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Lorenzo Stoakes
2b6a3f061f
Patch series "initial work on making VMA flags a bitmap", v3.
We are in the rather silly situation that we are running out of VMA flags
as they are currently limited to a system word in size.
This leads to absurd situations where we limit features to 64-bit
architectures only because we simply do not have the ability to add a flag
for 32-bit ones.
This is very constraining and leads to hacks or, in the worst case, simply
an inability to implement features we want for entirely arbitrary reasons.
This also of course gives us something of a Y2K type situation in mm where
we might eventually exhaust all of the VMA flags even on 64-bit systems.
This series lays the groundwork for getting away from this limitation by
establishing VMA flags as a bitmap whose size we can increase in future
beyond 64 bits if required.
This is necessarily a highly iterative process given the extensive use of
VMA flags throughout the kernel, so we start by performing basic steps.
Firstly, we declare VMA flags by bit number rather than by value,
retaining the VM_xxx fields but in terms of these newly introduced
VMA_xxx_BIT fields.
While we are here, we use sparse annotations to ensure that, when dealing
with VMA bit number parameters, we cannot be passed values which are not
declared as such - providing some useful type safety.
We then introduce an opaque VMA flag type, much like the opaque mm_struct
flag type introduced in commit bb6525f2f8 ("mm: add bitmap mm->flags
field"), which we establish in union with vma->vm_flags (but still set at
system word size meaning there is no functional or data type size change).
We update the vm_flags_xxx() helpers to use this new bitmap, introducing
sensible helpers to do so.
This series lays the foundation for further work to expand the use of
bitmap VMA flags and eventually eliminate these arbitrary restrictions.
This patch (of 4):
In order to lay the groundwork for VMA flags being a bitmap rather than a
system word in size, we need to be able to consistently refer to VMA flags
by bit number rather than value.
Take this opportunity to do so in an enum which we which is additionally
useful for tooling to extract metadata from.
This additionally makes it very clear which bits are being used for what
at a glance.
We use the VMA_ prefix for the bit values as it is logical to do so since
these reference VMAs. We consistently suffix with _BIT to make it clear
what the values refer to.
We declare bit values even when the flags that use them would not be
enabled by config options as this is simply clearer and clearly defines
what bit numbers are used for what, at no additional cost.
We declare a sparse-bitwise type vma_flag_t which ensures that users can't
pass around invalid VMA flags by accident and prepares for future work
towards VMA flags being a bitmap where we want to ensure bit values are
type safe.
To make life easier, we declare some macro helpers - DECLARE_VMA_BIT()
allows us to avoid duplication in the enum bit number declarations (and
maintaining the sparse __bitwise attribute), and INIT_VM_FLAG() is used to
assist with declaration of flags.
Unfortunately we can't declare both in the enum, as we run into issue with
logic in the kernel requiring that flags are preprocessor definitions, and
additionally we cannot have a macro which declares another macro so we
must define each flag macro directly.
Additionally, update the VMA userland testing vma_internal.h header to
include these changes.
We also have to fix the parameters to the vma_flag_*_atomic() functions
since VMA_MAYBE_GUARD_BIT is now of type vma_flag_t and sparse will
complain otherwise.
We have to update some rather silly if-deffery found in mm/task_mmu.c
which would otherwise break.
Finally, we update the rust binding helper as now it cannot auto-detect
the flags at all.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/3a35e5a0bcfa00e84af24cbafc0653e74deda64a.1764064556.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Reviewed-by: Pedro Falcato <[email protected]>
Acked-by: Alice Ryhl <[email protected]> [rust]
Cc: Alex Gaynor <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Andreas Hindborg <[email protected]>
Cc: Axel Rasmussen <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: Baoquan He <[email protected]>
Cc: Barry Song <[email protected]>
Cc: Ben Segall <[email protected]>
Cc: Björn Roy Baron <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Byungchul Park <[email protected]>
Cc: Chengming Zhou <[email protected]>
Cc: Chris Li <[email protected]>
Cc: Danilo Krummrich <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Dev Jain <[email protected]>
Cc: Dietmar Eggemann <[email protected]>
Cc: Gary Guo <[email protected]>
Cc: Gregory Price <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Joshua Hahn <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Kairui Song <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Kemeng Shi <[email protected]>
Cc: Lance Yang <[email protected]>
Cc: Leon Romanovsky <[email protected]>
Cc: Liam Howlett <[email protected]>
Cc: Mathew Brost <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Mel Gorman <mgorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Nhat Pham <[email protected]>
Cc: Nico Pache <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Qi Zheng <[email protected]>
Cc: Rakie Kim <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Shakeel Butt <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Trevor Gross <[email protected]>
Cc: Valentin Schneider <[email protected]>
Cc: Vincent Guittot <[email protected]>
Cc: Wei Xu <[email protected]>
Cc: xu xin <[email protected]>
Cc: Yuanchu Xie <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
67 lines
2.2 KiB
Plaintext
67 lines
2.2 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0
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# We want to map these types to `isize`/`usize` manually, instead of
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# define them as `int`/`long` depending on platform bitwidth.
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--blocklist-type __kernel_s?size_t
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--blocklist-type __kernel_ptrdiff_t
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--opaque-type xregs_state
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--opaque-type desc_struct
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--opaque-type arch_lbr_state
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--opaque-type local_apic
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# Packed type cannot transitively contain a `#[repr(align)]` type.
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--opaque-type alt_instr
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--opaque-type x86_msi_data
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--opaque-type x86_msi_addr_lo
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# `try` is a reserved keyword since Rust 2018; solved in `bindgen` v0.59.2,
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# commit 2aed6b021680 ("context: Escape the try keyword properly").
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--opaque-type kunit_try_catch
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# If SMP is disabled, `arch_spinlock_t` is defined as a ZST which triggers a Rust
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# warning. We don't need to peek into it anyway.
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--opaque-type spinlock
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# `seccomp`'s comment gets understood as a doctest
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--no-doc-comments
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# These functions use the `__preserve_most` calling convention, which neither bindgen
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# nor Rust currently understand, and which Clang currently declares to be unstable.
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--blocklist-function __list_.*_report
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# These constants are sometimes not recognized by bindgen depending on config.
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# We use const helpers to aid bindgen, to avoid conflicts when constants are
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# recognized, block generation of the non-helper constants.
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--blocklist-item ARCH_SLAB_MINALIGN
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--blocklist-item ARCH_KMALLOC_MINALIGN
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--blocklist-item VM_MERGEABLE
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--blocklist-item VM_READ
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--blocklist-item VM_WRITE
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--blocklist-item VM_EXEC
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--blocklist-item VM_SHARED
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--blocklist-item VM_MAYREAD
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--blocklist-item VM_MAYWRITE
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--blocklist-item VM_MAYEXEC
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--blocklist-item VM_MAYEXEC
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--blocklist-item VM_PFNMAP
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--blocklist-item VM_IO
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--blocklist-item VM_DONTCOPY
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--blocklist-item VM_DONTEXPAND
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--blocklist-item VM_LOCKONFAULT
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--blocklist-item VM_ACCOUNT
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--blocklist-item VM_NORESERVE
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--blocklist-item VM_HUGETLB
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--blocklist-item VM_SYNC
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--blocklist-item VM_ARCH_1
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--blocklist-item VM_WIPEONFORK
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--blocklist-item VM_DONTDUMP
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--blocklist-item VM_SOFTDIRTY
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--blocklist-item VM_MIXEDMAP
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--blocklist-item VM_HUGEPAGE
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--blocklist-item VM_NOHUGEPAGE
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# Structs should implement `Zeroable` when all of their fields do.
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--with-derive-custom-struct .*=MaybeZeroable
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--with-derive-custom-union .*=MaybeZeroable
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