linux/arch/x86/boot
David Woodhouse 99f857db88 x86, build: Dynamically find entry points in compressed startup code
We have historically hard-coded entry points in head.S just so it's easy
to build the executable/bzImage headers with references to them.

Unfortunately, this leads to boot loaders abusing these "known" addresses
even when they are *explicitly* told that they "should look at the ELF
header to find this address, as it may change in the future". And even
when the address in question *has* actually been changed in the past,
without fanfare or thought to compatibility.

Thus we have bootloaders doing stunningly broken things like jumping
to offset 0x200 in the kernel startup code in 64-bit mode, *hoping*
that startup_64 is still there (it has moved at least once
before). And hoping that it's actually a 64-bit kernel despite the
fact that we don't give them any indication of that fact.

This patch should hopefully remove the temptation to abuse internal
addresses in future, where sternly worded comments have not sufficed.
Instead of having hard-coded addresses and saying "please don't abuse
these", we actually pull the addresses out of the ELF payload into
zoffset.h, and make build.c shove them back into the right places in
the bzImage header.

Rather than including zoffset.h into build.c and thus having to rebuild
the tool for every kernel build, we parse it instead. The parsing code
is small and simple.

This patch doesn't actually move any of the interesting entry points, so
any offending bootloader will still continue to "work" after this patch
is applied. For some version of "work" which includes jumping into the
compressed payload and crashing, if the bzImage it's given is a 32-bit
kernel. No change there then.

[ hpa: some of the issues in the description are addressed or
  retconned by the 2.12 boot protocol.  This patch has been edited to
  only remove fixed addresses that were *not* thus retconned. ]

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Link: http://lkml.kernel.org/r/1358513837.2397.247.camel@shinybook.infradead.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Matt Fleming <matt.fleming@intel.com>
2013-01-27 20:19:37 -08:00
..
compressed x86, build: Dynamically find entry points in compressed startup code 2013-01-27 20:19:37 -08:00
tools x86, build: Dynamically find entry points in compressed startup code 2013-01-27 20:19:37 -08:00
.gitignore x86: remove offsets.h from .gitignore and dontdiff 2012-11-19 14:10:53 +01:00
a20.c x86, setup: "glove box" BIOS interrupts in the core boot code 2009-04-09 16:08:11 -07:00
apm.c x86, setup: "glove box" BIOS interrupts in the APM code 2009-04-09 16:08:11 -07:00
bioscall.S x86, boot: use .code16gcc instead of .code16 2009-06-16 17:47:32 -07:00
bitops.h
boot.h x86, boot: Fix port argument to inl() function 2012-01-31 12:05:54 -08:00
cmdline.c x86, setup: reorganize the early console setup 2010-08-02 15:51:56 -07:00
code16gcc.h
copy.S x86: copy.S - use GLOBAL,ENDPROC macros 2009-02-19 17:13:00 +01:00
cpu.c x86 setup: handle more than 8 CPU flag words 2008-09-16 15:09:26 -07:00
cpucheck.c x86: boot: stub out unimplemented CPU feature words 2008-09-05 16:13:44 -07:00
ctype.h x86, setup: move isdigit.h to ctype.h, header files on top. 2010-08-02 21:07:20 -07:00
early_serial_console.c x86, setup: Fix earlyprintk=serial,0x3f8,115200 2010-09-21 10:18:33 -07:00
edd.c x86, setup: "glove box" BIOS interrupts in the EDD code 2009-04-09 16:08:11 -07:00
header.S x86, boot: Define the 2.12 bzImage boot protocol 2013-01-27 15:56:37 -08:00
install.sh kbuild: use INSTALLKERNEL to select customized installkernel script 2009-09-20 12:18:14 +02:00
main.c keyboard: Use BIOS Keyboard variable to set Numlock 2012-05-08 14:19:41 -07:00
Makefile x86, build: Dynamically find entry points in compressed startup code 2013-01-27 20:19:37 -08:00
mca.c x86, setup: "glove box" BIOS interrupts in the MCA code 2009-04-09 16:08:11 -07:00
memory.c x86, setup: When probing memory with e801, use ax/bx as a pair 2011-04-25 14:52:37 -07:00
mkcpustr.c UAPI: Partition the header include path sets and add uapi/ header directories 2012-10-02 18:01:26 +01:00
mtools.conf.in
pm.c x86: remove zImage support 2009-03-11 11:00:00 -07:00
pmjump.S x86, setup: move 32-bit code to .text32 2009-03-17 15:26:06 -07:00
printf.c x86, setup: reorganize the early console setup 2010-08-02 15:51:56 -07:00
regs.c x86, setup: "glove box" BIOS calls -- infrastructure 2009-04-09 16:08:11 -07:00
setup.ld x86, boot: Define the 2.12 bzImage boot protocol 2013-01-27 15:56:37 -08:00
string.c x86, efi: EFI boot stub support 2011-12-12 14:26:10 -08:00
tty.c x86, setup: reorganize the early console setup 2010-08-02 15:51:56 -07:00
version.c kbuild: move utsrelease.h to include/generated 2009-12-12 13:08:15 +01:00
vesa.h
video-bios.c x86: fix usage of bios intcall() 2009-07-04 12:56:32 -07:00
video-mode.c
video-vesa.c Merge branch 'x86-setup-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-09-14 08:01:47 -07:00
video-vga.c x86, setup: Set ax register in boot vga query 2010-06-10 15:24:29 -07:00
video.c x86, setup: When restoring the screen, update boot_params.screen_info 2010-02-17 18:32:06 -08:00
video.h x86, setup: remove obsolete pre-Kconfig CONFIG_VIDEO_ variables 2009-06-26 11:02:31 -07:00