efi/libstub: Allocate headspace in efi_get_memory_map()

efi_get_memory_map() allocates a buffer to store the memory map that it
retrieves.  This buffer may need to be reused by the client after
ExitBootServices() is called, at which point allocations are not longer
permitted.  To support this usecase, provide the allocated buffer size back
to the client, and allocate some additional headroom to account for any
reasonable growth in the map that is likely to happen between the call to
efi_get_memory_map() and the client reusing the buffer.

Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>

1 files changed, 13 insertions, 7 deletions

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index ff574dad95cc..c5b7c7b4f0d7 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -1008,7 +1008,7 @@ static efi_status_t exit_boot(struct boot_params *boot_params,
                               void *handle, bool is64)
 {
         struct efi_info *efi = &boot_params->efi_info;
-        unsigned long map_sz, key, desc_size;
+        unsigned long map_sz, key, desc_size, buff_size;
         efi_memory_desc_t *mem_map;
         struct setup_data *e820ext;
         const char *signature;
@@ -1019,14 +1019,20 @@ static efi_status_t exit_boot(struct boot_params *boot_params,
         bool called_exit = false;
         u8 nr_entries;
         int i;
-
-        nr_desc = 0;
-        e820ext = NULL;
-        e820ext_size = 0;
+        struct efi_boot_memmap map;
+
+        nr_desc =       0;
+        e820ext =       NULL;
+        e820ext_size =  0;
+        map.map =       &mem_map;
+        map.map_size =  &map_sz;
+        map.desc_size = &desc_size;
+        map.desc_ver =  &desc_version;
+        map.key_ptr =   &key;
+        map.buff_size = &buff_size;
 
 get_map:
-        status = efi_get_memory_map(sys_table, &mem_map, &map_sz, &desc_size,
-                                    &desc_version, &key);
+        status = efi_get_memory_map(sys_table, &map);
 
         if (status != EFI_SUCCESS)
                 return status;