Initial version under CVS control

7 files changed, 955 insertions, 0 deletions

diff --git a/alloc.c b/alloc.c
new file mode 100644
index 0000000..398ec2b
--- /dev/null
+++ b/alloc.c
@@ -0,0 +1,126 @@
+#ident "$Id$"
+/* ----------------------------------------------------------------------- *
+ *   
+ *   Copyright 2000 H. Peter Anvin - All Rights Reserved
+ *
+ *   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., 675 Mass Ave, Cambridge MA 02139,
+ *   USA; either version 2 of the License, or (at your option) any later
+ *   version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * alloc.c
+ *
+ * Provide persistent storage versions of malloc(), realloc() and free().
+ *
+ * This code uses a modified buddy system allocator.  It's probably broken
+ * if your byte size isn't at least a power of 2.
+ */
+
+#include <stdlib.h>
+#include <inttypes.h>
+#include <limits.h>
+
+#define OBJSTORE_INTERNALS 1
+#include "objstore.h"
+
+#define OBJSTORE_ARENA_MAGIC	0xd8319f45
+
+/* This is the minimal order worth allocating.  This must be able
+   to hold two pointers plus an integer.  2^4 = 16 bytes. */
+#define ORDER_MIN		4	/* This must be >= 1. */
+
+/* This is the size of the alloc bitmask.  It will usually be sparse. */
+/* This is two bits per unit of the lowest order */
+#define ALLOC_BITMAP_SIZE	((ARENA_LIMIT >> ORDER_MIN)*2/CHAR_BIT)
+
+/* This bit is set in the order marker to indicate an occupied cell. */
+#define OCCUPIED		((unsigned char)(1 << (CHAR_BIT-1)))
+
+/* How many address bits? */
+static const int orders = sizeof(void *) * CHAR_BIT;
+
+/*
+ * Initalize the object store arena allocator.  Note the argument
+ * that allows a fixed-offset structure at the beginning.  This is
+ * essential, since otherwise we wouldn't be able to begin to
+ * pick apart the object hierarchy.
+ */
+void *objstore_arena_init(size_t leadin_size)
+{
+  struct ObjStore *os = objstore_os_struct;
+  void **order_list, **order_ptr;
+  uintptr_t begin_data, end_data, order_size;
+  int i;
+  
+  leadin_size = (leadin_size + os->pagesize - 1) & ~(os->pagesize - 1);
+  order_list = (void **)((char *)os->arena + leadin_size);
+  begin_data = (uintptr_t)(order_list + orders + 1);
+  end_data   = (uintptr_t)os->arena + os->arena_len;
+  
+  if ( (uintptr_t)order_list[0] != (uintptr_t)OBJSTORE_ARENA_MAGIC ) {
+    /* The arena is uninitialized. */
+
+    /* Begin by initializing all the pointers to null */
+    for ( i = 0 ; i < orders ; i++ )
+      order_list[i] = NULL;
+
+    /* Align the beginning and end to the lowest-supported order.
+       Note that begin_data is adjusted +1 above, to handle the
+       order/alloc marker of the first unit. */
+    begin_data = (begin_data + ((uintptr_t)1 << ORDER_MIN) - 1) &
+      ~(((uintptr_t)1 << ORDER_MIN) - 1);
+    end_data = end_data & ~(((uintptr_t)1 << ORDER_MIN)-1);
+
+    for ( i = ORDER_MIN ; i < orders ; i++ ) {
+      order_size = (uintptr_t)1 << i;
+      order_ptr  = &order_list[i];
+      if ( (begin_data & order_size) &&
+	   (end_data-begin_data) >= order_size ) {
+	((unsigned char *)begin_data)[-1] = i; /* Free object of order i */
+	*order_ptr = (void *)begin_data;
+	order_ptr = (void **)begin_data;
+	*order_ptr = NULL;
+	begin_data += order_size;
+      }
+      if ( (end_data & order_size) &&
+	   (end_data-begin_data) >= order_size ) {
+	end_data -= order_size;
+	((unsigned char *)begin_data)[-1] = i; /* Free object of order i */
+	*order_ptr = (void *)end_data;
+	order_ptr  = (void **)end_data;
+	*order_ptr = NULL;
+      }
+    }
+   
+    /* Arena now initialized */
+    order_list[0] = (void *)(uintptr_t)OBJSTORE_ARENA_MAGIC;
+  }
+}
+
+void *objstore_malloc(size_t size)
+{
+  int order_needed, order, i;
+  
+  size += 1;			/* Add 1 for bookkeeping byte */
+
+  /* Find the order needed */
+  for ( order_needed = ORDER_MIN ;
+	(size_t)(1UL << order_needed) < size ;
+	order_needed++ );
+
+  /* Find the order available */
+  for ( order = order_needed ; order < orders ; order++ ) {
+    if ( order_list[order] )
+      break;
+  }
+
+  if ( order >= orders )
+    return NULL;		/* Nothing available */
+
+  /* Split orders down to the needed one */
+  for ( i = order ; i < order_needed ; i++ ) {
+    
diff --git a/arena.c b/arena.c
new file mode 100644
index 0000000..60f9602
--- /dev/null
+++ b/arena.c
@@ -0,0 +1,642 @@
+#ident "$Id$"
+/* ----------------------------------------------------------------------- *
+ *   
+ *   Copyright 2000 H. Peter Anvin - All Rights Reserved
+ *
+ *   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., 675 Mass Ave, Cambridge MA 02139,
+ *   USA; either version 2 of the License, or (at your option) any later
+ *   version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * objstore.c
+ *
+ * Persistent object store implemented using memory-mapping tricks
+ */
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include <signal.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <fcntl.h>
+#include <math.h>		/* HUGE_VAL */
+#define __USE_MISC	1	/* Needed to support mremap() */
+#define __USE_GNU	1	/* Needed to support mremap() */
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sched.h>
+
+#define OBJSTORE_INTERNALS 1
+#include "objstore.h"
+
+enum page_status {
+  page_unread = 0,
+  page_clean = 1,
+  page_dirty = 2,
+};
+
+/*
+ * This is the data structure for the object store.  Note that only
+ * one active object store is supported, due to the need to trap
+ * SIGSEGV.
+ */
+struct ObjStore *objstore_os_struct;
+
+/* Wrappers for read() and write() which retries if incomplete */
+static ssize_t objstore_read(int fd, void *buf, size_t count)
+{
+  char *bufp = buf;
+  ssize_t total = 0;
+  ssize_t rv;
+
+  while ( count ) {
+    rv = read(fd, bufp, count);
+    if ( rv == -1 ) {
+      if ( errno == EINTR || errno == EAGAIN )
+	continue;
+      else
+	return total ? total : -1;
+    } else if ( rv == 0 ) {
+      return total;
+    }
+    bufp  += rv;
+    count -= rv;
+    total += rv;
+  }
+
+  return total;
+}
+
+static ssize_t objstore_write(int fd, void *buf, size_t count)
+{
+  char *bufp = buf;
+  ssize_t total = 0;
+  ssize_t rv;
+
+  while ( count ) {
+    rv = write(fd, bufp, count);
+    if ( rv == -1 ) {
+      if ( errno == EINTR || errno == EAGAIN )
+	continue;
+      else
+	return total ? total : -1;
+    } else if ( rv == 0 ) {
+      return total;
+    }
+    bufp  += rv;
+    count -= rv;
+    total += rv;
+  }
+
+  return total;
+}
+
+/*
+ * SIGSEGV handler for persistent object store
+ */
+static void objstore_sigsegv(int signal, siginfo_t *siginfo, void *ptr)
+{
+  struct ObjStore *os = objstore_os_struct;
+  void *page;
+  off_t offset;
+  char *pageinfo;
+  struct flock lock;
+  int old_errno = errno;
+#ifdef __linux__
+  struct sigcontext *ctxt;
+
+# ifdef __i386__		/* This is so specific to Linux/i386 */
+  if ( siginfo->si_code == 0 ) {
+    /* Old kernel.  Fill in data to the best of our knowledge. */
+    /* Don't even begin to ask me where the 0x14 comes from */
+    ctxt = (struct sigcontext *)((char *)ptr + 0x14);
+    if ( ctxt->trapno == 14 ) {
+      /* Linux/i386 uses unmapped pages to mimic PROT_NONE, so we can't
+	 tell ACCERR and MAPERR apart from the register state */
+      siginfo->si_code = SEGV_ACCERR;
+      siginfo->si_addr = (void *)ctxt->cr2;
+    }
+  }
+# endif /* __i386__ */
+#endif /* __linux__ */
+
+  if ( signal != SIGSEGV || siginfo->si_code != SEGV_ACCERR ||
+       ((uintptr_t)siginfo->si_addr - (uintptr_t)os->arena) >= os->arena_len ) {
+    struct sigaction dfl;
+
+    dfl.sa_handler = SIG_DFL;
+    sigemptyset(&dfl.sa_mask);
+    dfl.sa_flags = SA_ONESHOT;
+    sigaction(SIGSEGV, &dfl, NULL);
+
+    errno = old_errno;
+    return;			/* Re-take fault */
+  }
+
+  page = (void *)((uintptr_t)siginfo->si_addr & ~(os->pagesize-1));
+  offset = (uintptr_t)page - (uintptr_t)os->arena;
+  pageinfo = os->pageinfo + (offset >> os->pageshift);
+
+  mprotect(page, os->pagesize, PROT_READ|PROT_WRITE);
+
+  switch ( (enum page_status) *pageinfo ) {
+  case page_unread:
+    lseek(os->main_fd, offset, SEEK_SET);
+
+    lock.l_type   = F_RDLCK;
+    lock.l_whence = SEEK_SET;
+    lock.l_start  = offset;
+    lock.l_len    = os->pagesize;
+    while ( fcntl(os->main_fd, F_SETLKW, &lock) == -1 && errno == EINTR ); 
+    if ( objstore_read(os->main_fd, page, os->pagesize) < os->pagesize )
+      abort();		/* Uh-oh... */
+    
+    lock.l_type = F_UNLCK;
+    while ( fcntl(os->main_fd, F_SETLKW, &lock) == -1 && errno == EINTR );
+ 
+    mprotect(page, os->pagesize, PROT_READ); /* Make page readonly */
+    *pageinfo = page_clean;	/* Page read and clean */
+    os->loaded_count++;		/* For accounting purposes */
+    break;
+
+  case page_clean:
+    *pageinfo = page_dirty;	/* Page now dirty */
+    os->dirty_count++;		/* For accounting purposes */
+    /* Leave page r/w */
+    break;
+
+  default:
+    abort();			/* This shouldn't happen */
+  }
+
+  errno = old_errno;
+}
+
+/*
+ * Routine to do log writeback.  Used by initial log recovery routine
+ * as well as during-execution garbage collect.
+ * THIS ROUTINE SHOULD BE INVOKED WITH LOCK HELD ON THE LOG FILE.
+ */
+static int objstore_log_writeback(void)
+{
+  struct ObjStore *os = objstore_os_struct;
+  struct ObjStore_LogRecord record;
+  off_t position, last_commit;
+  struct flock lockmain;
+  
+  last_commit = 0;		/* Last COMMIT record found */
+  position = lseek(os->log_fd, 0, SEEK_SET);
+  
+  while ( objstore_read(os->log_fd, &record, sizeof(record)) == sizeof(record) ) {
+    if ( record.magic != LOGRECORD_MAGIC )
+      break;			/* Bad magic, assume rest of log corrupt */
+    if ( record.record_type == osrec_commit ) {
+      /* NOTE: last_commit points to the final byte to examine, thus
+	 at the *end* of the final commit record. */
+      position += sizeof(record);
+      last_commit = position;	/* Found a commit record */
+    } else if ( record.record_type == osrec_page ) {
+      /* Advance past current page cluster */
+      position = lseek(os->log_fd, record.size, SEEK_CUR);
+    } else {
+      return -1;		/* Unknown record - unsafe to process */
+    }
+  }
+  
+  /* Now we know where the last commit was.  Now we can process
+     everything up to that point. */
+  
+  position = lseek(os->log_fd, 0, SEEK_SET);
+  
+  while ( objstore_read(os->log_fd, &record, sizeof(record))
+	  == sizeof(record) && position < last_commit ) {
+    if ( record.magic != LOGRECORD_MAGIC )
+      break;			/* Bad magic, assume rest of log corrupt */
+    if ( record.record_type == osrec_commit ) {
+      /* Found a commit record, do nothing */
+      position += sizeof(record);
+    } else if ( record.record_type == osrec_page ) {
+      /* Write back data to file */
+      char *data;
+      
+      position += sizeof(record);
+      if ( !data )
+	return -1;		/* Badness... */
+      
+      lockmain.l_type   = F_WRLCK;
+      lockmain.l_whence = SEEK_SET;
+      lockmain.l_start  = record.offset;
+      lockmain.l_len    = record.size;
+      while ( fcntl(os->main_fd, F_SETLKW, &lockmain) == -1 && errno == EINTR ); 
+      data = mmap(NULL, record.size, PROT_WRITE, MAP_SHARED,
+		  os->main_fd, record.offset);
+      if ( data == MAP_FAILED )
+	return -1;
+      if ( objstore_read(os->log_fd, data, record.size) != record.size )
+	return -1;		/* Badness */
+      if ( munmap(data, record.size) )
+	return -1;
+      
+      lockmain.l_type = F_UNLCK;
+      while ( fcntl(os->main_fd, F_SETLKW, &lockmain) == -1 && errno == EINTR );
+      position += record.size;
+    } else {
+      return -1;		/* Unknown record - unsafe to process */
+    }
+  }
+  
+  /* Log successfully recovered.  Truncate. */
+  fsync(os->main_fd);
+  ftruncate(os->log_fd, 0);
+  /* Write initial commit record, for sequence number recovery */
+  record.magic       = LOGRECORD_MAGIC;
+  record.record_type = osrec_commit;
+  record.size        = os->fork_seq;
+  record.offset      = 0x54494d43; /* For debugging */
+  if ( objstore_write(os->log_fd, &record, sizeof(record)) < sizeof(record) )
+    return -1;
+
+  fsync(os->log_fd);		/* Indicate log recovery complete */
+
+  return 0;
+}
+
+/*
+ * Routine to do log recovery
+ */
+static int objstore_recover_log(void)
+{
+  struct ObjStore *os = objstore_os_struct;
+  struct flock lock;
+  int rv = 0;
+
+  /* First, lock the log file */
+  lock.l_type   = F_WRLCK;
+  lock.l_whence = SEEK_SET;
+  lock.l_start  = 0;
+  lock.l_len    = 0;
+  while ( fcntl(os->log_fd, F_SETLKW, &lock) == -1 && errno == EINTR );
+
+  /* Do log recovery, and write initial commit record. */
+  rv = objstore_log_writeback();
+
+  /* Increase the sequence number, since we just wrote a commit. */
+  os->fork_seq++;
+
+  /* Unlock file and run. */
+  lock.l_type = F_UNLCK;
+  while ( fcntl(os->log_fd, F_SETLKW, &lock) == -1 && errno == EINTR );
+
+  return rv;
+}
+
+/*
+ * Opens the object store.  This includes log
+ * playback (crash recovery) if the log file exists
+ * and is nonempty.
+ */
+void *objstore_init(char *main_file, char *log_file, size_t *arena_len)
+{
+  struct ObjStore *os;
+  void *arena_ptr;
+  struct sigaction sigact;
+  struct flock lock;
+  off_t file_len, len = arena_len ? *arena_len : 0;
+  size_t file_pages, len_pages;
+
+  arena_ptr = ARENA_ADDRESS;
+
+  objstore_os_struct = os = malloc(sizeof(struct ObjStore));
+  if ( !os )
+    goto errx0;
+
+  os->fork_seq = 0;		/* Initialize sequence counter */
+
+  os->main_fd = open(main_file, O_RDWR|O_CREAT, 0666);
+  if ( os->main_fd < 0 )
+    goto errx1;
+
+  os->pagesize = getpagesize();
+  if ( os->pagesize & (os->pagesize - 1) )
+    goto errx2;			/* WTF -- pagesize not a power of 2? */
+
+  /* Compute log2(os->pagesize) */
+  os->pageshift = 0;
+  while ( (1 << os->pageshift) < os->pagesize )
+    os->pageshift++;
+
+  /*
+   * Open log file
+   */
+  os->log_fd = open(log_file, O_RDWR|O_APPEND|O_CREAT, 0666);
+  if ( os->log_fd < 0 )
+    goto errx3;
+
+  /* Now, do log recovery if needed */
+  if ( objstore_recover_log() )
+    goto errx3;
+
+  /* Allocate arena memory space */
+  lock.l_type = F_WRLCK;
+  lock.l_whence = SEEK_SET;
+  lock.l_start  = 0;
+  lock.l_len    = 0;
+  while ( fcntl(os->main_fd, F_SETLKW, &lock) == -1 && errno == EINTR );
+  file_len = lseek(os->main_fd, 0, SEEK_END);
+  if ( len == 0 ) {
+    len = file_len;
+  }
+  len = (len + os->pagesize - 1) & ~(os->pagesize - 1);
+  if ( len > file_len ) {
+    ftruncate(os->main_fd, len);	/* Extend file */
+  }
+  lock.l_type = F_UNLCK;
+  while ( fcntl(os->main_fd, F_SETLKW, &lock) == -1 && errno == EINTR );
+
+  os->arena = mmap(arena_ptr, len, PROT_NONE,
+		   MAP_ANON|MAP_PRIVATE|MAP_FIXED, 0, 0);
+  if ( os->arena == MAP_FAILED )
+    goto errx3;
+
+  os->arena_len = len;
+  if ( *arena_len )
+    *arena_len = len;
+
+  os->pageinfo = malloc(len >> os->pageshift);
+  if ( !os->pageinfo )
+    goto errx4;
+
+  /* The pageinfo up to and including file_len is "unread"; beyond
+     file_len we know it must be zero and thus it can be marked "clean" */
+  file_len = (file_len + os->pagesize - 1) & ~(os->pagesize-1);
+  file_pages = file_len >> os->pageshift;
+  len_pages  = len >> os->pageshift;
+
+  memset(os->pageinfo, page_unread, file_pages);
+
+  if ( len_pages > file_pages ) {
+    mprotect((char *)os->arena + file_len, len - file_len, PROT_READ);
+    memset(os->pageinfo + file_pages, page_clean, len_pages-file_pages);
+  }
+
+  sigact.sa_sigaction = objstore_sigsegv;
+  sigemptyset(&sigact.sa_mask);
+  sigact.sa_flags = SA_RESTART|SA_SIGINFO;
+  if ( sigaction(SIGSEGV, &sigact, &os->oldact) )
+    goto errx5;
+
+  return os->arena;
+
+ errx5:
+  munmap(os->pageinfo, len >> os->pageshift);
+ errx4:
+  munmap(arena_ptr, len);
+ errx3:
+  if ( os->log_fd >= 0 ) close(os->log_fd);
+ errx2:
+  close(os->main_fd);
+ errx1:
+  free(os);
+ errx0:
+
+  return NULL;
+}
+
+/*
+ * Object store checkpoint.  Writes entries to the log file.
+ * The "gc_factor" is the factor of maximum log size file relative
+ * to the arena size.  For example, if gc_factor == 0.5 then if the
+ * log size is more than 50% of the arena file size a writeback cycle
+ * will take place after the log has been written.  This means other
+ * checkpoints will have to wait!
+ *
+ * Set gc_factor to 0.0 to force a gc, and to HUGE_VAL to inhibit gc.
+ */
+int objstore_checkpoint(double gc_factor)
+{
+  struct ObjStore *os = objstore_os_struct;
+  int f;
+  char *pi, *epi;
+  void *page;
+  
+  pi  = os->pageinfo;
+  epi = os->pageinfo + (os->arena_len >> os->pageshift);
+
+  f = fork();
+  if ( f < 0 )
+    return 1;			/* Checkpoint failed! */
+  else if ( f > 0 ) {
+    /* Parent process -- just mark all dirty pages clean */
+    
+    size_t size, count;
+    char *opi;
+    int found_dirty;
+    
+    /* Aggregate both clean and dirty pages; this should allow the OS
+       to avoid keeping track of quite as many memory protect regions */
+    for ( pi = os->pageinfo ; pi < epi ; pi++ ) {
+      if ( *pi == page_dirty || *pi == page_clean ) {
+	found_dirty = (*pi == page_dirty);
+	page = (char *)os->arena +
+	  ((uintptr_t)(pi - os->pageinfo) << os->pageshift);
+
+	opi = pi;
+	size = os->pagesize;
+	count = 1;
+	while ( pi+1 < epi &&
+		(pi[1] == page_dirty || pi[1] == page_clean) ) {
+	  pi++;
+	  found_dirty = found_dirty || (*pi == page_dirty);
+	  count++;
+	  size += os->pagesize;
+	}
+	if ( found_dirty ) {
+	  mprotect(page, size, PROT_READ);
+	  memset(opi, page_clean, count);
+	}
+      }
+    }
+    os->dirty_count = 0;	/* No pages dirty */
+    os->fork_seq++;		/* Increase next sequence number */
+    return 0;
+  } else {
+    /* Child process -- do the actual work of writing back dirty pages */
+
+    struct ObjStore_LogRecord record, last_rec;
+    struct flock lock;
+    off_t logsize;
+
+    record.magic = LOGRECORD_MAGIC;
+    record.record_type = osrec_page;
+
+    lock.l_whence = SEEK_SET;
+    lock.l_start  = 0;
+    lock.l_len    = 0;
+    for (;;) {
+      /* First, lock the entire log file */
+      lock.l_type   = F_WRLCK;
+      while ( fcntl(os->log_fd, F_SETLKW, &lock) == -1 && errno == EINTR );
+
+      /* Make sure we were indeed next in turn */
+      lseek(os->log_fd, -(off_t)sizeof(last_rec), SEEK_END);
+      if ( objstore_read(os->log_fd, &last_rec, sizeof(last_rec)) < sizeof(last_rec)) {
+	  kill(getppid(), SIGABRT); /* Kill main process */
+	  _exit(99);
+      }
+      if ( last_rec.size+1 == os->fork_seq )
+	break;			/* It's for us... */
+
+      /* Someone else is ahead of us in line.  Yield to them. */
+      lock.l_type = F_UNLCK;
+      while ( fcntl(os->log_fd, F_SETLKW, &lock) == -1 && errno == EINTR );
+      
+      sched_yield();		/* Snore... */
+    }
+
+    /* Write dirty pages to log file */
+    for ( pi = os->pageinfo ; pi < epi ; pi++ ) {
+      if ( *pi == page_dirty ) {
+	page = (char *)os->arena +
+	  ((uintptr_t)(pi - os->pageinfo) << os->pageshift);
+	record.offset = (char *)page - (char *)os->arena;
+
+	/* Aggregate contiguous pages into a single record */
+	record.size   = os->pagesize;
+	while ( pi+1 < epi && pi[1] == page_dirty ) {
+	  pi++;
+	  record.size += os->pagesize;
+	}
+
+	if ( objstore_write(os->log_fd, &record, sizeof(record))
+	     < sizeof(record) ||
+	     objstore_write(os->log_fd, page, record.size) < record.size ) {
+	  kill(getppid(), SIGABRT); /* Kill main process */
+	  _exit(99);
+	}
+      }
+    }
+
+    /* This might be more efficiently done with fdatasync() */
+    fsync(os->log_fd);		/* Make sure we have written everything */
+    
+    /* Write commit record */
+    record.record_type = osrec_commit;
+    record.size        = os->fork_seq;
+    record.offset      = (off_t)0x54494d43;
+    if ( objstore_write(os->log_fd, &record, sizeof(record)) < sizeof(record) ) {
+      kill(getppid(), SIGABRT);
+      _exit(99);
+    }
+    fsync(os->log_fd);
+
+    /* Check to see if it's time for garbage collect */
+    logsize = lseek(os->log_fd, 0, SEEK_END);
+    if ( gc_factor < HUGE_VAL && (double)logsize >= gc_factor*os->arena_len ) {
+      /* Replaying the log isn't the most efficient way to do this.
+	 We could also keep a status bit per page around, and flush
+	 them out of the shadow array.  The biggest problem with that
+	 is that it probably can't be done in the background, unlike
+	 this method.  Leave this as-is for now. */
+      if ( objstore_log_writeback() ) {
+	kill(getppid(), SIGABRT);
+	_exit(99);
+      }
+    }
+
+    /* Drop lock on log file */
+    lock.l_type = F_UNLCK;
+    while ( fcntl(os->log_fd, F_SETLKW, &lock) == -1 && errno == EINTR );
+
+    _exit(0);			/* Done! */
+  }
+}
+
+/*
+ * Extend the size of the object store.
+ *
+ * This currently relies on several Linux-specific features,
+ * specifically mremap() and knowing that we probably can extend
+ * it without changing the virtual address.
+ */
+int objstore_extend(size_t new_size)
+{
+  struct ObjStore *os = objstore_os_struct;
+  struct flock lock;
+  void *newp, *infop;
+  off_t file_size;
+  int ft;
+  size_t add_size, old_size;
+  size_t add_pages, old_pages, new_pages, file_pages;
+
+  old_size = os->arena_len;
+
+  if ( new_size <= old_size )
+    return 0;			/* No action */
+
+  new_size = (new_size + os->pagesize - 1) & ~(os->pagesize - 1);
+  add_size = new_size - old_size;
+
+  lock.l_type = F_WRLCK;
+  lock.l_whence = SEEK_SET;
+  lock.l_start  = 0;
+  lock.l_len    = 0;
+  while ( fcntl(os->main_fd, F_SETLKW, &lock) == -1 && errno == EINTR );
+
+  lock.l_type = F_UNLCK;
+  file_size = lseek(os->main_fd, 0, SEEK_END);
+  if ( file_size < new_size )
+    ft = ftruncate(os->main_fd, new_size);
+  else
+    ft = 0;
+
+  while ( fcntl(os->main_fd, F_SETLKW, &lock) == -1 && errno == EINTR );
+  if ( ft )
+    return -1;			/* Failure */
+
+  newp = mmap((char*)os->arena + old_size,
+	      add_size,
+	      PROT_NONE,
+	      MAP_PRIVATE|MAP_ANON|MAP_FIXED, 0, 0);
+  
+  if ( newp == MAP_FAILED )
+    return -1;			/* Failure */
+
+  /* Since we specified MAP_FIXED, this should be guaranteed */
+  assert( newp == (char*)os->arena + old_size );
+
+  /* Convert sizes to pages */
+  file_size  = (file_size + os->pagesize - 1) & ~(os->pagesize-1);
+  new_pages  = new_size  >> os->pageshift;
+  old_pages  = old_size  >> os->pageshift;
+  file_pages = file_size >> os->pageshift;
+  add_pages  = new_pages - old_pages;
+
+  infop = realloc(os->pageinfo, new_pages);
+  if ( !infop ) {
+    munmap(newp, add_size);
+    return -1;			/* Failure */
+  }
+  
+  os->arena_len  = new_size;
+  os->pageinfo   = infop;
+  
+  /* If we extended the file, the new area is known to contain
+     zero, and can thus be considered "clean"; otherwise we have
+     to consider it "unread". */
+  if ( file_pages > old_pages ) {
+    memset(os->pageinfo + old_pages, page_unread, file_pages-old_pages);
+  }
+  if ( file_pages < new_pages ) {
+    memset(os->pageinfo + file_pages, page_clean, new_pages-file_pages);
+    mprotect((char *)os->arena + file_size, new_size-file_size, PROT_READ);
+  }
+
+  return 0;
+}
diff --git a/ftrunctest.c b/ftrunctest.c
new file mode 100644
index 0000000..dfa58b3
--- /dev/null
+++ b/ftrunctest.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <string.h>
+
+int main(int argc, char *argv[])
+{
+  int fd;
+  char *mapping;
+
+  fd = open("ftrunc.dat", O_RDWR|O_CREAT, 0666);
+  ftruncate(fd, 1024*1024*1024);
+  close(fd);
+
+  return 0;
+}
+
+ 
diff --git a/lpsm.h b/lpsm.h
new file mode 100644
index 0000000..6d80df6
--- /dev/null
+++ b/lpsm.h
@@ -0,0 +1,71 @@
+#ident "$Id$"
+/* ----------------------------------------------------------------------- *
+ *   
+ *   Copyright 2000 H. Peter Anvin - All Rights Reserved
+ *
+ *   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., 675 Mass Ave, Cambridge MA 02139,
+ *   USA; either version 2 of the License, or (at your option) any later
+ *   version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * objstore.h
+ *
+ * Header file for the persistent object store
+ */
+
+#ifndef OBJSTORE_H
+#define OBJSTORE_H
+
+#include <stdlib.h>
+#include <signal.h>
+#include <inttypes.h>
+
+#ifdef OBJSTORE_INTERNALS
+
+#include "system.h"		/* System-specific constants */
+
+struct ObjStore {
+  int main_fd;			/* Primary file descriptor */
+  int log_fd;			/* Log file descriptor */
+  int pagesize;			/* Page size */
+  int pageshift;		/* log2(pagesize) */
+  void *arena;			/* Mapped memory zone */
+  size_t arena_len;		/* Length of arena */
+  char *pageinfo;		/* Page info pointer */
+  size_t loaded_count;		/* Loaded pages count (accounting) */
+  size_t dirty_count;		/* Dirty pages count (accounting) */
+  struct sigaction oldact;	/* Previous signal action */
+  size_t fork_seq;		/* Sequence number of forked processes */
+};
+
+enum ObjStore_RecordType {
+  osrec_page,			/* Page data */
+  osrec_commit,			/* Commit record */
+};
+
+#define LOGRECORD_MAGIC 0x9247746e
+
+struct ObjStore_LogRecord {
+  unsigned int  magic;		/* Magic number; for verification */
+  unsigned int record_type;	/* Record */
+  size_t size;			/* Data byte count (sequence # for commit) */
+  off_t offset;			/* Offset of data */
+};
+
+extern struct ObjStore *objstore_os_struct;
+
+#else  /* not OBJSTORE_INTERNALS */
+
+struct Objstore;
+
+#endif /* not OBJSTORE_INTERNALS */
+
+void *objstore_init(char *main_file, char *log_file, size_t *arena_len);
+int objstore_checkpoint(double gc_factor);
+int objstore_extend(size_t new_size);
+
+#endif
diff --git a/system.h b/system.h
new file mode 100644
index 0000000..9d74409
--- /dev/null
+++ b/system.h
@@ -0,0 +1,29 @@
+#ident "$Id$"
+/* ----------------------------------------------------------------------- *
+ *   
+ *   Copyright 2000 H. Peter Anvin - All Rights Reserved
+ *
+ *   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., 675 Mass Ave, Cambridge MA 02139,
+ *   USA; either version 2 of the License, or (at your option) any later
+ *   version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * system.h
+ *
+ * System-specific constants.
+ */
+
+#ifndef SYSTEM_H
+#define SYSTEM_H
+
+/* These constants are appropriate for Linux/i386 */
+
+/* This is where we map the database file - must be constant */
+#define ARENA_ADDRESS	((void *)0x60000000)
+
+#endif /* SYSTEM_H */
+
diff --git a/test_mmap.c b/test_mmap.c
new file mode 100644
index 0000000..445870f
--- /dev/null
+++ b/test_mmap.c
@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <string.h>
+#include <errno.h>
+
+int main(int argc, char *argv[])
+{
+  char *mapping;
+
+  mapping = mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, 0, 0);
+  mmap(mapping+8192, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON|MAP_FIXED, 0, 0);
+  strcpy(mapping+0, "Foo mani padme hum");
+  strcpy(mapping+4096, "Foo mani padme hum");
+  errno = 0;
+  mmap(mapping+4096, 4096, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_PRIVATE|MAP_ANON, 0, 0);
+  munmap(mapping, 16384);
+}
+
+ 
diff --git a/teststore.c b/teststore.c
new file mode 100644
index 0000000..14c40fc
--- /dev/null
+++ b/teststore.c
@@ -0,0 +1,47 @@
+#ident "$Id$"
+/* ----------------------------------------------------------------------- *
+ *   
+ *   Copyright 2000 Transmeta Corporation - All Rights Reserved
+ *
+ *   This source module contains confidential and proprietary information
+ *   of Transmeta Corporation.  It is not to be disclosed or used except
+ *   in accordance with applicable agreements.  This copyright notice does
+ *   not evidence any actual or intended publication of such source code.
+ *
+ * ----------------------------------------------------------------------- */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include "objstore.h"
+
+int main(int argc, char *argv[])
+{
+  void *buf;
+  int arena_len = 16384;
+
+  buf = objstore_init("test.dat", "test.log", &arena_len);
+
+  printf("Read from first page: %s\n", (char *)buf);
+
+  strcpy((char *)buf + 4096, "This is the second page!");
+  strcpy((char *)buf + 8192, "This is the third page!");
+
+  printf("Read from third page: %s\n", (char *)buf + 8192);
+  objstore_checkpoint(0.5);
+
+  strcpy((char *)buf + 8192, "This is also the third page!");
+
+  printf("Read from third page: %s\n", (char *)buf + 8192);
+  objstore_checkpoint(0.0);
+
+  objstore_extend(65536);
+  strcpy((char *)buf + 32768, "This is the ninth page!");
+  objstore_checkpoint(0.0);
+
+  sleep(5);
+
+  return 0;
+}
+