18e670053Srsc // Boot loader.
2f5527388Srsc //
3*c24ac5d7SFrans Kaashoek // Part of the boot block, along with bootasm.S, which calls bootmain().
4411ee741Srtm // bootasm.S has put the processor into protected 32-bit mode.
5411ee741Srtm // bootmain() loads an ELF kernel image from the disk starting at
6411ee741Srtm // sector 1 and then jumps to the kernel entry routine.
70cfc7290Srsc
80cfc7290Srsc #include "types.h"
90cfc7290Srsc #include "elf.h"
100cfc7290Srsc #include "x86.h"
119aa0337dSFrans Kaashoek #include "memlayout.h"
1255e95b16Srtm
1355e95b16Srtm #define SECTSIZE 512
1455e95b16Srtm
15b7f653dcSrsc void readseg(uchar*, uint, uint);
1655e95b16Srtm
1755e95b16Srtm void
bootmain(void)18c35c064eSrsc bootmain(void)
1955e95b16Srtm {
2097ac612fSrsc struct elfhdr *elf;
21b5f17007Srsc struct proghdr *ph, *eph;
2297ac612fSrsc void (*entry)(void);
239aa0337dSFrans Kaashoek uchar* pa;
2455e95b16Srtm
2597ac612fSrsc elf = (struct elfhdr*)0x10000; // scratch space
2655e95b16Srtm
2797ac612fSrsc // Read 1st page off disk
28b7f653dcSrsc readseg((uchar*)elf, 4096, 0);
2997ac612fSrsc
3097ac612fSrsc // Is this an ELF executable?
3197ac612fSrsc if(elf->magic != ELF_MAGIC)
32b7f653dcSrsc return; // let bootasm.S handle error
3355e95b16Srtm
3497ac612fSrsc // Load each program segment (ignores ph flags).
3597ac612fSrsc ph = (struct proghdr*)((uchar*)elf + elf->phoff);
3697ac612fSrsc eph = ph + elf->phnum;
37b7f653dcSrsc for(; ph < eph; ph++){
38fa81545fSFrans Kaashoek pa = (uchar*)ph->paddr;
39fa81545fSFrans Kaashoek readseg(pa, ph->filesz, ph->off);
40b7f653dcSrsc if(ph->memsz > ph->filesz)
419aa0337dSFrans Kaashoek stosb(pa + ph->filesz, 0, ph->memsz - ph->filesz);
42b7f653dcSrsc }
4355e95b16Srtm
4497ac612fSrsc // Call the entry point from the ELF header.
4597ac612fSrsc // Does not return!
462fc6c35bSAustin Clements entry = (void(*)(void))(elf->entry);
4797ac612fSrsc entry();
4855e95b16Srtm }
4955e95b16Srtm
50eaea18cbSrsc void
waitdisk(void)51eaea18cbSrsc waitdisk(void)
52eaea18cbSrsc {
5397ac612fSrsc // Wait for disk ready.
54eaea18cbSrsc while((inb(0x1F7) & 0xC0) != 0x40)
55eaea18cbSrsc ;
56eaea18cbSrsc }
57eaea18cbSrsc
58eaea18cbSrsc // Read a single sector at offset into dst.
59eaea18cbSrsc void
readsect(void * dst,uint offset)60eaea18cbSrsc readsect(void *dst, uint offset)
61eaea18cbSrsc {
6297ac612fSrsc // Issue command.
63eaea18cbSrsc waitdisk();
64eaea18cbSrsc outb(0x1F2, 1); // count = 1
65eaea18cbSrsc outb(0x1F3, offset);
66eaea18cbSrsc outb(0x1F4, offset >> 8);
67eaea18cbSrsc outb(0x1F5, offset >> 16);
68eaea18cbSrsc outb(0x1F6, (offset >> 24) | 0xE0);
69eaea18cbSrsc outb(0x1F7, 0x20); // cmd 0x20 - read sectors
70eaea18cbSrsc
7197ac612fSrsc // Read data.
72eaea18cbSrsc waitdisk();
73eaea18cbSrsc insl(0x1F0, dst, SECTSIZE/4);
74eaea18cbSrsc }
75eaea18cbSrsc
76cd3d739eSFrans Kaashoek // Read 'count' bytes at 'offset' from kernel into physical address 'pa'.
77eaea18cbSrsc // Might copy more than asked.
7855e95b16Srtm void
readseg(uchar * pa,uint count,uint offset)79cd3d739eSFrans Kaashoek readseg(uchar* pa, uint count, uint offset)
8055e95b16Srtm {
81cd3d739eSFrans Kaashoek uchar* epa;
8255e95b16Srtm
83cd3d739eSFrans Kaashoek epa = pa + count;
8455e95b16Srtm
8597ac612fSrsc // Round down to sector boundary.
86cd3d739eSFrans Kaashoek pa -= offset % SECTSIZE;
8755e95b16Srtm
8897ac612fSrsc // Translate from bytes to sectors; kernel starts at sector 1.
8955e95b16Srtm offset = (offset / SECTSIZE) + 1;
9055e95b16Srtm
9155e95b16Srtm // If this is too slow, we could read lots of sectors at a time.
9255e95b16Srtm // We'd write more to memory than asked, but it doesn't matter --
9355e95b16Srtm // we load in increasing order.
94cd3d739eSFrans Kaashoek for(; pa < epa; pa += SECTSIZE, offset++)
95cd3d739eSFrans Kaashoek readsect(pa, offset);
9655e95b16Srtm }
97