x86/mm/doc: Enhance the x86-64 virtual memory layout descriptions
After the cleanups from Baoquan He, make it even more readable:
- Remove the 'bits' area size column: it's pretty pointless and was even
wrong for some of the entries. Given that MB, GB, TB, PT are 10, 20,
30 and 40 bits, a "8 TB" size description makes it obvious that it's
43 bits.
- Introduce an "offset" column:
--------------------------------------------------------------------------------
start addr | offset | end addr | size | VM area description
-----------------|------------|------------------|---------|--------------------
...
ffff880000000000 | -120 TB | ffffc7ffffffffff | 64 TB | direct mapping of all physical memory (page_offset_base),
this is what limits max physical memory supported.
The -120 TB notation makes it obvious where this particular virtual memory
region starts: 120 TB down from the top of the 64-bit virtual memory space.
Especially the layout of the kernel mappings is a *lot* more obvious when
written this way, plus it's much easier to compare it with the size column
and understand/check/validate and modify the kernel's layout in the future.
- Mark the part from where the 47-bit and 56-bit kernel layouts are 100% identical,
this starts at the -512 GB offset and the EFI region.
- Re-shuffle the size desciptions to be continous blocks of sizes, instead of the
often mixed size. I.e. write "0.5 TB" instead of "512 GB" if we are still in
the TB-granular region of the map.
- Make the 47-bit and 56-bit descriptions use the *exact* same layout and wording,
and only differ where there's a material difference. This makes it easy to compare
the two tables side by side by switching between two terminal tabs.
- Plus enhance a lot of other stylistic/typographical details: make the tables
explicitly tabular, add headers, enhance certain entries, etc. etc.
Note that there are some apparent errors in the tables as well, but I'll fix
them in a separate patch to make it easier to review/validate.
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: corbet@lwn.net
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: thgarnie@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-10-06 19:41:12 +08:00
|
|
|
====================================================
|
|
|
|
|
Complete virtual memory map with 4-level page tables
|
|
|
|
|
====================================================
|
2005-04-17 06:20:36 +08:00
|
|
|
|
x86/mm/doc: Enhance the x86-64 virtual memory layout descriptions
After the cleanups from Baoquan He, make it even more readable:
- Remove the 'bits' area size column: it's pretty pointless and was even
wrong for some of the entries. Given that MB, GB, TB, PT are 10, 20,
30 and 40 bits, a "8 TB" size description makes it obvious that it's
43 bits.
- Introduce an "offset" column:
--------------------------------------------------------------------------------
start addr | offset | end addr | size | VM area description
-----------------|------------|------------------|---------|--------------------
...
ffff880000000000 | -120 TB | ffffc7ffffffffff | 64 TB | direct mapping of all physical memory (page_offset_base),
this is what limits max physical memory supported.
The -120 TB notation makes it obvious where this particular virtual memory
region starts: 120 TB down from the top of the 64-bit virtual memory space.
Especially the layout of the kernel mappings is a *lot* more obvious when
written this way, plus it's much easier to compare it with the size column
and understand/check/validate and modify the kernel's layout in the future.
- Mark the part from where the 47-bit and 56-bit kernel layouts are 100% identical,
this starts at the -512 GB offset and the EFI region.
- Re-shuffle the size desciptions to be continous blocks of sizes, instead of the
often mixed size. I.e. write "0.5 TB" instead of "512 GB" if we are still in
the TB-granular region of the map.
- Make the 47-bit and 56-bit descriptions use the *exact* same layout and wording,
and only differ where there's a material difference. This makes it easy to compare
the two tables side by side by switching between two terminal tabs.
- Plus enhance a lot of other stylistic/typographical details: make the tables
explicitly tabular, add headers, enhance certain entries, etc. etc.
Note that there are some apparent errors in the tables as well, but I'll fix
them in a separate patch to make it easier to review/validate.
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: corbet@lwn.net
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: thgarnie@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-10-06 19:41:12 +08:00
|
|
|
Notes:
|
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|
|
|
|
|
|
|
- Negative addresses such as "-23 TB" are absolute addresses in bytes, counted down
|
|
|
|
|
from the top of the 64-bit address space. It's easier to understand the layout
|
|
|
|
|
when seen both in absolute addresses and in distance-from-top notation.
|
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|
|
For example 0xffffe90000000000 == -23 TB, it's 23 TB lower than the top of the
|
|
|
|
|
64-bit address space (ffffffffffffffff).
|
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|
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|
|
Note that as we get closer to the top of the address space, the notation changes
|
|
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|
|
from TB to GB and then MB/KB.
|
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- "16M TB" might look weird at first sight, but it's an easier to visualize size
|
|
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|
|
notation than "16 EB", which few will recognize at first sight as 16 exabytes.
|
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|
It also shows it nicely how incredibly large 64-bit address space is.
|
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|
|
|
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|
========================================================================================================================
|
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|
Start addr | Offset | End addr | Size | VM area description
|
|
|
|
|
========================================================================================================================
|
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|
| | | |
|
|
|
|
|
0000000000000000 | 0 | 00007fffffffffff | 128 TB | user-space virtual memory, different per mm
|
|
|
|
|
__________________|____________|__________________|_________|___________________________________________________________
|
|
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|
| | | |
|
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|
0000800000000000 | +128 TB | ffff7fffffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical
|
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|
| | | | virtual memory addresses up to the -128 TB
|
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|
| | | | starting offset of kernel mappings.
|
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|
__________________|____________|__________________|_________|___________________________________________________________
|
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|
|
| Kernel-space virtual memory, shared between all processes:
|
|
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|
|
____________________________________________________________|___________________________________________________________
|
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|
|
| | | |
|
|
|
|
|
ffff800000000000 | -128 TB | ffff87ffffffffff | 8 TB | ... guard hole, also reserved for hypervisor
|
|
|
|
|
ffff880000000000 | -120 TB | ffffc7ffffffffff | 64 TB | direct mapping of all physical memory (page_offset_base)
|
|
|
|
|
ffffc80000000000 | -56 TB | ffffc8ffffffffff | 1 TB | ... unused hole
|
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|
ffffc90000000000 | -55 TB | ffffe8ffffffffff | 32 TB | vmalloc/ioremap space (vmalloc_base)
|
|
|
|
|
ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unused hole
|
|
|
|
|
ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual memory map (vmemmap_base)
|
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|
|
ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unused hole
|
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|
ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory
|
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|
|
fffffc0000000000 | -4 TB | fffffdffffffffff | 2 TB | ... unused hole
|
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|
|
| | | | vaddr_end for KASLR
|
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fffffe0000000000 | -2 TB | fffffe7fffffffff | 0.5 TB | cpu_entry_area mapping
|
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|
fffffe8000000000 | -1.5 TB | fffffeffffffffff | 0.5 TB | LDT remap for PTI
|
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|
ffffff0000000000 | -1 TB | ffffff7fffffffff | 0.5 TB | %esp fixup stacks
|
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__________________|____________|__________________|_________|____________________________________________________________
|
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|
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| Identical layout to the 47-bit one from here on:
|
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|
____________________________________________________________|____________________________________________________________
|
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| | | |
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ffffff8000000000 | -512 GB | ffffffeeffffffff | 444 GB | ... unused hole
|
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|
ffffffef00000000 | -68 GB | fffffffeffffffff | 64 GB | EFI region mapping space
|
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|
ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | ... unused hole
|
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ffffffff80000000 | -2 GB | ffffffff9fffffff | 512 MB | kernel text mapping, mapped to physical address 0
|
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ffffffff80000000 |-2048 MB | | |
|
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ffffffffa0000000 |-1536 MB | fffffffffeffffff | 1520 MB | module mapping space
|
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ffffffffff000000 | -16 MB | | |
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FIXADDR_START | ~-11 MB | ffffffffff5fffff | ~0.5 MB | kernel-internal fixmap range, variable size and offset
|
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ffffffffff600000 | -10 MB | ffffffffff600fff | 4 kB | legacy vsyscall ABI
|
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|
ffffffffffe00000 | -2 MB | ffffffffffffffff | 2 MB | ... unused hole
|
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|
__________________|____________|__________________|_________|___________________________________________________________
|
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|
|
|
|
|
|
|
|
|
|
|
|
====================================================
|
|
|
|
|
Complete virtual memory map with 5-level page tables
|
|
|
|
|
====================================================
|
|
|
|
|
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|
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Notes:
|
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|
- With 56-bit addresses, user-space memory gets expanded by a factor of 512x,
|
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from 0.125 PB to 64 PB. All kernel mappings shift down to the -64 PT starting
|
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offset and many of the regions expand to support the much larger physical
|
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memory supported.
|
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|
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|
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|
========================================================================================================================
|
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|
Start addr | Offset | End addr | Size | VM area description
|
|
|
|
|
========================================================================================================================
|
|
|
|
|
| | | |
|
|
|
|
|
0000000000000000 | 0 | 00ffffffffffffff | 64 PB | user-space virtual memory, different per mm
|
|
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|
|
__________________|____________|__________________|_________|___________________________________________________________
|
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|
| | | |
|
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|
0000800000000000 | +64 PB | ffff7fffffffffff | ~16K PB | ... huge, still almost 64 bits wide hole of non-canonical
|
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|
| | | | virtual memory addresses up to the -128 TB
|
|
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|
|
| | | | starting offset of kernel mappings.
|
|
|
|
|
__________________|____________|__________________|_________|___________________________________________________________
|
|
|
|
|
|
|
|
|
|
|
| Kernel-space virtual memory, shared between all processes:
|
|
|
|
|
____________________________________________________________|___________________________________________________________
|
|
|
|
|
| | | |
|
|
|
|
|
ff00000000000000 | -64 PB | ff0fffffffffffff | 4 PB | ... guard hole, also reserved for hypervisor
|
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|
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|
ff10000000000000 | -60 PB | ff8fffffffffffff | 32 PB | direct mapping of all physical memory (page_offset_base)
|
|
|
|
|
ff90000000000000 | -28 PB | ff9fffffffffffff | 4 PB | LDT remap for PTI
|
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ffa0000000000000 | -24 PB | ffd1ffffffffffff | 12.5 PB | vmalloc/ioremap space (vmalloc_base)
|
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ffd2000000000000 | -11.5 PB | ffd3ffffffffffff | 0.5 PB | ... unused hole
|
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ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual memory map (vmemmap_base)
|
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ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unused hole
|
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ffdf000000000000 | -8.25 PB | fffffdffffffffff | ~8 PB | KASAN shadow memory
|
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fffffc0000000000 | -4 TB | fffffdffffffffff | 2 TB | ... unused hole
|
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| | | | vaddr_end for KASLR
|
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fffffe0000000000 | -2 TB | fffffe7fffffffff | 0.5 TB | cpu_entry_area mapping
|
|
|
|
|
fffffe8000000000 | -1.5 TB | fffffeffffffffff | 0.5 TB | ... unused hole
|
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|
|
ffffff0000000000 | -1 TB | ffffff7fffffffff | 0.5 TB | %esp fixup stacks
|
|
|
|
|
__________________|____________|__________________|_________|____________________________________________________________
|
|
|
|
|
|
|
|
|
|
|
| Identical layout to the 47-bit one from here on:
|
|
|
|
|
____________________________________________________________|____________________________________________________________
|
|
|
|
|
| | | |
|
|
|
|
|
ffffff8000000000 | -512 GB | ffffffeeffffffff | 444 GB | ... unused hole
|
|
|
|
|
ffffffef00000000 | -68 GB | fffffffeffffffff | 64 GB | EFI region mapping space
|
|
|
|
|
ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | ... unused hole
|
|
|
|
|
ffffffff80000000 | -2 GB | ffffffff9fffffff | 512 MB | kernel text mapping, mapped to physical address 0
|
|
|
|
|
ffffffff80000000 |-2048 MB | | |
|
|
|
|
|
ffffffffa0000000 |-1536 MB | fffffffffeffffff | 1520 MB | module mapping space
|
|
|
|
|
ffffffffff000000 | -16 MB | | |
|
|
|
|
|
FIXADDR_START | ~-11 MB | ffffffffff5fffff | ~0.5 MB | kernel-internal fixmap range, variable size and offset
|
|
|
|
|
ffffffffff600000 | -10 MB | ffffffffff600fff | 4 kB | legacy vsyscall ABI
|
|
|
|
|
ffffffffffe00000 | -2 MB | ffffffffffffffff | 2 MB | ... unused hole
|
|
|
|
|
__________________|____________|__________________|_________|___________________________________________________________
|
2017-03-30 16:07:27 +08:00
|
|
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|
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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
|
2017-12-05 20:34:54 +08:00
|
|
|
through to the most-significant implemented bit are sign extended.
|
|
|
|
|
This causes hole between user space and kernel addresses if you interpret them
|
|
|
|
|
as unsigned.
|
2017-03-30 16:07:27 +08:00
|
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|
|
2007-02-13 20:26:23 +08:00
|
|
|
The direct mapping covers all memory in the system up to the highest
|
2005-11-06 00:25:54 +08:00
|
|
|
memory address (this means in some cases it can also include PCI memory
|
2007-02-13 20:26:23 +08:00
|
|
|
holes).
|
2005-11-06 00:25:54 +08:00
|
|
|
|
2017-03-30 16:07:27 +08:00
|
|
|
vmalloc space is lazily synchronized into the different PML4/PML5 pages of
|
|
|
|
|
the processes using the page fault handler, with init_top_pgt as
|
2005-04-17 06:20:36 +08:00
|
|
|
reference.
|
|
|
|
|
|
2015-11-28 05:09:35 +08:00
|
|
|
We map EFI runtime services in the 'efi_pgd' PGD in a 64Gb large virtual
|
|
|
|
|
memory window (this size is arbitrary, it can be raised later if needed).
|
|
|
|
|
The mappings are not part of any other kernel PGD and are only available
|
|
|
|
|
during EFI runtime calls.
|
2013-11-01 00:25:08 +08:00
|
|
|
|
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
|
|
|
Note that if CONFIG_RANDOMIZE_MEMORY is enabled, the direct mapping of all
|
|
|
|
|
physical memory, vmalloc/ioremap space and virtual memory map are randomized.
|
|
|
|
|
Their order is preserved but their base will be offset early at boot time.
|
2018-01-04 19:32:03 +08:00
|
|
|
|
|
|
|
|
Be very careful vs. KASLR when changing anything here. The KASLR address
|
|
|
|
|
range must not overlap with anything except the KASAN shadow area, which is
|
|
|
|
|
correct as KASAN disables KASLR.
|