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[86.166.129.230]) by smtp.gmail.com with ESMTPSA id w21sm12108758wmi.45.2021.01.08.09.14.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Jan 2021 09:14:00 -0800 (PST) Date: Fri, 8 Jan 2021 17:13:59 +0000 From: Andrew Burgess To: Simon Marchi Subject: Re: [PATCH v2] gdb: check for empty strings in, get_standard_cache_dir/get_standard_config_dir Message-ID: <20210108171359.GA2945@embecosm.com> References: <20210107205725.2010353-1-simon.marchi@efficios.com> <20210108094811.GT2945@embecosm.com> <0ddb71dd-8ff8-ae3b-09bd-96ba46bfdaf1@polymtl.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0ddb71dd-8ff8-ae3b-09bd-96ba46bfdaf1@polymtl.ca> X-Operating-System: Linux/5.8.13-100.fc31.x86_64 (x86_64) X-Uptime: 17:13:35 up 30 days, 21:58, X-Editor: GNU Emacs [ http://www.gnu.org/software/emacs ] X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Simon Marchi , gdb-patches@sourceware.org, sourcewarebugz@kyber.fi Errors-To: gdb-patches-bounces@sourceware.org Sender: "Gdb-patches" * Simon Marchi [2021-01-08 10:50:58 -0500]: > On 2021-01-08 4:48 a.m., Andrew Burgess wrote: > > I wonder if it's worth including the case where ALL of the environment > > variables are empty as well, just to check that there's no issues with > > GDB falling through all the checks? > > I don't know, but it wasn't too difficult so I did it. > > > > > Otherwise, LGTM. > > I also thought it would be a good idea to check that the index-cache > directory value doesn't get affected by these empty values, that we > properly skip over them. See updated patch below. > > > From c010770be40c91b97be5e97ce830abea4efd8f86 Mon Sep 17 00:00:00 2001 > From: Simon Marchi > Date: Fri, 8 Jan 2021 10:47:53 -0500 > Subject: [PATCH v2] gdb: check for empty strings in > get_standard_cache_dir/get_standard_config_dir > > New in v2: > > - Check the value of the index-cache directory before and after. > - Check with all the env vars defined to empty. > > As reported in PR 27157, if some environment variables read at startup > by GDB are defined but empty, we hit the assert in gdb_abspath: > > $ XDG_CACHE_HOME= ./gdb -nx --data-directory=data-directory -q > AddressSanitizer:DEADLYSIGNAL > ================================================================= > ==2007040==ERROR: AddressSanitizer: SEGV on unknown address 0x0000000001b0 (pc 0x5639d4aa4127 bp 0x7ffdac232c00 sp 0x7ffdac232bf0 T0) > ==2007040==The signal is caused by a READ memory access. > ==2007040==Hint: address points to the zero page. > #0 0x5639d4aa4126 in target_stack::top() const /home/smarchi/src/binutils-gdb/gdb/target.h:1334 > #1 0x5639d4aa41f1 in inferior::top_target() /home/smarchi/src/binutils-gdb/gdb/inferior.h:369 > #2 0x5639d4a70b1f in current_top_target() /home/smarchi/src/binutils-gdb/gdb/target.c:120 > #3 0x5639d4b00591 in gdb_readline_wrapper_cleanup::gdb_readline_wrapper_cleanup() /home/smarchi/src/binutils-gdb/gdb/top.c:1046 > #4 0x5639d4afab31 in gdb_readline_wrapper(char const*) /home/smarchi/src/binutils-gdb/gdb/top.c:1104 > #5 0x5639d4ccce2c in defaulted_query /home/smarchi/src/binutils-gdb/gdb/utils.c:893 > #6 0x5639d4ccd6af in query(char const*, ...) /home/smarchi/src/binutils-gdb/gdb/utils.c:985 > #7 0x5639d4ccaec1 in internal_vproblem /home/smarchi/src/binutils-gdb/gdb/utils.c:373 > #8 0x5639d4ccb3d1 in internal_verror(char const*, int, char const*, __va_list_tag*) /home/smarchi/src/binutils-gdb/gdb/utils.c:439 > #9 0x5639d5151a92 in internal_error(char const*, int, char const*, ...) /home/smarchi/src/binutils-gdb/gdbsupport/errors.cc:55 > #10 0x5639d5162ab4 in gdb_abspath(char const*) /home/smarchi/src/binutils-gdb/gdbsupport/pathstuff.cc:132 > #11 0x5639d5162fac in get_standard_cache_dir[abi:cxx11]() /home/smarchi/src/binutils-gdb/gdbsupport/pathstuff.cc:228 > #12 0x5639d3e76a81 in _initialize_index_cache() /home/smarchi/src/binutils-gdb/gdb/dwarf2/index-cache.c:325 > #13 0x5639d4dbbe92 in initialize_all_files() /home/smarchi/build/binutils-gdb/gdb/init.c:321 > #14 0x5639d4b00259 in gdb_init(char*) /home/smarchi/src/binutils-gdb/gdb/top.c:2344 > #15 0x5639d4440715 in captured_main_1 /home/smarchi/src/binutils-gdb/gdb/main.c:950 > #16 0x5639d444252e in captured_main /home/smarchi/src/binutils-gdb/gdb/main.c:1229 > #17 0x5639d44425cf in gdb_main(captured_main_args*) /home/smarchi/src/binutils-gdb/gdb/main.c:1254 > #18 0x5639d3923371 in main /home/smarchi/src/binutils-gdb/gdb/gdb.c:32 > #19 0x7fa002d3f0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2) > #20 0x5639d392314d in _start (/home/smarchi/build/binutils-gdb/gdb/gdb+0x4d414d) > > gdb_abspath doesn't handle empty strings, so handle this case in the > callers. If a variable is defined but empty, I think it's reasonable in > this case to just ignore it, as if it was not defined. > > Note that this sometimes also lead to a segfault, because the failed > assertion happens very early during startup, before things are fully > initialized. > > gdbsupport/ChangeLog: > > PR gdb/27157 > * pathstuff.cc (get_standard_cache_dir, get_standard_config_dir, > find_gdb_home_config_file): Add empty string check. > > gdb/testsuite/ChangeLog: > > PR gdb/27157 > * gdb.base/empty-host-env-vars.exp: New test. LGTM. Thanks, Andrew > > Change-Id: I8654d8e97e74e1dff6d308c111ae4b1bbf07bef9 > --- > .../gdb.base/empty-host-env-vars.exp | 72 +++++++++++++++++++ > gdbsupport/pathstuff.cc | 14 ++-- > 2 files changed, 79 insertions(+), 7 deletions(-) > create mode 100644 gdb/testsuite/gdb.base/empty-host-env-vars.exp > > diff --git a/gdb/testsuite/gdb.base/empty-host-env-vars.exp b/gdb/testsuite/gdb.base/empty-host-env-vars.exp > new file mode 100644 > index 000000000000..bd7212e7b655 > --- /dev/null > +++ b/gdb/testsuite/gdb.base/empty-host-env-vars.exp > @@ -0,0 +1,72 @@ > +# Copyright 2021 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 . > + > +# GDB reads some environment variables on startup, make sure it behaves > +# correctly if these variables are defined but empty. > + > +set all_env_vars { HOME XDG_CACHE_HOME LOCALAPPDATA XDG_CONFIG_HOME } > + > +# Record the initial value of the index-cache directory. > +clean_restart > +set index_cache_directory "" > +gdb_test_multiple "show index-cache directory" "" { > + -re -wrap "The directory of the index cache is \"(.*)\"\\." { > + set index_cache_directory $expect_out(1,string) > + set index_cache_directory [string_to_regexp $index_cache_directory] > + pass $gdb_test_name > + } > +} > + > +foreach_with_prefix env_var_name $all_env_vars { > + # Restore the original state of the environment variable. > + save_vars env($env_var_name) { > + set env($env_var_name) {} > + clean_restart > + > + # Verify that the empty environment variable didn't affect the > + # index-cache directory setting, that we still see the initial value. > + # "HOME" is different, because if that one is unset, GDB isn't even > + # able to compute the default location. In that case, we expect it to > + # be empty. > + if { $env_var_name == "HOME" } { > + gdb_test "show index-cache directory" \ > + "The directory of the index cache is \"\"\\." > + } else { > + gdb_test "show index-cache directory" \ > + "The directory of the index cache is \"$index_cache_directory\"\\." > + } > + } > +} > + > +# Try the same, but with all the env vars set to an empty value at the same > +# time. > +with_test_prefix "all env vars" { > + set save_vars_arg {} > + foreach env_var_name $all_env_vars { > + lappend save_vars_arg env($env_var_name) > + } > + > + # Restore the original state of all the environment variables. > + save_vars $save_vars_arg { > + foreach env_var_name $all_env_vars { > + set env($env_var_name) {} > + } > + > + clean_restart > + > + gdb_test "show index-cache directory" \ > + "The directory of the index cache is \"\"\\." > + } > +} > diff --git a/gdbsupport/pathstuff.cc b/gdbsupport/pathstuff.cc > index 51ab8c651b20..ad13900819ef 100644 > --- a/gdbsupport/pathstuff.cc > +++ b/gdbsupport/pathstuff.cc > @@ -222,7 +222,7 @@ get_standard_cache_dir () > > #ifndef __APPLE__ > const char *xdg_cache_home = getenv ("XDG_CACHE_HOME"); > - if (xdg_cache_home != NULL) > + if (xdg_cache_home != NULL && xdg_cache_home[0] != '\0') > { > /* Make sure the path is absolute and tilde-expanded. */ > gdb::unique_xmalloc_ptr abs (gdb_abspath (xdg_cache_home)); > @@ -231,7 +231,7 @@ get_standard_cache_dir () > #endif > > const char *home = getenv ("HOME"); > - if (home != NULL) > + if (home != NULL && home[0] != '\0') > { > /* Make sure the path is absolute and tilde-expanded. */ > gdb::unique_xmalloc_ptr abs (gdb_abspath (home)); > @@ -240,14 +240,14 @@ get_standard_cache_dir () > > #ifdef WIN32 > const char *win_home = getenv ("LOCALAPPDATA"); > - if (win_home != NULL) > + if (win_home != NULL && win_home[0] != '\0') > { > /* Make sure the path is absolute and tilde-expanded. */ > gdb::unique_xmalloc_ptr abs (gdb_abspath (win_home)); > return string_printf ("%s/gdb", abs.get ()); > } > #endif > - > + > return {}; > } > > @@ -289,7 +289,7 @@ get_standard_config_dir () > > #ifndef __APPLE__ > const char *xdg_config_home = getenv ("XDG_CONFIG_HOME"); > - if (xdg_config_home != NULL) > + if (xdg_config_home != NULL && xdg_config_home[0] != '\0') > { > /* Make sure the path is absolute and tilde-expanded. */ > gdb::unique_xmalloc_ptr abs (gdb_abspath (xdg_config_home)); > @@ -298,7 +298,7 @@ get_standard_config_dir () > #endif > > const char *home = getenv ("HOME"); > - if (home != NULL) > + if (home != NULL && home[0] != '\0') > { > /* Make sure the path is absolute and tilde-expanded. */ > gdb::unique_xmalloc_ptr abs (gdb_abspath (home)); > @@ -340,7 +340,7 @@ find_gdb_home_config_file (const char *name, struct stat *buf) > } > > const char *homedir = getenv ("HOME"); > - if (homedir != nullptr) > + if (homedir != nullptr && homedir[0] != '\0') > { > /* Make sure the path is absolute and tilde-expanded. */ > gdb::unique_xmalloc_ptr abs (gdb_abspath (homedir)); > -- > 2.29.2 >