x86/efi: Add EFI framebuffer earlyprintk support
It's incredibly difficult to diagnose early EFI boot issues without
special hardware because earlyprintk=vga doesn't work on EFI systems.
Add support for writing to the EFI framebuffer, via earlyprintk=efi,
which will actually give users a chance of providing debug output.
Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Jones <pjones@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 78d91af..0f3621e 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -59,6 +59,16 @@
with klogd/syslogd or the X server. You should normally 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 X86_PTDUMP
bool "Export kernel pagetable layout to userspace via debugfs"
depends on DEBUG_KERNEL
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 0062a01..65c6e6e 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -109,6 +109,8 @@
return IS_ENABLED(CONFIG_X86_64) == efi_enabled(EFI_64BIT);
}
+extern struct console early_efi_console;
+
#else
/*
* IF EFI is not configured, have the EFI calls return -ENOSYS.
diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index d15f575..6d3d200 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -17,6 +17,8 @@
#include <asm/mrst.h>
#include <asm/pgtable.h>
#include <linux/usb/ehci_def.h>
+#include <linux/efi.h>
+#include <asm/efi.h>
/* Simple VGA output */
#define VGABASE (__ISA_IO_base + 0xb8000)
@@ -234,6 +236,11 @@
early_console_register(&early_hsu_console, keep);
}
#endif
+#ifdef CONFIG_EARLY_PRINTK_EFI
+ if (!strncmp(buf, "efi", 3))
+ early_console_register(&early_efi_console, keep);
+#endif
+
buf++;
}
return 0;
diff --git a/arch/x86/platform/efi/Makefile b/arch/x86/platform/efi/Makefile
index 6db1cc4..b7b0b35 100644
--- a/arch/x86/platform/efi/Makefile
+++ b/arch/x86/platform/efi/Makefile
@@ -1,2 +1,3 @@
obj-$(CONFIG_EFI) += efi.o efi_$(BITS).o efi_stub_$(BITS).o
obj-$(CONFIG_ACPI_BGRT) += efi-bgrt.o
+obj-$(CONFIG_EARLY_PRINTK_EFI) += early_printk.o
diff --git a/arch/x86/platform/efi/early_printk.c b/arch/x86/platform/efi/early_printk.c
new file mode 100644
index 0000000..6599a00
--- /dev/null
+++ b/arch/x86/platform/efi/early_printk.c
@@ -0,0 +1,191 @@
+/*
+ * 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>
+#include <linux/efi.h>
+#include <linux/font.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <asm/setup.h>
+
+static const struct font_desc *font;
+static u32 efi_x, efi_y;
+
+static __init void early_efi_clear_scanline(unsigned int y)
+{
+ unsigned long base, *dst;
+ u16 len;
+
+ base = boot_params.screen_info.lfb_base;
+ len = boot_params.screen_info.lfb_linelength;
+
+ dst = early_ioremap(base + y*len, len);
+ if (!dst)
+ return;
+
+ memset(dst, 0, len);
+ early_iounmap(dst, len);
+}
+
+static __init void early_efi_scroll_up(void)
+{
+ unsigned long base, *dst, *src;
+ u16 len;
+ u32 i, height;
+
+ base = boot_params.screen_info.lfb_base;
+ len = boot_params.screen_info.lfb_linelength;
+ height = boot_params.screen_info.lfb_height;
+
+ for (i = 0; i < height - font->height; i++) {
+ dst = early_ioremap(base + i*len, len);
+ if (!dst)
+ return;
+
+ src = early_ioremap(base + (i + font->height) * len, len);
+ if (!src) {
+ early_iounmap(dst, len);
+ return;
+ }
+
+ memmove(dst, src, len);
+
+ early_iounmap(src, len);
+ early_iounmap(dst, len);
+ }
+}
+
+static void early_efi_write_char(u32 *dst, unsigned char c, unsigned int h)
+{
+ const u32 color_black = 0x00000000;
+ const u32 color_white = 0x00ffffff;
+ const u8 *src;
+ u8 s8;
+ int m;
+
+ src = font->data + c * font->height;
+ s8 = *(src + h);
+
+ for (m = 0; m < 8; m++) {
+ if ((s8 >> (7 - m)) & 1)
+ *dst = color_white;
+ else
+ *dst = color_black;
+ dst++;
+ }
+}
+
+static __init void
+early_efi_write(struct console *con, const char *str, unsigned int num)
+{
+ struct screen_info *si;
+ unsigned long base;
+ unsigned int len;
+ const char *s;
+ void *dst;
+
+ base = boot_params.screen_info.lfb_base;
+ si = &boot_params.screen_info;
+ len = si->lfb_linelength;
+
+ while (num) {
+ unsigned int linemax;
+ unsigned int h, count = 0;
+
+ for (s = str; *s && *s != '\n'; s++) {
+ if (count == num)
+ break;
+ count++;
+ }
+
+ linemax = (si->lfb_width - efi_x) / font->width;
+ if (count > linemax)
+ count = linemax;
+
+ for (h = 0; h < font->height; h++) {
+ unsigned int n, x;
+
+ dst = early_ioremap(base + (efi_y + h) * len, len);
+ if (!dst)
+ return;
+
+ s = str;
+ n = count;
+ x = efi_x;
+
+ while (n-- > 0) {
+ early_efi_write_char(dst + x*4, *s, h);
+ x += font->width;
+ s++;
+ }
+
+ early_iounmap(dst, len);
+ }
+
+ num -= count;
+ efi_x += count * font->width;
+ str += count;
+
+ if (num > 0 && *s == '\n') {
+ efi_x = 0;
+ efi_y += font->height;
+ str++;
+ num--;
+ }
+
+ if (efi_x >= si->lfb_width) {
+ efi_x = 0;
+ efi_y += font->height;
+ }
+
+ if (efi_y + font->height >= si->lfb_height) {
+ u32 i;
+
+ efi_y -= font->height;
+ early_efi_scroll_up();
+
+ for (i = 0; i < font->height; i++)
+ early_efi_clear_scanline(efi_y + i);
+ }
+ }
+}
+
+static __init int early_efi_setup(struct console *con, char *options)
+{
+ struct screen_info *si;
+ u16 xres, yres;
+ u32 i;
+
+ si = &boot_params.screen_info;
+ xres = si->lfb_width;
+ yres = si->lfb_height;
+
+ /*
+ * early_efi_write_char() implicitly assumes a framebuffer with
+ * 32-bits per pixel.
+ */
+ if (si->lfb_depth != 32)
+ return -ENODEV;
+
+ font = get_default_font(xres, yres, -1, -1);
+ if (!font)
+ return -ENODEV;
+
+ efi_y = rounddown(yres, font->height) - font->height;
+ for (i = 0; i < (yres - efi_y) / font->height; i++)
+ early_efi_scroll_up();
+
+ return 0;
+}
+
+struct console early_efi_console = {
+ .name = "earlyefi",
+ .write = early_efi_write,
+ .setup = early_efi_setup,
+ .flags = CON_PRINTBUFFER,
+ .index = -1,
+};