[PING][PATCH 4/4 v6] gdb/debuginfod: Add .debug_line downloading

[Aaron Merey <amerey@redhat.com>]

Ping,

Thanks,
Aaron

On Wed, Jan 17, 2024 at 10:49 AM Aaron Merey <amerey@redhat.com> wrote:
>
> v6 adds a testcase for downloads during autocompletion.  It also
> implements the suggestions from Thiago's review:
> https://sourceware.org/pipermail/gdb-patches/2023-December/205507.html
>
> ELF/DWARF section downloading allows gdb to download .gdb_index files in
> order to defer full debuginfo downloads.  However .gdb_index does not
> contain any information regarding source filenames.  When a gdb command
> includes a filename argument (ex. 'break main.c:50'), this results in
> the mass downloading of all deferred debuginfo so that gdb can search the
> debuginfo for matching source filenames.  This can result in unnecessary
> downloads.
>
> To improve this, have gdb instead download each debuginfo's .debug_line
> (and .debug_line_str if using DWARF5) when executing these commands.
> Download full debuginfo only when its .debug_line contains a matching
> filename.
>
> Since the combined size of .debug_line and .debug_line_str is only about
> 1% the size of the corresponding debuginfo, significant time can be saved
> by checking these sections before choosing to download an entire debuginfo.
>
> This patch also redirects stdout and stderr of the debuginfod server
> used by testsuite/gdb.debuginfod tests to a server_log standard output
> file.  While adding tests for this patch I ran into an issue where the
> test server would block when logging to stderr, presumably because the
> stderr buffer filled up and wasn't being read from.  Redirecting the
> log to a file fixes this and also makes the server log more accessible
> when debugging test failures.
> ---
>  gdb/cli-out.c                            |  11 +-
>  gdb/completer.c                          |  18 +-
>  gdb/dwarf2/line-header.c                 | 161 ++++++++++++------
>  gdb/dwarf2/line-header.h                 |  10 ++
>  gdb/dwarf2/read-gdb-index.c              |  60 +++++++
>  gdb/dwarf2/read.c                        | 208 +++++++++++++++++++++++
>  gdb/dwarf2/read.h                        |  37 ++++
>  gdb/mi/mi-out.c                          |   9 +-
>  gdb/testsuite/gdb.debuginfod/section.exp |  27 +++
>  gdb/ui-out.c                             |   3 +
>  gdb/ui-out.h                             |  20 +++
>  11 files changed, 511 insertions(+), 53 deletions(-)
>
> diff --git a/gdb/cli-out.c b/gdb/cli-out.c
> index b4c7a657423..79f61eed62c 100644
> --- a/gdb/cli-out.c
> +++ b/gdb/cli-out.c
> @@ -307,16 +307,23 @@ cli_ui_out::do_progress_notify (const std::string &msg,
>
>    if (info.state == progress_update::START)
>      {
> +      std::string prefix;
> +      if (cur_prefix_state == prefix_state_t::NEWLINE_NEEDED)
> +       {
> +         prefix = "\n";
> +         cur_prefix_state = prefix_state_t::NEWLINE_PRINTED;
> +       }
> +
>        if (stream->isatty ()
>           && current_ui->input_interactive_p ()
>           && chars_per_line >= MIN_CHARS_PER_LINE)
>         {
> -         gdb_printf (stream, "%s\n", msg.c_str ());
> +         gdb_printf (stream, "%s\n", (prefix + msg).c_str ());
>           info.state = progress_update::BAR;
>         }
>        else
>         {
> -         gdb_printf (stream, "%s...\n", msg.c_str ());
> +         gdb_printf (stream, "%s...\n", (prefix + msg).c_str ());
>           info.state = progress_update::WORKING;
>         }
>      }
> diff --git a/gdb/completer.c b/gdb/completer.c
> index 8e2f031f13a..6d453d0d197 100644
> --- a/gdb/completer.c
> +++ b/gdb/completer.c
> @@ -1362,6 +1362,10 @@ complete_line_internal_1 (completion_tracker &tracker,
>      {
>        /* We've recognized a full command.  */
>
> +      /* Disable pagination since responding to the pagination prompt
> +        overwrites rl_line_buffer.  */
> +      scoped_restore pag_restore = make_scoped_restore (&pagination_enabled, false);
> +
>        if (p == tmp_command + point)
>         {
>           /* There is no non-whitespace in the line beyond the
> @@ -1461,7 +1465,8 @@ complete_line_internal_1 (completion_tracker &tracker,
>  }
>
>  /* Wrapper around complete_line_internal_1 to handle
> -   MAX_COMPLETIONS_REACHED_ERROR.  */
> +   MAX_COMPLETIONS_REACHED_ERROR and possible progress update
> +   interactions.  */
>
>  static void
>  complete_line_internal (completion_tracker &tracker,
> @@ -1469,6 +1474,11 @@ complete_line_internal (completion_tracker &tracker,
>                         const char *line_buffer, int point,
>                         complete_line_internal_reason reason)
>  {
> +  scoped_restore restore_prefix_state
> +    = make_scoped_restore
> +      (&cur_prefix_state,
> +       ui_out::progress_update::prefix_state::NEWLINE_NEEDED);
> +
>    try
>      {
>        complete_line_internal_1 (tracker, text, line_buffer, point, reason);
> @@ -1478,6 +1488,12 @@ complete_line_internal (completion_tracker &tracker,
>        if (except.error != MAX_COMPLETIONS_REACHED_ERROR)
>         throw;
>      }
> +
> +  /* If progress update messages printed, then the text being completed
> +     needs to be printed again.  */
> +  if (cur_prefix_state
> +      == ui_out::progress_update::prefix_state::NEWLINE_PRINTED)
> +    rl_forced_update_display ();
>  }
>
>  /* See completer.h.  */
> diff --git a/gdb/dwarf2/line-header.c b/gdb/dwarf2/line-header.c
> index ddaf7e4a527..aec02b3e1f7 100644
> --- a/gdb/dwarf2/line-header.c
> +++ b/gdb/dwarf2/line-header.c
> @@ -102,12 +102,15 @@ read_checked_initial_length_and_offset (bfd *abfd, const gdb_byte *buf,
>  {
>    LONGEST length = read_initial_length (abfd, buf, bytes_read);
>
> -  gdb_assert (cu_header->initial_length_size == 4
> -             || cu_header->initial_length_size == 8
> -             || cu_header->initial_length_size == 12);
> +  if (cu_header != nullptr)
> +    {
> +      gdb_assert (cu_header->initial_length_size == 4
> +                 || cu_header->initial_length_size == 8
> +                 || cu_header->initial_length_size == 12);
>
> -  if (cu_header->initial_length_size != *bytes_read)
> -    complaint (_("intermixed 32-bit and 64-bit DWARF sections"));
> +      if (cu_header->initial_length_size != *bytes_read)
> +       complaint (_("intermixed 32-bit and 64-bit DWARF sections"));
> +    }
>
>    *offset_size = (*bytes_read == 4) ? 4 : 8;
>    return length;
> @@ -116,21 +119,27 @@ read_checked_initial_length_and_offset (bfd *abfd, const gdb_byte *buf,
>  /* Read directory or file name entry format, starting with byte of
>     format count entries, ULEB128 pairs of entry formats, ULEB128 of
>     entries count and the entries themselves in the described entry
> -   format.  */
> +   format.
> +
> +   .debug_line and .debug_line_str sections are stored in LINE_BUFP
> +   and LINE_STR_DATA respectively.  */
>
>  static void
> -read_formatted_entries (dwarf2_per_objfile *per_objfile, bfd *abfd,
> -                       const gdb_byte **bufp, struct line_header *lh,
> -                       unsigned int offset_size,
> -                       void (*callback) (struct line_header *lh,
> -                                         const char *name,
> -                                         dir_index d_index,
> -                                         unsigned int mod_time,
> -                                         unsigned int length))
> +read_formatted_entries
> +  (bfd *abfd, const gdb_byte **line_bufp,
> +   const gdb::array_view<const gdb_byte> line_str_data,
> +   struct line_header *lh,
> +   unsigned int offset_size,
> +   void (*callback) (struct line_header *lh,
> +                    const char *name,
> +                    dir_index d_index,
> +                    unsigned int mod_time,
> +                    unsigned int length))
>  {
>    gdb_byte format_count, formati;
>    ULONGEST data_count, datai;
> -  const gdb_byte *buf = *bufp;
> +  const gdb_byte *buf = *line_bufp;
> +  const gdb_byte *str_buf = line_str_data.data ();
>    const gdb_byte *format_header_data;
>    unsigned int bytes_read;
>
> @@ -157,7 +166,7 @@ read_formatted_entries (dwarf2_per_objfile *per_objfile, bfd *abfd,
>           ULONGEST content_type = read_unsigned_leb128 (abfd, format, &bytes_read);
>           format += bytes_read;
>
> -         ULONGEST form  = read_unsigned_leb128 (abfd, format, &bytes_read);
> +         ULONGEST form = read_unsigned_leb128 (abfd, format, &bytes_read);
>           format += bytes_read;
>
>           std::optional<const char *> string;
> @@ -172,12 +181,24 @@ read_formatted_entries (dwarf2_per_objfile *per_objfile, bfd *abfd,
>
>             case DW_FORM_line_strp:
>               {
> -               const char *str
> -                 = per_objfile->read_line_string (buf, offset_size);
> +               if (line_str_data.empty ())
> +                 warning (_("Dwarf Error: DW_FORM_line_strp used without " \
> +                            "required section"));
> +
> +               if (line_str_data.size () <= offset_size)
> +                 warning (_("Dwarf Error: DW_FORM_line_strp pointing outside " \
> +                            "of section .debug_line_str"));
> +
> +               ULONGEST str_offset = read_offset (abfd, buf, offset_size);
> +               const char *str;
> +               if (str_buf[str_offset] == '\0')
> +                 str = nullptr;
> +               else
> +                 str = (const char *) (str_buf + str_offset);
>                 string.emplace (str);
>                 buf += offset_size;
> +               break;
>               }
> -             break;
>
>             case DW_FORM_data1:
>               uint.emplace (read_1_byte (abfd, buf));
> @@ -248,28 +269,30 @@ read_formatted_entries (dwarf2_per_objfile *per_objfile, bfd *abfd,
>        callback (lh, fe.name, fe.d_index, fe.mod_time, fe.length);
>      }
>
> -  *bufp = buf;
> +  *line_bufp = buf;
>  }
>
>  /* See line-header.h.  */
>
>  line_header_up
> -dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
> -                          dwarf2_per_objfile *per_objfile,
> -                          struct dwarf2_section_info *section,
> -                          const struct comp_unit_head *cu_header,
> -                          const char *comp_dir)
> +dwarf_decode_line_header (bfd *abfd,
> +                         gdb::array_view<const gdb_byte> line_data,
> +                         gdb::array_view<const gdb_byte> line_str_data,
> +                         const gdb_byte **debug_line_ptr,
> +                         bool is_dwz,
> +                         const struct comp_unit_head *cu_header,
> +                         const char *comp_dir)
>  {
> -  const gdb_byte *line_ptr;
> +  const gdb_byte *line_ptr, *buf;
>    unsigned int bytes_read, offset_size;
>    int i;
>    const char *cur_dir, *cur_file;
>
> -  bfd *abfd = section->get_bfd_owner ();
> +  buf = *debug_line_ptr;
>
>    /* Make sure that at least there's room for the total_length field.
>       That could be 12 bytes long, but we're just going to fudge that.  */
> -  if (to_underlying (sect_off) + 4 >= section->size)
> +  if (buf + 4 >= line_data.data () + line_data.size ())
>      {
>        dwarf2_statement_list_fits_in_line_number_section_complaint ();
>        return 0;
> @@ -277,24 +300,26 @@ dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
>
>    line_header_up lh (new line_header (comp_dir));
>
> -  lh->sect_off = sect_off;
> +  lh->sect_off = (sect_offset) (buf - line_data.data ());
>    lh->offset_in_dwz = is_dwz;
>
> -  line_ptr = section->buffer + to_underlying (sect_off);
> +  line_ptr = buf;
>
>    /* Read in the header.  */
>    LONGEST unit_length
> -    = read_checked_initial_length_and_offset (abfd, line_ptr, cu_header,
> +    = read_checked_initial_length_and_offset (abfd, buf, cu_header,
>                                               &bytes_read, &offset_size);
> -  line_ptr += bytes_read;
>
> -  const gdb_byte *start_here = line_ptr;
> +  line_ptr += bytes_read;
>
> -  if (line_ptr + unit_length > (section->buffer + section->size))
> +  if (line_ptr + unit_length > buf + line_data.size ())
>      {
>        dwarf2_statement_list_fits_in_line_number_section_complaint ();
>        return 0;
>      }
> +
> +  const gdb_byte *start_here = line_ptr;
> +
>    lh->statement_program_end = start_here + unit_length;
>    lh->version = read_2_bytes (abfd, line_ptr);
>    line_ptr += 2;
> @@ -303,7 +328,7 @@ dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
>        /* This is a version we don't understand.  The format could have
>          changed in ways we don't handle properly so just punt.  */
>        complaint (_("unsupported version in .debug_line section"));
> -      return NULL;
> +      return nullptr;
>      }
>    if (lh->version >= 5)
>      {
> @@ -320,13 +345,14 @@ dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
>           complaint (_("unsupported segment selector size %u "
>                        "in .debug_line section"),
>                      segment_selector_size);
> -         return NULL;
> +         return nullptr;
>         }
>      }
>
>    LONGEST header_length = read_offset (abfd, line_ptr, offset_size);
>    line_ptr += offset_size;
>    lh->statement_program_start = line_ptr + header_length;
> +
>    lh->minimum_instruction_length = read_1_byte (abfd, line_ptr);
>    line_ptr += 1;
>
> @@ -347,12 +373,16 @@ dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
>
>    lh->default_is_stmt = read_1_byte (abfd, line_ptr);
>    line_ptr += 1;
> +
>    lh->line_base = read_1_signed_byte (abfd, line_ptr);
>    line_ptr += 1;
> +
>    lh->line_range = read_1_byte (abfd, line_ptr);
>    line_ptr += 1;
> +
>    lh->opcode_base = read_1_byte (abfd, line_ptr);
>    line_ptr += 1;
> +
>    lh->standard_opcode_lengths.reset (new unsigned char[lh->opcode_base]);
>
>    lh->standard_opcode_lengths[0] = 1;  /* This should never be used anyway.  */
> @@ -365,21 +395,23 @@ dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
>    if (lh->version >= 5)
>      {
>        /* Read directory table.  */
> -      read_formatted_entries (per_objfile, abfd, &line_ptr, lh.get (),
> -                             offset_size,
> -                             [] (struct line_header *header, const char *name,
> -                                 dir_index d_index, unsigned int mod_time,
> -                                 unsigned int length)
> +      read_formatted_entries
> +       (abfd, &line_ptr, line_str_data,
> +        lh.get (), offset_size,
> +        [] (struct line_header *header, const char *name,
> +            dir_index d_index, unsigned int mod_time,
> +            unsigned int length)
>         {
>           header->add_include_dir (name);
>         });
>
>        /* Read file name table.  */
> -      read_formatted_entries (per_objfile, abfd, &line_ptr, lh.get (),
> -                             offset_size,
> -                             [] (struct line_header *header, const char *name,
> -                                 dir_index d_index, unsigned int mod_time,
> -                                 unsigned int length)
> +      read_formatted_entries
> +       (abfd, &line_ptr, line_str_data,
> +        lh.get (), offset_size,
> +        [] (struct line_header *header, const char *name,
> +            dir_index d_index, unsigned int mod_time,
> +            unsigned int length)
>         {
>           header->add_file_name (name, d_index, mod_time, length);
>         });
> @@ -387,7 +419,7 @@ dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
>    else
>      {
>        /* Read directory table.  */
> -      while ((cur_dir = read_direct_string (abfd, line_ptr, &bytes_read)) != NULL)
> +      while ((cur_dir = read_direct_string (abfd, line_ptr, &bytes_read)) != nullptr)
>         {
>           line_ptr += bytes_read;
>           lh->add_include_dir (cur_dir);
> @@ -395,7 +427,7 @@ dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
>        line_ptr += bytes_read;
>
>        /* Read file name table.  */
> -      while ((cur_file = read_direct_string (abfd, line_ptr, &bytes_read)) != NULL)
> +      while ((cur_file = read_direct_string (abfd, line_ptr, &bytes_read)) != nullptr)
>         {
>           unsigned int mod_time, length;
>           dir_index d_index;
> @@ -413,9 +445,40 @@ dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
>        line_ptr += bytes_read;
>      }
>
> -  if (line_ptr > (section->buffer + section->size))
> +  if (line_ptr > (buf + line_data.size ()))
>      complaint (_("line number info header doesn't "
>                  "fit in `.debug_line' section"));
>
> +  *debug_line_ptr += unit_length + offset_size;
>    return lh;
>  }
> +
> +line_header_up
> +dwarf_decode_line_header  (sect_offset sect_off, bool is_dwz,
> +                          dwarf2_per_objfile *per_objfile,
> +                          struct dwarf2_section_info *section,
> +                          const struct comp_unit_head *cu_header,
> +                          const char *comp_dir)
> +{
> +  struct objfile *objfile = per_objfile->objfile;
> +  struct dwarf2_per_bfd *per_bfd = per_objfile->per_bfd;
> +
> +  /* Read .debug_line.  */
> +  dwarf2_section_info *line_sec = &per_bfd->line;
> +  bfd_size_type line_size = line_sec->get_size (objfile);
> +
> +  gdb::array_view<const gdb_byte> line (line_sec->buffer, line_size);
> +
> +  /* Read .debug_line_str.  */
> +  dwarf2_section_info *line_str_sec = &per_bfd->line_str;
> +  bfd_size_type line_str_size = line_str_sec->get_size (objfile);
> +
> +  gdb::array_view<const gdb_byte> line_str (line_str_sec->buffer,
> +                                           line_str_size);
> +
> +  const gdb_byte *line_ptr = line.data () + to_underlying (sect_off);
> +
> +  return dwarf_decode_line_header
> +    (per_bfd->obfd, line, line_str, &line_ptr,
> +     is_dwz, cu_header, comp_dir);
> +}
> diff --git a/gdb/dwarf2/line-header.h b/gdb/dwarf2/line-header.h
> index 06d2eec573b..1dffb7c7e5e 100644
> --- a/gdb/dwarf2/line-header.h
> +++ b/gdb/dwarf2/line-header.h
> @@ -217,4 +217,14 @@ extern line_header_up dwarf_decode_line_header
>     struct dwarf2_section_info *section, const struct comp_unit_head *cu_header,
>     const char *comp_dir);
>
> +/* Like above but the .debug_line and .debug_line_str are stored in
> +   LINE_DATA and LINE_STR_DATA.  *DEBUG_LINE_PTR should point to a
> +   statement program header within LINE_DATA.  */
> +
> +extern line_header_up dwarf_decode_line_header
> +  (bfd *abfd, gdb::array_view<const gdb_byte> line_data,
> +   gdb::array_view<const gdb_byte> line_str_data,
> +   const gdb_byte **debug_line_ptr, bool is_dwz,
> +  const comp_unit_head *cu_header, const char *comp_dir);
> +
>  #endif /* DWARF2_LINE_HEADER_H */
> diff --git a/gdb/dwarf2/read-gdb-index.c b/gdb/dwarf2/read-gdb-index.c
> index 55b04391eb5..3d75678d7dc 100644
> --- a/gdb/dwarf2/read-gdb-index.c
> +++ b/gdb/dwarf2/read-gdb-index.c
> @@ -131,6 +131,9 @@ struct mapped_gdb_index final : public mapped_index_base
>    }
>  };
>
> +struct mapped_debug_line;
> +typedef std::unique_ptr<mapped_debug_line> mapped_debug_line_up;
> +
>  struct dwarf2_gdb_index : public dwarf2_base_index_functions
>  {
>    /* This dumps minimal information about the index.
> @@ -162,6 +165,15 @@ struct dwarf2_gdb_index : public dwarf2_base_index_functions
>       domain_enum domain,
>       enum search_domain kind);
>
> + /* If OBJFILE's debuginfo download has been deferred, use a mapped_debug_line
> +    to generate filenames.
> +
> +    Otherwise call dwarf2_base_index_functions::map_symbol_filenames.  */
> +
> +  void map_symbol_filenames (struct objfile *objfile,
> +                            gdb::function_view<symbol_filename_ftype> fun,
> +                            bool need_fullname) override;
> +
>    /* Calls dwarf2_base_index_functions::expand_all_symtabs and downloads
>       debuginfo if necessary.  */
>    void expand_all_symtabs (struct objfile *objfile) override;
> @@ -169,6 +181,15 @@ struct dwarf2_gdb_index : public dwarf2_base_index_functions
>    /* Calls dwarf2_base_index_functions::find_last_source_symtab and downloads
>       debuginfo if necessary.  */
>    struct symtab *find_last_source_symtab (struct objfile *objfile) override;
> +
> +  /* Filename information related to this .gdb_index.  */
> +  mapped_debug_line_up mdl;
> +
> +  /* Return true if any of the filenames in this .gdb_index's .debug_line
> +     mapping match FILE_MATCHER.  Initializes the mapping if necessary.  */
> +  bool filename_in_debug_line
> +    (objfile *objfile,
> +     gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher);
>  };
>
>  void
> @@ -204,6 +225,30 @@ dwarf2_gdb_index::find_last_source_symtab (struct objfile *objfile)
>      }
>  }
>
> +void
> +dwarf2_gdb_index::map_symbol_filenames
> +     (struct objfile *objfile,
> +      gdb::function_view<symbol_filename_ftype> fun,
> +      bool need_fullname)
> +{
> +  try
> +    {
> +      dwarf2_base_index_functions::map_symbol_filenames (objfile, fun,
> +                                                        need_fullname);
> +    }
> +  catch (const gdb_exception &e)
> +    {
> +      if ((objfile->flags & OBJF_DOWNLOAD_DEFERRED) == 0)
> +       exception_print (gdb_stderr, e);
> +      else
> +       {
> +         if (mdl == nullptr)
> +           mdl.reset (new mapped_debug_line (objfile));
> +         mdl->map_filenames (fun, need_fullname);
> +       }
> +    }
> +}
> +
>  /* This dumps minimal information about the index.
>     It is called via "mt print objfiles".
>     One use is to verify .gdb_index has been loaded by the
> @@ -371,6 +416,17 @@ dwarf2_gdb_index::do_expand_symtabs_matching
>    return result;
>  }
>
> +bool
> +dwarf2_gdb_index::filename_in_debug_line
> +  (objfile *objfile,
> +   gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher)
> +{
> +  if (mdl == nullptr)
> +    mdl.reset (new mapped_debug_line (objfile));
> +
> +  return mdl->contains_matching_filename (file_matcher);
> +}
> +
>  bool
>  dwarf2_gdb_index::expand_symtabs_matching
>      (struct objfile *objfile,
> @@ -399,6 +455,10 @@ dwarf2_gdb_index::expand_symtabs_matching
>           return false;
>         }
>
> +      if (file_matcher != nullptr
> +         && !filename_in_debug_line (objfile, file_matcher))
> +       return true;
> +
>        read_full_dwarf_from_debuginfod (objfile, this);
>        return true;
>      }
> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
> index 8725a2fbcdb..4af83728c63 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -82,6 +82,7 @@
>  #include <optional>
>  #include "gdbsupport/underlying.h"
>  #include "gdbsupport/hash_enum.h"
> +#include "gdbsupport/scoped_mmap.h"
>  #include "filename-seen-cache.h"
>  #include "producer.h"
>  #include <fcntl.h>
> @@ -1950,6 +1951,213 @@ dw2_get_file_names (dwarf2_per_cu_data *this_cu,
>    return this_cu->file_names;
>  }
>
> +#if !HAVE_SYS_MMAN_H
> +
> +bool
> +mapped_debug_line::contains_matching_filename
> +  (gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher)
> +{
> +  return false;
> +}
> +
> +gdb::array_view<const gdb_byte>
> +mapped_debug_line::read_debug_line_separate
> +  (const char *filename, std::unique_ptr<index_cache_resource> *resource)
> +{
> +  return {};
> +}
> +
> +bool
> +mapped_debug_line::read_debug_line_from_debuginfod (objfile *objfile)
> +{
> +  return false;
> +}
> +
> +void
> +mapped_debug_line::map_filenames
> +  (gdb::function_view<symbol_filename_ftype> fun,
> +   bool need_fullname)
> +{
> +  return;
> +}
> +
> +#else /* !HAVE_SYS_MMAN_H */
> +
> +struct line_resource_mmap final : public index_cache_resource
> +{
> +  /* Try to mmap FILENAME.  Throw an exception on failure, including if the
> +     file doesn't exist.  */
> +  line_resource_mmap (const char *filename)
> +    : mapping (mmap_file (filename))
> +  {}
> +
> +  scoped_mmap mapping;
> +};
> +
> +/* See read.h.  */
> +
> +bool
> +mapped_debug_line::contains_matching_filename
> +  (gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher)
> +{
> +  for (line_header_up &lh : line_headers)
> +    for (file_entry &fe : lh->file_names ())
> +      {
> +       const char *filename = fe.name;
> +
> +       if (file_matcher (fe.name, false))
> +         return true;
> +
> +       bool basename_match = file_matcher (lbasename (fe.name), true);
> +
> +       if (!basenames_may_differ && !basename_match)
> +         continue;
> +
> +       /* DW_AT_comp_dir is not explicitly mentioned in the .debug_line
> +          until DWARF5.  Since we don't have access to the CU at this
> +          point we just check for a partial match on the filename.
> +          If there is a match, the full debuginfo will be downloaded
> +          ane the match will be re-evalute with DW_AT_comp_dir.  */
> +       if (lh->version < 5 && fe.d_index == 0)
> +         return basename_match;
> +
> +       const char *dirname = fe.include_dir (&*lh);
> +       std::string fullname;
> +
> +       if (dirname == nullptr || IS_ABSOLUTE_PATH (filename))
> +         fullname = filename;
> +       else
> +         fullname = std::string (dirname) + SLASH_STRING + filename;
> +
> +       gdb::unique_xmalloc_ptr<char> rewritten
> +         = rewrite_source_path (fullname.c_str ());
> +       if (rewritten != nullptr)
> +         fullname = rewritten.release ();
> +
> +       if (file_matcher (fullname.c_str (), false))
> +         return true;
> +      }
> +
> +  return false;
> +}
> +
> +/* See read.h.  */
> +
> +void
> +mapped_debug_line::map_filenames
> +  (gdb::function_view<symbol_filename_ftype> fun,
> +   bool need_fullname)
> +{
> +  for (line_header_up &lh : line_headers)
> +    for (file_entry &fe : lh->file_names ())
> +      {
> +       const char *filename = fe.name;
> +
> +       if (!need_fullname)
> +         {
> +           fun (filename, nullptr);
> +           continue;
> +         }
> +
> +       const char *dirname = fe.include_dir (&*lh);
> +       std::string fullname;
> +
> +       if (dirname == nullptr || IS_ABSOLUTE_PATH (filename))
> +         fullname = filename;
> +       else
> +         fullname = std::string (dirname) + SLASH_STRING + filename;
> +
> +       gdb::unique_xmalloc_ptr<char> rewritten
> +         = rewrite_source_path (fullname.c_str ());
> +       if (rewritten != nullptr)
> +         fullname = rewritten.release ();
> +
> +       fun (filename, fullname.c_str ());
> +      }
> +}
> +
> +/* See read.h.  */
> +
> +gdb::array_view<const gdb_byte>
> +mapped_debug_line::read_debug_line_separate
> +  (const char *filename, std::unique_ptr<index_cache_resource> *resource)
> +{
> +  if (filename == nullptr)
> +    return {};
> +
> +  try
> +  {
> +    line_resource_mmap *mmap_resource
> +      = new line_resource_mmap (filename);
> +
> +    resource->reset (mmap_resource);
> +
> +    return gdb::array_view<const gdb_byte>
> +      ((const gdb_byte *) mmap_resource->mapping.get (),
> +       mmap_resource->mapping.size ());
> +  }
> +  catch (const gdb_exception &except)
> +  {
> +    exception_print (gdb_stderr, except);
> +  }
> +
> +  return {};
> +}
> +
> +/* See read.h.  */
> +
> +bool
> +mapped_debug_line::read_debug_line_from_debuginfod (objfile *objfile)
> +{
> +  const bfd_build_id *build_id = build_id_bfd_get (objfile->obfd.get ());
> +  if (build_id == nullptr)
> +    return false;
> +
> +  gdb::unique_xmalloc_ptr<char> line_path;
> +  scoped_fd line_fd = debuginfod_section_query (build_id->data,
> +                                               build_id->size,
> +                                               bfd_get_filename
> +                                                 (objfile->obfd.get ()),
> +                                               ".debug_line",
> +                                               &line_path);
> +
> +  if (line_fd.get () < 0)
> +    return false;
> +
> +  gdb::unique_xmalloc_ptr<char> line_str_path;
> +  scoped_fd line_str_fd = debuginfod_section_query (build_id->data,
> +                                                   build_id->size,
> +                                                   bfd_get_filename
> +                                                     (objfile->obfd.get ()),
> +                                                   ".debug_line_str",
> +                                                   &line_str_path);
> +
> +  line_data = read_debug_line_separate (line_path.get (), &line_resource);
> +  line_str_data = read_debug_line_separate (line_str_path.get (),
> +                                           &line_str_resource);
> +
> +  const gdb_byte *line_ptr = line_data.data ();
> +
> +  while (line_ptr < line_data.data () + line_data.size ())
> +    {
> +      line_header_up lh
> +       = dwarf_decode_line_header (objfile->obfd.get (),
> +                                   line_data, line_str_data,
> +                                   &line_ptr, false,
> +                                   nullptr, nullptr);
> +      line_headers.emplace_back (std::move (lh));
> +    }
> +
> +  return true;
> +}
> +#endif /* !HAVE_SYS_MMAN_H */
> +
> +mapped_debug_line::mapped_debug_line (objfile *objfile)
> +{
> +  if (!read_debug_line_from_debuginfod (objfile))
> +    line_headers.clear ();
> +}
> +
>  /* A helper for the "quick" functions which computes and caches the
>     real path for a given file name from the line table.  */
>
> diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h
> index 8b6f1864458..db16160b43e 100644
> --- a/gdb/dwarf2/read.h
> +++ b/gdb/dwarf2/read.h
> @@ -33,6 +33,7 @@
>  #include "gdbsupport/hash_enum.h"
>  #include "gdbsupport/function-view.h"
>  #include "gdbsupport/packed.h"
> +#include "dwarf2/line-header.h"
>
>  /* Hold 'maintenance (set|show) dwarf' commands.  */
>  extern struct cmd_list_element *set_dwarf_cmdlist;
> @@ -982,4 +983,40 @@ extern htab_up create_quick_file_names_table (unsigned int nr_initial_entries);
>  extern void read_full_dwarf_from_debuginfod (struct objfile *,
>                                              dwarf2_base_index_functions *);
>
> +struct mapped_debug_line
> +{
> +  mapped_debug_line (objfile *objfile);
> +
> +  /* Return true if any of the mapped .debug_line's filenames match
> +     FILE_MATCHER.  */
> +
> +  bool contains_matching_filename
> +    (gdb::function_view<expand_symtabs_file_matcher_ftype> file_matcher);
> +
> +  /* Call FUN with each filename in this mapped .debug_line.  Include
> +     each file's fullname if NEED_FULLNAME is true.  */
> +
> +  void map_filenames (gdb::function_view<symbol_filename_ftype> fun,
> +                     bool need_fullname);
> +
> +private:
> +  std::vector<line_header_up> line_headers;
> +
> +  gdb::array_view<const gdb_byte> line_data;
> +  gdb::array_view<const gdb_byte> line_str_data;
> +
> +  std::unique_ptr<index_cache_resource> line_resource;
> +  std::unique_ptr<index_cache_resource> line_str_resource;
> +
> +  /* Download the .debug_line and .debug_line_str associated with OBJFILE
> +     and populate line_headers.  */
> +
> +  bool read_debug_line_from_debuginfod (objfile *objfile);
> +
> +  /* Initialize line_data and line_str_data with the .debug_line and
> +    .debug_line_str downloaded read_debug_line_from_debuginfod.  */
> +
> +  gdb::array_view<const gdb_byte> read_debug_line_separate
> +    (const char *filename, std::unique_ptr<index_cache_resource> *resource);
> +};
>  #endif /* DWARF2READ_H */
> diff --git a/gdb/mi/mi-out.c b/gdb/mi/mi-out.c
> index 0bc13f963bc..ab955a0fc05 100644
> --- a/gdb/mi/mi-out.c
> +++ b/gdb/mi/mi-out.c
> @@ -278,7 +278,14 @@ mi_ui_out::do_progress_notify (const std::string &msg, const char *unit,
>
>    if (info.state == progress_update::START)
>      {
> -      gdb_printf ("%s...\n", msg.c_str ());
> +      std::string prefix;
> +      if (cur_prefix_state == prefix_state_t::NEWLINE_NEEDED)
> +       {
> +         prefix = "\n";
> +         cur_prefix_state = prefix_state_t::NEWLINE_PRINTED;
> +       }
> +
> +      gdb_printf ("%s...\n", (prefix + msg).c_str ());
>        info.state = progress_update::WORKING;
>      }
>  }
> diff --git a/gdb/testsuite/gdb.debuginfod/section.exp b/gdb/testsuite/gdb.debuginfod/section.exp
> index c3872ecdfc9..3ac11152daa 100644
> --- a/gdb/testsuite/gdb.debuginfod/section.exp
> +++ b/gdb/testsuite/gdb.debuginfod/section.exp
> @@ -18,6 +18,7 @@
>  standard_testfile
>
>  load_lib debuginfod-support.exp
> +load_lib completion-support.exp
>
>  require allow_debuginfod_tests
>
> @@ -159,6 +160,32 @@ proc_with_prefix local_url { } {
>      # Hit the breakpoint.
>      set res ".*Breakpoint 2, libsection2_test.*\"In ${libfile2}\\\\n\".*"
>      gdb_test "c" $res "break continue"
> +
> +    clean_restart_with_prompt $sectexec "line 1"
> +
> +    # List source file using .debug_line download.
> +    set res ".*\.debug_line.*$lib_sl1.*21.*extern void libsection2_test.*"
> +    gdb_test "list $libsrc1:21" $res "line 1 list"
> +
> +    clean_restart_with_prompt $sectexec "line 2"
> +
> +    # Set breakpoint using .debug_line download.
> +    set res ".*section \.debug_line for $lib_sl1.*Breakpoint 2 at.*$libsrc1.*"
> +    gdb_test "br $libsrc1:41" $res "line 2 br"
> +
> +    # Continue to breakpoint.
> +    set res "Breakpoint 2, libsection1_test.*\"Cancelling thread\\\\n\".*"
> +    gdb_test "c" $res "line 2 continue"
> +
> +    # Check that download progress message is correctly formatted
> +    # when printing threads.
> +    set res ".*separate debug info for $lib_sl2\.\.\.\r\n.* 2    Thread.*"
> +    gdb_test "info thr" $res "line thread"
> +
> +    clean_restart_with_prompt $sectexec "autocomplete"
> +
> +    # Download debuginfo during autocompletion.
> +    test_gdb_complete_tab_unique "br lib" ".*Downloading separate debug.*" ""
>  }
>
>  # Create CACHE and DB directories ready for debuginfod to use.
> diff --git a/gdb/ui-out.c b/gdb/ui-out.c
> index 75f9f1612cb..d9a620b70e8 100644
> --- a/gdb/ui-out.c
> +++ b/gdb/ui-out.c
> @@ -32,6 +32,9 @@
>  #include <memory>
>  #include <string>
>
> +/* Current state of newline prefixing for progress update messages.  */
> +prefix_state_t cur_prefix_state = prefix_state_t::NEWLINE_OFF;
> +
>  namespace {
>
>  /* A header of a ui_out_table.  */
> diff --git a/gdb/ui-out.h b/gdb/ui-out.h
> index 2934d3a6b34..2c21603f1a7 100644
> --- a/gdb/ui-out.h
> +++ b/gdb/ui-out.h
> @@ -296,6 +296,21 @@ class ui_out
>        BAR
>      };
>
> +    /* Used to communicate the status of a newline prefix for the next progress
> +       update message.  */
> +    enum prefix_state
> +    {
> +      /* Do not modify the next progress update message.  */
> +      NEWLINE_OFF,
> +
> +      /* The next progress update message should include a newline prefix.  */
> +      NEWLINE_NEEDED,
> +
> +      /* A newline prefix was included in a debuginfod progress update
> +        message.  */
> +      NEWLINE_PRINTED
> +    };
> +
>      /* SHOULD_PRINT indicates whether something should be printed for a tty.  */
>      progress_update ()
>      {
> @@ -393,6 +408,11 @@ class ui_out
>    ui_out_level *current_level () const;
>  };
>
> +typedef ui_out::progress_update::prefix_state prefix_state_t;
> +
> +/* Current state of the newline prefix.  */
> +extern prefix_state_t cur_prefix_state;
> +
>  /* Start a new tuple or list on construction, and end it on
>     destruction.  Normally this is used via the typedefs
>     ui_out_emit_tuple and ui_out_emit_list.  */
> --
> 2.43.0
>