source: patches/grub-0.97-use_mmap-2.patch@ 757a9c2

Submitted By: Jim Gifford <clfs at cross-lfs dot org>
Date: 07-15-2009
Initial Package Version: 0.97
Upstream Status: Unknown
Origin: Grub Bug Report - http://savannah.gnu.org/bugs/?func=detailitem&item_id=11312
Description: This patch fixes the following issues on x86_64
        1) malloc'd pages seem to lack the execute bit on x86_64;
        2) grub seems to use some stack pointer diversion to malloc'd pages;
        3) nested functions execute data on the stack;
        4) this causes a segfault (at least on my machine)

diff -Naur grub-0.97.orig/grub/asmstub.c grub-0.97/grub/asmstub.c
--- grub-0.97.orig/grub/asmstub.c       2005-02-16 12:45:14.000000000 -0800
+++ grub-0.97/grub/asmstub.c    2009-07-05 23:32:43.000000000 -0700
@@ -42,6 +42,7 @@
 #include <sys/time.h>
 #include <termios.h>
 #include <signal.h>
+#include <sys/mman.h>
 
 #ifdef __linux__
 # include <sys/ioctl.h>                /* ioctl */
@@ -79,7 +80,7 @@
 struct apm_info apm_bios_info;
 
 /* Emulation requirements. */
-char *grub_scratch_mem = 0;
+void *grub_scratch_mem = 0;
 
 struct geometry *disks = 0;
 
@@ -103,14 +104,62 @@
 static unsigned int serial_speed;
 #endif /* SIMULATE_SLOWNESS_OF_SERIAL */
 
+/* This allocates page-aligned storage of the specified size, which must be
+ * a multiple of the page size as determined by calling sysconf(_SC_PAGESIZE)
+ */
+#ifdef __linux__
+static void *
+grub_mmap_alloc(size_t len)
+{
+  int mmap_flags = MAP_ANONYMOUS|MAP_PRIVATE;
+
+#ifdef MAP_32BIT
+  mmap_flags |= MAP_32BIT;
+#endif
+  /* Mark the simulated stack executable, as GCC uses stack trampolines
+   * to implement nested functions. */
+  return mmap(NULL, len, PROT_READ|PROT_WRITE|PROT_EXEC, mmap_flags, -1, 0);
+}
+#else /* !defined(__linux__) */
+static void *
+grub_mmap_alloc(size_t len)
+{
+  int fd = 0, offset = 0, ret = 0;
+  void *pa = MAP_FAILED; 
+  char template[] = "/tmp/grub_mmap_alloc_XXXXXX";
+  int e;
+
+  fd = mkstemp(template);
+  if (fd < 0)
+    return pa;
+
+  unlink(template);
+
+  ret = ftruncate(fd, len);
+  if (ret < 0)
+    return pa;
+
+  /* Mark the simulated stack executable, as GCC uses stack trampolines
+   * to implement nested functions. */
+  pa = mmap(NULL, len, PROT_READ|PROT_WRITE|PROT_EXEC,
+                  MAP_PRIVATE, fd, offset);
+
+  e = errno;
+  close(fd);
+  errno = e;
+  return pa;
+}
+#endif /* defined(__linux__) */
+
 /* The main entry point into this mess. */
 int
 grub_stage2 (void)
 {
   /* These need to be static, because they survive our stack transitions. */
   static int status = 0;
-  static char *realstack;
-  char *scratch, *simstack;
+  static void *realstack;
+  void *simstack_alloc_base, *simstack;
+  size_t simstack_size, page_size;
   int i;
 
   auto void doit (void);
@@ -142,9 +191,35 @@
     }
 
   assert (grub_scratch_mem == 0);
-  scratch = malloc (0x100000 + EXTENDED_MEMSIZE + 15);
-  assert (scratch);
-  grub_scratch_mem = (char *) ((((int) scratch) >> 4) << 4);
+
+  /* Allocate enough pages for 0x100000 + EXTENDED_SIZE + 15, and
+   * make sure the memory is aligned to a multiple of the system's
+   * page size */
+  page_size = sysconf (_SC_PAGESIZE);
+  simstack_size = ( 0x100000 + EXTENDED_MEMSIZE + 15);
+  if (simstack_size % page_size)
+    {
+      /* If we're not on a page_size boundary, round up to the next one */
+      simstack_size &= ~(page_size-1);
+      simstack_size += page_size;
+    }
+
+  /* Add one for a PROT_NONE boundary page at each end. */
+  simstack_size += 2 * page_size;
+
+  simstack_alloc_base = grub_mmap_alloc(simstack_size);
+  assert (simstack_alloc_base != MAP_FAILED);
+
+  /* mark pages above and below our simstack area as innaccessable.
+   * If the implementation we're using doesn't support that, then the
+   * new protection modes are undefined.  It's safe to just ignore
+   * them, though.  It'd be nice if we knew that we'd get a SEGV for
+   * touching the area, but that's all.  it'd be nice to have. */
+  mprotect (simstack_alloc_base, page_size, PROT_NONE);
+  mprotect ((void *)((unsigned long)simstack_alloc_base +
+                         simstack_size - page_size),  page_size, PROT_NONE);
+
+  grub_scratch_mem = (void *)((unsigned long)simstack_alloc_base + page_size);
 
   /* FIXME: simulate the memory holes using mprot, if available. */
 
@@ -217,7 +292,7 @@
   device_map = 0;
   free (disks);
   disks = 0;
-  free (scratch);
+  munmap(simstack_alloc_base, simstack_size);
   grub_scratch_mem = 0;
 
   if (serial_device)
diff -Naur grub-0.97.orig/stage2/builtins.c grub-0.97/stage2/builtins.c
--- grub-0.97.orig/stage2/builtins.c    2005-02-15 13:58:23.000000000 -0800
+++ grub-0.97/stage2/builtins.c 2009-07-05 23:42:45.000000000 -0700
@@ -130,63 +130,97 @@
   grub_printf ("[%d,%d,%d]", sector, offset, length);
 }
 
-

+/* blocklist_read_helper nee disk_read_blocklist_func was a nested
+ * function, to which pointers were taken and exposed globally.  Even
+ * in the GNU-C nested functions extension, they have local linkage,
+ * and aren't guaranteed to be accessable *at all* outside of their 
+ * containing scope.
+ *
+ * Above and beyond all of that, the variables within blocklist_func_context
+ * are originally local variables, with local (not even static) linkage,
+ * from within blocklist_func.  These were each referenced by
+ * disk_read_blocklist_func, which is only called from other functions
+ * through a globally scoped pointer.
+ * 
+ * The documentation in GCC actually uses the words "all hell will break
+ * loose" to describe this scenario.
+ *
+ * Also, "start_sector" was also used uninitialized, but gcc doesn't warn
+ * about it (possibly because of the scoping madness?)
+ */
+   
+static struct {
+       int start_sector;
+       int num_sectors;
+       int num_entries;
+       int last_length;
+} blocklist_func_context = {
+       .start_sector = 0,
+       .num_sectors = 0,
+       .num_entries = 0,
+       .last_length = 0
+};
+
+/* Collect contiguous blocks into one entry as many as possible,
+   and print the blocklist notation on the screen.  */
+static void
+blocklist_read_helper (int sector, int offset, int length)
+{
+  int *start_sector = &blocklist_func_context.start_sector;
+  int *num_sectors = &blocklist_func_context.num_sectors;
+  int *num_entries = &blocklist_func_context.num_entries;
+  int *last_length = &blocklist_func_context.last_length;
+
+  if (*num_sectors > 0)
+  {
+    if (*start_sector + *num_sectors == sector
+      && offset == 0 && *last_length == SECTOR_SIZE)
+    {
+      *num_sectors++;
+      *last_length = length;
+      return;
+    }
+    else
+    {
+      if (*last_length == SECTOR_SIZE)
+        grub_printf ("%s%d+%d", *num_entries ? "," : "",
+          *start_sector - part_start, *num_sectors);
+      else if (*num_sectors > 1)
+        grub_printf ("%s%d+%d,%d[0-%d]", *num_entries ? "," : "",
+          *start_sector - part_start, *num_sectors-1,
+          *start_sector + *num_sectors-1 - part_start, 
+          *last_length);
+      else
+        grub_printf ("%s%d[0-%d]", *num_entries ? "," : "",
+          *start_sector - part_start, *last_length);
+      *num_entries++;
+      *num_sectors = 0;
+    }
+  }
+
+  if (offset > 0)
+  {
+    grub_printf("%s%d[%d-%d]", *num_entries ? "," : "",
+          sector-part_start, offset, offset+length);
+    *num_entries++;
+  }
+  else
+  {
+    *start_sector = sector;
+    *num_sectors = 1;
+    *last_length = length;
+  }
+}
+
 /* blocklist */
 static int
 blocklist_func (char *arg, int flags)
 {
   char *dummy = (char *) RAW_ADDR (0x100000);
-  int start_sector;
-  int num_sectors = 0;
-  int num_entries = 0;
-  int last_length = 0;
 
-  auto void disk_read_blocklist_func (int sector, int offset, int length);
-  
-  /* Collect contiguous blocks into one entry as many as possible,
-     and print the blocklist notation on the screen.  */
-  auto void disk_read_blocklist_func (int sector, int offset, int length)
-    {
-      if (num_sectors > 0)
-       {
-         if (start_sector + num_sectors == sector
-             && offset == 0 && last_length == SECTOR_SIZE)
-           {
-             num_sectors++;
-             last_length = length;
-             return;
-           }
-         else
-           {
-             if (last_length == SECTOR_SIZE)
-               grub_printf ("%s%d+%d", num_entries ? "," : "",
-                            start_sector - part_start, num_sectors);
-             else if (num_sectors > 1)
-               grub_printf ("%s%d+%d,%d[0-%d]", num_entries ? "," : "",
-                            start_sector - part_start, num_sectors-1,
-                            start_sector + num_sectors-1 - part_start, 
-                            last_length);
-             else
-               grub_printf ("%s%d[0-%d]", num_entries ? "," : "",
-                            start_sector - part_start, last_length);
-             num_entries++;
-             num_sectors = 0;
-           }
-       }
-
-      if (offset > 0)
-       {
-         grub_printf("%s%d[%d-%d]", num_entries ? "," : "",
-                     sector-part_start, offset, offset+length);
-         num_entries++;
-       }
-      else
-       {
-         start_sector = sector;
-         num_sectors = 1;
-         last_length = length;
-       }
-    }
+  int *start_sector = &blocklist_func_context.start_sector;
+  int *num_sectors = &blocklist_func_context.num_sectors;
+  int *num_entries = &blocklist_func_context.num_entries;
 
   /* Open the file.  */
   if (! grub_open (arg))
@@ -206,15 +240,15 @@
   grub_printf (")");
 
   /* Read in the whole file to DUMMY.  */
-  disk_read_hook = disk_read_blocklist_func;
+  disk_read_hook = blocklist_read_helper;
   if (! grub_read (dummy, -1))
     goto fail;
 
   /* The last entry may not be printed yet.  Don't check if it is a
    * full sector, since it doesn't matter if we read too much. */
-  if (num_sectors > 0)
-    grub_printf ("%s%d+%d", num_entries ? "," : "",
-                start_sector - part_start, num_sectors);
+  if (*num_sectors > 0)
+       grub_printf ("%s%d+%d", *num_entries ? "," : "",
+                *start_sector - part_start, *num_sectors);
 
   grub_printf ("\n");
   
@@ -1740,6 +1774,77 @@
 
 

 /* install */
+static struct {
+       int saved_sector;
+       int installaddr;
+       int installlist;
+       char *stage2_first_buffer;
+} install_func_context = {
+       .saved_sector = 0,
+       .installaddr = 0,
+       .installlist = 0,
+       .stage2_first_buffer = NULL,
+};
+
+/* Save the first sector of Stage2 in STAGE2_SECT.  */
+/* Formerly disk_read_savesect_func with local scope inside install_func */
+static void
+install_savesect_helper(int sector, int offset, int length)
+{
+  if (debug)
+    printf ("[%d]", sector);
+
+  /* ReiserFS has files which sometimes contain data not aligned
+     on sector boundaries.  Returning an error is better than
+     silently failing. */
+  if (offset != 0 || length != SECTOR_SIZE)
+    errnum = ERR_UNALIGNED;
+
+  install_func_context.saved_sector = sector;
+}
+
+/* Write SECTOR to INSTALLLIST, and update INSTALLADDR and  INSTALLSECT.  */
+/* Formerly disk_read_blocklist_func with local scope inside install_func */
+static void
+install_blocklist_helper (int sector, int offset, int length)
+{
+  int *installaddr = &install_func_context.installaddr;
+  int *installlist = &install_func_context.installlist;
+  char **stage2_first_buffer = &install_func_context.stage2_first_buffer;
+  /* Was the last sector full? */
+  static int last_length = SECTOR_SIZE;
+
+  if (debug)
+    printf("[%d]", sector);
+
+  if (offset != 0 || last_length != SECTOR_SIZE)
+    {
+      /* We found a non-sector-aligned data block. */
+      errnum = ERR_UNALIGNED;
+      return;
+    }
+
+  last_length = length;
+
+  if (*((unsigned long *) (*installlist - 4))
+      + *((unsigned short *) *installlist) != sector
+      || *installlist == (int) *stage2_first_buffer + SECTOR_SIZE + 4)
+    {
+      *installlist -= 8;
+
+      if (*((unsigned long *) (*installlist - 8)))
+        errnum = ERR_WONT_FIT;
+      else
+        {
+          *((unsigned short *) (*installlist + 2)) = (*installaddr >> 4);
+          *((unsigned long *) (*installlist - 4)) = sector;
+        }
+    }
+
+  *((unsigned short *) *installlist) += 1;
+  *installaddr += 512;
+}
+
 static int
 install_func (char *arg, int flags)
 {
@@ -1747,8 +1852,12 @@
   char *stage1_buffer = (char *) RAW_ADDR (0x100000);
   char *stage2_buffer = stage1_buffer + SECTOR_SIZE;
   char *old_sect = stage2_buffer + SECTOR_SIZE;
-  char *stage2_first_buffer = old_sect + SECTOR_SIZE;
-  char *stage2_second_buffer = stage2_first_buffer + SECTOR_SIZE;
+  /* stage2_first_buffer used to be defined as:
+   * char *stage2_first_buffer = old_sect + SECTOR_SIZE;  */
+  char **stage2_first_buffer = &install_func_context.stage2_first_buffer;
+  /* and stage2_second_buffer was:
+   * char *stage2_second_buffer = stage2_first_buffer + SECTOR_SIZE; */
+  char *stage2_second_buffer = old_sect + SECTOR_SIZE + SECTOR_SIZE;
   /* XXX: Probably SECTOR_SIZE is reasonable.  */
   char *config_filename = stage2_second_buffer + SECTOR_SIZE;
   char *dummy = config_filename + SECTOR_SIZE;
@@ -1757,10 +1866,11 @@
   int src_drive, src_partition, src_part_start;
   int i;
   struct geometry dest_geom, src_geom;
-  int saved_sector;
+  int *saved_sector = &install_func_context.saved_sector;
   int stage2_first_sector, stage2_second_sector;
   char *ptr;
-  int installaddr, installlist;
+  int *installaddr = &install_func_context.installaddr;
+  int *installlist = &install_func_context.installlist;
   /* Point to the location of the name of a configuration file in Stage 2.  */
   char *config_file_location;
   /* If FILE is a Stage 1.5?  */
@@ -1769,67 +1879,13 @@
   int is_open = 0;
   /* If LBA is forced?  */
   int is_force_lba = 0;
-  /* Was the last sector full? */
-  int last_length = SECTOR_SIZE;
-  
+
+  *stage2_first_buffer = old_sect + SECTOR_SIZE;
 #ifdef GRUB_UTIL
   /* If the Stage 2 is in a partition mounted by an OS, this will store
      the filename under the OS.  */
   char *stage2_os_file = 0;
 #endif /* GRUB_UTIL */
-  
-  auto void disk_read_savesect_func (int sector, int offset, int length);
-  auto void disk_read_blocklist_func (int sector, int offset, int length);
-  
-  /* Save the first sector of Stage2 in STAGE2_SECT.  */
-  auto void disk_read_savesect_func (int sector, int offset, int length)
-    {
-      if (debug)
-       printf ("[%d]", sector);
-
-      /* ReiserFS has files which sometimes contain data not aligned
-         on sector boundaries.  Returning an error is better than
-         silently failing. */
-      if (offset != 0 || length != SECTOR_SIZE)
-       errnum = ERR_UNALIGNED;
-
-      saved_sector = sector;
-    }
-
-  /* Write SECTOR to INSTALLLIST, and update INSTALLADDR and
-     INSTALLSECT.  */
-  auto void disk_read_blocklist_func (int sector, int offset, int length)
-    {
-      if (debug)
-       printf("[%d]", sector);
-
-      if (offset != 0 || last_length != SECTOR_SIZE)
-       {
-         /* We found a non-sector-aligned data block. */
-         errnum = ERR_UNALIGNED;
-         return;
-       }
-
-      last_length = length;
-
-      if (*((unsigned long *) (installlist - 4))
-         + *((unsigned short *) installlist) != sector
-         || installlist == (int) stage2_first_buffer + SECTOR_SIZE + 4)
-       {
-         installlist -= 8;
-
-         if (*((unsigned long *) (installlist - 8)))
-           errnum = ERR_WONT_FIT;
-         else
-           {
-             *((unsigned short *) (installlist + 2)) = (installaddr >> 4);
-             *((unsigned long *) (installlist - 4)) = sector;
-           }
-       }
-
-      *((unsigned short *) installlist) += 1;
-      installaddr += 512;
-    }
 
   /* First, check the GNU-style long option.  */
   while (1)
@@ -1862,10 +1918,10 @@
   addr = skip_to (0, file);
 
   /* Get the installation address.  */
-  if (! safe_parse_maxint (&addr, &installaddr))
+  if (! safe_parse_maxint (&addr, installaddr))
     {
       /* ADDR is not specified.  */
-      installaddr = 0;
+      *installaddr = 0;
       ptr = addr;
       errnum = 0;
     }
@@ -1961,17 +2017,17 @@
       = 0x9090;
   
   /* Read the first sector of Stage 2.  */
-  disk_read_hook = disk_read_savesect_func;
-  if (grub_read (stage2_first_buffer, SECTOR_SIZE) != SECTOR_SIZE)
+  disk_read_hook = install_savesect_helper;
+  if (grub_read (*stage2_first_buffer, SECTOR_SIZE) != SECTOR_SIZE)
     goto fail;
 
-  stage2_first_sector = saved_sector;
+  stage2_first_sector = *saved_sector;
   
   /* Read the second sector of Stage 2.  */
   if (grub_read (stage2_second_buffer, SECTOR_SIZE) != SECTOR_SIZE)
     goto fail;
 
-  stage2_second_sector = saved_sector;
+  stage2_second_sector = *saved_sector;
   
   /* Check for the version of Stage 2.  */
   if (*((short *) (stage2_second_buffer + STAGE2_VER_MAJ_OFFS))
@@ -1987,27 +2043,27 @@
 
   /* If INSTALLADDR is not specified explicitly in the command-line,
      determine it by the Stage 2 id.  */
-  if (! installaddr)
+  if (! *installaddr)
     {
       if (! is_stage1_5)
        /* Stage 2.  */
-       installaddr = 0x8000;
+       *installaddr = 0x8000;
       else
        /* Stage 1.5.  */
-       installaddr = 0x2000;
+       *installaddr = 0x2000;
     }
 
   *((unsigned long *) (stage1_buffer + STAGE1_STAGE2_SECTOR))
     = stage2_first_sector;
   *((unsigned short *) (stage1_buffer + STAGE1_STAGE2_ADDRESS))
-    = installaddr;
+    = *installaddr;
   *((unsigned short *) (stage1_buffer + STAGE1_STAGE2_SEGMENT))
-    = installaddr >> 4;
+    = *installaddr >> 4;
 
-  i = (int) stage2_first_buffer + SECTOR_SIZE - 4;
+  i = (int) *stage2_first_buffer + SECTOR_SIZE - 4;
   while (*((unsigned long *) i))
     {
-      if (i < (int) stage2_first_buffer
+      if (i < (int) *stage2_first_buffer
          || (*((int *) (i - 4)) & 0x80000000)
          || *((unsigned short *) i) >= 0xA00
          || *((short *) (i + 2)) == 0)
@@ -2021,13 +2077,13 @@
       i -= 8;
     }
 
-  installlist = (int) stage2_first_buffer + SECTOR_SIZE + 4;
-  installaddr += SECTOR_SIZE;
+  *installlist = (int) *stage2_first_buffer + SECTOR_SIZE + 4;
+  *installaddr += SECTOR_SIZE;
   
   /* Read the whole of Stage2 except for the first sector.  */
   grub_seek (SECTOR_SIZE);
 
-  disk_read_hook = disk_read_blocklist_func;
+  disk_read_hook = install_blocklist_helper;
   if (! grub_read (dummy, -1))
     goto fail;
   
@@ -2110,7 +2166,7 @@
          /* Skip the first sector.  */
          grub_seek (SECTOR_SIZE);
          
-         disk_read_hook = disk_read_savesect_func;
+         disk_read_hook = install_savesect_helper;
          if (grub_read (stage2_buffer, SECTOR_SIZE) != SECTOR_SIZE)
            goto fail;
          
@@ -2180,7 +2236,7 @@
          else
 #endif /* GRUB_UTIL */
            {
-             if (! devwrite (saved_sector - part_start, 1, stage2_buffer))
+             if (! devwrite (*saved_sector - part_start, 1, stage2_buffer))
                goto fail;
            }
        }
@@ -2202,7 +2258,7 @@
          goto fail;
        }
 
-      if (fwrite (stage2_first_buffer, 1, SECTOR_SIZE, fp) != SECTOR_SIZE)
+      if (fwrite (*stage2_first_buffer, 1, SECTOR_SIZE, fp) != SECTOR_SIZE)
        {
          fclose (fp);
          errnum = ERR_WRITE;
@@ -2229,7 +2285,7 @@
        goto fail;
 
       if (! devwrite (stage2_first_sector - src_part_start, 1,
-                     stage2_first_buffer))
+                     *stage2_first_buffer))
        goto fail;
 
       if (! devwrite (stage2_second_sector - src_part_start, 1,
diff -Naur grub-0.97.orig/stage2/shared.h grub-0.97/stage2/shared.h
--- grub-0.97.orig/stage2/shared.h      2004-06-19 09:40:09.000000000 -0700
+++ grub-0.97/stage2/shared.h   2009-07-05 23:32:43.000000000 -0700
@@ -36,8 +36,8 @@
 
 /* Maybe redirect memory requests through grub_scratch_mem. */
 #ifdef GRUB_UTIL
-extern char *grub_scratch_mem;
-# define RAW_ADDR(x) ((x) + (int) grub_scratch_mem)
+extern void *grub_scratch_mem;
+# define RAW_ADDR(x) ((x) + (unsigned long) grub_scratch_mem)
 # define RAW_SEG(x) (RAW_ADDR ((x) << 4) >> 4)
 #else
 # define RAW_ADDR(x) (x)