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

[H. Peter Anvin]

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

On February 18, 2014 10:22:40 AM PST, Thomas Renninger <trenn@xxxxxxx> 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@xxxxxxx>
>CC: hpa@xxxxxxxxx
>CC: tglx@xxxxxxxxxxxxx
>CC: ck@xxxxxxxxxxxxxxxxxx
>CC: linux-kernel@xxxxxxxxxxxxxxx
>CC: x86@xxxxxxxxxx
>CC: mingo@xxxxxxxxxx
>CC: rjw@xxxxxxxxxxxxx
>CC: devel@xxxxxxxxxx
>---
>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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