Commit fd626195 authored by Lenny Szubowicz's avatar Lenny Szubowicz Committed by Ard Biesheuvel
Browse files

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: default avatarLenny Szubowicz <lszubowi@redhat.com>
Suggested-by: default avatarArd Biesheuvel <ardb@kernel.org>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
parent 8f592ada

drivers/firmware/efi/libstub/efistub.h

+13 −0
Original line number Diff line number Diff line
@@ -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;

drivers/firmware/efi/libstub/mem.c

+0 −2
Original line number Diff line number Diff line
@@ -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)

drivers/firmware/efi/libstub/x86-stub.c

+9 −15
Original line number Diff line number Diff line
@@ -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		= &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);

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