[PATCH 1/3] ACPI: utils: Add exclusive AML evaluation helpers

["Ali Ahmet Memiş" <aliamemis@disroot.org>]

ACPICA drops the interpreter lock while AML waits, for example around EC
accesses, so two methods can run interleaved. Some firmware relies on
methods not interleaving, for instance by switching an EC page selector
without taking the AML mutex that the other users of that page hold.

Add acpi_evaluate_object_exclusive() and acpi_evaluate_integer_exclusive()
which serialize the evaluation under a global mutex, for callers that are
known to be affected.

Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memiş <aliamemis@disroot.org>
---
 drivers/acpi/utils.c    | 56 +++++++++++++++++++++++++++++++++++++----
 include/acpi/acpi_bus.h |  8 ++++++
 2 files changed, 59 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index d499b72574ab..f28680424f14 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -10,6 +10,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/types.h>
@@ -243,10 +244,34 @@ acpi_extract_package(union acpi_object *package,
 
 EXPORT_SYMBOL(acpi_extract_package);
 
-acpi_status
-acpi_evaluate_integer(acpi_handle handle,
-		      acpi_string pathname,
-		      struct acpi_object_list *arguments, unsigned long long *data)
+static DEFINE_MUTEX(acpi_exclusive_eval_lock);
+
+/**
+ * acpi_evaluate_object_exclusive - Evaluate an object without interleaving
+ * @handle: ACPI handle of the object or its scope.
+ * @pathname: Path of the object relative to @handle.
+ * @arguments: Arguments to pass, or NULL.
+ * @buffer: Buffer for the return value, or NULL.
+ *
+ * Same as acpi_evaluate_object(), but serialized with other exclusive
+ * evaluations.  Use it only for methods known to break when interleaved.
+ */
+acpi_status acpi_evaluate_object_exclusive(acpi_handle handle,
+					   acpi_string pathname,
+					   struct acpi_object_list *arguments,
+					   struct acpi_buffer *buffer)
+{
+	guard(mutex)(&acpi_exclusive_eval_lock);
+
+	return acpi_evaluate_object(handle, pathname, arguments, buffer);
+}
+EXPORT_SYMBOL_GPL(acpi_evaluate_object_exclusive);
+
+static acpi_status __acpi_evaluate_integer(acpi_handle handle,
+					   acpi_string pathname,
+					   struct acpi_object_list *arguments,
+					   unsigned long long *data,
+					   bool exclusive)
 {
 	acpi_status status = AE_OK;
 	union acpi_object element;
@@ -257,7 +282,12 @@ acpi_evaluate_integer(acpi_handle handle,
 
 	buffer.length = sizeof(union acpi_object);
 	buffer.pointer = &element;
-	status = acpi_evaluate_object(handle, pathname, arguments, &buffer);
+	if (exclusive)
+		status = acpi_evaluate_object_exclusive(handle, pathname,
+							arguments, &buffer);
+	else
+		status = acpi_evaluate_object(handle, pathname, arguments,
+					      &buffer);
 	if (ACPI_FAILURE(status)) {
 		acpi_util_eval_error(handle, pathname, status);
 		return status;
@@ -275,8 +305,24 @@ acpi_evaluate_integer(acpi_handle handle,
 	return AE_OK;
 }
 
+acpi_status
+acpi_evaluate_integer(acpi_handle handle,
+		      acpi_string pathname,
+		      struct acpi_object_list *arguments, unsigned long long *data)
+{
+	return __acpi_evaluate_integer(handle, pathname, arguments, data, false);
+}
 EXPORT_SYMBOL(acpi_evaluate_integer);
 
+acpi_status acpi_evaluate_integer_exclusive(acpi_handle handle,
+					    acpi_string pathname,
+					    struct acpi_object_list *arguments,
+					    unsigned long long *data)
+{
+	return __acpi_evaluate_integer(handle, pathname, arguments, data, true);
+}
+EXPORT_SYMBOL_GPL(acpi_evaluate_integer_exclusive);
+
 int acpi_get_local_u64_address(acpi_handle handle, u64 *addr)
 {
 	acpi_status status;
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index a10a591c18b2..e7a671dba624 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -32,6 +32,14 @@ acpi_status
 acpi_evaluate_integer(acpi_handle handle,
 		      acpi_string pathname,
 		      struct acpi_object_list *arguments, unsigned long long *data);
+acpi_status acpi_evaluate_object_exclusive(acpi_handle handle,
+					   acpi_string pathname,
+					   struct acpi_object_list *arguments,
+					   struct acpi_buffer *buffer);
+acpi_status acpi_evaluate_integer_exclusive(acpi_handle handle,
+					    acpi_string pathname,
+					    struct acpi_object_list *arguments,
+					    unsigned long long *data);
 bool acpi_evaluate_reference(acpi_handle handle, acpi_string pathname,
 			     struct acpi_object_list *arguments,
 			     struct acpi_handle_list *list);

base-commit: 24a19b953e2a3d0ea5a8c4951a0ab8f32720c907
-- 
2.55.0