linux-kernel - [RESEND PATCH 1/3] memremap: add MEMREMAP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <9085d37fa97a762a46b9d58719c085368682c64f.1452010802.git.brian.starkey@arm.com>
Date:	Tue,  5 Jan 2016 16:41:26 +0000
From:	Brian Starkey <brian.starkey@....com>
To:	gregkh@...uxfoundation.org
Cc:	catalin.marinas@....com, dan.j.williams@...el.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [RESEND PATCH 1/3] memremap: add MEMREMAP_WC flag

Add a flag to memremap() for writecombine mappings. Mappings satisfied
by this flag will not be cached, however writes may be delayed or
combined into more efficient bursts. This is most suitable for
buffers written sequentially by the CPU for use by other DMA devices.

Signed-off-by: Brian Starkey <brian.starkey@....com>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
---
 include/linux/io.h |    1 +
 kernel/memremap.c  |   15 +++++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/linux/io.h b/include/linux/io.h
index 32403b5..e2c8419 100644
--- a/include/linux/io.h
+++ b/include/linux/io.h
@@ -135,6 +135,7 @@ enum {
 	/* See memremap() kernel-doc for usage description... */
 	MEMREMAP_WB = 1 << 0,
 	MEMREMAP_WT = 1 << 1,
+	MEMREMAP_WC = 1 << 2,
 };
 
 void *memremap(resource_size_t offset, size_t size, unsigned long flags);
diff --git a/kernel/memremap.c b/kernel/memremap.c
index e517a16..3849987 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -41,11 +41,13 @@ static void *try_ram_remap(resource_size_t offset, size_t size)
  * memremap() - remap an iomem_resource as cacheable memory
  * @offset: iomem resource start address
  * @size: size of remap
- * @flags: either MEMREMAP_WB or MEMREMAP_WT
+ * @flags: any of MEMREMAP_WB, MEMREMAP_WT and MEMREMAP_WC
  *
  * memremap() is "ioremap" for cases where it is known that the resource
  * being mapped does not have i/o side effects and the __iomem
- * annotation is not applicable.
+ * annotation is not applicable. In the case of multiple flags, the different
+ * mapping types will be attempted in the order listed below until one of
+ * them succeeds.
  *
  * MEMREMAP_WB - matches the default mapping for "System RAM" on
  * the architecture.  This is usually a read-allocate write-back cache.
@@ -57,6 +59,10 @@ static void *try_ram_remap(resource_size_t offset, size_t size)
  * cache or are written through to memory and never exist in a
  * cache-dirty state with respect to program visibility.  Attempts to
  * map "System RAM" with this mapping type will fail.
+ *
+ * MEMREMAP_WC - establish a writecombine mapping, whereby writes may
+ * be coalesced together (e.g. in the CPU's write buffers), but is otherwise
+ * uncached. Attempts to map "System RAM" with this mapping type will fail.
  */
 void *memremap(resource_size_t offset, size_t size, unsigned long flags)
 {
@@ -101,6 +107,11 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags)
 		addr = ioremap_wt(offset, size);
 	}
 
+	if (!addr && (flags & MEMREMAP_WC)) {
+		flags &= ~MEMREMAP_WC;
+		addr = ioremap_wc(offset, size);
+	}
+
 	return addr;
 }
 EXPORT_SYMBOL(memremap);
-- 
1.7.9.5

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/