fb: Add custom boot logo support

Some distributions wish to customize m1n1's boot logo. Instead having
overwrite the existing logo files add build system support for this.

`make LOGO=custom` will create m1n1.bin with a custom logo created from
'data/custom_{128,256}.png'. In addition m1n1-asahi.bin is created which
carries only the built-in asahi logo.
This is implemented via a logo payload which used by m1n1 when it's the
first payload.

Closes: #238
Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

Makefile

@@ -234,10 +234,21 @@ build/$(NAME).macho: build/$(NAME).elf
 	$(QUIET)echo "  MACHO $@"
 	$(QUIET)$(OBJCOPY) -O binary --strip-debug $< $@
 
+ifeq ($(LOGO),)
 build/$(NAME).bin: build/$(NAME)-raw.elf
 	$(QUIET)echo "  RAW   $@"
 	$(QUIET)$(OBJCOPY) -O binary --strip-debug $< $@
 
+else
+build/$(NAME)-asahi.bin: build/$(NAME)-raw.elf
+	$(QUIET)echo "  RAW   $@"
+	$(QUIET)$(OBJCOPY) -O binary --strip-debug $< $@
+
+build/$(NAME).bin: build/$(NAME)-asahi.bin build/$(LOGO).logo
+	$(QUIET)echo "  RAW   $@"
+	$(QUIET)cat $^ > $@
+endif
+
 .INTERMEDIATE: build-tag build-cfg
 build-tag src/../build/build_tag.h &:
 	$(QUIET)mkdir -p build
@@ -266,4 +277,16 @@ build/%.bin: font/%.bin
 	$(QUIET)mkdir -p "$(dir $@)"
 	$(QUIET)cp $< $@
 
+build/%.rgba: data/%.png
+	$(eval SIZE := $(lastword $(subst _, ,$*)))
+	$(QUIET)echo "  MAGIC $@"
+	$(QUIET)mkdir -p "$(dir $@)"
+	$(QUIET)magick $< -background black -flatten -depth 8 -crop $(SIZE)x$(SIZE) -resize $(SIZE)x$(SIZE) rgba:$@
+
+build/%.logo: build/%_256.rgba build/%_128.rgba
+	$(QUIET)echo "  PAYLOAD $@"
+	$(QUIET)mkdir -p "$(dir $@)"
+	$(QUIET)echo -n "m1n1_logo_256128" > $@
+	$(QUIET)cat $^ >> $@
+
 -include $(DEPDIR)/*

src/fb.c

@@ -5,6 +5,7 @@
 #include "iodev.h"
 #include "malloc.h"
 #include "memory.h"
+#include "payload.h"
 #include "string.h"
 #include "types.h"
 #include "utils.h"
@@ -69,6 +70,8 @@ const struct image logo_256 = {
     .height = 256,
 };
 
+struct image custom_logo = {};
+
 const struct image *logo;
 struct image orig_logo;
 
@@ -402,6 +405,7 @@ void fb_clear_direct(void)
 
 void fb_init(bool clear)
 {
+    void *custom_128, *custom_256;
     fb.hwptr = (void *)cur_boot_args.video.base;
     fb.stride = cur_boot_args.video.stride / 4;
     fb.width = cur_boot_args.video.width;
@@ -460,6 +464,19 @@ void fb_init(bool clear)
                         &orig_logo);
     }
 
+    if (payload_logo(&custom_128, &custom_256)) {
+        custom_logo = *logo;
+        if (custom_logo.width == 256) {
+            custom_logo.ptr = custom_256;
+            logo = &custom_logo;
+        } else if (custom_logo.width == 128) {
+            custom_logo.ptr = custom_128;
+            logo = &custom_logo;
+        } else {
+            printf("fb: unexpected logo dimensions %ux%u\n", custom_logo.width, custom_logo.height);
+        }
+    }
+
     if (clear) {
         memset32(fb.ptr, 0, fb.size);
     } else {

src/payload.c

@@ -34,6 +34,11 @@ static const u8 initramfs_magic[] = {
     'i', 't', 'r', 'a', 'm', 'f', 's'}; // followed by size as little endian uint32_t
 static const u8 empty[] = {0, 0, 0, 0};
 
+// custom logo is RGBA with 256x256 retina logo followed by half resolution
+static const u8 custom_logo_magic[] = {'m', '1', 'n', '1', '_', 'l', 'o', 'g',
+                                       'o', '_', '2', '5', '6', '1', '2', '8'};
+#define CUSTOM_LOGO_SIZE (4 * ((256 * 256) + (128 * 128)))
+
 static char expect_compatible[256];
 static struct kernel_header *kernel = NULL;
 static void *fdt = NULL;
@@ -241,6 +246,10 @@ static void *load_one_payload(void *start, size_t size)
         printf("Found a m1n1 initramfs payload at %p, 0x%x bytes\n", p, size);
         p += sizeof(initramfs_magic) + 4;
         return load_cpio(p, size);
+    } else if (!memcmp(p, custom_logo_magic, sizeof(custom_logo_magic))) {
+        printf("Found a m1n1 custom logo payload at %p, skipping 0x%lx bytes\n", p,
+               sizeof(custom_logo_magic) + CUSTOM_LOGO_SIZE);
+        return p + sizeof(custom_logo_magic) + CUSTOM_LOGO_SIZE;
     } else if (check_var(&p)) {
         return p;
     } else if (!memcmp(p, empty, sizeof empty) ||
@@ -260,6 +269,25 @@ void do_enable_tso(void)
     msr(ACTLR_EL1, actlr);
 }
 
+bool payload_logo(void **custom_128, void **custom_256)
+{
+    void *p = _payload_start;
+
+    *custom_128 = NULL;
+    *custom_256 = NULL;
+
+    if (!memcmp(p, custom_logo_magic, sizeof(custom_logo_magic))) {
+        void *data = p + sizeof(custom_logo_magic);
+        printf("Found a m1n1 custom logo payload at %p\n", p);
+        *custom_256 = data;
+        *custom_128 = data + 4 * 256 * 256;
+
+        return true;
+    }
+
+    return false;
+}
+
 int payload_run(void)
 {
     const char *target = adt_getprop(adt, 0, "target-type", NULL);

src/payload.h

@@ -3,6 +3,10 @@
 #ifndef __PAYLOAD_H__
 #define __PAYLOAD_H__
 
+#include "types.h"
+
+bool payload_logo(void **custom_128, void **custom_256);
+
 int payload_run(void);
 
 #endif