From: Rusty Russell <rusty@rustcorp.com.au>

Eric Biederman complained that lguest doesn't use the Linux standard boot
header format.  He's got a good point.

This also simplifies the code: the example launcher writes the header
directly, rather than lguest writing into it during boot.

While we're touching this code, we also fix the problem of initrd's which
don't have a page-aligned size.

This anticipates changing the paravirt-finding routines to use a "platform
type" field from %esi, rather than a "probe all until one succeeds"
routine, but doesn't actually change that code.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/lguest/lguest.c |   48 ++++++++++++++++++++------------
 1 files changed, 31 insertions(+), 17 deletions(-)

diff -puN Documentation/lguest/lguest.c~lguest-use-standard-bootloader-format-fix-badly-sized-doc Documentation/lguest/lguest.c
--- a/Documentation/lguest/lguest.c~lguest-use-standard-bootloader-format-fix-badly-sized-doc
+++ a/Documentation/lguest/lguest.c
@@ -30,10 +30,12 @@
 #include <termios.h>
 #include <getopt.h>
 #include <zlib.h>
+typedef unsigned long long u64;
 typedef uint32_t u32;
 typedef uint16_t u16;
 typedef uint8_t u8;
 #include "../../include/linux/lguest_launcher.h"
+#include "../../include/asm-i386/e820.h"
 
 #define PAGE_PRESENT 0x7 	/* Present, RW, Execute */
 #define NET_PEERNUM 1
@@ -241,31 +243,33 @@ static unsigned long load_kernel(int fd,
 	return load_bzimage(fd, page_offset);
 }
 
+static inline unsigned long page_align(unsigned long addr)
+{
+	return ((addr + getpagesize()-1) & ~(getpagesize()-1));
+}
+
 /* initrd gets loaded at top of memory: return length. */
 static unsigned long load_initrd(const char *name, unsigned long mem)
 {
 	int ifd;
 	struct stat st;
+	unsigned long len;
 	void *iaddr;
 
 	ifd = open_or_die(name, O_RDONLY);
 	if (fstat(ifd, &st) < 0)
 		err(1, "fstat() on initrd '%s'", name);
 
-	iaddr = mmap((void *)mem - st.st_size, st.st_size,
+	len = page_align(st.st_size);
+	iaddr = mmap((void *)mem - len, st.st_size,
 		     PROT_READ|PROT_EXEC|PROT_WRITE,
 		     MAP_FIXED|MAP_PRIVATE, ifd, 0);
-	if (iaddr != (void *)mem - st.st_size)
+	if (iaddr != (void *)mem - len)
 		err(1, "Mmaping initrd '%s' returned %p not %p",
-		    name, iaddr, (void *)mem - st.st_size);
+		    name, iaddr, (void *)mem - len);
 	close(ifd);
 	verbose("mapped initrd %s size=%lu @ %p\n", name, st.st_size, iaddr);
-	return st.st_size;
-}
-
-static inline unsigned long page_align(unsigned long addr)
-{
-	return ((addr + getpagesize()-1) & ~(getpagesize()-1));
+	return len;
 }
 
 static unsigned long setup_pagetables(unsigned long mem,
@@ -933,10 +937,10 @@ static void usage(void)
 
 int main(int argc, char *argv[])
 {
-	unsigned long mem, pgdir, start, page_offset;
+	unsigned long mem, pgdir, start, page_offset, initrd_size = 0;
 	int c, lguest_fd, waker_fd;
 	struct device_list device_list;
-	struct lguest_boot_info *boot = (void *)0;
+	void *boot = (void *)0;
 	const char *initrd_name = NULL;
 
 	device_list.max_infd = -1;
@@ -984,15 +988,25 @@ int main(int argc, char *argv[])
 	map_device_descriptors(&device_list, mem);
 
 	/* Map the initrd image if requested */
-	if (initrd_name)
-		boot->initrd_size = load_initrd(initrd_name, mem);
+	if (initrd_name) {
+		initrd_size = load_initrd(initrd_name, mem);
+		*(unsigned long *)(boot+0x218) = mem - initrd_size;
+		*(unsigned long *)(boot+0x21c) = initrd_size;
+		*(unsigned char *)(boot+0x210) = 0xFF;
+	}
 
 	/* Set up the initial linar pagetables. */
-	pgdir = setup_pagetables(mem, boot->initrd_size, page_offset);
+	pgdir = setup_pagetables(mem, initrd_size, page_offset);
 
-	/* Give the guest the boot information it needs. */
-	concat(boot->cmdline, argv+optind+2);
-	boot->max_pfn = mem/getpagesize();
+	/* E820 memory map: ours is a simple, single region. */
+	*(char*)(boot+E820NR) = 1;
+	*((struct e820entry *)(boot+E820MAP))
+		= ((struct e820entry) { 0, mem, E820_RAM });
+	/* Command line pointer and command line (at 4096) */
+	*(void **)(boot + 0x228) = boot + 4096;
+	concat(boot + 4096, argv+optind+2);
+	/* Paravirt type: 1 == lguest */
+	*(int *)(boot + 0x23c) = 1;
 
 	lguest_fd = tell_kernel(pgdir, start, page_offset);
 	waker_fd = setup_waker(&device_list);
_