mirror of https://gitlab.com/nakst/essence
56 lines
2.3 KiB
C++
56 lines
2.3 KiB
C++
typedef struct MBRPartition {
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uint32_t offset, count;
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bool present;
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} MBRPartition;
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bool MBRGetPartitions(uint8_t *firstBlock, EsFileOffset sectorCount, MBRPartition *partitions) {
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if (firstBlock[510] != 0x55 || firstBlock[511] != 0xAA) {
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return false;
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}
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#ifdef KERNEL
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KernelLog(LOG_INFO, "FS", "probing MBR", "First sector on device looks like an MBR...\n");
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#endif
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for (uintptr_t i = 0; i < 4; i++) {
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if (!firstBlock[4 + 0x1BE + i * 0x10]) {
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partitions[i].present = false;
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continue;
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}
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partitions[i].offset =
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((uint32_t) firstBlock[0x1BE + i * 0x10 + 8 ] << 0)
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+ ((uint32_t) firstBlock[0x1BE + i * 0x10 + 9 ] << 8)
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+ ((uint32_t) firstBlock[0x1BE + i * 0x10 + 10] << 16)
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+ ((uint32_t) firstBlock[0x1BE + i * 0x10 + 11] << 24);
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partitions[i].count =
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((uint32_t) firstBlock[0x1BE + i * 0x10 + 12] << 0)
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+ ((uint32_t) firstBlock[0x1BE + i * 0x10 + 13] << 8)
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+ ((uint32_t) firstBlock[0x1BE + i * 0x10 + 14] << 16)
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+ ((uint32_t) firstBlock[0x1BE + i * 0x10 + 15] << 24);
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partitions[i].present = true;
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if (partitions[i].offset > sectorCount || partitions[i].count > sectorCount - partitions[i].offset || partitions[i].count < 32) {
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#ifdef KERNEL
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KernelLog(LOG_INFO, "FS", "invalid MBR", "Partition %d has offset %d and count %d, which is invalid. Ignoring the rest of the MBR...\n",
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i, partitions[i].offset, partitions[i].count);
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#endif
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return false;
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}
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}
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return true;
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}
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void MBRFixPartition(uint32_t *partitions) {
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uint32_t headsPerCylinder = 256, sectorsPerTrack = 63;
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uint32_t partitionOffsetCylinder = (partitions[2] / sectorsPerTrack) / headsPerCylinder;
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uint32_t partitionOffsetHead = (partitions[2] / sectorsPerTrack) % headsPerCylinder;
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uint32_t partitionOffsetSector = (partitions[2] % sectorsPerTrack) + 1;
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uint32_t partitionSizeCylinder = (partitions[3] / sectorsPerTrack) / headsPerCylinder;
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uint32_t partitionSizeHead = (partitions[3] / sectorsPerTrack) % headsPerCylinder;
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uint32_t partitionSizeSector = (partitions[3] % sectorsPerTrack) + 1;
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partitions[0] |= (partitionOffsetHead << 8) | (partitionOffsetSector << 16) | (partitionOffsetCylinder << 24) | ((partitionOffsetCylinder >> 8) << 16);
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partitions[1] |= (partitionSizeHead << 8) | (partitionSizeSector << 16) | (partitionSizeCylinder << 24) | ((partitionSizeCylinder >> 8) << 16);
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}
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