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gdb: add a new 'maint info target-sections' command

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We already have a command 'maint info sections', this command prints
all sections from all known object files.

However, GDB maintains a second section table internally.  This
section table is used when GDB wants to read directly from an object
file rather than actually reading memory on the target.  As such only
some sections (the allocatable ones) are added to this secondary
section table.

I recently ran into a situation where some of GDB's optimisations for
reading directly from the files were not working.  In 'maint info
sections' I could see that GDB knew about the object file, and did
know about the sections that it _should_ have been reading from.  But
I couldn't ask GDB which sections it had copied into its secondary
section table.

This commit adds a new command 'maint info target-sections' that fills
this gap.  This command lists only those sections that GDB has copied
into its secondary table.

You'll notice that the testsuite includes a comment indicating that
there's a bug in GDB.  Normally this is not something I would add to
the testsuite, instead we should raise an actual bugzilla bug and then
mark an xfail, however, a later patch in this series will remove this
comment once the actual bug in GDB is fixed.

gdb/ChangeLog:

	* NEWS: Mention new 'maint info target-sections' command.
	* maint.c (maintenance_info_target_sections): New function.
	(_initialize_maint_cmds): Register new command.

gdb/doc/ChangeLog:

	* gdb.texinfo (Files): Document new 'maint info target-sections'
	command.

gdb/testsuite/ChangeLog:

	* gdb.base/maint-info-sections.exp: Add new tests.
	(check_maint_info_target_sections_output): New proc.
This commit is contained in:
Andrew Burgess 2021-02-12 16:10:56 +00:00
parent 895b7b4e4b
commit 02a7930992
7 changed files with 153 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
gdb/ChangeLog
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@ -1,3 +1,9 @@
2021-02-24 Andrew Burgess <andrew.burgess@embecosm.com>
* NEWS: Mention new 'maint info target-sections' command.
* maint.c (maintenance_info_target_sections): New function.
(_initialize_maint_cmds): Register new command.
2021-02-24 Andrew Burgess <andrew.burgess@embecosm.com>
* riscv-tdep.c (riscv_features_from_gdbarch_info): Rename to...

3
gdb/NEWS
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@ -47,6 +47,9 @@ maintenance flush register-cache
maintenance flush dcache
A new command to flush the dcache.
maintenance info target-sections
Print GDB's internal target sections table.
* Changed commands
break [PROBE_MODIFIER] [LOCATION] [thread THREADNUM]

5
gdb/doc/ChangeLog
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@ -1,3 +1,8 @@
2021-02-24 Andrew Burgess <andrew.burgess@embecosm.com>
* gdb.texinfo (Files): Document new 'maint info target-sections'
command.
2021-02-17 Lancelot Six <lsix@lancelotsix.com>
PR cli/17290

8
gdb/doc/gdb.texinfo
View File

@ -20668,6 +20668,14 @@ COFF shared library information.
Section contains common symbols.
@end table
@end table
@kindex maint info target-sections
@item maint info target-sections
This command prints @value{GDBN}'s internal section table. For each
target @value{GDBN} maintains a table containing the allocatable
sections from all currently mapped objects, along with information
about where the section is mapped.
@kindex set trust-readonly-sections
@cindex read-only sections
@item set trust-readonly-sections on

59
gdb/maint.c
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@ -464,6 +464,56 @@ maintenance_info_sections (const char *arg, int from_tty)
maint_print_all_sections (_("Core file: "), core_bfd, nullptr, arg);
}
/* Implement the "maintenance info target-sections" command. */
static void
maintenance_info_target_sections (const char *arg, int from_tty)
{
bfd *abfd = nullptr;
int digits = 0;
const target_section_table *table
= target_get_section_table (current_top_target ());
if (table == nullptr)
return;
for (const target_section &sec : *table)
{
if (abfd == nullptr || sec.the_bfd_section->owner != abfd)
{
abfd = sec.the_bfd_section->owner;
digits = std::max (index_digits (gdb_bfd_count_sections (abfd)),
digits);
}
}
struct gdbarch *gdbarch = nullptr;
int addr_size = 0;
abfd = nullptr;
for (const target_section &sec : *table)
{
if (sec.the_bfd_section->owner != abfd)
{
abfd = sec.the_bfd_section->owner;
gdbarch = gdbarch_from_bfd (abfd);
addr_size = gdbarch_addr_bit (gdbarch) / 8;
printf_filtered (_("From '%s', file type %s:\n"),
bfd_get_filename (abfd), bfd_get_target (abfd));
}
print_bfd_section_info (abfd,
sec.the_bfd_section,
nullptr,
digits);
/* The magic '8 + digits' here ensures that the 'Start' is aligned
with the output of print_bfd_section_info. */
printf_filtered ("%*sStart: %s, End: %s, Owner token: %p\n",
(8 + digits), "",
hex_string_custom (sec.addr, addr_size),
hex_string_custom (sec.endaddr, addr_size),
sec.owner);
}
}
static void
maintenance_print_statistics (const char *args, int from_tty)
{
@ -1122,6 +1172,15 @@ Options:\n\
&maintenanceinfolist);
set_cmd_completer_handle_brkchars (cmd, maint_info_sections_completer);
add_cmd ("target-sections", class_maintenance,
maintenance_info_target_sections, _("\
List GDB's internal section table.\n\
\n\
Print the current targets section list. This is a sub-set of all\n\
sections, from all objects currently loaded. Usually the ALLOC\n\
sectoins."),
&maintenanceinfolist);
add_basic_prefix_cmd ("print", class_maintenance,
_("Maintenance command for printing GDB internal state."),
&maintenanceprintlist, "maintenance print ", 0,

5
gdb/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2021-02-24 Andrew Burgess <andrew.burgess@embecosm.com>
* gdb.base/maint-info-sections.exp: Add new tests.
(check_maint_info_target_sections_output): New proc.
2021-02-24 Andrew Burgess <andrew.burgess@embecosm.com>
* gdb.arch/riscv-default-tdesc.exp: New file.

68
gdb/testsuite/gdb.base/maint-info-sections.exp
View File

@ -13,7 +13,8 @@
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
# Test just for the 'maintenance info sections' command.
# Test just for the 'maintenance info sections' command and the
# 'maintenance info target-sections' command.
load_lib completion-support.exp
@ -29,6 +30,65 @@ if ![runto_main] then {
return -1
}
# Check the output of 'maint info target-sections' command.
proc check_maint_info_target_sections_output {prefix} {
global hex gdb_prompt
with_test_prefix $prefix {
# Check the output of the 'maint info target-sections' command.
# Ensures that all the lines have the expected format, and that we see
# an auxiliary information line after every section information line.
#
# We also check that every bfd section has the ALLOC flag.
set seen_header false
set seen_a_section false
set seen_aux_info false
set expecting_aux_info false
gdb_test_multiple "maint info target-sections" "" {
-re "^maint info target-sections\r\n" {
# Consume the command we sent to GDB that the terminal echo'd
# back.
exp_continue
}
-re "^From '\[^\r\n\]+', file type \[^\r\n\]+:\r\n" {
# There might be more than one header, but there should be at
# least one.
set seen_header true
if { $expecting_aux_info } {
fail $gdb_test_name
} else {
exp_continue
}
}
-re "^ \\\[\[0-9\]+\\\]\\s+$hex->$hex at $hex: \[^*\r\]+\\yALLOC\\y\[^*\r\]*\r\n" {
# A bfd section description line.
set seen_a_section true
if { $expecting_aux_info } {
fail $gdb_test_name
} else {
set expecting_aux_info true
exp_continue
}
}
-re "^\\s+Start: $hex, End: $hex, Owner token: $hex\r\n" {
# A target section auxiliary information line.
set seen_aux_info true
if { !$expecting_aux_info } {
fail $gdb_test_name
} else {
set expecting_aux_info false
exp_continue
}
}
-re "^$gdb_prompt $" {
gdb_assert { $seen_header && $seen_a_section && $seen_aux_info }
gdb_assert { !$expecting_aux_info }
pass $gdb_test_name
}
}
}
}
# Check that 'maint info sections' output looks correct. When
# checking the lines for each section we reject section names starting
# with a '*' character, the internal *COM*, *UND*, *ABS*, and *IND*
@ -128,6 +188,8 @@ gdb_test_multiple "maint info sections DATA" "" {
}
}
check_maint_info_target_sections_output "with executable"
# Restart GDB, but don't load the executable.
clean_restart
@ -161,6 +223,10 @@ gdb_test_multiple "maint info sections -all-objects" "" {
}
}
# NOTE: We would like to check 'maint info target-sections' again
# here, but GDB currently doesn't display the target sections table in
# this case. This is a bug and will be fixed shortly!!
# Test the command line completion on 'maint info sections'. First
# the command line flag.
test_gdb_complete_unique \