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d52888aa27
On 5-level paging the LDT remap area is placed in the middle of the KASLR
randomization region and it can overlap with the direct mapping, the
vmalloc or the vmap area.
The LDT mapping is per mm, so it cannot be moved into the P4D page table
next to the CPU_ENTRY_AREA without complicating PGD table allocation for
5-level paging.
The 4 PGD slot gap just before the direct mapping is reserved for
hypervisors, so it cannot be used.
Move the direct mapping one slot deeper and use the resulting gap for the
LDT remap area. The resulting layout is the same for 4 and 5 level paging.
[ tglx: Massaged changelog ]
Fixes: f55f0501cb ("x86/pti: Put the LDT in its own PGD if PTI is on")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: bp@alien8.de
Cc: hpa@zytor.com
Cc: dave.hansen@linux.intel.com
Cc: peterz@infradead.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: bhe@redhat.com
Cc: willy@infradead.org
Cc: linux-mm@kvack.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181026122856.66224-2-kirill.shutemov@linux.intel.com
154 lines
11 KiB
Plaintext
154 lines
11 KiB
Plaintext
====================================================
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Complete virtual memory map with 4-level page tables
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====================================================
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Notes:
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- Negative addresses such as "-23 TB" are absolute addresses in bytes, counted down
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from the top of the 64-bit address space. It's easier to understand the layout
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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
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64-bit address space (ffffffffffffffff).
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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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Start addr | Offset | End addr | Size | VM area description
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========================================================================================================================
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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
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ffff880000000000 | -120 TB | ffff887fffffffff | 0.5 TB | LDT remap for PTI
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ffff888000000000 | -119.5 TB | ffffc87fffffffff | 64 TB | direct mapping of all physical memory (page_offset_base)
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ffffc88000000000 | -55.5 TB | ffffc8ffffffffff | 0.5 TB | ... unused hole
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ffffc90000000000 | -55 TB | ffffe8ffffffffff | 32 TB | vmalloc/ioremap space (vmalloc_base)
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ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unused hole
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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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__________________|____________|__________________|_________|____________________________________________________________
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| Identical layout to the 56-bit one from here on:
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____________________________________________________________|____________________________________________________________
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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 | ... unused hole
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ffffff0000000000 | -1 TB | ffffff7fffffffff | 0.5 TB | %esp fixup stacks
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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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====================================================
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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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Start addr | Offset | End addr | Size | VM area description
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========================================================================================================================
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0000000000000000 | 0 | 00ffffffffffffff | 64 PB | user-space virtual memory, different per mm
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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 -64 PB
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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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ff00000000000000 | -64 PB | ff0fffffffffffff | 4 PB | ... guard hole, also reserved for hypervisor
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ff10000000000000 | -60 PB | ff10ffffffffffff | 0.25 PB | LDT remap for PTI
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ff11000000000000 | -59.75 PB | ff90ffffffffffff | 32 PB | direct mapping of all physical memory (page_offset_base)
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ff91000000000000 | -27.75 PB | ff9fffffffffffff | 3.75 PB | ... unused hole
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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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__________________|____________|__________________|_________|____________________________________________________________
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| Identical layout to the 47-bit one from here on:
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____________________________________________________________|____________________________________________________________
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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 | ... unused hole
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ffffff0000000000 | -1 TB | ffffff7fffffffff | 0.5 TB | %esp fixup stacks
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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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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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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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The direct mapping covers all memory in the system up to the highest
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memory address (this means in some cases it can also include PCI memory
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holes).
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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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reference.
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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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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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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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For both 4- and 5-level layouts, the STACKLEAK_POISON value in the last 2MB
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hole: ffffffffffff4111
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