149 lines
4.5 KiB
Diff
149 lines
4.5 KiB
Diff
From 0f8f51e98c7f643b8ce32bc6f6d621ce902d7a66 Mon Sep 17 00:00:00 2001
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From: Tom de Vries <tdevries@suse.de>
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Date: Thu, 28 Sep 2023 20:17:33 +0200
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Subject: [PATCH 2/6] [gdb/tui] Fix segfault in tui_find_disassembly_address
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PR29040 describes a FAIL for test-case gdb.threads/next-fork-other-thread.exp
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and target board unix/-m32.
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The FAIL happens due to the test executable running into an assert, which is
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caused by a forked child segfaulting, like so:
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...
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Program terminated with signal SIGSEGV, Segmentation fault.
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#0 0x00000000 in ?? ()
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...
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I tried to reproduce the segfault with exec next-fork-other-thread-fork, using
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TUI layout asm.
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I set a breakpoint at fork and ran to the breakpoint, and somewhere during the
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following session I ran into a gdb segfault here in
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tui_find_disassembly_address:
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...
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/* Disassemble forward. */
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next_addr = tui_disassemble (gdbarch, asm_lines, new_low, max_lines);
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last_addr = asm_lines.back ().addr;
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...
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due to asm_lines being empty after the call to tui_disassemble, while
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asm_lines.back () assumes that it's not empty.
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I have not been able to reproduce that segfault in that original setting, I'm
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not sure of the exact scenario (though looking back it probably involved
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"set detach-on-fork off").
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What likely happened is that I managed to reproduce PR29040, and TUI (attempted
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to) display the disassembly for address 0, which led to the gdb segfault.
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When gdb_print_insn encounters an insn it cannot print because it can't read
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the memory, it throws a MEMORY_ERROR that is caught by tui_disassemble.
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The specific bit that causes the gdb segfault is that if gdb_print_insn throws
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a MEMORY_ERROR for the first insn in tui_disassemble, it returns an empty
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asm_lines.
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FWIW, I did manage to reproduce the gdb segfault as follows:
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...
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$ gdb -q \
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-iex "set pagination off" \
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/usr/bin/rustc \
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-ex "set breakpoint pending on" \
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-ex "b dl_main" \
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-ex run \
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-ex "up 4" \
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-ex "layout asm" \
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-ex "print \$pc"
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...
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<TUI>
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...
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$1 = (void (*)()) 0x1
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(gdb)
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...
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Now press <up>, and the segfault triggers.
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Fix the segfault by handling asm_lines.empty () results of tui_disassemble in
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tui_find_disassembly_address.
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I've written a unit test that exercises this scenario.
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Tested on x86_64-linux.
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Reviewed-by: Kevin Buettner <kevinb@redhat.com>
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PR tui/30823
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Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30823
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---
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gdb/tui/tui-disasm.c | 39 +++++++++++++++++++++++++++++++++++++++
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1 file changed, 39 insertions(+)
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diff --git a/gdb/tui/tui-disasm.c b/gdb/tui/tui-disasm.c
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index f0b55769d71..03c78aa1291 100644
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--- a/gdb/tui/tui-disasm.c
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+++ b/gdb/tui/tui-disasm.c
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@@ -41,6 +41,8 @@
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#include "objfiles.h"
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#include "cli/cli-style.h"
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#include "tui/tui-location.h"
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+#include "gdbsupport/selftest.h"
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+#include "inferior.h"
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#include "gdb_curses.h"
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@@ -203,6 +205,8 @@ tui_find_disassembly_address (struct gdbarch *gdbarch, CORE_ADDR pc, int from)
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instruction fails to disassemble we will take the address of the
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previous instruction that did disassemble as the result. */
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tui_disassemble (gdbarch, asm_lines, pc, max_lines + 1);
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+ if (asm_lines.empty ())
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+ return pc;
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new_low = asm_lines.back ().addr;
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}
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else
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@@ -244,6 +248,8 @@ tui_find_disassembly_address (struct gdbarch *gdbarch, CORE_ADDR pc, int from)
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/* Disassemble forward. */
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next_addr = tui_disassemble (gdbarch, asm_lines, new_low, max_lines);
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+ if (asm_lines.empty ())
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+ break;
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last_addr = asm_lines.back ().addr;
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/* If disassembling from the current value of NEW_LOW reached PC
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@@ -522,3 +528,36 @@ tui_disasm_window::display_start_addr (struct gdbarch **gdbarch_p,
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*gdbarch_p = m_gdbarch;
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*addr_p = m_start_line_or_addr.u.addr;
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}
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+
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+#if GDB_SELF_TEST
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+namespace selftests {
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+namespace tui {
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+namespace disasm {
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+
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+static void
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+run_tests ()
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+{
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+ if (current_inferior () != nullptr)
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+ {
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+ struct gdbarch *gdbarch = current_inferior ()->gdbarch;
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+
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+ /* Check that tui_find_disassembly_address robustly handles the case of
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+ being passed a PC for which gdb_print_insn throws a MEMORY_ERROR. */
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+ SELF_CHECK (tui_find_disassembly_address (gdbarch, 0, 1) == 0);
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+ SELF_CHECK (tui_find_disassembly_address (gdbarch, 0, -1) == 0);
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+ }
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+}
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+
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+} /* namespace disasm */
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+} /* namespace tui */
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+} /* namespace selftests */
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+#endif /* GDB_SELF_TEST */
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+
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+void _initialize_tui_disasm ();
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+void
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+_initialize_tui_disasm ()
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+{
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+#if GDB_SELF_TEST
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+ selftests::register_test ("tui-disasm", selftests::tui::disasm::run_tests);
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+#endif
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+}
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--
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2.35.3
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