From 9e0aa64f5510861b2517c5841b59adde8e423540 Mon Sep 17 00:00:00 2001 From: Jan Kratochvil Date: Mon, 19 May 2014 20:20:27 +0200 Subject: [PATCH] Fix gdbserver qGetTLSAddr for x86_64 -m32 gdbserver makes libthread_db to access uninitialized memory. Surprisingly it does not harm normally, even -fsanitize=address works with current gdbserver. I have found just valgrind detects it as a very first warning for gdbserver: Syscall param ptrace(addr) contains uninitialised byte(s) at 0x3721EECEBE: ptrace (ptrace.c:45) by 0x436EE5: ps_get_thread_area (linux-x86-low.c:252) by 0x5559D02: __td_ta_lookup_th_unique (td_ta_map_lwp2thr.c:157) by 0x5559EC3: td_ta_map_lwp2thr (td_ta_map_lwp2thr.c:207) by 0x43F87D: find_one_thread (thread-db.c:281) by 0x440038: thread_db_get_tls_address (thread-db.c:505) by 0x40F6D0: handle_query (server.c:2004) by 0x4124CF: process_serial_event (server.c:3445) by 0x4136B6: handle_serial_event (server.c:3889) by 0x419571: handle_file_event (event-loop.c:434) by 0x418D38: process_event (event-loop.c:189) by 0x419AB7: start_event_loop (event-loop.c:552) Reproducible with: cd gdb/testsuite g++ -o gdb.threads/tls gdb.threads/tls{,2}.c -m32 -pthread ../gdbserver/gdbserver :1234 gdb.threads/tls ../gdb -batch gdb.threads/tls -ex 'target remote :1234' -ex 'b spin' -ex c -ex 'p a_thread_local' It is more easily reproducible even without valgrind using s/0x00/0xff/ in the attached patch. It will then turn the output of reproducer above: $1 = 0 -> Cannot find thread-local storage for Thread 29044, executable file .../gdb/testsuite/gdb.threads/tls: Remote target failed to process qGetTLSAddr request gdb/gdbserver/ 2014-05-19 Jan Kratochvil Fix gdbserver qGetTLSAddr for x86_64 -m32. * linux-x86-low.c (X86_64_USER_REGS): New. (x86_fill_gregset): Call memset for BUF first in x86_64 -m32 case. Message-ID: <20140410114901.GA16411@host2.jankratochvil.net> --- gdb/gdbserver/ChangeLog | 6 ++++++ gdb/gdbserver/linux-x86-low.c | 5 +++++ 2 files changed, 11 insertions(+) diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog index 4537792a7a1..e509c2c4e4d 100644 --- a/gdb/gdbserver/ChangeLog +++ b/gdb/gdbserver/ChangeLog @@ -1,3 +1,9 @@ +2014-05-19 Jan Kratochvil + + Fix gdbserver qGetTLSAddr for x86_64 -m32. + * linux-x86-low.c (X86_64_USER_REGS): New. + (x86_fill_gregset): Call memset for BUF first in x86_64 -m32 case. + 2014-04-28 Yao Qi * Makefile.in (i386-avx512.c): Fix the typo of generated file diff --git a/gdb/gdbserver/linux-x86-low.c b/gdb/gdbserver/linux-x86-low.c index 1bd7b4abc95..10cd0d51e01 100644 --- a/gdb/gdbserver/linux-x86-low.c +++ b/gdb/gdbserver/linux-x86-low.c @@ -206,6 +206,7 @@ static const int x86_64_regmap[] = }; #define X86_64_NUM_REGS (sizeof (x86_64_regmap) / sizeof (x86_64_regmap[0])) +#define X86_64_USER_REGS (GS + 1) #else /* ! __x86_64__ */ @@ -364,6 +365,10 @@ x86_fill_gregset (struct regcache *regcache, void *buf) collect_register (regcache, i, ((char *) buf) + x86_64_regmap[i]); return; } + + /* 32-bit inferior registers need to be zero-extended. + Callers would read uninitialized memory otherwise. */ + memset (buf, 0x00, X86_64_USER_REGS * 8); #endif for (i = 0; i < I386_NUM_REGS; i++) -- 2.30.2