a parameter. Note that no other
116 way to specify the width is implemented. */
117 if (*fmt == '*')
118 {
119 width = va_arg (arg, int);
120 /* The maximum padding accepted is up to pointer size. */
121 assert (width < IFMTSIZE);
122 ++fmt;
123 }
124
125 /* Handle precision. */
126 if (*fmt == '.' && fmt[1] == '*')
127 {
128 prec = va_arg (arg, int);
129 fmt += 2;
130 }
131
132 /* Recognize the l modifier. It is only important on some
133 platforms where long and int have a different size. We
134 can use the same code for size_t. */
135 if (*fmt == 'l' || *fmt == 'z')
136 {
137#if LONG_MAX != INT_MAX
138 long_mod = 1;
139#endif
140 ++fmt;
141 }
142
143 switch (*fmt)
144 {
145 /* Integer formatting. */
146 case 'd':
147 case 'u':
148 case 'x':
149 {
150 /* We have to make a difference if long and int have a
151 different size. */
152#if LONG_MAX != INT_MAX
153 unsigned long int num = (long_mod
154 ? va_arg (arg, unsigned long int)
155 : va_arg (arg, unsigned int));
156#else
157 unsigned long int num = va_arg (arg, unsigned int);
158#endif
159 bool negative = false;
160 if (*fmt == 'd')
161 {
162#if LONG_MAX != INT_MAX
163 if (long_mod)
164 {
165 if ((long int) num < 0)
166 {
167 num = -num;
168 negative = true;
169 }
170 }
171 else
172 {
173 if ((int) num < 0)
174 {
175 num = -(unsigned int) num;
176 negative = true;
177 }
178 }
179#else
180 if ((int) num < 0)
181 {
182 num = -num;
183 negative = true;
184 }
185#endif
186 }
187
188 char *endp = &ifmtbuf[niov][IFMTSIZE];
189 char *cp = _itoa (num, endp, *fmt == 'x' ? 16 : 10, 0);
190
191 /* Pad to the width the user specified. */
192 if (width != -1)
193 while (endp - cp < width)
194 *--cp = fill;
195
196 if (negative)
197 *--cp = '-';
198
199 iov[niov].iov_base = cp;
200 iov[niov].iov_len = endp - cp;
201 ++niov;
202 }
203 break;
204
205 case 's':
206 /* Get the string argument. */
207 iov[niov].iov_base = va_arg (arg, char *);
208 iov[niov].iov_len = _dl_debug_strlen (s: iov[niov].iov_base);
209 if (prec != -1)
210 iov[niov].iov_len = MIN ((size_t) prec, iov[niov].iov_len);
211 ++niov;
212 break;
213
214 case '%':
215 iov[niov].iov_base = (void *) fmt;
216 iov[niov].iov_len = 1;
217 ++niov;
218 break;
219
220 default:
221 assert (! "invalid format specifier");
222 }
223 ++fmt;
224 }
225 else if (*fmt == '\n')
226 {
227 /* See whether we have to print a single newline character. */
228 if (fmt == startp)
229 {
230 iov[niov].iov_base = (char *) startp;
231 iov[niov++].iov_len = 1;
232 }
233 else
234 /* No, just add it to the rest of the string. */
235 ++iov[niov - 1].iov_len;
236
237 /* Next line, print a tag again. */
238 tag_p = 1;
239 ++fmt;
240 }
241 }
242
243 /* Finally write the result. */
244 _dl_writev (fd, iov, niov);
245}
246
247
248/* Write to debug file. */
249void
250_dl_debug_printf (const char *fmt, ...)
251{
252 va_list arg;
253
254 va_start (arg, fmt);
255 _dl_debug_vdprintf (GLRO(dl_debug_fd), tag_p: 1, fmt, arg);
256 va_end (arg);
257}
258
259
260/* Write to debug file but don't start with a tag. */
261void
262_dl_debug_printf_c (const char *fmt, ...)
263{
264 va_list arg;
265
266 va_start (arg, fmt);
267 _dl_debug_vdprintf (GLRO(dl_debug_fd), tag_p: -1, fmt, arg);
268 va_end (arg);
269}
270
271
272/* Write the given file descriptor. */
273void
274_dl_dprintf (int fd, const char *fmt, ...)
275{
276 va_list arg;
277
278 va_start (arg, fmt);
279 _dl_debug_vdprintf (fd, tag_p: 0, fmt, arg);
280 va_end (arg);
281}
282
283void
284_dl_printf (const char *fmt, ...)
285{
286 va_list arg;
287
288 va_start (arg, fmt);
289 _dl_debug_vdprintf (STDOUT_FILENO, tag_p: 0, fmt, arg);
290 va_end (arg);
291}
292
293void
294_dl_error_printf (const char *fmt, ...)
295{
296 va_list arg;
297
298 va_start (arg, fmt);
299 _dl_debug_vdprintf (STDERR_FILENO, tag_p: 0, fmt, arg);
300 va_end (arg);
301}
302
303void
304_dl_fatal_printf (const char *fmt, ...)
305{
306 va_list arg;
307
308 va_start (arg, fmt);
309 _dl_debug_vdprintf (STDERR_FILENO, tag_p: 0, fmt, arg);
310 va_end (arg);
311 _exit (127);
312}
313rtld_hidden_def (_dl_fatal_printf)
314

source code of glibc/elf/dl-printf.c