Migration to Etherboot-5.3 discussion

[R CHAN]

Hi,

Since others have brought it up, and it may not be rocket science,
I thought I'd start a thread on new functions in Etherboot-5.3
and how one might best migrate them to GRUB. As Okuji has pointed up,
others have tried and given up and it may not require a genious-level 
programmer, (but I'm currently at the moron-level).

Here are the global symbols needed by e1000.o
 U adjust_pci_device
 U mdelay
 U pci_bar_size
 U pci_bar_start
 U pcibios_read_config_byte
 U pcibios_read_config_word
 U pcibios_write_config_word
 U poll_interruptions
 U printf
 U udelay
 U virt_offset
and some questions on resolving them, please correct.

1. printf - no problem - map to etherboot_printf

2. udelay, mdelay usually macros in netboot/ code.
Should not be a problem, use new timer.c.

3. adjust_pci_device, pcibios_ functions - already in current netboot/ 
code. Only pci_bar_size, pci_bar_start are new but probably can
use new pci.c.

4. poll_interruptions() is new
Here is a code snippet - do you see any show-stoppers here?

void poll_interruptions(void)
{
        int ch;
#ifdef FREEBSD_PXEEMU
        if (pxeemu_nbp_active)
                return;
#endif
        /* If an interruption has occured restart etherboot */
        if (iskey() && (ch = getchar(), (ch == K_ESC) || (ch == K_EOF) 
|| (ch == K_INTR))) {
                int state = (ch != K_INTR)? -1 : -3;
                longjmp(restart_etherboot, state);
        }
}


5. virt_offset - this is the main problem
Here is the declaration and usage in some inlines

/* Amount of relocation etherboot is experiencing */
extern unsigned long virt_offset;

/* Don't require identity mapped physical memory,
 * osloader.c is the only valid user at the moment.
 */
static inline unsigned long virt_to_phys(volatile const void *virt_addr)
{
        return ((unsigned long)virt_addr) + virt_offset;
}

static inline void *phys_to_virt(unsigned long phys_addr)
{
        return (void *)(phys_addr - virt_offset);
}

Unfortunately, virt_offset is defined in a .S file and I'm not
clear what it does - any thoughts on just setting it to 0?
It is used in two files start32.S, and pcibios.S

Here is where the value of virt_offset is set:


/**************************************************************************
START - Where all the fun begins....
**************************************************************************/
/* this must be the first thing in the file because we enter from the top */
        .text
        .arch i386
        .global _start
_start:
        .code32
        cli
        /* Save the initial ebp value */
        pushl   %ebp


        /*
         * See where I am running, and compute virt_offset
         */
        call    1f
1:      popl    %ebp
        subl    $1b, %ebp
        movl    %ebp, virt_offset(%ebp)

However, the variable is used and abused in many locations and
can change its value.

Awaiting edification,

Richard