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ACPICA: Do not touch VGA memory when EBDA < 1ki_b

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ACPICA commit a36eda9631e84f271319c41288889dd5b1329369

The ACPICA code assumes that EBDA region must be at least 1ki_b in size.
Because this is not guaranteed, it might happen that while scanning the
memory for RSDP pointer, the kernel touches memory above 640ki_b.

This is unwanted as the VGA memory range may not be decoded or
even present when running under virtualization.

Link: https://github.com/acpica/acpica/commit/a36eda96
Signed-off-by: Vit Kabele <vit@kabele.me>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Vit Kabele 2022-10-27 19:50:59 +02:00 committed by Rafael J. Wysocki
parent 4fe54f5093
commit 8ff2906513
1 changed files with 15 additions and 7 deletions
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22
drivers/acpi/acpica/tbxfroot.c
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@ -114,6 +114,7 @@ acpi_find_root_pointer(acpi_physical_address *table_address)
u8 *table_ptr;
u8 *mem_rover;
u32 physical_address;
u32 ebda_window_size;
ACPI_FUNCTION_TRACE(acpi_find_root_pointer);
@ -145,24 +146,31 @@ acpi_find_root_pointer(acpi_physical_address *table_address)
*/
if (physical_address > 0x400 && physical_address < 0xA0000) {
/*
* 1b) Search EBDA paragraphs (EBDA is required to be a
* minimum of 1K length)
* Calculate the scan window size
* The EBDA is not guaranteed to be larger than a ki_b and in case
* that it is smaller, the scanning function would leave the low
* memory and continue to the VGA range.
*/
ebda_window_size = ACPI_MIN(ACPI_EBDA_WINDOW_SIZE,
0xA0000 - physical_address);
/*
* 1b) Search EBDA paragraphs
*/
table_ptr = acpi_os_map_memory((acpi_physical_address)
physical_address,
ACPI_EBDA_WINDOW_SIZE);
ebda_window_size);
if (!table_ptr) {
ACPI_ERROR((AE_INFO,
"Could not map memory at 0x%8.8X for length %u",
physical_address, ACPI_EBDA_WINDOW_SIZE));
physical_address, ebda_window_size));
return_ACPI_STATUS(AE_NO_MEMORY);
}
mem_rover =
acpi_tb_scan_memory_for_rsdp(table_ptr,
ACPI_EBDA_WINDOW_SIZE);
acpi_os_unmap_memory(table_ptr, ACPI_EBDA_WINDOW_SIZE);
acpi_tb_scan_memory_for_rsdp(table_ptr, ebda_window_size);
acpi_os_unmap_memory(table_ptr, ebda_window_size);
if (mem_rover) {