Chris Newton
2004-Oct-07 14:39 UTC
[syslinux] x86 vs. x86_64 detection proof of concept patch (try two)
Greetings all,
Sorry, resending this with the attachment inline.
First of all, a disclaimer: Please forgive my horrible assembly code.
This is just a quick munging of code to achieve x86 versus x86_64
detection within pxelinux. So please look at it as a proof of concept
and not a real piece of code. :) For example it only works on pxelinux
and has no thought for extending it beyond simple x86 versus x86_64
architectures.
I had the need for pxelinux to be able to detect if the cpu its running
on is a x86 or x86_64 machine. Seeing as the two opteron motherboards I
have don't specify any difference in the PXE identification string in
the DHCP discover packets they send out. So I have copied some code from
the linux kernel for detecting the cpu and added in a 'kernel64'
configuration option. The kernel64 option is ignored if the cpu is not a
x86_64.
So my machines can now boot with a 32bit or 64bit kernel depending on
their architecture. I did not put in a similar append64 option because
my initrd works for both kind of kernels.
Hopefully this can benefit someone. :) Best of luck.
--
J. Christopher Newton
Software Engineer
Aspen Systems, Inc.
3900 Youngfield Street
Wheat Ridge, Co 80033
Tel +01 (303) 431-4606 Ext. 132
Fax +01 (303) 431-7196
Email: chrisn at aspsys.com
www.aspsys.com
Common subdirectories: syslinux-2.11/com32 and syslinux-2.11.new/com32
diff -u syslinux-2.11/keywords syslinux-2.11.new/keywords
--- syslinux-2.11/keywords 2004-05-29 16:11:23.000000000 -0600
+++ syslinux-2.11.new/keywords 2004-10-04 17:33:54.000000000 -0600
@@ -7,6 +7,7 @@
ipappend
kbdmap
kernel
+kernel64
label
localboot
prompt
diff -u syslinux-2.11/keywords.inc syslinux-2.11.new/keywords.inc
--- syslinux-2.11/keywords.inc 2004-05-29 16:11:23.000000000 -0600
+++ syslinux-2.11.new/keywords.inc 2004-10-04 17:33:55.000000000 -0600
@@ -52,6 +52,7 @@
keyword implicit, pc_setint16, AllowImplicit
keyword kbdmap, pc_filecmd, loadkeys
keyword kernel, pc_kernel
+ keyword kernel64, pc_kernel64
keyword label, pc_label
keyword prompt, pc_setint16, ForcePrompt
keyword say, pc_say
Common subdirectories: syslinux-2.11/memdisk and
syslinux-2.11.new/memdisk
Common subdirectories: syslinux-2.11/menu and syslinux-2.11.new/menu
diff -u syslinux-2.11/parseconfig.inc syslinux-2.11.new/parseconfig.inc
--- syslinux-2.11/parseconfig.inc 2003-11-26 22:36:16.000000000 -0700
+++ syslinux-2.11.new/parseconfig.inc 2004-10-04 17:33:55.000000000
-0600
@@ -100,6 +100,17 @@
.err: ret
;
+; "kernel64" command
+pc_kernel64: cmp word [VKernelCtr],byte 0
+ je .err ; ("label" section only)
+ cmp word [CpuIs64], 0
+ je .err ; Ignore if kernel cpu is 32bit
+ call pc_getline
+ mov di,VKernelBuf+vk_rname
+ call mangle_name
+.err: ret
+
+;
; "timeout" command
;
pc_timeout: call getint
diff -u syslinux-2.11/pxelinux.asm syslinux-2.11.new/pxelinux.asm
--- syslinux-2.11/pxelinux.asm 2004-08-04 00:16:53.000000000 -0600
+++ syslinux-2.11.new/pxelinux.asm 2004-10-04 17:33:56.000000000 -0600
@@ -304,6 +304,7 @@
command_line resb max_cmd_len+2 ; Command line buffer
alignb 4
default_cmd resb max_cmd_len+1 ; "default" command line
+CpuIs64 resw 1 ; Is this cpu a x86_64 machine?
;
; PXE packets which don't need static initialization
@@ -392,6 +393,27 @@
call writestr
;
+; ID the CPU: Shamelessly borrowed from the Linux kernel
arch/x86_64/kernel/head.S
+;
+ mov word [CpuIs64], 0
+ mov eax, 80000000h
+ cpuid
+ cmp eax, 80000000h
+ jbe afterbits
+ ; Check if long mode is implemented
+ mov eax, 80000001h
+ cpuid
+ bt edx, 29
+ jnc afterbits
+ mov word [CpuIs64], 1
+afterbits:
+ mov si, cpu64_str
+ cmp word [CpuIs64], 1
+ je writecpustr
+ mov si, cpu32_str
+writecpustr: call writestr
+
+;
; Assume API version 2.1, in case we find the !PXE structure without
; finding the PXENV+ structure. This should really look at the Base
; Code ROM ID structure in have_pxe, but this is adequate for now --
@@ -2366,6 +2388,8 @@
default_str db 'default', 0
default_len equ ($-default_str)
syslinux_banner db CR, LF, 'PXELINUX ', version_str, ' ', date,
' ', 0
+cpu32_str db 'CPUID: x86', CR, LF, 0
+cpu64_str db 'CPUID: x86_64', CR, LF, 0
cfgprefix db 'pxelinux.cfg/' ; No final null!
cfgprefix_len equ ($-cfgprefix)
Common subdirectories: syslinux-2.11/sample and syslinux-2.11.new/sample
Common subdirectories: syslinux-2.11/win32 and syslinux-2.11.new/win32
H. Peter Anvin
2004-Oct-07 18:17 UTC
[syslinux] x86 vs. x86_64 detection proof of concept patch (try two)
Chris Newton wrote:> Greetings all, > > Sorry, resending this with the attachment inline. > > First of all, a disclaimer: Please forgive my horrible assembly code. > This is just a quick munging of code to achieve x86 versus x86_64 > detection within pxelinux. So please look at it as a proof of concept > and not a real piece of code. :) For example it only works on pxelinux > and has no thought for extending it beyond simple x86 versus x86_64 > architectures. > > I had the need for pxelinux to be able to detect if the cpu its running > on is a x86 or x86_64 machine. Seeing as the two opteron motherboards I > have don't specify any difference in the PXE identification string in > the DHCP discover packets they send out. So I have copied some code from > the linux kernel for detecting the cpu and added in a 'kernel64' > configuration option. The kernel64 option is ignored if the cpu is not a > x86_64. > > So my machines can now boot with a 32bit or 64bit kernel depending on > their architecture. I did not put in a similar append64 option because > my initrd works for both kind of kernels. > > Hopefully this can benefit someone. :) Best of luck. >I think this kind of things are better done with a comboot image, mostly because x86 vs x86-64 is only one of *many* selections one may wish to make when selecting a kernel. Some people would want to have i586/i686/athlon/pentium4/k8/em64t kernels on tap, for example. -hpa