platform/x86/amd/pmf: Add capability to sideload of policy binary

A policy binary is OS agnostic, and the same policies are expected to work
across the OSes.  At times it becomes difficult to debug when the policies
inside the policy binaries starts to misbehave. Add a way to sideload such
policies independently to debug them via a debugfs entry.

Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Link: https://lore.kernel.org/r/20231212014705.2017474-12-Shyam-sundar.S-k@amd.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/amd/pmf/pmf.h

@@ -219,6 +219,7 @@ struct amd_pmf_dev {
 	bool cnqf_supported;
 	struct notifier_block pwr_src_notifier;
 	/* Smart PC solution builder */
+	struct dentry *esbin;
 	unsigned char *policy_buf;
 	u32 policy_sz;
 	struct tee_context *tee_ctx;

drivers/platform/x86/amd/pmf/tee-if.c

@@ -8,6 +8,7 @@
  * Author: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
  */
 
+#include <linux/debugfs.h>
 #include <linux/tee_drv.h>
 #include <linux/uuid.h>
 #include "pmf.h"
@@ -16,9 +17,14 @@
 
 /* Policy binary actions sampling frequency (in ms) */
 static int pb_actions_ms = MSEC_PER_SEC;
+/* Sideload policy binaries to debug policy failures */
+static bool pb_side_load;
+
 #ifdef CONFIG_AMD_PMF_DEBUG
 module_param(pb_actions_ms, int, 0644);
 MODULE_PARM_DESC(pb_actions_ms, "Policy binary actions sampling frequency (default = 1000ms)");
+module_param(pb_side_load, bool, 0444);
+MODULE_PARM_DESC(pb_side_load, "Sideload policy binaries debug policy failures");
 #endif
 
 static const uuid_t amd_pmf_ta_uuid = UUID_INIT(0x6fd93b77, 0x3fb8, 0x524d,
@@ -269,6 +275,57 @@ static int amd_pmf_start_policy_engine(struct amd_pmf_dev *dev)
 	return 0;
 }
 
+#ifdef CONFIG_AMD_PMF_DEBUG
+static ssize_t amd_pmf_get_pb_data(struct file *filp, const char __user *buf,
+				   size_t length, loff_t *pos)
+{
+	struct amd_pmf_dev *dev = filp->private_data;
+	unsigned char *new_policy_buf;
+	int ret;
+
+	/* Policy binary size cannot exceed POLICY_BUF_MAX_SZ */
+	if (length > POLICY_BUF_MAX_SZ || length == 0)
+		return -EINVAL;
+
+	/* re-alloc to the new buffer length of the policy binary */
+	new_policy_buf = kzalloc(length, GFP_KERNEL);
+	if (!new_policy_buf)
+		return -ENOMEM;
+
+	if (copy_from_user(new_policy_buf, buf, length))
+		return -EFAULT;
+
+	kfree(dev->policy_buf);
+	dev->policy_buf = new_policy_buf;
+	dev->policy_sz = length;
+
+	ret = amd_pmf_start_policy_engine(dev);
+	if (ret)
+		return -EINVAL;
+
+	return length;
+}
+
+static const struct file_operations pb_fops = {
+	.write = amd_pmf_get_pb_data,
+	.open = simple_open,
+};
+
+static void amd_pmf_open_pb(struct amd_pmf_dev *dev, struct dentry *debugfs_root)
+{
+	dev->esbin = debugfs_create_dir("pb", debugfs_root);
+	debugfs_create_file("update_policy", 0644, dev->esbin, dev, &pb_fops);
+}
+
+static void amd_pmf_remove_pb(struct amd_pmf_dev *dev)
+{
+	debugfs_remove_recursive(dev->esbin);
+}
+#else
+static void amd_pmf_open_pb(struct amd_pmf_dev *dev, struct dentry *debugfs_root) {}
+static void amd_pmf_remove_pb(struct amd_pmf_dev *dev) {}
+#endif
+
 static int amd_pmf_get_bios_buffer(struct amd_pmf_dev *dev)
 {
 	dev->policy_buf = kzalloc(dev->policy_sz, GFP_KERNEL);
@@ -281,6 +338,9 @@ static int amd_pmf_get_bios_buffer(struct amd_pmf_dev *dev)
 
 	memcpy(dev->policy_buf, dev->policy_base, dev->policy_sz);
 
+	if (pb_side_load)
+		amd_pmf_open_pb(dev, dev->dbgfs_dir);
+
 	return amd_pmf_start_policy_engine(dev);
 }
 
@@ -393,6 +453,9 @@ int amd_pmf_init_smart_pc(struct amd_pmf_dev *dev)
 
 void amd_pmf_deinit_smart_pc(struct amd_pmf_dev *dev)
 {
+	if (pb_side_load)
+		amd_pmf_remove_pb(dev);
+
 	kfree(dev->prev_data);
 	kfree(dev->policy_buf);
 	cancel_delayed_work_sync(&dev->pb_work);