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Fri, 17 May 2019 09:47:53 -0700 (PDT) From: Stephen Boyd To: linux-kernel@vger.kernel.org Subject: [RFC/PATCH 3/5] memremap: Add support for read-only memory mappings Date: Fri, 17 May 2019 09:47:44 -0700 Message-Id: <20190517164746.110786-4-swboyd@chromium.org> X-Mailer: git-send-email 2.21.0.1020.gf2820cf01a-goog In-Reply-To: <20190517164746.110786-1-swboyd@chromium.org> References: <20190517164746.110786-1-swboyd@chromium.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190517_094754_320603_3B55FDAF X-CRM114-Status: GOOD ( 15.84 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org, Will Deacon , Andy Gross , Evan Green , Bjorn Andersson , Rob Herring , Catalin Marinas , Dan Williams , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Sometimes we have memories that are supposed to be read-only, but when we map these regions the best we can do is map them as write-back with MEMREMAP_WB. Introduce a read-only memory mapping (MEMREMAP_RO) that allows us to map reserved memory regions as read-only. This way, we're less likely to see these special memory regions become corrupted by stray writes to them. Cc: Evan Green Cc: Rob Herring Cc: Bjorn Andersson Cc: Andy Gross Cc: Will Deacon Cc: Catalin Marinas Cc: Dan Williams Signed-off-by: Stephen Boyd --- include/linux/io.h | 1 + kernel/iomem.c | 15 +++++++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/include/linux/io.h b/include/linux/io.h index 32e30e8fb9db..16c7f4498869 100644 --- a/include/linux/io.h +++ b/include/linux/io.h @@ -159,6 +159,7 @@ enum { MEMREMAP_WC = 1 << 2, MEMREMAP_ENC = 1 << 3, MEMREMAP_DEC = 1 << 4, + MEMREMAP_RO = 1 << 5, }; void *memremap(resource_size_t offset, size_t size, unsigned long flags); diff --git a/kernel/iomem.c b/kernel/iomem.c index f7525e14ebc6..8d3cf74a32cb 100644 --- a/kernel/iomem.c +++ b/kernel/iomem.c @@ -19,6 +19,13 @@ static void *arch_memremap_wb(resource_size_t offset, unsigned long size) } #endif +#ifndef arch_memremap_ro +static void *arch_memremap_ro(resource_size_t offset, unsigned long size) +{ + return NULL; +} +#endif + #ifndef arch_memremap_can_ram_remap static bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size, unsigned long flags) @@ -84,7 +91,10 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags) } /* Try all mapping types requested until one returns non-NULL */ - if (flags & MEMREMAP_WB) { + if ((flags & MEMREMAP_RO) && is_ram != REGION_INTERSECTS) + addr = arch_memremap_ro(offset, size); + + if (!addr && (flags & MEMREMAP_WB)) { /* * MEMREMAP_WB is special in that it can be satisifed * from the direct map. Some archs depend on the @@ -103,7 +113,8 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags) * address mapping. Enforce that this mapping is not aliasing * System RAM. */ - if (!addr && is_ram == REGION_INTERSECTS && flags != MEMREMAP_WB) { + if (!addr && is_ram == REGION_INTERSECTS && + (flags != MEMREMAP_WB || flags != MEMREMAP_RO)) { WARN_ONCE(1, "memremap attempted on ram %pa size: %#lx\n", &offset, (unsigned long) size); return NULL; -- Sent by a computer through tubes _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel