diff options
Diffstat (limited to 'bootmain.c')
| -rw-r--r-- | bootmain.c | 112 |
1 files changed, 56 insertions, 56 deletions
@@ -11,10 +11,10 @@ * be stored in the first sector of the disk. * * * The 2nd sector onward holds the kernel image. - * + * * * The kernel image must be in ELF format. * - * BOOT UP STEPS + * BOOT UP STEPS * * when the CPU boots it loads the BIOS into memory and executes it * * * the BIOS intializes devices, sets of the interrupt routines, and @@ -30,8 +30,8 @@ * * cmain() in this file takes over, reads in the kernel and jumps to it. **********************************************************************/ -#define SECTSIZE 512 -#define ELFHDR ((struct elfhdr *) 0x10000) // scratch space +#define SECTSIZE 512 +#define ELFHDR ((struct elfhdr *) 0x10000) // scratch space void readsect(void*, uint); void readseg(uint, uint, uint); @@ -39,30 +39,30 @@ void readseg(uint, uint, uint); void cmain(void) { - struct proghdr *ph, *eph; + struct proghdr *ph, *eph; - // read 1st page off disk - readseg((uint) ELFHDR, SECTSIZE*8, 0); + // read 1st page off disk + readseg((uint) ELFHDR, SECTSIZE*8, 0); - // is this a valid ELF? - if (ELFHDR->magic != ELF_MAGIC) - goto bad; + // is this a valid ELF? + if (ELFHDR->magic != ELF_MAGIC) + goto bad; - // load each program segment (ignores ph flags) - ph = (struct proghdr *) ((uchar *) ELFHDR + ELFHDR->phoff); - eph = ph + ELFHDR->phnum; - for (; ph < eph; ph++) - readseg(ph->va, ph->memsz, ph->offset); + // load each program segment (ignores ph flags) + ph = (struct proghdr *) ((uchar *) ELFHDR + ELFHDR->phoff); + eph = ph + ELFHDR->phnum; + for (; ph < eph; ph++) + readseg(ph->va, ph->memsz, ph->offset); - // call the entry point from the ELF header - // note: does not return! - ((void (*)(void)) (ELFHDR->entry & 0xFFFFFF))(); + // call the entry point from the ELF header + // note: does not return! + ((void (*)(void)) (ELFHDR->entry & 0xFFFFFF))(); bad: - outw(0x8A00, 0x8A00); - outw(0x8A00, 0x8E00); - while(1) - /* do nothing */; + outw(0x8A00, 0x8A00); + outw(0x8A00, 0x8E00); + while(1) + /* do nothing */; } // Read 'count' bytes at 'offset' from kernel into virtual address 'va'. @@ -70,52 +70,52 @@ bad: void readseg(uint va, uint count, uint offset) { - uint end_va; - - va &= 0xFFFFFF; - end_va = va + count; - - // round down to sector boundary - va &= ~(SECTSIZE - 1); - - // translate from bytes to sectors, and kernel starts at sector 1 - offset = (offset / SECTSIZE) + 1; - - // If this is too slow, we could read lots of sectors at a time. - // We'd write more to memory than asked, but it doesn't matter -- - // we load in increasing order. - while (va < end_va) { - readsect((uchar*) va, offset); - va += SECTSIZE; - offset++; - } + uint end_va; + + va &= 0xFFFFFF; + end_va = va + count; + + // round down to sector boundary + va &= ~(SECTSIZE - 1); + + // translate from bytes to sectors, and kernel starts at sector 1 + offset = (offset / SECTSIZE) + 1; + + // If this is too slow, we could read lots of sectors at a time. + // We'd write more to memory than asked, but it doesn't matter -- + // we load in increasing order. + while (va < end_va) { + readsect((uchar*) va, offset); + va += SECTSIZE; + offset++; + } } void waitdisk(void) { - // wait for disk reaady - while ((inb(0x1F7) & 0xC0) != 0x40) - /* do nothing */; + // wait for disk reaady + while ((inb(0x1F7) & 0xC0) != 0x40) + /* do nothing */; } void readsect(void *dst, uint offset) { - // wait for disk to be ready - waitdisk(); + // wait for disk to be ready + waitdisk(); - outb(0x1F2, 1); // count = 1 - outb(0x1F3, offset); - outb(0x1F4, offset >> 8); - outb(0x1F5, offset >> 16); - outb(0x1F6, (offset >> 24) | 0xE0); - outb(0x1F7, 0x20); // cmd 0x20 - read sectors + outb(0x1F2, 1); // count = 1 + outb(0x1F3, offset); + outb(0x1F4, offset >> 8); + outb(0x1F5, offset >> 16); + outb(0x1F6, (offset >> 24) | 0xE0); + outb(0x1F7, 0x20); // cmd 0x20 - read sectors - // wait for disk to be ready - waitdisk(); + // wait for disk to be ready + waitdisk(); - // read a sector - insl(0x1F0, dst, SECTSIZE/4); + // read a sector + insl(0x1F0, dst, SECTSIZE/4); } |