[PATCH] efi: make the min and max mmap slack slots configurable

Hamza Mahfooz
2024-12-09T16:25:25Z

Recent platforms require more slack slots than the current value of
EFI_MMAP_NR_SLACK_SLOTS, otherwise they fail to boot. So, introduce
EFI_MIN_NR_MMAP_SLACK_SLOTS and EFI_MAX_NR_MMAP_SLACK_SLOTS
and use them to determine a number of slots that the platform
is willing to accept.

Cc: stable@vger.kernel.org
Cc: Tyler Hicks <code@tyhicks.com>
Tested-by: Brian Nguyen <nguyenbrian@microsoft.com>
Tested-by: Jacob Pan <panj@microsoft.com>
Reviewed-by: Allen Pais <apais@microsoft.com>
Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
---
drivers/firmware/efi/Kconfig | 23 +++++++++++++++++
.../firmware/efi/libstub/efi-stub-helper.c | 2 +-
drivers/firmware/efi/libstub/efistub.h | 15 +----------
drivers/firmware/efi/libstub/kaslr.c | 2 +-
drivers/firmware/efi/libstub/mem.c | 25 +++++++++++++++----
drivers/firmware/efi/libstub/randomalloc.c | 2 +-
drivers/firmware/efi/libstub/relocate.c | 2 +-
drivers/firmware/efi/libstub/x86-stub.c | 8 +++---
8 files changed, 52 insertions(+), 27 deletions(-)

diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index e312d731f4a3..7fedc271d543 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -155,6 +155,29 @@ config EFI_TEST
Say Y here to enable the runtime services support via /dev/efi_test.
If unsure, say N.

+#
+# An efi_boot_memmap is used by efi_get_memory_map() to return the
+# EFI memory map in a dynamically allocated buffer.
+#
+# The buffer allocated for the EFI memory map includes extra room for
+# a range of [EFI_MIN_NR_MMAP_SLACK_SLOTS, EFI_MAX_NR_MMAP_SLACK_SLOTS]
+# additional EFI memory descriptors. This facilitates the reuse of the
+# EFI memory map buffer when a second call to ExitBootServices() is
+# needed because of intervening changes to the EFI memory map. Other
+# related structures, e.g. x86 e820ext, need to factor in this headroom
+# requirement as well.
+#
+
+config EFI_MIN_NR_MMAP_SLACK_SLOTS
+ int
+ depends on EFI
+ default 8
+
+config EFI_MAX_NR_MMAP_SLACK_SLOTS
+ int
+ depends on EFI
+ default 64
+
config EFI_DEV_PATH_PARSER
bool

diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index c0c81ca4237e..adf2b0c0dd34 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -432,7 +432,7 @@ efi_status_t efi_exit_boot_services(void *handle, void *priv,
if (efi_disable_pci_dma)
efi_pci_disable_bridge_busmaster();

- status = efi_get_memory_map(&map, true);
+ status = efi_get_memory_map(&map, true, NULL);
if (status != EFI_SUCCESS)
return status;

diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index 76e44c185f29..d86c6e13de5f 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -160,19 +160,6 @@ void efi_set_u64_split(u64 data, u32 *lo, u32 *hi)
*/
#define EFI_100NSEC_PER_USEC ((u64)10)

-/*
- * An efi_boot_memmap is used by efi_get_memory_map() to return the
- * EFI memory map in a dynamically allocated buffer.
- *
- * The buffer allocated for the EFI memory map includes extra room for
- * a minimum of EFI_MMAP_NR_SLACK_SLOTS additional EFI memory descriptors.
- * This facilitates the reuse of the EFI memory map buffer when a second
- * call to ExitBootServices() is needed because of intervening changes to
- * the EFI memory map. Other related structures, e.g. x86 e820ext, need
- * to factor in this headroom requirement as well.
- */
-#define EFI_MMAP_NR_SLACK_SLOTS 8
-
typedef struct efi_generic_dev_path efi_device_path_protocol_t;

union efi_device_path_to_text_protocol {
@@ -1059,7 +1046,7 @@ void efi_apply_loadoptions_quirk(const void **load_options, u32 *load_options_si
char *efi_convert_cmdline(efi_loaded_image_t *image);

efi_status_t efi_get_memory_map(struct efi_boot_memmap **map,
- bool install_cfg_tbl);
+ bool install_cfg_tbl, unsigned int *n);

efi_status_t efi_allocate_pages(unsigned long size, unsigned long *addr,
unsigned long max);
diff --git a/drivers/firmware/efi/libstub/kaslr.c b/drivers/firmware/efi/libstub/kaslr.c
index 6318c40bda38..06e7a1ef34ab 100644
--- a/drivers/firmware/efi/libstub/kaslr.c
+++ b/drivers/firmware/efi/libstub/kaslr.c
@@ -62,7 +62,7 @@ static bool check_image_region(u64 base, u64 size)
bool ret = false;
int map_offset;

- status = efi_get_memory_map(&map, false);
+ status = efi_get_memory_map(&map, false, NULL);
if (status != EFI_SUCCESS)
return false;

diff --git a/drivers/firmware/efi/libstub/mem.c b/drivers/firmware/efi/libstub/mem.c
index 4f1fa302234d..cab25183b790 100644
--- a/drivers/firmware/efi/libstub/mem.c
+++ b/drivers/firmware/efi/libstub/mem.c
@@ -13,32 +13,47 @@
* configuration table
*
* Retrieve the UEFI memory map. The allocated memory leaves room for
- * up to EFI_MMAP_NR_SLACK_SLOTS additional memory map entries.
+ * up to CONFIG_EFI_MAX_NR_MMAP_SLACK_SLOTS additional memory map entries.
*
* Return: status code
*/
efi_status_t efi_get_memory_map(struct efi_boot_memmap **map,
- bool install_cfg_tbl)
+ bool install_cfg_tbl,
+ unsigned int *n)
{
int memtype = install_cfg_tbl ? EFI_ACPI_RECLAIM_MEMORY
: EFI_LOADER_DATA;
efi_guid_t tbl_guid = LINUX_EFI_BOOT_MEMMAP_GUID;
+ unsigned int nr = CONFIG_EFI_MIN_NR_MMAP_SLACK_SLOTS;
struct efi_boot_memmap *m, tmp;
efi_status_t status;
unsigned long size;

+ BUILD_BUG_ON(!is_power_of_2(CONFIG_EFI_MIN_NR_MMAP_SLACK_SLOTS) ||
+ !is_power_of_2(CONFIG_EFI_MAX_NR_MMAP_SLACK_SLOTS) ||
+ CONFIG_EFI_MIN_NR_MMAP_SLACK_SLOTS >=
+ CONFIG_EFI_MAX_NR_MMAP_SLACK_SLOTS);
+
tmp.map_size = 0;
status = efi_bs_call(get_memory_map, &tmp.map_size, NULL, &tmp.map_key,
&tmp.desc_size, &tmp.desc_ver);
if (status != EFI_BUFFER_TOO_SMALL)
return EFI_LOAD_ERROR;

- size = tmp.map_size + tmp.desc_size * EFI_MMAP_NR_SLACK_SLOTS;
- status = efi_bs_call(allocate_pool, memtype, sizeof(*m) + size,
- (void **)&m);
+ do {
+ size = tmp.map_size + tmp.desc_size * nr;
+ status = efi_bs_call(allocate_pool, memtype, sizeof(*m) + size,
+ (void **)&m);
+ nr <<= 1;
+ } while (status == EFI_BUFFER_TOO_SMALL &&
+ nr <= CONFIG_EFI_MAX_NR_MMAP_SLACK_SLOTS);
+
if (status != EFI_SUCCESS)
return status;

+ if (n)
+ *n = nr;
+
if (install_cfg_tbl) {
/*
* Installing a configuration table might allocate memory, and
diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
index c41e7b2091cd..e80a65e7b87a 100644
--- a/drivers/firmware/efi/libstub/randomalloc.c
+++ b/drivers/firmware/efi/libstub/randomalloc.c
@@ -65,7 +65,7 @@ efi_status_t efi_random_alloc(unsigned long size,
efi_status_t status;
int map_offset;

- status = efi_get_memory_map(&map, false);
+ status = efi_get_memory_map(&map, false, NULL);
if (status != EFI_SUCCESS)
return status;

diff --git a/drivers/firmware/efi/libstub/relocate.c b/drivers/firmware/efi/libstub/relocate.c
index d694bcfa1074..b7b0aad95ba4 100644
--- a/drivers/firmware/efi/libstub/relocate.c
+++ b/drivers/firmware/efi/libstub/relocate.c
@@ -28,7 +28,7 @@ efi_status_t efi_low_alloc_above(unsigned long size, unsigned long align,
unsigned long nr_pages;
int i;

- status = efi_get_memory_map(&map, false);
+ status = efi_get_memory_map(&map, false, NULL);
if (status != EFI_SUCCESS)
goto fail;

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 188c8000d245..cb14f0d2a3d9 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -740,15 +740,15 @@ static efi_status_t allocate_e820(struct boot_params *params,
struct efi_boot_memmap *map;
efi_status_t status;
__u32 nr_desc;
+ __u32 nr;

- status = efi_get_memory_map(&map, false);
+ status = efi_get_memory_map(&map, false, &nr);
if (status != EFI_SUCCESS)
return status;

nr_desc = map->map_size / map->desc_size;
- if (nr_desc > ARRAY_SIZE(params->e820_table) - EFI_MMAP_NR_SLACK_SLOTS) {
- u32 nr_e820ext = nr_desc - ARRAY_SIZE(params->e820_table) +
- EFI_MMAP_NR_SLACK_SLOTS;
+ if (nr_desc > ARRAY_SIZE(params->e820_table) - nr) {
+ u32 nr_e820ext = nr_desc - ARRAY_SIZE(params->e820_table) + nr;

status = alloc_e820ext(nr_e820ext, e820ext, e820ext_size);
}
--
2.47.1