[RFC 2/5] sbm: enhance buffer mapping API

[Petr Tesarik]

From: Petr Tesarik <petr.tesarik1@xxxxxxxxxxxxxxxxxxx>

Add SBM_MAP_READONLY() and SBM_MAP_WRITABLE() to the public API to allow
mapping kernel buffers directly into the sandbox with no copying.

Signed-off-by: Petr Tesarik <petr.tesarik1@xxxxxxxxxxxxxxxxxxx>
---
 include/linux/sbm.h | 71 +++++++++++++++++++++++++++++++++++++++++++++
 kernel/sbm.c        | 34 ++++++++++++++++++++++
 2 files changed, 105 insertions(+)

diff --git a/include/linux/sbm.h b/include/linux/sbm.h
index 98fd27cd58d0..dbdc0781349f 100644
--- a/include/linux/sbm.h
+++ b/include/linux/sbm.h
@@ -181,6 +181,31 @@ static inline void *sbm_add_buf(struct sbm *sbm, struct sbm_buf **list,
 #define SBM_COPY_INOUT(sbm, buf, size) \
 	((typeof(({buf; })))sbm_add_buf((sbm), &(sbm)->io, (buf), (size)))
 
+/**
+ * sbm_map_readonly() - Map memory for reading.
+ * @sbm:   SBM instance.
+ * @ptr:   Starting virtual address.
+ * @size:  Size in bytes.
+ *
+ * Make the specified virtual address range readable in sandbox code.
+ *
+ * Return: Address of the buffer, or %NULL on error.
+ */
+void *sbm_map_readonly(struct sbm *sbm, const void *ptr, size_t size);
+
+/**
+ * sbm_map_writable() - Map memory for reading and writing.
+ * @sbm:   SBM instance.
+ * @ptr:   Starting virtual address.
+ * @size:  Size in bytes.
+ *
+ * Make the specified virtual address range readable and writable in sandbox
+ * code.
+ *
+ * Return: Address of the buffer, or %NULL on error.
+ */
+void *sbm_map_writable(struct sbm *sbm, const void *ptr, size_t size);
+
 #ifdef CONFIG_HAVE_ARCH_SBM
 
 /**
@@ -303,8 +328,54 @@ static inline int sbm_exec(struct sbm *sbm, sbm_func func, void *data)
 #define SBM_COPY_OUT(sbm, buf, size) __SBM_EVAL(buf)
 #define SBM_COPY_INOUT(sbm, buf, size) __SBM_EVAL(buf)
 
+static inline void *sbm_map_readonly(struct sbm *sbm, const void *ptr,
+				     size_t size)
+{
+	return (void *)ptr;
+}
+
+static inline void *sbm_map_writable(struct sbm *sbm, const void *ptr,
+				     size_t size)
+{
+	return (void *)ptr;
+}
+
 #endif /* CONFIG_SANDBOX_MODE */
 
+/**
+ * SBM_MAP_READONLY() - Map an input buffer into SBM.
+ * @sbm:   SBM instance.
+ * @buf:   Buffer virtual address.
+ * @size:  Size of the buffer.
+ *
+ * Make a read-only mapping of buffer in sandbox mode.
+ *
+ * This works with page granularity. If the buffer is not page-aligned,
+ * some data before and/or after the page is also mappeed into the sandbox.
+ * The mapping does not ensure guard pages either.
+ *
+ * Return: Buffer address in sandbox mode (same as kernel mode).
+ */
+#define SBM_MAP_READONLY(sbm, buf, size) \
+	((typeof(({buf; })))sbm_map_readonly((sbm), (buf), (size)))
+
+/**
+ * SBM_MAP_WRITABLE() - Map an input/output buffer into SBM.
+ * @sbm:   SBM instance.
+ * @buf:   Buffer virtual address.
+ * @size:  Size of the buffer.
+ *
+ * Make a writable mapping of buffer in sandbox mode.
+ *
+ * This works with page granularity. If the buffer is not page-aligned,
+ * some data before and/or after the page is also mappeed into the sandbox.
+ * The mapping does not ensure guard pages either.
+ *
+ * Return: Buffer address in sandbox mode (same as kernel mode).
+ */
+#define SBM_MAP_WRITABLE(sbm, buf, size) \
+	((typeof(({buf; })))sbm_map_writable((sbm), (buf), (size)))
+
 /**
  * __SBM_MAP() - Convert parameters to comma-separated expressions.
  * @m: Macro used to convert each pair.
diff --git a/kernel/sbm.c b/kernel/sbm.c
index df57184f5d87..c832808b538e 100644
--- a/kernel/sbm.c
+++ b/kernel/sbm.c
@@ -71,6 +71,40 @@ void sbm_destroy(struct sbm *sbm)
 }
 EXPORT_SYMBOL(sbm_destroy);
 
+void *sbm_map_readonly(struct sbm *sbm, const void *ptr, size_t size)
+{
+	struct sbm_buf buf;
+
+	if (sbm->error)
+		return NULL;
+
+	buf.sbm_ptr = (void *)ptr;
+	buf.size = size;
+	sbm->error = arch_sbm_map_readonly(sbm, &buf);
+	if (sbm->error)
+		return NULL;
+
+	return buf.sbm_ptr;
+}
+EXPORT_SYMBOL(sbm_map_readonly);
+
+void *sbm_map_writable(struct sbm *sbm, const void *ptr, size_t size)
+{
+	struct sbm_buf buf;
+
+	if (sbm->error)
+		return NULL;
+
+	buf.sbm_ptr = (void *)ptr;
+	buf.size = size;
+	sbm->error = arch_sbm_map_writable(sbm, &buf);
+	if (sbm->error)
+		return NULL;
+
+	return buf.sbm_ptr;
+}
+EXPORT_SYMBOL(sbm_map_writable);
+
 /* Copy input buffers into a sandbox. */
 static int sbm_copy_in(struct sbm *sbm)
 {
-- 
2.34.1