152 lines
5.2 KiB
Diff
152 lines
5.2 KiB
Diff
From 3bd7e5b7ee5ea0b3bbb4030ca841f66faad74f0f Mon Sep 17 00:00:00 2001
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From: Sergio Durigan Junior <sergiodj@redhat.com>
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Date: Fri, 21 Aug 2015 18:28:07 -0400
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Subject: [PATCH 2/4] Catching errors on probes-based dynamic linker interface
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This patch is intended to make the interaction between the
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probes-based dynamic linker interface and the SystemTap SDT probe code
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on GDB more robust. It does that by wrapping the calls to the probe
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API with TRY...CATCH'es, so that any exception thrown will be caught
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and handled properly.
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The idea for this patch came from
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<https://bugzilla.redhat.com/show_bug.cgi?id=1196181>, which is a bug
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initially filed against Fedora GDB (but now under Fedora GLIBC). This
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bug happens on armhfp (although it could happen on other targets as
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well), and is triggered because GCC generates a strange argument for
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one of the probes used by GDB in the dynamic linker interface. As can
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be seen in the bug, this argument is "-4@.L1052".
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I don't want to discuss the reasons for this argument to be there
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(this discussion belongs to the bug, or to another thread), but GDB
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could definitely do a better error handling here. Currently, one sees
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the following message when there is an error in the probes-based
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dynamic linker interface:
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(gdb) run
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Starting program: /bin/inferior
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warning: Probes-based dynamic linker interface failed.
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Reverting to original interface.
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Cannot parse expression `.L976 4@r4'.
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(gdb)
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Which means that one needs to explicitly issue a "continue" command to
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make GDB continue running the inferior, even though this error is not
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fatal and GDB will fallback to the old interface automatically.
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This is where this patch helps: it makes GDB still print the necessary
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warnings or error messages, but it *also* does not stop the inferior
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unnecessarily.
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I have tested this patch on the systems where this error happens, but
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I could not come up with a way to create a testcase for it.
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Nevertheless, it should be straightforward to see that this patch does
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improve the current situation.
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gdb/ChangeLog:
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2015-09-01 Sergio Durigan Junior <sergiodj@redhat.com>
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* solib-svr4.c (solib_event_probe_action): Call
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get_probe_argument_count using TRY...CATCH.
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(svr4_handle_solib_event): Likewise, for evaluate_probe_argument.
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---
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gdb/ChangeLog | 6 ++++++
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gdb/solib-svr4.c | 43 ++++++++++++++++++++++++++++++++++++++++---
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2 files changed, 46 insertions(+), 3 deletions(-)
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Index: gdb-7.9.1/gdb/solib-svr4.c
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===================================================================
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--- gdb-7.9.1.orig/gdb/solib-svr4.c
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+++ gdb-7.9.1/gdb/solib-svr4.c
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@@ -1769,8 +1769,9 @@ static enum probe_action
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solib_event_probe_action (struct probe_and_action *pa)
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{
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enum probe_action action;
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- unsigned probe_argc;
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+ unsigned probe_argc = 0;
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struct frame_info *frame = get_current_frame ();
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+ volatile struct gdb_exception ex;
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action = pa->action;
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if (action == DO_NOTHING || action == PROBES_INTERFACE_FAILED)
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@@ -1783,7 +1784,23 @@ solib_event_probe_action (struct probe_a
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arg0: Lmid_t lmid (mandatory)
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arg1: struct r_debug *debug_base (mandatory)
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arg2: struct link_map *new (optional, for incremental updates) */
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- probe_argc = get_probe_argument_count (pa->probe, frame);
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+ TRY_CATCH (ex, RETURN_MASK_ERROR)
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+ {
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+ probe_argc = get_probe_argument_count (pa->probe, frame);
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+ }
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+
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+ if (ex.reason < 0)
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+ {
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+ exception_print (gdb_stderr, ex);
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+ probe_argc = 0;
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+ }
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+
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+ /* If get_probe_argument_count throws an exception, probe_argc will
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+ be set to zero. However, if pa->probe does not have arguments,
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+ then get_probe_argument_count will succeed but probe_argc will
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+ also be zero. Both cases happen because of different things, but
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+ they are treated equally here: action will be set to
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+ PROBES_INTERFACE_FAILED. */
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if (probe_argc == 2)
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action = FULL_RELOAD;
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else if (probe_argc < 2)
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@@ -1889,10 +1906,11 @@ svr4_handle_solib_event (void)
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struct probe_and_action *pa;
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enum probe_action action;
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struct cleanup *old_chain, *usm_chain;
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- struct value *val;
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+ struct value *val = NULL;
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CORE_ADDR pc, debug_base, lm = 0;
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int is_initial_ns;
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struct frame_info *frame = get_current_frame ();
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+ volatile struct gdb_exception ex;
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/* Do nothing if not using the probes interface. */
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if (info->probes_table == NULL)
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@@ -1937,7 +1955,17 @@ svr4_handle_solib_event (void)
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usm_chain = make_cleanup (resume_section_map_updates_cleanup,
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current_program_space);
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- val = evaluate_probe_argument (pa->probe, 1, frame);
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+ TRY_CATCH (ex, RETURN_MASK_ERROR)
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+ {
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+ val = evaluate_probe_argument (pa->probe, 1, frame);
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+ }
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+
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+ if (ex.reason < 0)
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+ {
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+ exception_print (gdb_stderr, ex);
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+ val = NULL;
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+ }
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+
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if (val == NULL)
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{
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do_cleanups (old_chain);
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@@ -1968,7 +1996,20 @@ svr4_handle_solib_event (void)
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if (action == UPDATE_OR_RELOAD)
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{
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- val = evaluate_probe_argument (pa->probe, 2, frame);
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+ volatile struct gdb_exception ex;
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+
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+ TRY_CATCH (ex, RETURN_MASK_ERROR)
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+ {
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+ val = evaluate_probe_argument (pa->probe, 2, frame);
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+ }
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+
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+ if (ex.reason < 0)
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+ {
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+ exception_print (gdb_stderr, ex);
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+ do_cleanups (old_chain);
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+ return;
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+ }
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+
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if (val != NULL)
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lm = value_as_address (val);
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