From: Thomas Gleixner <[email protected]>
For the write_atomic callback, the console driver may have unsafe
regions that need to be appropriately marked. Provide functions
that accept the nbcon_write_context struct to allow for the driver
to enter and exit unsafe regions.
Co-developed-by: John Ogness <[email protected]>
Signed-off-by: John Ogness <[email protected]>
Signed-off-by: Thomas Gleixner (Intel) <[email protected]>
---
include/linux/console.h | 4 ++++
kernel/printk/printk_nbcon.c | 41 +++++++++++++++++++++++++++++++++++-
2 files changed, 44 insertions(+), 1 deletion(-)
diff --git a/include/linux/console.h b/include/linux/console.h
index 3d129b2b70a1..e4ce1015627c 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -456,8 +456,12 @@ static inline bool console_is_registered(const struct console *con)
#ifdef CONFIG_PRINTK
extern bool nbcon_can_proceed(struct nbcon_write_context *wctxt);
+extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt);
+extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt);
#else
static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { return false; }
+static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) { return false; }
+static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { return false; }
#endif
extern int console_set_on_cmdline;
diff --git a/kernel/printk/printk_nbcon.c b/kernel/printk/printk_nbcon.c
index e1f0e4278ffa..57b7539bbbb2 100644
--- a/kernel/printk/printk_nbcon.c
+++ b/kernel/printk/printk_nbcon.c
@@ -761,7 +761,6 @@ EXPORT_SYMBOL_GPL(nbcon_can_proceed);
*
* Internal helper to avoid duplicated code
*/
-__maybe_unused
static bool nbcon_context_update_unsafe(struct nbcon_context *ctxt, bool unsafe)
{
struct console *con = ctxt->console;
@@ -787,6 +786,46 @@ static bool nbcon_context_update_unsafe(struct nbcon_context *ctxt, bool unsafe)
return true;
}
+/**
+ * nbcon_enter_unsafe - Enter an unsafe region in the driver
+ * @wctxt: The write context that was handed to the write function
+ *
+ * Return: True if the state is correct. False if ownership was
+ * handed over or taken.
+ *
+ * When this function returns false then the calling context is no longer
+ * the owner and is no longer allowed to go forward. In this case it must
+ * back out immediately and carefully. The buffer content is also no longer
+ * trusted since it no longer belongs to the calling context.
+ */
+bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt)
+{
+ struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
+
+ return nbcon_context_update_unsafe(ctxt, true);
+}
+EXPORT_SYMBOL_GPL(nbcon_enter_unsafe);
+
+/**
+ * nbcon_exit_unsafe - Exit an unsafe region in the driver
+ * @wctxt: The write context that was handed to the write function
+ *
+ * Return: True if the state is correct. False if ownership was
+ * handed over or taken.
+ *
+ * When this function returns false then the calling context is no longer
+ * the owner and is no longer allowed to go forward. In this case it must
+ * back out immediately and carefully. The buffer content is also no longer
+ * trusted since it no longer belongs to the calling context.
+ */
+bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt)
+{
+ struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
+
+ return nbcon_context_update_unsafe(ctxt, false);
+}
+EXPORT_SYMBOL_GPL(nbcon_exit_unsafe);
+
/**
* nbcon_emit_next_record - Emit a record in the acquired context
* @wctxt: The write context that will be handed to the write function
--
2.39.2
On Fri 2023-07-28 02:08:33, John Ogness wrote:
> From: Thomas Gleixner <[email protected]>
>
> For the write_atomic callback, the console driver may have unsafe
> regions that need to be appropriately marked. Provide functions
> that accept the nbcon_write_context struct to allow for the driver
> to enter and exit unsafe regions.
>
> diff --git a/kernel/printk/printk_nbcon.c b/kernel/printk/printk_nbcon.c
> index e1f0e4278ffa..57b7539bbbb2 100644
> --- a/kernel/printk/printk_nbcon.c
> +++ b/kernel/printk/printk_nbcon.c
> @@ -761,7 +761,6 @@ EXPORT_SYMBOL_GPL(nbcon_can_proceed);
> *
> * Internal helper to avoid duplicated code
> */
> -__maybe_unused
> static bool nbcon_context_update_unsafe(struct nbcon_context *ctxt, bool unsafe)
> {
> struct console *con = ctxt->console;
It might be better to define nbcon_context_update_unsafe()
in this patch. I guess that nbcon_enter_unsafe()/nbcon_exit_unsafe()
are the only callers.
> @@ -787,6 +786,46 @@ static bool nbcon_context_update_unsafe(struct nbcon_context *ctxt, bool unsafe)
> return true;
> }
>
> +/**
> + * nbcon_enter_unsafe - Enter an unsafe region in the driver
> + * @wctxt: The write context that was handed to the write function
> + *
> + * Return: True if the state is correct. False if ownership was
> + * handed over or taken.
Same as in 7th patch. I would write:
* Return: True if this context still owns the console. False
if the ownership has been handed over or taken.
> + *
> + * When this function returns false then the calling context is no longer
> + * the owner and is no longer allowed to go forward. In this case it must
> + * back out immediately and carefully. The buffer content is also no longer
> + * trusted since it no longer belongs to the calling context.
> + */
> +bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt)
> +{
> + struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
> +
> + return nbcon_context_update_unsafe(ctxt, true);
> +}
> +EXPORT_SYMBOL_GPL(nbcon_enter_unsafe);
> +
> +/**
> + * nbcon_exit_unsafe - Exit an unsafe region in the driver
> + * @wctxt: The write context that was handed to the write function
> + *
> + * Return: True if the state is correct. False if ownership was
> + * handed over or taken.
Same here.
> + * When this function returns false then the calling context is no longer
> + * the owner and is no longer allowed to go forward. In this case it must
> + * back out immediately and carefully. The buffer content is also no longer
> + * trusted since it no longer belongs to the calling context.
> + */
> +bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt)
> +{
> + struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
> +
> + return nbcon_context_update_unsafe(ctxt, false);
> +}
> +EXPORT_SYMBOL_GPL(nbcon_exit_unsafe);
> +
Best Regards,
Petr