misc: sram: Integrate protect-exec reserved sram area type

Introduce a new "protect-exec" reserved sram area type which is
makes use of the the existing functionality provided for the "pool"
sram region type for use with the genalloc framework and with the
added requirement that it be maintained as read-only and executable
while allowing for an arbitrary number of drivers to share the space.

This introduces a common way to maintain a region of sram as read-only
and executable and also introduces a helper function, sram_exec_copy,
which allows for copying data to this protected region while maintaining
locking to avoid conflicts between multiple users of the same space. A
region of memory that is marked with the "protect-exec" flag in the
device tree also has the requirement of providing a page aligned block
of memory so that the page attribute manipulation does not affect
surrounding regions.

Also, selectively enable this only for builds that support set_memory_*
calls, for now just ARM, through the use of Kconfig.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/devicetree/bindings/sram/sram.txt b/Documentation/devicetree/bindings/sram/sram.txt
index 068c2c03c38f7226dd36a6a38ea12a6d87565892..267da4410aefd0ac8e17beedfc33adf394e014e4 100644 (file)
--- a/Documentation/devicetree/bindings/sram/sram.txt
+++ b/Documentation/devicetree/bindings/sram/sram.txt
@@ -42,6 +42,12 @@ Optional properties in the area nodes:
          and in use by another device or devices
 - export : indicates that the reserved SRAM area may be accessed outside
            of the kernel, e.g. by bootloader or userspace
+- protect-exec : Same as 'pool' above but with the additional
+                constraint that code wil be run from the region and
+                that the memory is maintained as read-only, executable
+                during code execution. NOTE: This region must be page
+                aligned on start and end in order to properly allow
+                manipulation of the page attributes.
 - label : the name for the reserved partition, if omitted, the label
           is taken from the node name excluding the unit address.
 

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 64971baf11faebaff879c58067d23fd9bf29895a..0444a8f9b0947ec5fe96464e0bf9ac47f46e6a16 100644 (file)
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -474,11 +474,15 @@ config SRAM
        bool "Generic on-chip SRAM driver"
        depends on HAS_IOMEM
        select GENERIC_ALLOCATOR
+       select SRAM_EXEC if ARM
        help
          This driver allows you to declare a memory region to be managed by
          the genalloc API. It is supposed to be used for small on-chip SRAM
          areas found on many SoCs.
 
+config SRAM_EXEC
+       bool
+
 config VEXPRESS_SYSCFG
        bool "Versatile Express System Configuration driver"
        depends on VEXPRESS_CONFIG

diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 31983366090a781441a3235cac5883d6fbb27fa4..7a3ea89339b4d07c34289a539c4f9bd2f12d2aff 100644 (file)
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -47,6 +47,7 @@ obj-$(CONFIG_INTEL_MEI)               += mei/
 obj-$(CONFIG_VMWARE_VMCI)      += vmw_vmci/
 obj-$(CONFIG_LATTICE_ECP3_CONFIG)      += lattice-ecp3-config.o
 obj-$(CONFIG_SRAM)             += sram.o
+obj-$(CONFIG_SRAM_EXEC)                += sram-exec.o
 obj-y                          += mic/
 obj-$(CONFIG_GENWQE)           += genwqe/
 obj-$(CONFIG_ECHO)             += echo/

diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
index 5a6e001845c23e33862f93ca621ef4f9e7ba0ade..d1185b78cf9aa4208620f27913ba1bddad96d411 100644 (file)
--- a/drivers/misc/sram.c
+++ b/drivers/misc/sram.c
@@ -122,6 +122,18 @@ static int sram_add_partition(struct sram_dev *sram, struct sram_reserve *block,
                if (ret)
                        return ret;
        }
+       if (block->protect_exec) {
+               ret = sram_check_protect_exec(sram, block, part);
+               if (ret)
+                       return ret;
+
+               ret = sram_add_pool(sram, block, start, part);
+               if (ret)
+                       return ret;
+
+               sram_add_protect_exec(part);
+       }
+
        sram->partitions++;
 
        return 0;
@@ -207,7 +219,11 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
                if (of_find_property(child, "pool", NULL))
                        block->pool = true;
 
-               if ((block->export || block->pool) && block->size) {
+               if (of_find_property(child, "protect-exec", NULL))
+                       block->protect_exec = true;
+
+               if ((block->export || block->pool || block->protect_exec) &&
+                   block->size) {
                        exports++;
 
                        label = NULL;
@@ -269,7 +285,8 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
                        goto err_chunks;
                }
 
-               if ((block->export || block->pool) && block->size) {
+               if ((block->export || block->pool || block->protect_exec) &&
+                   block->size) {
                        ret = sram_add_partition(sram, block,
                                                 res->start + block->start);
                        if (ret) {

diff --git a/drivers/misc/sram.h b/drivers/misc/sram.h
index b268cd3f55bb132292570f8333597a283fb6fec5..c181ce4c8fca8221e1a1153d411491426c180b75 100644 (file)
--- a/drivers/misc/sram.h
+++ b/drivers/misc/sram.h
@@ -34,6 +34,7 @@ struct sram_reserve {
        u32 size;
        bool export;
        bool pool;
+       bool protect_exec;
        const char *label;
 };