1 /*
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright © 2019 Keith Packard
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above
14 * copyright notice, this list of conditions and the following
15 * disclaimer in the documentation and/or other materials provided
16 * with the distribution.
17 *
18 * 3. Neither the name of the copyright holder nor the names of its
19 * contributors may be used to endorse or promote products derived
20 * from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
23 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
24 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
25 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
26 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
27 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
28 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
29 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
31 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
32 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
33 * OF THE POSSIBILITY OF SUCH DAMAGE.
34 */
35
36 #include "semihost-private.h"
37 #include <stdbool.h>
38 #include <string.h>
39
40 #define SH_EXT_NUM_BYTES ((SH_EXT_NUM + 7) >> 3)
41
42 static bool got_feature_bytes;
43 static uint8_t feature_bytes[SH_EXT_NUM_BYTES];
44
45 static const uint8_t fb_magic[4] = {
46 SHFB_MAGIC_0,
47 SHFB_MAGIC_1,
48 SHFB_MAGIC_2,
49 SHFB_MAGIC_3,
50 };
51
52 static void
get_features(void)53 get_features(void)
54 {
55 if (got_feature_bytes)
56 return;
57 got_feature_bytes = true;
58
59 int fd = sys_semihost_open(":semihosting-features", 0);
60 if (fd == -1)
61 return;
62
63 int len = sys_semihost_flen(fd);
64 if (len < (int) sizeof(fb_magic))
65 goto do_close;
66
67 uint8_t magic[sizeof (fb_magic)];
68 if (sys_semihost_read(fd, magic, sizeof (fb_magic)) != 0)
69 goto do_close;
70 if (memcmp(magic, fb_magic, sizeof (fb_magic)) != 0)
71 goto do_close;
72
73 int to_read = len - sizeof(fb_magic);
74 if (to_read > (int) sizeof(feature_bytes))
75 to_read = sizeof(feature_bytes);
76
77 (void) sys_semihost_read(fd, feature_bytes, to_read);
78 do_close:
79 sys_semihost_close(fd);
80 }
81
82 bool
sys_semihost_feature(uint8_t feature)83 sys_semihost_feature(uint8_t feature)
84 {
85 get_features();
86 uint8_t byte = (feature >> 3);
87 uint8_t bit = (feature & 7);
88 return (feature_bytes[byte] & (1 << bit)) != 0;
89 }
90
