linux/arch/x86/mm/kaslr.c
Mike Rapoport 57c8a661d9 mm: remove include/linux/bootmem.h
Move remaining definitions and declarations from include/linux/bootmem.h
into include/linux/memblock.h and remove the redundant header.

The includes were replaced with the semantic patch below and then
semi-automated removal of duplicated '#include <linux/memblock.h>

@@
@@
- #include <linux/bootmem.h>
+ #include <linux/memblock.h>

[sfr@canb.auug.org.au: dma-direct: fix up for the removal of linux/bootmem.h]
  Link: http://lkml.kernel.org/r/20181002185342.133d1680@canb.auug.org.au
[sfr@canb.auug.org.au: powerpc: fix up for removal of linux/bootmem.h]
  Link: http://lkml.kernel.org/r/20181005161406.73ef8727@canb.auug.org.au
[sfr@canb.auug.org.au: x86/kaslr, ACPI/NUMA: fix for linux/bootmem.h removal]
  Link: http://lkml.kernel.org/r/20181008190341.5e396491@canb.auug.org.au
Link: http://lkml.kernel.org/r/1536927045-23536-30-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guan Xuetao <gxt@pku.edu.cn>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Serge Semin <fancer.lancer@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-10-31 08:54:16 -07:00

221 lines
6.3 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* This file implements KASLR memory randomization for x86_64. It randomizes
* the virtual address space of kernel memory regions (physical memory
* mapping, vmalloc & vmemmap) for x86_64. This security feature mitigates
* exploits relying on predictable kernel addresses.
*
* Entropy is generated using the KASLR early boot functions now shared in
* the lib directory (originally written by Kees Cook). Randomization is
* done on PGD & P4D/PUD page table levels to increase possible addresses.
* The physical memory mapping code was adapted to support P4D/PUD level
* virtual addresses. This implementation on the best configuration provides
* 30,000 possible virtual addresses in average for each memory region.
* An additional low memory page is used to ensure each CPU can start with
* a PGD aligned virtual address (for realmode).
*
* The order of each memory region is not changed. The feature looks at
* the available space for the regions based on different configuration
* options and randomizes the base and space between each. The size of the
* physical memory mapping is the available physical memory.
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/random.h>
#include <linux/memblock.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/setup.h>
#include <asm/kaslr.h>
#include "mm_internal.h"
#define TB_SHIFT 40
/*
* The end address could depend on more configuration options to make the
* highest amount of space for randomization available, but that's too hard
* to keep straight and caused issues already.
*/
static const unsigned long vaddr_end = CPU_ENTRY_AREA_BASE;
/*
* Memory regions randomized by KASLR (except modules that use a separate logic
* earlier during boot). The list is ordered based on virtual addresses. This
* order is kept after randomization.
*/
static __initdata struct kaslr_memory_region {
unsigned long *base;
unsigned long size_tb;
} kaslr_regions[] = {
{ &page_offset_base, 0 },
{ &vmalloc_base, 0 },
{ &vmemmap_base, 1 },
};
/* Get size in bytes used by the memory region */
static inline unsigned long get_padding(struct kaslr_memory_region *region)
{
return (region->size_tb << TB_SHIFT);
}
/*
* Apply no randomization if KASLR was disabled at boot or if KASAN
* is enabled. KASAN shadow mappings rely on regions being PGD aligned.
*/
static inline bool kaslr_memory_enabled(void)
{
return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN);
}
/* Initialize base and padding for each memory region randomized with KASLR */
void __init kernel_randomize_memory(void)
{
size_t i;
unsigned long vaddr_start, vaddr;
unsigned long rand, memory_tb;
struct rnd_state rand_state;
unsigned long remain_entropy;
vaddr_start = pgtable_l5_enabled() ? __PAGE_OFFSET_BASE_L5 : __PAGE_OFFSET_BASE_L4;
vaddr = vaddr_start;
/*
* These BUILD_BUG_ON checks ensure the memory layout is consistent
* with the vaddr_start/vaddr_end variables. These checks are very
* limited....
*/
BUILD_BUG_ON(vaddr_start >= vaddr_end);
BUILD_BUG_ON(vaddr_end != CPU_ENTRY_AREA_BASE);
BUILD_BUG_ON(vaddr_end > __START_KERNEL_map);
if (!kaslr_memory_enabled())
return;
kaslr_regions[0].size_tb = 1 << (__PHYSICAL_MASK_SHIFT - TB_SHIFT);
kaslr_regions[1].size_tb = VMALLOC_SIZE_TB;
/*
* Update Physical memory mapping to available and
* add padding if needed (especially for memory hotplug support).
*/
BUG_ON(kaslr_regions[0].base != &page_offset_base);
memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) +
CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING;
/* Adapt phyiscal memory region size based on available memory */
if (memory_tb < kaslr_regions[0].size_tb)
kaslr_regions[0].size_tb = memory_tb;
/* Calculate entropy available between regions */
remain_entropy = vaddr_end - vaddr_start;
for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++)
remain_entropy -= get_padding(&kaslr_regions[i]);
prandom_seed_state(&rand_state, kaslr_get_random_long("Memory"));
for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) {
unsigned long entropy;
/*
* Select a random virtual address using the extra entropy
* available.
*/
entropy = remain_entropy / (ARRAY_SIZE(kaslr_regions) - i);
prandom_bytes_state(&rand_state, &rand, sizeof(rand));
if (pgtable_l5_enabled())
entropy = (rand % (entropy + 1)) & P4D_MASK;
else
entropy = (rand % (entropy + 1)) & PUD_MASK;
vaddr += entropy;
*kaslr_regions[i].base = vaddr;
/*
* Jump the region and add a minimum padding based on
* randomization alignment.
*/
vaddr += get_padding(&kaslr_regions[i]);
if (pgtable_l5_enabled())
vaddr = round_up(vaddr + 1, P4D_SIZE);
else
vaddr = round_up(vaddr + 1, PUD_SIZE);
remain_entropy -= entropy;
}
}
static void __meminit init_trampoline_pud(void)
{
unsigned long paddr, paddr_next;
pgd_t *pgd;
pud_t *pud_page, *pud_page_tramp;
int i;
pud_page_tramp = alloc_low_page();
paddr = 0;
pgd = pgd_offset_k((unsigned long)__va(paddr));
pud_page = (pud_t *) pgd_page_vaddr(*pgd);
for (i = pud_index(paddr); i < PTRS_PER_PUD; i++, paddr = paddr_next) {
pud_t *pud, *pud_tramp;
unsigned long vaddr = (unsigned long)__va(paddr);
pud_tramp = pud_page_tramp + pud_index(paddr);
pud = pud_page + pud_index(vaddr);
paddr_next = (paddr & PUD_MASK) + PUD_SIZE;
*pud_tramp = *pud;
}
set_pgd(&trampoline_pgd_entry,
__pgd(_KERNPG_TABLE | __pa(pud_page_tramp)));
}
static void __meminit init_trampoline_p4d(void)
{
unsigned long paddr, paddr_next;
pgd_t *pgd;
p4d_t *p4d_page, *p4d_page_tramp;
int i;
p4d_page_tramp = alloc_low_page();
paddr = 0;
pgd = pgd_offset_k((unsigned long)__va(paddr));
p4d_page = (p4d_t *) pgd_page_vaddr(*pgd);
for (i = p4d_index(paddr); i < PTRS_PER_P4D; i++, paddr = paddr_next) {
p4d_t *p4d, *p4d_tramp;
unsigned long vaddr = (unsigned long)__va(paddr);
p4d_tramp = p4d_page_tramp + p4d_index(paddr);
p4d = p4d_page + p4d_index(vaddr);
paddr_next = (paddr & P4D_MASK) + P4D_SIZE;
*p4d_tramp = *p4d;
}
set_pgd(&trampoline_pgd_entry,
__pgd(_KERNPG_TABLE | __pa(p4d_page_tramp)));
}
/*
* Create PGD aligned trampoline table to allow real mode initialization
* of additional CPUs. Consume only 1 low memory page.
*/
void __meminit init_trampoline(void)
{
if (!kaslr_memory_enabled()) {
init_trampoline_default();
return;
}
if (pgtable_l5_enabled())
init_trampoline_p4d();
else
init_trampoline_pud();
}