linux/arch/x86/boot/string.c
Matt Fleming 291f36325f x86, efi: EFI boot stub support
There is currently a large divide between kernel development and the
development of EFI boot loaders. The idea behind this patch is to give
the kernel developers full control over the EFI boot process. As
H. Peter Anvin put it,

"The 'kernel carries its own stub' approach been very successful in
dealing with BIOS, and would make a lot of sense to me for EFI as
well."

This patch introduces an EFI boot stub that allows an x86 bzImage to
be loaded and executed by EFI firmware. The bzImage appears to the
firmware as an EFI application. Luckily there are enough free bits
within the bzImage header so that it can masquerade as an EFI
application, thereby coercing the EFI firmware into loading it and
jumping to its entry point. The beauty of this masquerading approach
is that both BIOS and EFI boot loaders can still load and run the same
bzImage, thereby allowing a single kernel image to work in any boot
environment.

The EFI boot stub supports multiple initrds, but they must exist on
the same partition as the bzImage. Command-line arguments for the
kernel can be appended after the bzImage name when run from the EFI
shell, e.g.

Shell> bzImage console=ttyS0 root=/dev/sdb initrd=initrd.img

v7:
 - Fix checkpatch warnings.

v6:

 - Try to allocate initrd memory just below hdr->inird_addr_max.

v5:

 - load_options_size is UTF-16, which needs dividing by 2 to convert
   to the corresponding ASCII size.

v4:

 - Don't read more than image->load_options_size

v3:

 - Fix following warnings when compiling CONFIG_EFI_STUB=n

   arch/x86/boot/tools/build.c: In function ‘main’:
   arch/x86/boot/tools/build.c:138:24: warning: unused variable ‘pe_header’
   arch/x86/boot/tools/build.c:138:15: warning: unused variable ‘file_sz’

 - As reported by Matthew Garrett, some Apple machines have GOPs that
   don't have hardware attached. We need to weed these out by
   searching for ones that handle the PCIIO protocol.

 - Don't allocate memory if no initrds are on cmdline
 - Don't trust image->load_options_size

Maarten Lankhorst noted:
 - Don't strip first argument when booted from efibootmgr
 - Don't allocate too much memory for cmdline
 - Don't update cmdline_size, the kernel considers it read-only
 - Don't accept '\n' for initrd names

v2:

 - File alignment was too large, was 8192 should be 512. Reported by
   Maarten Lankhorst on LKML.
 - Added UGA support for graphics
 - Use VIDEO_TYPE_EFI instead of hard-coded number.
 - Move linelength assignment until after we've assigned depth
 - Dynamically fill out AddressOfEntryPoint in tools/build.c
 - Don't use magic number for GDT/TSS stuff. Requested by Andi Kleen
 - The bzImage may need to be relocated as it may have been loaded at
   a high address address by the firmware. This was required to get my
   macbook booting because the firmware loaded it at 0x7cxxxxxx, which
   triggers this error in decompress_kernel(),

	if (heap > ((-__PAGE_OFFSET-(128<<20)-1) & 0x7fffffff))
		error("Destination address too large");

Cc: Mike Waychison <mikew@google.com>
Cc: Matthew Garrett <mjg@redhat.com>
Tested-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Link: http://lkml.kernel.org/r/1321383097.2657.9.camel@mfleming-mobl1.ger.corp.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2011-12-12 14:26:10 -08:00

148 lines
2.7 KiB
C

/* -*- linux-c -*- ------------------------------------------------------- *
*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright 2007 rPath, Inc. - All Rights Reserved
*
* This file is part of the Linux kernel, and is made available under
* the terms of the GNU General Public License version 2.
*
* ----------------------------------------------------------------------- */
/*
* Very basic string functions
*/
#include "boot.h"
int strcmp(const char *str1, const char *str2)
{
const unsigned char *s1 = (const unsigned char *)str1;
const unsigned char *s2 = (const unsigned char *)str2;
int delta = 0;
while (*s1 || *s2) {
delta = *s2 - *s1;
if (delta)
return delta;
s1++;
s2++;
}
return 0;
}
int strncmp(const char *cs, const char *ct, size_t count)
{
unsigned char c1, c2;
while (count) {
c1 = *cs++;
c2 = *ct++;
if (c1 != c2)
return c1 < c2 ? -1 : 1;
if (!c1)
break;
count--;
}
return 0;
}
size_t strnlen(const char *s, size_t maxlen)
{
const char *es = s;
while (*es && maxlen) {
es++;
maxlen--;
}
return (es - s);
}
unsigned int atou(const char *s)
{
unsigned int i = 0;
while (isdigit(*s))
i = i * 10 + (*s++ - '0');
return i;
}
/* Works only for digits and letters, but small and fast */
#define TOLOWER(x) ((x) | 0x20)
static unsigned int simple_guess_base(const char *cp)
{
if (cp[0] == '0') {
if (TOLOWER(cp[1]) == 'x' && isxdigit(cp[2]))
return 16;
else
return 8;
} else {
return 10;
}
}
/**
* simple_strtoull - convert a string to an unsigned long long
* @cp: The start of the string
* @endp: A pointer to the end of the parsed string will be placed here
* @base: The number base to use
*/
unsigned long long simple_strtoull(const char *cp, char **endp, unsigned int base)
{
unsigned long long result = 0;
if (!base)
base = simple_guess_base(cp);
if (base == 16 && cp[0] == '0' && TOLOWER(cp[1]) == 'x')
cp += 2;
while (isxdigit(*cp)) {
unsigned int value;
value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
if (value >= base)
break;
result = result * base + value;
cp++;
}
if (endp)
*endp = (char *)cp;
return result;
}
/**
* strlen - Find the length of a string
* @s: The string to be sized
*/
size_t strlen(const char *s)
{
const char *sc;
for (sc = s; *sc != '\0'; ++sc)
/* nothing */;
return sc - s;
}
/**
* strstr - Find the first substring in a %NUL terminated string
* @s1: The string to be searched
* @s2: The string to search for
*/
char *strstr(const char *s1, const char *s2)
{
size_t l1, l2;
l2 = strlen(s2);
if (!l2)
return (char *)s1;
l1 = strlen(s1);
while (l1 >= l2) {
l1--;
if (!memcmp(s1, s2, l2))
return (char *)s1;
s1++;
}
return NULL;
}