170 lines
6.3 KiB
Diff
170 lines
6.3 KiB
Diff
From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
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From: Keith Seitz <keiths@redhat.com>
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Date: Tue, 28 Jul 2020 09:32:50 -0400
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Subject: gdb-rhbz1842691-corefile-mem-access-12of15.patch
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;; Add new command "maint print core-file-backed-mappings"
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;; Kevin Buettner, RH BZ 1842961
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Author: Kevin Buettner <kevinb@redhat.com>
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Date: Fri Jul 3 21:55:51 2020 -0700
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Add new command "maint print core-file-backed-mappings"
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I wrote a read_core_file_mappings method for FreeBSD and then registered
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this gdbarch method. I saw some strange behavior while testing it and
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wanted a way to make sure that mappings were being correctly loaded
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into corelow.c, so I wrote the new command which is the topic of this
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commit. I think it might be occasionally useful for debugging strange
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corefile behavior.
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With regard to FreeBSD, my work isn't ready yet. Unlike Linux,
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FreeBSD puts all mappings into its core file note. And, unlike Linux,
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it doesn't dump load segments which occupy no space in the file. So
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my (perhaps naive) implementation of a FreeBSD read_core_file_mappings
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didn't work all that well: I saw more failures in the corefile2.exp
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tests than without it. I think it should be possible to make FreeBSD
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work as well as Linux, but it will require doing something with all of
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the mappings, not just the file based mappings that I was considering.
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In the v4 series, Pedro asked the following:
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I don't understand what this command provides that "info proc
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mappings" doesn't? Can you give an example of when you'd use this
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command over "info proc mappings" ?
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On Linux, "info proc mappings" and "maint print core-file-backed-mappings"
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will produce similar, possibly identical, output. This need not be
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the case for other OSes. E.g. on FreeBSD, had I finished the
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implementation, the output from these commands would have been very
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different. The FreeBSD "info proc mappings" command would show
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additional (non-file-backed) mappings in addition to at least one
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additional field (memory permissions) for each mapping.
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As noted earlier, I was seeing some unexpected behavior while working
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on the FreeBSD implementation and wanted to be certain that the
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mappings were being correctly loaded by corelow.c. "info proc
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mappings" prints the core file mappings, but doesn't tell us anything
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about whether they've been loaded by corelow.c This new maintenance
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command directly interrogates the data structures and prints the
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values found there.
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gdb/ChangeLog:
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* corelow.c (gdbcmd.h): Include.
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(core_target::info_proc_mappings): New method.
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(get_current_core_target): New function.
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(maintenance_print_core_file_backed_mappings): New function.
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(_initialize_corelow): Add core-file-backed-mappings to
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"maint print" commands.
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diff --git a/gdb/corelow.c b/gdb/corelow.c
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--- a/gdb/corelow.c
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+++ b/gdb/corelow.c
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@@ -118,6 +118,9 @@ public:
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const char *human_name,
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bool required);
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+ /* See definition. */
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+ void info_proc_mappings (struct gdbarch *gdbarch);
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+
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private: /* per-core data */
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/* The core's section table. Note that these target sections are
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@@ -1292,6 +1295,86 @@ core_target::info_proc (const char *args, enum info_proc_what request)
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return true;
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}
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+/* Get a pointer to the current core target. If not connected to a
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+ core target, return NULL. */
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+
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+static core_target *
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+get_current_core_target ()
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+{
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+ target_ops *proc_target = find_target_at (process_stratum);
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+ return dynamic_cast<core_target *> (proc_target);
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+}
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+
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+/* Display file backed mappings from core file. */
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+
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+void
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+core_target::info_proc_mappings (struct gdbarch *gdbarch)
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+{
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+ if (m_core_file_mappings.sections != m_core_file_mappings.sections_end)
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+ {
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+ printf_filtered (_("Mapped address spaces:\n\n"));
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+ if (gdbarch_addr_bit (gdbarch) == 32)
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+ {
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+ printf_filtered ("\t%10s %10s %10s %10s %s\n",
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+ "Start Addr",
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+ " End Addr",
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+ " Size", " Offset", "objfile");
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+ }
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+ else
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+ {
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+ printf_filtered (" %18s %18s %10s %10s %s\n",
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+ "Start Addr",
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+ " End Addr",
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+ " Size", " Offset", "objfile");
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+ }
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+ }
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+
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+ for (const struct target_section *tsp = m_core_file_mappings.sections;
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+ tsp < m_core_file_mappings.sections_end;
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+ tsp++)
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+ {
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+ ULONGEST start = tsp->addr;
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+ ULONGEST end = tsp->endaddr;
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+ ULONGEST file_ofs = tsp->the_bfd_section->filepos;
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+ const char *filename = bfd_get_filename (tsp->the_bfd_section->owner);
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+
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+ if (gdbarch_addr_bit (gdbarch) == 32)
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+ printf_filtered ("\t%10s %10s %10s %10s %s\n",
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+ paddress (gdbarch, start),
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+ paddress (gdbarch, end),
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+ hex_string (end - start),
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+ hex_string (file_ofs),
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+ filename);
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+ else
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+ printf_filtered (" %18s %18s %10s %10s %s\n",
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+ paddress (gdbarch, start),
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+ paddress (gdbarch, end),
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+ hex_string (end - start),
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+ hex_string (file_ofs),
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+ filename);
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+ }
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+}
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+
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+/* Implement "maintenance print core-file-backed-mappings" command.
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+
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+ If mappings are loaded, the results should be similar to the
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+ mappings shown by "info proc mappings". This command is mainly a
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+ debugging tool for GDB developers to make sure that the expected
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+ mappings are present after loading a core file. For Linux, the
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+ output provided by this command will be very similar (if not
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+ identical) to that provided by "info proc mappings". This is not
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+ necessarily the case for other OSes which might provide
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+ more/different information in the "info proc mappings" output. */
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+
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+static void
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+maintenance_print_core_file_backed_mappings (const char *args, int from_tty)
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+{
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+ core_target *targ = get_current_core_target ();
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+ if (targ != nullptr)
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+ targ->info_proc_mappings (targ->core_gdbarch ());
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+}
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+
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+void _initialize_corelow ();
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void
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_initialize_corelow (void)
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{
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@@ -1303,4 +1386,8 @@ Set whether CORE-FILE loads the build-id associated files automatically."), _("\
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Show whether CORE-FILE loads the build-id associated files automatically."),
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NULL, NULL, NULL,
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&setlist, &showlist);
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+ add_cmd ("core-file-backed-mappings", class_maintenance,
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+ maintenance_print_core_file_backed_mappings,
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+ _("Print core file's file-backed mappings"),
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+ &maintenanceprintlist);
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}
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