sysdeps/riscv/dl-machine.h

/* Machine-dependent ELF dynamic relocation inline functions.  RISC-V version.
   Copyright (C) 2011-2021 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/>.  */

#ifndef dl_machine_h
#define dl_machine_h

#define ELF_MACHINE_NAME "RISC-V"

#include <entry.h>
#include <elf/elf.h>
#include <sys/asm.h>
#include <dl-tls.h>
#include <dl-irel.h>
#include <dl-static-tls.h>
#include <dl-machine-rel.h>

#ifndef _RTLD_PROLOGUE
# define _RTLD_PROLOGUE(entry)						\
	".globl\t" __STRING (entry) "\n\t"				\
	".type\t" __STRING (entry) ", @function\n"			\
	__STRING (entry) ":\n\t"
#endif

#ifndef _RTLD_EPILOGUE
# define _RTLD_EPILOGUE(entry)						\
	".size\t" __STRING (entry) ", . - " __STRING (entry) "\n\t"
#endif

#define ELF_MACHINE_JMP_SLOT R_RISCV_JUMP_SLOT

#define elf_machine_type_class(type)				\
  ((ELF_RTYPE_CLASS_PLT * ((type) == ELF_MACHINE_JMP_SLOT	\
     || (__WORDSIZE == 32 && (type) == R_RISCV_TLS_DTPREL32)	\
     || (__WORDSIZE == 32 && (type) == R_RISCV_TLS_DTPMOD32)	\
     || (__WORDSIZE == 32 && (type) == R_RISCV_TLS_TPREL32)	\
     || (__WORDSIZE == 64 && (type) == R_RISCV_TLS_DTPREL64)	\
     || (__WORDSIZE == 64 && (type) == R_RISCV_TLS_DTPMOD64)	\
     || (__WORDSIZE == 64 && (type) == R_RISCV_TLS_TPREL64)))	\
   | (ELF_RTYPE_CLASS_COPY * ((type) == R_RISCV_COPY)))

/* Return nonzero iff ELF header is compatible with the running host.  */
static inline int __attribute_used__
elf_machine_matches_host (const ElfW(Ehdr) *ehdr)
{
  /* We can only run RISC-V binaries.  */
  if (ehdr->e_machine != EM_RISCV)
    return 0;

  /* Ensure the library's floating-point ABI matches that of the running
     system.  For now we don't support mixing XLEN, so there's no need (or way)
     to check it matches.  */
#ifdef __riscv_float_abi_double
  if ((ehdr->e_flags & EF_RISCV_FLOAT_ABI) != EF_RISCV_FLOAT_ABI_DOUBLE)
    return 0;
#else
  if ((ehdr->e_flags & EF_RISCV_FLOAT_ABI) != EF_RISCV_FLOAT_ABI_SOFT)
    return 0;
#endif

  return 1;
}

/* Return the run-time load address of the shared object.  */
static inline ElfW(Addr)
elf_machine_load_address (void)
{
  extern const ElfW(Ehdr) __ehdr_start attribute_hidden;
  return (ElfW(Addr)) &__ehdr_start;
}

/* Return the link-time address of _DYNAMIC.  */
static inline ElfW(Addr)
elf_machine_dynamic (void)
{
  extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
  return (ElfW(Addr)) _DYNAMIC - elf_machine_load_address ();
}

#define STRINGXP(X) __STRING (X)
#define STRINGXV(X) STRINGV_ (X)
#define STRINGV_(...) # __VA_ARGS__

/* Initial entry point code for the dynamic linker.
   The C function `_dl_start' is the real entry point;
   its return value is the user program's entry point.  */

#define RTLD_START asm (\
	".text\n\
	" _RTLD_PROLOGUE (ENTRY_POINT) "\
	mv a0, sp\n\
	jal _dl_start\n\
	" _RTLD_PROLOGUE (_dl_start_user) "\
	# Stash user entry point in s0.\n\
	mv s0, a0\n\
	# See if we were run as a command with the executable file\n\
	# name as an extra leading argument.\n\
	lw a0, _dl_skip_args\n\
	# Load the original argument count.\n\
	" STRINGXP (REG_L) " a1, 0(sp)\n\
	# Subtract _dl_skip_args from it.\n\
	sub a1, a1, a0\n\
	# Adjust the stack pointer to skip _dl_skip_args words.\n\
	sll a0, a0, " STRINGXP (PTRLOG) "\n\
	add sp, sp, a0\n\
	# Save back the modified argument count.\n\
	" STRINGXP (REG_S) " a1, 0(sp)\n\
	# Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env) \n\
	" STRINGXP (REG_L) " a0, _rtld_local\n\
	add a2, sp, " STRINGXP (SZREG) "\n\
	sll a3, a1, " STRINGXP (PTRLOG) "\n\
	add a3, a3, a2\n\
	add a3, a3, " STRINGXP (SZREG) "\n\
	# Stash the stack pointer in s1.\n\
	mv s1, sp\n\
	# Align stack to 128 bits for the _dl_init call.\n\
	andi sp, sp,-16\n\
	# Call the function to run the initializers.\n\
	jal _dl_init\n\
	# Restore the stack pointer for _start.\n\
	mv sp, s1\n\
	# Pass our finalizer function to _start.\n\
	lla a0, _dl_fini\n\
	# Jump to the user entry point.\n\
	jr s0\n\
	" _RTLD_EPILOGUE (ENTRY_POINT) \
	  _RTLD_EPILOGUE (_dl_start_user) "\
	.previous" \
);

/* Names of the architecture-specific auditing callback functions.  */
#define ARCH_LA_PLTENTER riscv_gnu_pltenter
#define ARCH_LA_PLTEXIT riscv_gnu_pltexit

/* Bias .got.plt entry by the offset requested by the PLT header.  */
#define elf_machine_plt_value(map, reloc, value) (value)

static inline ElfW(Addr)
elf_machine_fixup_plt (struct link_map *map, lookup_t t,
		       const ElfW(Sym) *refsym, const ElfW(Sym) *sym,
		       const ElfW(Rela) *reloc,
		       ElfW(Addr) *reloc_addr, ElfW(Addr) value)
{
  return *reloc_addr = value;
}

#endif /* !dl_machine_h */

#ifdef RESOLVE_MAP

/* Perform a relocation described by R_INFO at the location pointed to
   by RELOC_ADDR.  SYM is the relocation symbol specified by R_INFO and
   MAP is the object containing the reloc.  */

static inline void
__attribute__ ((always_inline))
elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
		  const ElfW(Rela) *reloc, const ElfW(Sym) *sym,
		  const struct r_found_version *version,
		  void *const reloc_addr, int skip_ifunc)
{
  ElfW(Addr) r_info = reloc->r_info;
  const unsigned long int r_type = ELFW (R_TYPE) (r_info);
  ElfW(Addr) *addr_field = (ElfW(Addr) *) reloc_addr;
  const ElfW(Sym) *const __attribute__ ((unused)) refsym = sym;
  struct link_map *sym_map = RESOLVE_MAP (map, scope, &sym, version, r_type);
  ElfW(Addr) value = 0;
  if (sym_map != NULL)
    value = SYMBOL_ADDRESS (sym_map, sym, true) + reloc->r_addend;

  if (sym != NULL
      && __glibc_unlikely (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC)
      && __glibc_likely (sym->st_shndx != SHN_UNDEF)
      && __glibc_likely (!skip_ifunc))
    value = elf_ifunc_invoke (value);


  switch (r_type)
    {
#ifndef RTLD_BOOTSTRAP
    case __WORDSIZE == 64 ? R_RISCV_TLS_DTPMOD64 : R_RISCV_TLS_DTPMOD32:
      if (sym_map)
	*addr_field = sym_map->l_tls_modid;
      break;

    case __WORDSIZE == 64 ? R_RISCV_TLS_DTPREL64 : R_RISCV_TLS_DTPREL32:
      if (sym != NULL)
	*addr_field = TLS_DTPREL_VALUE (sym) + reloc->r_addend;
      break;

    case __WORDSIZE == 64 ? R_RISCV_TLS_TPREL64 : R_RISCV_TLS_TPREL32:
      if (sym != NULL)
	{
	  CHECK_STATIC_TLS (map, sym_map);
	  *addr_field = TLS_TPREL_VALUE (sym_map, sym) + reloc->r_addend;
	}
      break;

    case R_RISCV_COPY:
      {
	if (__glibc_unlikely (sym == NULL))
	  /* This can happen in trace mode if an object could not be
	     found.  */
	  break;

	/* Handle TLS copy relocations.  */
	if (__glibc_unlikely (ELFW (ST_TYPE) (sym->st_info) == STT_TLS))
	  {
	    /* There's nothing to do if the symbol is in .tbss.  */
	    if (__glibc_likely (sym->st_value >= sym_map->l_tls_initimage_size))
	      break;
	    value += (ElfW(Addr)) sym_map->l_tls_initimage - sym_map->l_addr;
	  }

	size_t size = sym->st_size;
	if (__glibc_unlikely (sym->st_size != refsym->st_size))
	  {
	    const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
	    if (sym->st_size > refsym->st_size)
	      size = refsym->st_size;
	    if (sym->st_size > refsym->st_size || GLRO(dl_verbose))
	      _dl_error_printf ("\
  %s: Symbol `%s' has different size in shared object, consider re-linking\n",
				rtld_progname ?: "<program name unknown>",
				strtab + refsym->st_name);
	  }

	memcpy (reloc_addr, (void *)value, size);
	break;
      }
#endif

#if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
    case R_RISCV_RELATIVE:
      {
# if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
	/* This is defined in rtld.c, but nowhere in the static libc.a;
	   make the reference weak so static programs can still link.
	   This declaration cannot be done when compiling rtld.c
	   (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
	   common defn for _dl_rtld_map, which is incompatible with a
	   weak decl in the same file.  */
#  ifndef SHARED
	weak_extern (GL(dl_rtld_map));
#  endif
	if (map != &GL(dl_rtld_map)) /* Already done in rtld itself.  */
# endif
	  *addr_field = map->l_addr + reloc->r_addend;
      break;
    }
#endif

    case R_RISCV_IRELATIVE:
      value = map->l_addr + reloc->r_addend;
      if (__glibc_likely (!skip_ifunc))
        value = elf_ifunc_invoke (value);
      *addr_field = value;
      break;

    case R_RISCV_JUMP_SLOT:
    case __WORDSIZE == 64 ? R_RISCV_64 : R_RISCV_32:
      *addr_field = value;
      break;

    case R_RISCV_NONE:
      break;

    default:
      _dl_reloc_bad_type (map, r_type, 0);
      break;
    }
}

static inline void
__attribute__ ((always_inline))
elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
			  void *const reloc_addr)
{
  *(ElfW(Addr) *) reloc_addr = l_addr + reloc->r_addend;
}

static inline void
__attribute__ ((always_inline))
elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
		      ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
		      int skip_ifunc)
{
  ElfW(Addr) *const reloc_addr = (void *) (l_addr + reloc->r_offset);
  const unsigned int r_type = ELFW (R_TYPE) (reloc->r_info);

  /* Check for unexpected PLT reloc type.  */
  if (__glibc_likely (r_type == R_RISCV_JUMP_SLOT))
    {
      if (__glibc_unlikely (map->l_mach.plt == 0))
	{
	  if (l_addr)
	    *reloc_addr += l_addr;
	}
      else
	*reloc_addr = map->l_mach.plt;
    }
  else if (__glibc_unlikely (r_type == R_RISCV_IRELATIVE))
    {
      ElfW(Addr) value = map->l_addr + reloc->r_addend;
      if (__glibc_likely (!skip_ifunc))
        value = elf_ifunc_invoke (value);
      *reloc_addr = value;
    }
  else
    _dl_reloc_bad_type (map, r_type, 1);
}

/* Set up the loaded object described by L so its stub function
   will jump to the on-demand fixup code __dl_runtime_resolve.  */

static inline int
__attribute__ ((always_inline))
elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
			   int lazy, int profile)
{
#ifndef RTLD_BOOTSTRAP
  /* If using PLTs, fill in the first two entries of .got.plt.  */
  if (l->l_info[DT_JMPREL])
    {
      extern void _dl_runtime_resolve (void) __attribute__ ((visibility ("hidden")));
      ElfW(Addr) *gotplt = (ElfW(Addr) *) D_PTR (l, l_info[DT_PLTGOT]);
      /* If a library is prelinked but we have to relocate anyway,
	 we have to be able to undo the prelinking of .got.plt.
	 The prelinker saved the address of .plt for us here.  */
      if (gotplt[1])
	l->l_mach.plt = gotplt[1] + l->l_addr;
      gotplt[0] = (ElfW(Addr)) &_dl_runtime_resolve;
      gotplt[1] = (ElfW(Addr)) l;
    }

  if (l->l_type == lt_executable)
    {
      /* The __global_pointer$ may not be defined by the linker if the
	 $gp register does not be used to access the global variable
	 in the executable program. Therefore, the search symbol is
	 set to a weak symbol to avoid we error out if the
	 __global_pointer$ is not found.  */
      ElfW(Sym) gp_sym = { 0 };
      gp_sym.st_info = (unsigned char) ELFW (ST_INFO (STB_WEAK, STT_NOTYPE));

      const ElfW(Sym) *ref = &gp_sym;
      _dl_lookup_symbol_x ("__global_pointer$", l, &ref,
			   l->l_scope, NULL, 0, 0, NULL);
      if (ref)
        asm (
          "mv gp, %0\n"
          :
          : "r" (ref->st_value)
        );
    }
#endif
  return lazy;
}

#endif /* RESOLVE_MAP */