Re: [PATCH 1/4] ACPI: Provide support for ACPI table adding via OS

H. Peter Anvin
2014-02-18T18:30:37Z

Why can't you add SSDTs? It would be particularly useful.

On February 18, 2014 10:22:40 AM PST, Thomas Renninger <trenn@suse.de> wrote:
>This is done the same way as the previous ACPI physical table override
>mechanism.
>How to override or add tables via initrd, please look up:
>Documentation/acpi/initrd_table_override.txt
>
>SSDTs can only be overridden, not added.
>
>Overriding only happens if the OEM id of the table header matches the
>one
>with the BIOS provided one.
>All table types (SSDTs are an exception), must only show up once.
>So either you:
>- Add a fresh new table for adding of which type (signature) none
>exists
> in the BIOS -> OS ACPI table adding happens.
>or
>- Add a table which already exists in BIOS, but the OEM id must match
>the
>one of the table of the same type (signature) that exists in BIOS
>already
> -> OS ACPI table overriding happens
> Typically one copies away the original ACPI table, disassembles,
> modifies (for example adding debug strings), compiles it and provides
> the table via initrd for overriding (will have the same OEM id).
> But this is not necessary, one could also come up with a selfmade
> table for overriding, by taking care that the signature and OEM id is
> the same as the one provided by BIOS
>
>In ACPI table overriding case you see in dmesg:
> ACPI: Override [DSDT- BXDSDT], this is unsafe: tainting kernel
> Disabling lock debugging due to kernel taint
>
>In ACPI table adding case you see in dmesg (BGRT table got added):
> ACPI: Add [BGRT-SLIC-WKS], this is unsafe: tainting kernel
> ACPI: BGRT 000000007fffd1ba 000038 (v00 HPQOEM SLIC-WKS 01072009
> INTL 20130823)
>
>Signed-off-by: Thomas Renninger <trenn@suse.de>
>CC: hpa@zytor.com
>CC: tglx@linutronix.de
>CC: ck@conrad-kostecki.de
>CC: linux-kernel@vger.kernel.org
>CC: x86@kernel.org
>CC: mingo@redhat.com
>CC: rjw@rjwysocki.net
>CC: devel@acpica.org
>---
>drivers/acpi/osl.c | 89
>+++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 files changed, 88 insertions(+), 1 deletions(-)
>
>diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
>index fc1aa79..07439b4 100644
>--- a/drivers/acpi/osl.c
>+++ b/drivers/acpi/osl.c
>@@ -566,6 +566,8 @@ static const char * const table_sigs[] = {
>
> #define ACPI_OVERRIDE_TABLES 64
>static struct cpio_data __initdata
>acpi_initrd_files[ACPI_OVERRIDE_TABLES];
>+/* Remember physical address of overriden or added tables */
>+static acpi_physical_address
>acpi_table_overridden[ACPI_OVERRIDE_TABLES];
>
> #define MAP_CHUNK_SIZE (NR_FIX_BTMAPS << PAGE_SHIFT)
>
>@@ -715,7 +717,7 @@ acpi_os_physical_table_override(struct
>acpi_table_header *existing_table,
> *address = 0;
> return AE_OK;
> #else
>- int table_offset = 0;
>+ int no, table_offset = 0;
> struct acpi_table_header *table;
>
> *table_length = 0;
>@@ -759,6 +761,12 @@ acpi_os_physical_table_override(struct
>acpi_table_header *existing_table,
> *table_length = table->length;
> acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
> *address = acpi_tables_addr + table_offset;
>+ for (no = 0; no < ACPI_OVERRIDE_TABLES; no++) {
>+ if (acpi_table_overridden[no] == 0) {
>+ acpi_table_overridden[no] = *address;
>+ break;
>+ }
>+ }
> break;
> } while (table_offset + ACPI_HEADER_SIZE < all_tables_size);
>
>@@ -768,6 +776,85 @@ acpi_os_physical_table_override(struct
>acpi_table_header *existing_table,
> #endif
> }
>
>+acpi_status
>+acpi_os_physical_table_add(acpi_physical_address *address,
>+ u32 *table_length)
>+{
>+#ifndef CONFIG_ACPI_INITRD_TABLE_OVERRIDE
>+ *table_length = 0;
>+ *address = 0;
>+ return AE_OK;
>+#else
>+ int no, 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;
>+
>+ /* Do not add SSDTs for now, they might be intended to get
>+ overridden when an SSDT gets loaded dynamically in ACPI
>+ context at any time later */
>+ if (!memcmp("SSDT", table->signature, 4)) {
>+ acpi_os_unmap_memory(table,
>+ ACPI_HEADER_SIZE);
>+ continue;
>+ }
>+
>+ /* Only add tables that have not been overridden already */
>+ for (no = 0; no < ACPI_OVERRIDE_TABLES; no++) {
>+ if (acpi_table_overridden[no] == 0)
>+ break;
>+ if (acpi_table_overridden[no] ==
>+ acpi_tables_addr + table_offset - table->length)
>+ break;
>+ }
>+ /* All tables have been added or overridden */
>+ if (acpi_table_overridden[no] != 0) {
>+ acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
>+ continue;
>+ }
>+ /* Max table override/add limit reached */
>+ if (no == ACPI_OVERRIDE_TABLES) {
>+ acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
>+ return AE_ERROR;
>+ }
>+
>+ table_offset -= table->length;
>+ *table_length = table->length;
>+ *address = acpi_tables_addr + table_offset;
>+ /* do not add this table again */
>+ acpi_table_overridden[no] = *address;
>+ pr_warn(PREFIX
>+ "Add [%4.4s-%8.8s], this is unsafe: tainting kernel\n",
>+ table->signature, table->oem_table_id);
>+ add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
>+ acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
>+ return AE_OK;
>+ } while (table_offset + ACPI_HEADER_SIZE < all_tables_size);
>+ return AE_OK;
>+#endif
>+}
>+
> static irqreturn_t acpi_irq(int irq, void *dev_id)
> {
> u32 handled;

--
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