Messages in this thread | | | Date | Fri, 14 Apr 2006 21:09:36 +0300 | From | Alon Bar-Lev <> | Subject | Re: [PATCH][TAKE 3] THE LINUX/I386 BOOT PROTOCOL - Breaking the 256 limit |
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H. Peter Anvin wrote: > Alon Bar-Lev wrote: >> diff -urNp linux-2.6.16/Documentation/i386/boot.txt >> linux-2.6.16.new/Documentation/i386/boot.txt >> --- linux-2.6.16/Documentation/i386/boot.txt 2006-03-20 >> 07:53:29.000000000 +0200 >> +++ linux-2.6.16.new/Documentation/i386/boot.txt 2006-04-14 >> 01:55:47.000000000 +0300 >> @@ -235,11 +235,8 @@ loader to communicate with the kernel. relevant >> to the boot loader itself, see "special command line options" >> below. >> >> -The kernel command line is a null-terminated string currently up to >> -255 characters long, plus the final null. A string that is too long >> -will be automatically truncated by the kernel, a boot loader may allow >> -a longer command line to be passed to permit future kernels to extend >> -this limit. >> +The kernel command line is a null-terminated string. A string that is >> too >> +long will be automatically truncated by the kernel. >> >> If the boot protocol version is 2.02 or later, the address of the >> kernel command line is given by the header field cmd_line_ptr (see >> @@ -260,6 +257,9 @@ command line is entered using the follow >> covered by setup_move_size, so you may need to adjust this >> field. >> >> + The kernel command line *must* be 256 bytes including the >> + final null. >> + >> >> **** SAMPLE BOOT CONFIGURATION >> > > This chunk is confusing at the very best. > > -hpa >
Hello,
The problem is that boot loader developers did not understand the old statement: "A string that is too long will be automatically truncated by the kernel, a boot loader may allow a longer command line to be passed to permit future kernels to extend this limit."
Most of them handed the same buffer to < 2.02 protocols and >= 2.0.2 protocols. When I've opened bugs against that they claimed that they follow instructions since the 256 limit was explicitly mentioned. I've ended up in patching GRUB my-self to allow this.
I thought that this should be made clearer... But maybe I did not write it too well.
I've removed the 255+1 limitation from the boot protocol main description, so there will be no known limit there... And moved it to the <2.02 section notes.
Can you please suggest a different phrasing? Or maybe you think that it is not needed at all... But then I have a problem of making boot loader fix their code.
Best Regards, Alon Bar-Lev.
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