[patch] Fix inferior execl of new PIE x86_64
Jan Kratochvil
jan.kratochvil@redhat.com
Thu Sep 30 21:58:00 GMT 2010
Hi,
gcc -o 1 1.c -Wall -g -fPIE -pie; gdb -nx ./1 -ex 'b main' -ex r -ex c
Starting program: .../gdb/1
Breakpoint 1, main (argc=1, argv=0x7fffffffdff8) at 1.c:7
7 setbuf (stdout, NULL);
Continuing.
re-exec
process 28056 is executing new program: .../gdb/1
Error in re-setting breakpoint 1: Cannot access memory at address 0x80c
exit
Program exited normally.
(gdb) _
while it should be:
re-exec
process 28095 is executing new program: .../gdb/1
Breakpoint 1, main (argc=2, argv=0x7fffffffe008) at 1.c:7
7 setbuf (stdout, NULL);
(gdb) _
The error comes from:
throw_error <- memory_error <- read_memory <- read_memory_unsigned_integer <-
amd64_analyze_prologue <- amd64_skip_prologue <- gdbarch_skip_prologue <-
skip_prologue_sal <- find_function_start_sal <- symbol_found <- decode_variable
<- decode_line_1 <- breakpoint_re_set_one <- catch_errors <- breakpoint_re_set
<- clear_symtab_users <- new_symfile_objfile <-
symbol_file_add_with_addrs_or_offsets <- symbol_file_add_from_bfd <-
symbol_file_add <- symbol_file_add_main_1 <- symbol_file_add_main <-
follow_exec
I understand this hack is not nice, the correct way would be to unify more
follow_exec with post_create_inferior. But I could break it for non-GNU/Linux
targets a lot.
No regressions on {x86_64,x86_64-m32,i686}-fedora14snapshot-linux-gnu.
Thanks,
Jan
for the demo above:
------------------------------------------------------------------------------
#include <unistd.h>
#include <assert.h>
#include <stdio.h>
int
main (int argc, char **argv)
{
setbuf (stdout, NULL);
if (argc == 1)
{
puts ("re-exec");
execl ("/proc/self/exe", argv[0], "foo", NULL);
assert (0);
}
puts ("exit");
return 0;
}
------------------------------------------------------------------------------
gdb/
2010-09-30 Jan Kratochvil <jan.kratochvil@redhat.com>
* infrun.c (follow_exec): Replace symbol_file_add_main by
symbol_file_add with SYMFILE_DEFER_BP_RESET, set_initial_language and
breakpoint_re_set.
* m32r-rom.c (m32r_load, m32r_upload_command): Use parameter 0 for
clear_symtab_users.
* objfiles.c (free_all_objfiles): Likewise.
* remote-m32r-sdi.c (m32r_load): Likewise.
* solib-som.c (som_solib_create_inferior_hook): Likewise.
* symfile.c (new_symfile_objfile): New comment for add_flags. Call
clear_symtab_users with ADD_FLAGS.
(reread_symbols): Use parameter 0 for clear_symtab_users.
(clear_symtab_users): New parameter add_flags. Do not call
breakpoint_re_set if SYMFILE_DEFER_BP_RESET.
(clear_symtab_users_cleanup): Use parameter 0 for clear_symtab_users.
* symtab.h (clear_symtab_users): New parameter add_flags.
gdb/testsuite/
2010-09-30 Jan Kratochvil <jan.kratochvil@redhat.com>
* gdb.base/pie-execl.exp: New file.
* gdb.base/pie-execl.c: New file.
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -835,8 +835,15 @@ follow_exec (ptid_t pid, char *execd_pathname)
/* That a.out is now the one to use. */
exec_file_attach (execd_pathname, 0);
- /* Load the main file's symbols. */
- symbol_file_add_main (execd_pathname, 0);
+ /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
+ (Position Independent Executable) main symbol file will get applied by
+ solib_create_inferior_hook below. breakpoint_re_set would fail to insert
+ the breakpoints with the zero displacement. */
+
+ symbol_file_add (execd_pathname, SYMFILE_MAINLINE | SYMFILE_DEFER_BP_RESET,
+ NULL, 0);
+
+ set_initial_language ();
#ifdef SOLIB_CREATE_INFERIOR_HOOK
SOLIB_CREATE_INFERIOR_HOOK (PIDGET (inferior_ptid));
@@ -846,6 +853,8 @@ follow_exec (ptid_t pid, char *execd_pathname)
jit_inferior_created_hook ();
+ breakpoint_re_set ();
+
/* Reinsert all breakpoints. (Those which were symbolic have
been reset to the proper address in the new a.out, thanks
to symbol_file_command...) */
--- a/gdb/m32r-rom.c
+++ b/gdb/m32r-rom.c
@@ -188,7 +188,7 @@ m32r_load (char *filename, int from_tty)
the stack may not be valid, and things would get horribly
confused... */
- clear_symtab_users ();
+ clear_symtab_users (0);
}
static void
@@ -551,7 +551,7 @@ m32r_upload_command (char *args, int from_tty)
the stack may not be valid, and things would get horribly
confused... */
- clear_symtab_users ();
+ clear_symtab_users (0);
}
/* Provide a prototype to silence -Wmissing-prototypes. */
--- a/gdb/objfiles.c
+++ b/gdb/objfiles.c
@@ -692,7 +692,7 @@ free_all_objfiles (void)
{
free_objfile (objfile);
}
- clear_symtab_users ();
+ clear_symtab_users (0);
}
/* A helper function for objfile_relocate1 that relocates a single
--- a/gdb/remote-m32r-sdi.c
+++ b/gdb/remote-m32r-sdi.c
@@ -1377,7 +1377,7 @@ m32r_load (char *args, int from_tty)
might be to call normal_stop, except that the stack may not be valid,
and things would get horribly confused... */
- clear_symtab_users ();
+ clear_symtab_users (0);
if (!nostart)
{
--- a/gdb/solib-som.c
+++ b/gdb/solib-som.c
@@ -354,7 +354,7 @@ keep_going:
/* Make the breakpoint at "_start" a shared library event breakpoint. */
create_solib_event_breakpoint (target_gdbarch, anaddr);
- clear_symtab_users ();
+ clear_symtab_users (0);
}
static void
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -1035,7 +1035,7 @@ syms_from_objfile (struct objfile *objfile,
/* Perform required actions after either reading in the initial
symbols for a new objfile, or mapping in the symbols from a reusable
- objfile. */
+ objfile. ADD_FLAGS is a bitmask of enum symfile_add_flags. */
void
new_symfile_objfile (struct objfile *objfile, int add_flags)
@@ -1048,7 +1048,7 @@ new_symfile_objfile (struct objfile *objfile, int add_flags)
/* OK, make it the "real" symbol file. */
symfile_objfile = objfile;
- clear_symtab_users ();
+ clear_symtab_users (add_flags);
}
else if ((add_flags & SYMFILE_DEFER_BP_RESET) == 0)
{
@@ -2527,7 +2527,7 @@ reread_symbols (void)
/* Notify objfiles that we've modified objfile sections. */
objfiles_changed ();
- clear_symtab_users ();
+ clear_symtab_users (0);
/* At least one objfile has changed, so we can consider that
the executable we're debugging has changed too. */
observer_notify_executable_changed ();
@@ -2745,10 +2745,10 @@ allocate_symtab (char *filename, struct objfile *objfile)
/* Reset all data structures in gdb which may contain references to symbol
- table data. */
+ table data. ADD_FLAGS is a bitmask of enum symfile_add_flags. */
void
-clear_symtab_users (void)
+clear_symtab_users (int add_flags)
{
/* Someday, we should do better than this, by only blowing away
the things that really need to be blown. */
@@ -2758,7 +2758,8 @@ clear_symtab_users (void)
clear_current_source_symtab_and_line ();
clear_displays ();
- breakpoint_re_set ();
+ if ((add_flags & SYMFILE_DEFER_BP_RESET) == 0)
+ breakpoint_re_set ();
set_default_breakpoint (0, NULL, 0, 0, 0);
clear_pc_function_cache ();
observer_notify_new_objfile (NULL);
@@ -2777,7 +2778,7 @@ clear_symtab_users (void)
static void
clear_symtab_users_cleanup (void *ignore)
{
- clear_symtab_users ();
+ clear_symtab_users (0);
}
/* OVERLAYS:
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -1186,7 +1186,7 @@ extern void skip_prologue_sal (struct symtab_and_line *);
/* symfile.c */
-extern void clear_symtab_users (void);
+extern void clear_symtab_users (int add_flags);
extern enum language deduce_language_from_filename (const char *);
--- /dev/null
+++ b/gdb/testsuite/gdb.base/pie-execl.c
@@ -0,0 +1,51 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2010 Free Software Foundation, Inc.
+
+ 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 <stdio.h>
+#include <unistd.h>
+#include <assert.h>
+
+static void pie_execl_marker (void);
+
+int
+main (int argc, char **argv)
+{
+ setbuf (stdout, NULL);
+
+#if BIN == 1
+ if (argc == 2)
+ {
+ printf ("pie-execl: re-exec: %s\n", argv[1]);
+ execl (argv[1], argv[1], NULL);
+ assert (0);
+ }
+#endif
+
+ pie_execl_marker ();
+
+ return 0;
+}
+
+/* pie_execl_marker must be on a different address than in `pie-execl2.c'. */
+
+volatile int v;
+
+static void
+pie_execl_marker (void)
+{
+ v = 1;
+}
--- /dev/null
+++ b/gdb/testsuite/gdb.base/pie-execl.exp
@@ -0,0 +1,94 @@
+# Copyright 2010 Free Software Foundation, Inc.
+
+# 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/>.
+
+# The problem was due to amd64_skip_prologue attempting to access inferior
+# memory before the PIE (Position Independent Executable) gets relocated.
+
+if { ![istarget *-linux*]} {
+ continue
+}
+
+set testfile "pie-execl"
+set srcfile ${testfile}.c
+set executable1 ${testfile}1
+set executable2 ${testfile}2
+set binfile1 ${objdir}/${subdir}/${executable1}
+set binfile2 ${objdir}/${subdir}/${executable2}
+
+# Use conditional compilation according to `BIN' as GDB remembers the source
+# file name of the breakpoint.
+
+set opts [list debug {additional_flags=-fPIE -pie}]
+if {[build_executable ${testfile}.exp $executable1 $srcfile [concat $opts {additional_flags=-DBIN=1}]] == ""
+ || [build_executable ${testfile}.exp $executable2 $srcfile [concat $opts {additional_flags=-DBIN=2}]] == ""} {
+ return -1
+}
+
+clean_restart ${executable1}
+
+gdb_test_no_output "set args ${binfile2}"
+
+if ![runto_main] {
+ return -1
+}
+
+# Do not stop on `main' after re-exec.
+delete_breakpoints
+
+gdb_breakpoint "pie_execl_marker"
+gdb_test "info breakpoints" ".*" ""
+
+set addr1 ""
+set test "pie_execl_marker address first"
+gdb_test_multiple "p/x &pie_execl_marker" $test {
+ -re " = (0x\[0-9a-f\]+)\r\n$gdb_prompt $" {
+ set addr1 $expect_out(1,string)
+ pass $test
+ }
+}
+verbose -log "addr1 is $addr1"
+
+set test "continue"
+gdb_test_multiple $test $test {
+ -re "Error in re-setting breakpoint" {
+ fail $test
+ }
+ -re "Cannot access memory" {
+ fail $test
+ }
+ -re "pie-execl: re-exec.*executing new program.*\r\nBreakpoint \[0-9\]+,\[^\r\n\]* pie_execl_marker .*\r\n$gdb_prompt $" {
+ pass $test
+ }
+}
+
+gdb_test "info breakpoints" ".*" ""
+
+set addr2 ""
+set test "pie_execl_marker address second"
+gdb_test_multiple "p/x &pie_execl_marker" $test {
+ -re " = (0x\[0-9a-f\]+)\r\n$gdb_prompt $" {
+ set addr2 $expect_out(1,string)
+ pass $test
+ }
+}
+verbose -log "addr2 is $addr2"
+
+# Ensure we cannot get a false PASS and the inferior has really changed.
+set test "pie_execl_marker address has changed"
+if [string equal $addr1 $addr2] {
+ fail $test
+} else {
+ pass $test
+}
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