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cb9f753a37
Thanks to commit 4b3ef9daa4 ("mm/swap: split swap cache into 64MB
trunks"), after swapoff the address_space associated with the swap
device will be freed. So page_mapping() users which may touch the
address_space need some kind of mechanism to prevent the address_space
from being freed during accessing.
The dcache flushing functions (flush_dcache_page(), etc) in architecture
specific code may access the address_space of swap device for anonymous
pages in swap cache via page_mapping() function. But in some cases
there are no mechanisms to prevent the swap device from being swapoff,
for example,
CPU1 CPU2
__get_user_pages() swapoff()
flush_dcache_page()
mapping = page_mapping()
... exit_swap_address_space()
... kvfree(spaces)
mapping_mapped(mapping)
The address space may be accessed after being freed.
But from cachetlb.txt and Russell King, flush_dcache_page() only care
about file cache pages, for anonymous pages, flush_anon_page() should be
used. The implementation of flush_dcache_page() in all architectures
follows this too. They will check whether page_mapping() is NULL and
whether mapping_mapped() is true to determine whether to flush the
dcache immediately. And they will use interval tree (mapping->i_mmap)
to find all user space mappings. While mapping_mapped() and
mapping->i_mmap isn't used by anonymous pages in swap cache at all.
So, to fix the race between swapoff and flush dcache, __page_mapping()
is add to return the address_space for file cache pages and NULL
otherwise. All page_mapping() invoking in flush dcache functions are
replaced with page_mapping_file().
[akpm@linux-foundation.org: simplify page_mapping_file(), per Mike]
Link: http://lkml.kernel.org/r/20180305083634.15174-1-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Chen Liqin <liqin.linux@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Chris Zankel <chris@zankel.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
98 lines
2.4 KiB
C
98 lines
2.4 KiB
C
/*
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* linux/arch/unicore32/mm/flush.c
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*
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* Code specific to PKUnity SoC and UniCore ISA
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*
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* Copyright (C) 2001-2010 GUAN Xue-tao
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/module.h>
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#include <linux/mm.h>
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#include <linux/pagemap.h>
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#include <asm/cacheflush.h>
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#include <asm/tlbflush.h>
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void flush_cache_mm(struct mm_struct *mm)
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{
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}
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void flush_cache_range(struct vm_area_struct *vma, unsigned long start,
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unsigned long end)
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{
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if (vma->vm_flags & VM_EXEC)
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__flush_icache_all();
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}
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void flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr,
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unsigned long pfn)
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{
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}
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static void flush_ptrace_access(struct vm_area_struct *vma, struct page *page,
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unsigned long uaddr, void *kaddr, unsigned long len)
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{
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/* VIPT non-aliasing D-cache */
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if (vma->vm_flags & VM_EXEC) {
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unsigned long addr = (unsigned long)kaddr;
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__cpuc_coherent_kern_range(addr, addr + len);
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}
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}
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/*
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* Copy user data from/to a page which is mapped into a different
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* processes address space. Really, we want to allow our "user
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* space" model to handle this.
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*
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* Note that this code needs to run on the current CPU.
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*/
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void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
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unsigned long uaddr, void *dst, const void *src,
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unsigned long len)
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{
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memcpy(dst, src, len);
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flush_ptrace_access(vma, page, uaddr, dst, len);
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}
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void __flush_dcache_page(struct address_space *mapping, struct page *page)
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{
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/*
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* Writeback any data associated with the kernel mapping of this
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* page. This ensures that data in the physical page is mutually
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* coherent with the kernels mapping.
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*/
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__cpuc_flush_kern_dcache_area(page_address(page), PAGE_SIZE);
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}
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/*
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* Ensure cache coherency between kernel mapping and userspace mapping
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* of this page.
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*/
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void flush_dcache_page(struct page *page)
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{
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struct address_space *mapping;
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/*
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* The zero page is never written to, so never has any dirty
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* cache lines, and therefore never needs to be flushed.
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*/
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if (page == ZERO_PAGE(0))
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return;
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mapping = page_mapping_file(page);
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if (mapping && !mapping_mapped(mapping))
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clear_bit(PG_dcache_clean, &page->flags);
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else {
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__flush_dcache_page(mapping, page);
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if (mapping)
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__flush_icache_all();
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set_bit(PG_dcache_clean, &page->flags);
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}
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}
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EXPORT_SYMBOL(flush_dcache_page);
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