backported more fixes from 256boss

[bootcensus] / src / part.c

diff --git a/src/part.c b/src/part.c
new file mode 100644 (file)
index 0000000..df007ee
--- /dev/null
+++ b/src/part.c
@@ -0,0 +1,158 @@
+/*
+pcboot - bootable PC demo/game kernel
+Copyright (C) 2018-2019  John Tsiombikas <nuclear@member.fsf.org>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY, without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+#include <stdio.h>
+#include "part.h"
+#include "boot.h"
+#include "bootdev.h"
+#include "ptype.h"
+
+struct part_record {
+       uint8_t stat;
+       uint8_t first_head, first_cyl, first_sect;
+       uint8_t type;
+       uint8_t last_head, last_cyl, last_sect;
+       uint32_t first_lba;
+       uint32_t nsect_lba;
+} __attribute__((packed));
+
+static int read_sector(int dev, uint64_t sidx);
+static const char *ptype_name(int type);
+
+static unsigned char sectdata[512];
+
+#define BOOTSIG_OFFS   510
+#define PTABLE_OFFS            0x1be
+
+#define BOOTSIG                        0xaa55
+
+#define IS_MBR                 (sidx == 0)
+#define IS_FIRST_EBR   (!IS_MBR && (first_ebr_offs == 0))
+
+int read_partitions(int dev, struct partition *ptab, int ptabsz)
+{
+       int i, num_rec, nparts = 0;
+       int num_bootrec = 0;
+       struct partition *part = ptab;
+       struct part_record *prec;
+       uint64_t sidx = 0;
+       uint64_t first_ebr_offs = 0;
+
+       if(ptabsz <= 0) {
+               ptab = 0;
+       }
+
+       do {
+               if(IS_FIRST_EBR) {
+                       first_ebr_offs = sidx;
+               }
+
+               if(read_sector(dev, sidx) == -1) {
+                       printf("failed to read sector %llu\n", (unsigned long long)sidx);
+                       return -1;
+               }
+               if(*(uint16_t*)(sectdata + BOOTSIG_OFFS) != BOOTSIG) {
+                       printf("invalid partitionm table, sector %llu has no magic\n", (unsigned long long)sidx);
+                       return -1;
+               }
+               prec = (struct part_record*)(sectdata + PTABLE_OFFS);
+
+               /* MBR has 4 records, EBRs have 2 */
+               num_rec = IS_MBR ? 4 : 2;
+
+               for(i=0; i<num_rec; i++) {
+                       /* ignore empty partitions in the MBR, stop on empty partitions in an EBR */
+                       if(prec[i].type == 0) {
+                               if(num_bootrec > 0) {
+                                       sidx = 0;
+                                       break;
+                               }
+                               continue;
+                       }
+
+                       /* ignore extended partitions and setup sector index to read the
+                        * next logical partition.
+                        */
+                       if(prec[i].type == PTYPE_EXT || prec[i].type == PTYPE_EXT_LBA) {
+                               /* all EBR start fields are relative to the first EBR offset */
+                               sidx = first_ebr_offs + prec[i].first_lba;
+                               continue;
+                       }
+
+                       /* found a proper partition */
+                       nparts++;
+
+                       if(ptab) {
+                               part->attr = prec[i].type;
+
+                               if(prec[i].stat & 0x80) {
+                                       part->attr |= PART_ACT_BIT;
+                               }
+                               if(IS_MBR) {
+                                       part->attr |= PART_PRIM_BIT;
+                               }
+                               part->start_sect = prec[i].first_lba + first_ebr_offs;
+                               part->size_sect = prec[i].nsect_lba;
+                               part++;
+                       }
+               }
+
+               num_bootrec++;
+       } while(sidx > 0 && (!ptab || nparts < ptabsz));
+
+       return nparts;
+}
+
+void print_partition_table(struct partition *ptab, int npart)
+{
+       int i;
+       struct partition *p = ptab;
+
+       printf("Found %d partitions\n", npart);
+       for(i=0; i<npart; i++) {
+               printf("%d%c ", i, PART_IS_ACT(p->attr) ? '*' : ' ');
+               printf("(%s) %-20s ", PART_IS_PRIM(p->attr) ? "pri" : "log", ptype_name(PART_TYPE(p->attr)));
+               printf("start: %-10llu ", (unsigned long long)p->start_sect);
+               printf("size: %-10llu\n", (unsigned long long)p->size_sect);
+               p++;
+       }
+}
+
+static int read_sector(int dev, uint64_t sidx)
+{
+       if(dev == -1 || dev == boot_drive_number) {
+               if(bdev_read_sect(sidx, sectdata) == -1) {
+                       return -1;
+               }
+               return 0;
+       }
+
+       printf("BUG: reading partitions of drives other than the boot drive not implemented yet\n");
+       return -1;
+}
+
+static const char *ptype_name(int type)
+{
+       int i;
+
+       for(i=0; i<PTYPES_SIZE; i++) {
+               if(partypes[i].type == type) {
+                       return partypes[i].name;
+               }
+       }
+       return "unknown";
+}