Re: [PATCH v3 04/13] or1k: startup and dynamic linking code

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 10/12/2021 20:34, Stafford Horne via Libc-alpha wrote:
> Code for C runtime startup and dynamic loading including PLT layout.

Patch looks ok, although I comment much on ABI and assembly code. Some
comments below.

> ---
>  sysdeps/or1k/bits/link.h   |  51 ++++++
>  sysdeps/or1k/dl-machine.h  | 323 +++++++++++++++++++++++++++++++++++++
>  sysdeps/or1k/dl-start.S    |  98 +++++++++++
>  sysdeps/or1k/ldsodefs.h    |  40 +++++
>  sysdeps/or1k/sotruss-lib.c |  51 ++++++
>  sysdeps/or1k/start.S       |  99 ++++++++++++
>  sysdeps/or1k/tst-audit.h   |  24 +++
>  7 files changed, 686 insertions(+)
>  create mode 100644 sysdeps/or1k/bits/link.h
>  create mode 100644 sysdeps/or1k/dl-machine.h
>  create mode 100644 sysdeps/or1k/dl-start.S
>  create mode 100644 sysdeps/or1k/ldsodefs.h
>  create mode 100644 sysdeps/or1k/sotruss-lib.c
>  create mode 100644 sysdeps/or1k/start.S
>  create mode 100644 sysdeps/or1k/tst-audit.h
> 
> diff --git a/sysdeps/or1k/bits/link.h b/sysdeps/or1k/bits/link.h
> new file mode 100644
> index 0000000000..ad183c9625
> --- /dev/null
> +++ b/sysdeps/or1k/bits/link.h
> @@ -0,0 +1,51 @@
> +/* Declarations for dynamic linker interface. OpenRISC version.
> +   Copyright (C) 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 _LINK_H
> +# error "Never include <bits/link.h> directly; use <link.h> instead."
> +#endif
> +
> +/* Registers for entry into PLT.  */
> +typedef struct La_or1k_regs
> +{
> +  uint32_t lr_reg[31];
> +} La_or1k_regs;
> +

So is the intent is to provide caller all the register, no only the caller-saved 
registers?

> +/* Return values for calls from PLT.  */
> +typedef struct La_or1k_retval
> +{
> +  uint32_t lrv_r3;
> +} La_or1k_retval;
> +
> +__BEGIN_DECLS
> +
> +extern ElfW(Addr) la_or1k_gnu_pltenter (ElfW(Sym) *__sym, unsigned int __ndx,
> +					uintptr_t *__refcook,
> +					uintptr_t *__defcook,
> +					La_or1k_regs *__regs,
> +					unsigned int *__flags,
> +					const char *__symname,
> +					long int *__framesizep);
> +extern unsigned int la_or1k_gnu_pltexit (ElfW(Sym) *__sym, unsigned int __ndx,
> +					 uintptr_t *__refcook,
> +					 uintptr_t *__defcook,
> +					 const La_or1k_regs *__inregs,
> +					 La_or1k_retval *__outregs,
> +					 const char *__symname);
> +
> +__END_DECLS
> diff --git a/sysdeps/or1k/dl-machine.h b/sysdeps/or1k/dl-machine.h
> new file mode 100644
> index 0000000000..d41554769e
> --- /dev/null
> +++ b/sysdeps/or1k/dl-machine.h
> @@ -0,0 +1,323 @@
> +/* Machine-dependent ELF dynamic relocation inline functions.  OpenRISC version.
> +   Copyright (C) 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 "or1k"
> +
> +#include <sys/cdefs.h>
> +#include <sys/param.h>
> +#include <tls.h>
> +#include <dl-irel.h>
> +#include <dl-static-tls.h>
> +#include <dl-machine-rel.h>
> +
> +/* Return nonzero iff ELF header is compatible with the running host.  */
> +static inline int __attribute__ ((unused))
> +elf_machine_matches_host (const Elf32_Ehdr *ehdr)
> +{
> +  return ehdr->e_machine == EM_OPENRISC;
> +}
> +
> +static inline Elf32_Addr *
> +or1k_get_got (void)
> +{
> +  Elf32_Addr *got;
> +  register long int linkreg asm ("r9");

Is the 'r9' a required register by the ABI to use on this assembly snippet?
I am asking because local name 'registers' are only a hint to gcc, as we
found recently [1], if you really need 'r9' you will probably need to use 
a global name resgister.

> +  asm ("l.jal    0x8\n"
> +       " l.movhi %0, gotpchi(_GLOBAL_OFFSET_TABLE_-4)\n"
> +       "l.ori    %0, %0, gotpclo(_GLOBAL_OFFSET_TABLE_+0)\n"
> +       "l.add    %0, %0, %1\n"
> +       : "=r" (got), "=r" (linkreg));
> +
> +  return got;
> +}
> +
> +/* Return the link-time address of _DYNAMIC.  Conveniently, this is the
> +   first element of the GOT.  */
> +static inline Elf32_Addr
> +elf_machine_dynamic (void)
> +{
> +  Elf32_Addr *got = or1k_get_got();

Space before '('.

> +  return *got;
> +}
> +
> +
> +/* Return the run-time load address of the shared object.  */
> +static inline Elf32_Addr
> +elf_machine_load_address (void)
> +{
> +  /* Compute the difference between the runtime address of _DYNAMIC as seen
> +     by a GOTOFF reference, and the link-time address found in the special
> +     unrelocated first GOT entry.  */
> +  Elf32_Addr dyn;
> +  Elf32_Addr *got = or1k_get_got();

Space before '('.

> +
> +  asm ("l.movhi %0, gotoffhi(_DYNAMIC);"
> +       "l.ori   %0, %0, gotofflo(_DYNAMIC);"
> +       "l.add   %0, %0, %1;"
> +       : "=&r"(dyn) : "r"(got));
> +
> +  return dyn - *got;
> +}
> +
> +/* Initial entry point code for the dynamic linker.  The function _dl_start
> +   is the real entry point; it's return value is the user program's entry
> +   point.
> +
> +   Code is really located in dl-start.S, just tell the linker that it
> +   exists.  */
> +#define RTLD_START asm (".globl _dl_start");
> +
> +/* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry or
> +   TLS variable, so undefined references should not be allowed to
> +   define the value.
> +   ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
> +   of the main executable's symbols, as for a COPY reloc.  */
> +
> +#define elf_machine_type_class(type) \
> +  (((type) == R_OR1K_JMP_SLOT \
> +   || (type) == R_OR1K_TLS_DTPMOD \
> +   || (type) == R_OR1K_TLS_DTPOFF \
> +   || (type) == R_OR1K_TLS_TPOFF) * ELF_RTYPE_CLASS_PLT \
> +   | ((type) == R_OR1K_COPY) * ELF_RTYPE_CLASS_COPY)
> +
> +/* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
> +#define ELF_MACHINE_JMP_SLOT    R_OR1K_JMP_SLOT
> +
> +#define ARCH_LA_PLTENTER or1k_gnu_pltenter
> +#define ARCH_LA_PLTEXIT or1k_gnu_pltexit
> +
> +/* Set up the loaded object described by L so its unrelocated PLT
> +   entries will jump to the on-demand fixup code in dl-runtime.c.  */
> +static inline int __attribute__ ((unused, always_inline))
> +elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
> +			   int lazy, int profile)
> +{
> +  ElfW(Addr) *pltgot;
> +  extern void _dl_runtime_resolve (ElfW(Word));
> +  extern void _dl_runtime_profile (ElfW(Word));
> +
> +  if (l->l_info[DT_JMPREL] && lazy)
> +    {
> +      pltgot = (ElfW(Addr) *) D_PTR (l, l_info[DT_PLTGOT]);
> +
> +      /* Fill in initial entrys of the plt */
> +
> +      /* Register the link_map address in the plt at pltgot[1].
> +	 This will also be used in the resolver for accessing the
> +	 link_map structure.  */
> +      pltgot[1] = (ElfW(Addr)) l;
> +
> +      /* The pltgot[2] entry contains the address of a function which gets
> +	 called to get the address of a so far unresolved function and
> +	 jump to it.  The profiling extension of the dynamic linker allows
> +	 to intercept the calls to collect information.  In this case we
> +	 don't store the address in the GOT so that all future calls also
> +	 end in this function.  */
> +#if 0 /* Profiling not supported in OpenRISC yet (need to implement
> +	 _dl_runtime_profile).  */
> +      if ( profile)
> +	{
> +	   pltgot[2] = (ElfW(Addr)) &_dl_runtime_profile;
> +
> +	  if (GLRO(dl_profile) != NULL
> +	      && _dl_name_match_p (GLRO(dl_profile), l))
> +	    /* Say that we really want profiling and the timers are
> +	       started.  */
> +	    GL(dl_profile_map) = l;
> +	}
> +      else
> +#endif

I think it would be better to remove the commented code and add a comment stating
LD_PROFILE is not currently supported.

> +	{
> +	  /* This function will get called to fix up the GOT entry
> +	     indicated by the offset on the stack, and then jump to
> +	     the resolved address.  */
> +	  pltgot[2] = (ElfW(Addr)) &_dl_runtime_resolve;
> +	}
> +
> +    }
> +
> +  return lazy;
> +}
> +
> +/* Mask identifying addresses reserved for the user program,
> +   where the dynamic linker should not map anything.  */
> +#define ELF_MACHINE_USER_ADDRESS_MASK   0xf8000000UL
> +
> +/* We define an initialization functions.  This is called very early in
> +   _dl_sysdep_start.  */
> +#define DL_PLATFORM_INIT dl_platform_init ()
> +
> +static inline void __attribute__ ((unused))
> +dl_platform_init (void)
> +{
> +  if (GLRO(dl_platform) != NULL && *GLRO(dl_platform) == '\0')
> +    /* Avoid an empty string which would disturb us.  */
> +    GLRO(dl_platform) = NULL;
> +}
> +
> +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;
> +}
> +
> +/* Return the final value of a plt relocation.  */
> +static inline Elf32_Addr
> +elf_machine_plt_value (struct link_map *map, const Elf32_Rela *reloc,
> +		       Elf32_Addr value)
> +{
> +  return value + reloc->r_addend;
> +}
> +
> +
> +#endif /* !dl_machine_h */
> +
> +#ifdef RESOLVE_MAP
> +
> +/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
> +   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_arg, int skip_ifunc)
> +{
> +  Elf32_Addr *const reloc_addr = reloc_addr_arg;
> +  const unsigned int r_type = ELF32_R_TYPE (reloc->r_info);
> +
> +  if (__glibc_unlikely (r_type == R_OR1K_NONE))
> +    return;
> +  else
> +    {
> +# ifndef RESOLVE_CONFLICT_FIND_MAP
> +      const Elf32_Sym *const refsym = sym;
> +# endif
> +      struct link_map *sym_map = RESOLVE_MAP (map, scope, &sym, version,
> +					      r_type);
> +      Elf32_Addr value = SYMBOL_ADDRESS (sym_map, sym, true);
> +
> +      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 RESOLVE_CONFLICT_FIND_MAP
> +	  case R_OR1K_COPY:
> +	    if (sym == NULL)
> +	      /* This can happen in trace mode if an object could not be
> +		 found.  */
> +	      break;
> +	    if (__glibc_unlikely (sym->st_size > refsym->st_size)
> +		|| (__glibc_unlikely (sym->st_size < refsym->st_size)
> +		  && GLRO(dl_verbose)))
> +	    {
> +	      const char *strtab;
> +
> +	      strtab = (const char *) D_PTR (map, l_info[DT_STRTAB]);
> +	      _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_arg, (void *) value,
> +		MIN (sym->st_size, refsym->st_size));
> +	    break;
> +# endif /* !RESOLVE_CONFLICT_FIND_MAP */
> +	  case R_OR1K_32:
> +	    /* Support relocations on mis-aligned offsets.  */
> +	    value += reloc->r_addend;
> +	    memcpy (reloc_addr_arg, &value, 4);
> +	    break;
> +	  case R_OR1K_GLOB_DAT:
> +	  case R_OR1K_JMP_SLOT:
> +	    *reloc_addr = value + reloc->r_addend;
> +	    break;
> +	  case R_OR1K_TLS_DTPMOD:
> +# ifdef RTLD_BOOTSTRAP
> +	    /* During startup the dynamic linker is always the module
> +	       with index 1.  */
> +	    *reloc_addr = 1;
> +# else
> +	    if (sym_map != NULL)
> +	      *reloc_addr = sym_map->l_tls_modid;
> +# endif
> +	    break;
> +	  case R_OR1K_TLS_DTPOFF:
> +# ifndef RTLD_BOOTSTRAP
> +	    *reloc_addr = (sym == NULL ? 0 : sym->st_value) + reloc->r_addend;
> +# endif
> +	    break;
> +
> +	  case R_OR1K_TLS_TPOFF:
> +# ifdef RTLD_BOOTSTRAP
> +	    *reloc_addr = sym->st_value + reloc->r_addend +
> +	      map->l_tls_offset - TLS_TCB_SIZE;
> +# else
> +	    if (sym_map != NULL)
> +	      {
> +		CHECK_STATIC_TLS (map, sym_map);
> +		*reloc_addr = sym->st_value + reloc->r_addend +
> +		  sym_map->l_tls_offset - TLS_TCB_SIZE;
> +	      }
> +# endif
> +	    break;
> +	  default:
> +	    _dl_reloc_bad_type (map, r_type, 0);
> +	    break;
> +	}
> +    }
> +}
> +
> +static inline void
> +__attribute__ ((always_inline))
> +elf_machine_rela_relative (Elf32_Addr l_addr, const Elf32_Rela *reloc,
> +			   void *const reloc_addr_arg)
> +{
> +  Elf32_Addr *const reloc_addr = reloc_addr_arg;
> +  *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)
> +{
> +  Elf32_Addr *const reloc_addr = (void *) (l_addr + reloc->r_offset);
> +  const unsigned int r_type = ELF32_R_TYPE (reloc->r_info);
> +
> +  if (__glibc_likely (r_type == R_OR1K_JMP_SLOT))
> +      *reloc_addr += l_addr;
> +  else if (__glibc_unlikely (r_type == R_OR1K_NONE))
> +    return;
> +  else
> +    _dl_reloc_bad_type (map, r_type, 1);
> +}
> +
> +#endif /* RESOLVE_MAP */
> diff --git a/sysdeps/or1k/dl-start.S b/sysdeps/or1k/dl-start.S
> new file mode 100644
> index 0000000000..ecb1505427
> --- /dev/null
> +++ b/sysdeps/or1k/dl-start.S
> @@ -0,0 +1,98 @@
> +/* Machine-dependent ELF startup code.  OpenRISC version.
> +   Copyright (C) 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/>.  */
> +
> +#include <sysdep.h>
> +
> +/* Initial entry point code for the dynamic linker.
> +   The function _dl_start is the real entry point;
> +   it's return value is the user program's entry point.  */
> +ENTRY (_start)
> +	/* Count arguments in r11 */
> +	l.ori	r3, r1, 0
> +	l.movhi	r11, 0
> +1:
> +	l.addi	r3, r3, 4
> +	l.lwz	r12, 0(r3)
> +	l.sfnei	r12, 0
> +	l.addi	r11, r11, 1
> +	l.bf	1b
> +	 l.nop
> +	l.addi	r11, r11, -1
> +	/* store argument counter to stack.  */
> +	l.sw	0(r1), r11
> +
> +	/* Load the PIC register.  */
> +	l.jal	0x8
> +	 l.movhi r16, gotpchi(_GLOBAL_OFFSET_TABLE_-4)
> +	l.ori	r16, r16, gotpclo(_GLOBAL_OFFSET_TABLE_+0)
> +	l.add	r16, r16, r9
> +
> +	l.ori	r3, r1, 0
> +
> +	l.jal	_dl_start
> +	 l.nop
> +	/* Save user entry in a call saved reg.  */
> +	l.ori	r22, r11, 0
> +	/* Fall through to _dl_start_user.  */
> +
> +_dl_start_user:
> +	/* Set up for _dl_init.  */
> +
> +	/* Load _rtld_local (a.k.a _dl_loaded).  */
> +	l.lwz	r12, got(_rtld_local)(r16)
> +	l.lwz	r3, 0(r12)
> +
> +	/* Load argc */
> +	l.lwz	r18, got(_dl_argc)(r16)
> +	l.lwz	r4, 0(r18)
> +
> +	/* Load argv */
> +	l.lwz	r20, got(_dl_argv)(r16)
> +	l.lwz	r5, 0(r20)
> +
> +	/* Load envp = &argv[argc + 1].  */
> +	l.slli	r6, r4, 2
> +	l.addi	r6, r6, 4
> +	l.add	r6, r6, r5
> +
> +	l.jal	plt(_dl_init)
> +	 l.nop
> +
> +	/* Now set up for user entry.
> +	   The already defined ABI loads argc and argv from the stack.
> +
> +	   argc = 0(r1)
> +	   argv = r1 + 4
> +	*/
> +
> +	/* Load SP as argv - 4.  */
> +	l.lwz	r3, 0(r20)
> +	l.addi	r1, r3, -4
> +
> +	/* Save argc.  */
> +	l.lwz	r3, 0(r18)
> +	l.sw	0(r1), r3
> +
> +	/* Pass _dl_fini function address to _start.
> +	   Next start.S will then pass this as rtld_fini to __libc_start_main.  */
> +	l.lwz	r3, got(_dl_fini)(r16)
> +
> +	l.jr	r22
> +	 l.nop
> +
> +END (_start)
> diff --git a/sysdeps/or1k/ldsodefs.h b/sysdeps/or1k/ldsodefs.h
> new file mode 100644
> index 0000000000..89713fcc70
> --- /dev/null
> +++ b/sysdeps/or1k/ldsodefs.h
> @@ -0,0 +1,40 @@
> +/* Run-time dynamic linker data structures for loaded ELF shared objects.
> +   Copyright (C) 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	_OR1K_LDSODEFS_H
> +#define	_OR1K_LDSODEFS_H	1
> +
> +#include <elf.h>
> +
> +struct La_or1k_regs;
> +struct La_or1k_retval;
> +
> +#define ARCH_PLTENTER_MEMBERS						\
> +    uintptr_t (*or1k_gnu_pltenter) (Elf32_Sym *, unsigned int, uintptr_t *, \
> +				  uintptr_t *, struct La_or1k_regs *, \
> +				  unsigned int *, const char *name,	\
> +				  long int *framesizep)
> +
> +#define ARCH_PLTEXIT_MEMBERS						\
> +    unsigned int (*or1k_gnu_pltexit) (Elf32_Sym *, unsigned int, uintptr_t *, \
> +				    uintptr_t *, const struct La_or1k_regs *, \
> +				    struct La_or1k_retval *, const char *)
> +
> +#include_next <ldsodefs.h>
> +
> +#endif
> diff --git a/sysdeps/or1k/sotruss-lib.c b/sysdeps/or1k/sotruss-lib.c
> new file mode 100644
> index 0000000000..ee16f84456
> --- /dev/null
> +++ b/sysdeps/or1k/sotruss-lib.c
> @@ -0,0 +1,51 @@
> +/* Override generic sotruss-lib.c to define actual functions for OpenRISC.
> +   Copyright (C) 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/>.  */
> +
> +#define HAVE_ARCH_PLTENTER
> +#define HAVE_ARCH_PLTEXIT
> +
> +#include <elf/sotruss-lib.c>
> +
> +ElfW(Addr)
> +la_or1k_gnu_pltenter (ElfW(Sym) *sym __attribute__ ((unused)),
> +		       unsigned int ndx __attribute__ ((unused)),
> +		       uintptr_t *refcook, uintptr_t *defcook,
> +		       La_or1k_regs *regs, unsigned int *flags,
> +		       const char *symname, long int *framesizep)
> +{
> +  print_enter (refcook, defcook, symname,
> +	       regs->lr_reg[0], regs->lr_reg[1], regs->lr_reg[2],
> +	       *flags);
> +
> +  /* No need to copy anything, we will not need the parameters in any case.  */
> +  *framesizep = 0;
> +
> +  return sym->st_value;
> +}
> +
> +unsigned int
> +la_or1k_gnu_pltexit (ElfW(Sym) *sym, unsigned int ndx, uintptr_t *refcook,
> +		      uintptr_t *defcook,
> +		      const struct La_or1k_regs *inregs,
> +		      struct La_or1k_retval *outregs,
> +		      const char *symname)
> +{
> +  print_exit (refcook, defcook, symname, outregs->lrv_r3);
> +
> +  return 0;
> +}
> diff --git a/sysdeps/or1k/start.S b/sysdeps/or1k/start.S
> new file mode 100644
> index 0000000000..0424355f36
> --- /dev/null
> +++ b/sysdeps/or1k/start.S
> @@ -0,0 +1,99 @@
> +/* start, OpenRISC version.
> +   Copyright (C) 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, write to the Free
> +   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
> +   02111-1307 USA.  */
> +
> +/* This is the canonical entry point, usually the first thing in the text
> +   segment.
> +
> +   sp   The stack contains the arguments and environment:
> +    0(sp)     argc
> +    4(sp)     argv[0]
> +    ...
> +    (4*argc)(sp)    NULL
> +    (4*(argc+1))(sp)  envp[0]
> +    ...
> +    NULL
> + */
> +
> +#define __ASSEMBLY__
> +#include <sysdep.h>
> +#include <entry.h>
> +
> +ENTRY (ENTRY_POINT)
> +
> +	/* Setup Arguments to the __libc_start_main function.  */
> +
> +	/* Take values for argc and argv off the stack.
> +	   These will be passed as arguments two and three to main
> +	   and thus go in registers r4 and r5, respectively.  */
> +	l.lwz	r4, 0(r1)
> +	l.addi	r5, r1, 4
> +
> +	/* Pass in rtld_fini from dl-start.S.  */
> +	l.or	r8, r3, r3
> +
> +#ifdef PIC
> +	/* Obtain a pointer to .got in r16 */
> +	l.jal	0x8
> +	 l.movhi r16, gotpchi(_GLOBAL_OFFSET_TABLE_-4)
> +	l.ori	r16, r16, gotpclo(_GLOBAL_OFFSET_TABLE_+0)
> +	l.add	r16, r16, r9
> +
> +	/* Pass in the the main symbol.  */
> +	l.lwz	r3, got(main)(r16)
> +#else
> +	/* Pass in the the main symbol.  */
> +	l.movhi r3, hi(main)
> +	l.ori	r3, r3, lo(main)
> +#endif
> +	/* Used to be init and fini.  */
> +	l.movhi	r6, 0x0
> +	l.movhi	r7, 0x0
> +
> +	/* Push stack limit onto the stack.
> +	   This provides the highest stack address to user code (as stack grows
> +	   downwards.
> +	   This is the seventh argument to __libc_start_main and thus needs to
> +	   be passed on the stack.  */
> +	l.sw	-4(r1), r1
> +
> +	/* Adjust stack to account for a total of 7 args (i.e. the last one is
> +	   on the stack.  */
> +	l.addi	r1, r1, -4
> +
> +	/* Clear the frame pointer and link register since this is the
> +	   outermost frame.  */
> +	l.movhi	r2, 0x0
> +	l.movhi	r9, 0x0
> +
> +	/* Let the libc call main and exit with its return code.  */
> +#ifdef PIC
> +	l.j	plt(__libc_start_main)
> +#else
> +	l.j	__libc_start_main
> +#endif
> +	 l.nop
> +END (ENTRY_POINT)
> +
> +	/* Define a symbol for the first piece of initialized data.  */
> +	.data
> +	.globl __data_start
> +__data_start:
> +	.long 0
> +	.weak data_start
> +	data_start = __data_start
> diff --git a/sysdeps/or1k/tst-audit.h b/sysdeps/or1k/tst-audit.h
> new file mode 100644
> index 0000000000..79ee1b7b02
> --- /dev/null
> +++ b/sysdeps/or1k/tst-audit.h
> @@ -0,0 +1,24 @@
> +/* Definitions for testing PLT entry/exit auditing.  OpenRISC version.
> +   Copyright (C) 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/>.  */
> +
> +#define pltenter la_or1k_gnu_pltenter
> +#define pltexit la_or1k_gnu_pltexit
> +#define La_regs La_or1k_regs
> +#define La_retval La_or1k_retval
> +#define int_retval lrv_r3

[1] https://sourceware.org/pipermail/libc-alpha/2021-December/134176.html