Re: [PATCH 3/3] PR gdb/27570: missing support for debuginfod in core_target::build_file_mappings

[Aaron Merey <amerey@redhat.com>]

Ping ** 2

Thanks,
Aaron

On Tue, Jan 25, 2022 at 8:42 PM Aaron Merey <amerey@redhat.com> wrote:
>
> Ping
>
> Thanks,
> Aaron
>
> On Tue, Nov 16, 2021 at 10:28 PM Aaron Merey via Gdb-patches
> <gdb-patches@sourceware.org> wrote:
> >
> > Hi Simon,
> >
> > I've fixed the issues you pointed out.  The revised patch is below.
> >
> > Thanks,
> > Aaron
> >
> > From 357ffcc705057b4ed324cc39c2f5159693491fbe Mon Sep 17 00:00:00 2001
> > From: Aaron Merey <amerey@redhat.com>
> > Date: Tue, 16 Nov 2021 19:45:44 -0500
> > Subject: [PATCH 3/3] PR gdb/27570: missing support for debuginfod in
> >  core_target::build_file_mappings
> >
> > Add debuginfod support to core_target::build_file_mappings and
> > locate_exec_from_corefile_build_id to enable the downloading of
> > missing executables and shared libraries referenced in core files.
> >
> > Also add debuginfod support to solib_map_sections so that previously
> > downloaded shared libraries can be retrieved from the debuginfod
> > cache.
> >
> > When core file shared libraries are found locally, verify that
> > their build-ids match the corresponding build-ids found in the
> > core file.  If there is a mismatch, attempt to query debuginfod
> > for the correct build and print a warning if unsuccessful:
> >
> >   warning: Build-id of /lib64/libc.so.6 does not match core file.
> >
> > Also unset the DEBUGINFOD_URLS environment variable in gcore.in
> > to disable debuginfod when gcore invokes gdb.  Debuginfo is not
> > needed for core file generation so debuginfod queries will slow
> > down gcore unnecessarily.
> > ---
> >  gdb/corelow.c                                 | 27 ++++++++++++
> >  gdb/debuginfod-support.c                      | 44 +++++++++++++++++++
> >  gdb/debuginfod-support.h                      | 17 +++++++
> >  gdb/gcore.in                                  |  3 ++
> >  gdb/solib.c                                   | 34 ++++++++++++++
> >  .../gdb.debuginfod/fetch_src_and_symbols.exp  | 22 ++++++++++
> >  6 files changed, 147 insertions(+)
> >
> > diff --git a/gdb/corelow.c b/gdb/corelow.c
> > index d1256a9e99b..8141f815e39 100644
> > --- a/gdb/corelow.c
> > +++ b/gdb/corelow.c
> > @@ -46,6 +46,8 @@
> >  #include "gdbsupport/filestuff.h"
> >  #include "build-id.h"
> >  #include "gdbsupport/pathstuff.h"
> > +#include "gdbsupport/scoped_fd.h"
> > +#include "debuginfod-support.h"
> >  #include <unordered_map>
> >  #include <unordered_set>
> >  #include "gdbcmd.h"
> > @@ -229,6 +231,11 @@ core_target::build_file_mappings ()
> >                canonical) pathname will be provided.  */
> >             gdb::unique_xmalloc_ptr<char> expanded_fname
> >               = exec_file_find (filename, NULL);
> > +
> > +           if (expanded_fname == nullptr && build_id != nullptr)
> > +             debuginfod_exec_query (build_id->data, build_id->size,
> > +                                    filename, &expanded_fname);
> > +
> >             if (expanded_fname == nullptr)
> >               {
> >                 m_core_unavailable_mappings.emplace_back (start, end - start);
> > @@ -410,6 +417,26 @@ locate_exec_from_corefile_build_id (bfd *abfd, int from_tty)
> >    gdb_bfd_ref_ptr execbfd
> >      = build_id_to_exec_bfd (build_id->size, build_id->data);
> >
> > +  if (execbfd == nullptr)
> > +    {
> > +      /* Attempt to query debuginfod for the executable.  */
> > +      gdb::unique_xmalloc_ptr<char> execpath;
> > +      scoped_fd fd = debuginfod_exec_query (build_id->data, build_id->size,
> > +                                           abfd->filename, &execpath);
> > +
> > +      if (fd.get () >= 0)
> > +       {
> > +         execbfd = gdb_bfd_open (execpath.get (), gnutarget);
> > +
> > +         if (execbfd == nullptr)
> > +           warning (_("File \"%s\" from debuginfod cannot be opened as bfd"),
> > +                    execpath.get ());
> > +         else if (!build_id_verify (execbfd.get (), build_id->size,
> > +                                    build_id->data))
> > +           execbfd.reset (nullptr);
> > +       }
> > +    }
> > +
> >    if (execbfd != nullptr)
> >      {
> >        exec_file_attach (bfd_get_filename (execbfd.get ()), from_tty);
> > diff --git a/gdb/debuginfod-support.c b/gdb/debuginfod-support.c
> > index 2e1837da949..c4c593148b6 100644
> > --- a/gdb/debuginfod-support.c
> > +++ b/gdb/debuginfod-support.c
> > @@ -68,6 +68,15 @@ debuginfod_debuginfo_query (const unsigned char *build_id,
> >    return scoped_fd (-ENOSYS);
> >  }
> >
> > +scoped_fd
> > +debuginfod_exec_query (const unsigned char *build_id,
> > +                      int build_id_len,
> > +                      const char *filename,
> > +                      gdb::unique_xmalloc_ptr<char> *destname)
> > +{
> > +  return scoped_fd (-ENOSYS);
> > +}
> > +
> >  #define NO_IMPL _("Support for debuginfod is not compiled into GDB.")
> >
> >  #else
> > @@ -256,6 +265,41 @@ debuginfod_debuginfo_query (const unsigned char *build_id,
> >
> >    return fd;
> >  }
> > +
> > +/* See debuginfod-support.h  */
> > +
> > +scoped_fd
> > +debuginfod_exec_query (const unsigned char *build_id,
> > +                      int build_id_len,
> > +                      const char *filename,
> > +                      gdb::unique_xmalloc_ptr<char> *destname)
> > +{
> > +  if (!debuginfod_is_enabled ())
> > +    return scoped_fd (-ENOSYS);
> > +
> > +  debuginfod_client *c = get_debuginfod_client ();
> > +
> > +  if (c == nullptr)
> > +    return scoped_fd (-ENOMEM);
> > +
> > +  char *dname = nullptr;
> > +  user_data data ("executable for", filename);
> > +
> > +  debuginfod_set_user_data (c, &data);
> > +  scoped_fd fd (debuginfod_find_executable (c, build_id, build_id_len, &dname));
> > +  debuginfod_set_user_data (c, nullptr);
> > +
> > +  if (debuginfod_verbose > 0 && fd.get () < 0 && fd.get () != -ENOENT)
> > +    printf_filtered (_("Download failed: %s. " \
> > +                      "Continuing without executable for %ps.\n"),
> > +                    safe_strerror (-fd.get ()),
> > +                    styled_string (file_name_style.style (),  filename));
> > +
> > +  if (fd.get () >= 0)
> > +    destname->reset (dname);
> > +
> > +  return fd;
> > +}
> >  #endif
> >
> >  /* Set callback for "set debuginfod enabled".  */
> > diff --git a/gdb/debuginfod-support.h b/gdb/debuginfod-support.h
> > index 5e5aab56e74..7815a2f6ede 100644
> > --- a/gdb/debuginfod-support.h
> > +++ b/gdb/debuginfod-support.h
> > @@ -61,4 +61,21 @@ debuginfod_debuginfo_query (const unsigned char *build_id,
> >                             const char *filename,
> >                             gdb::unique_xmalloc_ptr<char> *destname);
> >
> > +/* Query debuginfod servers for an executable file with BUILD_ID.
> > +   BUILD_ID can be given as a binary blob or a null-terminated string.
> > +   If given as a binary blob, BUILD_ID_LEN should be the number of bytes.
> > +   If given as a null-terminated string, BUILD_ID_LEN should be 0.
> > +
> > +   FILENAME should be the name or path associated with the executable.
> > +   It is used for printing messages to the user.
> > +
> > +   If the file is successfully retrieved, its path on the local machine
> > +   is stored in DESTNAME.  If GDB is not built with debuginfod, this
> > +   function returns -ENOSYS.  */
> > +
> > +extern scoped_fd debuginfod_exec_query (const unsigned char *build_id,
> > +                                       int build_id_len,
> > +                                       const char *filename,
> > +                                       gdb::unique_xmalloc_ptr<char>
> > +                                         *destname);
> >  #endif /* DEBUGINFOD_SUPPORT_H */
> > diff --git a/gdb/gcore.in b/gdb/gcore.in
> > index 24354a79e27..25b24c3cd3d 100644
> > --- a/gdb/gcore.in
> > +++ b/gdb/gcore.in
> > @@ -89,6 +89,9 @@ if [ ! -f "$binary_path/@GDB_TRANSFORM_NAME@" ]; then
> >    exit 1
> >  fi
> >
> > +# Prevent unnecessary debuginfod queries during core file generation.
> > +unset DEBUGINFOD_URLS
> > +
> >  # Initialise return code.
> >  rc=0
> >
> > diff --git a/gdb/solib.c b/gdb/solib.c
> > index c0beea19d7b..87a3fc0c462 100644
> > --- a/gdb/solib.c
> > +++ b/gdb/solib.c
> > @@ -49,6 +49,8 @@
> >  #include "filesystem.h"
> >  #include "gdb_bfd.h"
> >  #include "gdbsupport/filestuff.h"
> > +#include "gdbsupport/scoped_fd.h"
> > +#include "debuginfod-support.h"
> >  #include "source.h"
> >  #include "cli/cli-style.h"
> >
> > @@ -539,6 +541,38 @@ solib_map_sections (struct so_list *so)
> >
> >    gdb::unique_xmalloc_ptr<char> filename (tilde_expand (so->so_name));
> >    gdb_bfd_ref_ptr abfd (ops->bfd_open (filename.get ()));
> > +  const char *build_id_hexstr =
> > +    current_program_space->get_cbfd_soname_build_id (so->so_name);
> > +
> > +  /* If we already know the build-id of this solib from a core file,
> > +     verify it matches abfd's build-id.  If there is a mismatch or
> > +     the solib wasn't found, attempt to query debuginfod for
> > +     the correct solib.  */
> > +  if (build_id_hexstr != nullptr)
> > +    {
> > +      bool mismatch = false;
> > +
> > +      if (abfd != nullptr && abfd->build_id != nullptr)
> > +       {
> > +         std::string build_id = build_id_to_string (abfd->build_id);
> > +
> > +         if (build_id != build_id_hexstr)
> > +           mismatch = true;
> > +       }
> > +
> > +      if (abfd == nullptr || mismatch)
> > +       {
> > +         scoped_fd fd = debuginfod_exec_query ((const unsigned char*)
> > +                                               build_id_hexstr,
> > +                                               0, so->so_name, &filename);
> > +
> > +         if (fd.get () >= 0)
> > +           abfd = ops->bfd_open (filename.get ());
> > +         else if (mismatch)
> > +           warning (_("Build-id of %ps does not match core file."),
> > +                    styled_string (file_name_style.style (), filename.get ()));
> > +       }
> > +    }
> >
> >    if (abfd == NULL)
> >      return 0;
> > diff --git a/gdb/testsuite/gdb.debuginfod/fetch_src_and_symbols.exp b/gdb/testsuite/gdb.debuginfod/fetch_src_and_symbols.exp
> > index 757bd201b17..cfe2ae7f7da 100644
> > --- a/gdb/testsuite/gdb.debuginfod/fetch_src_and_symbols.exp
> > +++ b/gdb/testsuite/gdb.debuginfod/fetch_src_and_symbols.exp
> > @@ -63,6 +63,11 @@ if { [gdb_compile "$sourcetmp" "$binfile" executable {debug}] != "" } {
> >      return -1
> >  }
> >
> > +if { [gdb_compile "$sourcetmp" "${binfile}2" executable {debug}] != "" } {
> > +    fail "compile"
> > +    return -1
> > +}
> > +
> >  # Write some assembly that just has a .gnu_debugaltlink section.
> >  # Copied from testsuite/gdb.dwarf2/dwzbuildid.exp.
> >  proc write_just_debugaltlink {filename dwzname buildid} {
> > @@ -114,6 +119,8 @@ proc write_dwarf_file {filename buildid {value 99}} {
> >      }
> >  }
> >
> > +set corefile [standard_output_file "corefile"]
> > +
> >  proc no_url { } {
> >      global binfile outputdir debugdir
> >
> > @@ -167,6 +174,16 @@ proc no_url { } {
> >      gdb_test "file ${binfile}_alt.o" \
> >         ".*could not find '.gnu_debugaltlink'.*" \
> >         "file [file tail ${binfile}_alt.o]"
> > +
> > +    # Generate a core file and test that gdb cannot find the executable
> > +    clean_restart ${binfile}2
> > +    gdb_test "start" "Temporary breakpoint.*"
> > +    gdb_test "generate-core-file $::corefile" "Saved corefile $::corefile" \
> > +       "file [file tail $::corefile] gen"
> > +    file rename -force ${binfile}2 $debugdir
> > +
> > +    clean_restart
> > +    gdb_test "core $::corefile" ".*in ?? ().*" "file [file tail $::corefile]"
> >  }
> >
> >  proc local_url { } {
> > @@ -234,6 +251,11 @@ proc local_url { } {
> >      gdb_test "br main" "Breakpoint 1 at.*file.*"
> >      gdb_test "l" ".*This program is distributed in the hope.*"
> >
> > +    # gdb should now find the executable file
> > +    clean_restart
> > +    gdb_test "core $::corefile" ".*return 0.*" "file [file tail $::corefile]" \
> > +       "Enable debuginfod?.*" "y"
> > +
> >      # gdb should now find the debugaltlink file
> >      clean_restart
> >      gdb_test "file ${binfile}_alt.o" \
> > --
> > 2.31.1
> >