[coreboot] SeaBIOS question and cross compilation fix.

Stefan Reinauer stepan at coresystems.de
Thu Nov 6 16:00:21 CET 2008

Hi, Kevin,

I am experimenting with v3 and better integration of SeaBIOS and
coreboot. For that, I am copying a SeaBIOS image to the FSEG during
coreboot's VGA init code. In addition I added another 32bit entry point
to SeaBIOS at 0xffc0 (Thus, living at 0xfffc0)

int copy_systembios(void)
        struct mem_file archive, result;
        int ret;
        ret = find_file(&archive, "bios.bin", &result);
        if (ret) {
                printk(BIOS_WARNING, "No legacy bios found.\n");
                return -1;
        process_file(&result, (void *)0xf0000);
        return 0;

void run_bios(struct device *dev, unsigned long addr)
        int i;
        void (*init_systembios)(void) = (void *)0xfffc0;
        real_mode_switch_call_vga((dev->bus->secondary << 8) |

Now, the entry point looks like this:
diff -ur -x .git seabios2/src/romlayout.S seabios/src/romlayout.S
--- seabios2/src/romlayout.S    2008-11-06 15:46:44.000000000 +0100
+++ seabios/src/romlayout.S     2008-11-01 11:38:06.000000000 +0100
@@ -544,6 +544,18 @@
         ORG 0xff54
         IRQ_ENTRY_ARG 05

+        ORG 0xffc0 // coreboot Entry Point
+       mov $0x3f8, %dx
+       mov $0x44, %al
+       outb %al, %dx // print
+       call _code32__init
+       mov $0x3f8, %dx
+       mov $0x45, %al
+       outb %al, %dx
+       ret
         ORG 0xfff0 // Power-up Entry Point
         ljmpw $SEG_BIOS, $post16

And _init looks like this (simplified):

void VISIBLE32
    outb('@', 0x3f8);

Unfortunately, this does not seem to work. The machine jumps somewhere
else and will triple fault eventually.

The outb to serial console in the assembler entry point work fine. If I
comment out the call to _code32__init, the function also returns nicely.
(printing "DE" on the way. But as soon as I leave the call in, seabios
crashes after printing "D" It does not even print the @.

Any hints?

Also, find attached a patch to allow cross compilation of SeaBIOS and
make it work with systems where /bin/echo does not know the option -e


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