linux-kernel - [RFC/PATCH 0/5] Read-only memremap() proposal

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Date:   Fri, 17 May 2019 09:47:41 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        Evan Green <evgreen@...omium.org>,
        Rob Herring <robh+dt@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: [RFC/PATCH 0/5] Read-only memremap() proposal

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.

Cc: Evan Green <evgreen@...omium.org>
Cc: Rob Herring <robh+dt@...nel.org>
Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
Cc: Andy Gross <agross@...nel.org>
Cc: Will Deacon <will.deacon@....com>
Cc: Catalin Marinas <catalin.marinas@....com>

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

 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                  | 15 +++++++++--
 6 files changed, 70 insertions(+), 12 deletions(-)


base-commit: 9e98c678c2d6ae3a17cb2de55d17f69dddaa231b
prerequisite-patch-id: 62119e27c0c0686e02f0cb55c296b878fb7f5e47
prerequisite-patch-id: bda32cfc1733c245ae3f141d7c27b18e4adcc628
prerequisite-patch-id: b8f8097161bd15e87d54dcfbfa67b9ca1abc7204
-- 
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