x86: Add support for booting Linux using the 32 bit boot protocol

This change conditionally modifies the zboot command so that it can use the
32 bit boot protocol. This is necessary because the 16 bit realmode entry
point assumes that it can call BIOS services which neither coreboot nor
u-boot provide.

Signed-off-by: Gabe Black <gabeblack@chromium.org>

arch/x86/include/asm/zimage.h

@@ -24,6 +24,8 @@
 #ifndef _ASM_ZIMAGE_H_
 #define _ASM_ZIMAGE_H_
 
+#include <asm/e820.h>
+
 /* linux i386 zImage/bzImage header. Offsets relative to
  * the start of the image */
 
@@ -44,10 +46,13 @@
 #define BZIMAGE_LOAD_ADDR  0x100000
 #define ZIMAGE_LOAD_ADDR   0x10000
 
+/* Implementation defined function to install an e820 map. */
+unsigned install_e820_map(unsigned max_entries, struct e820entry *);
+
 void *load_zimage(char *image, unsigned long kernel_size,
 		  unsigned long initrd_addr, unsigned long initrd_size,
-		  int auto_boot);
+		  int auto_boot, void **load_address);
 
-void boot_zimage(void *setup_base);
+void boot_zimage(void *setup_base, void *load_address);
 
 #endif

arch/x86/lib/bootm.c

@@ -38,6 +38,7 @@ int do_bootm_linux(int flag, int argc, char * const argv[],
 	void		*base_ptr = NULL;
 	ulong		os_data, os_len;
 	image_header_t	*hdr;
+	void		*load_address;
 
 #if defined(CONFIG_FIT)
 	const void	*data;
@@ -75,7 +76,8 @@ int do_bootm_linux(int flag, int argc, char * const argv[],
 
 #ifdef CONFIG_CMD_ZBOOT
 	base_ptr = load_zimage((void *)os_data, os_len,
-			images->rd_start, images->rd_end - images->rd_start, 0);
+			images->rd_start, images->rd_end - images->rd_start,
+			0, &load_address);
 #endif
 
 	if (NULL == base_ptr) {
@@ -92,7 +94,7 @@ int do_bootm_linux(int flag, int argc, char * const argv[],
 	/* we assume that the kernel is in place */
 	printf("\nStarting kernel ...\n\n");
 
-	boot_zimage(base_ptr);
+	boot_zimage(base_ptr, load_address);
 	/* does not return */
 
 error:

arch/x86/lib/zimage.c

@@ -52,6 +52,16 @@
 
 #define COMMAND_LINE_SIZE	2048
 
+unsigned generic_install_e820_map(unsigned max_entries,
+				  struct e820entry *entries)
+{
+	return 0;
+}
+
+unsigned install_e820_map(unsigned max_entries,
+			  struct e820entry *entries)
+	__attribute__((weak, alias("generic_install_e820_map")));
+
 static void build_command_line(char *command_line, int auto_boot)
 {
 	char *env_command_line;
@@ -81,13 +91,12 @@ static void build_command_line(char *command_line, int auto_boot)
 
 void *load_zimage(char *image, unsigned long kernel_size,
 		  unsigned long initrd_addr, unsigned long initrd_size,
-		  int auto_boot)
+		  int auto_boot, void **load_address)
 {
 	struct boot_params *setup_base;
 	int setup_size;
 	int bootproto;
 	int big_image;
-	void *load_address;
 
 	struct boot_params *params = (struct boot_params *)image;
 	struct setup_header *hdr = &params->hdr;
@@ -134,14 +143,23 @@ void *load_zimage(char *image, unsigned long kernel_size,
 
 	/* Determine load address */
 	if (big_image)
-		load_address = (void *)BZIMAGE_LOAD_ADDR;
+		*load_address = (void *)BZIMAGE_LOAD_ADDR;
 	else
-		load_address = (void *)ZIMAGE_LOAD_ADDR;
+		*load_address = (void *)ZIMAGE_LOAD_ADDR;
 
+#if defined CONFIG_ZBOOT_32
+	printf("Building boot_params at 0x%8.8lx\n", (ulong)setup_base);
+	memset(setup_base, 0, sizeof(*setup_base));
+	setup_base->hdr = params->hdr;
+
+	setup_base->e820_entries = install_e820_map(
+		ARRAY_SIZE(setup_base->e820_map), setup_base->e820_map);
+#else
 	/* load setup */
 	printf("Moving Real-Mode Code to 0x%8.8lx (%d bytes)\n",
 	       (ulong)setup_base, setup_size);
 	memmove(setup_base, image, setup_size);
+#endif
 
 	printf("Using boot protocol version %x.%02x\n",
 	       (bootproto & 0xff00) >> 8, bootproto & 0xff);
@@ -180,7 +198,7 @@ void *load_zimage(char *image, unsigned long kernel_size,
 
 		if (hdr->setup_sects >= 15) {
 			printf("Linux kernel version %s\n",
-			       (char *)setup_base +
+			       (char *)params +
 			       hdr->kernel_version + 0x200);
 		} else {
 			printf("Setup Sectors < 15 - "
@@ -235,17 +253,36 @@ void *load_zimage(char *image, unsigned long kernel_size,
 	build_command_line((char *)setup_base + COMMAND_LINE_OFFSET, auto_boot);
 
 	printf("Loading %czImage at address 0x%08x (%ld bytes)\n",
-	       big_image ? 'b' : ' ', (u32)load_address, kernel_size);
+	       big_image ? 'b' : ' ', (u32)*load_address, kernel_size);
-
 
-	memmove(load_address, image + setup_size, kernel_size);
+	memmove(*load_address, image + setup_size, kernel_size);
 
 	/* ready for booting */
 	return setup_base;
 }
 
-void boot_zimage(void *setup_base)
+void boot_zimage(void *setup_base, void *load_address)
 {
+	printf("\nStarting kernel ...\n\n");
+
+#if defined CONFIG_ZBOOT_32
+	/*
+	 * Set %ebx, %ebp, and %edi to 0, %esi to point to the boot_params
+	 * structure, and then jump to the kernel. We assume that %cs is
+	 * 0x10, 4GB flat, and read/execute, and the data segments are 0x18,
+	 * 4GB flat, and read/write. U-boot is setting them up that way for
+	 * itself in arch/i386/cpu/cpu.c.
+	 */
+	__asm__ __volatile__ (
+	"movl $0, %%ebp		\n"
+	"cli			\n"
+	"jmp %[kernel_entry]	\n"
+	:: [kernel_entry]"a"(load_address),
+	   [boot_params] "S"(setup_base),
+	   "b"(0), "D"(0)
+	:  "%ebp"
+	);
+#else
 	struct pt_regs regs;
 
 	memset(&regs, 0, sizeof(struct pt_regs));
@@ -256,12 +293,14 @@ void boot_zimage(void *setup_base)
 	regs.eflags = 0;
 	enter_realmode(((u32)setup_base + SETUP_START_OFFSET) >> 4, 0,
 		       &regs, &regs);
+#endif
 }
 
 int do_zboot(cmd_tbl_t *cmdtp, int flag, int argc, char *const argv[])
 {
 	void *base_ptr;
 	void *bzImage_addr = NULL;
+	void *load_address;
 	char *s;
 	ulong bzImage_size = 0;
 
@@ -285,7 +324,8 @@ int do_zboot(cmd_tbl_t *cmdtp, int flag, int argc, char *const argv[])
 		bzImage_size = simple_strtoul(argv[2], NULL, 16);
 
 	/* Lets look for */
-	base_ptr = load_zimage(bzImage_addr, bzImage_size, 0, 0, 0);
+	base_ptr = load_zimage(bzImage_addr, bzImage_size, 0, 0, 0,
+		&load_address);
 
 	if (!base_ptr) {
 		printf("## Kernel loading failed ...\n");
@@ -295,9 +335,7 @@ int do_zboot(cmd_tbl_t *cmdtp, int flag, int argc, char *const argv[])
 		       (u32)base_ptr);
 
 		/* we assume that the kernel is in place */
-		printf("\nStarting kernel ...\n\n");
+		boot_zimage(base_ptr, load_address);
-
-		boot_zimage(base_ptr);
 		/* does not return */
 	}