ACPI, APEI, EINJ, Refine the fix of resource conflict

Current fix for resource conflict is to remove the address region <param1 &
param2, ~param2+1> from trigger resource, which is highly relies on valid user
input. This patch is trying to avoid such potential issues by fetching the
exact address region from trigger action table entry.

Signed-off-by: Xiao, Hui <[e-mail]>
Signed-off-by: Huang Ying <[e-mail]>
Signed-off-by: Len Brown <[e-mail]>

drivers/acpi/apei/einj.c

···
 	return 0;
 }
 
+static struct acpi_generic_address *einj_get_trigger_parameter_region(
+	struct acpi_einj_trigger *trigger_tab, u64 param1, u64 param2)
+{
+	int i;
+	struct acpi_whea_header *entry;
+
+	entry = (struct acpi_whea_header *)
+		((char *)trigger_tab + sizeof(struct acpi_einj_trigger));
+	for (i = 0; i < trigger_tab->entry_count; i++) {
+		if (entry->action == ACPI_EINJ_TRIGGER_ERROR &&
+		entry->instruction == ACPI_EINJ_WRITE_REGISTER_VALUE &&
+		entry->register_region.space_id ==
+			ACPI_ADR_SPACE_SYSTEM_MEMORY &&
+		(entry->register_region.address & param2) == (param1 & param2))
+			return &entry->register_region;
+		entry++;
+	}
+
+	return NULL;
+}
 /* Execute instructions in trigger error action table */
 static int __einj_error_trigger(u64 trigger_paddr, u32 type,
 				u64 param1, u64 param2)
···
 	struct resource *r;
 	u32 table_size;
 	int rc = -EIO;
+	struct acpi_generic_address *trigger_param_region = NULL;
 
 	r = request_mem_region(trigger_paddr, sizeof(*trigger_tab),
 			       "APEI EINJ Trigger Table");
···
 	if (param_extension && (type & 0x0038) && param2) {
 		struct apei_resources addr_resources;
 		apei_resources_init(&addr_resources);
-		rc = apei_resources_add(&addr_resources,
-					param1 & param2,
-					~param2 + 1, true);
-		if (rc)
-			goto out_fini;
-		rc = apei_resources_sub(&trigger_resources, &addr_resources);
+		trigger_param_region = einj_get_trigger_parameter_region(
+			trigger_tab, param1, param2);
+		if (trigger_param_region) {
+			rc = apei_resources_add(&addr_resources,
+				trigger_param_region->address,
+				trigger_param_region->bit_width/8, true);
+			if (rc)
+				goto out_fini;
+			rc = apei_resources_sub(&trigger_resources,
+					&addr_resources);
+		}
 		apei_resources_fini(&addr_resources);
 		if (rc)
 			goto out_fini;