Alon Bar-Lev wrote:
Hello Peter,
I am sorry that I am contacting you directly... Please refer me to
correct contact if you are not the one.
Lately, I've found that 256 bytes long kernel parameters are not enough
for my configuration.
I've found the place where the kernel defines the length, I've actually
found it in two places... I cannot understand why...
include/asm-i386/param.h: #define COMMAND_LINE_SIZE 256
include/asm-i386/setup.h: #define COMMAND_LINE_SIZE 256
Now... I've added an entry in the kernel configuration menu so that I
can define these constants using menuconfig.
I was quite happy...
But then I've got into a discussion with grub's development team...
From what I've read in the Documentation/i386/boot.txt I understood
that if I use boot protocol 2.02+ there should be no reason for 256 byte
limitation on the string pointed by the cmd_line_ptr, so I guessed they
will deliver the command-line twice once for the old protocol truncated,
and once for the new protocol not truncated.
Grub and Lilo approach is to point the cmd_line_ptr to the old
protocol's command line, thus truncating it to 256.
I'm just wondering... Can the 256 limit be broken, without modifying the
boot protocol?
I think it can... But I need a formal answer so I can push it forward.
Yes, it can. Several people on the SYSLINUX mailing list have tried
this, and it works just fine. The current version of SYSLINUX has a
limit of 511 characters (because of memory management reasons inside
SYSLINUX) instead of 255 (plus null).
I think someone on the SYSLINUX mailing list already sent a patch to
akpm to make 512 the default; making it configurable would be a better
idea. Feel free to send your patch through me.
-hpa
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