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gdb: introduce ability to disable frame unwinders

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Sometimes, in the GDB testsuite, we want to test the ability of specific
unwinders to handle some piece of code. Usually this is done by trying
to outsmart GDB, or by coercing the compiler to remove information that
GDB would rely on.  Both approaches have problems as GDB gets smarter
with time, and that compilers might differ in version and behavior, or
simply introduce new useful information. This was requested back in 2003
in PR backtrace/8434.

To improve our ability to thoroughly test GDB, this patch introduces a
new maintenance command that allows a user to disable some unwinders,
based on either the name of the unwinder or on its class. With this
change, it will now be possible for GDB to not find any frame unwinders
for a given frame, which would previously cause GDB to assert. GDB will
now check if any frame unwinder has been disabled, and if some has, it
will just error out instead of asserting.

Unwinders can be disabled or re-enabled in 3 different ways:
* Disabling/enabling all at once (using '-all').
* By specifying an unwinder class to be disabled (option '-class').
* By specifying the name of an unwinder (option '-name').

If you give no options to the command, GDB assumes the input is an
unwinder class. '-class' would make no difference if used, is just here
for completeness.

This command is meant to be used once the inferior is already at the
desired location for the test. An example session would be:

(gdb) start
Temporary breakpoint 1, main () at omp.c:17
17          func();
(gdb) maint frame-unwinder disable ARCH
(gdb) bt
\#0  main () at omp.c:17
(gdb) maint frame-unwinder enable ARCH
(gdb) cont
Continuing.

This commit is a more generic version of commit 3c3bb0580b,
and so, based on the final paragraph of the commit message:
    gdb: Add switch to disable DWARF stack unwinders
<...>
    If in the future we find ourselves adding more switches to disable
    different unwinders, then we should probably move to a more generic
    solution, and remove this patch.
this patch also reverts 3c3bb0580b

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=8434
Co-Authored-By: Andrew Burgess <aburgess@redhat.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Approved-By: Andrew Burgess <aburgess@redhat.com>

temp adding completion
This commit is contained in:
Guinevere Larsen
2024-03-14 16:14:28 +01:00
parent 1239e7cf37
commit b49f56d0aa
11 changed files with 466 additions and 85 deletions
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266
gdb/frame-unwind.c
View File

@@ -29,6 +29,7 @@
#include "gdbarch.h"
#include "dwarf2/frame-tailcall.h"
#include "cli/cli-cmds.h"
#include "cli/cli-option.h"
#include "inferior.h"
/* Conversion list between the enum for frame_unwind_class and
@@ -39,6 +40,7 @@ static const char * unwind_class_conversion[] =
"EXTENSION",
"DEBUGINFO",
"ARCH",
nullptr
};
/* Default sniffers, that must always be the first in the unwinder list,
@@ -90,6 +92,20 @@ frame_unwinder_class_str (frame_unwind_class uclass)
return unwind_class_conversion[uclass];
}
/* Case insensitive search for a frame_unwind_class based on the given
string. */
static enum frame_unwind_class
str_to_frame_unwind_class (const char *class_str)
{
for (int i = 0; i < UNWIND_CLASS_NUMBER; i++)
{
if (strcasecmp (unwind_class_conversion[i], class_str) == 0)
return (frame_unwind_class) i;
}
error (_("Unknown frame unwind class: %s"), class_str);
}
void
frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
const struct frame_unwind *unwinder)
@@ -176,27 +192,46 @@ frame_unwind_find_by_frame (const frame_info_ptr &this_frame, void **this_cache)
FRAME_SCOPED_DEBUG_ENTER_EXIT;
frame_debug_printf ("this_frame=%d", frame_relative_level (this_frame));
const struct frame_unwind *unwinder_from_target;
/* If we see a disabled unwinder, we assume some test is being run on
GDB, and we don't want to internal_error at the end of this function. */
bool seen_disabled_unwinder = false;
/* Lambda to factor out the logic of checking if an unwinder is enabled,
testing it and otherwise recording if we saw a disable unwinder. */
auto test_unwinder = [&] (const struct frame_unwind *unwinder)
{
if (unwinder == nullptr)
return false;
unwinder_from_target = target_get_unwinder ();
if (unwinder_from_target != NULL
&& frame_unwind_try_unwinder (this_frame, this_cache,
unwinder_from_target))
if (!unwinder->enabled ())
{
seen_disabled_unwinder = true;
return false;
}
return frame_unwind_try_unwinder (this_frame,
this_cache,
unwinder);
};
if (test_unwinder (target_get_unwinder ()))
return;
unwinder_from_target = target_get_tailcall_unwinder ();
if (unwinder_from_target != NULL
&& frame_unwind_try_unwinder (this_frame, this_cache,
unwinder_from_target))
if (test_unwinder (target_get_tailcall_unwinder ()))
return;
struct gdbarch *gdbarch = get_frame_arch (this_frame);
std::vector<const frame_unwind *> &table = get_frame_unwind_table (gdbarch);
for (const auto &unwinder : table)
if (frame_unwind_try_unwinder (this_frame, this_cache, unwinder))
return;
{
if (test_unwinder (unwinder))
return;
}
internal_error (_("frame_unwind_find_by_frame failed"));
if (seen_disabled_unwinder)
error (_("Required frame unwinder may have been disabled"
", see 'maint info frame-unwinders'"));
else
internal_error (_("frame_unwind_find_by_frame failed"));
}
/* A default frame sniffer which always accepts the frame. Used by
@@ -407,10 +442,11 @@ maintenance_info_frame_unwinders (const char *args, int from_tty)
std::vector<const frame_unwind *> &table = get_frame_unwind_table (gdbarch);
ui_out *uiout = current_uiout;
ui_out_emit_table table_emitter (uiout, 3, -1, "FrameUnwinders");
ui_out_emit_table table_emitter (uiout, 4, -1, "FrameUnwinders");
uiout->table_header (27, ui_left, "name", "Name");
uiout->table_header (25, ui_left, "type", "Type");
uiout->table_header (9, ui_left, "class", "Class");
uiout->table_header (8, ui_left, "enabled", "Enabled");
uiout->table_body ();
for (const auto &unwinder : table)
@@ -420,10 +456,167 @@ maintenance_info_frame_unwinders (const char *args, int from_tty)
uiout->field_string ("type", frame_type_str (unwinder->type ()));
uiout->field_string ("class", frame_unwinder_class_str (
unwinder->unwinder_class ()));
uiout->field_string ("enabled", unwinder->enabled () ? "Y" : "N");
uiout->text ("\n");
}
}
/* Options for disabling frame unwinders. */
struct maint_frame_unwind_options
{
std::string unwinder_name;
const char *unwinder_class = nullptr;
bool all = false;
};
static const gdb::option::option_def maint_frame_unwind_opt_defs[] = {
gdb::option::flag_option_def<maint_frame_unwind_options> {
"all",
[] (maint_frame_unwind_options *opt) { return &opt->all; },
N_("Change the state of all unwinders")
},
gdb::option::string_option_def<maint_frame_unwind_options> {
"name",
[] (maint_frame_unwind_options *opt) { return &opt->unwinder_name; },
nullptr,
N_("The name of the unwinder to have its state changed")
},
gdb::option::enum_option_def<maint_frame_unwind_options> {
"class",
unwind_class_conversion,
[] (maint_frame_unwind_options *opt) { return &opt->unwinder_class; },
nullptr,
N_("The class of unwinders to have their states changed")
}
};
static inline gdb::option::option_def_group
make_frame_unwind_enable_disable_options (maint_frame_unwind_options *opts)
{
return {{maint_frame_unwind_opt_defs}, opts};
}
/* Helper function to both enable and disable frame unwinders.
If ENABLE is true, this call will be enabling unwinders,
otherwise the unwinders will be disabled. */
static void
enable_disable_frame_unwinders (const char *args, int from_tty, bool enable)
{
if (args == nullptr)
{
if (enable)
error (_("Specify which frame unwinder(s) should be enabled"));
else
error (_("Specify which frame unwinder(s) should be disabled"));
}
struct gdbarch* gdbarch = current_inferior ()->arch ();
std::vector<const frame_unwind *> unwinder_list
= get_frame_unwind_table (gdbarch);
maint_frame_unwind_options opts;
gdb::option::process_options
(&args, gdb::option::PROCESS_OPTIONS_UNKNOWN_IS_ERROR,
make_frame_unwind_enable_disable_options (&opts));
if ((opts.all && !opts.unwinder_name.empty ())
|| (opts.all && opts.unwinder_class != nullptr)
|| (!opts.unwinder_name.empty () && opts.unwinder_class != nullptr))
error (_("Options are mutually exclusive"));
/* First see if the user wants to change all unwinders. */
if (opts.all)
{
for (const frame_unwind *u : unwinder_list)
u->set_enabled (enable);
reinit_frame_cache ();
return;
}
/* If user entered a specific unwinder name, handle it here. If the
unwinder is already at the expected state, error out. */
if (!opts.unwinder_name.empty ())
{
bool did_something = false;
for (const frame_unwind *unwinder : unwinder_list)
{
if (strcasecmp (unwinder->name (),
opts.unwinder_name.c_str ()) == 0)
{
if (unwinder->enabled () == enable)
{
if (unwinder->enabled ())
error (_("unwinder %s is already enabled"),
unwinder->name ());
else
error (_("unwinder %s is already disabled"),
unwinder->name ());
}
unwinder->set_enabled (enable);
did_something = true;
break;
}
}
if (!did_something)
error (_("couldn't find unwinder named %s"),
opts.unwinder_name.c_str ());
}
else
{
if (opts.unwinder_class == nullptr)
opts.unwinder_class = args;
enum frame_unwind_class dclass = str_to_frame_unwind_class
(opts.unwinder_class);
for (const frame_unwind *unwinder: unwinder_list)
{
if (unwinder->unwinder_class () == dclass)
unwinder->set_enabled (enable);
}
}
reinit_frame_cache ();
}
/* Completer for the "maint frame-unwinder enable|disable" commands. */
static void
enable_disable_frame_unwinders_completer (struct cmd_list_element *ignore,
completion_tracker &tracker,
const char *text,
const char * /*word*/)
{
maint_frame_unwind_options opts;
const auto group = make_frame_unwind_enable_disable_options (&opts);
const char *start = text;
if (gdb::option::complete_options
(tracker, &text, gdb::option::PROCESS_OPTIONS_UNKNOWN_IS_OPERAND, group))
return;
/* Only complete a class name as a stand-alone operand when no options
are given. */
if (start == text)
complete_on_enum (tracker, unwind_class_conversion, text, text);
return;
}
/* Implement "maint frame-unwinder disable" command. */
static void
maintenance_disable_frame_unwinders (const char *args, int from_tty)
{
enable_disable_frame_unwinders (args, from_tty, false);
}
/* Implement "maint frame-unwinder enable" command. */
static void
maintenance_enable_frame_unwinders (const char *args, int from_tty)
{
enable_disable_frame_unwinders (args, from_tty, true);
}
void _initialize_frame_unwind ();
void
_initialize_frame_unwind ()
@@ -436,4 +629,51 @@ _initialize_frame_unwind ()
List the frame unwinders currently in effect.\n\
Unwinders are listed starting with the highest priority."),
&maintenanceinfolist);
/* Add "maint frame-unwinder disable/enable". */
static struct cmd_list_element *maint_frame_unwinder;
add_basic_prefix_cmd ("frame-unwinder", class_maintenance,
_("Commands handling frame unwinders."),
&maint_frame_unwinder, 0, &maintenancelist);
cmd_list_element *c
= add_cmd ("disable", class_maintenance, maintenance_disable_frame_unwinders,
_("\
Disable one or more frame unwinder(s).\n\
Usage: maint frame-unwinder disable [-all | -name NAME | [-class] CLASS]\n\
\n\
These are the meanings of the options:\n\
\t-all - All available unwinders will be disabled\n\
\t-name - NAME is the exact name of the frame unwinder to be disabled\n\
\t-class - CLASS is the class of unwinders to be disabled. Valid classes are:\n\
\t\tGDB - Unwinders added by GDB core;\n\
\t\tEXTENSION - Unwinders added by extension languages;\n\
\t\tDEBUGINFO - Unwinders that handle debug information;\n\
\t\tARCH - Unwinders that use architecture-specific information;\n\
\n\
UNWINDER and NAME are case insensitive."),
&maint_frame_unwinder);
set_cmd_completer_handle_brkchars (c,
enable_disable_frame_unwinders_completer);
c =
add_cmd ("enable", class_maintenance, maintenance_enable_frame_unwinders,
_("\
Enable one or more frame unwinder(s).\n\
Usage: maint frame-unwinder enable [-all | -name NAME | [-class] CLASS]\n\
\n\
These are the meanings of the options:\n\
\t-all - All available unwinders will be enabled\n\
\t-name - NAME is the exact name of the frame unwinder to be enabled\n\
\t-class - CLASS is the class of unwinders to be enabled. Valid classes are:\n\
\t\tGDB - Unwinders added by GDB core;\n\
\t\tEXTENSION - Unwinders added by extension languages;\n\
\t\tDEBUGINFO - Unwinders that handle debug information;\n\
\t\tARCH - Unwinders that use architecture-specific information;\n\
\n\
UNWINDER and NAME are case insensitive."),
&maint_frame_unwinder);
set_cmd_completer_handle_brkchars (c,
enable_disable_frame_unwinders_completer);
}