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mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL 

CONFIG_KMAP_LOCAL can be enabled by x86/32bit even if CONFIG_HIGHMEM is not
enabled for temporary MMIO space mappings.

Provide it as a seperate config option which depends on CONFIG_KMAP_LOCAL
and let CONFIG_DEBUG_HIGHMEM select it.

This won't increase the debug coverage of this significantly but it paves
the way to do so.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201118204006.869487226@linutronix.de
This commit is contained in:
Thomas Gleixner 2020-11-18 20:48:39 +01:00
parent 13c8da5db4
commit 6e799cb69a
3 changed files with 11 additions and 3 deletions
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2
include/asm-generic/kmap_size.h
View File

@ -3,7 +3,7 @@
#define _ASM_GENERIC_KMAP_SIZE_H
/* For debug this provides guard pages between the maps */
#ifdef CONFIG_DEBUG_HIGHMEM
#ifdef CONFIG_DEBUG_KMAP_LOCAL
# define KM_MAX_IDX 33
#else
# define KM_MAX_IDX 16

8
lib/Kconfig.debug
View File

@ -849,9 +849,17 @@ config DEBUG_PER_CPU_MAPS
Say N if unsure.
config DEBUG_KMAP_LOCAL
bool "Debug kmap_local temporary mappings"
depends on DEBUG_KERNEL && KMAP_LOCAL
help
This option enables additional error checking for the kmap_local
infrastructure. Disable for production use.
config DEBUG_HIGHMEM
bool "Highmem debugging"
depends on DEBUG_KERNEL && HIGHMEM
select DEBUG_KMAP_LOCAL
help
This option enables additional error checking for high memory
systems. Disable for production systems.

4
mm/highmem.c
View File

@ -368,10 +368,10 @@ EXPORT_SYMBOL(kunmap_high);
static DEFINE_PER_CPU(int, __kmap_local_idx);
/*
* With DEBUG_HIGHMEM the stack depth is doubled and every second
* With DEBUG_KMAP_LOCAL the stack depth is doubled and every second
* slot is unused which acts as a guard page
*/
#ifdef CONFIG_DEBUG_HIGHMEM
#ifdef CONFIG_DEBUG_KMAP_LOCAL
# define KM_INCR 2
#else
# define KM_INCR 1