2005-04-17 06:20:36 +08:00
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Virtual memory map with 4 level page tables:
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2018-10-06 16:43:26 +08:00
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0000000000000000 - 00007fffffffffff (=47 bits, 128 TB) user space, different per mm
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hole caused by [47:63] sign extension
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ffff800000000000 - ffff87ffffffffff (=43 bits, 8 TB) guard hole, reserved for hypervisor
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ffff880000000000 - ffffc7ffffffffff (=46 bits, 64 TB) direct mapping of all phys. memory (page_offset_base)
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ffffc80000000000 - ffffc8ffffffffff (=40 bits, 1 TB) unused hole
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ffffc90000000000 - ffffe8ffffffffff (=45 bits, 32 TB) vmalloc/ioremap space (vmalloc_base)
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ffffe90000000000 - ffffe9ffffffffff (=40 bits, 1 TB) unused hole
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ffffea0000000000 - ffffeaffffffffff (=40 bits, 1 TB) virtual memory map (vmemmap_base)
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ffffeb0000000000 - ffffebffffffffff (=40 bits, 1 TB) unused hole
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ffffec0000000000 - fffffbffffffffff (=44 bits, 16 TB) kasan shadow memory
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fffffc0000000000 - fffffdffffffffff (=41 bits, 2 TB) unused hole
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2018-01-04 19:32:03 +08:00
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vaddr_end for KASLR
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2018-10-06 16:43:26 +08:00
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fffffe0000000000 - fffffe7fffffffff (=39 bits, 512 GB) cpu_entry_area mapping
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fffffe8000000000 - fffffeffffffffff (=39 bits, 512 GB) LDT remap for PTI
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ffffff0000000000 - ffffff7fffffffff (=39 bits, 512 GB) %esp fixup stacks
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ffffff8000000000 - fffffffeefffffff (~39 bits, ~507 GB) unused hole
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ffffffef00000000 - fffffffeffffffff (=36 bits, 64 GB) EFI region mapping space
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ffffffff00000000 - ffffffff7fffffff (=31 bits, 2 GB) unused hole
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ffffffff80000000 - ffffffff9fffffff (=29 bits, 512 MB) kernel text mapping, from phys 0
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ffffffffa0000000 - fffffffffeffffff (~31 bits, 1520 MB) module mapping space
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2017-12-12 23:56:43 +08:00
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[fixmap start] - ffffffffff5fffff kernel-internal fixmap range
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2018-10-06 16:43:26 +08:00
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ffffffffff600000 - ffffffffff600fff ( =4 kB) legacy vsyscall ABI
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ffffffffffe00000 - ffffffffffffffff ( =2 MB) unused hole
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2005-04-17 06:20:36 +08:00
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2017-03-30 16:07:27 +08:00
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Virtual memory map with 5 level page tables:
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2018-10-06 16:43:26 +08:00
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0000000000000000 - 00ffffffffffffff (=56 bits, 64 PB) user space, different per mm
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hole caused by [56:63] sign extension
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ff00000000000000 - ff0fffffffffffff (=52 bits, 4 PB) guard hole, reserved for hypervisor
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ff10000000000000 - ff8fffffffffffff (=55 bits, 32 PB) direct mapping of all phys. memory (page_offset_base)
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ff90000000000000 - ff9fffffffffffff (=52 bits, 4 PB) LDT remap for PTI
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ffa0000000000000 - ffd1ffffffffffff (=53 bits, 12800 TB) vmalloc/ioremap space (vmalloc_base)
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ffd2000000000000 - ffd3ffffffffffff (=49 bits, 512 TB) unused hole
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ffd4000000000000 - ffd5ffffffffffff (=49 bits, 512 TB) virtual memory map (vmemmap_base)
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ffd6000000000000 - ffdeffffffffffff (~51 bits, 2304 TB) unused hole
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ffdf000000000000 - fffffdffffffffff (~53 bits, ~8 PB) kasan shadow memory
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fffffc0000000000 - fffffdffffffffff (=41 bits, 2 TB) unused hole
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2018-01-04 19:32:03 +08:00
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vaddr_end for KASLR
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2018-10-06 16:43:26 +08:00
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fffffe0000000000 - fffffe7fffffffff (=39 bits, 512 GB) cpu_entry_area mapping
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fffffe8000000000 - fffffeffffffffff (=39 bits, 512 GB) unused hole
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ffffff0000000000 - ffffff7fffffffff (=39 bits, 512 GB) %esp fixup stacks
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ffffff8000000000 - ffffffeeffffffff (~39 bits, 444 GB) unused hole
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ffffffef00000000 - fffffffeffffffff (=36 bits, 64 GB) EFI region mapping space
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ffffffff00000000 - ffffffff7fffffff (31 bits, 2 GB) unused hole
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ffffffff80000000 - ffffffff9fffffff (=29 bits, 512 MB) kernel text mapping, from phys 0
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ffffffffa0000000 - fffffffffeffffff (~31 bits, 1520 MB) module mapping space
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2017-12-12 23:56:43 +08:00
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[fixmap start] - ffffffffff5fffff kernel-internal fixmap range
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2018-10-06 16:43:26 +08:00
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ffffffffff600000 - ffffffffff600fff ( =4 kB) legacy vsyscall ABI
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ffffffffffe00000 - ffffffffffffffff ( =2 MB) unused hole
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2017-03-30 16:07:27 +08:00
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Architecture defines a 64-bit virtual address. Implementations can support
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less. Currently supported are 48- and 57-bit virtual addresses. Bits 63
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2017-12-05 20:34:54 +08:00
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through to the most-significant implemented bit are sign extended.
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This causes hole between user space and kernel addresses if you interpret them
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as unsigned.
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2017-03-30 16:07:27 +08:00
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2007-02-13 20:26:23 +08:00
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The direct mapping covers all memory in the system up to the highest
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2005-11-06 00:25:54 +08:00
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memory address (this means in some cases it can also include PCI memory
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2007-02-13 20:26:23 +08:00
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holes).
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2005-11-06 00:25:54 +08:00
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2017-03-30 16:07:27 +08:00
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vmalloc space is lazily synchronized into the different PML4/PML5 pages of
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the processes using the page fault handler, with init_top_pgt as
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2005-04-17 06:20:36 +08:00
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reference.
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2015-11-28 05:09:35 +08:00
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We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual
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memory window (this size is arbitrary, it can be raised later if needed).
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The mappings are not part of any other kernel PGD and are only available
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during EFI runtime calls.
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2013-11-01 00:25:08 +08:00
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x86/mm: Implement ASLR for kernel memory regions
Randomizes the virtual address space of kernel memory regions for
x86_64. This first patch adds the infrastructure and does not randomize
any region. The following patches will randomize the physical memory
mapping, vmalloc and vmemmap regions.
This security feature mitigates exploits relying on predictable kernel
addresses. These addresses can be used to disclose the kernel modules
base addresses or corrupt specific structures to elevate privileges
bypassing the current implementation of KASLR. This feature can be
enabled with the CONFIG_RANDOMIZE_MEMORY option.
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. No performance impact
was detected while testing the feature.
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 & PUD page table levels to increase possible addresses. The
physical memory mapping code was adapted to support 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).
x86/dump_pagetable was updated to correctly display each region.
Updated documentation on x86_64 memory layout accordingly.
Performance data, after all patches in the series:
Kernbench shows almost no difference (-+ less than 1%):
Before:
Average Optimal load -j 12 Run (std deviation): Elapsed Time 102.63 (1.2695)
User Time 1034.89 (1.18115) System Time 87.056 (0.456416) Percent CPU 1092.9
(13.892) Context Switches 199805 (3455.33) Sleeps 97907.8 (900.636)
After:
Average Optimal load -j 12 Run (std deviation): Elapsed Time 102.489 (1.10636)
User Time 1034.86 (1.36053) System Time 87.764 (0.49345) Percent CPU 1095
(12.7715) Context Switches 199036 (4298.1) Sleeps 97681.6 (1031.11)
Hackbench shows 0% difference on average (hackbench 90 repeated 10 times):
attemp,before,after 1,0.076,0.069 2,0.072,0.069 3,0.066,0.066 4,0.066,0.068
5,0.066,0.067 6,0.066,0.069 7,0.067,0.066 8,0.063,0.067 9,0.067,0.065
10,0.068,0.071 average,0.0677,0.0677
Signed-off-by: Thomas Garnier <thgarnie@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Alexander Kuleshov <kuleshovmail@gmail.com>
Cc: Alexander Popov <alpopov@ptsecurity.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lv Zheng <lv.zheng@intel.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: kernel-hardening@lists.openwall.com
Cc: linux-doc@vger.kernel.org
Link: http://lkml.kernel.org/r/1466556426-32664-6-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-06-22 08:47:02 +08:00
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Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all
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physical memory, vmalloc/ioremap space and virtual memory map are randomized.
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Their order is preserved but their base will be offset early at boot time.
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2018-01-04 19:32:03 +08:00
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Be very careful vs. KASLR when changing anything here. The KASLR address
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range must not overlap with anything except the KASAN shadow area, which is
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correct as KASAN disables KASLR.
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