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-rw-r--r--lib/Kconfig.debug14
-rw-r--r--mm/highmem.c12
2 files changed, 25 insertions, 1 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index f24fa158f9db..e952f892f047 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -856,9 +856,23 @@ config DEBUG_KMAP_LOCAL
This option enables additional error checking for the kmap_local
infrastructure. Disable for production use.
+config ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP
+ bool
+
+config DEBUG_KMAP_LOCAL_FORCE_MAP
+ bool "Enforce kmap_local temporary mappings"
+ depends on DEBUG_KERNEL && ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP
+ select KMAP_LOCAL
+ select DEBUG_KMAP_LOCAL
+ help
+ This option enforces temporary mappings through the kmap_local
+ mechanism for non-highmem pages and on non-highmem systems.
+ Disable this for production systems!
+
config DEBUG_HIGHMEM
bool "Highmem debugging"
depends on DEBUG_KERNEL && HIGHMEM
+ select DEBUG_KMAP_LOCAL_FORCE_MAP if ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP
select DEBUG_KMAP_LOCAL
help
This option enables additional error checking for high memory
diff --git a/mm/highmem.c b/mm/highmem.c
index fab128de97de..39aaca1a1ece 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -474,7 +474,12 @@ void *__kmap_local_page_prot(struct page *page, pgprot_t prot)
{
void *kmap;
- if (!PageHighMem(page))
+ /*
+ * To broaden the usage of the actual kmap_local() machinery always map
+ * pages when debugging is enabled and the architecture has no problems
+ * with alias mappings.
+ */
+ if (!IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) && !PageHighMem(page))
return page_address(page);
/* Try kmap_high_get() if architecture has it enabled */
@@ -494,6 +499,11 @@ void kunmap_local_indexed(void *vaddr)
if (addr < __fix_to_virt(FIX_KMAP_END) ||
addr > __fix_to_virt(FIX_KMAP_BEGIN)) {
+ if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP)) {
+ /* This _should_ never happen! See above. */
+ WARN_ON_ONCE(1);
+ return;
+ }
/*
* Handle mappings which were obtained by kmap_high_get()
* first as the virtual address of such mappings is below