debugfs: use specified mode to possibly mark files read/write only

In many SoC implementations there are hardware registers can be read or
write only.  This extends the debugfs to enforce the file permissions for
these types of registers by providing a set of fops which are read or
write only.  This assumes that the kernel developer knows more about the
hardware than the user (even root users) -- which is normally true.

Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 63 insertions, 0 deletions

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 39a619c..4d74fc7 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -67,6 +67,8 @@ static int debugfs_u8_get(void *data, u64 *val)
 	return 0;
 }
 DEFINE_SIMPLE_ATTRIBUTE(fops_u8, debugfs_u8_get, debugfs_u8_set, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_u8_ro, debugfs_u8_get, NULL, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_u8_wo, NULL, debugfs_u8_set, "%llu\n");
 
 /**
  * debugfs_create_u8 - create a debugfs file that is used to read and write an unsigned 8-bit value
@@ -95,6 +97,13 @@ DEFINE_SIMPLE_ATTRIBUTE(fops_u8, debugfs_u8_get, debugfs_u8_set, "%llu\n");
 struct dentry *debugfs_create_u8(const char *name, mode_t mode,
 				 struct dentry *parent, u8 *value)
 {
+	/* if there are no write bits set, make read only */
+	if (!(mode & S_IWUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_u8_ro);
+	/* if there are no read bits set, make write only */
+	if (!(mode & S_IRUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_u8_wo);
+
 	return debugfs_create_file(name, mode, parent, value, &fops_u8);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_u8);
@@ -110,6 +119,8 @@ static int debugfs_u16_get(void *data, u64 *val)
 	return 0;
 }
 DEFINE_SIMPLE_ATTRIBUTE(fops_u16, debugfs_u16_get, debugfs_u16_set, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_u16_ro, debugfs_u16_get, NULL, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_u16_wo, NULL, debugfs_u16_set, "%llu\n");
 
 /**
  * debugfs_create_u16 - create a debugfs file that is used to read and write an unsigned 16-bit value
@@ -138,6 +149,13 @@ DEFINE_SIMPLE_ATTRIBUTE(fops_u16, debugfs_u16_get, debugfs_u16_set, "%llu\n");
 struct dentry *debugfs_create_u16(const char *name, mode_t mode,
 				  struct dentry *parent, u16 *value)
 {
+	/* if there are no write bits set, make read only */
+	if (!(mode & S_IWUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_u16_ro);
+	/* if there are no read bits set, make write only */
+	if (!(mode & S_IRUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_u16_wo);
+
 	return debugfs_create_file(name, mode, parent, value, &fops_u16);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_u16);
@@ -153,6 +171,8 @@ static int debugfs_u32_get(void *data, u64 *val)
 	return 0;
 }
 DEFINE_SIMPLE_ATTRIBUTE(fops_u32, debugfs_u32_get, debugfs_u32_set, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_u32_ro, debugfs_u32_get, NULL, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_u32_wo, NULL, debugfs_u32_set, "%llu\n");
 
 /**
  * debugfs_create_u32 - create a debugfs file that is used to read and write an unsigned 32-bit value
@@ -181,6 +201,13 @@ DEFINE_SIMPLE_ATTRIBUTE(fops_u32, debugfs_u32_get, debugfs_u32_set, "%llu\n");
 struct dentry *debugfs_create_u32(const char *name, mode_t mode,
 				 struct dentry *parent, u32 *value)
 {
+	/* if there are no write bits set, make read only */
+	if (!(mode & S_IWUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_u32_ro);
+	/* if there are no read bits set, make write only */
+	if (!(mode & S_IRUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_u32_wo);
+
 	return debugfs_create_file(name, mode, parent, value, &fops_u32);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_u32);
@@ -197,6 +224,8 @@ static int debugfs_u64_get(void *data, u64 *val)
 	return 0;
 }
 DEFINE_SIMPLE_ATTRIBUTE(fops_u64, debugfs_u64_get, debugfs_u64_set, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_u64_ro, debugfs_u64_get, NULL, "%llu\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_u64_wo, NULL, debugfs_u64_set, "%llu\n");
 
 /**
  * debugfs_create_u64 - create a debugfs file that is used to read and write an unsigned 64-bit value
@@ -225,15 +254,28 @@ DEFINE_SIMPLE_ATTRIBUTE(fops_u64, debugfs_u64_get, debugfs_u64_set, "%llu\n");
 struct dentry *debugfs_create_u64(const char *name, mode_t mode,
 				 struct dentry *parent, u64 *value)
 {
+	/* if there are no write bits set, make read only */
+	if (!(mode & S_IWUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_u64_ro);
+	/* if there are no read bits set, make write only */
+	if (!(mode & S_IRUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_u64_wo);
+
 	return debugfs_create_file(name, mode, parent, value, &fops_u64);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_u64);
 
 DEFINE_SIMPLE_ATTRIBUTE(fops_x8, debugfs_u8_get, debugfs_u8_set, "0x%02llx\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_x8_ro, debugfs_u8_get, NULL, "0x%02llx\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_x8_wo, NULL, debugfs_u8_set, "0x%02llx\n");
 
 DEFINE_SIMPLE_ATTRIBUTE(fops_x16, debugfs_u16_get, debugfs_u16_set, "0x%04llx\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_x16_ro, debugfs_u16_get, NULL, "0x%04llx\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_x16_wo, NULL, debugfs_u16_set, "0x%04llx\n");
 
 DEFINE_SIMPLE_ATTRIBUTE(fops_x32, debugfs_u32_get, debugfs_u32_set, "0x%08llx\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_x32_ro, debugfs_u32_get, NULL, "0x%08llx\n");
+DEFINE_SIMPLE_ATTRIBUTE(fops_x32_wo, NULL, debugfs_u32_set, "0x%08llx\n");
 
 /*
  * debugfs_create_x{8,16,32} - create a debugfs file that is used to read and write an unsigned {8,16,32}-bit value
@@ -256,6 +298,13 @@ DEFINE_SIMPLE_ATTRIBUTE(fops_x32, debugfs_u32_get, debugfs_u32_set, "0x%08llx\n"
 struct dentry *debugfs_create_x8(const char *name, mode_t mode,
 				 struct dentry *parent, u8 *value)
 {
+	/* if there are no write bits set, make read only */
+	if (!(mode & S_IWUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_x8_ro);
+	/* if there are no read bits set, make write only */
+	if (!(mode & S_IRUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_x8_wo);
+
 	return debugfs_create_file(name, mode, parent, value, &fops_x8);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_x8);
@@ -273,6 +322,13 @@ EXPORT_SYMBOL_GPL(debugfs_create_x8);
 struct dentry *debugfs_create_x16(const char *name, mode_t mode,
 				 struct dentry *parent, u16 *value)
 {
+	/* if there are no write bits set, make read only */
+	if (!(mode & S_IWUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_x16_ro);
+	/* if there are no read bits set, make write only */
+	if (!(mode & S_IRUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_x16_wo);
+
 	return debugfs_create_file(name, mode, parent, value, &fops_x16);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_x16);
@@ -290,6 +346,13 @@ EXPORT_SYMBOL_GPL(debugfs_create_x16);
 struct dentry *debugfs_create_x32(const char *name, mode_t mode,
 				 struct dentry *parent, u32 *value)
 {
+	/* if there are no write bits set, make read only */
+	if (!(mode & S_IWUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_x32_ro);
+	/* if there are no read bits set, make write only */
+	if (!(mode & S_IRUGO))
+		return debugfs_create_file(name, mode, parent, value, &fops_x32_wo);
+
 	return debugfs_create_file(name, mode, parent, value, &fops_x32);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_x32);