[PING**3][PATCH 2/3] gdb: Add soname to build-id mapping for corefiles

[Aaron Merey <amerey@redhat.com>]

Ping.

Thanks,
Aaron

On Mon, Oct 18, 2021 at 7:06 PM Aaron Merey <amerey@redhat.com> wrote:
>
> Ping
>
> Thanks,
> Aaron
>
> On Tue, Sep 28, 2021 at 9:12 PM Aaron Merey <amerey@redhat.com> wrote:
> >
> > Ping.
> >
> > Thanks,
> > Aaron
> >
> > On Wed, Aug 18, 2021 at 10:22 PM Aaron Merey via Gdb-patches
> > <gdb-patches@sourceware.org> wrote:
> > >
> > > Hi Lancelot and Simon,
> > >
> > > Thanks for the reviews. The updated patch is included below.
> > >
> > > On Tue, Aug 17, 2021 at 9:59 AM Simon Marchi <simon.marchi@polymtl.ca> wrote:
> > > >>> +  /* Check that bfd is an ET_DYN ELF file.  */
> > > >>> +  bfd_check_format (abfd.get (), bfd_object);
> > > >
> > > > I asked this in my previous review, still applies here:
> > > >
> > > >   What's the point of calling bfd_check_format without checking the
> > > >   result?  It looks like a function without side-effects.
> > >
> > > I included a few comments in the [PATCH 0/3] email for this series[1].
> > > I mentioned that for some reason bfd_check_format appears to update
> > > the bfd 'flags' field with the correct value. If bfd_check_format is not
> > > called here the check for the DYNAMIC flag fails even for ET_DYN files.
> > >
> > > [1] https://sourceware.org/pipermail/gdb-patches/2021-August/181416.html
> > >
> > > ---
> > >  gdb/arch-utils.c | 15 +++++----------
> > >  gdb/arch-utils.h | 23 +++++++++++++----------
> > >  gdb/build-id.h   |  2 ++
> > >  gdb/corelow.c    | 13 ++++++++++++-
> > >  gdb/gdbarch.c    |  2 +-
> > >  gdb/gdbarch.h    |  4 ++--
> > >  gdb/gdbarch.sh   |  2 +-
> > >  gdb/linux-tdep.c | 46 ++++++++++++++++++++++++++++++++++------------
> > >  gdb/progspace.c  | 32 ++++++++++++++++++++++++++++++++
> > >  gdb/progspace.h  | 17 +++++++++++++++++
> > >  gdb/solib.c      | 35 +++++++++++++++++++++++++++++++++++
> > >  gdb/solib.h      |  5 +++++
> > >  12 files changed, 159 insertions(+), 37 deletions(-)
> > >
> > > diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c
> > > index 862f26b6cf7..ffb32cb203f 100644
> > > --- a/gdb/arch-utils.c
> > > +++ b/gdb/arch-utils.c
> > > @@ -1075,16 +1075,11 @@ default_get_pc_address_flags (frame_info *frame, CORE_ADDR pc)
> > >
> > >  /* See arch-utils.h.  */
> > >  void
> > > -default_read_core_file_mappings (struct gdbarch *gdbarch,
> > > -                                struct bfd *cbfd,
> > > -                                gdb::function_view<void (ULONGEST count)>
> > > -                                  pre_loop_cb,
> > > -                                gdb::function_view<void (int num,
> > > -                                                         ULONGEST start,
> > > -                                                         ULONGEST end,
> > > -                                                         ULONGEST file_ofs,
> > > -                                                         const char *filename)>
> > > -                                  loop_cb)
> > > +default_read_core_file_mappings
> > > + (struct gdbarch *gdbarch,
> > > +  struct bfd *cbfd,
> > > +  gdb::function_view<void (ULONGEST count)> pre_loop_cb,
> > > +  loop_cb_ftype loop_cb)
> > >  {
> > >  }
> > >
> > > diff --git a/gdb/arch-utils.h b/gdb/arch-utils.h
> > > index 03e9082f6d7..2243c3fb85b 100644
> > > --- a/gdb/arch-utils.h
> > > +++ b/gdb/arch-utils.h
> > > @@ -294,15 +294,18 @@ extern ULONGEST default_type_align (struct gdbarch *gdbarch,
> > >  extern std::string default_get_pc_address_flags (frame_info *frame,
> > >                                                  CORE_ADDR pc);
> > >
> > > +
> > > +using loop_cb_ftype = gdb::function_view<void (int num,
> > > +                                              ULONGEST start,
> > > +                                              ULONGEST end,
> > > +                                              ULONGEST file_ofs,
> > > +                                              const char *filename,
> > > +                                              const bfd_build_id *build_id)>;
> > > +
> > >  /* Default implementation of gdbarch read_core_file_mappings method.  */
> > > -extern void default_read_core_file_mappings (struct gdbarch *gdbarch,
> > > -                                            struct bfd *cbfd,
> > > -                                            gdb::function_view<void (ULONGEST count)>
> > > -                                              pre_loop_cb,
> > > -                                            gdb::function_view<void (int num,
> > > -                                                                     ULONGEST start,
> > > -                                                                     ULONGEST end,
> > > -                                                                     ULONGEST file_ofs,
> > > -                                                                     const char *filename)>
> > > -                                              loop_cb);
> > > +extern void default_read_core_file_mappings
> > > + (struct gdbarch *gdbarch,
> > > +  struct bfd *cbfd,
> > > +  gdb::function_view<void (ULONGEST count)> pre_loop_cb,
> > > +  loop_cb_ftype loop_cb);
> > >  #endif /* ARCH_UTILS_H */
> > > diff --git a/gdb/build-id.h b/gdb/build-id.h
> > > index 42f8d57ede1..3c9402ee71b 100644
> > > --- a/gdb/build-id.h
> > > +++ b/gdb/build-id.h
> > > @@ -20,8 +20,10 @@
> > >  #ifndef BUILD_ID_H
> > >  #define BUILD_ID_H
> > >
> > > +#include "defs.h"
> > >  #include "gdb_bfd.h"
> > >  #include "gdbsupport/rsp-low.h"
> > > +#include <string>
> > >
> > >  /* Locate NT_GNU_BUILD_ID from ABFD and return its content.  */
> > >
> > > diff --git a/gdb/corelow.c b/gdb/corelow.c
> > > index eb785a08633..31af0f22584 100644
> > > --- a/gdb/corelow.c
> > > +++ b/gdb/corelow.c
> > > @@ -214,7 +214,7 @@ core_target::build_file_mappings ()
> > >      /* read_core_file_mappings will invoke this lambda for each mapping
> > >         that it finds.  */
> > >      [&] (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs,
> > > -        const char *filename)
> > > +        const char *filename, const bfd_build_id *build_id)
> > >        {
> > >         /* Architecture-specific read_core_mapping methods are expected to
> > >            weed out non-file-backed mappings.  */
> > > @@ -282,6 +282,16 @@ core_target::build_file_mappings ()
> > >
> > >         /* Set target_section fields.  */
> > >         m_core_file_mappings.emplace_back (start, end, sec);
> > > +
> > > +       /* If this is a bfd of a shared library, record its soname
> > > +          and build id.  */
> > > +       if (build_id != nullptr)
> > > +         {
> > > +           gdb::optional<std::string> soname = gdb_bfd_read_elf_soname (bfd);
> > > +           if (soname)
> > > +             current_program_space->set_cbfd_soname_build_id
> > > +              (std::move (*soname), build_id);
> > > +         }
> > >        });
> > >
> > >    normalize_mem_ranges (&m_core_unavailable_mappings);
> > > @@ -305,6 +315,7 @@ core_target::close ()
> > >          comments in clear_solib in solib.c.  */
> > >        clear_solib ();
> > >
> > > +      current_program_space->clear_cbfd_soname_build_ids ();
> > >        current_program_space->cbfd.reset (nullptr);
> > >      }
> > >
> > > diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c
> > > index f89dcc57754..35464115039 100644
> > > --- a/gdb/gdbarch.c
> > > +++ b/gdb/gdbarch.c
> > > @@ -5411,7 +5411,7 @@ set_gdbarch_get_pc_address_flags (struct gdbarch *gdbarch,
> > >  }
> > >
> > >  void
> > > -gdbarch_read_core_file_mappings (struct gdbarch *gdbarch, struct bfd *cbfd, gdb::function_view<void (ULONGEST count)> pre_loop_cb, gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename)> loop_cb)
> > > +gdbarch_read_core_file_mappings (struct gdbarch *gdbarch, struct bfd *cbfd, gdb::function_view<void (ULONGEST count)> pre_loop_cb, gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename, const bfd_build_id *build_id)> loop_cb)
> > >  {
> > >    gdb_assert (gdbarch != NULL);
> > >    gdb_assert (gdbarch->read_core_file_mappings != NULL);
> > > diff --git a/gdb/gdbarch.h b/gdb/gdbarch.h
> > > index 979159ba2f5..baf80580d60 100644
> > > --- a/gdb/gdbarch.h
> > > +++ b/gdb/gdbarch.h
> > > @@ -1710,8 +1710,8 @@ extern void set_gdbarch_get_pc_address_flags (struct gdbarch *gdbarch, gdbarch_g
> > >
> > >  /* Read core file mappings */
> > >
> > > -typedef void (gdbarch_read_core_file_mappings_ftype) (struct gdbarch *gdbarch, struct bfd *cbfd, gdb::function_view<void (ULONGEST count)> pre_loop_cb, gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename)> loop_cb);
> > > -extern void gdbarch_read_core_file_mappings (struct gdbarch *gdbarch, struct bfd *cbfd, gdb::function_view<void (ULONGEST count)> pre_loop_cb, gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename)> loop_cb);
> > > +typedef void (gdbarch_read_core_file_mappings_ftype) (struct gdbarch *gdbarch, struct bfd *cbfd, gdb::function_view<void (ULONGEST count)> pre_loop_cb, gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename, const bfd_build_id *build_id)> loop_cb);
> > > +extern void gdbarch_read_core_file_mappings (struct gdbarch *gdbarch, struct bfd *cbfd, gdb::function_view<void (ULONGEST count)> pre_loop_cb, gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename, const bfd_build_id *build_id)> loop_cb);
> > >  extern void set_gdbarch_read_core_file_mappings (struct gdbarch *gdbarch, gdbarch_read_core_file_mappings_ftype *read_core_file_mappings);
> > >
> > >  extern struct gdbarch_tdep *gdbarch_tdep (struct gdbarch *gdbarch);
> > > diff --git a/gdb/gdbarch.sh b/gdb/gdbarch.sh
> > > index 39a99d0d5f3..c24079d34f3 100755
> > > --- a/gdb/gdbarch.sh
> > > +++ b/gdb/gdbarch.sh
> > > @@ -1210,7 +1210,7 @@ m;ULONGEST;type_align;struct type *type;type;;default_type_align;;0
> > >  f;std::string;get_pc_address_flags;frame_info *frame, CORE_ADDR pc;frame, pc;;default_get_pc_address_flags;;0
> > >
> > >  # Read core file mappings
> > > -m;void;read_core_file_mappings;struct bfd *cbfd, gdb::function_view<void (ULONGEST count)> pre_loop_cb, gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename)> loop_cb;cbfd, pre_loop_cb, loop_cb;;default_read_core_file_mappings;;0
> > > +m;void;read_core_file_mappings;struct bfd *cbfd, gdb::function_view<void (ULONGEST count)> pre_loop_cb, gdb::function_view<void (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs, const char *filename, const bfd_build_id *build_id)> loop_cb;cbfd, pre_loop_cb, loop_cb;;default_read_core_file_mappings;;0
> > >
> > >  EOF
> > >  }
> > > diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
> > > index ae2f7c14f6d..812ca1f99bf 100644
> > > --- a/gdb/linux-tdep.c
> > > +++ b/gdb/linux-tdep.c
> > > @@ -44,6 +44,7 @@
> > >  #include "solib-svr4.h"
> > >
> > >  #include <ctype.h>
> > > +#include <unordered_map>
> > >
> > >  /* This enum represents the values that the user can choose when
> > >     informing the Linux kernel about which memory mappings will be
> > > @@ -1097,16 +1098,11 @@ linux_info_proc (struct gdbarch *gdbarch, const char *args,
> > >     for each mapping.  */
> > >
> > >  static void
> > > -linux_read_core_file_mappings (struct gdbarch *gdbarch,
> > > -                              struct bfd *cbfd,
> > > -                              gdb::function_view<void (ULONGEST count)>
> > > -                                pre_loop_cb,
> > > -                              gdb::function_view<void (int num,
> > > -                                                       ULONGEST start,
> > > -                                                       ULONGEST end,
> > > -                                                       ULONGEST file_ofs,
> > > -                                                       const char *filename)>
> > > -                                loop_cb)
> > > +linux_read_core_file_mappings
> > > + (struct gdbarch *gdbarch,
> > > +  struct bfd *cbfd,
> > > +  gdb::function_view<void (ULONGEST count)> pre_loop_cb,
> > > +  loop_cb_ftype  loop_cb)
> > >  {
> > >    /* Ensure that ULONGEST is big enough for reading 64-bit core files.  */
> > >    gdb_static_assert (sizeof (ULONGEST) >= 8);
> > > @@ -1175,6 +1171,23 @@ linux_read_core_file_mappings (struct gdbarch *gdbarch,
> > >    if (f != descend)
> > >      warning (_("malformed note - filename area is too big"));
> > >
> > > +  const bfd_build_id *orig_build_id = cbfd->build_id;
> > > +  std::unordered_map<ULONGEST, const bfd_build_id *> vma_map;
> > > +  std::unordered_map<char *, const bfd_build_id *> filename_map;
> > > +
> > > +  /* Search for solib build-ids in the core file.  Each time one is found,
> > > +     map the start vma of the corresponding elf header to the build-id.  */
> > > +  for (bfd_section *sec = cbfd->sections; sec != nullptr; sec = sec->next)
> > > +    {
> > > +      cbfd->build_id = nullptr;
> > > +
> > > +      if (sec->flags & SEC_LOAD
> > > +         && get_elf_backend_data (cbfd)->elf_backend_core_find_build_id
> > > +              (cbfd, (bfd_vma) sec->filepos))
> > > +       vma_map[sec->vma] = cbfd->build_id;
> > > +    }
> > > +
> > > +  cbfd->build_id = orig_build_id;
> > >    pre_loop_cb (count);
> > >
> > >    for (int i = 0; i < count; i++)
> > > @@ -1188,8 +1201,17 @@ linux_read_core_file_mappings (struct gdbarch *gdbarch,
> > >        descdata += addr_size;
> > >        char * filename = filenames;
> > >        filenames += strlen ((char *) filenames) + 1;
> > > +      const bfd_build_id *build_id = vma_map[start];
> > > +
> > > +      /* Map filename to the build-id associated with this start vma,
> > > +        if such a build-id was found.  Otherwise use the build-id
> > > +        already associated with this filename if it exists. */
> > > +      if (build_id != nullptr)
> > > +       filename_map[filename] = build_id;
> > > +      else
> > > +       build_id = filename_map[filename];
> > >
> > > -      loop_cb (i, start, end, file_ofs, filename);
> > > +      loop_cb (i, start, end, file_ofs, filename, build_id);
> > >      }
> > >  }
> > >
> > > @@ -1218,7 +1240,7 @@ linux_core_info_proc_mappings (struct gdbarch *gdbarch, const char *args)
> > >           }
> > >        },
> > >      [=] (int num, ULONGEST start, ULONGEST end, ULONGEST file_ofs,
> > > -        const char *filename)
> > > +        const char *filename, const bfd_build_id *build_id)
> > >        {
> > >         if (gdbarch_addr_bit (gdbarch) == 32)
> > >           printf_filtered ("\t%10s %10s %10s %10s %s\n",
> > > diff --git a/gdb/progspace.c b/gdb/progspace.c
> > > index 7080bf8ee27..8b7b949d959 100644
> > > --- a/gdb/progspace.c
> > > +++ b/gdb/progspace.c
> > > @@ -17,6 +17,7 @@
> > >     You should have received a copy of the GNU General Public License
> > >     along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> > >
> > > +#include "build-id.h"
> > >  #include "defs.h"
> > >  #include "gdbcmd.h"
> > >  #include "objfiles.h"
> > > @@ -358,6 +359,37 @@ print_program_space (struct ui_out *uiout, int requested)
> > >      }
> > >  }
> > >
> > > +/* See progspace.h.  */
> > > +
> > > +void
> > > +program_space::set_cbfd_soname_build_id (std::string soname,
> > > +                                        const bfd_build_id *build_id)
> > > +{
> > > +  cbfd_soname_to_build_id[std::move (soname)] = build_id_to_string (build_id);
> > > +}
> > > +
> > > +/* See progspace.h.  */
> > > +
> > > +const char *
> > > +program_space::get_cbfd_soname_build_id (const char *soname)
> > > +{
> > > +  gdb_assert (soname);
> > > +
> > > +  auto it = cbfd_soname_to_build_id.find (basename (soname));
> > > +  if (it == cbfd_soname_to_build_id.end ())
> > > +    return nullptr;
> > > +
> > > +  return it->second.c_str ();
> > > +}
> > > +
> > > +/* See progspace.h.  */
> > > +
> > > +void
> > > +program_space::clear_cbfd_soname_build_ids ()
> > > +{
> > > +  cbfd_soname_to_build_id.clear ();
> > > +}
> > > +
> > >  /* Boolean test for an already-known program space id.  */
> > >
> > >  static int
> > > diff --git a/gdb/progspace.h b/gdb/progspace.h
> > > index fb348ca7539..b42b3ffc4f1 100644
> > > --- a/gdb/progspace.h
> > > +++ b/gdb/progspace.h
> > > @@ -30,6 +30,7 @@
> > >  #include "gdbsupport/safe-iterator.h"
> > >  #include <list>
> > >  #include <vector>
> > > +#include <unordered_map>
> > >
> > >  struct target_ops;
> > >  struct bfd;
> > > @@ -324,6 +325,19 @@ struct program_space
> > >    /* Binary file diddling handle for the core file.  */
> > >    gdb_bfd_ref_ptr cbfd;
> > >
> > > +  /* Associate a core file SONAME with BUILD_ID so that it can be retrieved
> > > +     with get_cbfd_soname_build_id.  */
> > > +  void set_cbfd_soname_build_id (std::string soname,
> > > +                                const bfd_build_id *build_id);
> > > +
> > > +  /* If a core file SONAME had a build-id associated with it by a previous
> > > +     call to set_cbfd_soname_build_id then return the build-id as a
> > > +     NULL-terminated hex string.  */
> > > +  const char *get_cbfd_soname_build_id (const char *soname);
> > > +
> > > +  /* Clear all core file soname to build-id mappings.  */
> > > +  void clear_cbfd_soname_build_ids ();
> > > +
> > >    /* The address space attached to this program space.  More than one
> > >       program space may be bound to the same address space.  In the
> > >       traditional unix-like debugging scenario, this will usually
> > > @@ -378,6 +392,9 @@ struct program_space
> > >    /* The set of target sections matching the sections mapped into
> > >       this program space.  Managed by both exec_ops and solib.c.  */
> > >    target_section_table m_target_sections;
> > > +
> > > +  /* Mapping of a core file's library sonames to their respective build-ids.  */
> > > +  std::unordered_map<std::string, std::string> cbfd_soname_to_build_id;
> > >  };
> > >
> > >  /* An address space.  It is used for comparing if
> > > diff --git a/gdb/solib.c b/gdb/solib.c
> > > index e30affbb7e7..1b99c8ab985 100644
> > > --- a/gdb/solib.c
> > > +++ b/gdb/solib.c
> > > @@ -23,6 +23,7 @@
> > >  #include <fcntl.h>
> > >  #include "symtab.h"
> > >  #include "bfd.h"
> > > +#include "build-id.h"
> > >  #include "symfile.h"
> > >  #include "objfiles.h"
> > >  #include "gdbcore.h"
> > > @@ -1585,6 +1586,40 @@ gdb_bfd_scan_elf_dyntag (const int desired_dyntag, bfd *abfd, CORE_ADDR *ptr,
> > >    return 0;
> > >  }
> > >
> > > +/* See solib.h.  */
> > > +
> > > +gdb::optional<std::string>
> > > +gdb_bfd_read_elf_soname (struct bfd *bfd)
> > > +{
> > > +  gdb_assert (bfd != nullptr);
> > > +
> > > +  gdb_bfd_ref_ptr abfd = gdb_bfd_open (bfd->filename, gnutarget);
> > > +
> > > +  if (abfd == nullptr)
> > > +    return {};
> > > +
> > > +  /* Check that bfd is an ET_DYN ELF file.  */
> > > +  bfd_check_format (abfd.get (), bfd_object);
> > > +  if (!(bfd_get_file_flags (abfd.get ()) & DYNAMIC))
> > > +    return {};
> > > +
> > > +  /* Determine soname of shared library.  If found map soname to build-id.  */
> > > +  CORE_ADDR idx;
> > > +  if (!gdb_bfd_scan_elf_dyntag (DT_SONAME, abfd.get (), &idx, nullptr))
> > > +    return {};
> > > +
> > > +  struct bfd_section *dynstr = bfd_get_section_by_name (abfd.get (), ".dynstr");
> > > +  if (dynstr == nullptr || bfd_section_size (dynstr) <= idx)
> > > +    return {};
> > > +
> > > +  /* Read the soname from the string table.  */
> > > +  gdb::byte_vector dynstr_buf;
> > > +  if (!gdb_bfd_get_full_section_contents (abfd.get (), dynstr, &dynstr_buf))
> > > +    return {};
> > > +
> > > +  return std::string ((const char *)dynstr_buf.data () + idx);
> > > +}
> > > +
> > >  /* Lookup the value for a specific symbol from symbol table.  Look up symbol
> > >     from ABFD.  MATCH_SYM is a callback function to determine whether to pick
> > >     up a symbol.  DATA is the input of this callback function.  Return NULL
> > > diff --git a/gdb/solib.h b/gdb/solib.h
> > > index c50f74e06bf..51cc047463f 100644
> > > --- a/gdb/solib.h
> > > +++ b/gdb/solib.h
> > > @@ -118,6 +118,11 @@ extern CORE_ADDR gdb_bfd_lookup_symbol_from_symtab (bfd *abfd,
> > >  extern int gdb_bfd_scan_elf_dyntag (const int desired_dyntag, bfd *abfd,
> > >                                     CORE_ADDR *ptr, CORE_ADDR *ptr_addr);
> > >
> > > +/* If BFD is an ELF shared object then attempt to return the string
> > > +   referred to by its DT_SONAME tag.   */
> > > +
> > > +extern gdb::optional<std::string> gdb_bfd_read_elf_soname (struct bfd *bfd);
> > > +
> > >  /* Enable or disable optional solib event breakpoints as appropriate.  */
> > >
> > >  extern void update_solib_breakpoints (void);
> > > --
> > > 2.31.1
> > >