[syslinux] inconsistent Int 22h local boot

[Miguel]

>> Upgrade to 3.54 did not solve the problem ...
>> same behavior ... Dell 1435
>> still returns from Int 22h AX=0014.
>> I'll try to collect more data.
>
> That is very odd indeed.

Agreed

> The code to do it shouldn't even have a way to
> return... I traced through the execution and there
> doesn't seem any possibility.  It would be useful to
> know what values are returned by INT 22h, AX=000Ah.

In addition to AX=000Ah, I also did AX=0015h.

I have attached a screen shot ... don't know if it will make it to the
mailing list.

Int22h AX=000Ah -> AL=32h DX=0201h

Int22h AX=0015h -> CX=0000h :

Note that the flag byte count is 0 ... based upon comboot.doc I expected a
value of 1.

To make things more confuzing/puzzling, if I put 'localboot 0' in the
pxelinux.cfg/MACADDR file then it successfully exits and boots from the
local hard drive.

I took a look at the code in com32/modules/menumain.c ... which looks like
the code that processes pxelinux.cfg/MACADDR files. I observe that it
calls Int22h AX=0014h, exactly as I am doing. It works from the boot:
prompt but does not work from my code ... very strange.

Screen shot is attached.
Source code is below.

Miguel

----


void syslinux_localboot(int localboottype) {
  static com32sys_t regs;
  int i;

  for (i = 0; i < 25; ++i) // clear screen
    printf("\n");
  printf("initiating localboot\n");

  localboottype = localboottype; // stop complaining about unused variable

  memset(&regs, 0, sizeof regs);
  regs.eax.w[0] = 0x000A;
  __intcall(0x22, &regs, &regs);
  printf("Int22h AX=000Ah -> AL=%02Xh DX=%04Xh\n\n",
         regs.eax.b[0], regs.edx.w[0]);

  memset(&regs, 0, sizeof regs);
  regs.eax.w[0] = 0x0015;
  __intcall(0x22, &regs, &regs);
  printf("Int22h AX=0015h -> CX=%04Xh :", regs.ecx.w[0]);
  {
    unsigned count = regs.ecx.w[0];
    unsigned char * flags_ptr = MK_PTR(regs.es, regs.ebx.w[0]);
    unsigned i;
    for (i = 0; i < count; ++i)
      printf(" %02Xh", flags_ptr[i]);
    printf("\n\n");
  }


  memset(&regs, 0, sizeof regs);
  regs.eax.w[0] = 0x0014;
  regs.edx.w[0] = (unsigned short) localboottype;
  printf("calling Int22h AX=%04Xh DX=%04Xh\n\n",
         regs.eax.w[0], regs.edx.w[0]);
  __intcall(0x22, &regs, NULL);

  // alternate method ... but requires the label 'localboot' in the
  // pxelinux.cfg file
  //
  //  char * bounce = __com32.cs_bounce;
  //  strcpy(bounce, "localboot");
  //
  //  regs.eax.w[0] = 0x0003;
  //  regs.es = SEG(bounce);
  //  regs.ebx.w[0] = OFFS(bounce);
  //  __intcall(0x22, &regs, NULL);

  printf("Why am I here?\n");
  syslinux_sleep(5);
  exit(0);
}



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