treewide: fix replace nbd@openwrt.org with nbd@nbd.name
[openwrt.org/openwrt.git] / target / linux / generic / patches-4.4 / 101-MIPS-fix-cache-flushing-for-highmem-pages.patch
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From: Felix Fietkau <nbd@nbd.name>
Date: Sun, 24 Jan 2016 01:03:51 +0100
Subject: [PATCH] MIPS: fix cache flushing for highmem pages
 
Most cache flush ops were no-op for highmem pages. This led to nasty
segfaults and (in the case of page_address(page) == NULL) kernel
crashes.
 
Fix this by always flushing highmem pages using kmap/kunmap_atomic
around the actual cache flush. This might be a bit inefficient, but at
least it's stable.
 
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 
--- a/arch/mips/mm/cache.c
+++ b/arch/mips/mm/cache.c
@@ -14,6 +14,7 @@
 #include <linux/sched.h>
 #include <linux/syscalls.h>
 #include <linux/mm.h>
+#include <linux/highmem.h>
 
 #include <asm/cacheflush.h>
 #include <asm/processor.h>
@@ -78,18 +79,29 @@ SYSCALL_DEFINE3(cacheflush, unsigned lon
        return 0;
 }
 
+static void
+flush_highmem_page(struct page *page)
+{
+       void *addr = kmap_atomic(page);
+       flush_data_cache_page((unsigned long)addr);
+       kunmap_atomic(addr);
+}
+
 void __flush_dcache_page(struct page *page)
 {
        struct address_space *mapping = page_mapping(page);
        unsigned long addr;
 
-       if (PageHighMem(page))
-               return;
        if (mapping && !mapping_mapped(mapping)) {
                SetPageDcacheDirty(page);
                return;
        }
 
+       if (PageHighMem(page)) {
+               flush_highmem_page(page);
+               return;
+       }
+
        /*
         * We could delay the flush for the !page_mapping case too.  But that
         * case is for exec env/arg pages and those are %99 certainly going to
@@ -105,6 +117,11 @@ void __flush_anon_page(struct page *page
 {
        unsigned long addr = (unsigned long) page_address(page);
 
+       if (PageHighMem(page)) {
+               flush_highmem_page(page);
+               return;
+       }
+
        if (pages_do_alias(addr, vmaddr)) {
                if (page_mapped(page) && !Page_dcache_dirty(page)) {
                        void *kaddr;
@@ -123,8 +140,10 @@ void __flush_icache_page(struct vm_area_
 {
        unsigned long addr;
 
-       if (PageHighMem(page))
+       if (PageHighMem(page)) {
+               flush_highmem_page(page);
                return;
+       }
 
        addr = (unsigned long) page_address(page);
        flush_data_cache_page(addr);
@@ -142,12 +161,17 @@ void __update_cache(struct vm_area_struc
        if (unlikely(!pfn_valid(pfn)))
                return;
        page = pfn_to_page(pfn);
-       if (page_mapping(page) && Page_dcache_dirty(page)) {
+       if (!Page_dcache_dirty(page) || !page_mapping(page))
+               return;
+
+       if (PageHighMem(page)) {
+               flush_highmem_page(page);
+       } else {
                addr = (unsigned long) page_address(page);
                if (exec || pages_do_alias(addr, address & PAGE_MASK))
                        flush_data_cache_page(addr);
-               ClearPageDcacheDirty(page);
        }
+       ClearPageDcacheDirty(page);
 }
 
 unsigned long _page_cachable_default;
 
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