loader: Load a splash screen if "splash" variable is defined

Load a splash screen that vt(4) can use if the "splash" env variable is defined.
For now only png is supported and decoding is done in loader and not in kernel
compared to splash screen support in sc(4).

For using this add:
boot_mute="YES"
splash="/boot/images/freebsd-logo-rev.png"
in loader.conf

Differential Revision:	https://reviews.freebsd.org/D45932
Reviewed by:		imp, tsoome
Sponsored by:		Beckhoff Automation GmbH & Co. KG

stand/common/bootstrap.h

@@ -282,6 +282,7 @@ int tslog_init(void);
 int tslog_publish(void);
 
 vm_offset_t build_font_module(vm_offset_t);
+vm_offset_t build_splash_module(vm_offset_t);
 
 /* MI module loaders */
 #ifdef __elfN

stand/common/gfx_fb.c

@@ -87,6 +87,7 @@
 #include <teken.h>
 #include <gfx_fb.h>
 #include <sys/font.h>
+#include <sys/splash.h>
 #include <sys/linker.h>
 #include <sys/module.h>
 #include <sys/stdint.h>
@@ -3007,3 +3008,50 @@ build_font_module(vm_offset_t addr)
 	file_addmetadata(fp, MODINFOMD_FONT, sizeof(fontp), &fontp);
 	return (addr);
 }
+
+vm_offset_t
+build_splash_module(vm_offset_t addr)
+{
+	struct preloaded_file *fp;
+	struct splash_info si;
+	const char *splash;
+	png_t png;
+	uint64_t splashp;
+	int error;
+
+	/* We can't load first */
+	if ((file_findfile(NULL, NULL)) == NULL) {
+		printf("Can not load splash module: %s\n",
+		    "the kernel is not loaded");
+		return (addr);
+	}
+
+	fp = file_findfile(NULL, "elf kernel");
+	if (fp == NULL)
+		fp = file_findfile(NULL, "elf64 kernel");
+	if (fp == NULL)
+		panic("can't find kernel file");
+
+	splash = getenv("splash");
+	if (splash == NULL)
+		return (addr);
+
+	/* Parse png */
+	if ((error = png_open(&png, splash)) != PNG_NO_ERROR) {
+		return (addr);
+	}
+
+	si.si_width = png.width;
+	si.si_height = png.height;
+	si.si_depth = png.bpp;
+	splashp = addr;
+	addr += archsw.arch_copyin(&si, addr, sizeof (struct splash_info));
+	addr = roundup2(addr, 8);
+
+	/* Copy the bitmap. */
+	addr += archsw.arch_copyin(png.image, addr, png.png_datalen);
+
+	printf("Loading splash ok\n");
+	file_addmetadata(fp, MODINFOMD_SPLASH, sizeof(splashp), &splashp);
+	return (addr);
+}

stand/efi/loader/bootinfo.c

@@ -390,6 +390,11 @@ bi_load(char *args, vm_offset_t *modulep, vm_offset_t *kernendp, bool exit_bs)
 
 	/* Pad to a page boundary. */
 	addr = roundup(addr, PAGE_SIZE);
+
+	addr = build_splash_module(addr);
+
+	/* Pad to a page boundary. */
+	addr = roundup(addr, PAGE_SIZE);
 #endif
 
 	/* Copy our environment. */