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gdb: fix reopen_exec_file for files with target: prefix

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Following on from this commit:

  commit f2c4f78c813a9cef38b7e9c9ad18822fb9e19345
  Date:   Thu Sep 21 16:35:30 2023 +0100

      gdb: fix reread_symbols when an objfile has target: prefix

In this commit I update reopen_exec_file to correctly handle
executables with a target: prefix.  Before this commit we used the
system 'stat' call, which obviously isn't going to work for files with
a target: prefix (files located on a possibly remote target machine).

By switching to bfd_stat we will use remote fileio to stat the remote
files, which means we should now correctly detect changes in a remote
executable.

The program_space::ebfd_mtime variable, with which we compare the
result of bfd_stat is set with a call to bfd_get_mtime, which in turn
calls bfd_stat, so comparing to the result of calling bfd_stat makes
sense (I think).

As I discussed in the commit f2c4f78c813a, if a BFD is an in-memory
BFD, then calling bfd_stat will always return 0, while bfd_get_mtime
will always return the time at which the BFD was created.  As a result
comparing the results will always show the file having changed.

I don't believe that GDB can set the main executable to an in-memory
BFD object, so, in this commit, I simply assert that the executable is
not in-memory.  If this ever changes then we would need to decide how
to handle this case -- always reload, or never reload.  The assert
doesn't appear to trigger for our current test suite.

Approved-By: Tom Tromey <tom@tromey.com>
This commit is contained in:
Andrew Burgess 2023-10-05 13:12:42 +01:00
parent 96619f154a
commit 70fd94b244
2 changed files with 80 additions and 7 deletions
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17
gdb/corefile.c
View File

@ -105,21 +105,24 @@ specify_exec_file_hook (void (*hook) (const char *))
void
reopen_exec_file (void)
{
int res;
struct stat st;
bfd *exec_bfd = current_program_space->exec_bfd ();
/* Don't do anything if there isn't an exec file. */
if (current_program_space->exec_bfd () == NULL)
if (exec_bfd == nullptr)
return;
/* The main executable can't be an in-memory BFD object. If it was then
the use of bfd_stat below would not work as expected. */
gdb_assert ((exec_bfd->flags & BFD_IN_MEMORY) == 0);
/* If the timestamp of the exec file has changed, reopen it. */
std::string filename = bfd_get_filename (current_program_space->exec_bfd ());
res = stat (filename.c_str (), &st);
struct stat st;
int res = bfd_stat (exec_bfd, &st);
if (res == 0
&& current_program_space->ebfd_mtime
&& current_program_space->ebfd_mtime != 0
&& current_program_space->ebfd_mtime != st.st_mtime)
exec_file_attach (filename.c_str (), 0);
exec_file_attach (bfd_get_filename (exec_bfd), 0);
}
/* If we have both a core file and an exec file,

70
gdb/testsuite/gdb.server/target-exec-file.exp
View File

@ -52,6 +52,19 @@ set target_exec [gdb_remote_download target $binfile]
# prompt us if this is the right thing to do.
gdb_test_no_output "set confirm off"
if { [allow_python_tests] } {
# Register an event handler for the executable changed event.
# This handler just copies the event into a global Python object.
gdb_test_multiline "Add connection_removed event" \
"python" "" \
"global_exec_changed_event = None" "" \
"def executable_changed(event):" "" \
" global global_exec_changed_event" "" \
" global_exec_changed_event = event" "" \
"gdb.events.executable_changed.connect (executable_changed)" "" \
"end" ""
}
# Start gdbserver, but always in extended-remote mode, and then
# connect to it from GDB.
set res [gdbserver_start "--multi" $target_exec]
@ -59,6 +72,22 @@ set gdbserver_protocol "extended-remote"
set gdbserver_gdbport [lindex $res 1]
gdb_target_cmd $gdbserver_protocol $gdbserver_gdbport
if { [allow_python_tests] } {
# When connecting to a remote target, if the user has not told GDB
# which executable to use, then GDB will figure out an executable
# from the remote target.
#
# As a result we expect to have seen an executable changed event.
with_test_prefix "after connecting" {
gdb_test "python print(global_exec_changed_event)" \
"<gdb.ExecutableChangedEvent object at $hex>"
gdb_test "python print(global_exec_changed_event.progspace.executable_filename)" \
[string_to_regexp target:$target_exec]
gdb_test "python print(global_exec_changed_event.reload)" "False"
gdb_test_no_output "python global_exec_changed_event = None"
}
}
# Issue a 'file' command and parse the output. We look for a couple
# of specific things to ensure that we are correctly reading the exec
# from the remote target.
@ -104,6 +133,20 @@ gdb_assert { $saw_read_of_remote_exec } \
gdb_assert { $saw_read_of_syms_from_exec } \
"symbols were read from remote exec file"
if { [allow_python_tests] } {
# The 'file' command forces GDB to always load the executable,
# even if the same filename is used. In this case, as the
# filename is the same, this will show as a reload event.
with_test_prefix "after 'file' command" {
gdb_test "python print(global_exec_changed_event)" \
"<gdb.ExecutableChangedEvent object at $hex>"
gdb_test "python print(global_exec_changed_event.progspace.executable_filename)" \
[string_to_regexp target:$target_exec]
gdb_test "python print(global_exec_changed_event.reload)" "True"
gdb_test_no_output "python global_exec_changed_event = None"
}
}
# Start the inferior (with the 'start' command), use TESTNAME for any
# pass/fail calls. EXPECT_REREAD should be true or false and
# indicates if we expect to too a line like:
@ -155,10 +198,24 @@ proc start_inferior { testname expect_reread } {
# see the symbols re-read now.
start_inferior "start inferior the first time" false
if { [allow_python_tests] } {
# The executable hasn't changed.
with_test_prefix "after starting inferior for the first time" {
gdb_test "python print(global_exec_changed_event)" "None"
}
}
# Re-start the inferior. The executable is unchanged so we should not
# see the symbol file being re-read.
start_inferior "start inferior a second time" false
if { [allow_python_tests] } {
# The executable still hasn't changed.
with_test_prefix "after starting inferior for the second time" {
gdb_test "python print(global_exec_changed_event)" "None"
}
}
# Delay for a short while so, when we touch the exec, we know the
# timestamp will change.
sleep 1
@ -172,3 +229,16 @@ if { $status != 0 } {
# Start the inferior again, we expect to see the symbols being re-read
# from the remote file.
start_inferior "start inferior a third time" true
if { [allow_python_tests] } {
# The executable has now changed on disk. This will be a reload
# event.
with_test_prefix "after starting inferior for the third time" {
gdb_test "python print(global_exec_changed_event)" \
"<gdb.ExecutableChangedEvent object at $hex>"
gdb_test "python print(global_exec_changed_event.progspace.executable_filename)" \
[string_to_regexp target:$target_exec]
gdb_test "python print(global_exec_changed_event.reload)" "True"
gdb_test_no_output "python global_exec_changed_event = None"
}
}