Details can be found in:
Documentation/acpi/initrd_table_override.txt
Signed-off-by: Thomas Renninger <trenn@xxxxxxx>
CC: eric.piel@xxxxxxxxxxxxxxxx
CC: vojcek@xxxxxxx
CC: Lin Ming <ming.m.lin@xxxxxxxxx>
CC: lenb@xxxxxxxxxx
CC: robert.moore@xxxxxxxxx
CC: hpa@xxxxxxxxx
CC: yinghai@xxxxxxxxxx
---
Documentation/acpi/initrd_table_override.txt | 122 ++++++++++++++++
arch/x86/kernel/setup.c | 4 +
drivers/acpi/Kconfig | 9 ++
drivers/acpi/osl.c | 200 ++++++++++++++++++++++++--
include/linux/acpi.h | 4 +
5 files changed, 328 insertions(+), 11 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..22222c0
--- /dev/null
+++ b/Documentation/acpi/initrd_table_override.txt
@@ -0,0 +1,122 @@
+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.
+
+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:
+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 /kernel/firmware/acpi/table[0-9].dat files inside the
+# cpio archive. Starting with table0.dat
+# The one uncompressed cpio archive and it 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/table0.dat
+# Add other ACPI tables, the filename's number must increase in order
+# A maximum of ten tables (table9.dat) are allowed:
+iasl -sa FACP.dsl
+iasl -sa SSDT1.dsl
+cp FACP.aml kernel/firmware/acpi/table1.dat
+cp SSDT1.aml kernel/firmware/acpi/table2.dat
+# Create the uncompressed cpio archive and concatenate the orginal 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/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index f4b9b80..6a91058 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -941,6 +941,10 @@ void __init setup_arch(char **cmdline_p)
reserve_initrd();
+#ifdef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
+ acpi_initrd_override((void *)initrd_start, initrd_end - initrd_start);
+#endif
+
reserve_crashkernel();
vsmp_init();
diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 8099895..a508f77 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -261,6 +261,15 @@ config ACPI_CUSTOM_DSDT
bool
default ACPI_CUSTOM_DSDT_FILE != ""
+config ACPI_INITRD_TABLE_OVERRIDE
+ bool
+ default y
+ help
+ This option provides functionality to override arbitrary ACPI tables
+ via initrd. No functional change if no ACPI tables are passed via
+ 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 9eaf708..c549c7d 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -534,6 +534,134 @@ acpi_os_predefined_override(const struct acpi_predefined_names *init_val,
return AE_OK;
}
+#ifdef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
+#include <linux/earlycpio.h>
+#include <linux/memblock.h>
+
+#include <asm/e820.h>
+
+static u64 acpi_tables_addr;
+static int all_tables_size;
+
+/* 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: */
+static const char * const table_sigs[] = {
+ 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, NULL };
+
+/* Non-fatal errors: Affected tables/files are ignored */
+#define INVALID_TABLE(x, name) \
+ { pr_err("ACPI OVERRIDE: " x " [%s]\n", name); continue; }
+
+#define ACPI_HEADER_SIZE sizeof(struct acpi_table_header)
+
+/* Must not increase 10 or needs code modifcation below */
+#define ACPI_OVERRIDE_TABLES 10
+
+void __init acpi_initrd_override(void *data, size_t size)
+{
+ int sig, no, table_nr = 0, offset = 0;
+ struct acpi_table_header *table;
+ char cpio_path[32] = "kernel/firmware/acpi/tableX.dat";
+ struct cpio_data file;
+ struct cpio_data early_initrd_files[ACPI_OVERRIDE_TABLES];
+ char *p;
+
+ if (data == NULL)
+ return;
+
+ for (no = 0; no < ACPI_OVERRIDE_TABLES; no++) {
+ cpio_path[26] = '0' + no;
+ printk(KERN_DEBUG "ACPI override: Trying to find %s\n",
+ cpio_path);
+ file = find_cpio_data(cpio_path, data, size);
+ if (!file.data)
+ break;
+
+ if (file.size < sizeof(struct acpi_table_header))
+ INVALID_TABLE("Table smaller than ACPI header",
+ cpio_path);
+
+ table = file.data;
+
+ for (sig = 0; table_sigs[sig]; sig++)
+ if (!memcmp(table->signature, table_sigs[sig], 4))
+ break;
+
+ if (!table_sigs[sig])
+ INVALID_TABLE("Unknown signature", cpio_path);
+ if (file.size != table->length)
+ INVALID_TABLE("File length does not match table length",
+ cpio_path);
+ if (acpi_table_checksum(file.data, table->length))
+ INVALID_TABLE("Bad table checksum", cpio_path);
+
+ pr_info("%4.4s ACPI table found in initrd [%s][0x%x]\n",
+ table->signature, cpio_path, table->length);
+
+ all_tables_size += table->length;
+ early_initrd_files[table_nr].data = file.data;
+ early_initrd_files[table_nr].size = file.size;
+ table_nr++;
+ }
+ if (table_nr == 0)
+ return;
+
+ acpi_tables_addr =
+ memblock_find_in_range(0, max_low_pfn_mapped << PAGE_SHIFT,
+ all_tables_size, PAGE_SIZE);
+ if (!acpi_tables_addr) {
+ WARN_ON(1);
+ return;
+ }
+ /*
+ * 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_addr, acpi_tables_addr + all_tables_size);
+ e820_add_region(acpi_tables_addr, all_tables_size, E820_ACPI);
+ update_e820();
+ p = early_ioremap(acpi_tables_addr, all_tables_size);
+
+ for (no = 0; no < table_nr; no++) {
+ memcpy(p + offset, early_initrd_files[no].data,
+ early_initrd_files[no].size);
+ offset += early_initrd_files[no].size;
+ }
+ early_iounmap(p, all_tables_size);
+}
+#endif /* CONFIG_ACPI_INITRD_TABLE_OVERRIDE */
+
+static void acpi_table_taint(struct acpi_table_header *table)
+{
+ pr_warn(PREFIX
+ "Override [%4.4s-%8.8s], this is unsafe: tainting kernel\n",
+ table->signature, table->oem_table_id);
+ add_taint(TAINT_OVERRIDDEN_ACPI_TABLE);
+}
+
acpi_status
acpi_os_table_override(struct acpi_table_header * existing_table,
struct acpi_table_header ** new_table)
@@ -547,24 +675,74 @@ acpi_os_table_override(struct acpi_table_header * existing_table,
if (strncmp(existing_table->signature, "DSDT", 4) == 0)
*new_table = (struct acpi_table_header *)AmlCode;
#endif
- if (*new_table != NULL) {
- printk(KERN_WARNING PREFIX "Override [%4.4s-%8.8s], "
- "this is unsafe: tainting kernel\n",
- existing_table->signature,
- existing_table->oem_table_id);
- add_taint(TAINT_OVERRIDDEN_ACPI_TABLE);
- }
+ if (*new_table != NULL)
+ acpi_table_taint(existing_table);
return AE_OK;
}
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;
+#else
+ int table_offset = 0;
+ struct acpi_table_header *table;
+
+ *table_length = 0;
+ *address = 0;
+
+ if (!acpi_tables_addr)
+ return AE_OK;
+
+ do {
+ if (table_offset + ACPI_HEADER_SIZE > all_tables_size) {
+ WARN_ON(1);
+ return AE_OK;
+ }
+
+ table = acpi_os_map_memory(acpi_tables_addr + table_offset,
+ ACPI_HEADER_SIZE);
+ if (table_offset + table->length > all_tables_size) {
+ acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
+ WARN_ON(1);
+ return AE_OK;
+ }
+
+ table_offset += table->length;
+
+ if (memcmp(existing_table->signature, table->signature, 4)) {
+ acpi_os_unmap_memory(table,
+ ACPI_HEADER_SIZE);
+ 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,
+ ACPI_HEADER_SIZE);
+ continue;
+ }
+
+ table_offset -= table->length;
+ *table_length = table->length;
+ acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
+ *address = acpi_tables_addr + table_offset;
+ add_taint(TAINT_OVERRIDDEN_ACPI_TABLE);
+ break;
+ } while (table_offset + ACPI_HEADER_SIZE < all_tables_size);
+
+ if (*address != 0)
+ acpi_table_taint(existing_table);
+ return AE_OK;
+#endif
+}
static irqreturn_t acpi_irq(int irq, void *dev_id)
{
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 4f2a762..87e2c9e 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
+void __init acpi_initrd_override(void *data, size_t size);
+#endif
+
char * __acpi_map_table (unsigned long phys_addr, unsigned long size);
void __acpi_unmap_table(char *map, unsigned long size);
int early_acpi_boot_init(void);
--
1.7.6.1
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