i am following james tutorial, to implement the filesystems as specified in it.(http://www.jamesmolloy.co.uk/tutorial_h ... nitrd.html)
The tutorial, and the source code have only implemented the initrd_read() function, which is working fine, i am trying to implement the initrd_write() on my own.
The makeInitrd.c is the code to make the initial ramdisk, i have made a few changes as compared to the tutorials, i have added some buffer spaces(empty spaces) in the header's section and the data section, which i wanted to use later during initrd_write(), to write new headers and data into this filesystem.
the code is as follows,
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struct initrd_header
{
unsigned char magic;
char name[64];
unsigned int offset;
unsigned int length;
};
int main(int argc, char **argv)
{
int nheaders = (argc-1)/2;
struct initrd_header headers[64]; //max of 64 files
printf("Size of the header : %d \n", sizeof(struct initrd_header));
memcpy(headers,0,sizeof(struct initrd_header) * 64);
unsigned int off = sizeof(struct initrd_header) * 64 + sizeof(int);
int i;
for(i=0; i<nheaders; i++)
{
printf("writing files %s->%s at 0x%x\n", argv[i*2 + 1],argv[i*2 + 2], off);
strcpy(headers[i].name, argv[i*2+2]);
headers[i].offset = off;
FILE *stream = fopen(argv[i*2+1],"r");
if(stream == 0)
{
printf("Error: file not found: %s\n", argv[i*2+1]);
return 1;
}
fseek(stream, 0, SEEK_END);
headers[i].length = ftell(stream);
off += headers[i].length;
fclose(stream);
headers[i].magic = 0xBF;
}
//put the other headers as null
for(;i<64;i++)
{
strcpy(headers[i].name,"");
headers[i].offset=0;
headers[i].length=0;
headers[i].magic=0;
}
FILE *wstream = fopen("initrd.img", "w");
unsigned char *data = (unsigned char *)malloc(off);
//this may be wrong
//fwrite(&nheaders, sizeof(int), 1, wstream);
//fwrite(headers, sizeof(struct initrd_header), 64, wstream);
//My correction... i believe this should be used
fwrite(&nheaders, 1, sizeof(int),wstream);
fwrite(headers, 1, sizeof(struct initrd_header)*64, wstream);
for(i = 0; i < nheaders; i++)
{
FILE *stream = fopen(argv[i*2+1], "r");
unsigned char *buf = (unsigned char *)malloc(headers[i].length);
fread(buf, 1, headers[i].length, stream);
fwrite(buf, 1, headers[i].length, wstream);
fclose(stream);
free(buf);
}
//allot a chunk of free space
unsigned char *buf = (unsigned char *)malloc(100);
buf[0]=' ';
buf[1]='\0';
fwrite(buf, 500, 100, wstream);
fclose(wstream);
free(data);
return 0;
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u32int initrd_write(fs_node_t *node, u32int offset, u32int size, u8int *buffer)
{
initrd_file_header_t header ;
u32int off = (file_headers[(initrd_header->nfiles)-1].offset)+(file_headers[(initrd_header->nfiles)-1].length);
//make the new header
header.magic= 0xBF;
strcpy(header.name, "newFile.txt");
puts("\nworking fine till here...");
for(;;);
header.offset = off; //this is causing page fault
header.length = size;
//add the header entry to the file system
file_headers[initrd_header->nfiles] = header;
memcpy(off, buffer, size);
//make a new node
node->mask = node->uid = node->gid = 0;
node->length = size;
node->inode = initrd_header->nfiles;
node->flags = FS_FILE;
node->read = &initrd_read;
node->write = &initrd_write;
node->readdir = 0;
node->finddir = 0;
node->open = 0;
node->close = 0;
node->impl = 0;
//update the root directory
root_nodes[initrd_header->nfiles] =*node;
puts("\nwrite is called...");
puts("file name :");
puts(root_nodes[initrd_header->nfiles].name);
puts("\tcontent:");
puts(buffer);
//increment the total no of files
(initrd_header->nfiles)++;
nroot_nodes = initrd_header->nfiles;
return size;
}
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u32int initrd_location = *((u32int*)mboot_ptr->mods_addr);
u32int initrd_end = *(u32int*)(mboot_ptr->mods_addr+4);
placement_address = initrd_end;
initialise_paging();