ref: b502a62da2ec6058923db94f87ecc2d29db2fa77
dir: /os/boot.original/puma/dosboot.c/
#include "u.h" #include "lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "dosfs.h" extern char *premature; /* * predeclared */ static void bootdump(Dosboot*); static void setname(Dosfile*, char*); long dosreadseg(Dosfile*, long, long); /* * debugging */ #define chatty 1 #define chat if(chatty)print /* * block io buffers */ enum { Nbio= 16, }; typedef struct Clustbuf Clustbuf; struct Clustbuf { int age; long sector; uchar *iobuf; Dos *dos; int size; }; Clustbuf bio[Nbio]; /* * get an io block from an io buffer */ Clustbuf* getclust(Dos *dos, long sector) { Clustbuf *p, *oldest; int size; chat("getclust @ %d\n", sector); /* * if we have it, just return it */ for(p = bio; p < &bio[Nbio]; p++){ if(sector == p->sector && dos == p->dos){ p->age = m->ticks; chat("getclust %d in cache\n", sector); return p; } } /* * otherwise, reuse the oldest entry */ oldest = bio; for(p = &bio[1]; p < &bio[Nbio]; p++){ if(p->age <= oldest->age) oldest = p; } p = oldest; /* * make sure the buffer is big enough */ size = dos->clustsize*dos->sectsize; if(p->iobuf==0 || p->size < size) p->iobuf = ialloc(size, 0); p->size = size; /* * read in the cluster */ chat("getclust addr %d\n", (sector+dos->start)*dos->sectsize); if((*dos->seek)(dos->dev, (sector+dos->start)*dos->sectsize) < 0){ chat("can't seek block\n"); return 0; } if((*dos->read)(dos->dev, p->iobuf, size) != size){ chat("can't read block\n"); return 0; } p->age = m->ticks; p->dos = dos; p->sector = sector; chat("getclust %d read\n", sector); return p; } /* * walk the fat one level ( n is a current cluster number ). * return the new cluster number or -1 if no more. */ static long fatwalk(Dos *dos, int n) { ulong k, sect; Clustbuf *p; int o; chat("fatwalk %d\n", n); if(n < 2 || n >= dos->fatclusters) return -1; switch(dos->fatbits){ case 12: k = (3*n)/2; break; case 16: k = 2*n; break; default: return -1; } if(k >= dos->fatsize*dos->sectsize) panic("getfat"); sect = (k/(dos->sectsize*dos->clustsize))*dos->clustsize + dos->fataddr; o = k%(dos->sectsize*dos->clustsize); p = getclust(dos, sect); k = p->iobuf[o++]; if(o >= dos->sectsize*dos->clustsize){ p = getclust(dos, sect+dos->clustsize); o = 0; } k |= p->iobuf[o]<<8; if(dos->fatbits == 12){ if(n&1) k >>= 4; else k &= 0xfff; if(k >= 0xff8) k |= 0xf000; } k = k < 0xfff8 ? k : -1; chat("fatwalk %d -> %d\n", n, k); return k; } /* * map a file's logical cluster address to a physical sector address */ static long fileaddr(Dosfile *fp, long ltarget) { Dos *dos = fp->dos; long l; long p; chat("fileaddr %8.8s %d\n", fp->name, ltarget); /* * root directory is contiguous and easy */ if(fp->pstart == 0){ if(ltarget*dos->sectsize*dos->clustsize >= dos->rootsize*sizeof(Dosdir)) return -1; l = dos->rootaddr + ltarget*dos->clustsize; chat("fileaddr %d -> %d\n", ltarget, l); return l; } /* * anything else requires a walk through the fat */ if(ltarget >= fp->lcurrent && fp->pcurrent){ /* start at the currrent point */ l = fp->lcurrent; p = fp->pcurrent; } else { /* go back to the beginning */ l = 0; p = fp->pstart; } while(l != ltarget){ /* walk the fat */ p = fatwalk(dos, p); if(p < 0) return -1; l++; } fp->lcurrent = l; fp->pcurrent = p; /* * clusters start at 2 instead of 0 (why? - presotto) */ l = dos->dataaddr + (p-2)*dos->clustsize; chat("fileaddr %d -> %d\n", ltarget, l); return l; } /* * read from a dos file */ long dosread(Dosfile *fp, void *a, long n) { long addr; long rv; int i; int off; Clustbuf *p; uchar *from, *to; if((fp->attr & DDIR) == 0){ if(fp->offset >= fp->length) return 0; if(fp->offset+n > fp->length) n = fp->length - fp->offset; } to = a; for(rv = 0; rv < n; rv+=i){ /* * read the cluster */ addr = fileaddr(fp, fp->offset/fp->dos->clustbytes); if(addr < 0) return -1; p = getclust(fp->dos, addr); if(p == 0) return -1; /* * copy the bytes we need */ off = fp->offset % fp->dos->clustbytes; from = &p->iobuf[off]; i = n - rv; if(i > fp->dos->clustbytes - off) i = fp->dos->clustbytes - off; memmove(to, from, i); to += i; fp->offset += i; } return rv; } /* * walk a directory returns * -1 if something went wrong * 0 if not found * 1 if found */ int doswalk(Dosfile *file, char *name) { Dosdir d; long n; if((file->attr & DDIR) == 0){ chat("walking non-directory!\n"); return -1; } setname(file, name); file->offset = 0; /* start at the beginning */ while((n = dosread(file, &d, sizeof(d))) == sizeof(d)){ chat("comparing to %8.8s.%3.3s\n", d.name, d.ext); if(memcmp(file->name, d.name, sizeof(d.name)) != 0) continue; if(memcmp(file->ext, d.ext, sizeof(d.ext)) != 0) continue; if(d.attr & DVLABEL){ chat("%8.8s.%3.3s is a LABEL\n", d.name, d.ext); continue; } file->attr = d.attr; file->pstart = GSHORT(d.start); file->length = GLONG(d.length); file->pcurrent = 0; file->lcurrent = 0; file->offset = 0; return 1; } return n >= 0 ? 0 : -1; } /* * instructions that boot blocks can start with */ #define JMPSHORT 0xeb #define JMPNEAR 0xe9 /* * read dos file system properties */ int dosinit(Dos *dos, int start, int ishard) { Dosboot *b; int i; Clustbuf *p; Dospart *dp; ulong mbroffset, offset; /* defaults till we know better */ dos->start = start; dos->sectsize = 512; dos->clustsize = 1; mbroffset = 0; dmddo: /* get first sector */ p = getclust(dos, mbroffset); if(p == 0){ chat("can't read boot block\n"); return -1; } /* * If it's a hard disc then look for an MBR and pick either an * active partition or the FAT with the lowest starting LBA. * Things are tricky because we could be pointing to, amongst others: * 1) a floppy BPB; * 2) a hard disc MBR; * 3) a hard disc extended partition table; * 4) a logical drive on a hard disc; * 5) a disc-manager boot block. * They all have the same magic at the end of the block. */ if(p->iobuf[0x1FE] != 0x55 || p->iobuf[0x1FF] != 0xAA) { chat("not DOS\n"); return -1; } p->dos = 0; b = (Dosboot *)p->iobuf; if(ishard && b->mediadesc != 0xF8){ dp = (Dospart*)&p->iobuf[0x1BE]; offset = 0xFFFFFFFF; for(i = 0; i < 4; i++, dp++){ if(dp->type == DMDDO){ mbroffset = 63; goto dmddo; } if(dp->type != FAT12 && dp->type != FAT16 && dp->type != FATHUGE) continue; if(dp->flag & 0x80){ offset = GLONG(dp->start); break; } if(GLONG(dp->start) < offset) offset = GLONG(dp->start); } if(i != 4 || offset != 0xFFFFFFFF){ dos->start = mbroffset+offset; p = getclust(dos, 0); if(p == 0 || p->iobuf[0x1FE] != 0x55 || p->iobuf[0x1FF] != 0xAA) return -1; } p->dos = 0; } b = (Dosboot *)p->iobuf; if(b->magic[0] != JMPNEAR && (b->magic[0] != JMPSHORT || b->magic[2] != 0x90)){ chat("no dos file system\n"); return -1; } if(chatty) bootdump(b); /* * determine the systems' wondersous properties */ dos->sectsize = GSHORT(b->sectsize); dos->clustsize = b->clustsize; dos->clustbytes = dos->sectsize*dos->clustsize; dos->nresrv = GSHORT(b->nresrv); dos->nfats = b->nfats; dos->rootsize = GSHORT(b->rootsize); dos->volsize = GSHORT(b->volsize); if(dos->volsize == 0) dos->volsize = GLONG(b->bigvolsize); dos->mediadesc = b->mediadesc; dos->fatsize = GSHORT(b->fatsize); dos->fataddr = dos->nresrv; dos->rootaddr = dos->fataddr + dos->nfats*dos->fatsize; i = dos->rootsize*sizeof(Dosdir) + dos->sectsize - 1; i = i/dos->sectsize; dos->dataaddr = dos->rootaddr + i; dos->fatclusters = 2+(dos->volsize - dos->dataaddr)/dos->clustsize; if(dos->fatclusters < 4087) dos->fatbits = 12; else dos->fatbits = 16; dos->freeptr = 2; /* * set up the root */ dos->root.dos = dos; dos->root.pstart = 0; dos->root.pcurrent = dos->root.lcurrent = 0; dos->root.offset = 0; dos->root.attr = DDIR; dos->root.length = dos->rootsize*sizeof(Dosdir); return 0; } static void bootdump(Dosboot *b) { if(chatty == 0) return; print("magic: 0x%2.2x 0x%2.2x 0x%2.2x\n", b->magic[0], b->magic[1], b->magic[2]); print("version: \"%8.8s\"\n", b->version); print("sectsize: %d\n", GSHORT(b->sectsize)); print("allocsize: %d\n", b->clustsize); print("nresrv: %d\n", GSHORT(b->nresrv)); print("nfats: %d\n", b->nfats); print("rootsize: %d\n", GSHORT(b->rootsize)); print("volsize: %d\n", GSHORT(b->volsize)); print("mediadesc: 0x%2.2x\n", b->mediadesc); print("fatsize: %d\n", GSHORT(b->fatsize)); print("trksize: %d\n", GSHORT(b->trksize)); print("nheads: %d\n", GSHORT(b->nheads)); print("nhidden: %d\n", GLONG(b->nhidden)); print("bigvolsize: %d\n", GLONG(b->bigvolsize)); print("driveno: %d\n", b->driveno); print("reserved0: 0x%2.2x\n", b->reserved0); print("bootsig: 0x%2.2x\n", b->bootsig); print("volid: 0x%8.8x\n", GLONG(b->volid)); print("label: \"%11.11s\"\n", b->label); } /* * grab next element from a path, return the pointer to unprocessed portion of * path. */ static char * nextelem(char *path, char *elem) { int i; while(*path == '/') path++; if(*path==0 || *path==' ') return 0; for(i=0; *path!='\0' && *path!='/' && *path!=' '; i++){ if(i==28){ print("name component too long\n"); return 0; } *elem++ = *path++; } *elem = '\0'; return path; } int dosstat(Dos *dos, char *path, Dosfile *f) { char element[NAMELEN]; *f = dos->root; while(path = nextelem(path, element)){ switch(doswalk(f, element)){ case -1: return -1; case 0: return 0; } } return 1; } /* * boot */ int dosboot(Dos *dos, char *path) { Dosfile file; long n; long addr; Exec *ep; void (*b)(void); switch(dosstat(dos, path, &file)){ case -1: print("error walking to %s\n", path); return -1; case 0: print("%s not found\n", path); return -1; case 1: print("found %8.8s.%3.3s attr 0x%ux start 0x%lux len %d\n", file.name, file.ext, file.attr, file.pstart, file.length); break; } /* * read header */ ep = (Exec*)ialloc(sizeof(Exec), 0); n = sizeof(Exec); if(dosreadseg(&file, n, (ulong) ep) != n){ print(premature); return -1; } if(GLLONG(ep->magic) != E_MAGIC){ print("bad magic 0x%lux not a plan 9 executable!\n", GLLONG(ep->magic)); return -1; } /* * read text */ addr = PADDR(GLLONG(ep->entry)); n = GLLONG(ep->text); print("+%d", n); if(dosreadseg(&file, n, addr) != n){ print(premature); return -1; } /* * read data (starts at first page after kernel) */ addr = PGROUND(addr+n); n = GLLONG(ep->data); print("+%d", n); if(dosreadseg(&file, n, addr) != n){ print(premature); return -1; } /* * bss and entry point */ print("+%d\nstart at 0x%lux\n", GLLONG(ep->bss), GLLONG(ep->entry)); /* * Go to new code. It's up to the program to get its PC relocated to * the right place. */ b = (void (*)(void))(PADDR(GLLONG(ep->entry))); (*b)(); return 0; } /* * read in a segment */ long dosreadseg(Dosfile *fp, long len, long addr) { char *a; long n, sofar; a = (char *)addr; for(sofar = 0; sofar < len; sofar += n){ n = 8*1024; if(len - sofar < n) n = len - sofar; n = dosread(fp, a + sofar, n); if(n <= 0) break; print("."); } return sofar; } /* * set up a dos file name */ static void setname(Dosfile *fp, char *from) { char *to; to = fp->name; for(; *from && to-fp->name < 8; from++, to++){ if(*from == '.'){ from++; break; } if(*from >= 'a' && *from <= 'z') *to = *from + 'A' - 'a'; else *to = *from; } while(to - fp->name < 8) *to++ = ' '; to = fp->ext; for(; *from && to-fp->ext < 3; from++, to++){ if(*from >= 'a' && *from <= 'z') *to = *from + 'A' - 'a'; else *to = *from; } while(to-fp->ext < 3) *to++ = ' '; chat("name is %8.8s %3.3s\n", fp->name, fp->ext); }