aecfd220b2
Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings (e.g.
"unused variable"). If the compiler thinks it is uninitialized, either
simply initialize the variable or make compiler changes. As a precursor
to removing[2] this[3] macro[4], refactor code to avoid its need.
The original reason for its use here was to work around the #ifdef
being the only place the variable was used. This is better expressed
using IS_ENABLED() and a new code block where the variable can be used
unconditionally.
[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/
Fixes: 1e01979c8f ("x86, numa: Implement pfn -> nid mapping granularity check")
Signed-off-by: Kees Cook <keescook@chromium.org>
114 lines
3.4 KiB
C
114 lines
3.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef PAGE_FLAGS_LAYOUT_H
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#define PAGE_FLAGS_LAYOUT_H
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#include <linux/numa.h>
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#include <generated/bounds.h>
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/*
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* When a memory allocation must conform to specific limitations (such
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* as being suitable for DMA) the caller will pass in hints to the
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* allocator in the gfp_mask, in the zone modifier bits. These bits
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* are used to select a priority ordered list of memory zones which
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* match the requested limits. See gfp_zone() in include/linux/gfp.h
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*/
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#if MAX_NR_ZONES < 2
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#define ZONES_SHIFT 0
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#elif MAX_NR_ZONES <= 2
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#define ZONES_SHIFT 1
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#elif MAX_NR_ZONES <= 4
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#define ZONES_SHIFT 2
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#elif MAX_NR_ZONES <= 8
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#define ZONES_SHIFT 3
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#else
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#error ZONES_SHIFT -- too many zones configured adjust calculation
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#endif
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#ifdef CONFIG_SPARSEMEM
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#include <asm/sparsemem.h>
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/* SECTION_SHIFT #bits space required to store a section # */
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#define SECTIONS_SHIFT (MAX_PHYSMEM_BITS - SECTION_SIZE_BITS)
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#endif /* CONFIG_SPARSEMEM */
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#ifndef BUILD_VDSO32_64
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/*
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* page->flags layout:
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*
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* There are five possibilities for how page->flags get laid out. The first
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* pair is for the normal case without sparsemem. The second pair is for
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* sparsemem when there is plenty of space for node and section information.
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* The last is when there is insufficient space in page->flags and a separate
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* lookup is necessary.
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*
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* No sparsemem or sparsemem vmemmap: | NODE | ZONE | ... | FLAGS |
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* " plus space for last_cpupid: | NODE | ZONE | LAST_CPUPID ... | FLAGS |
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* classic sparse with space for node:| SECTION | NODE | ZONE | ... | FLAGS |
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* " plus space for last_cpupid: | SECTION | NODE | ZONE | LAST_CPUPID ... | FLAGS |
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* classic sparse no space for node: | SECTION | ZONE | ... | FLAGS |
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*/
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#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
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#define SECTIONS_WIDTH SECTIONS_SHIFT
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#else
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#define SECTIONS_WIDTH 0
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#endif
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#define ZONES_WIDTH ZONES_SHIFT
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#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT <= BITS_PER_LONG - NR_PAGEFLAGS
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#define NODES_WIDTH NODES_SHIFT
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#else
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#ifdef CONFIG_SPARSEMEM_VMEMMAP
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#error "Vmemmap: No space for nodes field in page flags"
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#endif
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#define NODES_WIDTH 0
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#endif
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#ifdef CONFIG_NUMA_BALANCING
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#define LAST__PID_SHIFT 8
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#define LAST__PID_MASK ((1 << LAST__PID_SHIFT)-1)
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#define LAST__CPU_SHIFT NR_CPUS_BITS
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#define LAST__CPU_MASK ((1 << LAST__CPU_SHIFT)-1)
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#define LAST_CPUPID_SHIFT (LAST__PID_SHIFT+LAST__CPU_SHIFT)
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#else
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#define LAST_CPUPID_SHIFT 0
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#endif
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#ifdef CONFIG_KASAN_SW_TAGS
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#define KASAN_TAG_WIDTH 8
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#else
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#define KASAN_TAG_WIDTH 0
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#endif
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#if SECTIONS_WIDTH+ZONES_WIDTH+NODES_SHIFT+LAST_CPUPID_SHIFT+KASAN_TAG_WIDTH \
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<= BITS_PER_LONG - NR_PAGEFLAGS
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#define LAST_CPUPID_WIDTH LAST_CPUPID_SHIFT
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#else
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#define LAST_CPUPID_WIDTH 0
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#endif
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#if SECTIONS_WIDTH+NODES_WIDTH+ZONES_WIDTH+LAST_CPUPID_WIDTH+KASAN_TAG_WIDTH \
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> BITS_PER_LONG - NR_PAGEFLAGS
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#error "Not enough bits in page flags"
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#endif
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/*
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* We are going to use the flags for the page to node mapping if its in
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* there. This includes the case where there is no node, so it is implicit.
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* Note that this #define MUST have a value so that it can be tested with
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* the IS_ENABLED() macro.
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*/
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#if !(NODES_WIDTH > 0 || NODES_SHIFT == 0)
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#define NODE_NOT_IN_PAGE_FLAGS 1
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#endif
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#if defined(CONFIG_NUMA_BALANCING) && LAST_CPUPID_WIDTH == 0
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#define LAST_CPUPID_NOT_IN_PAGE_FLAGS
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#endif
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#endif
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#endif /* _LINUX_PAGE_FLAGS_LAYOUT */
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