efi/x86: Convert x86 EFI earlyprintk into generic earlycon implementation

Move the x86 EFI earlyprintk implementation to a shared location under
drivers/firmware and tweak it slightly so we can expose it as an earlycon
implementation (which is generic) rather than earlyprintk (which is only
implemented for a few architectures)

This also involves switching to write-combine mappings by default (which
is required on ARM since device mappings lack memory semantics, and so
memcpy/memset may not be used on them), and adding support for shared
memory framebuffers on cache coherent non-x86 systems (which do not
tolerate mismatched attributes).

Note that 32-bit ARM does not populate its struct screen_info early
enough for earlycon=efifb to work, so it is disabled there.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Alexander Graf <agraf@suse.de>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Jeffrey Hugo <jhugo@codeaurora.org>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Jones <pjones@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20190202094119.13230-10-ard.biesheuvel@linaro.orgSigned-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/admin-guide/kernel-parameters.txt

@@ -1073,9 +1073,15 @@
 			specified address. The serial port must already be
 			setup and configured. Options are not yet supported.
 
+		efifb,[options]
+			Start an early, unaccelerated console on the EFI
+			memory mapped framebuffer (if available). On cache
+			coherent non-x86 systems that use system memory for
+			the framebuffer, pass the 'ram' option so that it is
+			mapped with the correct attributes.
+
 	earlyprintk=	[X86,SH,ARM,M68k,S390]
 			earlyprintk=vga
-			earlyprintk=efi
 			earlyprintk=sclp
 			earlyprintk=xen
 			earlyprintk=serial[,ttySn[,baudrate]]

arch/x86/Kconfig.debug

@@ -40,16 +40,6 @@ config EARLY_PRINTK_DBGP
 	  with klogd/syslogd or the X server. You should normally say N here,
 	  unless you want to debug such a crash. You need usb debug device.
 
-config EARLY_PRINTK_EFI
-	bool "Early printk via the EFI framebuffer"
-	depends on EFI && EARLY_PRINTK
-	select FONT_SUPPORT
-	---help---
-	  Write kernel log output directly into the EFI framebuffer.
-
-	  This is useful for kernel debugging when your machine crashes very
-	  early before the console code is initialized.
-
 config EARLY_PRINTK_USB_XDBC
 	bool "Early printk via the xHCI debug port"
 	depends on EARLY_PRINTK && PCI

arch/x86/include/asm/efi.h

@@ -170,7 +170,6 @@ static inline bool efi_runtime_supported(void)
 	return false;
 }
 
-extern struct console early_efi_console;
 extern void parse_efi_setup(u64 phys_addr, u32 data_len);
 
 extern void efifb_setup_from_dmi(struct screen_info *si, const char *opt);

arch/x86/kernel/early_printk.c

@@ -388,10 +388,6 @@ static int __init setup_early_printk(char *buf)
 		if (!strncmp(buf, "xen", 3))
 			early_console_register(&xenboot_console, keep);
 #endif
-#ifdef CONFIG_EARLY_PRINTK_EFI
-		if (!strncmp(buf, "efi", 3))
-			early_console_register(&early_efi_console, keep);
-#endif
 #ifdef CONFIG_EARLY_PRINTK_USB_XDBC
 		if (!strncmp(buf, "xdbc", 4))
 			early_xdbc_parse_parameter(buf + 4);

arch/x86/platform/efi/Makefile

@@ -3,5 +3,4 @@ OBJECT_FILES_NON_STANDARD_efi_thunk_$(BITS).o := y
 OBJECT_FILES_NON_STANDARD_efi_stub_$(BITS).o := y
 
 obj-$(CONFIG_EFI) 		+= quirks.o efi.o efi_$(BITS).o efi_stub_$(BITS).o
-obj-$(CONFIG_EARLY_PRINTK_EFI)	+= early_printk.o
 obj-$(CONFIG_EFI_MIXED)		+= efi_thunk_$(BITS).o

drivers/firmware/efi/Kconfig

@@ -198,3 +198,9 @@ config EFI_DEV_PATH_PARSER
 	bool
 	depends on ACPI
 	default n
+
+config EFI_EARLYCON
+	def_bool y
+	depends on SERIAL_EARLYCON && !ARM && !IA64
+	select FONT_SUPPORT
+	select ARCH_USE_MEMREMAP_PROT

drivers/firmware/efi/Makefile

@@ -30,5 +30,6 @@ arm-obj-$(CONFIG_EFI)			:= arm-init.o arm-runtime.o
 obj-$(CONFIG_ARM)			+= $(arm-obj-y)
 obj-$(CONFIG_ARM64)			+= $(arm-obj-y)
 obj-$(CONFIG_EFI_CAPSULE_LOADER)	+= capsule-loader.o
+obj-$(CONFIG_EFI_EARLYCON)		+= earlycon.o
 obj-$(CONFIG_UEFI_CPER_ARM)		+= cper-arm.o
 obj-$(CONFIG_UEFI_CPER_X86)		+= cper-x86.o

arch/x86/platform/efi/early_printk.c → drivers/firmware/efi/earlycon.c

+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2013 Intel Corporation; author Matt Fleming
- *
- *  This file is part of the Linux kernel, and is made available under
- *  the terms of the GNU General Public License version 2.
  */
 
 #include <linux/console.h>
@@ -10,104 +8,68 @@
 #include <linux/font.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
-#include <asm/setup.h>
+#include <linux/serial_core.h>
+#include <linux/screen_info.h>
+
+#include <asm/early_ioremap.h>
 
 static const struct font_desc *font;
 static u32 efi_x, efi_y;
-static void *efi_fb;
-static bool early_efi_keep;
+static u64 fb_base;
+static pgprot_t fb_prot;
 
-/*
- * efi earlyprintk need use early_ioremap to map the framebuffer.
- * But early_ioremap is not usable for earlyprintk=efi,keep, ioremap should
- * be used instead. ioremap will be available after paging_init() which is
- * earlier than initcall callbacks. Thus adding this early initcall function
- * early_efi_map_fb to map the whole efi framebuffer.
- */
-static __init int early_efi_map_fb(void)
+static __ref void *efi_earlycon_map(unsigned long start, unsigned long len)
 {
-	u64 base, size;
-
-	if (!early_efi_keep)
-		return 0;
-
-	base = boot_params.screen_info.lfb_base;
-	if (boot_params.screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
-		base |= (u64)boot_params.screen_info.ext_lfb_base << 32;
-	size = boot_params.screen_info.lfb_size;
-	efi_fb = ioremap(base, size);
-
-	return efi_fb ? 0 : -ENOMEM;
+	return early_memremap_prot(fb_base + start, len, pgprot_val(fb_prot));
 }
-early_initcall(early_efi_map_fb);
 
-/*
- * early_efi_map maps efi framebuffer region [start, start + len -1]
- * In case earlyprintk=efi,keep we have the whole framebuffer mapped already
- * so just return the offset efi_fb + start.
- */
-static __ref void *early_efi_map(unsigned long start, unsigned long len)
+static __ref void efi_earlycon_unmap(void *addr, unsigned long len)
 {
-	u64 base;
-
-	base = boot_params.screen_info.lfb_base;
-	if (boot_params.screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
-		base |= (u64)boot_params.screen_info.ext_lfb_base << 32;
-
-	if (efi_fb)
-		return (efi_fb + start);
-	else
-		return early_ioremap(base + start, len);
+	early_memunmap(addr, len);
 }
 
-static __ref void early_efi_unmap(void *addr, unsigned long len)
-{
-	if (!efi_fb)
-		early_iounmap(addr, len);
-}
-
-static void early_efi_clear_scanline(unsigned int y)
+static void efi_earlycon_clear_scanline(unsigned int y)
 {
 	unsigned long *dst;
 	u16 len;
 
-	len = boot_params.screen_info.lfb_linelength;
-	dst = early_efi_map(y*len, len);
+	len = screen_info.lfb_linelength;
+	dst = efi_earlycon_map(y*len, len);
 	if (!dst)
 		return;
 
 	memset(dst, 0, len);
-	early_efi_unmap(dst, len);
+	efi_earlycon_unmap(dst, len);
 }
 
-static void early_efi_scroll_up(void)
+static void efi_earlycon_scroll_up(void)
 {
 	unsigned long *dst, *src;
 	u16 len;
 	u32 i, height;
 
-	len = boot_params.screen_info.lfb_linelength;
-	height = boot_params.screen_info.lfb_height;
+	len = screen_info.lfb_linelength;
+	height = screen_info.lfb_height;
 
 	for (i = 0; i < height - font->height; i++) {
-		dst = early_efi_map(i*len, len);
+		dst = efi_earlycon_map(i*len, len);
 		if (!dst)
 			return;
 
-		src = early_efi_map((i + font->height) * len, len);
+		src = efi_earlycon_map((i + font->height) * len, len);
 		if (!src) {
-			early_efi_unmap(dst, len);
+			efi_earlycon_unmap(dst, len);
 			return;
 		}
 
 		memmove(dst, src, len);
 
-		early_efi_unmap(src, len);
-		early_efi_unmap(dst, len);
+		efi_earlycon_unmap(src, len);
+		efi_earlycon_unmap(dst, len);
 	}
 }
 
-static void early_efi_write_char(u32 *dst, unsigned char c, unsigned int h)
+static void efi_earlycon_write_char(u32 *dst, unsigned char c, unsigned int h)
 {
 	const u32 color_black = 0x00000000;
 	const u32 color_white = 0x00ffffff;
@@ -128,14 +90,14 @@ static void early_efi_write_char(u32 *dst, unsigned char c, unsigned int h)
 }
 
 static void
-early_efi_write(struct console *con, const char *str, unsigned int num)
+efi_earlycon_write(struct console *con, const char *str, unsigned int num)
 {
 	struct screen_info *si;
 	unsigned int len;
 	const char *s;
 	void *dst;
 
-	si = &boot_params.screen_info;
+	si = &screen_info;
 	len = si->lfb_linelength;
 
 	while (num) {
@@ -155,7 +117,7 @@ early_efi_write(struct console *con, const char *str, unsigned int num)
 		for (h = 0; h < font->height; h++) {
 			unsigned int n, x;
 
-			dst = early_efi_map((efi_y + h) * len, len);
+			dst = efi_earlycon_map((efi_y + h) * len, len);
 			if (!dst)
 				return;
 
@@ -164,12 +126,12 @@ early_efi_write(struct console *con, const char *str, unsigned int num)
 			x = efi_x;
 
 			while (n-- > 0) {
-				early_efi_write_char(dst + x*4, *s, h);
+				efi_earlycon_write_char(dst + x*4, *s, h);
 				x += font->width;
 				s++;
 			}
 
-			early_efi_unmap(dst, len);
+			efi_earlycon_unmap(dst, len);
 		}
 
 		num -= count;
@@ -192,27 +154,40 @@ early_efi_write(struct console *con, const char *str, unsigned int num)
 			u32 i;
 
 			efi_y -= font->height;
-			early_efi_scroll_up();
+			efi_earlycon_scroll_up();
 
 			for (i = 0; i < font->height; i++)
-				early_efi_clear_scanline(efi_y + i);
+				efi_earlycon_clear_scanline(efi_y + i);
 		}
 	}
 }
 
-static __init int early_efi_setup(struct console *con, char *options)
+static int __init efi_earlycon_setup(struct earlycon_device *device,
+				     const char *opt)
 {
 	struct screen_info *si;
 	u16 xres, yres;
 	u32 i;
 
-	si = &boot_params.screen_info;
+	if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
+		return -ENODEV;
+
+	fb_base = screen_info.lfb_base;
+	if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
+		fb_base |= (u64)screen_info.ext_lfb_base << 32;
+
+	if (opt && !strcmp(opt, "ram"))
+		fb_prot = PAGE_KERNEL;
+	else
+		fb_prot = pgprot_writecombine(PAGE_KERNEL);
+
+	si = &screen_info;
 	xres = si->lfb_width;
 	yres = si->lfb_height;
 
 	/*
-	 * early_efi_write_char() implicitly assumes a framebuffer with
-	 * 32-bits per pixel.
+	 * efi_earlycon_write_char() implicitly assumes a framebuffer with
+	 * 32 bits per pixel.
 	 */
 	if (si->lfb_depth != 32)
 		return -ENODEV;
@@ -223,18 +198,9 @@ static __init int early_efi_setup(struct console *con, char *options)
 
 	efi_y = rounddown(yres, font->height) - font->height;
 	for (i = 0; i < (yres - efi_y) / font->height; i++)
-		early_efi_scroll_up();
+		efi_earlycon_scroll_up();
 
-	/* early_console_register will unset CON_BOOT in case ,keep */
-	if (!(con->flags & CON_BOOT))
-		early_efi_keep = true;
+	device->con->write = efi_earlycon_write;
 	return 0;
 }
-
-struct console early_efi_console = {
-	.name =		"earlyefi",
-	.write =	early_efi_write,
-	.setup =	early_efi_setup,
-	.flags =	CON_PRINTBUFFER,
-	.index =	-1,
-};
+EARLYCON_DECLARE(efifb, efi_earlycon_setup);