2 * Copyright 2015 Toomas Soome <tsoome@me.com>
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23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * Chain loader to load BIOS boot block either from MBR or PBR.
30 * Note the boot block location 0000:7c000 conflicts with loader, so we need to
31 * read in to temporary space and relocate on exec, when btx is stopped.
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
38 #include <sys/param.h>
39 #include <sys/linker.h>
40 #include <sys/diskmbr.h>
42 #include "bootstrap.h"
43 #include "libi386/libi386.h"
47 * The MBR/VBR is located in first sector of disk/partition.
48 * Read 512B to temporary location and set up relocation. Then
51 #define SECTOR_SIZE (512)
53 COMMAND_SET(chain, "chain", "chain load boot block from device", command_chain);
56 command_chain(int argc, char *argv[])
58 int fd, len, size = SECTOR_SIZE;
60 vm_offset_t mem = 0x100000;
61 struct i386_devdesc *rootdev;
64 command_errmsg = "no device or file name specified";
68 command_errmsg = "invalid trailing arguments";
72 fd = open(argv[1], O_RDONLY);
74 command_errmsg = "open failed";
78 len = strlen(argv[1]);
79 if (argv[1][len-1] != ':') {
80 if (fstat(fd, &st) == -1) {
81 command_errmsg = "stat failed";
86 } else if (strncmp(argv[1], "disk", 4) != 0) {
87 command_errmsg = "can only use disk device";
92 i386_getdev((void **)(&rootdev), argv[1], NULL);
93 if (rootdev == NULL) {
94 command_errmsg = "can't determine root device";
99 if (archsw.arch_readin(fd, mem, size) != size) {
100 command_errmsg = "failed to read disk";
106 if (argv[1][len-1] == ':' &&
107 *((uint16_t *)PTOV(mem + DOSMAGICOFFSET)) != DOSMAGIC) {
108 command_errmsg = "wrong magic";
112 relocater_data[0].src = mem;
113 relocater_data[0].dest = 0x7C00;
114 relocater_data[0].size = size;
116 relocator_edx = bd_unit2bios(rootdev->dd.d_unit);
117 relocator_esi = relocater_size;
124 relocator_sp = 0x7C00;
125 relocator_ip = 0x7C00;
126 relocator_a20_enabled = 0;
128 i386_copyin(relocater, 0x600, relocater_size);
132 __exec((void *)0x600);
134 panic("exec returned");
135 return (CMD_ERROR); /* not reached */