-Overriding ACPI tables via initrd
-=================================
+Upgrading ACPI tables via initrd
+================================
1) Introduction (What is this about)
2) What is this for
1) What is this about
---------------------
-If the ACPI_INITRD_TABLE_OVERRIDE compile option is true, it is possible to
-override nearly any ACPI table provided by the BIOS with an instrumented,
-modified one.
+If the ACPI_TABLE_UPGRADE compile option is true, it is possible to
+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.
-For a full list of ACPI tables that can be overridden, take a look at
-the char *table_sigs[MAX_ACPI_SIGNATURE]; definition in drivers/acpi/osl.c
+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.
All ACPI tables iasl (Intel's ACPI compiler and disassembler) knows should
be overridable, except:
- ACPI_SIG_RSDP (has a signature of 6 bytes)
2) What is this for
-------------------
-Please keep in mind that this is a debug option.
-ACPI tables should not get overridden for productive use.
-If BIOS ACPI tables are overridden the kernel will get tainted with the
-TAINT_OVERRIDDEN_ACPI_TABLE flag.
-Complain to your platform/BIOS vendor if you find a bug which is so sever
-that a workaround is not accepted in the Linux kernel.
+Complain to your platform/BIOS vendor if you find a bug which is so severe
+that a workaround is not accepted in the Linux kernel. And this facility
+allows you to upgrade the buggy tables before your platform/BIOS vendor
+releases an upgraded BIOS binary.
-Still, it can and should be enabled in any kernel, because:
- - There is no functional change with not instrumented initrds
- - It provides a powerful feature to easily debug and test ACPI BIOS table
- compatibility with the Linux kernel.
+This facility can be used by platform/BIOS vendors to provide a Linux
+compatible environment without modifying the underlying platform firmware.
+
+This facility also provides a powerful feature to easily debug and test
+ACPI BIOS table compatibility with the Linux kernel by modifying old
+platform provided ACPI tables or inserting new ACPI tables.
+
+It can and should be enabled in any kernel because there is no functional
+change with not instrumented initrds.
3) How does it work
# For example add this statement into a _PRT (PCI Routing Table) function
# of the DSDT:
Store("HELLO WORLD", debug)
+# And increase the OEM Revision. For example, before modification:
+DefinitionBlock ("DSDT.aml", "DSDT", 2, "INTEL ", "TEMPLATE", 0x00000000)
+# After modification:
+DefinitionBlock ("DSDT.aml", "DSDT", 2, "INTEL ", "TEMPLATE", 0x00000001)
iasl -sa dsdt.dsl
# Add the raw ACPI tables to an uncompressed cpio archive.
-# They must be put into a /kernel/firmware/acpi directory inside the
-# cpio archive.
-# The uncompressed cpio archive must be the first.
-# Other, typically compressed cpio archives, must be
-# concatenated on top of the uncompressed one.
+# They must be put into a /kernel/firmware/acpi directory inside the cpio
+# archive. Note that if the table put here matches a platform table
+# (similar Table Signature, and similar OEMID, and similar OEM Table ID)
+# with a more recent OEM Revision, the platform table will be upgraded by
+# this table. If the table put here doesn't match a platform table
+# (dissimilar Table Signature, or dissimilar OEMID, or dissimilar OEM Table
+# ID), this table will be appended.
mkdir -p kernel/firmware/acpi
cp dsdt.aml kernel/firmware/acpi
-# A maximum of: #define ACPI_OVERRIDE_TABLES 10
-# tables are currently allowed (see osl.c):
+# A maximum of "NR_ACPI_INITRD_TABLES (64)" tables are currently allowed
+# (see osl.c):
iasl -sa facp.dsl
iasl -sa ssdt1.dsl
cp facp.aml kernel/firmware/acpi
cp ssdt1.aml kernel/firmware/acpi
-# Create the uncompressed cpio archive and concatenate the original initrd
-# on top:
+# The uncompressed cpio archive must be the first. Other, typically
+# compressed cpio archives, must be concatenated on top of the uncompressed
+# one. Following command creates the uncompressed cpio archive and
+# concatenates the original initrd on top:
find kernel | cpio -H newc --create > /boot/instrumented_initrd
cat /boot/initrd >>/boot/instrumented_initrd
# reboot with increased acpi debug level, e.g. boot params:
add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
}
-#ifdef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
+#ifdef CONFIG_ACPI_TABLE_UPGRADE
static u64 acpi_tables_addr;
static int all_tables_size;
#define ACPI_HEADER_SIZE sizeof(struct acpi_table_header)
-#define ACPI_OVERRIDE_TABLES 64
-static struct cpio_data __initdata acpi_initrd_files[ACPI_OVERRIDE_TABLES];
-static DECLARE_BITMAP(acpi_initrd_installed, ACPI_OVERRIDE_TABLES);
+#define NR_ACPI_INITRD_TABLES 64
+static struct cpio_data __initdata acpi_initrd_files[NR_ACPI_INITRD_TABLES];
+static DECLARE_BITMAP(acpi_initrd_installed, NR_ACPI_INITRD_TABLES);
#define MAP_CHUNK_SIZE (NR_FIX_BTMAPS << PAGE_SHIFT)
if (data == NULL || size == 0)
return;
- for (no = 0; no < ACPI_OVERRIDE_TABLES; no++) {
+ for (no = 0; no < NR_ACPI_INITRD_TABLES; no++) {
file = find_cpio_data(cpio_path, data, size, &offset);
if (!file.data)
break;
table_length = table->length;
/* Only override tables matched */
- if (test_bit(table_index, acpi_initrd_installed) ||
- memcmp(existing_table->signature, table->signature, 4) ||
+ if (memcmp(existing_table->signature, table->signature, 4) ||
+ memcmp(table->oem_id, existing_table->oem_id,
+ ACPI_OEM_ID_SIZE) ||
memcmp(table->oem_table_id, existing_table->oem_table_id,
ACPI_OEM_TABLE_ID_SIZE)) {
acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
goto next_table;
}
+ /*
+ * Mark the table to avoid being used in
+ * acpi_table_initrd_scan() and check the revision.
+ */
+ if (test_and_set_bit(table_index, acpi_initrd_installed) ||
+ existing_table->oem_revision >= table->oem_revision) {
+ acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
+ goto next_table;
+ }
*length = table_length;
*address = acpi_tables_addr + table_offset;
- acpi_table_taint(existing_table);
+ pr_info("Table Upgrade: override [%4.4s-%6.6s-%8.8s]\n",
+ table->signature, table->oem_id,
+ table->oem_table_id);
acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
- set_bit(table_index, acpi_initrd_installed);
break;
next_table:
table_length = table->length;
/* Skip RSDT/XSDT which should only be used for override */
- if (test_bit(table_index, acpi_initrd_installed) ||
- ACPI_COMPARE_NAME(table->signature, ACPI_SIG_RSDT) ||
+ if (ACPI_COMPARE_NAME(table->signature, ACPI_SIG_RSDT) ||
ACPI_COMPARE_NAME(table->signature, ACPI_SIG_XSDT)) {
acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
goto next_table;
}
+ /*
+ * Mark the table to avoid being used in
+ * acpi_table_initrd_override(). Though this is not possible
+ * because override is disabled in acpi_install_table().
+ */
+ if (test_and_set_bit(table_index, acpi_initrd_installed)) {
+ acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
+ goto next_table;
+ }
- acpi_table_taint(table);
+ pr_info("Table Upgrade: install [%4.4s-%6.6s-%8.8s]\n",
+ table->signature, table->oem_id,
+ table->oem_table_id);
acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
acpi_install_table(acpi_tables_addr + table_offset, TRUE);
- set_bit(table_index, acpi_initrd_installed);
next_table:
table_offset += table_length;
table_index++;
static void __init acpi_table_initrd_scan(void)
{
}
-#endif /* CONFIG_ACPI_INITRD_TABLE_OVERRIDE */
+#endif /* CONFIG_ACPI_TABLE_UPGRADE */
acpi_status
acpi_os_physical_table_override(struct acpi_table_header *existing_table,
projects / GitHub / moto-9609 / android_kernel_motorola_exynos9610.git / commitdiff