On Tue, Aug 05, 2008 at 12:50:54PM +0800, Zhang Rui wrote:
> Hello,
> I am blocked with calling interrupt in coreboot.
> I tryed these ways:
> 1. use "asm("int $0x19 \n");". Qemu has no output when executeed
> here and nothing happens. The reason is that it should jump to real
> mode before calling int 19.
Right. You'd need to call "int 0x19" after transitioning to real
mode.
> 2. write a function boot_coreboot() in seabios. like:
>
> void VISIBLE32 boot_coreboot()
> {
> struct bregs br;
> dprintf(1, "boot_coreboot: begin\n");
> memset(&br, 0, sizeof(br));
> dprintf(1, "boot_coreboot: call int 19\n");
> call16_int(0x19, &br);
> dprintf(1, "boot_coreboot: end\n");
> }
>
> then call boot_coreboot() in seabios. It booted successfully.
>
> I have read the source code of call16_int, it jump to real mode and
> jump to the int 19 handler function directly, but do not use "int
> $0x19" asm code. why?
No. The call_int16(0x19, ...) function will call irq_trampoline_0x19
in real mode (see src/util.h). The irq_trampoline_0x19 code is
defined in src/romlayout.S (see macro "IRQ_TRAMPOLINE 19") which runs
"int 0x19".
> 3. write asm code to jump to real mode and call int 19.
> but in coreboot there is compiling errors when I write asm codes with
> lables in it in vm86.c.
> for a simple example:
> __asm__ __volatile__ (
> /* paranoia -- does ecx get saved? not sure. This is
> * the easiest safe thing to do. */
> " pushal \n"
> " ljmp $0x28, $cbint16bit\n"
> "cbint16bit: \n"
> " .code16 \n"
> " popal\n"
> );
>
> will cause errors:
> {standard input}: Assembler messages:
> {standard input}:746: Error: symbol `cbint16bit' is already defined
>
> in seabios there is compiling errors because of ".code16":
> out/../src/post.c:349: relocation truncated to fit: R_386_16 against
> `.text'
>
> what is wrong here?
I'm guessing you didn't issue a ".code32" after the ".code16". Not
putting the assembler back into 32bit mode will totally confuse it.
Also, you may be running into trouble with the segmented memory model
- the 32bit code runs at 0xfxxxx and uses 32bit offsets, while the
16bit code runs at 0xf000:xxxx and uses 16bit offsets.
I'm not sure why you'd want to do this in seabios though - option 2
above would be the preferred way to call int19.
-Kevin
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