From 087aaffcdf9c91667c93923fbc05fa8fb6bc7d3a Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Wed, 22 Sep 2010 18:34:36 -0400 Subject: ARM: implement CONFIG_STRICT_DEVMEM by disabling access to RAM via /dev/mem There are very few legitimate use cases, if any, for directly accessing system RAM through /dev/mem. So let's mimic what they do on x86 and forbid it when CONFIG_STRICT_DEVMEM is turned on. Signed-off-by: Nicolas Pitre --- arch/arm/mm/mmap.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'arch/arm/mm/mmap.c') diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c index 4f5b39687df5..b0a98305055c 100644 --- a/arch/arm/mm/mmap.c +++ b/arch/arm/mm/mmap.c @@ -144,3 +144,25 @@ int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) { return !(pfn + (size >> PAGE_SHIFT) > 0x00100000); } + +#ifdef CONFIG_STRICT_DEVMEM + +#include + +/* + * devmem_is_allowed() checks to see if /dev/mem access to a certain + * address is valid. The argument is a physical page number. + * We mimic x86 here by disallowing access to system RAM as well as + * device-exclusive MMIO regions. This effectively disable read()/write() + * on /dev/mem. + */ +int devmem_is_allowed(unsigned long pfn) +{ + if (iomem_is_exclusive(pfn << PAGE_SHIFT)) + return 0; + if (!page_is_ram(pfn)) + return 1; + return 0; +} + +#endif -- cgit