The spec allows ExitBootServices to fail with EFI_INVALID_PARAMETER if a
race condition has occurred where the EFI has updated the memory map after
the stub grabbed a reference to the map. The spec defines a retry
proceedure with specific requirements to handle this scenario.
No current stub implementation correctly follows the spec in this regard,
so add a helper to the stub library that correctly adhears to the spec and
abstracts the complexity from stubs.
Signed-off-by: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
---
drivers/firmware/efi/libstub/efi-stub-helper.c | 93 ++++++++++++++++++++++++++
include/linux/efi.h | 19 ++++++
2 files changed, 112 insertions(+)
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 3071269..d5be0b5 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -720,3 +720,96 @@ char *efi_convert_cmdline(efi_system_table_t *sys_table_arg,
*cmd_line_len = options_bytes;
return (char *)cmdline_addr;
}
+
+/*
+ * Handle calling ExitBootServices according to the requirements set out by the
+ * spec. Obtains the current memory map, and returns that info after calling
+ * ExitBootServices. Client has the option to specify a function to process the
+ * memory map data. A client specific structure may be passed to the function
+ * via priv. The client function may be called multiple times.
+ */
+efi_status_t efi_exit_boot_services(efi_system_table_t *sys_table,
+ void *handle,
+ efi_memory_desc_t **memory_map,
+ unsigned long *map_size,
+ unsigned long *desc_size,
+ u32 *desc_ver,
+ unsigned long *mmap_key,
+ void *priv,
+ efi_status_t (*priv_func)(
+ efi_system_table_t *sys_table,
+ void *handle,
+ efi_memory_desc_t *memory_map,
+ unsigned long *map_size,
+ unsigned long *desc_size,
+ u32 *desc_ver,
+ unsigned long *mmap_key,
+ unsigned long buff_size,
+ void *priv))
+{
+ efi_status_t status;
+ unsigned long buff_size;
+
+ status = efi_get_memory_map(sys_table, memory_map, map_size,
+ desc_size, desc_ver, mmap_key, &buff_size);
+
+ if (status != EFI_SUCCESS)
+ goto fail;
+
+ if (priv_func) {
+ status = priv_func(sys_table, handle, *memory_map, map_size,
+ desc_size, desc_ver, mmap_key, buff_size,
+ priv);
+ if (status != EFI_SUCCESS)
+ goto free_map;
+ }
+
+ status = sys_table->boottime->exit_boot_services(handle, *mmap_key);
+
+ if (status == EFI_INVALID_PARAMETER) {
+ /*
+ * The memory map changed between efi_get_memory_map() and
+ * exit_boot_services(). Per the spec we need to get the
+ * updated map, and try again. The spec implies one retry
+ * should be sufficent, which is confirmed against the EDK2
+ * implementation. Per the spec, we can only invoke
+ * get_memory_map() and exit_boot_services() - we cannot alloc
+ * so efi_get_memory_map() cannot be used, and we must reuse
+ * the buffer. For all practical purposes, the headroom in the
+ * buffer should account for any changes in the map so the call
+ * to get_memory_map() is expected to succeed here.
+ */
+ *map_size = buff_size;
+ status = sys_table->boottime->get_memory_map(map_size,
+ *memory_map,
+ mmap_key,
+ desc_size,
+ desc_ver);
+ if (status != EFI_SUCCESS)
+ /* exit_boot_services() was called, thus cannot free*/
+ goto fail;
+
+ if (priv_func) {
+ status = priv_func(sys_table, handle, *memory_map,
+ map_size, desc_size, desc_ver,
+ mmap_key, buff_size, priv);
+ if (status != EFI_SUCCESS)
+ /* exit_boot_services() called, cannot free*/
+ goto fail;
+ }
+
+ status = sys_table->boottime->exit_boot_services(handle,
+ *mmap_key);
+ }
+
+ if (status != EFI_SUCCESS)
+ /* exit_boot_services() was called, thus cannot free*/
+ goto fail;
+
+ return EFI_SUCCESS;
+
+free_map:
+ sys_table->boottime->free_pool(*memory_map);
+fail:
+ return status;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index c47fc5f..96f7b74 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1466,4 +1466,23 @@ efi_status_t efi_setup_gop(efi_system_table_t *sys_table_arg,
unsigned long size);
bool efi_runtime_disabled(void);
+
+efi_status_t efi_exit_boot_services(efi_system_table_t *sys_table,
+ void *handle,
+ efi_memory_desc_t **memory_map,
+ unsigned long *map_size,
+ unsigned long *desc_size,
+ u32 *desc_ver,
+ unsigned long *mmap_key,
+ void *priv,
+ efi_status_t (*priv_func)(
+ efi_system_table_t *sys_table,
+ void *handle,
+ efi_memory_desc_t *memory_map,
+ unsigned long *map_size,
+ unsigned long *desc_size,
+ u32 *desc_ver,
+ unsigned long *mmap_key,
+ unsigned long buff_size,
+ void *priv));
#endif /* _LINUX_EFI_H */
--
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Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.
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