From patchwork Wed Nov 29 01:21:39 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergio Durigan Junior X-Patchwork-Id: 24587 Received: (qmail 38195 invoked by alias); 29 Nov 2017 01:21:48 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 38179 invoked by uid 89); 29 Nov 2017 01:21:48 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-25.2 required=5.0 tests=BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, KAM_SHORT, KAM_STOCKGEN, KB_WAM_FROM_NAME_SINGLEWORD, SPF_HELO_PASS, T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 spammy=0o X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 29 Nov 2017 01:21:45 +0000 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id EE87BC049D5F; Wed, 29 Nov 2017 01:21:43 +0000 (UTC) Received: from psique.yyz.redhat.com (unused-10-15-17-193.yyz.redhat.com [10.15.17.193]) by smtp.corp.redhat.com (Postfix) with ESMTP id CB6AC600D5; Wed, 29 Nov 2017 01:21:40 +0000 (UTC) From: Sergio Durigan Junior To: GDB Patches Cc: Joel Brobecker , Yao Qi , Pedro Alves , Eli Zaretskii , Sergio Durigan Junior Subject: [PATCH v3] Add support for the readnever concept Date: Tue, 28 Nov 2017 20:21:39 -0500 Message-Id: <20171129012139.17325-1-sergiodj@redhat.com> In-Reply-To: <1467838463-15786-1-git-send-email-brobecker@adacore.com> References: <1467838463-15786-1-git-send-email-brobecker@adacore.com> X-IsSubscribed: yes Changes from v2: - Fixed a few nits pointed by Eli in the docs. - Implemented Pedro's suggestion and moved the logic of readnever out of the "*_build_psymtabs" and into the elf_symfile_read function. - Handle the propagation of the OBJF_READNEVER flag to the separate debuginfo file. - Reword commit title, fix a few typos in the commit message. The purpose of this concept is to turn the load of debugging information off, either globally (via the '--readnever' option), or objfile-specific. The implementation proposed here is an extension of the patch distributed with Fedora GDB; looking at the Fedora patch itself and the history, one can see some reasons why it was never resubmitted: - The patch appears to have been introduced as a workaround, at least initially; - The patch is far from perfect, as it simply shunts the load of DWARF debugging information, without really worrying about the other debug format. - Who really does non-symbolic debugging anyways? One use of this feature is when a user simply wants to do the following sequence: attach, dump core, detach. Loading the debugging information in this case is an unnecessary cause of delay. This patch expands the version shipped with Fedora GDB in order to make the feature available for all the debuginfo backends, not only for DWARF. It also implements a per-objfile flag which can be activated by using the "-readnever" command when using the 'add-symbol-file' or 'symbol-file' commands. While implementing the code for the 'symbol-file' command, I noticed a bug in 'symbol_file_command': GDB adds the symbol file before finishing parsing all the options, which means that the position of an option in the command impacts whether it will be considered or not. I changed the code there in order to only add the symbol file after all options have been parsed. It's also worth mentioning that this patch tests whether GDB correctly fails to initialize if both '--readnow' and '--readnever' options are passed. We didn't have any infrastructure to test that, so I added a new version of 'gdb_spawn', called 'gdb_spawn_ignore_error', which can be used to start a GDB that will fail without compromising the entire testcase. Tested on the BuildBot. gdb/ChangeLog: 2017-11-28 Andrew Cagney Joel Brobecker Sergio Durigan Junior * NEWS (Changes since GDB 8.0: Mention new '--readnever' feature. * dwarf2read.c: Include "top.h". (dwarf2_has_info): Return 0 if READNEVER_SYMBOL_FILES is set. * elfread.c: Include "top.h". (elf_symfile_read): Do not map over sections with 'elf_locate_sections' if readnever is on. * main.c (validate_readnow_readnever): New function. (captured_main_1): Add support for --readnever. (print_gdb_help): Document --readnever. * objfile-flags.h (enum objfile_flag) : New flag. * symfile.c (readnever_symbol_files): New global. (symbol_file_add_with_addrs): Set 'OBJF_READNEVER' when 'READNEVER_SYMBOL_FILES' is set. (validate_readnow_readnever): New function. (symbol_file_command): Handle '-readnever' option. Move call to 'symbol_file_add_main_1' out of the argument parsing loop. Call 'validate_readnow_readnever'. (add_symbol_file_command): Handle '-readnever' option. Document it. Call 'validate_readnow_readnever'. * top.h (readnever_symbol_files): New extern global. gdb/doc/ChangeLog: 2017-11-28 Andrew Cagney Joel Brobecker Sergio Durigan Junior * gdb.texinfo (File Options): Document --readnever. (Commands to Specify Files): Likewise, for 'symbol-file'. gdb/testsuite/ChangeLog: 2017-11-28 Joel Brobecker Sergio Durigan Junior Pedro Alves * gdb.base/readnever.c, gdb.base/readnever.exp: New files. * lib/gdb.exp (default_gdb_spawn): Add 'ignore_error' parameter. Handle case when 'ignore_error' is set. (gdb_spawn_ignore_error): New function. --- gdb/NEWS | 6 +++ gdb/doc/gdb.texinfo | 17 ++++++++ gdb/dwarf2read.c | 4 ++ gdb/elfread.c | 3 +- gdb/main.c | 37 +++++++++++++++-- gdb/objfile-flags.h | 4 ++ gdb/symfile.c | 33 +++++++++++++--- gdb/testsuite/gdb.base/readnever.c | 43 ++++++++++++++++++++ gdb/testsuite/gdb.base/readnever.exp | 77 ++++++++++++++++++++++++++++++++++++ gdb/testsuite/lib/gdb.exp | 18 ++++++--- gdb/top.h | 1 + 11 files changed, 229 insertions(+), 14 deletions(-) create mode 100644 gdb/testsuite/gdb.base/readnever.c create mode 100644 gdb/testsuite/gdb.base/readnever.exp diff --git a/gdb/NEWS b/gdb/NEWS index 754ce103bd..22502df149 100644 --- a/gdb/NEWS +++ b/gdb/NEWS @@ -3,6 +3,12 @@ *** Changes since GDB 8.0 +* New "--readnever" command line option instructs GDB to not read each + symbol file's symbolic debug information. This makes startup faster + but at the expense of not being able to perform symbolic debugging. + This option is intended for use cases where symbolic debugging will + not be used, e.g., when you only need to dump the debuggee's core. + * GDB now uses the GNU MPFR library, if available, to emulate target floating-point arithmetic during expression evaluation when the target uses different floating-point formats than the host. At least version diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 675f6e7bc8..2aca978d0f 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -1037,6 +1037,15 @@ Read each symbol file's entire symbol table immediately, rather than the default, which is to read it incrementally as it is needed. This makes startup slower, but makes future operations faster. +@item --readnever +@cindex @code{--readnever}, command-line option +Do not read each symbol file's symbolic debug information. This makes +startup faster but at the expense of not being able to perform +symbolic debugging. DWARF unwind information is also not read, +meaning backtraces may become incomplete or inaccurate. One use of +this is when a user simply wants to do the following sequence: attach, +dump core, detach. Loading the debugging information in this case is +an unnecessary cause of delay. @end table @node Mode Options @@ -18492,6 +18501,14 @@ tables by using the @samp{-readnow} option with any of the commands that load symbol table information, if you want to be sure @value{GDBN} has the entire symbol table available. +@cindex @code{-readnever}, option for symbol-file command +@cindex never read symbols +@cindex symbols, never read +@item symbol-file @r{[} -readnever @r{]} @var{filename} +@itemx file @r{[} -readnever @r{]} @var{filename} +You can instruct @value{GDBN} to never read the symbolic information +contained in @var{filename} by using the @samp{-readnever} option. + @c FIXME: for now no mention of directories, since this seems to be in @c flux. 13mar1992 status is that in theory GDB would look either in @c current dir or in same dir as myprog; but issues like competing diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c index 334d8c2e05..0975d2bbe2 100644 --- a/gdb/dwarf2read.c +++ b/gdb/dwarf2read.c @@ -82,6 +82,7 @@ #include #include #include "selftest.h" +#include "top.h" /* When == 1, print basic high level tracing messages. When > 1, be more verbose. @@ -2319,6 +2320,9 @@ int dwarf2_has_info (struct objfile *objfile, const struct dwarf2_debug_sections *names) { + if (readnever_symbol_files || (objfile->flags & OBJF_READNEVER)) + return 0; + dwarf2_per_objfile = ((struct dwarf2_per_objfile *) objfile_data (objfile, dwarf2_objfile_data_key)); if (!dwarf2_per_objfile) diff --git a/gdb/elfread.c b/gdb/elfread.c index f2483025ba..e8b4e2a759 100644 --- a/gdb/elfread.c +++ b/gdb/elfread.c @@ -1171,7 +1171,8 @@ elf_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags) struct elfinfo ei; memset ((char *) &ei, 0, sizeof (ei)); - bfd_map_over_sections (abfd, elf_locate_sections, (void *) & ei); + if (!readnever_symbol_files && !(objfile->flags & OBJF_READNEVER)) + bfd_map_over_sections (abfd, elf_locate_sections, (void *) & ei); elf_read_minimal_symbols (objfile, symfile_flags, &ei); diff --git a/gdb/main.c b/gdb/main.c index 61168faf50..8f04da107a 100644 --- a/gdb/main.c +++ b/gdb/main.c @@ -402,6 +402,19 @@ symbol_file_add_main_adapter (const char *arg, int from_tty) symbol_file_add_main (arg, add_flags); } +/* Perform validation of the '--readnow' and '--readnever' flags. */ + +static void +validate_readnow_readnever () +{ + if (readnever_symbol_files && readnow_symbol_files) + { + error (_("%s: '--readnow' and '--readnever' cannot be " + "specified simultaneously"), + gdb_program_name); + } +} + /* Type of this option. */ enum cmdarg_kind { @@ -579,14 +592,17 @@ captured_main_1 (struct captured_main_args *context) OPT_NOWINDOWS, OPT_WINDOWS, OPT_IX, - OPT_IEX + OPT_IEX, + OPT_READNOW, + OPT_READNEVER }; static struct option long_options[] = { {"tui", no_argument, 0, OPT_TUI}, {"dbx", no_argument, &dbx_commands, 1}, - {"readnow", no_argument, &readnow_symbol_files, 1}, - {"r", no_argument, &readnow_symbol_files, 1}, + {"readnow", no_argument, NULL, OPT_READNOW}, + {"readnever", no_argument, NULL, OPT_READNEVER}, + {"r", no_argument, NULL, OPT_READNOW}, {"quiet", no_argument, &quiet, 1}, {"q", no_argument, &quiet, 1}, {"silent", no_argument, &quiet, 1}, @@ -809,6 +825,20 @@ captured_main_1 (struct captured_main_args *context) } break; + case OPT_READNOW: + { + readnow_symbol_files = 1; + validate_readnow_readnever (); + } + break; + + case OPT_READNEVER: + { + readnever_symbol_files = 1; + validate_readnow_readnever (); + } + break; + case '?': error (_("Use `%s --help' for a complete list of options."), gdb_program_name); @@ -1183,6 +1213,7 @@ Selection of debuggee and its files:\n\n\ --se=FILE Use FILE as symbol file and executable file.\n\ --symbols=SYMFILE Read symbols from SYMFILE.\n\ --readnow Fully read symbol files on first access.\n\ + --readnever Do not read symbol files.\n\ --write Set writing into executable and core files.\n\n\ "), stream); fputs_unfiltered (_("\ diff --git a/gdb/objfile-flags.h b/gdb/objfile-flags.h index 43ba8aaefd..f2a2ccfa8c 100644 --- a/gdb/objfile-flags.h +++ b/gdb/objfile-flags.h @@ -64,6 +64,10 @@ enum objfile_flag unrelated to filesystem names. It can be for example "". */ OBJF_NOT_FILENAME = 1 << 6, + + /* User requested that we do not read this objfile's symbolic + information. */ + OBJF_READNEVER = 1 << 7, }; DEF_ENUM_FLAGS_TYPE (enum objfile_flag, objfile_flags); diff --git a/gdb/symfile.c b/gdb/symfile.c index feb50f8b79..1be4a54024 100644 --- a/gdb/symfile.c +++ b/gdb/symfile.c @@ -81,6 +81,7 @@ static void clear_symtab_users_cleanup (void *ignore); /* Global variables owned by this file. */ int readnow_symbol_files; /* Read full symbols immediately. */ +int readnever_symbol_files; /* Never read full symbols. */ /* Functions this file defines. */ @@ -1131,6 +1132,11 @@ symbol_file_add_with_addrs (bfd *abfd, const char *name, flags |= OBJF_READNOW; add_flags &= ~SYMFILE_NO_READ; } + else if (readnever_symbol_files || (objfile->flags & OBJF_READNEVER)) + { + flags |= OBJF_READNEVER; + add_flags |= SYMFILE_NO_READ; + } /* Give user a chance to burp if we'd be interactively wiping out any existing symbols. */ @@ -1594,6 +1600,16 @@ find_separate_debug_file_by_debuglink (struct objfile *objfile) return debugfile; } +/* Make sure that OBJF_{READNOW,READNEVER} are not set + simultaneously. */ + +static void +validate_readnow_readnever (objfile_flags flags) +{ + if ((flags & OBJF_READNOW) && (flags & OBJF_READNEVER)) + error (_("-readnow and -readnever cannot be used simultaneously")); +} + /* This is the symbol-file command. Read the file, analyze its symbols, and add a struct symtab to a symtab list. The syntax of the command is rather bizarre: @@ -1631,17 +1647,20 @@ symbol_file_command (const char *args, int from_tty) { if (strcmp (arg, "-readnow") == 0) flags |= OBJF_READNOW; + else if (strcmp (arg, "-readnever") == 0) + flags |= OBJF_READNEVER; else if (*arg == '-') error (_("unknown option `%s'"), arg); else - { - symbol_file_add_main_1 (arg, add_flags, flags); - name = arg; - } + name = arg; } if (name == NULL) error (_("no symbol file name was specified")); + + validate_readnow_readnever (flags); + + symbol_file_add_main_1 (name, add_flags, flags); } } @@ -2238,6 +2257,8 @@ add_symbol_file_command (const char *args, int from_tty) } else if (strcmp (arg, "-readnow") == 0) flags |= OBJF_READNOW; + else if (strcmp (arg, "-readnever") == 0) + flags |= OBJF_READNEVER; else if (strcmp (arg, "-s") == 0) { expecting_sec_name = 1; @@ -2245,10 +2266,12 @@ add_symbol_file_command (const char *args, int from_tty) } else error (_("USAGE: add-symbol-file " - " [-readnow] [-s ]*")); + " [-readnow|-readnever] [-s ]*")); } } + validate_readnow_readnever (flags); + /* This command takes at least two arguments. The first one is a filename, and the second is the address where this file has been loaded. Abort now if this address hasn't been provided by the diff --git a/gdb/testsuite/gdb.base/readnever.c b/gdb/testsuite/gdb.base/readnever.c new file mode 100644 index 0000000000..7b2fe1cae4 --- /dev/null +++ b/gdb/testsuite/gdb.base/readnever.c @@ -0,0 +1,43 @@ +/* Copyright 2016-2017 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +#include + +static void +fun_three (int a, char b, void *c) +{ + /* Do nothing. */ +} + +static void +fun_two (unsigned int p, const char *y) +{ + fun_three ((int) p, '1', (void *) y); +} + +static void +fun_one (int *x) +{ + fun_two (10, (const char *) x); +} + +int +main (void) +{ + int a = 10; + + fun_one (&a); + return 0; +} diff --git a/gdb/testsuite/gdb.base/readnever.exp b/gdb/testsuite/gdb.base/readnever.exp new file mode 100644 index 0000000000..a6d48db9b6 --- /dev/null +++ b/gdb/testsuite/gdb.base/readnever.exp @@ -0,0 +1,77 @@ +# Copyright 2016-2017 Free Software Foundation, Inc. + +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program 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 General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . + +standard_testfile .c + +if { [build_executable "failed to build" $testfile $srcfile { debug }] == -1 } { + untested "Couldn't compile ${srcfile}" + return -1 +} + +save_vars { GDBFLAGS } { + append GDBFLAGS " --readnever" + clean_restart ${binfile} +} + +if ![runto_main] then { + perror "couldn't run to breakpoint" + continue +} + +gdb_test "break fun_three" \ + "Breakpoint $decimal at $hex" + +gdb_test "continue" \ + "Breakpoint $decimal, $hex in fun_three \\(\\)" + +gdb_test "backtrace" \ + [multi_line "#0 $hex in fun_three \\(\\)" \ + "#1 $hex in fun_two \\(\\)" \ + "#2 $hex in fun_one \\(\\)" \ + "#3 $hex in main \\(\\)" ] + +gdb_test_no_output "maint info symtabs" \ + "maint info symtabs no output for --readnever" +gdb_test_no_output "maint info psymtabs" \ + "maint info psymtabs no output for --readnever" + +# Test invalid combination of flags. +save_vars { GDBFLAGS } { + append GDBFLAGS " --readnever --readnow" + gdb_exit + gdb_spawn_ignore_error + + set test "test readnow and readnever at the same time" + gdb_test_multiple "" $test { + eof { + pass $test + } + } +} + + +# Test symbol-file's -readnever option. + +# Restart GDB without the --readnever option. +gdb_exit +gdb_start +gdb_test "symbol-file ${binfile}0.o -readnever" \ + "Reading symbols from ${binfile}0\.o\.\.\.\\\(no debugging symbols found\\\)\.\.\.done\." \ + "use symbol-file -readnever" + +gdb_test_no_output "maint info symtabs" \ + "maint info symtabs no output for symbol-file -readnever" +gdb_test_no_output "maint info psymtabs" \ + "maint info psymtabs no output for symbol-file -readnever" diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp index 8d6972ab1f..6a6326344a 100644 --- a/gdb/testsuite/lib/gdb.exp +++ b/gdb/testsuite/lib/gdb.exp @@ -1580,7 +1580,7 @@ proc gdb_file_cmd { arg } { # Default gdb_spawn procedure. -proc default_gdb_spawn { } { +proc default_gdb_spawn { { ignore_error 0 } } { global use_gdb_stub global GDB global INTERNAL_GDBFLAGS GDBFLAGS @@ -1610,11 +1610,12 @@ proc default_gdb_spawn { } { } } set res [remote_spawn host "$GDB $INTERNAL_GDBFLAGS $GDBFLAGS [host_info gdb_opts]"] - if { $res < 0 || $res == "" } { - perror "Spawning $GDB failed." - return 1 + if { !$ignore_error } { + if { $res < 0 || $res == "" } { + perror "Spawning $GDB failed." + return 1 + } } - set gdb_spawn_id $res return 0 } @@ -4077,6 +4078,13 @@ proc gdb_spawn { } { default_gdb_spawn } +# Spawn the gdb process, but ignore errors. This is useful if you +# want GDB to fail, e.g. when testing invalid command line options. + +proc gdb_spawn_ignore_error { } { + default_gdb_spawn 1 +} + # Spawn GDB with CMDLINE_FLAGS appended to the GDBFLAGS global. proc gdb_spawn_with_cmdline_opts { cmdline_flags } { diff --git a/gdb/top.h b/gdb/top.h index 26fe87842f..a1df64f383 100644 --- a/gdb/top.h +++ b/gdb/top.h @@ -267,6 +267,7 @@ extern int gdb_in_secondary_prompt_p (struct ui *ui); /* From random places. */ extern int readnow_symbol_files; +extern int readnever_symbol_files; /* Perform _initialize initialization. */ extern void gdb_init (char *);