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Use "struct boot_params" in example launcher 

Now that the "struct boot_params" is userspace accessible, we don't need
magic numbers.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2007-10-22 11:29:57 +10:00
parent 5bbf89fc26
commit 43d33b21a0
1 changed files with 22 additions and 25 deletions
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47
Documentation/lguest/lguest.c
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@ -52,7 +52,7 @@ typedef uint8_t u8;
#include "linux/virtio_blk.h"
#include "linux/virtio_console.h"
#include "linux/virtio_ring.h"
#include "asm-x86/e820.h"
#include "asm-x86/bootparam.h"
/*:*/
#define PAGE_PRESENT 0x7 /* Present, RW, Execute */
@ -335,7 +335,7 @@ static unsigned long map_elf(int elf_fd, const Elf32_Ehdr *ehdr)
* the funky header so we know where in the file to load, and away we go! */
static unsigned long load_bzimage(int fd)
{
u8 hdr[1024];
struct boot_params boot;
int r;
/* Modern bzImages get loaded at 1M. */
void *p = from_guest_phys(0x100000);
@ -343,22 +343,21 @@ static unsigned long load_bzimage(int fd)
/* Go back to the start of the file and read the header. It should be
* a Linux boot header (see Documentation/i386/boot.txt) */
lseek(fd, 0, SEEK_SET);
read(fd, hdr, sizeof(hdr));
read(fd, &boot, sizeof(boot));
/* At offset 0x202, we expect the magic "HdrS" */
if (memcmp(hdr + 0x202, "HdrS", 4) != 0)
/* Inside the setup_hdr, we expect the magic "HdrS" */
if (memcmp(&boot.hdr.header, "HdrS", 4) != 0)
errx(1, "This doesn't look like a bzImage to me");
/* The byte at 0x1F1 tells us how many extra sectors of
* header: skip over them all. */
lseek(fd, (unsigned long)(hdr[0x1F1]+1) * 512, SEEK_SET);
/* Skip over the extra sectors of the header. */
lseek(fd, (boot.hdr.setup_sects+1) * 512, SEEK_SET);
/* Now read everything into memory. in nice big chunks. */
while ((r = read(fd, p, 65536)) > 0)
p += r;
/* Finally, 0x214 tells us where to start the kernel. */
return *(unsigned long *)&hdr[0x214];
/* Finally, code32_start tells us where to enter the kernel. */
return boot.hdr.code32_start;
}
/*L:140 Loading the kernel is easy when it's a "vmlinux", but most kernels
@ -1531,7 +1530,7 @@ int main(int argc, char *argv[])
/* A temporary and the /dev/lguest file descriptor. */
int i, c, lguest_fd;
/* The boot information for the Guest. */
void *boot;
struct boot_params *boot;
/* If they specify an initrd file to load. */
const char *initrd_name = NULL;
@ -1607,10 +1606,10 @@ int main(int argc, char *argv[])
initrd_size = load_initrd(initrd_name, mem);
/* These are the location in the Linux boot header where the
* start and size of the initrd are expected to be found. */
*(unsigned long *)(boot+0x218) = mem - initrd_size;
*(unsigned long *)(boot+0x21c) = initrd_size;
boot->hdr.ramdisk_image = mem - initrd_size;
boot->hdr.ramdisk_size = initrd_size;
/* The bootloader type 0xFF means "unknown"; that's OK. */
*(unsigned char *)(boot+0x210) = 0xFF;
boot->hdr.type_of_loader = 0xFF;
}
/* Set up the initial linear pagetables, starting below the initrd. */
@ -1618,23 +1617,21 @@ int main(int argc, char *argv[])
/* The Linux boot header contains an "E820" memory map: ours is a
* simple, single region. */
*(char*)(boot+E820NR) = 1;
*((struct e820entry *)(boot+E820MAP))
= ((struct e820entry) { 0, mem, E820_RAM });
boot->e820_entries = 1;
boot->e820_map[0] = ((struct e820entry) { 0, mem, E820_RAM });
/* The boot header contains a command line pointer: we put the command
* line after the boot header (at address 4096) */
*(u32 *)(boot + 0x228) = 4096;
concat(boot + 4096, argv+optind+2);
* line after the boot header. */
boot->hdr.cmd_line_ptr = to_guest_phys(boot + 1);
concat((char *)(boot + 1), argv+optind+2);
/* Boot protocol version: 2.07 supports the fields for lguest. */
*(u16 *)(boot + 0x206) = 0x207;
boot->hdr.version = 0x207;
/* The hardware_subarch value of "1" tells the Guest it's an lguest. */
*(u32 *)(boot + 0x23c) = 1;
boot->hdr.hardware_subarch = 1;
/* Set bit 6 of the loadflags (aka. KEEP_SEGMENTS) so the entry path
* does not try to reload segment registers. */
*(u8 *)(boot + 0x211) |= (1 << 6);
/* Tell the entry path not to try to reload segment registers. */
boot->hdr.loadflags |= KEEP_SEGMENTS;
/* We tell the kernel to initialize the Guest: this returns the open
* /dev/lguest file descriptor. */