Syslinux - Apr 2008 - extlinux: missing text on serial output

Hi!

Using the following extlinux.conf

serial 0x2f8 57600 0x013
# that is, RTS/CTS flow control on COM2

prompt 1
timeout 100

say Select 'linux' or 'xen'.
say Automatically booting 'xen' in 10 seconds.

default xen

label linux
  kernel /vmlinuz-2.6.18-6-686
  append initrd=/initrd.img-2.6.18-6-686 root=/dev/mapper/xen1-root ro
console=tty0 console=ttyS1,57600n8r noresume

label xen
  kernel mboot.c32
  append /xen-3.2-1-i386.gz com2=auto,8n1 console=com2L,vga dom0_mem=256M ---
/vmlinuz-2.6.18-6-xen-686 root=/dev/mapper/xen2-root ro xencons=xvc console=tty0
console=xvc noresume 3 --- /initrd.img-2.6.18-6-xen-686

I get this output on my monitor:

EXTLINUX 3.63 2008-04-10 EBIOS Copyright (C) 1994-2008 H. Peter Anvin
Select 'linux' or 'xen'.                         
Automatically booting 'xen' in 10 seconds.       
boot: 

Which is perfectly fine, but I'm deprived of the 'say' output when
looking at the serial console (lo', EBIOS is also missing!  And a CR
after the multiboot copyright string!)

EXTLINUX 3.63 2008-04-10  Copyright (C) 1994-2008 H. Peter Anvin


boot: 
COM32 Multiboot loader v0.2.  Copyright (C) 2005-2006 Tim Deegan.
                                                                 Kernel:
/xen-3.2-1-i386.gz com2=auto,

Can somebody confirm that it's a bug?
-- 
Thanks,
Feri.

Ferenc Wagner wrote:
> 
> EXTLINUX 3.63 2008-04-10 EBIOS Copyright (C) 1994-2008 H. Peter Anvin
> Select 'linux' or 'xen'.                         
> Automatically booting 'xen' in 10 seconds.       
> boot: 
> 
> Which is perfectly fine, but I'm deprived of the 'say' output
when
> looking at the serial console (lo', EBIOS is also missing!  And a CR
> after the multiboot copyright string!)
> 
> EXTLINUX 3.63 2008-04-10  Copyright (C) 1994-2008 H. Peter Anvin
> 
> 
> boot: 
> COM32 Multiboot loader v0.2.  Copyright (C) 2005-2006 Tim Deegan.
>                                                                  Kernel:
/xen-3.2-1-i386.gz com2=auto,
> 
> Can somebody confirm that it's a bug?
It's easy enough to see how the EBIOS would be missing - the banner is 
printed on the screen before the config file is written, so it's issued 
separately for the serial console.  The CR from the multiboot module is 
also reasonably easy to explain (it's a C environment, and at some point 
\n -> \r\n).  However, "say" not outputting on the serial console
is
weird and serious.  I will look into it.

	-hpa

Ferenc Wagner wrote:
> 
>> Compiling with NASM 2.02 and then running my Extlinux+vesamenu.c32 test
>> under Qemu works just fine.  Perhaps you could send me a copy of 
>> extlinux.bin from your compile session (or even better, tar up a full 
>> build tree)?
> 
> I will send you the full build tree tomorrow, this GPRS connection
> isn't up to that.  But I attached extlinux.bin and a disk image
> freezing into reboot.c32.
> 
Okay, no need to... the issue is the following:

-000011d0  e8 fc 0f 10 00 66 bb 1a  8e fa fc 89 25 9c f7 00
+000011d0  e8 2b 82 0f 00 66 bb 1a  8e fa fc 89 25 9c f7 00
               ^^^^^^^^^^^

The code on top is yours, the one on the bottom is mine.  This is 
supposed to be a near jump to the COM32 entrypoint, 0x101000, from 
source address 0x8dd0 (0x7c00+0x11d0).  The correct value for the jump 
is 0x000f822b (0x1010000-0x8dd0-5); somehow in your case the linker puts 
0x00100ffc instead there, which implies that it failed to subtract the 
PC offset, 0x8dd1 (the -4 is handled by the assembler.)

However, either NASM 2.02 or NASM 2.03.01 give, for me:

     11d0:       e8 fc 0f 10 00          call   1021d1 <pm_entry+0x11d1>
                         11d1: R_386_PC32        *ABS*

     11d0:       e8 fc 0f 10 00          call   1021d1 <pm_entry+0x11d1>
                         11d1: R_386_PC32        *ABS*

... and, as far as I can tell, this is correct behaviour.

This implies that the difference is an ld difference.  What version of 
binutils are you running?  Mine is:

: tazenda 65 ; ld -version
GNU ld version 2.17.50.0.18-1 20070731

	-hpa

Ferenc Wagner wrote:
> 
>> Compiling with NASM 2.02 and then running my Extlinux+vesamenu.c32 test
>> under Qemu works just fine.  Perhaps you could send me a copy of 
>> extlinux.bin from your compile session (or even better, tar up a full 
>> build tree)?
> 
> I will send you the full build tree tomorrow, this GPRS connection
> isn't up to that.  But I attached extlinux.bin and a disk image
> freezing into reboot.c32.
> 
Okay, I installed Debian Etch under KVM, and was able to reproduce this 
problem.  It appears to be a problem with ld 2.17, which is the default 
version in Etch; it does not depend on the version of NASM.

There isn't all that much I can do about it, other than use an indirect 
call here (see patch.)

I'm slightly hesitant to add this patch to the main code, though, to 
support a very old and obviously broken linker.

	-hpa
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