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>

5 files changed, 111 insertions, 49 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;
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 3bd127f95315..29368ac69221 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -41,6 +41,8 @@ static unsigned long __chunk_size = EFI_READ_CHUNK_SIZE;
 #define EFI_ALLOC_ALIGN		EFI_PAGE_SIZE
 #endif
 
+#define EFI_MMAP_NR_SLACK_SLOTS	8
+
 struct file_info {
 	efi_file_handle_t *handle;
 	u64 size;
@@ -63,49 +65,62 @@ void efi_printk(efi_system_table_t *sys_table_arg, char *str)
 	}
 }
 
+static inline bool mmap_has_headroom(unsigned long buff_size,
+				     unsigned long map_size,
+				     unsigned long desc_size)
+{
+	unsigned long slack = buff_size - map_size;
+
+	return slack / desc_size >= EFI_MMAP_NR_SLACK_SLOTS;
+}
+
 efi_status_t efi_get_memory_map(efi_system_table_t *sys_table_arg,
-				efi_memory_desc_t **map,
-				unsigned long *map_size,
-				unsigned long *desc_size,
-				u32 *desc_ver,
-				unsigned long *key_ptr)
+				struct efi_boot_memmap *map)
 {
 	efi_memory_desc_t *m = NULL;
 	efi_status_t status;
 	unsigned long key;
 	u32 desc_version;
 
-	*map_size = sizeof(*m) * 32;
+	*map->desc_size =	sizeof(*m);
+	*map->map_size =	*map->desc_size * 32;
+	*map->buff_size =	*map->map_size;
 again:
-	/*
-	 * 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);
 	status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
-				*map_size, (void **)&m);
+				*map->map_size, (void **)&m);
 	if (status != EFI_SUCCESS)
 		goto fail;
 
-	*desc_size = 0;
+	*map->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) {
+	status = efi_call_early(get_memory_map, map->map_size, m,
+				&key, map->desc_size, &desc_version);
+	if (status == EFI_BUFFER_TOO_SMALL ||
+	    !mmap_has_headroom(*map->buff_size, *map->map_size,
+			       *map->desc_size)) {
 		efi_call_early(free_pool, m);
+		/*
+		 * Make sure there is some entries of headroom so that the
+		 * buffer can be reused for a new map after allocations are
+		 * no longer permitted.  Its unlikely that the map will grow to
+		 * exceed this headroom once we are ready to trigger
+		 * ExitBootServices()
+		 */
+		*map->map_size += *map->desc_size * EFI_MMAP_NR_SLACK_SLOTS;
+		*map->buff_size = *map->map_size;
 		goto again;
 	}
 
 	if (status != EFI_SUCCESS)
 		efi_call_early(free_pool, m);
 
-	if (key_ptr && status == EFI_SUCCESS)
-		*key_ptr = key;
-	if (desc_ver && status == EFI_SUCCESS)
-		*desc_ver = desc_version;
+	if (map->key_ptr && status == EFI_SUCCESS)
+		*map->key_ptr = key;
+	if (map->desc_ver && status == EFI_SUCCESS)
+		*map->desc_ver = desc_version;
 
 fail:
-	*map = m;
+	*map->map = m;
 	return status;
 }
 
@@ -113,13 +128,20 @@ fail:
 unsigned long get_dram_base(efi_system_table_t *sys_table_arg)
 {
 	efi_status_t status;
-	unsigned long map_size;
+	unsigned long map_size, buff_size;
 	unsigned long membase  = EFI_ERROR;
 	struct efi_memory_map map;
 	efi_memory_desc_t *md;
+	struct efi_boot_memmap boot_map;
 
-	status = efi_get_memory_map(sys_table_arg, (efi_memory_desc_t **)&map.map,
-				    &map_size, &map.desc_size, NULL, NULL);
+	boot_map.map =		(efi_memory_desc_t **)&map.map;
+	boot_map.map_size =	&map_size;
+	boot_map.desc_size =	&map.desc_size;
+	boot_map.desc_ver =	NULL;
+	boot_map.key_ptr =	NULL;
+	boot_map.buff_size =	&buff_size;
+
+	status = efi_get_memory_map(sys_table_arg, &boot_map);
 	if (status != EFI_SUCCESS)
 		return membase;
 
@@ -144,15 +166,22 @@ efi_status_t efi_high_alloc(efi_system_table_t *sys_table_arg,
 			    unsigned long size, unsigned long align,
 			    unsigned long *addr, unsigned long max)
 {
-	unsigned long map_size, desc_size;
+	unsigned long map_size, desc_size, buff_size;
 	efi_memory_desc_t *map;
 	efi_status_t status;
 	unsigned long nr_pages;
 	u64 max_addr = 0;
 	int i;
+	struct efi_boot_memmap boot_map;
+
+	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;
 
-	status = efi_get_memory_map(sys_table_arg, &map, &map_size, &desc_size,
-				    NULL, NULL);
+	status = efi_get_memory_map(sys_table_arg, &boot_map);
 	if (status != EFI_SUCCESS)
 		goto fail;
 
@@ -230,14 +259,21 @@ efi_status_t efi_low_alloc(efi_system_table_t *sys_table_arg,
 			   unsigned long size, unsigned long align,
 			   unsigned long *addr)
 {
-	unsigned long map_size, desc_size;
+	unsigned long map_size, desc_size, buff_size;
 	efi_memory_desc_t *map;
 	efi_status_t status;
 	unsigned long nr_pages;
 	int i;
+	struct efi_boot_memmap boot_map;
+
+	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;
 
-	status = efi_get_memory_map(sys_table_arg, &map, &map_size, &desc_size,
-				    NULL, NULL);
+	status = efi_get_memory_map(sys_table_arg, &boot_map);
 	if (status != EFI_SUCCESS)
 		goto fail;
 
diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index e58abfa953cc..bec0fa8d8746 100644
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -175,13 +175,21 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
 					    unsigned long fdt_addr,
 					    unsigned long fdt_size)
 {
-	unsigned long map_size, desc_size;
+	unsigned long map_size, desc_size, buff_size;
 	u32 desc_ver;
 	unsigned long mmap_key;
 	efi_memory_desc_t *memory_map, *runtime_map;
 	unsigned long new_fdt_size;
 	efi_status_t status;
 	int runtime_entry_count = 0;
+	struct efi_boot_memmap map;
+
+	map.map =	&runtime_map;
+	map.map_size =	&map_size;
+	map.desc_size =	&desc_size;
+	map.desc_ver =	&desc_ver;
+	map.key_ptr =	&mmap_key;
+	map.buff_size =	&buff_size;
 
 	/*
 	 * Get a copy of the current memory map that we will use to prepare
@@ -189,8 +197,7 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
 	 * subsequent allocations adding entries, since they could not affect
 	 * the number of EFI_MEMORY_RUNTIME regions.
 	 */
-	status = efi_get_memory_map(sys_table, &runtime_map, &map_size,
-				    &desc_size, &desc_ver, &mmap_key);
+	status = efi_get_memory_map(sys_table, &map);
 	if (status != EFI_SUCCESS) {
 		pr_efi_err(sys_table, "Unable to retrieve UEFI memory map.\n");
 		return status;
@@ -199,6 +206,7 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
 	pr_efi(sys_table,
 	       "Exiting boot services and installing virtual address map...\n");
 
+	map.map = &memory_map;
 	/*
 	 * Estimate size of new FDT, and allocate memory for it. We
 	 * will allocate a bigger buffer if this ends up being too
@@ -218,8 +226,7 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
 		 * we can get the memory map key  needed for
 		 * exit_boot_services().
 		 */
-		status = efi_get_memory_map(sys_table, &memory_map, &map_size,
-					    &desc_size, &desc_ver, &mmap_key);
+		status = efi_get_memory_map(sys_table, &map);
 		if (status != EFI_SUCCESS)
 			goto fail_free_new_fdt;
 
diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c
index 53f6d3fe6d86..0c9f58c5ba50 100644
--- a/drivers/firmware/efi/libstub/random.c
+++ b/drivers/firmware/efi/libstub/random.c
@@ -73,12 +73,20 @@ efi_status_t efi_random_alloc(efi_system_table_t *sys_table_arg,
 			      unsigned long random_seed)
 {
 	unsigned long map_size, desc_size, total_slots = 0, target_slot;
+	unsigned long buff_size;
 	efi_status_t status;
 	efi_memory_desc_t *memory_map;
 	int map_offset;
+	struct efi_boot_memmap map;
 
-	status = efi_get_memory_map(sys_table_arg, &memory_map, &map_size,
-				    &desc_size, NULL, NULL);
+	map.map =	&memory_map;
+	map.map_size =	&map_size;
+	map.desc_size =	&desc_size;
+	map.desc_ver =	NULL;
+	map.key_ptr =	NULL;
+	map.buff_size =	&buff_size;
+
+	status = efi_get_memory_map(sys_table_arg, &map);
 	if (status != EFI_SUCCESS)
 		return status;
 
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 23cd3ced8c1a..943fee524176 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -118,6 +118,15 @@ typedef struct {
 	u32 imagesize;
 } efi_capsule_header_t;
 
+struct efi_boot_memmap {
+	efi_memory_desc_t	**map;
+	unsigned long		*map_size;
+	unsigned long		*desc_size;
+	u32			*desc_ver;
+	unsigned long		*key_ptr;
+	unsigned long		*buff_size;
+};
+
 /*
  * EFI capsule flags
  */
@@ -1371,11 +1380,7 @@ char *efi_convert_cmdline(efi_system_table_t *sys_table_arg,
 			  efi_loaded_image_t *image, int *cmd_line_len);
 
 efi_status_t efi_get_memory_map(efi_system_table_t *sys_table_arg,
-				efi_memory_desc_t **map,
-				unsigned long *map_size,
-				unsigned long *desc_size,
-				u32 *desc_ver,
-				unsigned long *key_ptr);
+				struct efi_boot_memmap *map);
 
 efi_status_t efi_low_alloc(efi_system_table_t *sys_table_arg,
 			   unsigned long size, unsigned long align,