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Message-ID: <2hhihkaeeyyy3xj22mjdx44zlied2sp4mfewj7y6ffrnakw7cy@3fuds6n7f4ew>
Date: Tue, 18 Jun 2024 09:43:37 -0500
From: Maxwell Bland <mbland@...orola.com>
To: linux-mm@...ck.org
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>,
Ard Biesheuvel <ardb@...nel.org>, Mark Rutland <mark.rutland@....com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Maxwell Bland <mbland@...orola.com>,
Alexandre Ghiti <alexghiti@...osinc.com>,
linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v4 5/5] arm64: add attrs and format to ptdump document
Update the ptdump content with a precise explanation of the attribute
symbols and the identical-entry coalescing implicit in the code.
Remove unnecessary layout example given the existing cat example,
and opt instead for a precise, clear explantination of address markers,
format, attributes.
Update example to match the new cosmetic and intermediate-directory
printing changes.
Signed-off-by: Maxwell Bland <mbland@...orola.com>
---
Documentation/arch/arm64/ptdump.rst | 126 ++++++++++++++--------------
1 file changed, 61 insertions(+), 65 deletions(-)
diff --git a/Documentation/arch/arm64/ptdump.rst b/Documentation/arch/arm64/ptdump.rst
index 5dcfc5d7cddf..fee7600dd4d1 100644
--- a/Documentation/arch/arm64/ptdump.rst
+++ b/Documentation/arch/arm64/ptdump.rst
@@ -29,68 +29,64 @@ configurations and mount debugfs::
mount -t debugfs nodev /sys/kernel/debug
cat /sys/kernel/debug/kernel_page_tables
-On analysing the output of ``cat /sys/kernel/debug/kernel_page_tables``
-one can derive information about the virtual address range of the entry,
-followed by size of the memory region covered by this entry, the
-hierarchical structure of the page tables and finally the attributes
-associated with each page. The page attributes provide information about
-access permissions, execution capability, type of mapping such as leaf
-level PTE or block level PGD, PMD and PUD, and access status of a page
-within the kernel memory. Assessing these attributes can assist in
-understanding the memory layout, access patterns and security
-characteristics of the kernel pages.
-
-Kernel virtual memory layout example::
-
- start address end address size attributes
- +---------------------------------------------------------------------------------------+
- | ---[ Linear Mapping start ]---------------------------------------------------------- |
- | .................. |
- | 0xfff0000000000000-0xfff0000000210000 2112K PTE RW NX SHD AF UXN MEM/NORMAL-TAGGED |
- | 0xfff0000000210000-0xfff0000001c00000 26560K PTE ro NX SHD AF UXN MEM/NORMAL |
- | .................. |
- | ---[ Linear Mapping end ]------------------------------------------------------------ |
- +---------------------------------------------------------------------------------------+
- | ---[ Modules start ]----------------------------------------------------------------- |
- | .................. |
- | 0xffff800000000000-0xffff800008000000 128M PTE |
- | .................. |
- | ---[ Modules end ]------------------------------------------------------------------- |
- +---------------------------------------------------------------------------------------+
- | ---[ vmalloc() area ]---------------------------------------------------------------- |
- | .................. |
- | 0xffff800008010000-0xffff800008200000 1984K PTE ro x SHD AF UXN MEM/NORMAL |
- | 0xffff800008200000-0xffff800008e00000 12M PTE ro x SHD AF CON UXN MEM/NORMAL |
- | .................. |
- | ---[ vmalloc() end ]----------------------------------------------------------------- |
- +---------------------------------------------------------------------------------------+
- | ---[ Fixmap start ]------------------------------------------------------------------ |
- | .................. |
- | 0xfffffbfffdb80000-0xfffffbfffdb90000 64K PTE ro x SHD AF UXN MEM/NORMAL |
- | 0xfffffbfffdb90000-0xfffffbfffdba0000 64K PTE ro NX SHD AF UXN MEM/NORMAL |
- | .................. |
- | ---[ Fixmap end ]-------------------------------------------------------------------- |
- +---------------------------------------------------------------------------------------+
- | ---[ PCI I/O start ]----------------------------------------------------------------- |
- | .................. |
- | 0xfffffbfffe800000-0xfffffbffff800000 16M PTE |
- | .................. |
- | ---[ PCI I/O end ]------------------------------------------------------------------- |
- +---------------------------------------------------------------------------------------+
- | ---[ vmemmap start ]----------------------------------------------------------------- |
- | .................. |
- | 0xfffffc0002000000-0xfffffc0002200000 2M PTE RW NX SHD AF UXN MEM/NORMAL |
- | 0xfffffc0002200000-0xfffffc0020000000 478M PTE |
- | .................. |
- | ---[ vmemmap end ]------------------------------------------------------------------- |
- +---------------------------------------------------------------------------------------+
-
-``cat /sys/kernel/debug/kernel_page_tables`` output::
-
- 0xfff0000001c00000-0xfff0000080000000 2020M PTE RW NX SHD AF UXN MEM/NORMAL-TAGGED
- 0xfff0000080000000-0xfff0000800000000 30G PMD
- 0xfff0000800000000-0xfff0000800700000 7M PTE RW NX SHD AF UXN MEM/NORMAL-TAGGED
- 0xfff0000800700000-0xfff0000800710000 64K PTE ro NX SHD AF UXN MEM/NORMAL-TAGGED
- 0xfff0000800710000-0xfff0000880000000 2089920K PTE RW NX SHD AF UXN MEM/NORMAL-TAGGED
- 0xfff0000880000000-0xfff0040000000000 4062G PMD
- 0xfff0040000000000-0xffff800000000000 3964T PGD
+``/sys/kernel/debug/kernel_page_tables`` provides a line of information
+for each group of page table entries sharing the same attributes and
+type of mapping, i.e. leaf level PTE or block level PGD, PMD, and PUD.
+Assessing these attributes can assist in determining memory layout,
+access patterns and security characteristics of the kernel pages.
+
+Lines are formatted as follows::
+
+ <start_vaddr>-<end_vaddr> <size> <type> <attributes>
+
+Note that the set of attributes, and therefore formatting, is not
+equivalent between leaf and non-leaf entries. For example, PMD entries
+can support the PXNTable permission bit and do not share that same set
+of attributes as leaf level PTE entries.
+
+The following attributes are presently supported::
+
+F Entry is invalid
+USER Memory is user mapped
+ro Memory is read-only
+RW Memory is read-write
+NX Memory is privileged execute never
+x Memory is privileged executable
+SHD Memory is shared
+AF Entry accessed flag is set
+NG Entry Not-Global flag is set
+CON Entry contiguous bit is set
+UXN Memory is unprivileged execute never
+GP Memory supports BTI
+TBL Entry is a table descriptor
+BLK Entry is a block descriptor
+NXTbl Entry's referenced table is PXN
+UXNTbl Entry's referenced table is unprivileged execute never
+DEVICE/* Entry is device memory, see ARM reference for types
+MEM/* Entry is non-device memory, see ARM reference for types
+
+The beginning and end of each region is also delineated by a single line
+tag in the following format::
+
+ ---[ <marker_name> ]---
+
+With supported address markers including the kernel's linear mapping,
+kasan shadow memory, kernel modules memory, vmalloc memory, PCI I/O
+memory, and the kernel's fixmap region.
+
+Example ``cat /sys/kernel/debug/kernel_page_tables`` output::
+
+---[ Linear Mapping start ]---
+0xffff000000000000-0xffff31ffffffffff 50T PGD
+0xffff320000000000-0xffffffffffffffff 206T PGD TBL RW x NXTbl UXNTbl MEM/NORMAL
+ 0xffff320000000000-0xffff3251ffffffff 328G PUD
+ 0xffff325200000000-0xffff32523fffffff 1G PUD TBL RW x NXTbl UXNTbl MEM/NORMAL
+ 0xffff325200000000-0xffff3252001fffff 2M PMD TBL RW x NXTbl UXNTbl MEM/NORMAL
+ 0xffff325200000000-0xffff3252001fffff 2M PTE RW NX SHD AF NG UXN MEM/NORMAL-TAGGED
+ 0xffff325200200000-0xffff3252003fffff 2M PMD TBL RW x NXTbl UXNTbl MEM/NORMAL
+ 0xffff325200200000-0xffff32520020ffff 64K PTE RW NX SHD AF NG UXN MEM/NORMAL-TAGGED
+ 0xffff325200210000-0xffff3252003fffff 1984K PTE ro NX SHD AF NG UXN MEM/NORMAL
+ 0xffff325200400000-0xffff325201dfffff 26M PMD BLK ro SHD AF NG NX UXN MEM/NORMAL
+ 0xffff325201e00000-0xffff325201ffffff 2M PMD TBL RW x NXTbl UXNTbl MEM/NORMAL
+ 0xffff325201e00000-0xffff325201e0ffff 64K PTE ro NX SHD AF NG UXN MEM/NORMAL
+ 0xffff325201e10000-0xffff325201ffffff 1984K PTE RW NX SHD AF NG UXN MEM/NORMAL-TAGGED
--
2.39.2
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