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| author | Thomas Gleixner <tglx@linutronix.de> | 2020-11-18 20:48:40 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2020-11-24 14:42:08 +0100 |
| commit | 0e91a0c6984c837a7c6760e3f28e8e1c532abf87 (patch) | |
| tree | ca90a3abad7717fa27186c38c2ed0c02f93ab7de | |
| parent | 6e799cb69a70eedbb41561b750f7180c12cff280 (diff) | |
| download | kernel_replicant_linux-0e91a0c6984c837a7c6760e3f28e8e1c532abf87.tar.gz kernel_replicant_linux-0e91a0c6984c837a7c6760e3f28e8e1c532abf87.tar.bz2 kernel_replicant_linux-0e91a0c6984c837a7c6760e3f28e8e1c532abf87.zip | |
mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP
CONFIG_DEBUG_KMAP_LOCAL, which is selected by CONFIG_DEBUG_HIGHMEM is only
providing guard pages, but does not provide a mechanism to enforce the
usage of the kmap_local() infrastructure.
Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP which forces the temporary
mapping even for lowmem pages. This needs to be a seperate config switch
because this only works on architectures which do not have cache aliasing
problems.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201118204007.028261233@linutronix.de
| -rw-r--r-- | lib/Kconfig.debug | 14 | ||||
| -rw-r--r-- | mm/highmem.c | 12 |
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 |