path: root/sysdeps/mips/dl-trampoline.c

/* PLT trampoline.  MIPS version.
   Copyright (C) 1996-2023 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library 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.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library.  If not, see
   <https://www.gnu.org/licenses/>.  */

/*  FIXME: Profiling of shared libraries is not implemented yet.  */

#include <sysdep.h>
#include <link.h>
#include <elf.h>
#include <ldsodefs.h>
#include <dl-machine.h>
#include <sysdep-cancel.h>

/* Get link map for callers object containing STUB_PC.  */
static inline struct link_map *
elf_machine_runtime_link_map (ElfW(Addr) gpreg, ElfW(Addr) stub_pc)
{
  extern int _dl_mips_gnu_objects;

  /* got[1] is reserved to keep its link map address for the shared
     object generated by the gnu linker.  If all are such objects, we
     can find the link map from current GPREG simply.  If not so, get
     the link map for caller's object containing STUB_PC.  */

  if (_dl_mips_gnu_objects)
    {
      ElfW(Addr) *got = elf_mips_got_from_gpreg (gpreg);
      ElfW(Word) g1;

      g1 = ((ElfW(Word) *) got)[1];

      if ((g1 & ELF_MIPS_GNU_GOT1_MASK) != 0)
	{
	  struct link_map *l =
	    (struct link_map *) (g1 & ~ELF_MIPS_GNU_GOT1_MASK);
	  ElfW(Addr) base, limit;
	  const ElfW(Phdr) *p = l->l_phdr;
	  ElfW(Half) this, nent = l->l_phnum;

	  /* For the common case of a stub being called from the containing
	     object, STUB_PC will point to somewhere within the object that
	     is described by the link map fetched via got[1].  Otherwise we
	     have to scan all maps.  */
	  for (this = 0; this < nent; this++)
	    {
	      if (p[this].p_type == PT_LOAD)
		{
		  base = p[this].p_vaddr + l->l_addr;
		  limit = base + p[this].p_memsz;
		  if (stub_pc >= base && stub_pc < limit)
		    return l;
		}
	    }
	}
    }

    struct link_map *l;
    Lmid_t nsid;

    for (nsid = 0; nsid < DL_NNS; ++nsid)
      for (l = GL(dl_ns)[nsid]._ns_loaded; l != NULL; l = l->l_next)
	{
	  ElfW(Addr) base, limit;
	  const ElfW(Phdr) *p = l->l_phdr;
	  ElfW(Half) this, nent = l->l_phnum;

	  for (this = 0; this < nent; ++this)
	    {
	      if (p[this].p_type == PT_LOAD)
		{
		  base = p[this].p_vaddr + l->l_addr;
		  limit = base + p[this].p_memsz;
		  if (stub_pc >= base && stub_pc < limit)
		    return l;
		}
	    }
	}

  _dl_signal_error (0, NULL, NULL, "cannot find runtime link map");
  return NULL;
}

/* Define mips specific runtime resolver. The function __dl_runtime_resolve
   is called from assembler function _dl_runtime_resolve which converts
   special argument registers t7 ($15) and t8 ($24):
     t7  address to return to the caller of the function
     t8  index for this function symbol in .dynsym
   to usual c arguments.

   Other architectures call fixup from dl-runtime.c in
   _dl_runtime_resolve.  MIPS instead calls __dl_runtime_resolve.  We
   have to use our own version because of the way the got section is
   treated on MIPS (we've also got ELF_MACHINE_PLT defined).  */

/* The flag _dl_mips_gnu_objects is set if all dynamic objects are
   generated by the gnu linker. */
int _dl_mips_gnu_objects = 1;

/* This is called from assembly stubs below which the compiler can't see.  */
static ElfW(Addr)
__dl_runtime_resolve (ElfW(Word), ElfW(Word), ElfW(Addr), ElfW(Addr))
		  __attribute_used__;

static ElfW(Addr)
__dl_runtime_resolve (ElfW(Word) sym_index,
		      ElfW(Word) return_address,
		      ElfW(Addr) old_gpreg,
		      ElfW(Addr) stub_pc)
{
  struct link_map *l = elf_machine_runtime_link_map (old_gpreg, stub_pc);
  const ElfW(Sym)