In order to allow access to second half of address space on 64-bit
machines, add code that creates /dev/highmem dedicated for that.
Note that due to maximum file size being limited to MAX_LFS_FILESIZE
or 0x7fff_ffff_ffff_ffff bytes at addresses 0x7fff_ffff_ffff_ffff and
0xffff_ffff_ffff_ffff cannot be access through /dev/mem and
/dev/hightmem correspondingly.
Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
---
drivers/misc/mem.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/drivers/misc/mem.c b/drivers/misc/mem.c
index 2f3316307..e3fb0d04a 100644
--- a/drivers/misc/mem.c
+++ b/drivers/misc/mem.c
@@ -7,6 +7,10 @@
#include <driver.h>
#include <init.h>
+#include <linux/pagemap.h>
+#include <linux/fs.h>
+
+
static struct cdev_operations memops = {
.read = mem_read_nofail,
.write = mem_write,
@@ -21,8 +25,7 @@ static int mem_probe(struct device_d *dev)
dev->priv = cdev;
cdev->name = (char*)dev->resource[0].name;
- cdev->size = min_t(unsigned long long, resource_size(&dev->resource[0]),
- S64_MAX);
+ cdev->size = resource_size(&dev->resource[0]);
cdev->ops = &memops;
cdev->dev = dev;
@@ -38,7 +41,21 @@ static struct driver_d mem_drv = {
static int mem_init(void)
{
- add_mem_device("mem", 0, ~0, IORESOURCE_MEM_WRITEABLE);
+ const resource_size_t size = min_t(unsigned long long,
+ MAX_LFS_FILESIZE,
+ (resource_size_t)~0);
+ add_mem_device("mem", 0, size, IORESOURCE_MEM_WRITEABLE);
+ /*
+ * We can't fit all of 64-bit address space into a single
+ * file, so we create a separate one to allow acces to the
+ * second half
+ */
+ if (IS_ENABLED(CONFIG_CPU_64))
+ add_mem_device("highmem",
+ (resource_size_t)MAX_LFS_FILESIZE + 1,
+ size,
+ IORESOURCE_MEM_WRITEABLE);
+
return platform_driver_register(&mem_drv);
}
device_initcall(mem_init);
--
2.20.1
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