[PATCH v3] driver-staging: vsoc.c: Add sysfs support for examining the permissions of regions.

[Jerry Lin]

Add a attribute called permissions under vsoc device node for examining
current granted permissions in vsoc_device.

This file will display permissions in following format:
  begin_offset  end_offset  owner_offset  owned_value
            %x          %x            %x           %x

Signed-off-by: Jerry Lin <wahaha...@gmail.com>
---
 drivers/staging/android/vsoc.c | 48 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 45 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/android/vsoc.c b/drivers/staging/android/vsoc.c
index 22571ab..8ce3604 100644
--- a/drivers/staging/android/vsoc.c
+++ b/drivers/staging/android/vsoc.c
@@ -128,9 +128,10 @@ struct vsoc_device {
 
 static struct vsoc_device vsoc_dev;
 
-/*
- * TODO(ghartman): Add a /sys filesystem entry that summarizes the permissions.
- */
+static ssize_t permissions_show(struct device *dev,
+                               struct device_attribute *attr,
+                               char *buf);
+static DEVICE_ATTR_RO(permissions);
 
 struct fd_scoped_permission_node {
        struct fd_scoped_permission permission;
@@ -718,6 +719,37 @@ static ssize_t vsoc_write(struct file *filp, const char 
__user *buffer,
        return len;
 }
 
+static ssize_t permissions_show(struct device *dev,
+                               struct device_attribute *attr,
+                               char *buffer)
+{
+       struct fd_scoped_permission_node *node;
+       char *row;
+       int ret;
+       ssize_t written = 0;
+
+       row = kzalloc(sizeof(char) * 128, GFP_KERNEL);
+       if (!row)
+               return 0;
+       mutex_lock(&vsoc_dev.mtx);
+       list_for_each_entry(node, &vsoc_dev.permissions, list) {
+               ret = snprintf(row, 128, "%x\t%x\t%x\t%x\n",
+                              node->permission.begin_offset,
+                              node->permission.end_offset,
+                              node->permission.owner_offset,
+                              node->permission.owned_value);
+               if (ret < 0)
+                       goto done;
+               memcpy(buffer + written, row, ret);
+               written += ret;
+       }
+
+done:
+       mutex_unlock(&vsoc_dev.mtx);
+       kfree(row);
+       return written;
+}
+
 static irqreturn_t vsoc_interrupt(int irq, void *region_data_v)
 {
        struct vsoc_region_data *region_data =
@@ -942,6 +974,15 @@ static int vsoc_probe_device(struct pci_dev *pdev,
                }
                vsoc_dev.regions_data[i].device_created = true;
        }
+       /*
+        * Create permission attribute on device node.
+        */
+       result = device_create_file(&pdev->dev, &dev_attr_permissions);
+       if (result) {
+               dev_err(&vsoc_dev.dev->dev, "device_create_file failed\n");
+               vsoc_remove_device(pdev);
+               return -EFAULT;
+       }
        return 0;
 }
 
@@ -967,6 +1008,7 @@ static void vsoc_remove_device(struct pci_dev *pdev)
        if (!pdev || !vsoc_dev.dev)
                return;
        dev_info(&pdev->dev, "remove_device\n");
+       device_remove_file(&pdev->dev, &dev_attr_permissions);
        if (vsoc_dev.regions_data) {
                for (i = 0; i < vsoc_dev.layout->region_count; ++i) {
                        if (vsoc_dev.regions_data[i].device_created) {
-- 
2.7.4

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