forked from luck/tmp_suning_uos_patched
8347bbecf3
Signed-off-by: Thomas Renninger <trenn@suse.de> Link: http://lkml.kernel.org/r/1349043837-22659-7-git-send-email-trenn@suse.de Cc: Len Brown <lenb@kernel.org> Cc: Robert Moore <robert.moore@intel.com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Eric Piel <eric.piel@tremplin-utc.net> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
95 lines
3.3 KiB
Plaintext
95 lines
3.3 KiB
Plaintext
Overriding 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_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.
|
|
|
|
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
|
|
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
|
|
-------------------
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
|
|
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)
|
|
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.
|
|
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):
|
|
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:
|
|
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
|