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b17c7ab3 TT |
1 | /* String reading |
2 | ||
213516ef | 3 | Copyright (C) 2022-2023 Free Software Foundation, Inc. |
b17c7ab3 TT |
4 | |
5 | This file is part of GDB. | |
6 | ||
7 | This program is free software; you can redistribute it and/or modify | |
8 | it under the terms of the GNU General Public License as published by | |
9 | the Free Software Foundation; either version 3 of the License, or | |
10 | (at your option) any later version. | |
11 | ||
12 | This program is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | GNU General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
18 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ | |
19 | ||
20 | #include "gdbsupport/common-defs.h" | |
21 | #include "target/target.h" | |
22 | ||
23 | /* Read LEN bytes of target memory at address MEMADDR, placing the | |
24 | results in GDB's memory at MYADDR. Returns a count of the bytes | |
25 | actually read, and optionally a target_xfer_status value in the | |
26 | location pointed to by ERRPTR if ERRPTR is non-null. */ | |
27 | ||
28 | static int | |
29 | partial_memory_read (CORE_ADDR memaddr, gdb_byte *myaddr, | |
30 | int len, int *errptr) | |
31 | { | |
32 | int nread; /* Number of bytes actually read. */ | |
33 | int errcode; /* Error from last read. */ | |
34 | ||
35 | /* First try a complete read. */ | |
36 | errcode = target_read_memory (memaddr, myaddr, len); | |
37 | if (errcode == 0) | |
38 | { | |
39 | /* Got it all. */ | |
40 | nread = len; | |
41 | } | |
42 | else | |
43 | { | |
44 | /* Loop, reading one byte at a time until we get as much as we can. */ | |
45 | for (errcode = 0, nread = 0; len > 0 && errcode == 0; nread++, len--) | |
46 | { | |
47 | errcode = target_read_memory (memaddr++, myaddr++, 1); | |
48 | } | |
49 | /* If an error, the last read was unsuccessful, so adjust count. */ | |
50 | if (errcode != 0) | |
51 | { | |
52 | nread--; | |
53 | } | |
54 | } | |
55 | if (errptr != NULL) | |
56 | { | |
57 | *errptr = errcode; | |
58 | } | |
59 | return (nread); | |
60 | } | |
61 | ||
62 | /* See target/target.h. */ | |
63 | ||
64 | int | |
65 | target_read_string (CORE_ADDR addr, int len, int width, | |
66 | unsigned int fetchlimit, | |
67 | gdb::unique_xmalloc_ptr<gdb_byte> *buffer, | |
68 | int *bytes_read) | |
69 | { | |
70 | int errcode; /* Errno returned from bad reads. */ | |
71 | unsigned int nfetch; /* Chars to fetch / chars fetched. */ | |
72 | gdb_byte *bufptr; /* Pointer to next available byte in | |
73 | buffer. */ | |
74 | ||
75 | /* Loop until we either have all the characters, or we encounter | |
76 | some error, such as bumping into the end of the address space. */ | |
77 | ||
78 | buffer->reset (nullptr); | |
79 | ||
80 | if (len > 0) | |
81 | { | |
82 | /* We want fetchlimit chars, so we might as well read them all in | |
83 | one operation. */ | |
84 | unsigned int fetchlen = std::min ((unsigned) len, fetchlimit); | |
85 | ||
86 | buffer->reset ((gdb_byte *) xmalloc (fetchlen * width)); | |
87 | bufptr = buffer->get (); | |
88 | ||
89 | nfetch = partial_memory_read (addr, bufptr, fetchlen * width, &errcode) | |
90 | / width; | |
91 | addr += nfetch * width; | |
92 | bufptr += nfetch * width; | |
93 | } | |
94 | else if (len == -1) | |
95 | { | |
96 | unsigned long bufsize = 0; | |
97 | unsigned int chunksize; /* Size of each fetch, in chars. */ | |
98 | int found_nul; /* Non-zero if we found the nul char. */ | |
99 | gdb_byte *limit; /* First location past end of fetch buffer. */ | |
100 | ||
101 | found_nul = 0; | |
102 | /* We are looking for a NUL terminator to end the fetching, so we | |
103 | might as well read in blocks that are large enough to be efficient, | |
104 | but not so large as to be slow if fetchlimit happens to be large. | |
105 | So we choose the minimum of 8 and fetchlimit. We used to use 200 | |
106 | instead of 8 but 200 is way too big for remote debugging over a | |
107 | serial line. */ | |
108 | chunksize = std::min (8u, fetchlimit); | |
109 | ||
110 | do | |
111 | { | |
112 | nfetch = std::min ((unsigned long) chunksize, fetchlimit - bufsize); | |
113 | ||
114 | if (*buffer == NULL) | |
115 | buffer->reset ((gdb_byte *) xmalloc (nfetch * width)); | |
116 | else | |
117 | buffer->reset ((gdb_byte *) xrealloc (buffer->release (), | |
118 | (nfetch + bufsize) * width)); | |
119 | ||
120 | bufptr = buffer->get () + bufsize * width; | |
121 | bufsize += nfetch; | |
122 | ||
123 | /* Read as much as we can. */ | |
124 | nfetch = partial_memory_read (addr, bufptr, nfetch * width, &errcode) | |
125 | / width; | |
126 | ||
127 | /* Scan this chunk for the null character that terminates the string | |
128 | to print. If found, we don't need to fetch any more. Note | |
129 | that bufptr is explicitly left pointing at the next character | |
130 | after the null character, or at the next character after the end | |
131 | of the buffer. */ | |
132 | ||
133 | limit = bufptr + nfetch * width; | |
134 | while (bufptr < limit) | |
135 | { | |
136 | bool found_nonzero = false; | |
137 | ||
138 | for (int i = 0; !found_nonzero && i < width; ++i) | |
139 | if (bufptr[i] != 0) | |
140 | found_nonzero = true; | |
141 | ||
142 | addr += width; | |
143 | bufptr += width; | |
144 | if (!found_nonzero) | |
145 | { | |
146 | /* We don't care about any error which happened after | |
147 | the NUL terminator. */ | |
148 | errcode = 0; | |
149 | found_nul = 1; | |
150 | break; | |
151 | } | |
152 | } | |
153 | } | |
154 | while (errcode == 0 /* no error */ | |
155 | && bufptr - buffer->get () < fetchlimit * width /* no overrun */ | |
156 | && !found_nul); /* haven't found NUL yet */ | |
157 | } | |
158 | else | |
159 | { /* Length of string is really 0! */ | |
160 | /* We always allocate *buffer. */ | |
161 | buffer->reset ((gdb_byte *) xmalloc (1)); | |
162 | bufptr = buffer->get (); | |
163 | errcode = 0; | |
164 | } | |
165 | ||
166 | /* bufptr and addr now point immediately beyond the last byte which we | |
167 | consider part of the string (including a '\0' which ends the string). */ | |
168 | *bytes_read = bufptr - buffer->get (); | |
169 | ||
170 | return errcode; | |
171 | } | |
172 | ||
173 | /* See target/target.h. */ | |
174 | ||
175 | gdb::unique_xmalloc_ptr<char> | |
176 | target_read_string (CORE_ADDR memaddr, int len, int *bytes_read) | |
177 | { | |
178 | gdb::unique_xmalloc_ptr<gdb_byte> buffer; | |
179 | ||
180 | int ignore; | |
181 | if (bytes_read == nullptr) | |
182 | bytes_read = &ignore; | |
183 | ||
184 | /* Note that the endian-ness does not matter here. */ | |
185 | int errcode = target_read_string (memaddr, -1, 1, len, &buffer, bytes_read); | |
186 | if (errcode != 0) | |
187 | return {}; | |
188 | ||
189 | return gdb::unique_xmalloc_ptr<char> ((char *) buffer.release ()); | |
190 | } |