From: Lancelot SIX <lancelot.six@amd.com>
To: gdb-patches@sourceware.org
Cc: Lancelot SIX <lancelot.six@amd.com>
Subject: [PATCH] gdb: ensure has dwarf info before reading DWZ file
Date: Sat, 30 Mar 2024 11:01:21 +0000 [thread overview]
Message-ID: <20240330110121.2292510-1-lancelot.six@amd.com> (raw)
I recent change (e9b738dfbdc "Avoid race when reading dwz file") moved
the call to dwarf2_read_dwz_file from dwarf2_initialize_objfile to
dwarf2_has_info.
Before that patch, dwarf2_initialize_objfile was only called when
dwarf2_has_info returned true, and since that patch it is always called.
When reading a file that has no debug info (.debug_info/.debug_abbrev
sections), but has a .gnu_debugaltlink section, GDB’s behavior is
different. I can observe this when loading
/lib/x86_64-linux-gnu/libtinfo.so on Ubuntu 22.04 (or while debugging
any program dynamically loading this library).
Before e9b738dfbdc, we had:
$ ./gdb/gdb -data-directory ./gdb/data-directory -q /lib/x86_64-linux-gnu/libtinfo.so
Reading symbols from /lib/x86_64-linux-gnu/libtinfo.so...
(No debugging symbols found in /lib/x86_64-linux-gnu/libtinfo.so)
(gdb)
while after we have:
$ ./gdb/gdb -data-directory ./gdb/data-directory -q /lib/x86_64-linux-gnu/libtinfo.so
Reading symbols from /lib/x86_64-linux-gnu/libtinfo.so...
warning: could not find '.gnu_debugaltlink' file for /usr/lib/x86_64-linux-gnu/libtinfo.so.6.3
(No debugging symbols found in /lib/x86_64-linux-gnu/libtinfo.so)
(gdb)
This patch restores the previous behavior of only trying to load the
DWZ file for objfiles when the main part of the debuginfo is present
(i.e. when dwarf2_has_info returns true). We still make sure that
dwarf2_read_dwz_file is called at most once per objfile.
A consequence of this change is that the per_bfd->dwz_file optional
object can now remain empty (instead of containing a nullptr), so also
this patch also adjusts dwarf2_get_dwz_file to account for this
possibility. This effectively reverts the changes to
dwarf2_get_dwz_file done by e9b738dfbdc.
Regression tested on x86_64-linux-gnu Ubuntu 22.04.
---
gdb/dwarf2/dwz.c | 13 +++++++++----
gdb/dwarf2/read.c | 36 +++++++++++++++++++-----------------
2 files changed, 28 insertions(+), 21 deletions(-)
diff --git a/gdb/dwarf2/dwz.c b/gdb/dwarf2/dwz.c
index 1eb4816fb47..c7cdba24076 100644
--- a/gdb/dwarf2/dwz.c
+++ b/gdb/dwarf2/dwz.c
@@ -282,9 +282,14 @@ dwarf2_read_dwz_file (dwarf2_per_objfile *per_objfile)
struct dwz_file *
dwarf2_get_dwz_file (dwarf2_per_bfd *per_bfd, bool require)
{
- gdb_assert (per_bfd->dwz_file.has_value ());
- dwz_file *result = per_bfd->dwz_file->get ();
- if (require && result == nullptr)
- error (_("could not read '.gnu_debugaltlink' section"));
+ gdb_assert (!require || per_bfd->dwz_file.has_value ());
+
+ dwz_file *result = nullptr;
+ if (per_bfd->dwz_file.has_value ())
+ {
+ result = per_bfd->dwz_file->get ();
+ if (require && result == nullptr)
+ error (_("could not read '.gnu_debugaltlink' section"));
+ }
return result;
}
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 31313bc88b3..9e37011ddf0 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -1362,11 +1362,11 @@ dwarf2_has_info (struct objfile *objfile,
return false;
dwarf2_per_objfile *per_objfile = get_dwarf2_per_objfile (objfile);
+ bool just_created = false;
if (per_objfile == NULL)
{
dwarf2_per_bfd *per_bfd;
- bool just_created = false;
/* We can share a "dwarf2_per_bfd" with other objfiles if the
BFD doesn't require relocations.
@@ -1398,27 +1398,29 @@ dwarf2_has_info (struct objfile *objfile,
}
per_objfile = dwarf2_objfile_data_key.emplace (objfile, objfile, per_bfd);
+ }
+
+ const bool has_info = (!per_objfile->per_bfd->info.is_virtual
+ && per_objfile->per_bfd->info.s.section != nullptr
+ && !per_objfile->per_bfd->abbrev.is_virtual
+ && per_objfile->per_bfd->abbrev.s.section != nullptr);
- if (just_created)
+ if (just_created && has_info)
+ {
+ /* Try to fetch any potential dwz file early, while still on
+ the main thread. Also, be sure to do it just once per
+ BFD, to avoid races. */
+ try
{
- /* Try to fetch any potential dwz file early, while still on
- the main thread. Also, be sure to do it just once per
- BFD, to avoid races. */
- try
- {
- dwarf2_read_dwz_file (per_objfile);
- }
- catch (const gdb_exception_error &err)
- {
- warning (_("%s"), err.what ());
- }
+ dwarf2_read_dwz_file (per_objfile);
+ }
+ catch (const gdb_exception_error &err)
+ {
+ warning (_("%s"), err.what ());
}
}
- return (!per_objfile->per_bfd->info.is_virtual
- && per_objfile->per_bfd->info.s.section != NULL
- && !per_objfile->per_bfd->abbrev.is_virtual
- && per_objfile->per_bfd->abbrev.s.section != NULL);
+ return has_info;
}
/* See declaration. */
base-commit: 13ed3225004896142dcb0fbe24411b66f17dfc8e
--
2.34.1
next reply other threads:[~2024-03-30 11:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-30 11:01 Lancelot SIX [this message]
2024-04-01 16:09 ` Tom Tromey
2024-04-02 8:40 ` Six, Lancelot
2024-04-02 13:16 ` Tom Tromey
2024-04-03 12:55 ` Lancelot SIX
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240330110121.2292510-1-lancelot.six@amd.com \
--to=lancelot.six@amd.com \
--cc=gdb-patches@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).