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0d453ba040
Define CONFIG_ILLEGAL_POINTER_VALUE to the eye-catching non-zero value of 0xdead000000000000, consistent with other architectures. Assert at compile-time that the poison pointers that include/linux/poison.h defines based on this illegal pointer are beyond the largest useful virtual addresses. Also, assert at compile-time that the range of poison pointers per include/linux/poison.h (currently a range of less than 0x10000 addresses) does not overlap with the range used for address handles for s390's non-MIO PCI instructions. This enables s390 to track the DMA mappings by the network stack's page_pool that was introduced with [0]. Other functional changes are not intended. Other archictectures have introduced this for various other reasons with commit5c178472af("riscv: define ILLEGAL_POINTER_VALUE for 64bit") commitf6853eb561("powerpc/64: Define ILLEGAL_POINTER_VALUE for 64-bit") commitbf0c4e0473("arm64: kconfig: Move LIST_POISON to a safe value") commita29815a333("core, x86: make LIST_POISON less deadly") [0] https://lore.kernel.org/all/20250409-page-pool-track-dma-v9-0-6a9ef2e0cba8@redhat.com/ Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com> Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com> Acked-by: Alexander Gordeev <agordeev@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
116 lines
3.4 KiB
ReStructuredText
116 lines
3.4 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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=================
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Memory Management
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=================
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Virtual memory layout
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=====================
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.. note::
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- Some aspects of the virtual memory layout setup are not
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clarified (number of page levels, alignment, DMA memory).
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- Unused gaps in the virtual memory layout could be present
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or not - depending on how partucular system is configured.
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No page tables are created for the unused gaps.
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- The virtual memory regions are tracked or untracked by KASAN
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instrumentation, as well as the KASAN shadow memory itself is
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created only when CONFIG_KASAN configuration option is enabled.
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::
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=============================================================================
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| Physical | Virtual | VM area description
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=============================================================================
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+- 0 --------------+- 0 --------------+
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| | S390_lowcore | Low-address memory
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| +- 8 KB -----------+
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| | ... unused gap | KASAN untracked
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+- AMODE31_START --+- AMODE31_START --+ .amode31 rand. phys/virt start
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|.amode31 text/data|.amode31 text/data| KASAN untracked
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+- AMODE31_END ----+- AMODE31_END ----+ .amode31 rand. phys/virt end (<2GB)
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+- __kaslr_offset_phys | kernel rand. phys start
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| kernel text/data | |
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+------------------+ | kernel phys end
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+- ident_map_size -+ |
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| ... unused gap | KASAN untracked
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+- __identity_base + identity mapping start (>= 2GB)
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| identity | phys == virt - __identity_base
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| mapping | virt == phys + __identity_base
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| | KASAN tracked
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+---- vmemmap -----+ 'struct page' array start
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| virtually mapped |
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| memory map | KASAN untracked
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+- __abs_lowcore --+
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| Absolute Lowcore | KASAN untracked
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+- __memcpy_real_area
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| Real Memory Copy| KASAN untracked
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+- VMALLOC_START --+ vmalloc area start
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| | KASAN untracked or
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| vmalloc area | KASAN shallowly populated in case
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| | CONFIG_KASAN_VMALLOC=y
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+- MODULES_VADDR --+ modules area start
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| | KASAN allocated per module or
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| modules area | KASAN shallowly populated in case
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| | CONFIG_KASAN_VMALLOC=y
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+- __kaslr_offset -+ kernel rand. virt start
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| | KASAN tracked
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| kernel text/data | phys == (kvirt - __kaslr_offset) +
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| | __kaslr_offset_phys
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+- kernel .bss end + kernel rand. virt end
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| ... unused gap | KASAN untracked
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+------------------+ UltraVisor Secure Storage limit
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| ... unused gap | KASAN untracked
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+KASAN_SHADOW_START+ KASAN shadow memory start
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| KASAN shadow | KASAN untracked
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+------------------+ ASCE limit
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| CONFIG_ILLEGAL_POINTER_VALUE causes memory access fault
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+------------------+
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