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[PATCH v2 2/3] gdb: New maintenance command to disable bfd sharing.
- From: Andrew Burgess <andrew dot burgess at embecosm dot com>
- To: gdb-patches at sourceware dot org
- Cc: Andrew Burgess <andrew dot burgess at embecosm dot com>
- Date: Thu, 13 Aug 2015 13:44:59 +0100
- Subject: [PATCH v2 2/3] gdb: New maintenance command to disable bfd sharing.
- Authentication-results: sourceware.org; auth=none
- References: <cover dot 1439454669 dot git dot andrew dot burgess at embecosm dot com>
- References: <cover dot 1439454669 dot git dot andrew dot burgess at embecosm dot com>
In some rare maintainer cases it is desirable to be able to disable bfd
sharing. This patch adds new commands maintenance set/show commands for
bfd-sharing, allowing gdb's bfd cache to be turned off.
gdb/ChangeLog:
* gdb_bfd.c (bfd_sharing): New variable.
(gdb_bfd_open): Check bfd_sharing variable.
(_initialize_gdb_bfd): Add new set/show command.
* NEWS: Mention new command.
gdb/doc/ChangeLog:
* gdb.texinfo (Maintenance Commands): Move documentation of "main
info bfds" to...
(File Caching): A New section. Outline bfd caching, and add new
description for "main set/show bfd-sharing".
---
gdb/ChangeLog | 7 +++++++
gdb/NEWS | 4 ++++
gdb/doc/ChangeLog | 7 +++++++
gdb/doc/gdb.texinfo | 35 ++++++++++++++++++++++++++++++-----
gdb/gdb_bfd.c | 29 +++++++++++++++++++++++++----
5 files changed, 73 insertions(+), 9 deletions(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index d920ea0..0f73f08 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,12 @@
2015-08-11 Andrew Burgess <andrew.burgess@embecosm.com>
+ * gdb_bfd.c (bfd_sharing): New variable.
+ (gdb_bfd_open): Check bfd_sharing variable.
+ (_initialize_gdb_bfd): Add new set/show command.
+ * NEWS: Mention new command.
+
+2015-08-11 Andrew Burgess <andrew.burgess@embecosm.com>
+
* gdb_bfd.c (struct gdb_bfd_data): Add size, inode, and device id
field.
(struct gdb_bfd_cache_search): Likewise.
diff --git a/gdb/NEWS b/gdb/NEWS
index 3fe6036..87fc14e 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -16,6 +16,10 @@ maint show target-non-stop
"set non-stop" is "off". The default is "auto", meaning non-stop
mode is enabled if supported by the target.
+maint set bfd-sharing
+maint show bfd-sharing
+ Control the reuse of bfd objects.
+
*** Changes in GDB 7.10
* Support for process record-replay and reverse debugging on aarch64*-linux*
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index 846ac24..9d553db 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,10 @@
+2015-08-11 Andrew Burgess <andrew.burgess@embecosm.com>
+
+ * gdb.texinfo (Maintenance Commands): Move documentation of "main
+ info bfds" to...
+ (File Caching): A New section. Outline bfd caching, and add new
+ description for "main set/show bfd-sharing".
+
2015-08-07 Pedro Alves <palves@redhat.com>
* gdb.texinfo (Maintenance Commands): Document "maint set/show
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 900970b..3cfb1a7 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -18190,6 +18190,36 @@ Set whether a source file may have multiple base names.
Show whether a source file may have multiple base names.
@end table
+@node File Caching
+@section File Caching
+@cindex caching of opened files
+@cindex caching of bfd objects
+
+To speed up file loading, and reduce memory usage, @value{GDBN} will
+reuse the @code{bfd} objects used to track open files. @xref{Top, ,
+BFD, bfd, The Binary File Descriptor Library}. The following commands
+allow visibility and control of the caching beaviour.
+
+@table @code
+@kindex maint info bfds
+@item maint info bfds
+This prints information about each @code{bfd} object that is known to
+@value{GDBN}.
+
+@kindex maint set bfd-sharing
+@kindex maint show bfd-sharing
+@kindex bfd caching
+@item maint set bfd-sharing
+@item maint show bfd-sharing
+Control whether @code{bfd} objects can be shared. When sharing is
+enabled @value{GDBN} will reuse already open @code{bfd} objects rather
+than reopening the same file. Turning sharing off does not cause
+already shared @code{bfd} objects to be unshared, but all future files
+that are opened will create a new @code{bfd} object. Similarly,
+re-enabling sharing will not cause multiple existing @code{bfd}
+objects to be collapsed into a single shared @code{bfd} object.
+@end table
+
@node Separate Debug Files
@section Debugging Information in Separate Files
@cindex separate debugging information files
@@ -33987,11 +34017,6 @@ Shared library events.
@end table
-@kindex maint info bfds
-@item maint info bfds
-This prints information about each @code{bfd} object that is known to
-@value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
-
@kindex maint info btrace
@item maint info btrace
Pint information about raw branch tracing data.
diff --git a/gdb/gdb_bfd.c b/gdb/gdb_bfd.c
index ee29531..14fdf43 100644
--- a/gdb/gdb_bfd.c
+++ b/gdb/gdb_bfd.c
@@ -111,6 +111,11 @@ DEFINE_REGISTRY (bfd, GDB_BFD_DATA_ACCESSOR)
static htab_t gdb_bfd_cache;
+/* When true gdb will reuse an existing bfd object if the filename,
+ modification time, and file size all match. */
+
+static int bfd_sharing;
+
/* The type of an object being looked up in gdb_bfd_cache. We use
htab's capability of storing one kind of object (BFD in this case)
and using a different sort of object for searching. */
@@ -394,7 +399,7 @@ gdb_bfd_open (const char *name, const char *target, int fd)
opening the BFD may fail; and this would violate hashtab
invariants. */
abfd = htab_find_with_hash (gdb_bfd_cache, &search, hash);
- if (abfd != NULL)
+ if (bfd_sharing && abfd != NULL)
{
close (fd);
gdb_bfd_ref (abfd);
@@ -405,9 +410,12 @@ gdb_bfd_open (const char *name, const char *target, int fd)
if (abfd == NULL)
return NULL;
- slot = htab_find_slot_with_hash (gdb_bfd_cache, &search, hash, INSERT);
- gdb_assert (!*slot);
- *slot = abfd;
+ if (bfd_sharing)
+ {
+ slot = htab_find_slot_with_hash (gdb_bfd_cache, &search, hash, INSERT);
+ gdb_assert (!*slot);
+ *slot = abfd;
+ }
gdb_bfd_ref (abfd);
return abfd;
@@ -942,4 +950,17 @@ _initialize_gdb_bfd (void)
add_cmd ("bfds", class_maintenance, maintenance_info_bfds, _("\
List the BFDs that are currently open."),
&maintenanceinfolist);
+
+ add_setshow_boolean_cmd ("bfd-sharing", no_class,
+ &bfd_sharing, _("\
+Set whether gdb will share bfds that appear to be the same file."), _("\
+Show whether gdb will share bfds that appear to be the same file."), _("\
+When enabled gdb will reuse existing bfds rather than reopening the\n\
+same file. To decide if two files are the same then gdb compares the\n\
+filename, file size, file modification time, and file inode."),
+ NULL,
+ NULL,
+ &maintenance_set_cmdlist,
+ &maintenance_show_cmdlist);
+ bfd_sharing = 1;
}
--
2.4.0