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From: Felix Fietkau <nbd@openwrt.org>
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@openwrt.org>
---
--- 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);
@@ -142,7 +161,12 @@ 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))
+ return;
+
+ if (PageHighMem(page)) {
+ flush_highmem_page(page);
+ } else if (page_mapping(page)) {
addr = (unsigned long) page_address(page);
if (exec || pages_do_alias(addr, address & PAGE_MASK))
flush_data_cache_page(addr);
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