Initial library support for booting a Linux kernel

2 files changed, 295 insertions, 0 deletions

diff --git a/com32/lib/Makefile b/com32/lib/Makefile
index 2424fe53..0ea60e77 100644
--- a/com32/lib/Makefile
+++ b/com32/lib/Makefile
@@ -69,6 +69,8 @@ LIBOBJS = \
 	syslinux/shuffle_rm.o syslinux/zonelist.o			\
 	syslinux/dump_mmap.o syslinux/dump_movelist.o			\
 	\
+	syslinux/load_linux.o						\
+	\
 	syslinux/pxe_get_cached.o
 
 BINDIR   = /usr/bin
diff --git a/com32/lib/syslinux/load_linux.c b/com32/lib/syslinux/load_linux.c
new file mode 100644
index 00000000..620ad081
--- /dev/null
+++ b/com32/lib/syslinux/load_linux.c
@@ -0,0 +1,293 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 2007 H. Peter Anvin - All Rights Reserved
+ *
+ *   Permission is hereby granted, free of charge, to any person
+ *   obtaining a copy of this software and associated documentation
+ *   files (the "Software"), to deal in the Software without
+ *   restriction, including without limitation the rights to use,
+ *   copy, modify, merge, publish, distribute, sublicense, and/or
+ *   sell copies of the Software, and to permit persons to whom
+ *   the Software is furnished to do so, subject to the following
+ *   conditions:
+ *
+ *   The above copyright notice and this permission notice shall
+ *   be included in all copies or substantial portions of the Software.
+ *
+ *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ *   OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * load_linux.c
+ *
+ * Load a Linux kernel (Image/zImage/bzImage).
+ */
+
+#include <stdlib.h>
+#include <inttypes.h>
+#include <string.h>
+#include <syslinux/linux.h>
+#include <syslinux/bootrm.h>
+#include <syslinux/movebits.h>
+
+struct linux_header {
+  uint8_t  boot_sector_1[0x0020];
+  uint16_t old_cmd_line_magic;
+  uint16_t old_cmd_line_offset;
+  uint8_t  boot_sector_2[0x01f1-0x0024];
+  uint8_t  setup_sects;
+  uint16_t root_flags;
+  uint32_t syssize;
+  uint16_t ram_size;
+  uint16_t vid_mode;
+  uint16_t root_dev;
+  uint16_t boot_flag;
+  uint16_t jump;
+  uint32_t header;
+  uint16_t version;
+  uint32_t realmode_swtch;
+  uint16_t start_sys;
+  uint16_t kernel_version;
+  uint8_t  type_of_loader;
+  uint8_t  loadflags;
+  uint16_t setup_move_size;
+  uint32_t code32_start;
+  uint32_t ramdisk_image;
+  uint32_t ramdisk_size;
+  uint32_t bootsect_kludge;
+  uint16_t heap_end_ptr;
+  uint16_t pad1;
+  uint32_t cmd_line_ptr;
+  uint32_t initrd_addr_max;
+  uint32_t kernel_alignment;
+  uint8_t  relocatable_kernel;
+  uint8_t  pad2[3];
+  uint32_t cmdline_max_len;
+} __packed;
+
+#define BOOT_MAGIC 0xAA55
+#define LINUX_MAGIC ('H' + ('d' << 8) + ('r' << 16) + ('S' << 24))
+#define OLD_CMDLINE_MAGIC 0xA33F
+
+/* loadflags */
+#define LOAD_HIGH	0x01
+#define CAN_USE_HEAP	0x80
+
+/* Offset for the command line versus the real mode code */
+#define CMDLINE_OFFSET	0x9000
+
+/* Get the combined size of the initramfs */
+static addr_t initramfs_size(struct initramfs *initramfs)
+{
+  struct initramfs *ip;
+  addr_t size = 0;
+
+  if (!initramfs)
+    return 0;
+
+  for (ip = initramfs->next; ip->len; ip = ip->next)
+    size += ip->len;
+
+  return size;
+}
+
+/* Create the appropriate mappings for the initramfs */
+static int map_initramfs(struct syslinux_movelist **fraglist,
+			 struct syslinux_memmap **mmap,
+			 struct initramfs *initramfs,
+			 addr_t addr)
+{
+  struct initramfs *ip;
+
+  for (ip = initramfs->next; ip->len; ip = ip->next) {
+    if (ip->data_len) {
+      if (syslinux_add_movelist(fraglist, addr, (addr_t)ip->data, ip->len))
+	return -1;
+    }
+    if (ip->len > ip->data_len) {
+      if (syslinux_add_memmap(mmap, addr+ip->data_len,
+			      ip->len-ip->data_len, SMT_ZERO))
+	return -1;
+    }
+    addr += ip->len;
+  }
+
+  return 0;
+}
+
+int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
+			struct initramfs *initramfs,
+			char *cmdline,
+			uint16_t video_mode,
+			uint32_t memlimit)
+{
+  struct linux_header hdr, *whdr;
+  size_t real_mode_size, prot_mode_size;
+  addr_t real_mode_base, prot_mode_base;
+  addr_t irf_size;
+  size_t cmdline_size;
+  struct syslinux_rm_regs regs;
+  struct syslinux_movelist *fraglist = NULL;
+  struct syslinux_memmap *mmap = NULL;
+  struct syslinux_memmap *amap = NULL;
+
+  cmdline_size = strlen(cmdline)+1;
+
+  if (kernel_size < 2*512)
+    goto bail;
+
+  /* Copy the header into private storage */
+  memcpy(&hdr, kernel_buf, sizeof hdr);
+  whdr = (struct linux_header *)kernel_buf; /* Writable header */
+
+  if (hdr.boot_flag != BOOT_MAGIC)
+    goto bail;
+
+  if (hdr.header != LINUX_MAGIC) {
+    hdr.version = 0x0100;	/* Very old kernel */
+    hdr.loadflags = 0;
+  }
+
+  whdr->vid_mode = video_mode;
+
+  if (!hdr.setup_sects)
+    hdr.setup_sects = 4;
+
+  if (hdr.version < 0x0203)
+    hdr.initrd_addr_max = 0x37ffffff;
+
+  if (!memlimit || memlimit-1 > hdr.initrd_addr_max)
+    memlimit = hdr.initrd_addr_max+1; /* Zero for no limit */
+
+  if (hdr.version < 0x0206)
+    hdr.cmdline_max_len = 256;
+
+  if (cmdline_size > hdr.cmdline_max_len) {
+    cmdline_size = hdr.cmdline_max_len;
+    cmdline[cmdline_size-1] = '\0';
+  }
+
+  real_mode_size = (hdr.setup_sects+1) << 9;
+  real_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x10000 : 0x90000;
+  prot_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x100000 : 0x10000;
+  prot_mode_size = kernel_size - real_mode_size;
+
+  if (!(hdr.loadflags & LOAD_HIGH) && prot_mode_size > 512*1024)
+    goto bail;			/* Kernel cannot be loaded low */
+
+  if (initramfs && hdr.version < 0x0200)
+    goto bail;			/* initrd/initramfs not supported */
+
+  if (hdr.version >= 0x0200) {
+    whdr->type_of_loader = 0x30; /* SYSLINUX unknown module */
+    if (hdr.version >= 0x0201) {
+      whdr->heap_end_ptr = CMDLINE_OFFSET - 0x0200;
+      whdr->loadflags |= CAN_USE_HEAP;
+    }
+    if (hdr.version >= 0x0202) {
+      whdr->cmd_line_ptr = real_mode_base + CMDLINE_OFFSET;
+    } else {
+      whdr->old_cmd_line_magic  = OLD_CMDLINE_MAGIC;
+      whdr->old_cmd_line_offset = CMDLINE_OFFSET;
+      /* Be paranoid and round up to a multiple of 16 */
+      whdr->setup_move_size = (CMDLINE_OFFSET+cmdline_size+15) & ~15;
+    }
+  }
+
+  /* Get the memory map */
+  mmap = syslinux_memory_map();		/* Memory map for shuffle_boot */
+  amap = syslinux_dup_memmap(mmap);	/* Keep track of available memory */
+  if (!mmap || !amap)
+    goto bail;
+
+  /* If the user has specified a memory limit, mark that as unavailable.
+     Question: should we mark this off-limit in the mmap as well (meaning
+     it's unavailable to the boot loader, which probably has already touched
+     some of it), or just in the amap? */
+  if (memlimit)
+    if (syslinux_add_memmap(&amap, memlimit, -memlimit, SMT_RESERVED))
+      goto bail;
+
+  /* Place the kernel in memory */
+
+  /* Real mode code */
+  if (syslinux_add_movelist(&fraglist, real_mode_base, (addr_t)kernel_buf,
+			    real_mode_size))
+    goto bail;
+  if (syslinux_add_memmap(&amap, real_mode_base, CMDLINE_OFFSET+cmdline_size,
+			  SMT_ALLOC))
+    goto bail;
+
+  /* Zero region between real mode code and cmdline */
+  if (syslinux_add_memmap(&mmap, real_mode_base+real_mode_size,
+			  CMDLINE_OFFSET-real_mode_size, SMT_ZERO))
+    goto bail;
+
+  /* Command line */
+  if (syslinux_add_movelist(&fraglist, real_mode_base+CMDLINE_OFFSET,
+			    (addr_t)cmdline, cmdline_size))
+    goto bail;
+
+  /* Protected-mode code */
+  if (syslinux_add_movelist(&fraglist, prot_mode_base,
+			    (addr_t)kernel_buf + real_mode_size,
+			    prot_mode_size))
+    goto bail;
+  if (syslinux_add_memmap(&amap, prot_mode_base, prot_mode_size, SMT_ALLOC))
+    goto bail;
+
+  /* Figure out the size of the initramfs, and where to put it.
+     We should put it at the highest possible address which is
+     <= hdr.initrd_addr_max, which fits the entire initramfs. */
+
+  irf_size = initramfs_size(initramfs);	/* Handles initramfs == NULL */
+
+  if (irf_size) {
+    addr_t best_addr = 0;
+    struct syslinux_memmap *ml;
+
+    if (irf_size) {
+      for (ml = amap; ml->type != SMT_END; ml = ml->next) {
+	addr_t adj_start = (ml->start+0xfff) & ~0xfff; /* Page-aligned */
+	if (ml->type == SMT_FREE &&
+	    ml->next->start - adj_start >= irf_size)
+	  best_addr = (ml->next->start - irf_size) & ~0xfff;
+      }
+
+      if (!best_addr)
+	goto bail;		/* Insufficient memory for initramfs */
+
+      whdr->ramdisk_image = best_addr;
+      whdr->ramdisk_size = irf_size;
+
+      if (syslinux_add_memmap(&amap, best_addr, irf_size, SMT_ALLOC))
+	goto bail;
+
+      if (map_initramfs(&fraglist, &mmap, initramfs, best_addr))
+	goto bail;
+    }
+  }
+
+  /* Set up the registers on entry */
+  memset(&regs, 0, sizeof regs);
+  regs.es = regs.ds = regs.ss = regs.fs = regs.gs = real_mode_base >> 4;
+  regs.cs = (real_mode_base >> 4)+0x20;
+  /* regs.ip = 0; */
+  regs.esp.w[0] = CMDLINE_OFFSET;
+
+  syslinux_shuffle_boot_rm(fraglist, mmap, 0, &regs);
+
+ bail:
+  syslinux_free_movelist(fraglist);
+  syslinux_free_memmap(mmap);
+  syslinux_free_memmap(amap);
+  return -1;
+}