Fix breakpoints on file reloads for PIE binaries

[ Backport of master commit ea142fbfc9. ]

When a binary is built using PIE, reloading the file will cause GDB to error
on restart.  For example:
gdb ./a.out
(gdb) break main
(gdb) run
(gdb) file ./a.out
(gdb) continue

Will cause GDB to error with:
Continuing.
Warning:
Cannot insert breakpoint 1.
Cannot access memory at address 0x9e0
Command aborted.

This is due to the symbol offsets not being relocated after reloading the file.

Fix is to ensure solib_create_inferior_hook is called, in the same manner as
infrun.c:follow_exec().

Expand the idempotent test to cover PIE scenarios.

gdb/ChangeLog:

	* symfile.c (symbol_file_command): Call solib_create_inferior_hook.

gdb/testsuite/ChangeLog:

	* gdb.base/break-idempotent.exp: Test both PIE and non PIE.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index f15cc5fcf05746090e27c03045251dc44f606746..f101a27be5358fd8aec00279478644c294c47251 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2019-08-04  Alan Hayward  <alan.hayward@arm.com>
+
+       * symfile.c (symbol_file_command): Call solib_create_inferior_hook.
+
 2019-05-29  Tom Tromey  <tromey@adacore.com>
 
        PR c++/20020:

diff --git a/gdb/symfile.c b/gdb/symfile.c
index bd7931568734dccf9456b11217234f469762a70a..a03ac29541a1cccc4d8349d1b086b9ffd85029e4 100644 (file)
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -1672,7 +1672,19 @@ symbol_file_command (const char *args, int from_tty)
 
       validate_readnow_readnever (flags);
 
+      /* Set SYMFILE_DEFER_BP_RESET because the proper displacement for a PIE
+        (Position Independent Executable) main symbol file will only be
+        computed by the solib_create_inferior_hook below.  Without it,
+        breakpoint_re_set would fail to insert the breakpoints with the zero
+        displacement.  */
+      add_flags |= SYMFILE_DEFER_BP_RESET;
+
       symbol_file_add_main_1 (name, add_flags, flags, offset);
+
+      solib_create_inferior_hook (from_tty);
+
+      /* Now it's safe to re-add the breakpoints.  */
+      breakpoint_re_set ();
     }
 }
 

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 03824fa2ae5ae6bb056dbefae48aecb02f99eb93..db67e6ec0fe92a068dfb992ff1ab63a063c16169 100644 (file)
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2019-07-08  Alan Hayward  <alan.hayward@arm.com>
+
+       * gdb.base/break-idempotent.exp: Test both PIE and non PIE.
+
 2019-03-22  Alan Hayward  <alan.hayward@arm.com>
 
        * README: Add pie options.

diff --git a/gdb/testsuite/gdb.base/break-idempotent.exp b/gdb/testsuite/gdb.base/break-idempotent.exp
index 902a5f818be9971422b5cfb154a2f28c7ab998da..a8b4d92733c1dd8eb5fab59e3266da3931e66f97 100644 (file)
--- a/gdb/testsuite/gdb.base/break-idempotent.exp
+++ b/gdb/testsuite/gdb.base/break-idempotent.exp
@@ -36,23 +36,6 @@
 
 standard_testfile
 
-if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
-    return -1
-}
-
-if ![runto_main] then {
-    fail "can't run to main"
-    return 0
-}
-
-if [is_remote host] {
-    set arg [remote_download host $binfile]
-    if { $arg == "" } {
-       perror "download failed"
-       return -1
-    }
-}
-
 # Force a breakpoint re-set in GDB.  Currently this is done by
 # reloading symbols with the "file" command.
 
@@ -123,7 +106,7 @@ proc set_breakpoint { break_command } {
 proc test_break { always_inserted break_command } {
     set cmd [lindex [split "$break_command"] 0]
 
-    with_test_prefix "always-inserted $always_inserted: $cmd" {
+    with_test_prefix "$cmd" {
        delete_breakpoints
 
        if ![runto_main] then {
@@ -163,20 +146,43 @@ proc test_break { always_inserted break_command } {
     }
 }
 
-foreach always_inserted { "off" "on" } {
-    test_break $always_inserted "break"
+# The testcase uses the "file" command to force breakpoint re-set in
+# GDB.  Test both with and without PIE, as GDB used to mishandle
+# breakpoint re-set when reloading PIEs.
+foreach_with_prefix pie { "nopie" "pie" } {
+
+    set opts {debug}
+    lappend opts $pie
 
-    if {![skip_hw_breakpoint_tests]} {
-       test_break $always_inserted "hbreak"
+    set binfile [standard_output_file $testfile-$pie]
+
+    if {[prepare_for_testing "failed to prepare" $binfile $srcfile $opts]} {
+       continue
     }
 
-    if {![skip_hw_watchpoint_tests]} {
-       test_break $always_inserted "watch"
+    if [is_remote host] {
+       set arg [remote_download host $binfile]
+       if { $arg == "" } {
+           untested "download failed"
+           continue
+       }
     }
 
-    if {![skip_hw_watchpoint_access_tests]
-       && ![skip_hw_watchpoint_multi_tests]} {
-       test_break $always_inserted "rwatch"
-       test_break $always_inserted "awatch"
+    foreach_with_prefix always_inserted { "off" "on" } {
+       test_break $always_inserted "break"
+
+       if {![skip_hw_breakpoint_tests]} {
+           test_break $always_inserted "hbreak"
+       }
+
+       if {![skip_hw_watchpoint_tests]} {
+           test_break $always_inserted "watch"
+       }
+
+       if {![skip_hw_watchpoint_access_tests]
+           && ![skip_hw_watchpoint_multi_tests]} {
+           test_break $always_inserted "rwatch"
+           test_break $always_inserted "awatch"
+       }
     }
 }