Commit 88f3aec7 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86: fix spontaneous reboot with allyesconfig bzImage 



recently the 64-bit allyesconfig bzImage kernel started spontaneously
rebooting during early bootup.

after a few fun hours spent with early init debugging, it turns out
that we've got this rather annoying limit on the size of the kernel
image:

      #define KERNEL_TEXT_SIZE  (40*1024*1024)

which limit my vmlinux just happened to pass:

       text           data       bss        dec       hex   filename
   29703744        4222751   8646224c   42572719   2899baf   vmlinux

40 MB is 42572719 bytes, so my vmlinux was just 1.5% above this limit :-/

So it happily crashed right in head_64.S, which - as we all know - is
the most debuggable code in the whole architecture ;-)

So increase the limit to allow an up to 128MB kernel image to be mapped.
(should anyone be that crazy or lazy)

We have a full 4K of pagetable (level2_kernel_pgt) allocated for these
mappings already, so there's no RAM overhead and the limit was rather
pointless and arbitrary.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 3b57bc46

arch/x86/kernel/head_64.S

+14 −8
Original line number Diff line number Diff line
@@ -379,15 +379,21 @@ NEXT_PAGE(level2_ident_pgt) 
	/* Since I easily can, map the first 1G.

	 * Don't set NX because code runs from these pages.

	 */

	PMDS(0x0000000000000000, __PAGE_KERNEL_LARGE_EXEC, PTRS_PER_PMD)

	PMDS(0, __PAGE_KERNEL_LARGE_EXEC, PTRS_PER_PMD)



NEXT_PAGE(level2_kernel_pgt)

	/* 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 */

	PMDS(0x0000000000000000, __PAGE_KERNEL_LARGE_EXEC|_PAGE_GLOBAL, KERNEL_TEXT_SIZE/PMD_SIZE)

	/* Module mapping starts here */

	.fill	(PTRS_PER_PMD - (KERNEL_TEXT_SIZE/PMD_SIZE)),8,0

	/*

	 * 128 MB kernel mapping. We spend a full page on this pagetable

	 * anyway.

	 *

	 * The kernel code+data+bss must not be bigger than that.

	 *

	 * (NOTE: at +128MB starts the module area, see MODULES_VADDR.

	 *  If you want to increase this then increase MODULES_VADDR

	 *  too.)

	 */

	PMDS(0, __PAGE_KERNEL_LARGE_EXEC|_PAGE_GLOBAL,

		KERNEL_TEXT_SIZE/PMD_SIZE)



NEXT_PAGE(level2_spare_pgt)

	.fill   512, 8, 0

arch/x86/mm/init_64.c

+3 −2
Original line number Diff line number Diff line
@@ -172,8 +172,9 @@ set_pte_phys(unsigned long vaddr, unsigned long phys, pgprot_t prot) 
}



/*

 * The head.S code sets up the kernel high mapping from:

 * __START_KERNEL_map to __START_KERNEL_map + KERNEL_TEXT_SIZE

 * The head.S code sets up the kernel high mapping:

 *

 *   from __START_KERNEL_map to __START_KERNEL_map + size (== _end-_text)

 *

 * phys_addr holds the negative offset to the kernel, which is added

 * to the compile time generated pmds. This results in invalid pmds up

include/asm-x86/page_64.h

+6 −2
Original line number Diff line number Diff line
@@ -47,7 +47,11 @@ 
#define __PHYSICAL_MASK_SHIFT	46

#define __VIRTUAL_MASK_SHIFT	48



#define KERNEL_TEXT_SIZE  (40*1024*1024)

/*

 * Kernel image size is limited to 128 MB (see level2_kernel_pgt in

 * arch/x86/kernel/head_64.S), and it is mapped here:

 */

#define KERNEL_TEXT_SIZE	(128*1024*1024)

#define KERNEL_TEXT_START	_AC(0xffffffff80000000, UL)



#ifndef __ASSEMBLY__

CRA Git | Maintained and supported by SUSTech CRA and CCSE