Hi,
mark3094 wrote:
I have found that if the kernel is larger than 40KB, it will not fit into the real mode segment that I am using as the INT 13 buffer.
If the kernel is larger than 64 KiB, then you have to split it into multiple reads (where each read is less than 64 KiB). If the kernel is larger than about 600 KiB (e.g. Linux is typically about 5 MiB) then you need a loop that reads (up to) 64 KiB then copies it somewhere else (e.g. to 0x00100000).
Also, for FAT32 the file may be fragmented, and you'd have to deal with that too.
The simplest way would be something like:
Code:
while(not_all_loadeed) {
find_next_cluster();
read_cluster_into_buffer();
copy_cluster_to_memory_above_0x00100000();
}
find_next_cluster();
read_cluster_into_buffer();
copy_cluster_to_memory_above_0x00100000();
}
You can improve performance a little by reading more than one cluster at a time (where possible):
Code:
while(not_all_loadeed) {
find_next_cluster();
sectors = find_contiguous_clusters() * sectors_per_cluster;
if(sectors > buffer_size / bytes_per_sector) {
sectors = buffer_size / bytes_per_sector;
}
read_contiguous_sectors_into_buffer(count);
copy_sectors_to_memory_above_0x00100000(count);
}
find_next_cluster();
sectors = find_contiguous_clusters() * sectors_per_cluster;
if(sectors > buffer_size / bytes_per_sector) {
sectors = buffer_size / bytes_per_sector;
}
read_contiguous_sectors_into_buffer(count);
copy_sectors_to_memory_above_0x00100000(count);
}
Also, for the last cluster in the file you may be able to skip some sectors. For example, if a cluster is 2 KiB (4 sectors) and the end of the file only consumes 123 bytes of the last cluster, then you could only load 1 sector of the last cluster.
mark3094 wrote:
Any ideas what I may be doing wrong here?
Not really. 0x0550:0x0000 is the same physical address as 0x0000:0x5500, and there's no other information that we can check.
Cheers,
Brendan
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