Re: [PATCH] ACPI: Implement overriding of arbitrary ACPI tables via initrd

From: Yinghai Lu
Date: Fri Mar 23 2012 - 16:54:17 EST

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On Fri, Mar 23, 2012 at 7:29 AM, Thomas Renninger <trenn@xxxxxxx> wrote:
> Details can be found in:
> Documentation/acpi/initrd_table_override.txt
>
> Additional dmesg output of a booted system with
> FACP (FADT), DSDT and SSDT (the 9th dynamically loaded one)
> tables overridden (with ### marked comments):
>
> ### ACPI tables found glued to initrd
> DSDT ACPI table found in initrd - size: 16234
> FACP ACPI table found in initrd - size: 116
> SSDT ACPI table found in initrd - size: 334
> ### Re-printed e820 map via e820_update() with additionally created
> ### ACPI data section at 0xcff55000 where the ACPI tables passed via
> ### initrd where copied to
> modified physical RAM map:
> ...
> ### New ACPI data section:
> modified: 00000000cff55000 - 00000000cff5912c (ACPI data)
> ### BIOS e820 provided ACPI data section:
> modified: 00000000cff60000 - 00000000cff69000 (ACPI data)
> ...
> ### Total size of all ACPI tables glued to initrd
> ### The address is initrd_start which gets updated to
> ### initrd_start = initrd_start + "size of all ACPI tables glued to initrd"
> Found acpi tables of size: 16684 at 0xffff8800374c4000
>
> Disabling lock debugging due to kernel taint
> ### initrd provided FACP and DSDT tables are used instead of BIOS provided ones
> ACPI: FACP @ 0x00000000cff68dd8 Phys table override, replaced with:
> ACPI: FACP 00000000cff58f6a 00074 (v01 INTEL TUMWATER 06040000 PTL 00000003)
> ACPI: DSDT @ 0x00000000cff649d4 Phys table override, replaced with:
> ACPI: DSDT 00000000cff55000 04404 (v01 Intel BLAKFORD 06040000 MSFT 0100000E)
> ...
> ### Much later, the 9th (/sys/firmware/acpi/table/dynamic/SSDT9) dynamically
> ### loaded ACPI table matches and gets overridden:
> ACPI: SSDT @ 0x00000000cff64824 Phys table override, replaced with:
> ACPI: SSDT 00000000cff58fde 0014E (v01 PmRef Cpu7Ist 00003000 INTL 20110316)
> ACPI: Dynamic OEM Table Load:
> ACPI: SSDT (null) 0014E (v01 PmRef Cpu7Ist 00003000 INTL 20110316)
> ...
>
> If the initrd does not start with a valid ACPI table signature or the ACPI
> table's checksum is wrong, there is no functional change.

great. that is very good feature for development and debug.

will not need to ask for testbios ...

>
> Signed-off-by: Thomas Renninger <trenn@xxxxxxx>
> CC: linux-acpi@xxxxxxxxxxxxxxx
> CC: linux-kernel@xxxxxxxxxxxxxxx
> CC: x86@xxxxxxxxxx
> CC: Lin Ming <ming.m.lin@xxxxxxxxx>
> CC: lenb@xxxxxxxxxx
> CC: robert.moore@xxxxxxxxx
> CC: hpa@xxxxxxxxx
> ---
> Documentation/acpi/initrd_table_override.txt | 110 +++++++++++++++++++
> arch/x86/kernel/setup.c | 18 ++-
> arch/x86/mm/init.c | 6 +
> drivers/acpi/Kconfig | 10 ++
> drivers/acpi/osl.c | 152 +++++++++++++++++++++++++-
> include/linux/acpi.h | 4 +
> include/linux/initrd.h | 3 +
> 7 files changed, 294 insertions(+), 9 deletions(-)
> create mode 100644 Documentation/acpi/initrd_table_override.txt
>
> diff --git a/Documentation/acpi/initrd_table_override.txt b/Documentation/acpi/initrd_table_override.txt
> new file mode 100644
> index 0000000..7b29d5f
> --- /dev/null
> +++ b/Documentation/acpi/initrd_table_override.txt
> @@ -0,0 +1,110 @@
> +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 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.
> +
> +Up to 10 arbitrary ACPI tables can be passed.
> +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 that sever
> +that a workaround is not accepted in the Linus 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.
> +
> +Until now it was only possible to override the DSDT by compiling it into
> +the kernel. This is a nightmare when trying to work on ACPI related bugs
> +and a lot bugs got stuck because of that.
> +Even for people with enough kernel knowledge, building a kernel to try out
> +things is very time consuming. Also people may have to browse and modify the
> +ACPI interpreter code to find a possible BIOS bug. With this feature, people
> +can correct the ACPI tables and try out quickly whether this is the root cause
> +that needs to get addressed in the kernel.
> +
> +This could even ease up testing for BIOS providers who could flush their BIOS
> +to test, but overriding table via initrd is much easier and quicker.
> +For example one could prepare different initrds overriding NUMA tables with
> +different affinity settings. Set up a script, let the machine reboot and
> +run tests over night and one can get a picture how these settings influence
> +the Linux kernel and which values are best.
> +
> +People can instrument the dynamic ACPI (ASL) code (for example with debug
> +statements showing up in syslog when the ACPI code is processed, etc.),
> +to better understand BIOS to OS interfaces, to hunt down ACPI BIOS code related
> +bugs quickly or to easier develop ACPI based drivers.
> +
> +Intstrumenting ACPI code in SSDTs is now much easier. Before, one had to copy
> +all SSDTs into the DSDT to compile it into the kernel for testing
> +(because only DSDT could get overridden). That's what the acpi_no_auto_ssdt
> +boot param is for: the BIOS provided SSDTs are ignored and all have to get
> +copied into the DSDT, complicated and time consuming.
> +
> +Much more use cases, depending on which ACPI parts you are working on...
> +
> +
> +3) How does it work
> +-------------------
> +
> +# Extract the machine's ACPI tables:
> +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 *.dsl
> +# glue them together with the initrd. ACPI tables go first, original initrd
> +# goes on top:
> +cat TBL1.dat >>instrumented_initrd
> +cat TBL2.dat >>instrumented_initrd
> +cat TBL3.dat >>instrumented_initrd
> +cat /boot/initrd >>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/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index d7d5099..5a5a33f 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -412,12 +412,20 @@ static void __init reserve_initrd(void)
> */
> initrd_start = ramdisk_image + PAGE_OFFSET;
> initrd_end = initrd_start + ramdisk_size;
> - return;
> + } else {
> + relocate_initrd();
> + memblock_free(ramdisk_image, ramdisk_end - ramdisk_image);
> }
> -
> - relocate_initrd();
> -
> - memblock_free(ramdisk_image, ramdisk_end - ramdisk_image);
> +#ifdef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
> + acpi_initrd_offset = acpi_initrd_table_override((void *)initrd_start,
> + (void *)initrd_end);
> + if (!acpi_initrd_offset)
> + return;
> + printk(KERN_INFO "Found acpi tables of size: %lu at 0x%lx\n",
> + acpi_initrd_offset, initrd_start);
> + initrd_start += acpi_initrd_offset;
> + return;
> +#endif
> }
> #else
> static void __init reserve_initrd(void)
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index 6cabf65..8df3fda 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -391,6 +391,12 @@ void free_initrd_mem(unsigned long start, unsigned long end)
> * - relocate_initrd()
> * So here We can do PAGE_ALIGN() safely to get partial page to be freed
> */
> +#ifdef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
> + if (acpi_initrd_offset)
> + free_init_pages("initrd memory", start - acpi_initrd_offset,
> + PAGE_ALIGN(end));
> + else
> +#endif

table already get copied to allocated ram, So you don't need to keep
the portion in initrd range.

> free_init_pages("initrd memory", start, PAGE_ALIGN(end));
> }
> #endif
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index 7556913..7113327 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -261,6 +261,16 @@ config ACPI_CUSTOM_DSDT
> bool
> default ACPI_CUSTOM_DSDT_FILE != ""
>
> +config ACPI_INITRD_TABLE_OVERRIDE
> + bool
> + depends on X86
> + default y
> + help
> + This option provides functionality to override arbitrary ACPI tables
> + via initrd. No functional change if no ACPI tables are glued to the
> + initrd, therefore it's safe to say Y.
> + See Documentation/acpi/initrd_table_override.txt for details
> +
> config ACPI_BLACKLIST_YEAR
> int "Disable ACPI for systems before Jan 1st this year" if X86_32
> default 0
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index ad92131..a78b6f6 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -45,6 +45,7 @@
> #include <linux/list.h>
> #include <linux/jiffies.h>
> #include <linux/semaphore.h>
> +#include <linux/memblock.h>
>
> #include <asm/io.h>
> #include <asm/uaccess.h>
> @@ -534,6 +535,107 @@ acpi_os_predefined_override(const struct acpi_predefined_names *init_val,
> return AE_OK;
> }
>
> +#ifdef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
> +#include <asm/e820.h>
> +
> +#define ACPI_OVERRIDE_TABLES 10
> +
> +static unsigned long acpi_table_override_offset[ACPI_OVERRIDE_TABLES];
> +static u64 acpi_tables_inram;
> +
> +unsigned long acpi_initrd_offset;
> +
> +/* Copied from acpica/tbutils.c:acpi_tb_checksum() */
> +u8 __init acpi_table_checksum(u8 *buffer, u32 length)
> +{
> + u8 sum = 0;
> + u8 *end = buffer + length;
> +
> + while (buffer < end)
> + sum = (u8) (sum + *(buffer++));
> + return sum;
> +}
> +
> +/* All but ACPI_SIG_RSDP and ACPI_SIG_FACS: */
> +#define MAX_ACPI_SIGNATURE 35
> +static const char *table_sigs[MAX_ACPI_SIGNATURE] = {
> + ACPI_SIG_BERT, ACPI_SIG_CPEP, ACPI_SIG_ECDT, ACPI_SIG_EINJ,
> + ACPI_SIG_ERST, ACPI_SIG_HEST, ACPI_SIG_MADT, ACPI_SIG_MSCT,
> + ACPI_SIG_SBST, ACPI_SIG_SLIT, ACPI_SIG_SRAT, ACPI_SIG_ASF,
> + ACPI_SIG_BOOT, ACPI_SIG_DBGP, ACPI_SIG_DMAR, ACPI_SIG_HPET,
> + ACPI_SIG_IBFT, ACPI_SIG_IVRS, ACPI_SIG_MCFG, ACPI_SIG_MCHI,
> + ACPI_SIG_SLIC, ACPI_SIG_SPCR, ACPI_SIG_SPMI, ACPI_SIG_TCPA,
> + ACPI_SIG_UEFI, ACPI_SIG_WAET, ACPI_SIG_WDAT, ACPI_SIG_WDDT,
> + ACPI_SIG_WDRT, ACPI_SIG_DSDT, ACPI_SIG_FADT, ACPI_SIG_PSDT,
> + ACPI_SIG_RSDT, ACPI_SIG_XSDT, ACPI_SIG_SSDT };
> +
> +int __init acpi_initrd_table_override(void *start_addr, void *end_addr)
> +{
> + int table_nr, sig;
> + unsigned long offset = 0, max_len = end_addr - start_addr;
> + char *p;
> +
> + for (table_nr = 0; table_nr < ACPI_OVERRIDE_TABLES; table_nr++) {
> + struct acpi_table_header *table;
> + if (max_len < offset + sizeof(struct acpi_table_header)) {
> + WARN_ON(1);
> + return 0;
> + }
> + table = start_addr + offset;
> +
> + for (sig = 0; sig < MAX_ACPI_SIGNATURE; sig++)
> + if (!memcmp(table->signature, table_sigs[sig], 4))
> + break;
> +
> + if (sig >= MAX_ACPI_SIGNATURE)
> + break;
> +
> + if (max_len < offset + table->length) {
> + WARN_ON(1);
> + return 0;
> + }
> +
> + if (acpi_table_checksum(start_addr + offset, table->length)) {
> + WARN(1, "%4.4s has invalid checksum\n",
> + table->signature);
> + continue;
> + }
> + printk(KERN_INFO "%4.4s ACPI table found in initrd"
> + " - size: %d\n", table->signature, table->length);
> +
> + offset += table->length;
> + acpi_table_override_offset[table_nr] = offset;
> + }
> + if (!offset)
> + return 0;
> +
> + acpi_tables_inram =
> + memblock_find_in_range(0, max_low_pfn_mapped << PAGE_SHIFT,
> + offset, PAGE_SIZE);

please don't use max_low_pfn_mapped. that will leave another blocker
to allocate kdump block with 512M.

could use max_low_pfn, and use io_remap to access it for copying purpose.

> + if (!acpi_tables_inram)
> + panic("Cannot find place for ACPI override tables\n");
> +
> + /*
> + * Only calling e820_add_reserve does not work and the
> + * tables are invalid (memory got used) later.
> + * memblock_x86_reserve_range works as expected and the tables
> + * won't get modified. But it's not enough because ioremap will
> + * complain later (used by acpi_os_map_memory) that the pages
> + * that should get mapped are not marked "reserved".
> + * Both memblock_x86_reserve_range and e820_add_region works fine.
> + */
> + memblock_reserve(acpi_tables_inram, acpi_tables_inram + offset);
> + e820_add_region(acpi_tables_inram, offset, E820_ACPI);
> + update_e820();

could use __weak function to avoid use e820 related calling here in osl.c

> +
> + p = early_ioremap(acpi_tables_inram, offset);
> + memcpy(p, start_addr, offset);
> + early_iounmap(p, offset);
> + return offset;
> +}
> +
> +#endif
> +
> acpi_status
> acpi_os_table_override(struct acpi_table_header * existing_table,
> struct acpi_table_header ** new_table)
> @@ -559,12 +661,54 @@ acpi_os_table_override(struct acpi_table_header * existing_table,
>
> acpi_status
> acpi_os_physical_table_override(struct acpi_table_header *existing_table,
> - acpi_physical_address * new_address,
> - u32 *new_table_length)
> + acpi_physical_address *address,
> + u32 *table_length)
> {
> - return AE_SUPPORT;
> -}
> +#ifndef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
> + *table_length = 0;
> + *address = 0;
> + return AE_OK;
> +#endif
> +
> + int table_nr = 0;
> + *table_length = 0;
> + *address = 0;
> + for (; table_nr < ACPI_OVERRIDE_TABLES &&
> + acpi_table_override_offset[table_nr]; table_nr++) {
> + int table_offset;
> + int table_len;
> + struct acpi_table_header *table;
> +
> + if (table_nr == 0)
> + table_offset = 0;
> + else
> + table_offset = acpi_table_override_offset[table_nr - 1];
>
> + table_len = acpi_table_override_offset[table_nr] - table_offset;
> +
> + table = acpi_os_map_memory(acpi_tables_inram + table_offset,
> + table_len);
> +

maybe could have dmi checking for more strict checking.

also would help if have one boot command that could skip overriding.

> + if (memcmp(existing_table->signature, table->signature, 4)) {
> + acpi_os_unmap_memory(table, table_len);
> + continue;
> + }
> +
> + /* Only override tables with matching oem id */
> + if (memcmp(table->oem_table_id, existing_table->oem_table_id,
> + ACPI_OEM_TABLE_ID_SIZE)) {
> + acpi_os_unmap_memory(table, table_len);
> + continue;
> + }
> +
> + acpi_os_unmap_memory(table, table_len);
> + *address = acpi_tables_inram + table_offset;
> + *table_length = table_len;
> + add_taint(TAINT_OVERRIDDEN_ACPI_TABLE);
> + break;
> + }
> + return AE_OK;
> +}
>
> static irqreturn_t acpi_irq(int irq, void *dev_id)
> {
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 104eda7..12bda6a 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -76,6 +76,10 @@ typedef int (*acpi_table_handler) (struct acpi_table_header *table);
>
> typedef int (*acpi_table_entry_handler) (struct acpi_subtable_header *header, const unsigned long end);
>
> +#ifdef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
> +int __init acpi_initrd_table_override(void *start_addr, void *end_addr);

> +#endif

if you have
#else
static inline int __init acpi_initrd_table_override(void *start_addr,
void *end_addr) { return 0 }
#endif

here, you can avoid one #ifdef in .c

Thanks

Yinghai
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Next message: Greg KH: "Linux 3.0.26"
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