efi: libstub: Move screen_info handling to common code

Currently, arm64, RISC-V and LoongArch rely on the fact that struct
screen_info can be accessed directly, due to the fact that the EFI stub
and the core kernel are part of the same image. This will change after a
future patch, so let's ensure that the screen_info handling is able to
deal with this, by adopting the arm32 approach of passing it as a
configuration table. While at it, switch to ACPI reclaim memory to hold
the screen_info data, which is more appropriate for this kind of
allocation.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

7 files changed, 93 insertions, 41 deletions

diff --git a/drivers/firmware/efi/efi-init.c b/drivers/firmware/efi/efi-init.c
index 2fd770b499a3..1639159493e3 100644
--- a/drivers/firmware/efi/efi-init.c
+++ b/drivers/firmware/efi/efi-init.c
@@ -22,6 +22,8 @@
 
 #include <asm/efi.h>
 
+unsigned long __initdata screen_info_table = EFI_INVALID_TABLE_ADDR;
+
 static int __init is_memory(efi_memory_desc_t *md)
 {
 	if (md->attribute & (EFI_MEMORY_WB|EFI_MEMORY_WT|EFI_MEMORY_WC))
@@ -55,9 +57,22 @@ extern __weak const efi_config_table_type_t efi_arch_tables[];
 
 static void __init init_screen_info(void)
 {
-	if (screen_info.orig_video_isVGA == VIDEO_TYPE_EFI &&
-	    memblock_is_map_memory(screen_info.lfb_base))
-		memblock_mark_nomap(screen_info.lfb_base, screen_info.lfb_size);
+	struct screen_info *si;
+
+	if (screen_info_table != EFI_INVALID_TABLE_ADDR) {
+		si = early_memremap(screen_info_table, sizeof(*si));
+		if (!si) {
+			pr_err("Could not map screen_info config table\n");
+			return;
+		}
+		screen_info = *si;
+		memset(si, 0, sizeof(*si));
+		early_memunmap(si, sizeof(*si));
+
+		if (memblock_is_map_memory(screen_info.lfb_base))
+			memblock_mark_nomap(screen_info.lfb_base,
+					    screen_info.lfb_size);
+	}
 }
 
 static int __init uefi_init(u64 efi_system_table)
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index a46df5d1d094..951a42d27cf4 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -58,6 +58,8 @@ static unsigned long __initdata mem_reserve = EFI_INVALID_TABLE_ADDR;
 static unsigned long __initdata rt_prop = EFI_INVALID_TABLE_ADDR;
 static unsigned long __initdata initrd = EFI_INVALID_TABLE_ADDR;
 
+extern unsigned long screen_info_table;
+
 struct mm_struct efi_mm = {
 	.mm_mt			= MTREE_INIT_EXT(mm_mt, MM_MT_FLAGS, efi_mm.mmap_lock),
 	.mm_users		= ATOMIC_INIT(2),
@@ -547,6 +549,9 @@ static const efi_config_table_type_t common_tables[] __initconst = {
 #ifdef CONFIG_EFI_COCO_SECRET
 	{LINUX_EFI_COCO_SECRET_AREA_GUID,	&efi.coco_secret,	"CocoSecret"	},
 #endif
+#ifdef CONFIG_EFI_GENERIC_STUB
+	{LINUX_EFI_SCREEN_INFO_TABLE_GUID,	&screen_info_table			},
+#endif
 	{},
 };
 
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 5b0ae755180e..3f44e272ff9c 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -81,7 +81,8 @@ lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \
 $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
 	$(call if_changed_rule,cc_o_c)
 
-lib-$(CONFIG_EFI_GENERIC_STUB)	+= efi-stub.o string.o intrinsics.o systable.o
+lib-$(CONFIG_EFI_GENERIC_STUB)	+= efi-stub.o string.o intrinsics.o systable.o \
+				   screen_info.o
 
 lib-$(CONFIG_ARM)		+= arm32-stub.o
 lib-$(CONFIG_ARM64)		+= arm64-stub.o arm64-entry.o
diff --git a/drivers/firmware/efi/libstub/arm32-stub.c b/drivers/firmware/efi/libstub/arm32-stub.c
index 0131e3aaa605..1073dd947516 100644
--- a/drivers/firmware/efi/libstub/arm32-stub.c
+++ b/drivers/firmware/efi/libstub/arm32-stub.c
@@ -76,43 +76,6 @@ void efi_handle_post_ebs_state(void)
 		      &efi_entry_state->sctlr_after_ebs);
 }
 
-static efi_guid_t screen_info_guid = LINUX_EFI_ARM_SCREEN_INFO_TABLE_GUID;
-
-struct screen_info *alloc_screen_info(void)
-{
-	struct screen_info *si;
-	efi_status_t status;
-
-	/*
-	 * Unlike on arm64, where we can directly fill out the screen_info
-	 * structure from the stub, we need to allocate a buffer to hold
-	 * its contents while we hand over to the kernel proper from the
-	 * decompressor.
-	 */
-	status = efi_bs_call(allocate_pool, EFI_RUNTIME_SERVICES_DATA,
-			     sizeof(*si), (void **)&si);
-
-	if (status != EFI_SUCCESS)
-		return NULL;
-
-	status = efi_bs_call(install_configuration_table,
-			     &screen_info_guid, si);
-	if (status == EFI_SUCCESS)
-		return si;
-
-	efi_bs_call(free_pool, si);
-	return NULL;
-}
-
-void free_screen_info(struct screen_info *si)
-{
-	if (!si)
-		return;
-
-	efi_bs_call(install_configuration_table, &screen_info_guid, NULL);
-	efi_bs_call(free_pool, si);
-}
-
 efi_status_t handle_kernel_image(unsigned long *image_addr,
 				 unsigned long *image_size,
 				 unsigned long *reserve_addr,
diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
index b55d1009d4c8..8521dc09c6ae 100644
--- a/drivers/firmware/efi/libstub/efi-stub.c
+++ b/drivers/firmware/efi/libstub/efi-stub.c
@@ -47,6 +47,15 @@
 static u64 virtmap_base = EFI_RT_VIRTUAL_BASE;
 static bool flat_va_mapping = (EFI_RT_VIRTUAL_OFFSET != 0);
 
+struct screen_info * __weak alloc_screen_info(void)
+{
+	return &screen_info;
+}
+
+void __weak free_screen_info(struct screen_info *si)
+{
+}
+
 static struct screen_info *setup_graphics(void)
 {
 	efi_guid_t gop_proto = EFI_GRAPHICS_OUTPUT_PROTOCOL_GUID;
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index a30fb5d8ef05..a4cb51e2cae3 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -975,4 +975,7 @@ efi_enable_reset_attack_mitigation(void) { }
 
 void efi_retrieve_tpm2_eventlog(void);
 
+struct screen_info *alloc_screen_info(void);
+void free_screen_info(struct screen_info *si);
+
 #endif
diff --git a/drivers/firmware/efi/libstub/screen_info.c b/drivers/firmware/efi/libstub/screen_info.c
new file mode 100644
index 000000000000..8e76a8b384ba
--- /dev/null
+++ b/drivers/firmware/efi/libstub/screen_info.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/efi.h>
+#include <asm/efi.h>
+
+#include "efistub.h"
+
+/*
+ * There are two ways of populating the core kernel's struct screen_info via the stub:
+ * - using a configuration table, like below, which relies on the EFI init code
+ *   to locate the table and copy the contents;
+ * - by linking directly to the core kernel's copy of the global symbol.
+ *
+ * The latter is preferred because it makes the EFIFB earlycon available very
+ * early, but it only works if the EFI stub is part of the core kernel image
+ * itself. The zboot decompressor can only use the configuration table
+ * approach.
+ *
+ * In order to support both methods from the same build of the EFI stub
+ * library, provide this dummy global definition of struct screen_info. If it
+ * is required to satisfy a link dependency, it means we need to override the
+ * __weak alloc and free methods with the ones below, and those will be pulled
+ * in as well.
+ */
+struct screen_info screen_info;
+
+static efi_guid_t screen_info_guid = LINUX_EFI_SCREEN_INFO_TABLE_GUID;
+
+struct screen_info *alloc_screen_info(void)
+{
+	struct screen_info *si;
+	efi_status_t status;
+
+	status = efi_bs_call(allocate_pool, EFI_ACPI_RECLAIM_MEMORY,
+			     sizeof(*si), (void **)&si);
+
+	if (status != EFI_SUCCESS)
+		return NULL;
+
+	status = efi_bs_call(install_configuration_table,
+			     &screen_info_guid, si);
+	if (status == EFI_SUCCESS)
+		return si;
+
+	efi_bs_call(free_pool, si);
+	return NULL;
+}
+
+void free_screen_info(struct screen_info *si)
+{
+	if (!si)
+		return;
+
+	efi_bs_call(install_configuration_table, &screen_info_guid, NULL);
+	efi_bs_call(free_pool, si);
+}