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efi/libstub: Call get_memory_map() to obtain map and desc sizes

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This fixes two minor issues in the implementation of get_memory_map():
- Currently, it assumes that sizeof(efi_memory_desc_t) == desc_size,
  which is usually true, but not mandated by the spec. (This was added
  intentionally to allow future additions to the definition of
  efi_memory_desc_t). The way the loop is implemented currently, the
  added slack space may be insufficient if desc_size is larger, which in
  some corner cases could result in the loop never terminating.
- It allocates 32 efi_memory_desc_t entries first (again, using the size
  of the struct instead of desc_size), and frees and reallocates if it
  turns out to be insufficient. Few implementations of UEFI have such small
  memory maps, which results in a unnecessary allocate/free pair on each
  invocation.

Fix this by calling the get_memory_map() boot service first with a '0'
input value for map size to retrieve the map size and desc size from the
firmware and only then perform the allocation, using desc_size rather
than sizeof(efi_memory_desc_t).

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
This commit is contained in:
Ard Biesheuvel 2015-01-08 17:51:47 +00:00 committed by Matt Fleming
parent 86d68a58d0
commit d1a8d66b91
1 changed files with 10 additions and 6 deletions
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16
drivers/firmware/efi/libstub/efi-stub-helper.c
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@ -66,25 +66,29 @@ efi_status_t efi_get_memory_map(efi_system_table_t *sys_table_arg,
unsigned long key;
u32 desc_version;
*map_size = sizeof(*m) * 32;
again:
*map_size = 0;
*desc_size = 0;
key = 0;
status = efi_call_early(get_memory_map, map_size, NULL,
&key, desc_size, &desc_version);
if (status != EFI_BUFFER_TOO_SMALL)
return EFI_LOAD_ERROR;
/*
* Add an additional efi_memory_desc_t because we're doing an
* allocation which may be in a new descriptor region.
*/
*map_size += sizeof(*m);
*map_size += *desc_size;
status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
*map_size, (void **)&m);
if (status != EFI_SUCCESS)
goto fail;
*desc_size = 0;
key = 0;
status = efi_call_early(get_memory_map, map_size, m,
&key, desc_size, &desc_version);
if (status == EFI_BUFFER_TOO_SMALL) {
efi_call_early(free_pool, m);
goto again;
return EFI_LOAD_ERROR;
}
if (status != EFI_SUCCESS)