http://sourceware.org/ml/gdb-patches/2016-10/msg00207.html Subject: [patch+7.12.1 2/2] Fix TLS (such as 'errno') regression --3Pql8miugIZX0722 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Hi, 2273f0ac95a79ce29ef42025c63f90e82cf907d7 is the first bad commit commit 2273f0ac95a79ce29ef42025c63f90e82cf907d7 Author: Tom Tromey Date: Tue Oct 15 13:28:57 2013 -0600 change minsyms not to be relocated at read-time [FYI v3 06/10] change minsyms not to be relocated at read-time Message-Id: <1393441273-32268-7-git-send-email-tromey@redhat.com> https://sourceware.org/ml/gdb-patches/2014-02/msg00798.html mv /usr/lib/debug /usr/lib/debug-x echo 'int main(){}'|gcc -pthread -x c - ./gdb -q -ex start -ex 'set debug expr 1' -ex 'p errno' ./a.out 0 UNOP_MEMVAL_TLS TLS type @0x35df7e0 (__thread /* "/lib64/libc.so.6" */ ) 4 OP_LONG Type @0x35df850 (__CORE_ADDR), value 140737345728528 (0x7ffff77fb010) Cannot access memory at address 0xffffef7c9698 -> 0 UNOP_MEMVAL_TLS TLS type @0x3ad9520 (__thread /* "/lib64/libc.so.6" */ ) 4 OP_LONG Type @0x3ad9590 (__CORE_ADDR), value 16 (0x10) $1 = 0 With glibc debuginfo, that is without: mv /usr/lib/debug /usr/lib/debug-x 0 OP_VAR_VALUE Block @0x3b30e70, symbol @0x3b30d10 (errno) $1 = 0 So such case is unrelated to this patch and the regression is not visible with glibc debuginfo installed. I guess all these issues will be solved by Gary Benson's Infinity. But at least for older non-Infinity glibcs GDB should not regress. For the testcase it is important the variable is in objfile with non-zero base address. glibc is a shared library for 'errno' but I found easier for the testcase to use PIE instead of a shlib. For TLS variables in PT_EXEC the regression obviously does not happen. It has been found by a more complete testcase present in Fedora, the fix there also solves more cases where FSF GDB currently cannot resolve 'errno': http://pkgs.fedoraproject.org/cgit/rpms/gdb.git/tree/gdb-6.5-bz185337-resolve-tls-without-debuginfo-v2.patch FAIL: gdb.dwarf2/dw2-errno2.exp: macros=N threads=Y: print errno for core No regressions on {x86_64,x86_64-m32,i686}-fedora26pre-linux-gnu. OK for check-in? Thanks, Jan --3Pql8miugIZX0722 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline; filename="tls1-2.patch" gdb/ChangeLog 2016-10-09 Jan Kratochvil * parse.c (write_exp_msymbol): Fix ADDR computation. gdb/testsuite/ChangeLog 2016-10-09 Jan Kratochvil * gdb.threads/tls-nodebug-pie.c: New file. * gdb.threads/tls-nodebug-pie.exp: New file. --- a/gdb/parse.c +++ b/gdb/parse.c @@ -480,13 +480,17 @@ write_exp_msymbol (struct parser_state *ps, struct objfile *objfile = bound_msym.objfile; struct gdbarch *gdbarch = get_objfile_arch (objfile); - CORE_ADDR addr = BMSYMBOL_VALUE_ADDRESS (bound_msym); struct obj_section *section = MSYMBOL_OBJ_SECTION (objfile, msymbol); enum minimal_symbol_type type = MSYMBOL_TYPE (msymbol); - CORE_ADDR pc; + CORE_ADDR addr, pc; const int is_tls = (section != NULL && section->the_bfd_section->flags & SEC_THREAD_LOCAL); + if (is_tls) + addr = MSYMBOL_VALUE_RAW_ADDRESS (bound_msym.minsym); + else + addr = BMSYMBOL_VALUE_ADDRESS (bound_msym); + /* The minimal symbol might point to a function descriptor; resolve it to the actual code address instead. */ pc = gdbarch_convert_from_func_ptr_addr (gdbarch, addr, ¤t_target); --- /dev/null +++ b/gdb/testsuite/gdb.threads/tls-nodebug-pie.c @@ -0,0 +1,27 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2016 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 . */ + +#include + +__thread int thread_local = 42; + +int main(void) +{ + /* Ensure we link against pthreads even with --as-needed. */ + pthread_testcancel(); + return 0; +} --- /dev/null +++ b/gdb/testsuite/gdb.threads/tls-nodebug-pie.exp @@ -0,0 +1,29 @@ +# Copyright 2016 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 . + +standard_testfile + +if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable \ + [list "additional_flags=-fPIE -pie"]] != "" } { + return -1 +} + +clean_restart ${binfile} +if ![runto_main] then { + return 0 +} + +# Formerly: Cannot access memory at address 0xd5554d5216fc +gdb_test "p thread_local" " = 42" "thread local storage" --3Pql8miugIZX0722--