[PATCH v3 0/5] Read-only memremap()

From: Stephen Boyd
Date: Tue Sep 10 2019 - 12:09:25 EST

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/20190614203717.75479-1-swboyd@xxxxxxxxxxxx):
* 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 <evgreen@xxxxxxxxxxxx>
Cc: Rob Herring <robh+dt@xxxxxxxxxx>
Cc: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
Cc: Andy Gross <agross@xxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>

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
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