diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/acpi/initrd_table_override.txt | 111 | ||||
| -rw-r--r-- | Documentation/admin-guide/acpi/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/acpi/initrd_table_override.rst | 115 |
3 files changed, 116 insertions, 111 deletions
diff --git a/Documentation/acpi/initrd_table_override.txt b/Documentation/acpi/initrd_table_override.txt deleted file mode 100644 index 30437a6db373..000000000000 --- a/Documentation/acpi/initrd_table_override.txt +++ /dev/null @@ -1,111 +0,0 @@ -Upgrading ACPI tables via initrd -================================ - -1) Introduction (What is this about) -2) What is this for -3) How does it work -4) References (Where to retrieve userspace tools) - -1) What is this about ---------------------- - -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. - -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. -All ACPI tables iasl (Intel's ACPI compiler and disassembler) knows should -be overridable, except: - - ACPI_SIG_RSDP (has a signature of 6 bytes) - - ACPI_SIG_FACS (does not have an ordinary ACPI table header) -Both could get implemented as well. - - -2) What is this for -------------------- - -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. - -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 -------------------- - -# Extract the machine's ACPI tables: -cd /tmp -acpidump >acpidump -acpixtract -a acpidump -# Disassemble, modify and recompile them: -iasl -d *.dat -# 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. 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 "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 -# 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: -acpi.debug_level=0x2 acpi.debug_layer=0xFFFFFFFF -# and check your syslog: -[ 1.268089] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT] -[ 1.272091] [ACPI Debug] String [0x0B] "HELLO WORLD" - -iasl is able to disassemble and recompile quite a lot different, -also static ACPI tables. - - -4) Where to retrieve userspace tools ------------------------------------- - -iasl and acpixtract are part of Intel's ACPICA project: -http://acpica.org/ -and should be packaged by distributions (for example in the acpica package -on SUSE). - -acpidump can be found in Len Browns pmtools: -ftp://kernel.org/pub/linux/kernel/people/lenb/acpi/utils/pmtools/acpidump -This tool is also part of the acpica package on SUSE. -Alternatively, used ACPI tables can be retrieved via sysfs in latest kernels: -/sys/firmware/acpi/tables diff --git a/Documentation/admin-guide/acpi/index.rst b/Documentation/admin-guide/acpi/index.rst index 3e041206089d..09e4e81e4fb7 100644 --- a/Documentation/admin-guide/acpi/index.rst +++ b/Documentation/admin-guide/acpi/index.rst @@ -8,3 +8,4 @@ the Linux ACPI support. .. toctree:: :maxdepth: 1 + initrd_table_override diff --git a/Documentation/admin-guide/acpi/initrd_table_override.rst b/Documentation/admin-guide/acpi/initrd_table_override.rst new file mode 100644 index 000000000000..cbd768207631 --- /dev/null +++ b/Documentation/admin-guide/acpi/initrd_table_override.rst @@ -0,0 +1,115 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================ +Upgrading ACPI tables via initrd +================================ + +What is this about +================== + +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. + +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. + +All ACPI tables iasl (Intel's ACPI compiler and disassembler) knows should +be overridable, except: + + - ACPI_SIG_RSDP (has a signature of 6 bytes) + - ACPI_SIG_FACS (does not have an ordinary ACPI table header) + +Both could get implemented as well. + + +What is this for +================ + +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. + +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. + + +How does it work +================ +:: + + # Extract the machine's ACPI tables: + cd /tmp + acpidump >acpidump + acpixtract -a acpidump + # Disassemble, modify and recompile them: + iasl -d *.dat + # 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. 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 "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 + # 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: + acpi.debug_level=0x2 acpi.debug_layer=0xFFFFFFFF + # and check your syslog: + [ 1.268089] ACPI: PCI Interrupt Routing Table [\_SB_.PCI0._PRT] + [ 1.272091] [ACPI Debug] String [0x0B] "HELLO WORLD" + +iasl is able to disassemble and recompile quite a lot different, +also static ACPI tables. + + +Where to retrieve userspace tools +================================= + +iasl and acpixtract are part of Intel's ACPICA project: +http://acpica.org/ + +and should be packaged by distributions (for example in the acpica package +on SUSE). + +acpidump can be found in Len Browns pmtools: +ftp://kernel.org/pub/linux/kernel/people/lenb/acpi/utils/pmtools/acpidump + +This tool is also part of the acpica package on SUSE. +Alternatively, used ACPI tables can be retrieved via sysfs in latest kernels: +/sys/firmware/acpi/tables |