efi/arm/libstub: Make screen_info accessible to the UEFI stub

In order to hand over the framebuffer described by the GOP protocol and
discovered by the UEFI stub, make struct screen_info accessible by the
stub. This involves allocating a loader data buffer and passing it to the
kernel proper via a UEFI Configuration Table, since the UEFI stub executes
in the context of the decompressor, and cannot access the kernel's copy of
struct screen_info directly.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Jones <pjones@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1461614832-17633-22-git-send-email-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 33 insertions, 1 deletions

diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
index 909d974d35d9..ac95dd8b119f 100644
--- a/drivers/firmware/efi/arm-init.c
+++ b/drivers/firmware/efi/arm-init.c
@@ -11,12 +11,15 @@
  *
  */
 
+#define pr_fmt(fmt)     "efi: " fmt
+
 #include <linux/efi.h>
 #include <linux/init.h>
 #include <linux/memblock.h>
 #include <linux/mm_types.h>
 #include <linux/of.h>
 #include <linux/of_fdt.h>
+#include <linux/screen_info.h>
 
 #include <asm/efi.h>
 
@@ -51,6 +54,32 @@ static phys_addr_t efi_to_phys(unsigned long addr)
         return addr;
 }
 
+static __initdata unsigned long screen_info_table = EFI_INVALID_TABLE_ADDR;
+
+static __initdata efi_config_table_type_t arch_tables[] = {
+        {LINUX_EFI_ARM_SCREEN_INFO_TABLE_GUID, NULL, &screen_info_table},
+        {NULL_GUID, NULL, NULL}
+};
+
+static void __init init_screen_info(void)
+{
+        struct screen_info *si;
+
+        if (screen_info_table != EFI_INVALID_TABLE_ADDR) {
+                si = early_memremap_ro(screen_info_table, sizeof(*si));
+                if (!si) {
+                        pr_err("Could not map screen_info config table\n");
+                        return;
+                }
+                screen_info = *si;
+                early_memunmap(si, sizeof(*si));
+
+                /* dummycon on ARM needs non-zero values for columns/lines */
+                screen_info.orig_video_cols = 80;
+                screen_info.orig_video_lines = 25;
+        }
+}
+
 static int __init uefi_init(void)
 {
         efi_char16_t *c16;
@@ -108,7 +137,8 @@ static int __init uefi_init(void)
                 goto out;
         }
         retval = efi_config_parse_tables(config_tables, efi.systab->nr_tables,
-                                         sizeof(efi_config_table_t), NULL);
+                                         sizeof(efi_config_table_t),
+                                         arch_tables);
 
         early_memunmap(config_tables, table_size);
 out:
@@ -223,4 +253,6 @@ void __init efi_init(void)
                                  PAGE_ALIGN(params.mmap_size +
                                             (params.mmap & ~PAGE_MASK)));
         }
+
+        init_screen_info();
 }