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binutils-gdb/gdb/exec.c
Andrew Burgess 96619f154a gdb: move all bfd_cache_close_all calls in gdb_bfd.c 
In the following commit I ran into a problem.  The next commit aims to
improve GDB's handling of the main executable being a file on a remote
target (i.e. one with a 'target:' prefix).

To do this I have replaced a system 'stat' call with a bfd_stat call.

However, doing this caused a regression in gdb.base/attach.exp.

The problem is that the bfd library caches open FILE* handles for bfd
objects that it has accessed, which is great for short-lived, non
interactive programs (e.g. the assembler, or objcopy, etc), however,
for GDB this caching causes us a problem.

If we open the main executable as a bfd then the bfd library will
cache the open FILE*.  If some time passes, maybe just sat at the GDB
prompt, or with the inferior running, and then later we use bfd_stat
to check if the underlying, on-disk file has changed, then the bfd
library will actually use fstat on the underlying file descriptor.
This is of course slightly different than using system stat on with
the on-disk file name.

If the on-disk file has changed then system stat will give results for
the current on-disk file.  But, if the bfd cache is still holding open
the file descriptor for the original on-disk file (from before the
change) then fstat will return a result based on the original file,
and so show no change as having happened.

This is a known problem in GDB, and so far this has been solved by
scattering bfd_cache_close_all() calls throughout GDB.  But, as I
said, in the next commit I've made a change and run into a
problem (gdb.base/attach.exp) where we are apparently missing a
bfd_cache_close_all() call.

Now I could solve this problem by adding a bfd_cache_close_all() call
before the bfd_stat call that I plan to add in the next commit, that
would for sure solve the problem, but feels a little crude.

Better I think would be to track down where the bfd is being opened
and add a corresponding bfd_cache_close_all() call elsewhere in GDB
once we've finished doing whatever it is that caused us to open the
bfd in the first place.

This second solution felt like the better choice, so I tracked the
problem down to elf_locate_base and fixed that.  But that just exposed
another problem in gdb_bfd_map_section which was also re-opening the
bfd, so I fixed this (with another bfd_cache_close_all() call), and
that exposed another issue in gdbarch_lookup_osabi... and at this
point I wondered if I was approaching this problem the wrong way...

.... And so, I wonder, is there a _better_ way to handle these
bfd_cache_close_all() calls?

I see two problems with the current approach:

  1. It's fragile.  Folk aren't always aware that they need to clear
  the bfd cache, and this feels like something that is easy to
  overlook in review.  So adding new code to GDB can innocently touch
  a bfd, which populates the cache, which will then be a bug that can
  lie hidden until an on-disk file just happens to change at the wrong
  time ... and GDB fails to spot the change.  Additionally,

  2. It's in efficient.  The caching is intended to stop the bfd
  library from continually having to re-open the on-disk file.  If we
  have a function that touches a bfd then often that function is the
  obvious place to call bfd_cache_close_all.  But if a single GDB
  command calls multiple functions, each of which touch the bfd, then
  we will end up opening and closing the same on-disk file multiple
  times.  It feels like we would be better postponing the
  bfd_cache_close_all call until some later point, then we can benefit
  from the bfd cache.

So, in this commit I propose a new approach.  We now clear the bfd
cache in two places:

  (a) Just before we display a GDB prompt.  We display a prompt after
  completing a command, and GDB is about to enter an idle state
  waiting for further input from the user (or in async mode, for an
  inferior event).  If while we are in this idle state the user
  changes the on-disk file(s) then we would like GDB to notice this
  the next time it leaves its idle state, e.g. the next time the user
  executes a command, or when an inferior event arrives,

  (b) When we resume the inferior.  In synchronous mode, resuming the
  inferior is another time when GDB is blocked and sitting idle, but
  in this case we don't display a prompt.  As with (a) above, when an
  inferior event arrives we want GDB to notice any changes to on-disk
  files.

It turns out that there are existing observers for both of these
cases (before_prompt and target_resumed respectively), so my initial
thought was that I should attach to these observers in gdb_bfd.c, and
in both cases call bfd_cache_close_all().

And this does indeed solve the gdb.base/attach.exp problem that I see
with the following commit.

However, I see a problem with this solution.

Both of the observers I'm using are exposed through the Python API as
events that a user can hook into.  The user can potentially run any
GDB command (using gdb.execute), so Python code might end up causing
some bfds to be reopened, and inserted into the cache.

To solve this one solution would be to add a bfd_cache_close_all()
call into gdbpy_enter::~gdbpy_enter().  Unfortunately, there's no
similar enter/exit object for Guile, though right now Guile doesn't
offer the same event API, so maybe we could just ignore that
problem... but this doesn't feel great.

So instead, I think a better solution might be to not use observers
for the bfd_cache_close_all() calls.  Instead, I'll call
bfd_cache_close_all() directly from core GDB after we've notified the
before_prompt and target_resumed observers, this was we can be sure
that the cache is cleared after the observers have run, and before GDB
enters an idle state.

This commit also removes all of the other bfd_cache_close_all() calls
from GDB.  My claim is that these are no longer needed.

Approved-By: Tom Tromey <tom@tromey.com>
2023-11-20 10:54:17 +00:00

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/* Work with executable files, for GDB.
Copyright (C) 1988-2023 Free Software Foundation, Inc.
This file is part of GDB.
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 <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "frame.h"
#include "inferior.h"
#include "target.h"
#include "gdbcmd.h"
#include "language.h"
#include "filenames.h"
#include "symfile.h"
#include "objfiles.h"
#include "completer.h"
#include "value.h"
#include "exec.h"
#include "observable.h"
#include "arch-utils.h"
#include "gdbthread.h"
#include "progspace.h"
#include "progspace-and-thread.h"
#include "gdb_bfd.h"
#include "gcore.h"
#include "source.h"
#include "build-id.h"
#include <fcntl.h>
#include "readline/tilde.h"
#include "gdbcore.h"
#include <ctype.h>
#include <sys/stat.h>
#include "solist.h"
#include <algorithm>
#include "gdbsupport/pathstuff.h"
#include "cli/cli-style.h"
#include "gdbsupport/buildargv.h"
void (*deprecated_file_changed_hook) (const char *);
static const target_info exec_target_info = {
"exec",
N_("Local exec file"),
N_("Use an executable file as a target.\n\
Specify the filename of the executable file.")
};
/* The target vector for executable files. */
struct exec_target final : public target_ops
{
const target_info &info () const override
{ return exec_target_info; }
strata stratum () const override { return file_stratum; }
void close () override;
enum target_xfer_status xfer_partial (enum target_object object,
const char *annex,
gdb_byte *readbuf,
const gdb_byte *writebuf,
ULONGEST offset, ULONGEST len,
ULONGEST *xfered_len) override;
void files_info () override;
bool has_memory () override;
gdb::unique_xmalloc_ptr<char> make_corefile_notes (bfd *, int *) override;
int find_memory_regions (find_memory_region_ftype func, void *data) override;
};
static exec_target exec_ops;
/* How to handle a mismatch between the current exec file and the exec
file determined from target. */
static const char *const exec_file_mismatch_names[]
= {"ask", "warn", "off", NULL };
enum exec_file_mismatch_mode
{
exec_file_mismatch_ask, exec_file_mismatch_warn, exec_file_mismatch_off
};
static const char *exec_file_mismatch = exec_file_mismatch_names[0];
static enum exec_file_mismatch_mode exec_file_mismatch_mode
= exec_file_mismatch_ask;
/* Show command. */
static void
show_exec_file_mismatch_command (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
gdb_printf (file,
_("exec-file-mismatch handling is currently \"%s\".\n"),
exec_file_mismatch_names[exec_file_mismatch_mode]);
}
/* Set command. Change the setting for range checking. */
static void
set_exec_file_mismatch_command (const char *ignore,
int from_tty, struct cmd_list_element *c)
{
for (enum exec_file_mismatch_mode mode = exec_file_mismatch_ask;
;
mode = static_cast<enum exec_file_mismatch_mode>(1 + (int) mode))
{
if (strcmp (exec_file_mismatch, exec_file_mismatch_names[mode]) == 0)
{
exec_file_mismatch_mode = mode;
return;
}
if (mode == exec_file_mismatch_off)
internal_error (_("Unrecognized exec-file-mismatch setting: \"%s\""),
exec_file_mismatch);
}
}
/* Whether to open exec and core files read-only or read-write. */
bool write_files = false;
static void
show_write_files (struct ui_file *file, int from_tty,
struct cmd_list_element *c, const char *value)
{
gdb_printf (file, _("Writing into executable and core files is %s.\n"),
value);
}
static void
exec_target_open (const char *args, int from_tty)
{
target_preopen (from_tty);
exec_file_attach (args, from_tty);
}
/* This is the target_close implementation. Clears all target
sections and closes all executable bfds from all program spaces. */
void
exec_target::close ()
{
for (struct program_space *ss : program_spaces)
{
ss->clear_target_sections ();
ss->exec_close ();
}
}
/* See gdbcore.h. */
void
try_open_exec_file (const char *exec_file_host, struct inferior *inf,
symfile_add_flags add_flags)
{
struct gdb_exception prev_err;
/* exec_file_attach and symbol_file_add_main may throw an error if the file
cannot be opened either locally or remotely.
This happens for example, when the file is first found in the local
sysroot (above), and then disappears (a TOCTOU race), or when it doesn't
exist in the target filesystem, or when the file does exist, but
is not readable.
Even without a symbol file, the remote-based debugging session should
continue normally instead of ending abruptly. Hence we catch thrown
errors/exceptions in the following code. */
try
{
/* We must do this step even if exec_file_host is NULL, so that
exec_file_attach will clear state. */
exec_file_attach (exec_file_host, add_flags & SYMFILE_VERBOSE);
}
catch (gdb_exception_error &err)
{
if (err.message != NULL)
warning ("%s", err.what ());
prev_err = std::move (err);
}
if (exec_file_host != NULL)
{
try
{
symbol_file_add_main (exec_file_host, add_flags);
}
catch (const gdb_exception_error &err)
{
if (prev_err != err)
warning ("%s", err.what ());
}
}
}
/* See gdbcore.h. */
void
validate_exec_file (int from_tty)
{
/* If user asked to ignore the mismatch, do nothing. */
if (exec_file_mismatch_mode == exec_file_mismatch_off)
return;
const char *current_exec_file = get_exec_file (0);
struct inferior *inf = current_inferior ();
/* Try to determine a filename from the process itself. */
const char *pid_exec_file = target_pid_to_exec_file (inf->pid);
bool build_id_mismatch = false;
/* If we cannot validate the exec file, return. */
if (current_exec_file == NULL || pid_exec_file == NULL)
return;
/* Try validating via build-id, if available. This is the most
reliable check. */
/* In case current_exec_file was changed, reopen_exec_file ensures
an up to date build_id (will do nothing if the file timestamp
did not change). If exec file changed, reopen_exec_file has
allocated another file name, so get_exec_file again. */
reopen_exec_file ();
current_exec_file = get_exec_file (0);
const bfd_build_id *exec_file_build_id
= build_id_bfd_get (current_program_space->exec_bfd ());
if (exec_file_build_id != nullptr)
{
/* Prepend the target prefix, to force gdb_bfd_open to open the
file on the remote file system (if indeed remote). */
std::string target_pid_exec_file
= std::string (TARGET_SYSROOT_PREFIX) + pid_exec_file;
gdb_bfd_ref_ptr abfd (gdb_bfd_open (target_pid_exec_file.c_str (),
gnutarget, -1, false));
if (abfd != nullptr)
{
const bfd_build_id *target_exec_file_build_id
= build_id_bfd_get (abfd.get ());
if (target_exec_file_build_id != nullptr)
{
if (exec_file_build_id->size == target_exec_file_build_id->size
&& memcmp (exec_file_build_id->data,
target_exec_file_build_id->data,
exec_file_build_id->size) == 0)
{
/* Match. */
return;
}
else
build_id_mismatch = true;
}
}
}
if (build_id_mismatch)
{
std::string exec_file_target (pid_exec_file);
/* In case the exec file is not local, exec_file_target has to point at
the target file system. */
if (is_target_filename (current_exec_file) && !target_filesystem_is_local ())
exec_file_target = TARGET_SYSROOT_PREFIX + exec_file_target;
warning
(_("Build ID mismatch between current exec-file %ps\n"
"and automatically determined exec-file %ps\n"
"exec-file-mismatch handling is currently \"%s\""),
styled_string (file_name_style.style (), current_exec_file),
styled_string (file_name_style.style (), exec_file_target.c_str ()),
exec_file_mismatch_names[exec_file_mismatch_mode]);
if (exec_file_mismatch_mode == exec_file_mismatch_ask)
{
symfile_add_flags add_flags = SYMFILE_MAINLINE;
if (from_tty)
{
add_flags |= SYMFILE_VERBOSE;
add_flags |= SYMFILE_ALWAYS_CONFIRM;
}
try
{
symbol_file_add_main (exec_file_target.c_str (), add_flags);
exec_file_attach (exec_file_target.c_str (), from_tty);
}
catch (gdb_exception_error &err)
{
warning (_("loading %ps %s"),
styled_string (file_name_style.style (),
exec_file_target.c_str ()),
err.message != NULL ? err.what () : "error");
}
}
}
}
/* See gdbcore.h. */
void
exec_file_locate_attach (int pid, int defer_bp_reset, int from_tty)
{
const char *exec_file_target;
symfile_add_flags add_flags = 0;
/* Do nothing if we already have an executable filename. */
if (get_exec_file (0) != NULL)
return;
/* Try to determine a filename from the process itself. */
exec_file_target = target_pid_to_exec_file (pid);
if (exec_file_target == NULL)
{
warning (_("No executable has been specified and target does not "
"support\n"
"determining executable automatically. "
"Try using the \"file\" command."));
return;
}
gdb::unique_xmalloc_ptr<char> exec_file_host
= exec_file_find (exec_file_target, NULL);
if (defer_bp_reset)
add_flags |= SYMFILE_DEFER_BP_RESET;
if (from_tty)
add_flags |= SYMFILE_VERBOSE;
/* Attempt to open the exec file. */
try_open_exec_file (exec_file_host.get (), current_inferior (), add_flags);
}
/* Set FILENAME as the new exec file.
This function is intended to be behave essentially the same
as exec_file_command, except that the latter will detect when
a target is being debugged, and will ask the user whether it
should be shut down first. (If the answer is "no", then the
new file is ignored.)
This file is used by exec_file_command, to do the work of opening
and processing the exec file after any prompting has happened.
And, it is used by child_attach, when the attach command was
given a pid but not a exec pathname, and the attach command could
figure out the pathname from the pid. (In this case, we shouldn't
ask the user whether the current target should be shut down --
we're supplying the exec pathname late for good reason.) */
void
exec_file_attach (const char *filename, int from_tty)
{
/* First, acquire a reference to the exec_bfd. We release
this at the end of the function; but acquiring it now lets the
BFD cache return it if this call refers to the same file. */
gdb_bfd_ref_ptr exec_bfd_holder
= gdb_bfd_ref_ptr::new_reference (current_program_space->exec_bfd ());
/* Remove any previous exec file. */
current_program_space->exec_close ();
/* Now open and digest the file the user requested, if any. */
if (!filename)
{
if (from_tty)
gdb_printf (_("No executable file now.\n"));
set_gdbarch_from_file (NULL);
}
else
{
int load_via_target = 0;
const char *scratch_pathname, *canonical_pathname;
int scratch_chan;
char **matching;
if (is_target_filename (filename))
{
if (target_filesystem_is_local ())
filename += strlen (TARGET_SYSROOT_PREFIX);
else
load_via_target = 1;
}
gdb::unique_xmalloc_ptr<char> canonical_storage, scratch_storage;
if (load_via_target)
{
/* gdb_bfd_fopen does not support "target:" filenames. */
if (write_files)
warning (_("writing into executable files is "
"not supported for %s sysroots"),
TARGET_SYSROOT_PREFIX);
scratch_pathname = filename;
scratch_chan = -1;
canonical_pathname = scratch_pathname;
}
else
{
scratch_chan = openp (getenv ("PATH"), OPF_TRY_CWD_FIRST,
filename, write_files ?
O_RDWR | O_BINARY : O_RDONLY | O_BINARY,
&scratch_storage);
#if defined(__GO32__) || defined(_WIN32) || defined(__CYGWIN__)
if (scratch_chan < 0)
{
int first_errno = errno;
char *exename = (char *) alloca (strlen (filename) + 5);
strcat (strcpy (exename, filename), ".exe");
scratch_chan = openp (getenv ("PATH"), OPF_TRY_CWD_FIRST,
exename, write_files ?
O_RDWR | O_BINARY
: O_RDONLY | O_BINARY,
&scratch_storage);
if (scratch_chan < 0)
errno = first_errno;
}
#endif
if (scratch_chan < 0)
perror_with_name (filename);
scratch_pathname = scratch_storage.get ();
/* gdb_bfd_open (and its variants) prefers canonicalized
pathname for better BFD caching. */
canonical_storage = gdb_realpath (scratch_pathname);
canonical_pathname = canonical_storage.get ();
}
gdb_bfd_ref_ptr temp;
if (write_files && !load_via_target)
temp = gdb_bfd_fopen (canonical_pathname, gnutarget,
FOPEN_RUB, scratch_chan);
else
temp = gdb_bfd_open (canonical_pathname, gnutarget, scratch_chan);
current_program_space->set_exec_bfd (std::move (temp));
if (!current_program_space->exec_bfd ())
{
error (_("\"%s\": could not open as an executable file: %s."),
scratch_pathname, bfd_errmsg (bfd_get_error ()));
}
/* gdb_realpath_keepfile resolves symlinks on the local
filesystem and so cannot be used for "target:" files. */
gdb_assert (current_program_space->exec_filename == nullptr);
if (load_via_target)
current_program_space->exec_filename
= (make_unique_xstrdup
(bfd_get_filename (current_program_space->exec_bfd ())));
else
current_program_space->exec_filename
= make_unique_xstrdup (gdb_realpath_keepfile
(scratch_pathname).c_str ());
if (!bfd_check_format_matches (current_program_space->exec_bfd (),
bfd_object, &matching))
{
/* Make sure to close exec_bfd, or else "run" might try to use
it. */
current_program_space->exec_close ();
error (_("\"%s\": not in executable format: %s"), scratch_pathname,
gdb_bfd_errmsg (bfd_get_error (), matching).c_str ());
}
std::vector<target_section> sections
= build_section_table (current_program_space->exec_bfd ());
current_program_space->ebfd_mtime
= bfd_get_mtime (current_program_space->exec_bfd ());
validate_files ();
set_gdbarch_from_file (current_program_space->exec_bfd ());
/* Add the executable's sections to the current address spaces'
list of sections. This possibly pushes the exec_ops
target. */
current_program_space->add_target_sections
(current_program_space->ebfd.get (), sections);
/* Tell display code (if any) about the changed file name. */
if (deprecated_exec_file_display_hook)
(*deprecated_exec_file_display_hook) (filename);
}
/* Are are loading the same executable? */
bfd *prev_bfd = exec_bfd_holder.get ();
bfd *curr_bfd = current_program_space->exec_bfd ();
bool reload_p = (((prev_bfd != nullptr) == (curr_bfd != nullptr))
&& (prev_bfd == nullptr
|| (strcmp (bfd_get_filename (prev_bfd),
bfd_get_filename (curr_bfd)) == 0)));
gdb::observers::executable_changed.notify (current_program_space, reload_p);
}
/* Process the first arg in ARGS as the new exec file.
Note that we have to explicitly ignore additional args, since we can
be called from file_command(), which also calls symbol_file_command()
which can take multiple args.
If ARGS is NULL, we just want to close the exec file. */
static void
exec_file_command (const char *args, int from_tty)
{
if (from_tty && target_has_execution ()
&& !query (_("A program is being debugged already.\n"
"Are you sure you want to change the file? ")))
error (_("File not changed."));
if (args)
{
/* Scan through the args and pick up the first non option arg
as the filename. */
gdb_argv built_argv (args);
char **argv = built_argv.get ();
for (; (*argv != NULL) && (**argv == '-'); argv++)
{;
}
if (*argv == NULL)
error (_("No executable file name was specified"));
gdb::unique_xmalloc_ptr<char> filename (tilde_expand (*argv));
exec_file_attach (filename.get (), from_tty);
}
else
exec_file_attach (NULL, from_tty);
}
/* Set both the exec file and the symbol file, in one command.
What a novelty. Why did GDB go through four major releases before this
command was added? */
static void
file_command (const char *arg, int from_tty)
{
/* FIXME, if we lose on reading the symbol file, we should revert
the exec file, but that's rough. */
exec_file_command (arg, from_tty);
symbol_file_command (arg, from_tty);
if (deprecated_file_changed_hook)
deprecated_file_changed_hook (arg);
}
/* Builds a section table, given args BFD, TABLE. */
std::vector<target_section>
build_section_table (struct bfd *some_bfd)
{
std::vector<target_section> table;
for (asection *asect : gdb_bfd_sections (some_bfd))
{
flagword aflag;
/* Check the section flags, but do not discard zero-length
sections, since some symbols may still be attached to this
section. For instance, we encountered on sparc-solaris 2.10
a shared library with an empty .bss section to which a symbol
named "_end" was attached. The address of this symbol still
needs to be relocated. */
aflag = bfd_section_flags (asect);
if (!(aflag & SEC_ALLOC))
continue;
table.emplace_back (bfd_section_vma (asect),
bfd_section_vma (asect) + bfd_section_size (asect),
asect);
}
return table;
}
/* Add the sections array defined by [SECTIONS..SECTIONS_END[ to the
current set of target sections. */
void
program_space::add_target_sections
(target_section_owner owner, const std::vector<target_section> &sections)
{
if (!sections.empty ())
{
for (const target_section &s : sections)
{
m_target_sections.push_back (s);
m_target_sections.back ().owner = owner;
}
scoped_restore_current_pspace_and_thread restore_pspace_thread;
/* If these are the first file sections we can provide memory
from, push the file_stratum target. Must do this in all
inferiors sharing the program space. */
for (inferior *inf : all_inferiors ())
{
if (inf->pspace != this)
continue;
if (inf->target_is_pushed (&exec_ops))
continue;
switch_to_inferior_no_thread (inf);
inf->push_target (&exec_ops);
}
}
}
/* Add the sections of OBJFILE to the current set of target sections. */
void
program_space::add_target_sections (struct objfile *objfile)
{
gdb_assert (objfile != nullptr);
/* Compute the number of sections to add. */
for (obj_section *osect : objfile->sections ())
{
if (bfd_section_size (osect->the_bfd_section) == 0)
continue;
m_target_sections.emplace_back (osect->addr (), osect->endaddr (),
osect->the_bfd_section, objfile);
}
}
/* Remove all target sections owned by OWNER.
OWNER must be the same value passed to add_target_sections. */
void
program_space::remove_target_sections (target_section_owner owner)
{
gdb_assert (owner.v () != nullptr);
auto it = std::remove_if (m_target_sections.begin (),
m_target_sections.end (),
[&] (target_section &sect)
{
return sect.owner.v () == owner.v ();
});
m_target_sections.erase (it, m_target_sections.end ());
/* If we don't have any more sections to read memory from,
remove the file_stratum target from the stack of each
inferior sharing the program space. */
if (m_target_sections.empty ())
{
scoped_restore_current_pspace_and_thread restore_pspace_thread;
for (inferior *inf : all_inferiors ())
{
if (inf->pspace != this)
continue;
switch_to_inferior_no_thread (inf);
inf->unpush_target (&exec_ops);
}
}
}
/* See exec.h. */
void
exec_on_vfork (inferior *vfork_child)
{
if (!vfork_child->pspace->target_sections ().empty ())
vfork_child->push_target (&exec_ops);
}
enum target_xfer_status
exec_read_partial_read_only (gdb_byte *readbuf, ULONGEST offset,
ULONGEST len, ULONGEST *xfered_len)
{
/* It's unduly pedantic to refuse to look at the executable for
read-only pieces; so do the equivalent of readonly regions aka
QTro packet. */
if (current_program_space->exec_bfd () != NULL)
{
asection *s;
bfd_size_type size;
bfd_vma vma;
for (s = current_program_space->exec_bfd ()->sections; s; s = s->next)
{
if ((s->flags & SEC_LOAD) == 0
|| (s->flags & SEC_READONLY) == 0)
continue;
vma = s->vma;
size = bfd_section_size (s);
if (vma <= offset && offset < (vma + size))
{
ULONGEST amt;
amt = (vma + size) - offset;
if (amt > len)
amt = len;
amt = bfd_get_section_contents (current_program_space->exec_bfd (), s,
readbuf, offset - vma, amt);
if (amt == 0)
return TARGET_XFER_EOF;
else
{
*xfered_len = amt;
return TARGET_XFER_OK;
}
}
}
}
/* Indicate failure to find the requested memory block. */
return TARGET_XFER_E_IO;
}
/* Return all read-only memory ranges found in the target section
table defined by SECTIONS and SECTIONS_END, starting at (and
intersected with) MEMADDR for LEN bytes. */
static std::vector<mem_range>
section_table_available_memory (CORE_ADDR memaddr, ULONGEST len,
const std::vector<target_section> &sections)
{
std::vector<mem_range> memory;
for (const target_section &p : sections)
{
if ((bfd_section_flags (p.the_bfd_section) & SEC_READONLY) == 0)
continue;
/* Copy the meta-data, adjusted. */
if (mem_ranges_overlap (p.addr, p.endaddr - p.addr, memaddr, len))
{
ULONGEST lo1, hi1, lo2, hi2;
lo1 = memaddr;
hi1 = memaddr + len;
lo2 = p.addr;
hi2 = p.endaddr;
CORE_ADDR start = std::max (lo1, lo2);
int length = std::min (hi1, hi2) - start;
memory.emplace_back (start, length);
}
}
return memory;
}
enum target_xfer_status
section_table_read_available_memory (gdb_byte *readbuf, ULONGEST offset,
ULONGEST len, ULONGEST *xfered_len)
{
const std::vector<target_section> *table
= target_get_section_table (current_inferior ()->top_target ());
std::vector<mem_range> available_memory
= section_table_available_memory (offset, len, *table);
normalize_mem_ranges (&available_memory);
for (const mem_range &r : available_memory)
{
if (mem_ranges_overlap (r.start, r.length, offset, len))
{
CORE_ADDR end;
enum target_xfer_status status;
/* Get the intersection window. */
end = std::min<CORE_ADDR> (offset + len, r.start + r.length);
gdb_assert (end - offset <= len);
if (offset >= r.start)
status = exec_read_partial_read_only (readbuf, offset,
end - offset,
xfered_len);
else
{
*xfered_len = r.start - offset;
status = TARGET_XFER_UNAVAILABLE;
}
return status;
}
}
*xfered_len = len;
return TARGET_XFER_UNAVAILABLE;
}
enum target_xfer_status
section_table_xfer_memory_partial (gdb_byte *readbuf, const gdb_byte *writebuf,
ULONGEST offset, ULONGEST len,
ULONGEST *xfered_len,
const std::vector<target_section> &sections,
gdb::function_view<bool
(const struct target_section *)> match_cb)
{
int res;
ULONGEST memaddr = offset;
ULONGEST memend = memaddr + len;
gdb_assert (len != 0);
for (const target_section &p : sections)
{
struct bfd_section *asect = p.the_bfd_section;
bfd *abfd = asect->owner;
if (match_cb != nullptr && !match_cb (&p))
continue; /* not the section we need. */
if (memaddr >= p.addr)
{
if (memend <= p.endaddr)
{
/* Entire transfer is within this section. */
if (writebuf)
res = bfd_set_section_contents (abfd, asect,
writebuf, memaddr - p.addr,
len);
else
res = bfd_get_section_contents (abfd, asect,
readbuf, memaddr - p.addr,
len);
if (res != 0)
{
*xfered_len = len;
return TARGET_XFER_OK;
}
else
return TARGET_XFER_EOF;
}
else if (memaddr >= p.endaddr)
{
/* This section ends before the transfer starts. */
continue;
}
else
{
/* This section overlaps the transfer. Just do half. */
len = p.endaddr - memaddr;
if (writebuf)
res = bfd_set_section_contents (abfd, asect,
writebuf, memaddr - p.addr,
len);
else
res = bfd_get_section_contents (abfd, asect,
readbuf, memaddr - p.addr,
len);
if (res != 0)
{
*xfered_len = len;
return TARGET_XFER_OK;
}
else
return TARGET_XFER_EOF;
}
}
}
return TARGET_XFER_EOF; /* We can't help. */
}
enum target_xfer_status
exec_target::xfer_partial (enum target_object object,
const char *annex, gdb_byte *readbuf,
const gdb_byte *writebuf,
ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
{
const std::vector<target_section> *table = target_get_section_table (this);
if (object == TARGET_OBJECT_MEMORY)
return section_table_xfer_memory_partial (readbuf, writebuf,
offset, len, xfered_len,
*table);
else
return TARGET_XFER_E_IO;
}
void
print_section_info (const std::vector<target_section> *t, bfd *abfd)
{
struct gdbarch *gdbarch = gdbarch_from_bfd (abfd);
/* FIXME: 16 is not wide enough when gdbarch_addr_bit > 64. */
int wid = gdbarch_addr_bit (gdbarch) <= 32 ? 8 : 16;
gdb_printf ("\t`%ps', ",
styled_string (file_name_style.style (),
bfd_get_filename (abfd)));
gdb_stdout->wrap_here (8);
gdb_printf (_("file type %s.\n"), bfd_get_target (abfd));
if (abfd == current_program_space->exec_bfd ())
{
/* gcc-3.4 does not like the initialization in
<p == t->sections_end>. */
bfd_vma displacement = 0;
bfd_vma entry_point;
bool found = false;
for (const target_section &p : *t)
{
struct bfd_section *psect = p.the_bfd_section;
if ((bfd_section_flags (psect) & (SEC_ALLOC | SEC_LOAD))
!= (SEC_ALLOC | SEC_LOAD))
continue;
if (bfd_section_vma (psect) <= abfd->start_address
&& abfd->start_address < (bfd_section_vma (psect)
+ bfd_section_size (psect)))
{
displacement = p.addr - bfd_section_vma (psect);
found = true;
break;
}
}
if (!found)
warning (_("Cannot find section for the entry point of %ps."),
styled_string (file_name_style.style (),
bfd_get_filename (abfd)));
entry_point = gdbarch_addr_bits_remove (gdbarch,
bfd_get_start_address (abfd)
+ displacement);
gdb_printf (_("\tEntry point: %s\n"),
paddress (gdbarch, entry_point));
}
for (const target_section &p : *t)
{
struct bfd_section *psect = p.the_bfd_section;
bfd *pbfd = psect->owner;
gdb_printf ("\t%s", hex_string_custom (p.addr, wid));
gdb_printf (" - %s", hex_string_custom (p.endaddr, wid));
/* FIXME: A format of "08l" is not wide enough for file offsets
larger than 4GB. OTOH, making it "016l" isn't desirable either
since most output will then be much wider than necessary. It
may make sense to test the size of the file and choose the
format string accordingly. */
/* FIXME: i18n: Need to rewrite this sentence. */
if (info_verbose)
gdb_printf (" @ %s",
hex_string_custom (psect->filepos, 8));
gdb_printf (" is %s", bfd_section_name (psect));
if (pbfd != abfd)
gdb_printf (" in %ps",
styled_string (file_name_style.style (),
bfd_get_filename (pbfd)));
gdb_printf ("\n");
}
}
void
exec_target::files_info ()
{
if (current_program_space->exec_bfd ())
print_section_info (&current_program_space->target_sections (),
current_program_space->exec_bfd ());
else
gdb_puts (_("\t<no file loaded>\n"));
}
static void
set_section_command (const char *args, int from_tty)
{
const char *secname;
if (args == 0)
error (_("Must specify section name and its virtual address"));
/* Parse out section name. */
for (secname = args; !isspace (*args); args++);
unsigned seclen = args - secname;
/* Parse out new virtual address. */
CORE_ADDR secaddr = parse_and_eval_address (args);
for (target_section &p : current_program_space->target_sections ())
{
if (!strncmp (secname, bfd_section_name (p.the_bfd_section), seclen)
&& bfd_section_name (p.the_bfd_section)[seclen] == '\0')
{
long offset = secaddr - p.addr;
p.addr += offset;
p.endaddr += offset;
if (from_tty)
exec_ops.files_info ();
return;
}
}
std::string secprint (secname, seclen);
error (_("Section %s not found"), secprint.c_str ());
}
/* If we can find a section in FILENAME with BFD index INDEX, adjust
it to ADDRESS. */
void
exec_set_section_address (const char *filename, int index, CORE_ADDR address)
{
for (target_section &p : current_program_space->target_sections ())
{
if (filename_cmp (filename,
bfd_get_filename (p.the_bfd_section->owner)) == 0
&& index == p.the_bfd_section->index)
{
p.endaddr += address - p.addr;
p.addr = address;
}
}
}
bool
exec_target::has_memory ()
{
/* We can provide memory if we have any file/target sections to read
from. */
return !current_program_space->target_sections ().empty ();
}
gdb::unique_xmalloc_ptr<char>
exec_target::make_corefile_notes (bfd *obfd, int *note_size)
{
error (_("Can't create a corefile"));
}
int
exec_target::find_memory_regions (find_memory_region_ftype func, void *data)
{
return objfile_find_memory_regions (this, func, data);
}
void _initialize_exec ();
void
_initialize_exec ()
{
struct cmd_list_element *c;
c = add_cmd ("file", class_files, file_command, _("\
Use FILE as program to be debugged.\n\
It is read for its symbols, for getting the contents of pure memory,\n\
and it is the program executed when you use the `run' command.\n\
If FILE cannot be found as specified, your execution directory path\n\
($PATH) is searched for a command of that name.\n\
No arg means to have no executable file and no symbols."), &cmdlist);
set_cmd_completer (c, filename_completer);
c = add_cmd ("exec-file", class_files, exec_file_command, _("\
Use FILE as program for getting contents of pure memory.\n\
If FILE cannot be found as specified, your execution directory path\n\
is searched for a command of that name.\n\
No arg means have no executable file."), &cmdlist);
set_cmd_completer (c, filename_completer);
add_com ("section", class_files, set_section_command, _("\
Change the base address of section SECTION of the exec file to ADDR.\n\
This can be used if the exec file does not contain section addresses,\n\
(such as in the a.out format), or when the addresses specified in the\n\
file itself are wrong. Each section must be changed separately. The\n\
``info files'' command lists all the sections and their addresses."));
add_setshow_boolean_cmd ("write", class_support, &write_files, _("\
Set writing into executable and core files."), _("\
Show writing into executable and core files."), NULL,
NULL,
show_write_files,
&setlist, &showlist);
add_setshow_enum_cmd ("exec-file-mismatch", class_support,
exec_file_mismatch_names,
&exec_file_mismatch,
_("\
Set exec-file-mismatch handling (ask|warn|off)."),
_("\
Show exec-file-mismatch handling (ask|warn|off)."),
_("\
Specifies how to handle a mismatch between the current exec-file\n\
loaded by GDB and the exec-file automatically determined when attaching\n\
to a process:\n\n\
ask - warn the user and ask whether to load the determined exec-file.\n\
warn - warn the user, but do not change the exec-file.\n\
off - do not check for mismatch.\n\
\n\
GDB detects a mismatch by comparing the build IDs of the files.\n\
If the user confirms loading the determined exec-file, then its symbols\n\
will be loaded as well."),
set_exec_file_mismatch_command,
show_exec_file_mismatch_command,
&setlist, &showlist);
add_target (exec_target_info, exec_target_open, filename_completer);
}
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