Followup to: <[email protected]>
By author: Olivier Galibert <[email protected]>
In newsgroup: linux.dev.kernel
>
> I get bitched at by the build process because the kernel I get is
> around 4.5Mb compressed. i386 does not have that limitation.
> Interestingly, a diff between the two build.c gives:
>
> --- ../../../i386/boot/tools/build.c 2006-06-22 20:19:33.000000000 +0200
> +++ build.c 2006-06-22 20:19:33.000000000 +0200
> @@ -70,8 +70,7 @@
>
> int main(int argc, char ** argv)
> {
> - unsigned int i, sz, setup_sectors;
> - int c;
> + unsigned int i, c, sz, setup_sectors;
> u32 sys_size;
> byte major_root, minor_root;
> struct stat sb;
> @@ -150,8 +149,10 @@
> sz = sb.st_size;
> fprintf (stderr, "System is %d kB\n", sz/1024);
> sys_size = (sz + 15) / 16;
> - if (!is_big_kernel && sys_size > DEF_SYSSIZE)
> - die("System is too big. Try using bzImage or modules.");
> + /* 0x40000*16 = 4.0 MB, reasonable estimate for the current maximum */
> + if (sys_size > (is_big_kernel ? 0x40000 : DEF_SYSSIZE))
> + die("System is too big. Try using %smodules.",
> + is_big_kernel ? "" : "bzImage or ");
> while (sz > 0) {
> int l, n;
>
>
> which shows two things:
> 1- a8f5034540195307362d071a8b387226b410469f should have a x86-64 version
> 2- the limit looks entirely artificial
>
> So, is removing the limit prone to bite me?
>
It turns out x86-64, unlike i386, does still have a hardcoded limit,
but the limit in build.c is wrong:
kernel/head.S:
/* 40MB kernel mapping. The kernel code cannot be bigger than that.
When you change this change KERNEL_TEXT_SIZE in page.h too. */
/* (2^48-(2*1024*1024*1024)-((2^39)*511)-((2^30)*510)) = 0 */
So this should be replaced by KERNEL_TEXT_SIZE in page.h, or better,
this should be done dynamically in x86-64 too.
-hpa
-
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