This patch series implements a read-only version of memremap() via a new MEMREMAP_RO flag. If this is passed in the mapping call, we'll try to map the memory region as read-only if it doesn't intersect with an existing mapping. Otherwise, we'll try to fallback to other flags to try to map the memory that way.
The main use case I have is to map the command-db memory region on Qualcomm devices with a read-only mapping. It's already a const marked pointer and the API returns const pointers as well, so this series makes sure that even stray writes can't modify the memory. To get there we introduce a devm version of memremap() for a reserved memory region, add a memremap() flag, and implement support for that flag on arm64. Changes from v2 (https://lkml.kernel.org/r/[email protected]): * Added a comment to kerneldoc for the new MEMREMAP_RO flag * Rebased to v5.3-rc1 Changes from v1: * Picked up tags and rebased to v5.2-rc3 Stephen Boyd (5): reserved_mem: Add a devm_memremap_reserved_mem() API soc: qcom: cmd-db: Migrate to devm_memremap_reserved_mem() memremap: Add support for read-only memory mappings arm64: Add support for arch_memremap_ro() soc: qcom: cmd-db: Map with read-only mappings Cc: Evan Green <[email protected]> Cc: Rob Herring <[email protected]> Cc: Bjorn Andersson <[email protected]> Cc: Andy Gross <[email protected]> Cc: Will Deacon <[email protected]> Cc: Catalin Marinas <[email protected]> arch/arm64/include/asm/io.h | 1 + drivers/of/of_reserved_mem.c | 45 +++++++++++++++++++++++++++++++++ drivers/soc/qcom/cmd-db.c | 14 +++------- include/linux/io.h | 1 + include/linux/of_reserved_mem.h | 6 +++++ kernel/iomem.c | 20 ++++++++++++--- 6 files changed, 74 insertions(+), 13 deletions(-) base-commit: 5f9e832c137075045d15cd6899ab0505cfb2ca4b -- Sent by a computer through tubes
