ref: 3544c39d3a383c07c4b8d452b6bb25ba639e042f
parent: 14510c867d15cbd0de68319b428b734a301317e0
author: ment <[email protected]>
date: Wed Apr 27 20:05:36 EDT 2011
unix tool for making bootable plan9 disks.
--- /dev/null
+++ b/sys/src/cmd/unix/mbrfix.c
@@ -1,0 +1,196 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <sys/types.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+
+typedef unsigned char uchar;
+typedef unsigned int uint;
+typedef unsigned long long vlong;
+
+
+enum {+ Sectsz = 0x200,
+ Psectsz = 11,
+ Pclustsc = 13,
+ Presvd = 14,
+ Pnumfat = 16,
+ Pfatsz = 22,
+ Pfatsz32 = 36,
+ Pvolid = 67,
+};
+
+int
+readn(int f, void *av, int n)
+{+ char *a;
+ int m, t;
+ a = av;
+ t = 0;
+ while(t < n){+ m = read(f, a+t, n-t);
+ if(m <= 0){+ if(t == 0)
+ return m;
+ break;
+ }
+ t += m;
+ }
+ return t;
+}
+
+void
+sysfatal(char *fmt, ...)
+{+ va_list va;
+ va_start(va, fmt);
+ vfprintf(stderr, fmt, va);
+ va_end(va);
+ fprintf(stderr, "\n");
+ exit(1);
+}
+
+void
+readsect(int fd, uint n, void *data)
+{+ loff_t off;
+
+ off = (loff_t) n * Sectsz;
+ if(llseek(fd, off, SEEK_SET) != off)
+ sysfatal("seek to sector 0x%x failed", n);+ if(readn(fd, data, Sectsz) != Sectsz)
+ sysfatal("short read: %m");+}
+
+void
+writesect(int fd, uint n, void *data)
+{+ loff_t off;
+
+ off = (loff_t) n * Sectsz;
+ if(llseek(fd, off, SEEK_SET) != off)
+ sysfatal("seek to sector 0x%x failed", n);+ if(write(fd, data, Sectsz) != Sectsz)
+ sysfatal("short write: %m");+}
+
+uint
+getulong(uchar *s)
+{+ return s[0] | (s[1] << 8) | (s[2] << 16) | (s[3] << 24);
+}
+
+void
+putulong(uchar *s, uint n)
+{+ *s++ = n & 0xff;
+ *s++ = (n >> 8) & 0xff;
+ *s++ = (n >> 16) & 0xff;
+ *s++ = (n >> 24) & 0xff;
+}
+
+
+uint
+getushort(uchar *s)
+{+ return s[0] | (s[1] << 8);
+}
+
+int
+checksig(uchar *s)
+{+ return s[0x1fe] == 0x55 && s[0x1ff] == 0xaa;
+}
+
+void
+fixpbs(uchar *pbs, uchar *pbs9, uint lba)
+{+ uint a;
+ uint fatsz, resvd, numfat;
+
+ numfat = pbs[Pnumfat];
+ fatsz = getushort(&pbs[Pfatsz]);
+ if(fatsz == 0)
+ fatsz = getulong(&pbs[Pfatsz32]);
+ resvd = getushort(&pbs[Presvd]);
+
+ a = pbs9[1] + 2;
+ memcpy(pbs, pbs9, 3);
+ memcpy(pbs+a, pbs9+a, Sectsz-a-2);
+ a = lba + numfat * fatsz + resvd;
+ printf("Xroot=%x\n", a);+ putulong(&pbs[Pvolid], a);
+}
+
+
+int
+main(int argc, char *argv[])
+{+ int dev, fd, i;
+ uchar mbr9[Sectsz], pbs9[Sectsz];
+ uchar mbr[Sectsz], pbs[Sectsz];
+ uint lba;
+ int part, want;
+ char *mbrfn, *pbsfn, *devfn;
+
+ if(argc < 4)
+ sysfatal("usage: <device> <mbrfile> <pbsfile> [part]");+ devfn = argv[1];
+ mbrfn = argv[2];
+ pbsfn = argv[3];
+ want = argc >= 5 ? atoi(argv[4]) : -1;
+ part = -1;
+
+ dev = open(devfn, O_RDWR);
+ if(dev < 0)
+ sysfatal("%s: %m", devfn);+
+ if((fd = open(mbrfn, O_RDONLY)) < 0)
+ sysfatal("%s: %m", mbrfn);+ if(readn(fd, mbr9, Sectsz) < 3)
+ sysfatal("%s: too short", mbrfn);+ close(fd);
+
+ fd = open(pbsfn, O_RDONLY);
+ if(fd < 0)
+ sysfatal("%s: %m", pbsfn);+ if(readn(fd, pbs9, Sectsz) < 3)
+ sysfatal("%s: too short", pbsfn);+ if(pbs9[0] != 0xeb)
+ sysfatal("first byte of pbs not a short jump");+ close(fd);
+
+ readsect(dev, 0, mbr);
+ if(!checksig(mbr))
+ sysfatal("sector 0 is missing signature");+ for(i=0; i<4; i++){+ if(mbr[0x1be + i*16] == 0x80 && (part == -1 || i == want))
+ part = i;
+ }
+ if(part == -1)
+ sysfatal("no bootable partitions found");+ if(want != -1 && part != want)
+ sysfatal("partition %d is not bootable", want);+
+ lba = getulong(&mbr[0x1be + part*16 + 8]);
+ if(lba == 0)
+ sysfatal("partition %d has zero LBA", part);+
+ readsect(dev, lba, pbs);
+ if(!checksig(pbs))
+ sysfatal("partition %d (LBA=0x%x) is missing signaure", part, lba);+ if(getushort(&pbs[Psectsz]) != 512)
+ sysfatal("sector size not 512");+
+ printf("using partition %d, LBA=0x%x\n", part, lba);+ memcpy(mbr, mbr9, 446);
+ fixpbs(pbs, pbs9, lba);
+
+ writesect(dev, 0, mbr);
+ writesect(dev, lba, pbs);
+
+ close(dev);
+ return 0;
+}