Re: [PATCH v4] ld.so: Replace DL_RO_DYN_SECTION with dl_relocate_ld

["H.J. Lu" <hjl.tools@gmail.com>]

On Sun, Sep 19, 2021 at 8:28 PM Siddhesh Poyarekar
<siddhesh@sourceware.org> wrote:
>
> On 9/19/21 21:58, H.J. Lu wrote:
> > Changes in v4:
> >
> > 1. Change l_ld_readonly to bitfield.
> >
> > Changes in v3:
> >
> > 1. Remove DL_RO_DYN_TEMP_CNT.
> > 2. Update comments for dl_relocate_ld.
> >
> > Changes in v2:
> >
> > 1. Replace DL_RO_DYN_SECTION with dl_relocate_ld so that MIPS and RISC-V
> > won't relocate dynamic section even if it is writable.
> > 2. Add a run-time testcase.
> >
> > We can't relocate entries in dynamic section if it is readonly:
> >
> > 1. Add a l_ld_readonly field to struct link_map to indicate if dynamic
> > section is readonly and set it based on p_flags of PT_DYNAMIC segment.
> > 2. Replace DL_RO_DYN_SECTION with dl_relocate_ld to decide if dynamic
> > section should be relocated.
> > 3. Remove DL_RO_DYN_TEMP_CNT.
> > 4. Don't use a static dynamic section to make readonly dynamic section
> > in vDSO writable.
> > 5. Remove the temp argument from elf_get_dynamic_info.
>
> LGTM, thanks for doing this.  AFAICT you've addressed their concerns but
> please check with Florian and Carlos before committing.

Carlos, do you have any comments?

>
> Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
>
> > ---
> >   elf/Makefile                     | 11 +++++++++--
> >   elf/dl-load.c                    |  3 ++-
> >   elf/dl-reloc-static-pie.c        | 12 +++++++++++-
> >   elf/get-dynamic-info.h           | 21 +++------------------
> >   elf/rtld.c                       |  6 ++++--
> >   elf/setup-vdso.h                 |  5 ++---
> >   elf/tst-ro-dynamic-mod.c         | 19 +++++++++++++++++++
> >   elf/tst-ro-dynamic-mod.map       | 16 ++++++++++++++++
> >   elf/tst-ro-dynamic.c             | 31 +++++++++++++++++++++++++++++++
> >   include/link.h                   |  3 +++
> >   sysdeps/generic/dl-relocate-ld.h | 32 ++++++++++++++++++++++++++++++++
> >   sysdeps/generic/ldsodefs.h       |  7 ++-----
> >   sysdeps/mips/dl-relocate-ld.h    | 32 ++++++++++++++++++++++++++++++++
> >   sysdeps/mips/ldsodefs.h          |  4 ----
> >   sysdeps/riscv/dl-relocate-ld.h   | 32 ++++++++++++++++++++++++++++++++
> >   sysdeps/riscv/ldsodefs.h         |  5 -----
> >   16 files changed, 198 insertions(+), 41 deletions(-)
> >   create mode 100644 elf/tst-ro-dynamic-mod.c
> >   create mode 100644 elf/tst-ro-dynamic-mod.map
> >   create mode 100644 elf/tst-ro-dynamic.c
> >   create mode 100644 sysdeps/generic/dl-relocate-ld.h
> >   create mode 100644 sysdeps/mips/dl-relocate-ld.h
> >   create mode 100644 sysdeps/riscv/dl-relocate-ld.h
> >
> > diff --git a/elf/Makefile b/elf/Makefile
> > index 9f3fadc37e..eeb47145fc 100644
> > --- a/elf/Makefile
> > +++ b/elf/Makefile
> > @@ -223,7 +223,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
> >        tst-tls-ie tst-tls-ie-dlmopen argv0test \
> >        tst-glibc-hwcaps tst-glibc-hwcaps-prepend tst-glibc-hwcaps-mask \
> >        tst-tls20 tst-tls21 tst-dlmopen-dlerror tst-dlmopen-gethostbyname \
> > -      tst-dl-is_dso
> > +      tst-dl-is_dso tst-ro-dynamic
> >   #    reldep9
> >   tests-internal += loadtest unload unload2 circleload1 \
> >        neededtest neededtest2 neededtest3 neededtest4 \
> > @@ -359,7 +359,7 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
> >               libmarkermod4-1 libmarkermod4-2 libmarkermod4-3 libmarkermod4-4 \
> >               tst-tls20mod-bad tst-tls21mod tst-dlmopen-dlerror-mod \
> >               tst-auxvalmod \
> > -             tst-dlmopen-gethostbyname-mod \
> > +             tst-dlmopen-gethostbyname-mod tst-ro-dynamic-mod \
> >
> >   # Most modules build with _ISOMAC defined, but those filtered out
> >   # depend on internal headers.
> > @@ -1908,3 +1908,10 @@ $(objpfx)tst-getauxval-static.out: $(objpfx)tst-auxvalmod.so
> >   tst-getauxval-static-ENV = LD_LIBRARY_PATH=$(objpfx):$(common-objpfx)
> >
> >   $(objpfx)tst-dlmopen-gethostbyname.out: $(objpfx)tst-dlmopen-gethostbyname-mod.so
> > +
> > +$(objpfx)tst-ro-dynamic: $(objpfx)tst-ro-dynamic-mod.so
> > +$(objpfx)tst-ro-dynamic-mod.so: $(objpfx)tst-ro-dynamic-mod.os \
> > +  tst-ro-dynamic-mod.map
> > +     $(LINK.o) -nostdlib -nostartfiles -shared -o $@ \
> > +             -Wl,--script=tst-ro-dynamic-mod.map \
> > +             $(objpfx)tst-ro-dynamic-mod.os
>
> Adding new test and options.  OK.
>
> > diff --git a/elf/dl-load.c b/elf/dl-load.c
> > index 650e4edc35..4445c28ef3 100644
> > --- a/elf/dl-load.c
> > +++ b/elf/dl-load.c
> > @@ -1149,6 +1149,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
> >                such a segment to avoid a crash later.  */
> >             l->l_ld = (void *) ph->p_vaddr;
> >             l->l_ldnum = ph->p_memsz / sizeof (ElfW(Dyn));
> > +           l->l_ld_readonly = (ph->p_flags & PF_W) == 0;
>
> Mark read-only for DSOs.  OK.
>
> >           }
> >         break;
> >
> > @@ -1292,7 +1293,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
> >     else
> >       l->l_ld = (ElfW(Dyn) *) ((ElfW(Addr)) l->l_ld + l->l_addr);
> >
> > -  elf_get_dynamic_info (l, NULL);
> > +  elf_get_dynamic_info (l);
> >
> >     /* Make sure we are not dlopen'ing an object that has the
> >        DF_1_NOOPEN flag set, or a PIE object.  */
> > diff --git a/elf/dl-reloc-static-pie.c b/elf/dl-reloc-static-pie.c
> > index d5bd2f31e9..2fb02d7276 100644
> > --- a/elf/dl-reloc-static-pie.c
> > +++ b/elf/dl-reloc-static-pie.c
> > @@ -40,7 +40,17 @@ _dl_relocate_static_pie (void)
> >
> >     /* Read our own dynamic section and fill in the info array.  */
> >     main_map->l_ld = ((void *) main_map->l_addr + elf_machine_dynamic ());
> > -  elf_get_dynamic_info (main_map, NULL);
> > +
> > +  const ElfW(Phdr) *ph, *phdr = GL(dl_phdr);
> > +  size_t phnum = GL(dl_phnum);
> > +  for (ph = phdr; ph < &phdr[phnum]; ++ph)
> > +    if (ph->p_type == PT_DYNAMIC)
> > +      {
> > +     main_map->l_ld_readonly = (ph->p_flags & PF_W) == 0;
> > +     break;
> > +      }
> > +
> > +  elf_get_dynamic_info (main_map);
>
> Mark read-only for static-pie.  OK.
>
> >
> >   # ifdef ELF_MACHINE_BEFORE_RTLD_RELOC
> >     ELF_MACHINE_BEFORE_RTLD_RELOC (main_map->l_info);
> > diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
> > index d8ec32377d..4aa2058abf 100644
> > --- a/elf/get-dynamic-info.h
> > +++ b/elf/get-dynamic-info.h
> > @@ -28,7 +28,7 @@ static
> >   auto
> >   #endif
> >   inline void __attribute__ ((unused, always_inline))
> > -elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
> > +elf_get_dynamic_info (struct link_map *l)
> >   {
> >   #if __ELF_NATIVE_CLASS == 32
> >     typedef Elf32_Word d_tag_utype;
> > @@ -69,28 +69,15 @@ elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
> >         info[i] = dyn;
> >       }
> >
> > -#define DL_RO_DYN_TEMP_CNT   8
> > -
> > -#ifndef DL_RO_DYN_SECTION
> >     /* Don't adjust .dynamic unnecessarily.  */
> > -  if (l->l_addr != 0)
> > +  if (l->l_addr != 0 && dl_relocate_ld (l))
> >       {
> >         ElfW(Addr) l_addr = l->l_addr;
> > -      int cnt = 0;
> >
> >   # define ADJUST_DYN_INFO(tag) \
> >         do                                                                  \
> >       if (info[tag] != NULL)                                                \
> > -       {                                                                   \
> > -         if (temp)                                                         \
> > -           {                                                               \
> > -             temp[cnt].d_tag = info[tag]->d_tag;                           \
> > -             temp[cnt].d_un.d_ptr = info[tag]->d_un.d_ptr + l_addr;        \
> > -             info[tag] = temp + cnt++;                                     \
> > -           }                                                               \
> > -         else                                                              \
> > -           info[tag]->d_un.d_ptr += l_addr;                                \
> > -       }                                                                   \
> > +         info[tag]->d_un.d_ptr += l_addr;                                  \
>
> Simplify by using the readonly flag.  OK.
>
> >         while (0)
> >
> >         ADJUST_DYN_INFO (DT_HASH);
> > @@ -107,9 +94,7 @@ elf_get_dynamic_info (struct link_map *l, ElfW(Dyn) *temp)
> >         ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
> >         ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
> >   # undef ADJUST_DYN_INFO
> > -      assert (cnt <= DL_RO_DYN_TEMP_CNT);
> >       }
> > -#endif
> >     if (info[DT_PLTREL] != NULL)
> >       {
> >   #if ELF_MACHINE_NO_RELA
> > diff --git a/elf/rtld.c b/elf/rtld.c
> > index 878e6480f4..88a78326c8 100644
> > --- a/elf/rtld.c
> > +++ b/elf/rtld.c
> > @@ -463,6 +463,7 @@ _dl_start_final (void *arg, struct dl_start_final_info *info)
> >   #ifndef DONT_USE_BOOTSTRAP_MAP
> >     GL(dl_rtld_map).l_addr = info->l.l_addr;
> >     GL(dl_rtld_map).l_ld = info->l.l_ld;
> > +  GL(dl_rtld_map).l_ld_readonly = info->l.l_ld_readonly;
> >     memcpy (GL(dl_rtld_map).l_info, info->l.l_info,
> >         sizeof GL(dl_rtld_map).l_info);
> >     GL(dl_rtld_map).l_mach = info->l.l_mach;
> > @@ -546,7 +547,7 @@ _dl_start (void *arg)
> >
> >     /* Read our own dynamic section and fill in the info array.  */
> >     bootstrap_map.l_ld = (void *) bootstrap_map.l_addr + elf_machine_dynamic ();
> > -  elf_get_dynamic_info (&bootstrap_map, NULL);
> > +  elf_get_dynamic_info (&bootstrap_map);
> >
> >   #if NO_TLS_OFFSET != 0
> >     bootstrap_map.l_tls_offset = NO_TLS_OFFSET;
> > @@ -1468,6 +1469,7 @@ dl_main (const ElfW(Phdr) *phdr,
> >       /* This tells us where to find the dynamic section,
> >          which tells us everything we need to do.  */
> >       main_map->l_ld = (void *) main_map->l_addr + ph->p_vaddr;
> > +     main_map->l_ld_readonly = (ph->p_flags & PF_W) == 0;
> >       break;
> >         case PT_INTERP:
> >       /* This "interpreter segment" was used by the program loader to
> > @@ -1613,7 +1615,7 @@ dl_main (const ElfW(Phdr) *phdr,
> >     if (! rtld_is_main)
> >       {
> >         /* Extract the contents of the dynamic section for easy access.  */
> > -      elf_get_dynamic_info (main_map, NULL);
> > +      elf_get_dynamic_info (main_map);
>
> Mark read-only for main executable.  OK.
>
> >
> >         /* If the main map is libc.so, update the base namespace to
> >        refer to this map.  If libc.so is loaded later, this happens
> > diff --git a/elf/setup-vdso.h b/elf/setup-vdso.h
> > index 86c491e49c..f44748bc98 100644
> > --- a/elf/setup-vdso.h
> > +++ b/elf/setup-vdso.h
> > @@ -33,8 +33,6 @@ setup_vdso (struct link_map *main_map __attribute__ ((unused)),
> >                                      0, LM_ID_BASE);
> >     if (__glibc_likely (l != NULL))
> >       {
> > -      static ElfW(Dyn) dyn_temp[DL_RO_DYN_TEMP_CNT] attribute_relro;
> > -
> >         l->l_phdr = ((const void *) GLRO(dl_sysinfo_dso)
> >                  + GLRO(dl_sysinfo_dso)->e_phoff);
> >         l->l_phnum = GLRO(dl_sysinfo_dso)->e_phnum;
> > @@ -45,6 +43,7 @@ setup_vdso (struct link_map *main_map __attribute__ ((unused)),
> >           {
> >             l->l_ld = (void *) ph->p_vaddr;
> >             l->l_ldnum = ph->p_memsz / sizeof (ElfW(Dyn));
> > +           l->l_ld_readonly = (ph->p_flags & PF_W) == 0;
>
> Mark read-only for vdso.  OK.
>
> >           }
> >         else if (ph->p_type == PT_LOAD)
> >           {
> > @@ -65,7 +64,7 @@ setup_vdso (struct link_map *main_map __attribute__ ((unused)),
> >         l->l_map_end += l->l_addr;
> >         l->l_text_end += l->l_addr;
> >         l->l_ld = (void *) ((ElfW(Addr)) l->l_ld + l->l_addr);
> > -      elf_get_dynamic_info (l, dyn_temp);
> > +      elf_get_dynamic_info (l);
> >         _dl_setup_hash (l);
> >         l->l_relocated = 1;
> >
> > diff --git a/elf/tst-ro-dynamic-mod.c b/elf/tst-ro-dynamic-mod.c
> > new file mode 100644
> > index 0000000000..6d99925964
> > --- /dev/null
> > +++ b/elf/tst-ro-dynamic-mod.c
> > @@ -0,0 +1,19 @@
> > +/* Test case for DSO with readonly dynamic section.
> > +   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/>.  */
> > +
> > +int foo = -1;
> > diff --git a/elf/tst-ro-dynamic-mod.map b/elf/tst-ro-dynamic-mod.map
> > new file mode 100644
> > index 0000000000..2fe4a2998c
> > --- /dev/null
> > +++ b/elf/tst-ro-dynamic-mod.map
> > @@ -0,0 +1,16 @@
> > +SECTIONS
> > +{
> > + . = SIZEOF_HEADERS;
> > + .dynamic : { *(.dynamic) } :text :dynamic
> > + .rodata : { *(.data*) *(.bss*) } :text
> > + /DISCARD/ : {
> > +  *(.note.gnu.property)
> > + }
> > + .note : { *(.note.*) } :text :note
> > +}
> > +PHDRS
> > +{
> > + text PT_LOAD FLAGS(5) FILEHDR PHDRS;
> > + dynamic PT_DYNAMIC FLAGS(4);
> > + note PT_NOTE FLAGS(4);
> > +}
> > diff --git a/elf/tst-ro-dynamic.c b/elf/tst-ro-dynamic.c
> > new file mode 100644
> > index 0000000000..3a18f8789a
> > --- /dev/null
> > +++ b/elf/tst-ro-dynamic.c
> > @@ -0,0 +1,31 @@
> > +/* Test case for DSO with readonly dynamic section.
> > +   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 <support/check.h>
> > +#include <support/test-driver.h>
> > +
> > +extern int foo;
> > +
> > +static int
> > +do_test (void)
> > +{
> > +  TEST_COMPARE (foo, -1);
> > +  return 0;
> > +}
> > +
> > +#include <support/test-driver.c>
>
> New test.  OK.
>
> > diff --git a/include/link.h b/include/link.h
> > index 4af16cb596..c46aced9f7 100644
> > --- a/include/link.h
> > +++ b/include/link.h
> > @@ -205,6 +205,7 @@ struct link_map
> >       unsigned int l_free_initfini:1; /* Nonzero if l_initfini can be
> >                                      freed, ie. not allocated with
> >                                      the dummy malloc in ld.so.  */
> > +    unsigned int l_ld_readonly:1; /* Nonzero if dynamic section is readonly.  */
>
> Flag bit.  OK.
>
> >
> >       /* NODELETE status of the map.  Only valid for maps of type
> >          lt_loaded.  Lazy binding sets l_nodelete_active directly,
> > @@ -342,6 +343,8 @@ struct link_map
> >       unsigned long long int l_serial;
> >     };
> >
> > +#include <dl-relocate-ld.h>
> > +
> >   /* Information used by audit modules.  For most link maps, this data
> >      immediate follows the link map in memory.  For the dynamic linker,
> >      it is allocated separately.  See link_map_audit_state in
> > diff --git a/sysdeps/generic/dl-relocate-ld.h b/sysdeps/generic/dl-relocate-ld.h
> > new file mode 100644
> > index 0000000000..5fae206db9
> > --- /dev/null
> > +++ b/sysdeps/generic/dl-relocate-ld.h
> > @@ -0,0 +1,32 @@
> > +/* Check if dynamic section should be relocated.  Generic 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_RELOCATE_LD_H
> > +#define _DL_RELOCATE_LD_H
> > +
> > +/* Return true if dynamic section in the shared library L should be
> > +   relocated.  */
> > +
> > +static inline bool
> > +dl_relocate_ld (const struct link_map *l)
> > +{
> > +  /* Don't relocate dynamic section if it is readonly  */
> > +  return !l->l_ld_readonly;
> > +}
>
> Depend on read-only flag for all architectures except those that
> override this definition.  OK.
>
> > +
> > +#endif /* _DL_RELOCATE_LD_H */
> > diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
> > index fd67871f4b..eafa308047 100644
> > --- a/sysdeps/generic/ldsodefs.h
> > +++ b/sysdeps/generic/ldsodefs.h
> > @@ -75,11 +75,8 @@ __BEGIN_DECLS
> >     have to be accessed via the D_PTR macro.  The macro is needed since for
> >     most architectures the entry is already relocated - but for some not
> >     and we need to relocate at access time.  */
> > -#ifdef DL_RO_DYN_SECTION
> > -# define D_PTR(map, i) ((map)->i->d_un.d_ptr + (map)->l_addr)
> > -#else
> > -# define D_PTR(map, i) (map)->i->d_un.d_ptr
> > -#endif
> > +#define D_PTR(map, i) \
> > +  ((map)->i->d_un.d_ptr + (dl_relocate_ld (map) ? 0 : (map)->l_addr))
>
> Simplify D_PTR to add l_addr for read-only maps.
>
> >
> >   /* Result of the lookup functions and how to retrieve the base address.  */
> >   typedef struct link_map *lookup_t;
> > diff --git a/sysdeps/mips/dl-relocate-ld.h b/sysdeps/mips/dl-relocate-ld.h
> > new file mode 100644
> > index 0000000000..0c18d9a567
> > --- /dev/null
> > +++ b/sysdeps/mips/dl-relocate-ld.h
> > @@ -0,0 +1,32 @@
> > +/* Check if dynamic section should be relocated.  MIPS 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_RELOCATE_LD_H
> > +#define _DL_RELOCATE_LD_H
> > +
> > +/* Return true if dynamic section in the shared library L should be
> > +   relocated.  */
> > +
> > +static inline bool
> > +dl_relocate_ld (const struct link_map *l)
> > +{
> > +  /* Never relocate dynamic section.  */
> > +  return false;
> > +}
>
> mips does not like relocating the dynamic section at all.  OK.
>
> > +
> > +#endif /* _DL_RELOCATE_LD_H */
> > diff --git a/sysdeps/mips/ldsodefs.h b/sysdeps/mips/ldsodefs.h
> > index 4db7c60e38..36fd09a8bd 100644
> > --- a/sysdeps/mips/ldsodefs.h
> > +++ b/sysdeps/mips/ldsodefs.h
> > @@ -75,10 +75,6 @@ struct La_mips_64_retval;
> >                                         struct La_mips_64_retval *,       \
> >                                         const char *);
> >
> > -/* The MIPS ABI specifies that the dynamic section has to be read-only.  */
> > -
> > -#define DL_RO_DYN_SECTION 1
> > -
> >   #include_next <ldsodefs.h>
> >
> >   /* The 64-bit MIPS ELF ABI uses an unusual reloc format.  Each
> > diff --git a/sysdeps/riscv/dl-relocate-ld.h b/sysdeps/riscv/dl-relocate-ld.h
> > new file mode 100644
> > index 0000000000..10327454b1
> > --- /dev/null
> > +++ b/sysdeps/riscv/dl-relocate-ld.h
> > @@ -0,0 +1,32 @@
> > +/* Check if dynamic section should be relocated.  RISC-V 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_RELOCATE_LD_H
> > +#define _DL_RELOCATE_LD_H
> > +
> > +/* Return true if dynamic section in the shared library L should be
> > +   relocated.  */
> > +
> > +static inline bool
> > +dl_relocate_ld (const struct link_map *l)
> > +{
> > +  /* Never relocate dynamic section for ABI compatibility.  */
> > +  return false;
> > +}
>
> Neither does risc-v.  OK.
>
> > +
> > +#endif /* _DL_RELOCATE_LD_H */
> > diff --git a/sysdeps/riscv/ldsodefs.h b/sysdeps/riscv/ldsodefs.h
> > index 0c696714a7..8947ffe4b5 100644
> > --- a/sysdeps/riscv/ldsodefs.h
> > +++ b/sysdeps/riscv/ldsodefs.h
> > @@ -38,11 +38,6 @@ struct La_riscv_retval;
> >                                      struct La_riscv_retval *,        \
> >                                      const char *);
> >
> > -/* Although the RISC-V ABI does not specify that the dynamic section has
> > -   to be read-only, it needs to be kept for ABI compatibility.  */
> > -
> > -#define DL_RO_DYN_SECTION 1
> > -
> >   #include_next <ldsodefs.h>
> >
> >   #endif
> >



-- 
H.J.