1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/efi.h>
4 #include <asm/efi.h>
5
6 #include "efistub.h"
7
8 /*
9 * There are two ways of populating the core kernel's struct screen_info via the stub:
10 * - using a configuration table, like below, which relies on the EFI init code
11 * to locate the table and copy the contents;
12 * - by linking directly to the core kernel's copy of the global symbol.
13 *
14 * The latter is preferred because it makes the EFIFB earlycon available very
15 * early, but it only works if the EFI stub is part of the core kernel image
16 * itself. The zboot decompressor can only use the configuration table
17 * approach.
18 *
19 * In order to support both methods from the same build of the EFI stub
20 * library, provide this dummy global definition of struct screen_info. If it
21 * is required to satisfy a link dependency, it means we need to override the
22 * __weak alloc and free methods with the ones below, and those will be pulled
23 * in as well.
24 */
25 struct screen_info screen_info;
26
27 static efi_guid_t screen_info_guid = LINUX_EFI_SCREEN_INFO_TABLE_GUID;
28
alloc_screen_info(void)29 struct screen_info *alloc_screen_info(void)
30 {
31 struct screen_info *si;
32 efi_status_t status;
33
34 status = efi_bs_call(allocate_pool, EFI_ACPI_RECLAIM_MEMORY,
35 sizeof(*si), (void **)&si);
36
37 if (status != EFI_SUCCESS)
38 return NULL;
39
40 status = efi_bs_call(install_configuration_table,
41 &screen_info_guid, si);
42 if (status == EFI_SUCCESS)
43 return si;
44
45 efi_bs_call(free_pool, si);
46 return NULL;
47 }
48
free_screen_info(struct screen_info * si)49 void free_screen_info(struct screen_info *si)
50 {
51 if (!si)
52 return;
53
54 efi_bs_call(install_configuration_table, &screen_info_guid, NULL);
55 efi_bs_call(free_pool, si);
56 }
57