1 /* ----------------------------------------------------------------------- *
2 *
3 * Copyright 2009 Pierre-Alexandre Meyer
4 *
5 * Some parts borrowed from chain.c32:
6 *
7 * Copyright 2003-2009 H. Peter Anvin - All Rights Reserved
8 * Copyright 2009 Intel Corporation; author: H. Peter Anvin
9 *
10 * This file is part of Syslinux, and is made available under
11 * the terms of the GNU General Public License version 2.
12 *
13 * ----------------------------------------------------------------------- */
14
15 #include <com32.h>
16 #include <stdlib.h>
17 #include <string.h>
18
19 #include <disk/errno_disk.h>
20 #include <disk/geom.h>
21 #include <disk/read.h>
22 #include <disk/util.h>
23 #include <disk/common.h>
24
25 /*
26 * TODO: implement file descriptors to cache metadata (geometry, ...)
27 */
28
29 /**
30 * read_mbr - return a pointer to a malloced buffer containing the mbr
31 * @drive: Drive number
32 * @buf: Pre-allocated buffer for output
33 *
34 * Return the number of sectors read on success or -1 on failure.
35 * errno_disk contains the error number.
36 **/
read_mbr(int drive,void * buf)37 int read_mbr(int drive, void *buf)
38 {
39 struct driveinfo drive_info;
40 drive_info.disk = drive;
41
42 /* MBR: lba = 0, 1 sector */
43 return read_sectors(&drive_info, buf, 0, 1);
44 }
45
46 /**
47 * dev_read - read from a drive
48 * @drive: Drive number
49 * @buf: Pre-allocated buffer for output
50 * @lba: Position to start reading from
51 * @sectors: Number of sectors to read
52 *
53 * High-level routine to read from a hard drive.
54 * Return the number of sectors read on success or -1 on failure.
55 * errno_disk contains the error number.
56 **/
dev_read(int drive,void * buf,unsigned int lba,int sectors)57 int dev_read(int drive, void *buf, unsigned int lba, int sectors)
58 {
59 struct driveinfo drive_info;
60 drive_info.disk = drive;
61
62 return read_sectors(&drive_info, buf, lba, sectors);
63 }
64
65 /**
66 * read_sectors - read several sectors from disk
67 * @drive_info: driveinfo struct describing the disk
68 * @data: Pre-allocated buffer for output
69 * @lba: Position to read
70 * @sectors: Number of sectors to read
71 *
72 * Return the number of sectors read on success or -1 on failure.
73 * errno_disk contains the error number.
74 **/
read_sectors(struct driveinfo * drive_info,void * data,const unsigned int lba,const int sectors)75 int read_sectors(struct driveinfo *drive_info, void *data,
76 const unsigned int lba, const int sectors)
77 {
78 com32sys_t inreg, outreg;
79 struct ebios_dapa *dapa;
80 void *buf;
81 char *bufp = data;
82 int rv = -1;
83
84 if (get_drive_parameters(drive_info) == -1)
85 return -1;
86
87 buf = lmalloc(sectors * SECTOR);
88 if (!buf)
89 return -1;
90
91 dapa = lmalloc(sizeof(*dapa));
92 if (!dapa)
93 goto fail;
94
95 memset(&inreg, 0, sizeof inreg);
96
97 if (drive_info->ebios) {
98 dapa->len = sizeof(*dapa);
99 dapa->count = sectors;
100 dapa->off = OFFS(buf);
101 dapa->seg = SEG(buf);
102 dapa->lba = lba;
103
104 inreg.esi.w[0] = OFFS(dapa);
105 inreg.ds = SEG(dapa);
106 inreg.edx.b[0] = drive_info->disk;
107 inreg.eax.b[1] = 0x42; /* Extended read */
108 } else {
109 unsigned int c, h, s;
110
111 if (!drive_info->cbios) { // XXX errno
112 /* We failed to get the geometry */
113 if (lba)
114 goto fail; /* Can only read MBR */
115
116 s = 1;
117 h = 0;
118 c = 0;
119 } else
120 lba_to_chs(drive_info, lba, &s, &h, &c);
121
122 // XXX errno
123 if (s > 63 || h > 256 || c > 1023)
124 goto fail;
125
126 inreg.eax.w[0] = 0x0201; /* Read one sector */
127 inreg.ecx.b[1] = c & 0xff;
128 inreg.ecx.b[0] = s + (c >> 6);
129 inreg.edx.b[1] = h;
130 inreg.edx.b[0] = drive_info->disk;
131 inreg.ebx.w[0] = OFFS(buf);
132 inreg.es = SEG(buf);
133 }
134
135 /* Perform the read */
136 if (int13_retry(&inreg, &outreg)) {
137 errno_disk = outreg.eax.b[1];
138 goto fail; /* Give up */
139 }
140
141 memcpy(bufp, buf, sectors * SECTOR);
142 rv = sectors;
143
144 fail:
145 lfree(dapa);
146 lfree(buf);
147 return rv;
148 }
149