mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL

2020-11-24T13:42:08+00:00

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 Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20201118204006.869487226@linutronix.de

asm-generic: Provide kmap_size.h

2020-11-06T22:14:54+00:00

kmap_types.h is a misnomer because the old atomic MAP based array does not exist anymore and the whole indirection of architectures including kmap_types.h is inconinstent and does not allow to provide guard page debugging for this misfeature. Add a common header file which defines the mapping stack size for all architectures. Will be used when converting architectures over to a generic kmap_local/atomic implementation. The array size is chosen with the following constraints in mind: - The deepest nest level in one context is 3 according to code inspection. - The worst case nesting for the upcoming reemptible version would be: 2 maps in task context and a fault inside 2 maps in the fault handler 3 maps in softirq 2 maps in interrupt So a total of 16 is sufficient and probably overestimated. Signed-off-by: Thomas Gleixner Acked-by: Arnd Bergmann Cc: Andrew Morton Link: https://lore.kernel.org/r/20201103095857.078043987@linutronix.de

kernel/linux.git/include/asm-generic/kmap_size.h, branch v6.6.131

mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL

asm-generic: Provide kmap_size.h