gfxboot.c32syslinux-3.84-pre5

Ok, here is the first try to turn the gfxboot wrapper into a com32 module. I
had to extend the interface to the gfxboot core a bit to get it working. So
it works only with latest gfxboot from

git://gitorious.org/gfxboot/gfxboot.git

Steffen

Signed-off-by: Sebastian Herbszt <herbszt@gmx.de>

5 files changed, 1042 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index 76abff51..c964e8d1 100644
--- a/Makefile
+++ b/Makefile
@@ -32,7 +32,7 @@ include $(topdir)/MCONFIG
 # List of module objects that should be installed for all derivatives
 MODULES = memdisk/memdisk memdump/memdump.com modules/*.com \
 	com32/menu/*.c32 com32/modules/*.c32 com32/mboot/*.c32 \
-	com32/hdt/*.c32 com32/rosh/*.c32
+	com32/hdt/*.c32 com32/rosh/*.c32 com32/gfxboot/*.c32
 
 # syslinux.exe is BTARGET so as to not require everyone to have the
 # mingw suite installed
diff --git a/com32/Makefile b/com32/Makefile
index 4a584853..69a125e6 100644
--- a/com32/Makefile
+++ b/com32/Makefile
@@ -1,3 +1,3 @@
-SUBDIRS = lib gpllib libutil modules mboot menu samples rosh cmenu hdt
+SUBDIRS = lib gpllib libutil modules mboot menu samples rosh cmenu hdt gfxboot
 all tidy dist clean spotless install:
 	set -e; for d in $(SUBDIRS); do $(MAKE) -C $$d $@; done
diff --git a/com32/gfxboot/Makefile b/com32/gfxboot/Makefile
new file mode 100644
index 00000000..2affcdea
--- /dev/null
+++ b/com32/gfxboot/Makefile
@@ -0,0 +1,44 @@
+## -----------------------------------------------------------------------
+##
+##   Copyright 2001-2009 H. Peter Anvin - All Rights Reserved
+##   Copyright 2009 Intel Corporation; author: H. Peter Anvin
+##
+##   This program is free software; you can redistribute it and/or modify
+##   it under the terms of the GNU General Public License as published by
+##   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+##   Boston MA 02111-1307, USA; either version 2 of the License, or
+##   (at your option) any later version; incorporated herein by reference.
+##
+## -----------------------------------------------------------------------
+
+topdir = ../..
+include ../MCONFIG
+
+MODULES	  = gfxboot.c32
+
+all: $(MODULES)
+
+gfxboot.elf : gfxboot.o realmode_callback.o $(LIBS) $(C_LIBS)
+	$(LD) $(LDFLAGS) -o $@ $^
+
+realmode_callback.o: realmode_callback.asm
+	nasm -f bin -O99 -o $*.tmp -l $*.lst $<
+	objcopy -B i386 -I binary -O elf32-i386 \
+	  --redefine-sym _binary_$*_tmp_start=$*_start \
+	  --redefine-sym _binary_$*_tmp_end=$*_end \
+	  --strip-symbol _binary_$*_tmp_size \
+	  $*.tmp $@
+
+tidy dist:
+	rm -f *.o *.lo *.a *.lst *.elf .*.d *.tmp
+
+clean: tidy
+	rm -f *.lnx
+
+spotless: clean
+	rm -f *.lss *.c32 *.com
+	rm -f *~ \#*
+
+install:
+
+-include .*.d
diff --git a/com32/gfxboot/gfxboot.c b/com32/gfxboot/gfxboot.c
new file mode 100644
index 00000000..e1b865a1
--- /dev/null
+++ b/com32/gfxboot/gfxboot.c
@@ -0,0 +1,806 @@
+/*
+ *
+ * gfxboot.c
+ *
+ * A com32 module to load gfxboot graphics.
+ *
+ * Copyright (c) 2009 Steffen Winterfeldt.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, Inc., 53 Temple Place Ste 330, Boston MA
+ * 02111-1307, USA; either version 2 of the License, or (at your option) any
+ * later version; incorporated herein by reference.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include <syslinux/loadfile.h>
+#include <syslinux/config.h>
+#include <syslinux/linux.h>
+#include <syslinux/boot.h>
+#include <console.h>
+#include <com32.h>
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+#define MAX_CONFIG_LINE_LEN	2048
+#define MAX_CMDLINE_LEN		2048
+
+// buffer for realmode callback
+// must be at least block size; can in theory be larger than 4k, but there's
+// not enough space left
+#define REALMODE_BUF_SIZE	4096
+
+// gfxboot working memory in MB
+#define	GFX_MEMORY_SIZE		7
+
+// read chunk size for progress bar
+#define CHUNK_SIZE	(64 << 10)
+
+// callback function numbers
+#define GFX_CB_INIT		0
+#define GFX_CB_DONE		1
+#define GFX_CB_INPUT		2
+#define GFX_CB_MENU_INIT	3
+#define GFX_CB_INFOBOX_INIT	4
+#define GFX_CB_INFOBOX_DONE	5
+#define GFX_CB_PROGRESS_INIT	6
+#define GFX_CB_PROGRESS_DONE	7
+#define GFX_CB_PROGRESS_UPDATE	8
+#define GFX_CB_PROGRESS_LIMIT	9		// unused
+#define GFX_CB_PASSWORD_INIT	10
+#define GFX_CB_PASSWORD_DONE	11
+
+// real mode code chunk, will be placed into bounce buffer
+extern void realmode_callback_start, realmode_callback_end;
+
+// gets in the way
+#undef linux
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// gfxboot config data (64 bytes)
+typedef struct __attribute__ ((packed)) {
+  uint8_t bootloader;		//  0: boot loader type (0: lilo, 1: syslinux, 2: grub)
+  uint8_t sector_shift;		//  1: sector shift
+  uint8_t media_type;		//  2: media type (0: disk, 1: floppy, 2: cdrom)
+  uint8_t failsafe;		//  3: turn on failsafe mode (bitmask)
+				//    0: SHIFT pressed
+				//    1: skip gfxboot
+				//    2: skip monitor detection
+  uint8_t sysconfig_size;	//  4: size of sysconfig data
+  uint8_t boot_drive;		//  5: BIOS boot drive
+  uint16_t callback;		//  6: offset to callback handler
+  uint16_t bootloader_seg;	//  8: code/data segment used by bootloader; must follow gfx_callback
+  uint16_t serial_port;		// 10: syslinux initialized serial port from 'serial' option
+  uint32_t user_info_0;		// 12: data for info box
+  uint32_t user_info_1;		// 16: data for info box
+  uint32_t bios_mem_size;	// 20: BIOS memory size (in bytes)
+  uint16_t xmem_0;		// 24: extended mem area 0 (start:size in MB; 12:4 bits) - obsolete
+  uint16_t xmem_1;		// 26: extended mem area 1 - obsolete
+  uint16_t xmem_2;		// 28: extended mem area 2 - obsolete
+  uint16_t xmem_3;		// 30: extended mem area 3 - obsolete
+  uint32_t file;		// 32: start of gfx file
+  uint32_t archive_start;	// 36: start of cpio archive
+  uint32_t archive_end;		// 40: end of cpio archive
+  uint32_t mem0_start;		// 44: low free memory start
+  uint32_t mem0_end;		// 48: low free memory end
+  uint32_t xmem_start;		// 52: extended mem start
+  uint32_t xmem_end;		// 56: extended mem end
+  uint16_t features;		// 60: feature flags returned by GFX_CB_INIT
+  				//    0: GFX_CB_MENU_INIT accepts 32 bit addresses
+  				//    1: knows about xmem_start, xmem_end
+  uint16_t reserved_1;		// 62:
+} gfx_config_t;
+
+
+// gfxboot menu description (18 bytes)
+typedef struct __attribute__ ((packed)) {
+  uint16_t entries;
+  char *default_entry;
+  char *label_list;
+  uint16_t label_size;
+  char *arg_list;
+  uint16_t arg_size;
+} gfx_menu_t;
+
+
+// menu description
+typedef struct menu_s {
+  struct menu_s *next;
+  char *label;
+  char *kernel;
+  char *linux;
+  char *localboot;
+  char *initrd;
+  char *append;
+  char *ipappend;
+} menu_t;
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+gfx_config_t gfx_config;
+gfx_menu_t gfx_menu;
+
+menu_t *menu;
+menu_t *menu_default;
+
+struct {
+  uint32_t jmp_table[12];
+  uint16_t code_seg;
+  char fname_buf[64];
+} gfx;
+
+void *lowmem_buf;
+unsigned lowmem_buf_size;
+
+int timeout;
+
+char cmdline[MAX_CMDLINE_LEN];
+
+void *save_buf;
+unsigned save_buf_size;
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void show_message(char *file);
+char *get_config_file_name(void);
+char *skip_spaces(char *s);
+char *skip_nonspaces(char *s);
+void chop_line(char *s);
+int read_config_file(void);
+unsigned magic_ok(unsigned char *buf, unsigned *code_size);
+unsigned find_file(unsigned char *buf, unsigned len, unsigned *gfx_file_start, unsigned *file_len, unsigned *code_size);
+int gfx_init(char *file);
+int gfx_menu_init(void);
+void gfx_done(void);
+int gfx_input(void);
+ssize_t save_read(int fd, void *buf, size_t size);
+void *load_one(char *file, ssize_t *file_size);
+void boot(void);
+void boot_entry(menu_t *menu_ptr, char *arg);
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+int main(int argc, char **argv)
+{
+  int menu_index;
+  enum syslinux_filesystem syslinux_id;
+  com32sys_t r;
+
+  openconsole(&dev_stdcon_r, &dev_stdcon_w);
+
+  syslinux_id = syslinux_version()->filesystem;
+
+  lowmem_buf = __com32.cs_bounce;
+  lowmem_buf_size = __com32.cs_bounce_size;
+
+  r.eax.l = 0x0a;	// Get Derivative-Specific Information
+  r.ecx.l = 9;
+  __intcall(0x22, &r, &r);
+  gfx_config.sector_shift = (uint8_t) r.ecx.l;
+  gfx_config.boot_drive = (uint8_t) r.edx.l;
+
+  if(syslinux_id == SYSLINUX_FS_PXELINUX) {
+    gfx_config.sector_shift = 11;
+    gfx_config.boot_drive = 0;
+  }
+
+  gfx_config.bootloader = 1;
+  gfx_config.sysconfig_size = sizeof gfx_config;
+  gfx_config.bootloader_seg = 0;	// apparently not needed
+
+  save_buf_size = lowmem_buf_size;
+  save_buf = malloc(save_buf_size);
+
+  if(argc < 2) {
+    printf("Usage: gfxboot.c32 bootlogo_file [message_file]\n");
+    if(argc > 2) show_message(argv[2]);
+
+    return 0;
+  }
+
+  if(read_config_file()) {
+    printf("Error reading config file\n");
+    if(argc > 2) show_message(argv[2]);
+
+    return 0;
+  }
+
+  if(gfx_init(argv[1])) {
+    printf("Error setting up gfxboot\n");
+    if(argc > 2) show_message(argv[2]);
+
+    return 0;
+  }
+
+  gfx_menu_init();
+
+  for(;;) {
+    menu_index = gfx_input();
+
+    // abort gfx, return to text mode prompt
+    if(menu_index == -1) {
+      gfx_done();
+      break;
+    }
+
+    // does not return if it succeeds
+    boot();
+  }
+
+  if(argc > 2) show_message(argv[2]);
+
+  return 0;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void show_message(char *file)
+{
+  int c;
+  FILE *f;
+
+  if(!(f = fopen(file, "r"))) return;
+
+  while((c = getc(f)) != EOF) {
+    if(c < ' ' && c != '\n' && c != '\t') continue;
+    printf("%c", c);
+  }
+
+  fclose(f);
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+char *skip_spaces(char *s)
+{
+  while(*s && (*s == ' ' || *s == '\t')) s++;
+
+  return s;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+char *skip_nonspaces(char *s)
+{
+  while(*s && *s != ' ' && *s != '\t') s++;
+
+  return s;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void chop_line(char *s)
+{
+  int i = strlen(s);
+
+  if(!i) return;
+
+  while(--i >= 0) {
+    if(s[i] == ' ' || s[i] == '\t' || s[i] == '\n') {
+      s[i] = 0;
+    }
+    else {
+      break;
+    }
+  }
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// Read and parse syslinux config file.
+//
+// return:
+//   0: ok, 1: error
+//
+int read_config_file(void)
+{
+  FILE *f;
+  char *s, *t, buf[MAX_CONFIG_LINE_LEN];
+  unsigned u, menu_idx = 0, label_size = 0, append_size = 0;
+  menu_t *menu_ptr = NULL, **menu_next = &menu;
+
+  menu_default = calloc(1, sizeof *menu_default);
+
+  if(!(f = fopen(syslinux_config_file(), "r"))) return 1;
+
+  while((s = fgets(buf, sizeof buf, f))) {
+    chop_line(s);
+    s = skip_spaces(s);
+    if(!*s || *s == '#') continue;
+    t = skip_nonspaces(s);
+    if(*t) *t++ = 0;
+    t = skip_spaces(t);
+
+    if(!strcmp(s, "timeout")) {
+      timeout = atoi(t);
+      continue;
+    }
+
+    if(!strcmp(s, "default")) {
+      menu_default->label = strdup(t);
+      u = strlen(t);
+      if(u > label_size) label_size = u;
+      continue;
+    }
+
+    if(!strcmp(s, "label")) {
+      menu_ptr = *menu_next = calloc(1, sizeof **menu_next);
+      menu_next = &menu_ptr->next;
+      menu_idx++;
+      menu_ptr->label = strdup(t);
+      u = strlen(t);
+      if(u > label_size) label_size = u;
+      continue;
+    }
+
+    if(!strcmp(s, "kernel") && menu_ptr) {
+      menu_ptr->kernel = strdup(t);
+      continue;
+    }
+
+    if(!strcmp(s, "linux") && menu_ptr) {
+      menu_ptr->linux = strdup(t);
+      continue;
+    }
+
+    if(!strcmp(s, "localboot") && menu_ptr) {
+      menu_ptr->localboot = strdup(t);
+      continue;
+    }
+
+    if(!strcmp(s, "initrd") && menu_ptr) {
+      menu_ptr->initrd = strdup(t);
+      continue;
+    }
+
+    if(!strcmp(s, "append")) {
+      (menu_ptr ?: menu_default)->append = strdup(t);
+      u = strlen(t);
+      if(u > append_size) append_size = u;
+      continue;
+    }
+
+    if(!strcmp(s, "ipappend")) {
+      (menu_ptr ?: menu_default)->ipappend = strdup(t);
+      continue;
+    }
+  }
+
+  fclose(f);
+
+  // final '\0'
+  label_size++;
+  append_size++;
+
+  gfx_menu.entries = menu_idx;
+  gfx_menu.label_size = label_size;
+  gfx_menu.arg_size = append_size;
+
+  gfx_menu.default_entry = menu_default->label;
+  if(!gfx_menu.default_entry && menu) {
+    gfx_menu.default_entry = menu->label;
+  }
+
+  gfx_menu.label_list = calloc(menu_idx, label_size);
+  gfx_menu.arg_list = calloc(menu_idx, append_size);
+
+  for(u = 0, menu_ptr = menu; menu_ptr; menu_ptr = menu_ptr->next, u++) {
+    if(!menu_ptr->append) menu_ptr->append = menu_default->append;
+    if(!menu_ptr->ipappend) menu_ptr->ipappend = menu_default->ipappend;
+
+    if(menu_ptr->label) strcpy(gfx_menu.label_list + u * label_size, menu_ptr->label);
+    if(menu_ptr->append) strcpy(gfx_menu.arg_list + u * append_size, menu_ptr->append);
+  }
+
+  return 0;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// Check header and return code start offset.
+//
+unsigned magic_ok(unsigned char *buf, unsigned *code_size)
+{
+  if(
+    *(unsigned *) buf == 0x0b2d97f00 &&		// magic id
+    (buf[4] == 8)				// version 8
+  ) {
+    *code_size = *(unsigned *) (buf + 12);
+    return *(unsigned *) (buf + 8);
+  }
+
+  return 0;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// Search cpio archive for gfx file.
+//
+unsigned find_file(unsigned char *buf, unsigned len, unsigned *gfx_file_start, unsigned *file_len, unsigned *code_size)
+{
+  unsigned i, fname_len, code_start = 0;
+
+  *gfx_file_start = 0;
+  *code_size = 0;
+
+  for(i = 0; i < len;) {
+    if((len - i) >= 0x1a && (buf[i] + (buf[i + 1] << 8)) == 0x71c7) {
+      fname_len = *(unsigned short *) (buf + i + 20);
+      *file_len = *(unsigned short *) (buf + i + 24) + (*(unsigned short *) (buf + i + 22) << 16);
+      i += 26 + fname_len;
+      i = ((i + 1) & ~1);
+      if((code_start = magic_ok(buf + i, code_size))) {
+        *gfx_file_start = i;
+        return code_start;
+      }
+      i += *file_len;
+      i = ((i + 1) & ~1);
+    }
+    else {
+      break;
+    }
+  }
+
+  return code_start;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// Initialize gfxboot code.
+//
+// return:
+//   0: ok, 1: error
+//
+int gfx_init(char *file)
+{
+  size_t archive_size = 0;
+  void *archive;
+  unsigned code_start, code_size, file_start, file_len, u;
+  com32sys_t r;
+  void *lowmem = lowmem_buf;
+  unsigned lowmem_size = lowmem_buf_size;
+
+  printf("Loading %s...\n", file);
+  if(loadfile(file, &archive, &archive_size)) return 1;
+
+  if(!archive_size) return 1;
+
+  // printf("%s: %d\n", file, archive_size);
+
+  gfx_config.archive_start = (uint32_t) archive;
+  gfx_config.archive_end = gfx_config.archive_start + archive_size;
+
+  // locate file inside cpio archive
+  if(!(code_start = find_file(archive, archive_size, &file_start, &file_len, &code_size))) {
+    printf("%s: invalid file format\n", file);
+    return 1;
+  }
+
+#if 0
+  printf(
+    "code_start = 0x%x, code_size = 0x%x\n"
+    "archive_start = 0x%x, archive size = 0x%x\n"
+    "file_start = 0x%x, file_len = 0x%x\n",
+    code_start, code_size,
+    gfx_config.archive_start, archive_size,
+    file_start, file_len
+  );
+#endif
+
+  gfx_config.file = gfx_config.archive_start + file_start;
+
+  u = &realmode_callback_end - &realmode_callback_start;
+  u = (u + REALMODE_BUF_SIZE + 0xf) & ~0xf;
+
+  if(u + code_size > lowmem_size) {
+    printf("bounce buffer too small: size %u, needed %u\n", lowmem_size, u + code_size);
+    return 1;
+  }
+
+  memcpy(lowmem + REALMODE_BUF_SIZE, &realmode_callback_start, &realmode_callback_end - &realmode_callback_start);
+
+  // fill in buffer size and location
+  *(uint16_t *) (lowmem + REALMODE_BUF_SIZE) = REALMODE_BUF_SIZE;
+  *(uint16_t *) (lowmem + REALMODE_BUF_SIZE + 2) = (uint32_t) lowmem >> 4;
+
+  gfx_config.bootloader_seg = ((uint32_t) lowmem + REALMODE_BUF_SIZE) >> 4;
+  gfx_config.callback = 4;	// start address
+
+  lowmem += u;
+  lowmem_size -= u;
+
+  memcpy(lowmem, archive + file_start + code_start, code_size);
+
+  gfx_config.mem0_start = (uint32_t) lowmem + code_size;
+  gfx_config.mem0_end = (uint32_t) lowmem + lowmem_size;
+  // align a bit
+  gfx_config.mem0_start = (gfx_config.mem0_start + 0xf) & ~0xf;
+
+  gfx_config.xmem_start = (uint32_t) malloc(GFX_MEMORY_SIZE << 20);
+  if(gfx_config.xmem_start) {
+    gfx_config.xmem_end = gfx_config.xmem_start + (GFX_MEMORY_SIZE << 20);
+  }
+
+  // fake; not used anyway
+  gfx_config.bios_mem_size = 256 << 20;
+
+  gfx.code_seg = (uint32_t) lowmem >> 4;
+
+  for(u = 0; u < sizeof gfx.jmp_table / sizeof *gfx.jmp_table; u++) {
+    gfx.jmp_table[u] = (gfx.code_seg << 16) + *(uint16_t *) (lowmem + 2 * u);
+  }
+
+#if 0
+  for(u = 0; u < sizeof gfx.jmp_table / sizeof *gfx.jmp_table; u++) {
+    printf("%d: 0x%08x\n", u, gfx.jmp_table[u]);
+  }
+#endif
+
+  // we are ready to start
+
+  r.esi.l = (uint32_t) &gfx_config;
+  __farcall(gfx.code_seg, gfx.jmp_table[GFX_CB_INIT], &r, &r);
+
+  if((r.eflags.l & EFLAGS_CF)) {
+    printf("graphics initialization failed\n");
+
+    return 1;
+  }
+
+  if((gfx_config.features & 3) != 3) {
+    gfx_done();
+
+    printf("%s: boot graphics code too old, please use newer version\n", file);
+
+    return 1;
+  }
+
+
+  return 0;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+int gfx_menu_init()
+{
+  com32sys_t r;
+
+  r.esi.l = (uint32_t) &gfx_menu;
+  __farcall(gfx.code_seg, gfx.jmp_table[GFX_CB_MENU_INIT], &r, &r);
+
+  return 0;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void gfx_done()
+{
+  com32sys_t r;
+
+  __farcall(gfx.code_seg, gfx.jmp_table[GFX_CB_DONE], &r, &r);
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// Run gfxboot main loop.
+//
+// return:
+//   boot menu index (-1: go to text mode prompt)
+//
+int gfx_input()
+{
+  com32sys_t r;
+
+  r.edi.l = (uint32_t) cmdline;
+  r.ecx.l = sizeof cmdline;
+  r.eax.l = timeout * 182 / 100;
+  timeout = 0;		// use timeout only first time
+  __farcall(gfx.code_seg, gfx.jmp_table[GFX_CB_INPUT], &r, &r);
+  if((r.eflags.l & EFLAGS_CF)) r.eax.l = 1;
+
+  if(r.eax.l == 1) return -1;
+
+  return r.ebx.l;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// Like read(2) but preserve bounce buffer.
+//
+ssize_t save_read(int fd, void *buf, size_t size)
+{
+  ssize_t i;
+
+  memcpy(save_buf, lowmem_buf, save_buf_size);
+  i = read(fd, buf, size);
+  memcpy(lowmem_buf, save_buf, save_buf_size);
+
+  return i;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// Read file and update progress bar.
+//
+void *load_one(char *file, ssize_t *file_size)
+{
+  int fd;
+  void *buf = NULL;
+  struct stat sbuf;
+  ssize_t size = 0, cur, i;
+  com32sys_t r;
+
+  *file_size = 0;
+
+  if((fd = open(file, O_RDONLY)) == -1) {
+    printf("%s: file not found\n", file);
+    return buf;
+  }
+
+  if(!fstat(fd, &sbuf) && S_ISREG(sbuf.st_mode)) size = sbuf.st_size;
+
+  i = 0;
+
+  if(size) {
+    buf = malloc(size);
+    for(i = 1, cur = 0 ; cur < size && i > 0; cur += i) {
+      i = save_read(fd, buf + cur, CHUNK_SIZE);
+      r.eax.l = i >> gfx_config.sector_shift;
+      __farcall(gfx.code_seg, gfx.jmp_table[GFX_CB_PROGRESS_UPDATE], &r, &r);
+    }
+  }
+  else {
+    do {
+      buf = realloc(buf, size + CHUNK_SIZE);
+      i = save_read(fd, buf + size, CHUNK_SIZE);
+      size += i;
+      r.eax.l = i >> gfx_config.sector_shift;
+      __farcall(gfx.code_seg, gfx.jmp_table[GFX_CB_PROGRESS_UPDATE], &r, &r);
+    } while(i > 0);
+  }
+
+  close(fd);
+
+  if(i == -1) {
+    free(buf);
+    buf = NULL;
+    size = 0;
+  }
+
+  *file_size = size;
+
+  return buf;
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// Locate menu entry and boot.
+//
+void boot()
+{
+  char *label, *arg, *s;
+  menu_t *menu_ptr;
+
+  label = skip_spaces(cmdline);
+  arg = skip_spaces(s = skip_nonspaces(label));
+  *s = 0;
+
+  for(menu_ptr = menu; menu_ptr; menu_ptr = menu_ptr->next) {
+    if(menu_ptr->label && !strcmp(menu_ptr->label, label)) break;
+  }
+
+  boot_entry(menu_ptr, arg);
+}
+
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// Load & run kernel.
+//
+// Returns only on error.
+//
+void boot_entry(menu_t *menu_ptr, char *arg)
+{
+  void *kernel, *initrd_buf;
+  ssize_t kernel_size = 0, initrd_size = 0;
+  struct initramfs *initrd = NULL;
+  char *file, *cmd_buf;
+  int fd;
+  struct stat sbuf;
+  com32sys_t r;
+  char *s, *s0, *t, *initrd_arg;
+
+  if(!menu_ptr) return;
+
+  if(menu_ptr->localboot) {
+    gfx_done();
+    syslinux_local_boot(atoi(arg));
+
+    return;
+  }
+
+  file = menu_ptr->kernel;
+  if(!file) file = menu_ptr->linux;
+  if(!file) return;
+
+  // first, load kernel
+
+  r.eax.l = 0;		// kernel size in sectors
+
+  if((fd = open(file, O_RDONLY)) >= 0) {
+    if(!fstat(fd, &sbuf) && S_ISREG(sbuf.st_mode)) r.eax.l = sbuf.st_size >> gfx_config.sector_shift;
+    close(fd);
+  }
+
+  r.esi.l = (uint32_t) file;
+  __farcall(gfx.code_seg, gfx.jmp_table[GFX_CB_PROGRESS_INIT], &r, &r);
+
+  kernel = load_one(file, &kernel_size);
+
+  if(!kernel) {
+    gfx_done();
+    printf("%s: read error\n", file);
+    return;
+  }
+
+  if(kernel_size < 1024 || *(uint32_t *) (kernel + 0x202) != 0x53726448) {
+    // not a linux kernel
+    gfx_done();
+    asprintf(&cmd_buf, "%s %s", menu_ptr->label, arg);
+    syslinux_run_command(cmd_buf);
+    return;
+  }
+
+  // printf("kernel = %p, size = %d\n", kernel, kernel_size);
+
+  // parse cmdline for "initrd" option
+
+  initrd_arg = menu_ptr->initrd;
+
+  s = s0 = strdup(arg);
+
+  while(*s && strncmp(s, "initrd=", sizeof "initrd=" - 1)) {
+    s = skip_spaces(skip_nonspaces(s));
+  }
+
+  if(*s) {
+    s += sizeof "initrd=" - 1;
+    *skip_nonspaces(s) = 0;
+    initrd_arg = s;
+  }
+
+  if(initrd_arg) {
+    initrd = initramfs_init();
+
+    while((t = strsep(&s, ","))) {
+      initrd_buf = load_one(t, &initrd_size);
+
+      if(!initrd_buf) {
+        printf("%s: read error\n", t);
+        free(s0);
+        return;
+      }
+
+      initramfs_add_data(initrd, initrd_buf, initrd_size, initrd_size, 4);
+
+      // printf("initrd = %p, size = %d\n", initrd_buf, initrd_size);
+    }
+  }
+
+  free(s0);
+
+  __farcall(gfx.code_seg, gfx.jmp_table[GFX_CB_PROGRESS_DONE], &r, &r);
+
+  syslinux_boot_linux(kernel, kernel_size, initrd, arg);
+}
+
+
diff --git a/com32/gfxboot/realmode_callback.asm b/com32/gfxboot/realmode_callback.asm
new file mode 100644
index 00000000..fb5461d9
--- /dev/null
+++ b/com32/gfxboot/realmode_callback.asm
@@ -0,0 +1,190 @@
+		bits 16
+
+		section .text
+
+		; must be filled in
+f_buf_size	dw 0
+f_buf_seg	dw 0
+
+
+; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+gfx_cb:
+		push cs
+		pop ds
+
+		cmp al,cb_len
+		jae gfx_cb_80
+
+		movzx bx,al
+		add bx,bx
+		call word [bx+cb_table]
+		jmp gfx_cb_90
+
+gfx_cb_80:
+		mov al,0ffh
+gfx_cb_90:
+		retf
+
+
+; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+; Return status info.
+;
+; return:
+;  edx		filename buffer (64 bytes)
+;
+cb_status:
+		mov edx,cs
+		shl edx,4
+		add edx,f_name
+		xor al,al
+		ret
+
+
+; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+; Open file.
+;
+; return:
+;    al		0: ok, 1: file not found
+;   ecx		file length (al = 0)
+;
+cb_fopen:
+		mov si,f_name
+		push ds
+		pop es
+		mov ax,6
+		int 22h
+		xchg edx,eax
+		mov al,1
+		jc cb_fopen_90
+		cmp cx,[f_buf_size]
+		ja cb_fopen_90
+		or cx,cx
+		jz cb_fopen_90
+		mov [f_block_size],cx
+		or edx,edx
+		jz cb_fopen_90
+		mov [f_handle],si
+		mov [f_size],edx
+		mov ecx,edx
+		mov ax,[f_buf_size]
+		cwd
+		div word [f_block_size]
+		mov [f_blocks],ax
+
+		xor al,al
+cb_fopen_90:
+		ret
+
+
+; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+; Read next chunk.
+;
+; return:
+;   edx		buffer address (linear)
+;   ecx		data length (< 64k)
+;
+cb_fread:
+		xor ecx,ecx
+		mov si,[f_handle]
+		or si,si
+		jz cb_fread_80
+		mov cx,[f_blocks]
+		mov es,[f_buf_seg]
+		xor bx,bx
+		mov ax,7
+		int 22h
+		mov [f_handle],si
+		mov al,1
+		jc cb_fread_90
+cb_fread_80:
+		xor al,al
+cb_fread_90:
+		movzx edx,word [f_buf_seg]
+		shl edx,4
+		ret
+
+
+; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+; Return current working directory.
+;
+; return:
+;  edx		filename
+;
+cb_getcwd:
+		mov ax,15h
+		int 22h
+		mov edx,es
+		shl edx,4
+		movzx ebx,bx
+		add edx,ebx
+		xor al,al
+		ret
+
+
+; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+; Set current working directory.
+;
+cb_chdir:
+		mov bx,f_name
+		push ds
+		pop es
+		mov ax,25h
+		int 22h
+		xor al,al
+		ret
+
+
+; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+; read sector
+;
+;  edx		sector
+;
+; return:
+;  edx		buffer (linear address)
+;
+;  Note: does not return on error!
+;
+cb_readsector:
+		xor edi,edi
+		xor esi,esi
+		mov cx,1
+		mov es,[f_buf_seg]
+		xor bx,bx
+		mov ax,19h
+		int 22h
+		movzx edx,word [f_buf_seg]
+		shl edx,4
+		xor al,al
+		ret
+
+
+; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+; Re-read fs structures.
+;
+cb_mount:
+		mov ax,26h
+		int 22h
+		setc al
+		ret
+
+
+; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+;
+		align 2, db 0
+
+cb_table	dw cb_status
+		dw cb_fopen
+		dw cb_fread
+		dw cb_getcwd
+		dw cb_chdir
+		dw cb_readsector
+		dw cb_mount
+cb_len		equ ($-cb_table)/2
+
+f_handle	dw 0
+f_block_size	dw 0
+f_blocks	dw 0
+f_size		dd 0
+f_name		times 64 db 0
+f_name_len	equ $ - f_name
+