elf: Use mmap to map in read-only sections

Message ID 20240301043032.2957895-1-hjl.tools@gmail.com
State Unresolved
Headers
Series elf: Use mmap to map in read-only sections |

Checks

Context Check Description
snail/binutils-gdb-check warning Git am fail log

Commit Message

H.J. Lu March 1, 2024, 4:30 a.m. UTC
  There are many linker input files in LLVM debug build with huge string
sections.  All these string sections can be treated as read-only.  But
linker copies all of them into memory which consumes huge amount of
memory and slows down linker significantly.  Add _bfd_mmap_readonly
and _bfd_mmap_readonly_local to mmap in reado-only sections.  It improves
linker performance for LLVM debug build by more than 10x.

NB: All string sections in valid ELF inputs must be null terminated.
There is no need to terminate it again and string sections are mmapped
as read-only.

	* bfd.c (bfd_mmapped_entry): New.
	(bfd_mmapped): Likewise.
	(bfd): Add mmapped.
	* bfdwin.c (bfd_get_file_window): Use _bfd_pagesize.
	* cache.c (cache_bmmap): Remove pagesize_m1 and use pagesize_m1
	instead.
	* elf.c (bfd_elf_get_str_section): Call _bfd_mmap_readonly
	instead of _bfd_alloc_and_read.  Don't terminate the string
	section again.
	(get_hash_table_data): Call _bfd_mmap_readonly_local and
	_bfd_munmap_readonly_local instead of _bfd_malloc_and_read and
	free.
	(_bfd_elf_get_dynamic_symbols): Call _bfd_mmap_readonly
	instead of _bfd_alloc_and_read.  Don't terminate the string
	section again.  Call _bfd_mmap_readonly_local and
	_bfd_munmap_readonly_local instead of _bfd_malloc_and_read and
	free.
	(_bfd_elf_slurp_version_tables): Call _bfd_mmap_readonly_local
	and _bfd_munmap_readonly_local instead of _bfd_malloc_and_read
	and free.
	* elflink.c (bfd_elf_link_record_dynamic_symbol): Use bfd_malloc
	to get the unversioned symbol.
	* libbfd-in.h (_bfd_pagesize): New.
	(_bfd_pagesize_m1): Likewise.
	(_bfd_mmap_readonly): Likewise.
	(_bfd_mmap_readonly_local): Likewise.
	(_bfd_munmap_readonly_local): Likewise.
	* libbfd.c (MAP_ANONYMOUS): New. Define if not defined.
	(bfd_allocate_mmapped_page): New.
	(bfd_mmap_readonly_local_1): Likewise.
	(_bfd_mmap_readonly_local): Likewise.
	(_bfd_munmap_readonly_local): Likewise.
	(_bfd_mmap_readonly): Likewise.
	(_bfd_pagesize): Likewise.
	(_bfd_pagesize_m1): Likewise.
	(bfd_init_pagesize): Likewise.
	* ynx-core.c (lynx_core_file_p): Use _bfd_pagesize.
	* opncls.c: Include <sys/mman.h>.
	(_bfd_delete_bfd): Munmap mmapped memories.
	* bfd-in2.h: Regenerated.
	* libbfd.h: Likewise.
---
 bfd/bfd-in2.h   |  17 +++++++
 bfd/bfd.c       |  17 +++++++
 bfd/bfdwin.c    |   8 +--
 bfd/cache.c     |  11 ++--
 bfd/elf.c       |  65 +++++++++++++++---------
 bfd/elflink.c   |  16 +++---
 bfd/libbfd-in.h |  18 +++++++
 bfd/libbfd.c    | 132 ++++++++++++++++++++++++++++++++++++++++++++++++
 bfd/libbfd.h    |  18 +++++++
 bfd/lynx-core.c |   2 +-
 bfd/opncls.c    |  16 ++++++
 11 files changed, 275 insertions(+), 45 deletions(-)
  

Patch

diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index a335df522d2..934c73e14e8 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -1951,6 +1951,20 @@  struct bfd_build_id
     bfd_byte data[1];
   };
 
+struct bfd_mmapped_entry
+  {
+    void *addr;
+    bfd_size_type size;
+  };
+
+struct bfd_mmapped
+  {
+    struct bfd_mmapped *next;
+    unsigned int max_entry;
+    unsigned int next_entry;
+    struct bfd_mmapped_entry entries[1];
+  };
+
 struct bfd
 {
   /* The filename the application opened the BFD with.  */
@@ -2280,6 +2294,9 @@  struct bfd
 
   /* For input BFDs, the build ID, if the object has one. */
   const struct bfd_build_id *build_id;
+
+  /* For input BFDs, mmapped entries. */
+  struct bfd_mmapped *mmapped;
 };
 
 static inline const char *
diff --git a/bfd/bfd.c b/bfd/bfd.c
index 6c822656cc8..34c571f8f7b 100644
--- a/bfd/bfd.c
+++ b/bfd/bfd.c
@@ -74,6 +74,20 @@  EXTERNAL
 .    bfd_byte data[1];
 .  };
 .
+.struct bfd_mmapped_entry
+.  {
+.    void *addr;
+.    bfd_size_type size;
+.  };
+.
+.struct bfd_mmapped
+.  {
+.    struct bfd_mmapped *next;
+.    unsigned int max_entry;
+.    unsigned int next_entry;
+.    struct bfd_mmapped_entry entries[1];
+.  };
+.
 
 CODE_FRAGMENT
 .struct bfd
@@ -406,6 +420,9 @@  CODE_FRAGMENT
 .
 .  {* For input BFDs, the build ID, if the object has one. *}
 .  const struct bfd_build_id *build_id;
+.
+.  {* For input BFDs, mmapped entries. *}
+.  struct bfd_mmapped *mmapped;
 .};
 .
 
diff --git a/bfd/bfdwin.c b/bfd/bfdwin.c
index beb17398744..d9ce0d25e90 100644
--- a/bfd/bfdwin.c
+++ b/bfd/bfdwin.c
@@ -165,7 +165,7 @@  bfd_get_file_window (bfd *abfd,
 		     bool writable)
 {
   static int ok_to_map = 1;
-  static size_t pagesize;
+  size_t pagesize = _bfd_pagesize;
   bfd_window_internal *i = windowp->i;
   bfd_size_type size_to_alloc = size;
 
@@ -175,12 +175,6 @@  bfd_get_file_window (bfd *abfd,
 	     windowp, windowp->data, (unsigned long) windowp->size,
 	     windowp->i, writable);
 
-  /* Make sure we know the page size, so we can be friendly to mmap.  */
-  if (pagesize == 0)
-    pagesize = getpagesize ();
-  if (pagesize == 0)
-    abort ();
-
   if (i == NULL)
     {
       i = bfd_zmalloc (sizeof (bfd_window_internal));
diff --git a/bfd/cache.c b/bfd/cache.c
index 4c00c00f8d5..2331262fb2e 100644
--- a/bfd/cache.c
+++ b/bfd/cache.c
@@ -498,7 +498,6 @@  cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED,
 #ifdef HAVE_MMAP
   else
     {
-      static uintptr_t pagesize_m1;
       FILE *f;
       file_ptr pg_offset;
       bfd_size_type pg_len;
@@ -510,12 +509,10 @@  cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED,
 	  return ret;
 	}
 
-      if (pagesize_m1 == 0)
-	pagesize_m1 = getpagesize () - 1;
-
       /* Align.  */
-      pg_offset = offset & ~pagesize_m1;
-      pg_len = (len + (offset - pg_offset) + pagesize_m1) & ~pagesize_m1;
+      pg_offset = offset & ~_bfd_pagesize_m1;
+      pg_len = ((len + (offset - pg_offset) + _bfd_pagesize_m1)
+		& ~_bfd_pagesize_m1);
 
       ret = mmap (addr, pg_len, prot, flags, fileno (f), pg_offset);
       if (ret == (void *) -1)
@@ -524,7 +521,7 @@  cache_bmmap (struct bfd *abfd ATTRIBUTE_UNUSED,
 	{
 	  *map_addr = ret;
 	  *map_len = pg_len;
-	  ret = (char *) ret + (offset & pagesize_m1);
+	  ret = (char *) ret + (offset & _bfd_pagesize_m1);
 	}
     }
 #endif
diff --git a/bfd/elf.c b/bfd/elf.c
index 8bffd3c5141..82f36625d16 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -289,16 +289,23 @@  bfd_elf_get_str_section (bfd *abfd, unsigned int shindex)
 	 in case the string table is not terminated.  */
       if (shstrtabsize + 1 <= 1
 	  || bfd_seek (abfd, offset, SEEK_SET) != 0
-	  || (shstrtab = _bfd_alloc_and_read (abfd, shstrtabsize + 1,
-					      shstrtabsize)) == NULL)
+	  || (shstrtab = _bfd_mmap_readonly (abfd, shstrtabsize + 1,
+					     shstrtabsize)) == NULL)
 	{
 	  /* Once we've failed to read it, make sure we don't keep
 	     trying.  Otherwise, we'll keep allocating space for
 	     the string table over and over.  */
 	  i_shdrp[shindex]->sh_size = 0;
 	}
-      else
-	shstrtab[shstrtabsize] = '\0';
+      else if (shstrtab[shstrtabsize - 1] != '\0')
+	{
+	  /* It is an error if a string table isn't terminated.  */
+	  _bfd_error_handler
+	    /* xgettext:c-format */
+	    (_("%pB(%pA): string table is corrupt"),
+	     abfd, i_shdrp[shindex]->bfd_section);
+	  return NULL;
+	}
       i_shdrp[shindex]->contents = shstrtab;
     }
   return (char *) shstrtab;
@@ -1940,7 +1947,7 @@  get_hash_table_data (bfd *abfd, bfd_size_type number,
       return NULL;
     }
 
-  e_data = _bfd_malloc_and_read (abfd, size, size);
+  e_data = _bfd_mmap_readonly_local (abfd, size);
   if (e_data == NULL)
     return NULL;
 
@@ -1958,7 +1965,7 @@  get_hash_table_data (bfd *abfd, bfd_size_type number,
     while (number--)
       i_data[number] = bfd_get_64 (abfd, e_data + number * ent_size);
 
-  free (e_data);
+  _bfd_munmap_readonly_local (e_data, size);
   return i_data;
 }
 
@@ -2007,6 +2014,8 @@  _bfd_elf_get_dynamic_symbols (bfd *abfd, Elf_Internal_Phdr *phdr,
   size_t verneed_size = 0;
   size_t extsym_size;
   const struct elf_backend_data *bed;
+  size_t esymbuf_size = 0;
+  size_t dynbuf_size = 0;
 
   /* Return TRUE if symbol table is bad.  */
   if (elf_bad_symtab (abfd))
@@ -2024,7 +2033,8 @@  _bfd_elf_get_dynamic_symbols (bfd *abfd, Elf_Internal_Phdr *phdr,
   if (bfd_seek (abfd, phdr->p_offset, SEEK_SET) != 0)
     goto error_return;
 
-  dynbuf = _bfd_malloc_and_read (abfd, phdr->p_filesz, phdr->p_filesz);
+  dynbuf_size = phdr->p_filesz;
+  dynbuf = _bfd_mmap_readonly_local (abfd, dynbuf_size);
   if (dynbuf == NULL)
     goto error_return;
 
@@ -2102,11 +2112,17 @@  _bfd_elf_get_dynamic_symbols (bfd *abfd, Elf_Internal_Phdr *phdr,
     goto error_return;
 
   /* Dynamic string table must be valid until ABFD is closed.  */
-  strbuf = (char *) _bfd_alloc_and_read (abfd, dt_strsz + 1, dt_strsz);
+  strbuf = (char *) _bfd_mmap_readonly (abfd, dt_strsz + 1, dt_strsz);
   if (strbuf == NULL)
     goto error_return;
-  /* Since this is a string table, make sure that it is terminated.  */
-  strbuf[dt_strsz] = 0;
+  if (strbuf[dt_strsz - 1] != 0)
+    {
+      /* It is an error if a string table is't terminated.  */
+      _bfd_error_handler
+	/* xgettext:c-format */
+	(_("%pB: DT_STRTAB table is corrupt"), abfd);
+      goto error_return;
+    }
 
   /* Get the real symbol count from DT_HASH or DT_GNU_HASH.  Prefer
      DT_HASH since it is simpler than DT_GNU_HASH.  */
@@ -2281,7 +2297,8 @@  _bfd_elf_get_dynamic_symbols (bfd *abfd, Elf_Internal_Phdr *phdr,
   if (filepos == (file_ptr) -1
       || bfd_seek (abfd, filepos, SEEK_SET) != 0)
     goto error_return;
-  esymbuf = _bfd_malloc_and_read (abfd, amt, amt);
+  esymbuf_size = amt;
+  esymbuf = _bfd_mmap_readonly_local (abfd, esymbuf_size);
   if (esymbuf == NULL)
     goto error_return;
 
@@ -2325,7 +2342,7 @@  _bfd_elf_get_dynamic_symbols (bfd *abfd, Elf_Internal_Phdr *phdr,
 	goto error_return;
 
       /* DT_VERSYM info must be valid until ABFD is closed.  */
-      versym = _bfd_alloc_and_read (abfd, amt, amt);
+      versym = _bfd_mmap_readonly (abfd, amt, amt);
 
       if (dt_verdef)
 	{
@@ -2337,8 +2354,7 @@  _bfd_elf_get_dynamic_symbols (bfd *abfd, Elf_Internal_Phdr *phdr,
 	    goto error_return;
 
 	  /* DT_VERDEF info must be valid until ABFD is closed.  */
-	  verdef = _bfd_alloc_and_read (abfd, verdef_size,
-					verdef_size);
+	  verdef = _bfd_mmap_readonly (abfd, verdef_size, verdef_size);
 	}
 
       if (dt_verneed)
@@ -2351,8 +2367,8 @@  _bfd_elf_get_dynamic_symbols (bfd *abfd, Elf_Internal_Phdr *phdr,
 	    goto error_return;
 
 	  /* DT_VERNEED info must be valid until ABFD is closed.  */
-	  verneed = _bfd_alloc_and_read (abfd, verneed_size,
-					 verneed_size);
+	  verneed = _bfd_mmap_readonly (abfd, verneed_size,
+					verneed_size);
 	}
     }
 
@@ -2375,8 +2391,8 @@  _bfd_elf_get_dynamic_symbols (bfd *abfd, Elf_Internal_Phdr *phdr,
   /* Restore file position for elf_object_p.  */
   if (bfd_seek (abfd, saved_filepos, SEEK_SET) != 0)
     res = false;
-  free (dynbuf);
-  free (esymbuf);
+  _bfd_munmap_readonly_local (dynbuf, dynbuf_size);
+  _bfd_munmap_readonly_local (esymbuf, esymbuf_size);
   free (gnubuckets);
   free (gnuchains);
   free (mipsxlat);
@@ -9435,6 +9451,7 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
   bfd_byte *contents = NULL;
   unsigned int freeidx = 0;
   size_t amt;
+  size_t size = 0;
 
   if (elf_dynverref (abfd) != 0 || elf_tdata (abfd)->dt_verneed != NULL)
     {
@@ -9471,7 +9488,8 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
 
 	  if (bfd_seek (abfd, hdr->sh_offset, SEEK_SET) != 0)
 	    goto error_return_verref;
-	  contents = _bfd_malloc_and_read (abfd, hdr->sh_size, hdr->sh_size);
+	  size = hdr->sh_size;
+	  contents = _bfd_mmap_readonly_local (abfd, size);
 	  if (contents == NULL)
 	    goto error_return_verref;
 
@@ -9604,7 +9622,7 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
       elf_tdata (abfd)->cverrefs = i;
 
       if (contents != elf_tdata (abfd)->dt_verneed)
-	free (contents);
+	_bfd_munmap_readonly_local (contents, size);
       contents = NULL;
     }
 
@@ -9646,7 +9664,8 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
 
 	  if (bfd_seek (abfd, hdr->sh_offset, SEEK_SET) != 0)
 	    goto error_return_verdef;
-	  contents = _bfd_malloc_and_read (abfd, hdr->sh_size, hdr->sh_size);
+	  size = hdr->sh_size;
+	  contents = _bfd_mmap_readonly_local (abfd, size);
 	  if (contents == NULL)
 	    goto error_return_verdef;
 
@@ -9800,7 +9819,7 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
 	}
 
       if (contents != elf_tdata (abfd)->dt_verdef)
-	free (contents);
+	_bfd_munmap_readonly_local (contents, size);
       contents = NULL;
     }
   else if (default_imported_symver)
@@ -9857,7 +9876,7 @@  _bfd_elf_slurp_version_tables (bfd *abfd, bool default_imported_symver)
  error_return:
   if (contents != elf_tdata (abfd)->dt_verneed
       && contents != elf_tdata (abfd)->dt_verdef)
-    free (contents);
+    _bfd_munmap_readonly_local (contents, size);
   return false;
 }
 
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 5a6cb07b2ce..42029f29f7a 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -549,22 +549,24 @@  bfd_elf_link_record_dynamic_symbol (struct bfd_link_info *info,
 	    return false;
 	}
 
+      char *unversioned_name = NULL;
+
       /* We don't put any version information in the dynamic string
 	 table.  */
       name = h->root.root.string;
       p = strchr (name, ELF_VER_CHR);
       if (p != NULL)
-	/* We know that the p points into writable memory.  In fact,
-	   there are only a few symbols that have read-only names, being
-	   those like _GLOBAL_OFFSET_TABLE_ that are created specially
-	   by the backends.  Most symbols will have names pointing into
-	   an ELF string table read from a file, or to objalloc memory.  */
-	*p = 0;
+	{
+	  unversioned_name = bfd_malloc (p - name + 1);
+	  memcpy (unversioned_name, name, p - name);
+	  unversioned_name[p - name] = 0;
+	  name = unversioned_name;
+	}
 
       indx = _bfd_elf_strtab_add (dynstr, name, p != NULL);
 
       if (p != NULL)
-	*p = ELF_VER_CHR;
+	free (unversioned_name);
 
       if (indx == (size_t) -1)
 	return false;
diff --git a/bfd/libbfd-in.h b/bfd/libbfd-in.h
index b8b2ce7ba09..f0a90a61a47 100644
--- a/bfd/libbfd-in.h
+++ b/bfd/libbfd-in.h
@@ -851,6 +851,9 @@  extern struct bfd_link_info *_bfd_get_link_info (bfd *)
 extern bool _bfd_link_keep_memory (struct bfd_link_info *)
   ATTRIBUTE_HIDDEN;
 
+extern uintptr_t _bfd_pagesize ATTRIBUTE_HIDDEN;
+extern uintptr_t _bfd_pagesize_m1 ATTRIBUTE_HIDDEN;
+
 #if GCC_VERSION >= 7000
 #define _bfd_mul_overflow(a, b, res) __builtin_mul_overflow (a, b, res)
 #else
@@ -888,6 +891,21 @@  _bfd_alloc_and_read (bfd *abfd, bfd_size_type asize, bfd_size_type rsize)
   return NULL;
 }
 
+#ifdef HAVE_MMAP
+extern void *_bfd_mmap_readonly (bfd *, bfd_size_type, bfd_size_type)
+  ATTRIBUTE_HIDDEN;
+extern void *_bfd_mmap_readonly_local (bfd *, bfd_size_type)
+  ATTRIBUTE_HIDDEN;
+extern void _bfd_munmap_readonly_local (void *, bfd_size_type)
+  ATTRIBUTE_HIDDEN;
+#else
+#define _bfd_mmap_readonly(abfd, asize, rsize) \
+  _bfd_alloc_and_read (abfd, asize, rsize)
+#define _bfd_mmap_readonly_local(abfd, rsize) \
+  _bfd_malloc_and_read (abfd, rsize, rsize)
+#define _bfd_munmap_readonly_local(ptr, rsize) free (ptr)
+#endif
+
 static inline void *
 _bfd_malloc_and_read (bfd *abfd, bfd_size_type asize, bfd_size_type rsize)
 {
diff --git a/bfd/libbfd.c b/bfd/libbfd.c
index f8d148c9677..d24392ceb43 100644
--- a/bfd/libbfd.c
+++ b/bfd/libbfd.c
@@ -1326,3 +1326,135 @@  _bfd_generic_init_private_section_data (bfd *ibfd ATTRIBUTE_UNUSED,
 {
   return true;
 }
+
+#ifdef HAVE_MMAP
+#include <sys/mman.h>
+
+#ifndef MAP_ANONYMOUS
+#define MAP_ANONYMOUS  MAP_ANON
+#endif
+
+/* Allocate a page to track mmapped memory and return the page and
+   the first entry.  Return NULL if mmap fails.  */
+
+static struct bfd_mmapped *
+bfd_allocate_mmapped_page (bfd *abfd, struct bfd_mmapped_entry **entry)
+{
+  struct bfd_mmapped * mmapped
+    = (struct bfd_mmapped *) mmap (NULL, _bfd_pagesize,
+				   PROT_READ | PROT_WRITE,
+				   MAP_PRIVATE | MAP_ANONYMOUS,
+				   -1, 0);
+  if (mmapped == MAP_FAILED)
+    return NULL;
+
+  mmapped->next = abfd->mmapped;
+  mmapped->max_entry
+    = ((_bfd_pagesize - offsetof (struct bfd_mmapped, entries))
+       / sizeof (struct bfd_mmapped_entry));
+  mmapped->next_entry = 1;
+  abfd->mmapped = mmapped;
+  *entry = mmapped->entries;
+  return mmapped;
+}
+
+/* Mmap a readonly memory region of RSIZE bytes at the current offset.
+   Return mmap address and size in MAP_ADDR and MAP_SIZE.  Return NULL
+   on invalid input and (void *) -1 for mmap failure.  */
+
+static void *
+bfd_mmap_readonly_local_1 (bfd *abfd, bfd_size_type rsize,
+			   void **map_addr, bfd_size_type *map_size)
+{
+  if (!_bfd_constant_p (rsize))
+    {
+      ufile_ptr filesize = bfd_get_file_size (abfd);
+      if (filesize != 0 && rsize > filesize)
+	{
+	  bfd_set_error (bfd_error_file_truncated);
+	  return NULL;
+	}
+    }
+
+  void *mem;
+  ufile_ptr offset = bfd_tell (abfd);
+  mem = bfd_mmap (abfd, NULL, rsize, PROT_READ, MAP_PRIVATE, offset,
+		  map_addr, map_size);
+  return mem;
+}
+
+/* Mmap a readonly memory region of RSIZE bytes at the current offset.
+   Return NULL on invalid input or mmap failure.  */
+
+void *
+_bfd_mmap_readonly_local (bfd *abfd, bfd_size_type rsize)
+{
+  void *map_addr;
+  bfd_size_type map_size;
+  return bfd_mmap_readonly_local_1 (abfd, rsize, &map_addr, &map_size);
+}
+
+/* Munmap RSIZE bytes at PTR.  */
+
+void
+_bfd_munmap_readonly_local (void *ptr, bfd_size_type rsize)
+{
+  /* NB: Since _bfd_munmap_readonly_local is called like free,
+     PTR may be NULL.  */
+  if (ptr != NULL)
+    munmap (ptr, rsize);
+}
+
+/* Mmap a readonly memory region of RSIZE bytes at the current offset.
+   Return NULL on invalid input or mmap failure.  */
+
+void *
+_bfd_mmap_readonly (bfd *abfd, bfd_size_type asize, bfd_size_type rsize)
+{
+  void *mem, *map_addr;
+  bfd_size_type map_size;
+  mem = bfd_mmap_readonly_local_1 (abfd, rsize, &map_addr, &map_size);
+  if (mem == NULL)
+    return mem;
+  if (mem == (void *) -1)
+    return _bfd_alloc_and_read (abfd, asize, rsize);
+
+  struct bfd_mmapped_entry *entry;
+  unsigned int next_entry;
+  struct bfd_mmapped *mmapped = abfd->mmapped;
+  if (mmapped != NULL
+      && (next_entry = mmapped->next_entry) < mmapped->max_entry)
+    {
+      entry = &mmapped->entries[next_entry];
+      mmapped->next_entry++;
+    }
+  else
+    {
+      mmapped = bfd_allocate_mmapped_page (abfd, &entry);
+      if (mmapped == NULL)
+	{
+	  munmap (map_addr, map_size);
+	  return NULL;
+	}
+    }
+
+  entry->addr = map_addr;
+  entry->size = map_size;
+
+  return mem;
+}
+
+#endif
+
+uintptr_t _bfd_pagesize;
+uintptr_t _bfd_pagesize_m1;
+
+__attribute__ ((unused, constructor))
+static void
+bfd_init_pagesize (void)
+{
+  _bfd_pagesize = getpagesize ();
+  if (_bfd_pagesize == 0)
+    abort ();
+  _bfd_pagesize_m1 = _bfd_pagesize - 1;
+}
diff --git a/bfd/libbfd.h b/bfd/libbfd.h
index a60063b5ae1..f8e20d850d9 100644
--- a/bfd/libbfd.h
+++ b/bfd/libbfd.h
@@ -857,6 +857,9 @@  extern struct bfd_link_info *_bfd_get_link_info (bfd *)
 extern bool _bfd_link_keep_memory (struct bfd_link_info *)
   ATTRIBUTE_HIDDEN;
 
+extern uintptr_t _bfd_pagesize ATTRIBUTE_HIDDEN;
+extern uintptr_t _bfd_pagesize_m1 ATTRIBUTE_HIDDEN;
+
 #if GCC_VERSION >= 7000
 #define _bfd_mul_overflow(a, b, res) __builtin_mul_overflow (a, b, res)
 #else
@@ -894,6 +897,21 @@  _bfd_alloc_and_read (bfd *abfd, bfd_size_type asize, bfd_size_type rsize)
   return NULL;
 }
 
+#ifdef HAVE_MMAP
+extern void *_bfd_mmap_readonly (bfd *, bfd_size_type, bfd_size_type)
+  ATTRIBUTE_HIDDEN;
+extern void *_bfd_mmap_readonly_local (bfd *, bfd_size_type)
+  ATTRIBUTE_HIDDEN;
+extern void _bfd_munmap_readonly_local (void *, bfd_size_type)
+  ATTRIBUTE_HIDDEN;
+#else
+#define _bfd_mmap_readonly(abfd, asize, rsize) \
+  _bfd_alloc_and_read (abfd, asize, rsize)
+#define _bfd_mmap_readonly_local(abfd, rsize) \
+  _bfd_malloc_and_read (abfd, rsize, rsize)
+#define _bfd_munmap_readonly_local(ptr, rsize) free (ptr)
+#endif
+
 static inline void *
 _bfd_malloc_and_read (bfd *abfd, bfd_size_type asize, bfd_size_type rsize)
 {
diff --git a/bfd/lynx-core.c b/bfd/lynx-core.c
index 44d94ad8745..9ec5a0d2028 100644
--- a/bfd/lynx-core.c
+++ b/bfd/lynx-core.c
@@ -96,7 +96,7 @@  lynx_core_file_p (bfd *abfd)
   asection *newsect;
   size_t amt;
 
-  pagesize = getpagesize ();	/* Serious cross-target issue here...  This
+  pagesize = _bfd_pagesize;	/* Serious cross-target issue here...  This
 				   really needs to come from a system-specific
 				   header file.  */
 
diff --git a/bfd/opncls.c b/bfd/opncls.c
index a0a5c40fba8..245e239c8e4 100644
--- a/bfd/opncls.c
+++ b/bfd/opncls.c
@@ -27,6 +27,10 @@ 
 #include "libiberty.h"
 #include "elf-bfd.h"
 
+#ifdef HAVE_MMAP
+#include <sys/mman.h>
+#endif
+
 #ifndef S_IXUSR
 #define S_IXUSR 0100	/* Execute by owner.  */
 #endif
@@ -176,6 +180,18 @@  _bfd_delete_bfd (bfd *abfd)
   else
     free ((char *) bfd_get_filename (abfd));
 
+#ifdef HAVE_MMAP
+  struct bfd_mmapped *mmapped, *next;
+  for (mmapped = abfd->mmapped; mmapped != NULL; mmapped = next)
+    {
+      struct bfd_mmapped_entry *entries = mmapped->entries;
+      next = mmapped->next;
+      for (unsigned int i = 0; i < mmapped->next_entry; i++)
+	munmap (entries[i].addr, entries[i].size);
+      munmap (mmapped, _bfd_pagesize);
+    }
+#endif
+
   free (abfd->arelt_data);
   free (abfd);
 }