Hello Levente,
You wrote:
I have a similar hack to check if the cpu is 64 or 32 bits. Let me know if
someone needs it.
Please send it.
cheers,
-a
Since there are some people who are interested in them I provide my little
monstrosities. I do it in the good faith that if someone finds them useful,
he will work on them and turn them into something neat that is
consistent with
ipxe code base (which is a remarkably well organized piece of software).
A few words of warning concerning these *hacks* (since that's what they
are,
don't be mistaken):
-local hdd count: Don't be surprised if your usb sticks (sdcards,
whatever) are counted
as hdds. Standard PC-BIOS puts the number of devices it considers
'hdd's at 0x00000475.
Now, BIOSes tend to list usb mass storage devices as hard drives. To
my knowledge
there is no standard api in PC-BIOS that is implemented at least by a
reasonable
number of BIOSes that lets one read hardware information on hdds
(otherwise perfectly
well known to the BIOS).
-32/64 bitness: Please be warned that the code below works only on
ia32/amd64 cpus
from about Pentium onwards (I think). Other x86 cpus (286,386 or 486)
will probably
crash on this code. If somebody takes the time to implement a proper
ipxe setting
please follow the (lengthy and painful) procedure in the Intel docs
according to the
rules of chivalry.
Below is the recipie for the 'iscpu64' stuff:
In the file src/core/main.c:
-add the include
#include <realmode.h>
-add these variables in main() to the variable declarations:
unsigned long is_cpu_64bit;
char sname[32];
char sval[32];
-still in main() search for the call to initialise() and startup(), and
put this code after them:
//this is a bit loose here,
//we assume cpuid works (i.e. we have pentium or newer cpu)
is_cpu_64bit = 0xbabeface;
__asm__ __volatile__ ( "push %%ebx\n\t"
"movl $0x80000000,%%eax\n\t"
"cpuid\n\t"
"cmpl $0x80000001,%%eax\n\t"
"jb 1f\n\t"
"movl $0x80000001,%%eax\n\t"
"cpuid\n\t"
"andl $0x20000000,%%edx\n\t"
"jmp 2f\n\t"
"\n1:\n\t"
"xorl %%edx,%%edx\n\t"
"\n2:\n\t"
"pop %%ebx\n\t"
: "=d" ( is_cpu_64bit )
:
: "eax", "ecx" );
memset ( sname, 0, sizeof ( sname ) );
strncpy ( sname, "iscpu64", sizeof ( sname ) - 1 );
memset ( sval, 0, sizeof ( sval ) );
sval[0] = ( is_cpu_64bit ) ? '1' : '0';
storef_named_setting ( sname, sval );
/levente
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