Alexandre Oliva writes:

This patch adds code to uClibc to support a new ABI designed for the
FR-V architecture, that enables text segments of executables and
shared libraries to be shared by multiple processes on an OS such as
uClinux, that can run on FR-V processors without an MMU.

Patches for binutils and GCC have just been posted in the
corresponding mailing lists.  The binutils patch was approved,
but there's one additional patch pending review, that I posted
this week.  An updated GCC patch will be posted to
gcc-patches@gcc.gnu.org as soon as I complete testing (I used a
known-good compiler to test the uClibc patch below).

Since the existing dynamic loader code didn't support independent
relocation of segments, it required changes that were somewhat
extensive.  I've added a number of new machine-specific macros to try
to keep the platform and ABI-specific details outside the generic
code.  I hope this is not a problem.

1 files changed, 628 insertions, 0 deletions

diff --git a/ldso/ldso/frv/dl-sysdep.h b/ldso/ldso/frv/dl-sysdep.h
new file mode 100644
index 000000000..ab3b09cd1
--- /dev/null
+++ b/ldso/ldso/frv/dl-sysdep.h
@@ -0,0 +1,628 @@
+     /* Copyright (C) 2003, 2004 Red Hat, Inc.
+	Contributed by Alexandre Oliva <aoliva@redhat.com>
+	Based on ../i386/dl-sysdep.h
+
+This file is part of uClibc.
+
+uClibc is free software; you can redistribute it and/or modify it
+under the terms of the GNU Lesser General Public License as
+published by the Free Software Foundation; either version 2.1 of the
+License, or (at your option) any later version.
+
+uClibc is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with uClibc; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
+USA.  */
+
+/*
+ * Various assembly language/system dependent  hacks that are required
+ * so that we can minimize the amount of platform specific code.
+ */
+
+/*
+ * Define this if the system uses RELOCA.
+ */
+#undef ELF_USES_RELOCA
+
+/*
+ * Get a pointer to the argv array.  On many platforms this can be just
+ * the address if the first argument, on other platforms we need to
+ * do something a little more subtle here.
+ */
+#define GET_ARGV(ARGVP, ARGS) ARGVP = ((unsigned long*) ARGS)
+
+/*
+ * Compute the GOT address.  On several platforms, we use assembly
+ * here.  on FR-V FDPIC, there's no way to compute the GOT address,
+ * since the offset between text and data is not fixed, so we arrange
+ * for the assembly _dl_boot to pass this value as an argument to
+ * _dl_boot.  */
+#define DL_BOOT_COMPUTE_GOT(got) ((got) = dl_boot_got_pointer)
+
+#define DL_BOOT_COMPUTE_DYN(dpnt, got, load_addr) \
+  ((dpnt) = dl_boot_ldso_dyn_pointer)
+
+/*
+ * Initialization sequence for a GOT.  Copy the resolver function
+ * descriptor and the pointer to the elf_resolve/link_map data
+ * structure.  Initialize the got_value in the module while at that.
+ */
+#define INIT_GOT(GOT_BASE,MODULE) \
+{				\
+  (MODULE)->loadaddr.got_value = (GOT_BASE); \
+  GOT_BASE[0] = ((unsigned long *)&_dl_linux_resolve)[0]; \
+  GOT_BASE[1] = ((unsigned long *)&_dl_linux_resolve)[1]; \
+  GOT_BASE[2] = (unsigned long) MODULE; \
+}
+
+/*
+ * Here is a macro to perform a relocation.  This is only used when
+ * bootstrapping the dynamic loader.  RELP is the relocation that we
+ * are performing, REL is the pointer to the address we are relocating.
+ * SYMBOL is the symbol involved in the relocation, and LOAD is the
+ * load address.
+ */
+#define PERFORM_BOOTSTRAP_RELOC(RELP,REL,SYMBOL,LOAD,SYMTAB) \
+	switch(ELF32_R_TYPE((RELP)->r_info)){				\
+	case R_FRV_32:							\
+	  *(REL) += (SYMBOL);						\
+	  break;							\
+	case R_FRV_FUNCDESC_VALUE:					\
+	  {								\
+	    struct funcdesc_value fv = {				\
+	      (void*)((SYMBOL) + *(REL)),				\
+	      (LOAD).got_value						\
+	    };								\
+	    *(struct funcdesc_value volatile *)(REL) = fv;		\
+	    break;							\
+	  }								\
+	default:							\
+	  _dl_exit(1);							\
+	}
+
+/*
+ * Transfer control to the user's application, once the dynamic loader
+ * is done.  We return the address of the function's entry point to
+ * _dl_boot, see boot1_arch.h.
+ */
+#define START()	do {							\
+  struct elf_resolve *exec_mod = _dl_loaded_modules;			\
+  dl_main_funcdesc->entry_point = _dl_elf_main;				\
+  while (exec_mod->libtype != elf_executable)				\
+    exec_mod = exec_mod->next;						\
+  dl_main_funcdesc->got_value = exec_mod->loadaddr.got_value;		\
+  /* _dl_dprintf(2, "entry point is (%x,%x)\n", dl_main_funcdesc->entry_point, dl_main_funcdesc->got_value); */ \
+  return;								\
+} while (0)
+
+
+
+/* Here we define the magic numbers that this dynamic loader should accept */
+
+#define MAGIC1 EM_CYGNUS_FRV
+#undef  MAGIC2
+/* Used for error messages */
+#define ELF_TARGET "FR-V"
+
+struct elf_resolve;
+
+struct funcdesc_value
+{
+  void *entry_point;
+  void *got_value;
+} __attribute__((__aligned__(8)));
+
+
+extern int _dl_linux_resolve(void) __attribute__((__visibility__("hidden")));
+
+#define do_rem(result, n, base)  result = (n % base)
+
+/* 4096 bytes alignment */
+#define PAGE_ALIGN 0xfffff000
+#define ADDR_ALIGN 0xfff
+#define OFFS_ALIGN 0x7ffff000
+
+struct funcdesc_ht;
+
+/* We must force strings used early in the bootstrap into the data
+   segment, such that they are referenced with GOTOFF instead of
+   GPREL, because GPREL needs the GOT to have already been
+   relocated.  */
+#define SEND_EARLY_STDERR(S) \
+  do { static char __s[] = (S); SEND_STDERR (__s); } while (0)
+
+#include <bits/elf-fdpic.h>
+#ifdef __USE_GNU
+# include <link.h>
+#else
+# define __USE_GNU
+# include <link.h>
+# undef __USE_GNU
+#endif
+#include <dl-syscall.h>
+#include <dl-string.h>
+
+/* These are declared in ldso.h, after it includes dl-elf.h that
+   includes ourselves.  */
+extern void *_dl_malloc(int size);
+extern void _dl_free(void *);
+extern void _dl_dprintf(int, const char *, ...);
+
+
+#ifndef _dl_assert
+# define _dl_assert(expr)
+#endif
+
+/* Initialize a DL_LOADADDR_TYPE given a got pointer and a complete
+   load map.  */
+inline static void
+__dl_init_loadaddr_map (struct elf32_fdpic_loadaddr *loadaddr, void *got_value,
+			struct elf32_fdpic_loadmap *map)
+{
+  if (map->version != 0)
+    {
+      SEND_EARLY_STDERR ("Invalid loadmap version number\n");
+      _dl_exit(-1);
+    }
+  if (map->nsegs == 0)
+    {
+      SEND_EARLY_STDERR ("Invalid segment count in loadmap\n");
+      _dl_exit(-1);
+    }
+  loadaddr->got_value = got_value;
+  loadaddr->map = map;
+}
+
+/* Figure out how many LOAD segments there are in the given headers,
+   and allocate a block for the load map big enough for them.
+   got_value will be properly initialized later on, with INIT_GOT.  */
+inline static int
+__dl_init_loadaddr (struct elf32_fdpic_loadaddr *loadaddr, Elf32_Phdr *ppnt,
+		    int pcnt)
+{
+  int count = 0, i;
+  size_t size;
+
+  for (i = 0; i < pcnt; i++)
+    if (ppnt[i].p_type == PT_LOAD)
+      count++;
+
+  loadaddr->got_value = 0;
+
+  size = sizeof (struct elf32_fdpic_loadmap)
+    + sizeof (struct elf32_fdpic_loadseg) * count;
+  loadaddr->map = _dl_malloc (size);
+  if (! loadaddr->map)
+    _dl_exit (-1);
+
+  loadaddr->map->version = 0;
+  loadaddr->map->nsegs = 0;
+
+  return count;
+}
+
+/* Incrementally initialize a load map.  */
+inline static void
+__dl_init_loadaddr_hdr (struct elf32_fdpic_loadaddr loadaddr, void *addr,
+			Elf32_Phdr *phdr, int maxsegs)
+{
+  struct elf32_fdpic_loadseg *segdata;
+
+  if (loadaddr.map->nsegs == maxsegs)
+    _dl_exit (-1);
+
+  segdata = &loadaddr.map->segs[loadaddr.map->nsegs++];
+  segdata->addr = (Elf32_Addr) addr;
+  segdata->p_vaddr = phdr->p_vaddr;
+  segdata->p_memsz = phdr->p_memsz;
+
+#if defined (__SUPPORT_LD_DEBUG__)
+  {
+    extern char *_dl_debug;
+    extern int _dl_debug_file;
+    if (_dl_debug)
+      _dl_dprintf(_dl_debug_file, "%i: mapped %x at %x, size %x\n",
+		  loadaddr.map->nsegs-1,
+		  segdata->p_vaddr, segdata->addr, segdata->p_memsz);
+  }
+#endif
+}
+
+inline static void __dl_loadaddr_unmap
+(struct elf32_fdpic_loadaddr loadaddr, struct funcdesc_ht *funcdesc_ht);
+
+/* Figure out whether the given address is in one of the mapped
+   segments.  */
+inline static int
+__dl_addr_in_loadaddr (void *p, struct elf32_fdpic_loadaddr loadaddr)
+{
+  struct elf32_fdpic_loadmap *map = loadaddr.map;
+  int c;
+
+  for (c = 0; c < map->nsegs; c++)
+    if ((void*)map->segs[c].addr <= p
+	&& (char*)p < (char*)map->segs[c].addr + map->segs[c].p_memsz)
+      return 1;
+
+  return 0;
+}
+
+inline static void * _dl_funcdesc_for (void *entry_point, void *got_value);
+
+#define DL_LOADADDR_TYPE struct elf32_fdpic_loadaddr
+
+#define DL_RELOC_ADDR(ADDR, LOADADDR) \
+  (__reloc_pointer ((void*)(ADDR), (LOADADDR).map))
+
+#define DL_ADDR_TO_FUNC_PTR(ADDR, LOADADDR) \
+  ((void(*)(void)) _dl_funcdesc_for ((void*)(ADDR), (LOADADDR).got_value))
+
+#define _dl_stabilize_funcdesc(val) \
+  ({ asm ("" : "+m" (*(val))); (val); })
+
+#define DL_CALL_FUNC_AT_ADDR(ADDR, LOADADDR, SIGNATURE, ...) \
+  ({ struct funcdesc_value fd = { (void*)(ADDR), (LOADADDR).got_value }; \
+     void (*pf)(void) = (void*) _dl_stabilize_funcdesc (&fd); \
+     (* SIGNATURE pf)(__VA_ARGS__); })
+
+#define DL_INIT_LOADADDR_BOOT(LOADADDR, BASEADDR) \
+  (__dl_init_loadaddr_map (&(LOADADDR), dl_boot_got_pointer, \
+			   dl_boot_ldsomap ?: dl_boot_progmap))
+
+#define DL_INIT_LOADADDR_PROG(LOADADDR, BASEADDR) \
+  (__dl_init_loadaddr_map (&(LOADADDR), 0, dl_boot_progmap))
+
+#define DL_INIT_LOADADDR_EXTRA_DECLS \
+  int dl_init_loadaddr_load_count;
+#define DL_INIT_LOADADDR(LOADADDR, BASEADDR, PHDR, PHDRCNT) \
+  (dl_init_loadaddr_load_count = \
+     __dl_init_loadaddr (&(LOADADDR), (PHDR), (PHDRCNT)))
+#define DL_INIT_LOADADDR_HDR(LOADADDR, ADDR, PHDR) \
+  (__dl_init_loadaddr_hdr ((LOADADDR), (ADDR), (PHDR), \
+			   dl_init_loadaddr_load_count))
+#define DL_LOADADDR_UNMAP(LOADADDR, LEN) \
+  (__dl_loadaddr_unmap ((LOADADDR), (NULL)))
+#define DL_LIB_UNMAP(LIB, LEN) \
+  (__dl_loadaddr_unmap ((LIB)->loadaddr, (LIB)->funcdesc_ht))
+#define DL_LOADADDR_BASE(LOADADDR) \
+  ((LOADADDR).got_value)
+
+#define DL_ADDR_IN_LOADADDR(ADDR, TPNT, TFROM) \
+  (! (TFROM) && __dl_addr_in_loadaddr ((void*)(ADDR), (TPNT)->loadaddr))
+
+/* We only support loading FDPIC independently-relocatable shared
+   libraries.  It probably wouldn't be too hard to support loading
+   shared libraries that require relocation by the same amount, but we
+   don't know that they exist or would be useful, and the dynamic
+   loader code could leak the whole-library map unless we keeping a
+   bit more state for DL_LOADADDR_UNMAP and DL_LIB_UNMAP, so let's
+   keep things simple for now.  */
+#define DL_CHECK_LIB_TYPE(epnt, piclib, _dl_progname, libname) \
+do \
+{ \
+  if (((epnt)->e_flags & EF_FRV_FDPIC) && ! ((epnt)->e_flags & EF_FRV_PIC)) \
+    (piclib) = 2; \
+  else \
+    { \
+      _dl_internal_error_number = LD_ERROR_NOTDYN; \
+      _dl_dprintf(2, "%s: '%s' is not an FDPIC shared library" \
+		  "\n", (_dl_progname), (libname)); \
+      _dl_close(infile); \
+      return NULL; \
+    } \
+} \
+while (0)  
+
+/* We want want to apply all relocations in the interpreter during
+   bootstrap.  Because of this, we have to skip the interpreter
+   relocations in _dl_parse_relocation_information(), see
+   elfinterp.c.  */
+#define DL_SKIP_BOOTSTRAP_RELOC(SYMTAB, INDEX, STRTAB) 0
+
+#ifdef __NR_pread
+#define _DL_PREAD(FD, BUF, SIZE, OFFSET) \
+  (_dl_pread((FD), (BUF), (SIZE), (OFFSET)))
+#endif
+
+#include <dl-hash.h>
+
+/* The hashcode handling code below is heavily inspired in libiberty's
+   hashtab code, but with most adaptation points and support for
+   deleting elements removed.
+
+   Copyright (C) 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
+   Contributed by Vladimir Makarov (vmakarov@cygnus.com).  */
+
+inline static unsigned long
+higher_prime_number (unsigned long n)
+{
+  /* These are primes that are near, but slightly smaller than, a
+     power of two.  */
+  static const unsigned long primes[] = {
+    (unsigned long) 7,
+    (unsigned long) 13,
+    (unsigned long) 31,
+    (unsigned long) 61,
+    (unsigned long) 127,
+    (unsigned long) 251,
+    (unsigned long) 509,
+    (unsigned long) 1021,
+    (unsigned long) 2039,
+    (unsigned long) 4093,
+    (unsigned long) 8191,
+    (unsigned long) 16381,
+    (unsigned long) 32749,
+    (unsigned long) 65521,
+    (unsigned long) 131071,
+    (unsigned long) 262139,
+    (unsigned long) 524287,
+    (unsigned long) 1048573,
+    (unsigned long) 2097143,
+    (unsigned long) 4194301,
+    (unsigned long) 8388593,
+    (unsigned long) 16777213,
+    (unsigned long) 33554393,
+    (unsigned long) 67108859,
+    (unsigned long) 134217689,
+    (unsigned long) 268435399,
+    (unsigned long) 536870909,
+    (unsigned long) 1073741789,
+    (unsigned long) 2147483647,
+					/* 4294967291L */
+    ((unsigned long) 2147483647) + ((unsigned long) 2147483644),
+  };
+
+  const unsigned long *low = &primes[0];
+  const unsigned long *high = &primes[sizeof(primes) / sizeof(primes[0])];
+
+  while (low != high)
+    {
+      const unsigned long *mid = low + (high - low) / 2;
+      if (n > *mid)
+	low = mid + 1;
+      else
+	high = mid;
+    }
+
+#if 0
+  /* If we've run out of primes, abort.  */
+  if (n > *low)
+    {
+      fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
+      abort ();
+    }
+#endif
+
+  return *low;
+}
+
+struct funcdesc_ht
+{
+  /* Table itself.  */
+  struct funcdesc_value **entries;
+
+  /* Current size (in entries) of the hash table */
+  size_t size;
+
+  /* Current number of elements.  */
+  size_t n_elements;
+};  
+
+inline static int
+hash_pointer (const void *p)
+{
+  return (int) ((long)p >> 3);
+}
+
+inline static struct funcdesc_ht *
+htab_create (void)
+{
+  struct funcdesc_ht *ht = _dl_malloc (sizeof (struct funcdesc_ht));
+
+  if (! ht)
+    return NULL;
+  ht->size = 3;
+  ht->entries = _dl_malloc (sizeof (struct funcdesc_ht_value *) * ht->size);
+  if (! ht->entries)
+    return NULL;
+  
+  ht->n_elements = 0;
+
+  _dl_memset (ht->entries, 0, sizeof (struct funcdesc_ht_value *) * ht->size);
+  
+  return ht;
+}
+
+inline static void
+htab_delete (struct funcdesc_ht *htab)
+{
+  int i;
+
+  for (i = htab->size - 1; i >= 0; i--)
+    if (htab->entries[i])
+      _dl_free (htab->entries[i]);
+
+  _dl_free (htab->entries);
+  _dl_free (htab);
+}
+
+/* Similar to htab_find_slot, but without several unwanted side effects:
+    - Does not call htab->eq_f when it finds an existing entry.
+    - Does not change the count of elements/searches/collisions in the
+      hash table.
+   This function also assumes there are no deleted entries in the table.
+   HASH is the hash value for the element to be inserted.  */
+
+inline static struct funcdesc_value **
+find_empty_slot_for_expand (struct funcdesc_ht *htab, int hash)
+{
+  size_t size = htab->size;
+  unsigned int index = hash % size;
+  struct funcdesc_value **slot = htab->entries + index;
+  int hash2;
+
+  if (! *slot)
+    return slot;
+
+  hash2 = 1 + hash % (size - 2);
+  for (;;)
+    {
+      index += hash2;
+      if (index >= size)
+	index -= size;
+
+      slot = htab->entries + index;
+      if (! *slot)
+	return slot;
+    }
+}
+
+/* The following function changes size of memory allocated for the
+   entries and repeatedly inserts the table elements.  The occupancy
+   of the table after the call will be about 50%.  Naturally the hash
+   table must already exist.  Remember also that the place of the
+   table entries is changed.  If memory allocation failures are allowed,
+   this function will return zero, indicating that the table could not be
+   expanded.  If all goes well, it will return a non-zero value.  */
+
+inline static int
+htab_expand (struct funcdesc_ht *htab)
+{
+  struct funcdesc_value **oentries;
+  struct funcdesc_value **olimit;
+  struct funcdesc_value **p;
+  struct funcdesc_value **nentries;
+  size_t nsize;
+
+  oentries = htab->entries;
+  olimit = oentries + htab->size;
+
+  /* Resize only when table after removal of unused elements is either
+     too full or too empty.  */
+  if (htab->n_elements * 2 > htab->size)
+    nsize = higher_prime_number (htab->n_elements * 2);
+  else
+    nsize = htab->size;
+
+  nentries = _dl_malloc (sizeof (struct funcdesc_value *) * nsize);
+  _dl_memset (nentries, 0, sizeof (struct funcdesc_value *) * nsize);
+  if (nentries == NULL)
+    return 0;
+  htab->entries = nentries;
+  htab->size = nsize;
+
+  p = oentries;
+  do
+    {
+      if (*p)
+	*find_empty_slot_for_expand (htab, hash_pointer ((*p)->entry_point))
+	  = *p;
+
+      p++;
+    }
+  while (p < olimit);
+
+  _dl_free (oentries);
+  return 1;
+}
+
+/* This function searches for a hash table slot containing an entry
+   equal to the given element.  To delete an entry, call this with
+   INSERT = 0, then call htab_clear_slot on the slot returned (possibly
+   after doing some checks).  To insert an entry, call this with
+   INSERT = 1, then write the value you want into the returned slot.
+   When inserting an entry, NULL may be returned if memory allocation
+   fails.  */
+
+inline static struct funcdesc_value **
+htab_find_slot (struct funcdesc_ht *htab, void *ptr)
+{
+  unsigned int index;
+  int hash, hash2;
+  size_t size;
+  struct funcdesc_value **entry;
+
+  if (htab->size * 3 <= htab->n_elements * 4
+      && htab_expand (htab) == 0)
+    return NULL;
+
+  hash = hash_pointer (ptr);
+
+  size = htab->size;
+  index = hash % size;
+
+  entry = &htab->entries[index];
+  if (!*entry)
+    goto empty_entry;
+  else if ((*entry)->entry_point == ptr)
+    return entry;
+      
+  hash2 = 1 + hash % (size - 2);
+  for (;;)
+    {
+      index += hash2;
+      if (index >= size)
+	index -= size;
+      
+      entry = &htab->entries[index];
+      if (!*entry)
+	goto empty_entry;
+      else if ((*entry)->entry_point == ptr)
+	return entry;
+    }
+
+ empty_entry:
+  htab->n_elements++;
+  return entry;
+}
+
+void *
+_dl_funcdesc_for (void *entry_point, void *got_value)
+{
+  struct elf_resolve *tpnt = ((void**)got_value)[2];
+  struct funcdesc_ht *ht = tpnt->funcdesc_ht;
+  struct funcdesc_value **entry;
+
+  _dl_assert (got_value == tpnt->loadaddr.got_value);
+
+  if (! ht)
+    {
+      ht = htab_create ();
+      if (! ht)
+	return (void*)-1;
+      tpnt->funcdesc_ht = ht;
+    }
+
+  entry = htab_find_slot (ht, entry_point);
+  if (*entry)
+    {
+      _dl_assert ((*entry)->entry_point == entry_point);
+      return _dl_stabilize_funcdesc (*entry);
+    }
+
+  *entry = _dl_malloc (sizeof (struct funcdesc_value));
+  (*entry)->entry_point = entry_point;
+  (*entry)->got_value = got_value;
+
+  return _dl_stabilize_funcdesc (*entry);
+}
+
+void
+__dl_loadaddr_unmap (struct elf32_fdpic_loadaddr loadaddr,
+		     struct funcdesc_ht *funcdesc_ht)
+{
+  int i;
+
+  for (i = 0; i < loadaddr.map->nsegs; i++)
+    _dl_munmap ((void*)loadaddr.map->segs[i].addr,
+		loadaddr.map->segs[i].p_memsz);
+
+  _dl_free (loadaddr.map);
+  if (funcdesc_ht)
+    htab_delete (funcdesc_ht);
+}