Messages in this thread | | | Date | Tue, 11 Oct 2005 21:24:57 +0200 | From | Alon Bar-Lev <> | Subject | Re: [PATCH 1/1] 2.6.14-rc3 x86: COMMAND_LINE_SIZE |
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Andi Kleen wrote: > Alon Bar-Lev <alon.barlev@gmail.com> writes: > >>+config COMMAND_LINE_MAX_SIZE >>+ int "Maximum kernel command-line size" >>+ default 512 >>+ help >>+ This option allows you to specify maximum kernel command-line >>+ for kernel to handle. > > > I think making that a config is a really bad idea. What happens > when the user specifies a very large value. Or a very small one? > There are subtle dependencies with the boot loader, so this is > mostly a lie anyways. And it doesn't really safe enough memory to > bother with a CONFIG.
I don't understand this dependency. The cmd_line_ptr is a null terminated string which set by the boot loader. The kernel reads this string until the null or COMMAND_LINE_MAX_SIZE. If the user specified too large buffer or too small buffer it won't reflect the boot loader since it sets the maximum sizeof the buffer, and the kernel truncates it.
> Also the last time I tried to increase this all kind of systems > with old bootloaders exploded (e.g. lilo on systems with large EDID > information - search the archives). Have these issues been resolved now? > If yes then I would suggest to just double the default. > If not it cannot be changed anyways.
I've looked at the sources of lilo and grub, both truncate the command line to 256 into the old protocol and set the cmd_line_ptr to point to the same place.
This change will no affect current implementation of the bootloader, but will allow them to change the code to set the cmd_line_ptr to the full command line.
I think that the maximum size should be set to 1024, but since the kernel allocates a static buffer, users may wish to optimize it. So I think that a configuration option is the right place.
Best Regards, Alon Bar-Lev. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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