4 files changed, 27 insertions, 2 deletions

diff --git a/Documentation/acpi/initrd_table_override.txt b/Documentation/acpi/initrd_table_override.txt
index eb651a6aa285..30437a6db373 100644
--- a/Documentation/acpi/initrd_table_override.txt
+++ b/Documentation/acpi/initrd_table_override.txt
@@ -14,6 +14,10 @@ upgrade the ACPI execution environment that is defined by the ACPI tables
 via upgrading the ACPI tables provided by the BIOS with an instrumented,
 modified, more recent version one, or installing brand new ACPI tables.
 
+When building initrd with kernel in a single image, option
+ACPI_TABLE_OVERRIDE_VIA_BUILTIN_INITRD should also be true for this
+feature to work.
+
 For a full list of ACPI tables that can be upgraded/installed, take a look
 at the char *table_sigs[MAX_ACPI_SIGNATURE]; definition in
 drivers/acpi/tables.c.
diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 90ff0a47c12e..4e015c77e48e 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -357,6 +357,16 @@ config ACPI_TABLE_UPGRADE
           initrd, therefore it's safe to say Y.
           See Documentation/acpi/initrd_table_override.txt for details
 
+config ACPI_TABLE_OVERRIDE_VIA_BUILTIN_INITRD
+        bool "Override ACPI tables from built-in initrd"
+        depends on ACPI_TABLE_UPGRADE
+        depends on INITRAMFS_SOURCE!="" && INITRAMFS_COMPRESSION=""
+        help
+          This option provides functionality to override arbitrary ACPI tables
+          from built-in uncompressed initrd.
+
+          See Documentation/acpi/initrd_table_override.txt for details
+
 config ACPI_DEBUG
         bool "Debug Statements"
         help
diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
index 48eabb6c2d4f..8fccbe49612a 100644
--- a/drivers/acpi/tables.c
+++ b/drivers/acpi/tables.c
@@ -473,14 +473,22 @@ static DECLARE_BITMAP(acpi_initrd_installed, NR_ACPI_INITRD_TABLES);
 
 void __init acpi_table_upgrade(void)
 {
-        void *data = (void *)initrd_start;
-        size_t size = initrd_end - initrd_start;
+        void *data;
+        size_t size;
         int sig, no, table_nr = 0, total_offset = 0;
         long offset = 0;
         struct acpi_table_header *table;
         char cpio_path[32] = "kernel/firmware/acpi/";
         struct cpio_data file;
 
+        if (IS_ENABLED(CONFIG_ACPI_TABLE_OVERRIDE_VIA_BUILTIN_INITRD)) {
+                data = __initramfs_start;
+                size = __initramfs_size;
+        } else {
+                data = (void *)initrd_start;
+                size = initrd_end - initrd_start;
+        }
+
         if (data == NULL || size == 0)
                 return;
 
diff --git a/include/linux/initrd.h b/include/linux/initrd.h
index 14beaff9b445..d77fe34fb00a 100644
--- a/include/linux/initrd.h
+++ b/include/linux/initrd.h
@@ -25,3 +25,6 @@ extern phys_addr_t phys_initrd_start;
 extern unsigned long phys_initrd_size;
 
 extern unsigned int real_root_dev;
+
+extern char __initramfs_start[];
+extern unsigned long __initramfs_size;