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commit 9e0aa64f5510861b2517c5841b59adde8e423540
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Author: Jan Kratochvil <jan.kratochvil@redhat.com>
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Date: Mon May 19 20:20:27 2014 +0200
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Fix gdbserver qGetTLSAddr for x86_64 -m32
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gdbserver makes libthread_db to access uninitialized memory. Surprisingly it
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does not harm normally, even -fsanitize=address works with current gdbserver.
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I have found just valgrind detects it as a very first warning for gdbserver:
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Syscall param ptrace(addr) contains uninitialised byte(s)
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at 0x3721EECEBE: ptrace (ptrace.c:45)
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by 0x436EE5: ps_get_thread_area (linux-x86-low.c:252)
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by 0x5559D02: __td_ta_lookup_th_unique (td_ta_map_lwp2thr.c:157)
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by 0x5559EC3: td_ta_map_lwp2thr (td_ta_map_lwp2thr.c:207)
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by 0x43F87D: find_one_thread (thread-db.c:281)
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by 0x440038: thread_db_get_tls_address (thread-db.c:505)
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by 0x40F6D0: handle_query (server.c:2004)
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by 0x4124CF: process_serial_event (server.c:3445)
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by 0x4136B6: handle_serial_event (server.c:3889)
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by 0x419571: handle_file_event (event-loop.c:434)
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by 0x418D38: process_event (event-loop.c:189)
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by 0x419AB7: start_event_loop (event-loop.c:552)
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Reproducible with:
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cd gdb/testsuite
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g++ -o gdb.threads/tls gdb.threads/tls{,2}.c -m32 -pthread
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../gdbserver/gdbserver :1234 gdb.threads/tls
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../gdb -batch gdb.threads/tls -ex 'target remote :1234' -ex 'b spin' -ex c -ex 'p a_thread_local'
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It is more easily reproducible even without valgrind using s/0x00/0xff/ in the
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attached patch. It will then turn the output of reproducer above:
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$1 = 0
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->
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Cannot find thread-local storage for Thread 29044, executable file .../gdb/testsuite/gdb.threads/tls:
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Remote target failed to process qGetTLSAddr request
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gdb/gdbserver/
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2014-05-19 Jan Kratochvil <jan.kratochvil@redhat.com>
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Fix gdbserver qGetTLSAddr for x86_64 -m32.
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* linux-x86-low.c (X86_64_USER_REGS): New.
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(x86_fill_gregset): Call memset for BUF first in x86_64 -m32 case.
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Message-ID: <20140410114901.GA16411@host2.jankratochvil.net>
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Index: gdb-7.6.1/gdb/gdbserver/linux-x86-low.c
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===================================================================
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--- gdb-7.6.1.orig/gdb/gdbserver/linux-x86-low.c
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+++ gdb-7.6.1/gdb/gdbserver/linux-x86-low.c
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@@ -144,6 +144,7 @@ static const int x86_64_regmap[] =
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};
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#define X86_64_NUM_REGS (sizeof (x86_64_regmap) / sizeof (x86_64_regmap[0]))
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+#define X86_64_USER_REGS (GS + 1)
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#else /* ! __x86_64__ */
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@@ -275,6 +276,10 @@ x86_fill_gregset (struct regcache *regca
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collect_register (regcache, i, ((char *) buf) + x86_64_regmap[i]);
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return;
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}
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+
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+ /* 32-bit inferior registers need to be zero-extended.
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+ Callers would read uninitialized memory otherwise. */
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+ memset (buf, 0x00, X86_64_USER_REGS * 8);
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#endif
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for (i = 0; i < I386_NUM_REGS; i++)
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