From fd62619598069c974739476d1851a00d665041d7 Mon Sep 17 00:00:00 2001 From: Lenny Szubowicz Date: Thu, 7 May 2020 14:33:32 -0400 Subject: [PATCH] efi/libstub/x86: Avoid EFI map buffer alloc in allocate_e820() In allocate_e820(), call the EFI get_memory_map() service directly instead of indirectly via efi_get_memory_map(). This avoids allocation of a buffer and return of the full EFI memory map, which is not needed here and would otherwise need to be freed. Routine allocate_e820() only needs to know how many EFI memory descriptors there are in the map to allocate an adequately sized e820ext buffer, if it's needed. Note that since efi_get_memory_map() returns a memory map buffer sized with extra headroom, allocate_e820() now needs to explicitly factor that into the e820ext size calculation. Signed-off-by: Lenny Szubowicz Suggested-by: Ard Biesheuvel Signed-off-by: Ard Biesheuvel --- drivers/firmware/efi/libstub/efistub.h | 13 +++++++++++++ drivers/firmware/efi/libstub/mem.c | 2 -- drivers/firmware/efi/libstub/x86-stub.c | 24 +++++++++--------------- 3 files changed, 22 insertions(+), 17 deletions(-) diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h index 67d2694..6294399 100644 --- a/drivers/firmware/efi/libstub/efistub.h +++ b/drivers/firmware/efi/libstub/efistub.h @@ -92,6 +92,19 @@ extern __pure efi_system_table_t *efi_system_table(void); #define EFI_LOCATE_BY_REGISTER_NOTIFY 1 #define EFI_LOCATE_BY_PROTOCOL 2 +/* + * 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 + struct efi_boot_memmap { efi_memory_desc_t **map; unsigned long *map_size; diff --git a/drivers/firmware/efi/libstub/mem.c b/drivers/firmware/efi/libstub/mem.c index 869a79c..09f4fa0 100644 --- a/drivers/firmware/efi/libstub/mem.c +++ b/drivers/firmware/efi/libstub/mem.c @@ -5,8 +5,6 @@ #include "efistub.h" -#define EFI_MMAP_NR_SLACK_SLOTS 8 - static inline bool mmap_has_headroom(unsigned long buff_size, unsigned long map_size, unsigned long desc_size) diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c index 05ccb22..f0339b5 100644 --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -606,24 +606,18 @@ static efi_status_t allocate_e820(struct boot_params *params, struct setup_data **e820ext, u32 *e820ext_size) { - unsigned long map_size, desc_size, buff_size; - struct efi_boot_memmap boot_map; - efi_memory_desc_t *map; + unsigned long map_size, desc_size, map_key; efi_status_t status; - __u32 nr_desc; + __u32 nr_desc, desc_version; - boot_map.map = ↦ - boot_map.map_size = &map_size; - boot_map.desc_size = &desc_size; - boot_map.desc_ver = NULL; - boot_map.key_ptr = NULL; - boot_map.buff_size = &buff_size; + /* Only need the size of the mem map and size of each mem descriptor */ + map_size = 0; + status = efi_bs_call(get_memory_map, &map_size, NULL, &map_key, + &desc_size, &desc_version); + if (status != EFI_BUFFER_TOO_SMALL) + return (status != EFI_SUCCESS) ? status : EFI_UNSUPPORTED; - status = efi_get_memory_map(&boot_map); - if (status != EFI_SUCCESS) - return status; - - nr_desc = buff_size / desc_size; + nr_desc = map_size / desc_size + EFI_MMAP_NR_SLACK_SLOTS; if (nr_desc > ARRAY_SIZE(params->e820_table)) { u32 nr_e820ext = nr_desc - ARRAY_SIZE(params->e820_table); -- 2.7.4