Re: [patch] Accessing tls variables across files causes a bug

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

(re)patched.  GDB misses getters to do it universally.

Testsuite addition, no regressions (x86_64-unknown-linux-gnu):
+PASS: gdb.threads/tls.exp: p a_thread_local
+PASS: gdb.threads/tls.exp: p file2_thread_local
+PASS: gdb.threads/tls.exp: info address file2_thread_local
+PASS: gdb.threads/tls.exp: p a_thread_local second time
+PASS: gdb.threads/tls.exp: info address a_thread_local


Regards,
Jan

2008-11-29  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Fix resolving external references to TLS variables.
	* findvar.c: Include `objfiles.h'.
	(read_var_value <LOC_UNRESOLVED>): New variable `obj_section'.  Handle
	SEC_THREAD_LOCAL variables.
	* printcmd.c (address_info <LOC_UNRESOLVED>): New variable
	`obj_section'.  Handle SEC_THREAD_LOCAL variables.

2008-11-29  Jan Kratochvil  <jan.kratochvil@redhat.com>

	Test resolving external references to TLS variables.
	* gdb.threads/tls.exp: New tests to examine A_THREAD_LOCAL and
	FILE2_THREAD_LOCAL.
	(testfile2, srcfile2): New variables.
	* gdb.threads/tls.c (file2_thread_local)
	(function_referencing_file2_thread_local): New.
	* gdb.threads/tls2.c: New file.

--- gdb/findvar.c	5 Sep 2008 11:37:17 -0000	1.118
+++ gdb/findvar.c	30 Nov 2008 21:10:02 -0000
@@ -34,6 +34,7 @@
 #include "regcache.h"
 #include "user-regs.h"
 #include "block.h"
+#include "objfiles.h"
 
 /* Basic byte-swapping routines.  GDB has needed these for a long time...
    All extract a target-format integer at ADDR which is LEN bytes long.  */
@@ -536,6 +537,7 @@ read_var_value (struct symbol *var, stru
     case LOC_UNRESOLVED:
       {
 	struct minimal_symbol *msym;
+	struct obj_section *obj_section;
 
 	msym = lookup_minimal_symbol (SYMBOL_LINKAGE_NAME (var), NULL, NULL);
 	if (msym == NULL)
@@ -545,6 +547,12 @@ read_var_value (struct symbol *var, stru
 					   SYMBOL_OBJ_SECTION (msym));
 	else
 	  addr = SYMBOL_VALUE_ADDRESS (msym);
+
+	/* SYMBOL_VALUE_ADDRESS should return the translated address.  */
+	obj_section = SYMBOL_OBJ_SECTION (msym);
+	if (obj_section
+	    && (obj_section->the_bfd_section->flags & SEC_THREAD_LOCAL) != 0)
+	  addr = target_translate_tls_address (obj_section->objfile, addr);
       }
       break;
 
--- gdb/printcmd.c	20 Nov 2008 16:13:11 -0000	1.138
+++ gdb/printcmd.c	30 Nov 2008 21:10:06 -0000
@@ -1234,6 +1234,7 @@ address_info (char *exp, int from_tty)
     case LOC_UNRESOLVED:
       {
 	struct minimal_symbol *msym;
+	struct obj_section *obj_section;
 
 	msym = lookup_minimal_symbol (SYMBOL_LINKAGE_NAME (sym), NULL, NULL);
 	if (msym == NULL)
@@ -1241,8 +1242,19 @@ address_info (char *exp, int from_tty)
 	else
 	  {
 	    section = SYMBOL_OBJ_SECTION (msym);
-	    printf_filtered (_("static storage at address "));
 	    load_addr = SYMBOL_VALUE_ADDRESS (msym);
+
+	    /* SYMBOL_VALUE_ADDRESS should return the translated address.  */
+	    if (section
+		&& (section->the_bfd_section->flags & SEC_THREAD_LOCAL) != 0)
+	      {
+		printf_filtered (_("a thread-local variable at offset %s "
+				   "at final address "), paddr_nz (load_addr));
+		load_addr = target_translate_tls_address (section->objfile,
+							  load_addr);
+	      }
+	    else
+	      printf_filtered (_("static storage at address "));
 	    fputs_filtered (paddress (load_addr), gdb_stdout);
 	    if (section_is_overlay (section))
 	      {
--- gdb/testsuite/gdb.threads/tls.c	29 Jul 2003 21:51:25 -0000	1.2
+++ gdb/testsuite/gdb.threads/tls.c	30 Nov 2008 21:10:09 -0000
@@ -20,6 +20,9 @@
 __thread int a_thread_local;
 __thread int another_thread_local;
 
+/* psymtabs->symtabs resolving check.  */
+extern __thread int file2_thread_local;
+
 /* Global variable just for info addr in gdb.  */
 int a_global;
 
@@ -119,6 +122,12 @@ void *spin( vp )
 }
 
 void
+function_referencing_file2_thread_local (void)
+{
+  file2_thread_local = file2_thread_local;
+}
+
+void
 do_pass()
 {
     int i;
--- gdb/testsuite/gdb.threads/tls.exp	6 Aug 2008 12:52:08 -0000	1.9
+++ gdb/testsuite/gdb.threads/tls.exp	30 Nov 2008 21:10:09 -0000
@@ -15,7 +15,9 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 set testfile tls
+set testfile2 tls2
 set srcfile ${testfile}.c
+set srcfile2 ${testfile2}.c
 set binfile ${objdir}/${subdir}/${testfile}
 
 if [istarget "*-*-linux"] then {
@@ -24,7 +26,7 @@ if [istarget "*-*-linux"] then {
     set target_cflags ""
 }
 
-if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable [list debug "incdir=${objdir}"]] != "" } {
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile} ${srcdir}/${subdir}/${srcfile2}" "${binfile}" executable [list debug "incdir=${objdir}"]] != "" } {
     return -1
 }
 
@@ -284,6 +286,20 @@ gdb_test "info address a_global" \
 setup_kfail "gdb/1294" "*-*-*"
 gdb_test "info address me" ".*me.*is a variable at offset.*" "info address me"
 
+
+# Test LOC_UNRESOLVED references resolving for `extern' TLS variables.
+
+gdb_test "p a_thread_local" " = \[0-9\]+"
+# Here it could crash with: Cannot access memory at address 0x0
+gdb_test "p file2_thread_local" " = \[0-9\]+"
+# Depending on the current lookup scope we may get two answers:
+# LOC_UNRESOLVED: Symbol "file2_thread_local" is a thread-local variable at offset 8 at final address 0x7ffff7fdb94c.
+# LOC_COMPUTED:   Symbol "file2_thread_local" is a thread-local variable at offset 8 in the thread-local storage for `.../gdb.threads/tls'.
+gdb_test "info address file2_thread_local" "Symbol \"file2_thread_local\" is a thread-local variable.*"
+# Here it could also crash with: Cannot access memory at address 0x0
+gdb_test "p a_thread_local" " = \[0-9\]+" "p a_thread_local second time"
+gdb_test "info address a_thread_local" "Symbol \"a_thread_local\" is a thread-local variable.*"
+
 # Done!
 #
 gdb_exit
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gdb/testsuite/gdb.threads/tls2.c	30 Nov 2008 21:10:09 -0000
@@ -0,0 +1,28 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2008 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/>.
+
+   Please email any bugs, comments, and/or additions to this file to:
+   bug-gdb@prep.ai.mit.edu  */
+
+extern __thread int a_thread_local;
+__thread int file2_thread_local;
+
+void
+function_referencing_a_thread_local (void)
+{
+  a_thread_local = a_thread_local;
+}