Commit e5ceb9a0 authored by Arvind Sankar's avatar Arvind Sankar Committed by Borislav Petkov
Browse files

x86/boot/64: Initialize 5-level paging variables earlier 



Commit

  ca0e22d4 ("x86/boot/compressed/64: Always switch to own page table")

started using a new set of pagetables even without KASLR.

After that commit, initialize_identity_maps() is called before the
5-level paging variables are setup in choose_random_location(), which
will not work if 5-level paging is actually enabled.

Fix this by moving the initialization of __pgtable_l5_enabled,
pgdir_shift and ptrs_per_p4d into cleanup_trampoline(), which is called
immediately after the finalization of whether the kernel is executing
with 4- or 5-level paging. This will be earlier than anything that might
require those variables, and keeps the 4- vs 5-level paging code all in
one place.

Fixes: ca0e22d4 ("x86/boot/compressed/64: Always switch to own page table")
Signed-off-by: default avatarArvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarJoerg Roedel <jroedel@suse.de>
Tested-by: default avatarJoerg Roedel <jroedel@suse.de>
Tested-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lkml.kernel.org/r/20201010191110.4060905-1-nivedita@alum.mit.edu
parent da9803df

arch/x86/boot/compressed/ident_map_64.c

+0 −6
Original line number Diff line number Diff line
@@ -33,12 +33,6 @@ 
#define __PAGE_OFFSET __PAGE_OFFSET_BASE

#include "../../mm/ident_map.c"



#ifdef CONFIG_X86_5LEVEL

unsigned int __pgtable_l5_enabled;

unsigned int pgdir_shift = 39;

unsigned int ptrs_per_p4d = 1;

#endif



/* Used by PAGE_KERN* macros: */

pteval_t __default_kernel_pte_mask __read_mostly = ~0;

arch/x86/boot/compressed/kaslr.c

+0 −8
Original line number Diff line number Diff line
@@ -840,14 +840,6 @@ void choose_random_location(unsigned long input, 
		return;

	}



#ifdef CONFIG_X86_5LEVEL

	if (__read_cr4() & X86_CR4_LA57) {

		__pgtable_l5_enabled = 1;

		pgdir_shift = 48;

		ptrs_per_p4d = 512;

	}

#endif



	boot_params->hdr.loadflags |= KASLR_FLAG;



	if (IS_ENABLED(CONFIG_X86_32))

arch/x86/boot/compressed/pgtable_64.c

+16 −0
Original line number Diff line number Diff line
@@ -8,6 +8,13 @@ 
#define BIOS_START_MIN		0x20000U	/* 128K, less than this is insane */

#define BIOS_START_MAX		0x9f000U	/* 640K, absolute maximum */



#ifdef CONFIG_X86_5LEVEL

/* __pgtable_l5_enabled needs to be in .data to avoid being cleared along with .bss */

unsigned int __section(.data) __pgtable_l5_enabled;

unsigned int __section(.data) pgdir_shift = 39;

unsigned int __section(.data) ptrs_per_p4d = 1;

#endif



struct paging_config {

	unsigned long trampoline_start;

	unsigned long l5_required;
@@ -198,4 +205,13 @@ void cleanup_trampoline(void *pgtable) 


	/* Restore trampoline memory */

	memcpy(trampoline_32bit, trampoline_save, TRAMPOLINE_32BIT_SIZE);



	/* Initialize variables for 5-level paging */

#ifdef CONFIG_X86_5LEVEL

	if (__read_cr4() & X86_CR4_LA57) {

		__pgtable_l5_enabled = 1;

		pgdir_shift = 48;

		ptrs_per_p4d = 512;

	}

#endif

}

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