Imbus/xv6-riscv-kernel
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xv6: boot loader adjustments

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do Bochs breakpoint and spin in bootasm.S.
not needed in bootmain too.
fix readseg bug (rounding of va).
zero segments when memsz > filesz.
no need to clear BSS in kernel main.
make bootother.S like bootasm.S
This commit is contained in:
rsc 2009-03-08 21:41:30 +00:00
parent 8220135362
commit b7f653dc49
4 changed files with 41 additions and 31 deletions
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29
bootmain.c
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@ -11,7 +11,7 @@
#define SECTSIZE 512
void readseg(uint, uint, uint);
void readseg(uchar*, uint, uint);
void
bootmain(void)
@ -19,32 +19,31 @@ bootmain(void)
struct elfhdr *elf;
struct proghdr *ph, *eph;
void (*entry)(void);
uchar* va;
elf = (struct elfhdr*)0x10000; // scratch space
// Read 1st page off disk
readseg((uint)elf, SECTSIZE*8, 0);
readseg((uchar*)elf, 4096, 0);
// Is this an ELF executable?
if(elf->magic != ELF_MAGIC)
goto bad;
return; // let bootasm.S handle error
// Load each program segment (ignores ph flags).
ph = (struct proghdr*)((uchar*)elf + elf->phoff);
eph = ph + elf->phnum;
for(; ph < eph; ph++)
readseg(ph->va & 0xFFFFFF, ph->memsz, ph->offset);
for(; ph < eph; ph++) {
va = (uchar*)(ph->va & 0xFFFFFF);
readseg(va, ph->filesz, ph->offset);
if(ph->memsz > ph->filesz)
stosb(va + ph->filesz, 0, ph->memsz - ph->filesz);
}
// Call the entry point from the ELF header.
// Does not return!
entry = (void(*)(void))(elf->entry & 0xFFFFFF);
entry();
bad:
outw(0x8A00, 0x8A00);
outw(0x8A00, 0x8E00);
for(;;)
;
}
void
@ -76,14 +75,14 @@ readsect(void *dst, uint offset)
// Read 'count' bytes at 'offset' from kernel into virtual address 'va'.
// Might copy more than asked.
void
readseg(uint va, uint count, uint offset)
readseg(uchar* va, uint count, uint offset)
{
uint eva;
uchar* eva;
eva = va + count;
// Round down to sector boundary.
va &= ~(SECTSIZE - 1);
va -= offset % SECTSIZE;
// Translate from bytes to sectors; kernel starts at sector 1.
offset = (offset / SECTSIZE) + 1;
@ -92,5 +91,5 @@ readseg(uint va, uint count, uint offset)
// We'd write more to memory than asked, but it doesn't matter --
// we load in increasing order.
for(; va < eva; va += SECTSIZE, offset++)
readsect((uchar*)va, offset);
readsect(va, offset);
}