[PR gdb/13808] gdb.trace: Pass tdesc selected in gdbserver to IPA.

If gdbserver and IPA are using different tdesc, they will disagree
about 'R' trace packet size.  This results in mangled traces.

To make sure they pick the same tdesc, gdbserver pokes the tdesc
(specified as an index in a target-specific list) into a global
variable in IPA.  In theory, IPA could find out the tdesc on its
own, but that may be complex (in particular, I don't know how to
tell whether we have LAST_BREAK on s390 without messing with ptrace),
and we'd have to duplicate the logic.

Tested on i386 and x86_64.  On i386, it fixes two FAILs in ftrace.exp.
On x86_64, these failures have been KFAILed - one of them works now,
but the other now fails due to an unrelated reason (ugh).

gdb/gdbserver/ChangeLog:

	PR gdb/13808
	* Makefile.in: Add i386-*-linux-ipa.o and amd64-*-linux-ipa.o.
	* configure.srv: Ditto.
	* linux-aarch64-ipa.c (get_ipa_tdesc): New function.
	(initialize_low_tracepoint): Remove ipa_tdesc assignment.
	* linux-amd64-ipa.c: Add "linux-x86-tdesc.h" include.
	(init_registers_amd64_linux): Remove prototype.
	(tdesc_amd64_linux): Remove declaration.
	(get_ipa_tdesc): New function.
	(initialize_low_tracepoint): Remove ipa_tdesc assignment,
	initialize remaining tdescs.
	* linux-i386-ipa.c: Add "linux-x86-tdesc.h" include.
	(init_registers_i386_linux): Remove prototype.
	(tdesc_i386_linux): Remove declaration.
	(get_ipa_tdesc): New function.
	(initialize_low_tracepoint): Remove ipa_tdesc assignment,
	initialize remaining tdescs.
	* linux-low.c (linux_get_ipa_tdesc_idx): New function.
	(linux_target_ops): wire in linux_get_ipa_tdesc_idx.
	* linux-low.h (struct linux_target_ops): Add get_ipa_tdesc_idx.
	* linux-x86-low.c: Move tdesc declarations to linux-x86-tdesc.h.
	(x86_get_ipa_tdesc_idx): New function.
	(the_low_target): Wire in x86_get_ipa_tdesc_idx.
	* linux-x86-tdesc.h: New file.
	* target.h (struct target_ops): Add get_ipa_tdesc_idx.
	(target_get_ipa_tdesc_idx): New macro.
	* tracepoint.c (ipa_tdesc_idx): New macro.
	(struct ipa_sym_addresses): Add addr_ipa_tdesc_idx.
	(symbol_list): Add ipa_tdesc_idx.
	(cmd_qtstart): Write ipa_tdesc_idx in the target.
	(ipa_tdesc): Remove.
	(ipa_tdesc_idx): New variable.
	(get_context_regcache): Use get_ipa_tdesc.
	(gdb_collect): Ditto.
	(gdb_probe): Ditto.
	* tracepoint.h (get_ipa_tdesc): New prototype.
	(ipa_tdesc): Remove.

gdb/testsuite/ChangeLog:

	PR gdb/13808
	* gdb.trace/ftrace.exp (test_fast_tracepoints): Remove kfail.

13 files changed, 293 insertions, 69 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 3ec48fa..a9759b7 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,43 @@
+2016-02-25  Marcin Kościelnicki  <koriakin@0x04.net>
+
+	PR gdb/13808
+	* Makefile.in: Add i386-*-linux-ipa.o and amd64-*-linux-ipa.o.
+	* configure.srv: Ditto.
+	* linux-aarch64-ipa.c (get_ipa_tdesc): New function.
+	(initialize_low_tracepoint): Remove ipa_tdesc assignment.
+	* linux-amd64-ipa.c: Add "linux-x86-tdesc.h" include.
+	(init_registers_amd64_linux): Remove prototype.
+	(tdesc_amd64_linux): Remove declaration.
+	(get_ipa_tdesc): New function.
+	(initialize_low_tracepoint): Remove ipa_tdesc assignment,
+	initialize remaining tdescs.
+	* linux-i386-ipa.c: Add "linux-x86-tdesc.h" include.
+	(init_registers_i386_linux): Remove prototype.
+	(tdesc_i386_linux): Remove declaration.
+	(get_ipa_tdesc): New function.
+	(initialize_low_tracepoint): Remove ipa_tdesc assignment,
+	initialize remaining tdescs.
+	* linux-low.c (linux_get_ipa_tdesc_idx): New function.
+	(linux_target_ops): wire in linux_get_ipa_tdesc_idx.
+	* linux-low.h (struct linux_target_ops): Add get_ipa_tdesc_idx.
+	* linux-x86-low.c: Move tdesc declarations to linux-x86-tdesc.h.
+	(x86_get_ipa_tdesc_idx): New function.
+	(the_low_target): Wire in x86_get_ipa_tdesc_idx.
+	* linux-x86-tdesc.h: New file.
+	* target.h (struct target_ops): Add get_ipa_tdesc_idx.
+	(target_get_ipa_tdesc_idx): New macro.
+	* tracepoint.c (ipa_tdesc_idx): New macro.
+	(struct ipa_sym_addresses): Add addr_ipa_tdesc_idx.
+	(symbol_list): Add ipa_tdesc_idx.
+	(cmd_qtstart): Write ipa_tdesc_idx in the target.
+	(ipa_tdesc): Remove.
+	(ipa_tdesc_idx): New variable.
+	(get_context_regcache): Use get_ipa_tdesc.
+	(gdb_collect): Ditto.
+	(gdb_probe): Ditto.
+	* tracepoint.h (get_ipa_tdesc): New prototype.
+	(ipa_tdesc): Remove.
+
 2016-02-24  Pedro Alves  <palves@redhat.com>
 
 	* linux-low.c (check_stopped_by_breakpoint): Rename to ...
diff --git a/gdb/gdbserver/Makefile.in b/gdb/gdbserver/Makefile.in
index 1e874e3..257e9bf 100644
--- a/gdb/gdbserver/Makefile.in
+++ b/gdb/gdbserver/Makefile.in
@@ -495,6 +495,18 @@ regcache-ipa.o: regcache.c
 i386-linux-ipa.o: i386-linux.c
 	$(IPAGENT_COMPILE) $<
 	$(POSTCOMPILE)
+i386-mmx-linux-ipa.o: i386-mmx-linux.c
+	$(IPAGENT_COMPILE) $<
+	$(POSTCOMPILE)
+i386-avx-linux-ipa.o: i386-avx-linux.c
+	$(IPAGENT_COMPILE) $<
+	$(POSTCOMPILE)
+i386-mpx-linux-ipa.o: i386-mpx-linux.c
+	$(IPAGENT_COMPILE) $<
+	$(POSTCOMPILE)
+i386-avx512-linux-ipa.o: i386-avx512-linux.c
+	$(IPAGENT_COMPILE) $<
+	$(POSTCOMPILE)
 linux-i386-ipa.o: linux-i386-ipa.c
 	$(IPAGENT_COMPILE) $<
 	$(POSTCOMPILE)
@@ -504,6 +516,15 @@ linux-amd64-ipa.o: linux-amd64-ipa.c
 amd64-linux-ipa.o: amd64-linux.c
 	$(IPAGENT_COMPILE) $<
 	$(POSTCOMPILE)
+amd64-avx-linux-ipa.o: amd64-avx-linux.c
+	$(IPAGENT_COMPILE) $<
+	$(POSTCOMPILE)
+amd64-mpx-linux-ipa.o: amd64-mpx-linux.c
+	$(IPAGENT_COMPILE) $<
+	$(POSTCOMPILE)
+amd64-avx512-linux-ipa.o: amd64-avx512-linux.c
+	$(IPAGENT_COMPILE) $<
+	$(POSTCOMPILE)
 linux-aarch64-ipa.o: linux-aarch64-ipa.c
 	$(IPAGENT_COMPILE) $<
 	$(POSTCOMPILE)
diff --git a/gdb/gdbserver/configure.srv b/gdb/gdbserver/configure.srv
index a54b9e7..a89b1d1 100644
--- a/gdb/gdbserver/configure.srv
+++ b/gdb/gdbserver/configure.srv
@@ -29,8 +29,8 @@ srv_i386_linux_regobj="i386-linux.o i386-avx-linux.o i386-avx512-linux.o i386-mp
 srv_amd64_regobj="amd64.o amd64-avx.o amd64-avx512.o amd64-mpx.o x32.o x32-avx.o x32-avx512.o"
 srv_amd64_linux_regobj="amd64-linux.o amd64-avx-linux.o amd64-avx512-linux.o amd64-mpx-linux.o x32-linux.o x32-avx-linux.o x32-avx512-linux.o"
 
-ipa_i386_linux_regobj=i386-linux-ipa.o
-ipa_amd64_linux_regobj=amd64-linux-ipa.o
+ipa_i386_linux_regobj="i386-linux-ipa.o i386-avx-linux-ipa.o i386-avx512-linux-ipa.o i386-mpx-linux-ipa.o i386-mmx-linux-ipa.o"
+ipa_amd64_linux_regobj="amd64-linux-ipa.o amd64-avx-linux-ipa.o amd64-avx512-linux-ipa.o amd64-mpx-linux-ipa.o"
 
 srv_i386_32bit_xmlfiles="i386/32bit-core.xml i386/32bit-sse.xml i386/32bit-avx.xml i386/32bit-avx512.xml i386/32bit-mpx.xml"
 srv_i386_64bit_xmlfiles="i386/64bit-core.xml i386/64bit-sse.xml i386/64bit-avx.xml i386/64bit-avx512.xml i386/x32-core.xml i386/64bit-mpx.xml"
diff --git a/gdb/gdbserver/linux-aarch64-ipa.c b/gdb/gdbserver/linux-aarch64-ipa.c
index 758708d..f1eaa70 100644
--- a/gdb/gdbserver/linux-aarch64-ipa.c
+++ b/gdb/gdbserver/linux-aarch64-ipa.c
@@ -143,9 +143,18 @@ gdb_agent_get_raw_reg (const unsigned char *raw_regs, int regnum)
 			+ aarch64_ft_collect_regmap[regnum] * FT_CR_SIZE);
 }
 
+/* Return target_desc to use for IPA, given the tdesc index passed by
+   gdbserver.  Index is ignored, since we have only one tdesc
+   at the moment.  */
+
+const struct target_desc *
+get_ipa_tdesc (int idx)
+{
+  return tdesc_aarch64;
+}
+
 void
 initialize_low_tracepoint (void)
 {
   init_registers_aarch64 ();
-  ipa_tdesc = tdesc_aarch64;
 }
diff --git a/gdb/gdbserver/linux-amd64-ipa.c b/gdb/gdbserver/linux-amd64-ipa.c
index 2eeedcd..2dca943 100644
--- a/gdb/gdbserver/linux-amd64-ipa.c
+++ b/gdb/gdbserver/linux-amd64-ipa.c
@@ -20,6 +20,7 @@
 
 #include "server.h"
 #include "tracepoint.h"
+#include "linux-x86-tdesc.h"
 
 /* Defined in auto-generated file amd64-linux.c.  */
 void init_registers_amd64_linux (void);
@@ -166,9 +167,34 @@ supply_static_tracepoint_registers (struct regcache *regcache,
 
 #endif /* HAVE_UST */
 
+/* Return target_desc to use for IPA, given the tdesc index passed by
+   gdbserver.  */
+
+const struct target_desc *
+get_ipa_tdesc (int idx)
+{
+  switch (idx)
+    {
+    case X86_TDESC_SSE:
+      return tdesc_amd64_linux;
+    case X86_TDESC_AVX:
+      return tdesc_amd64_avx_linux;
+    case X86_TDESC_MPX:
+      return tdesc_amd64_mpx_linux;
+    case X86_TDESC_AVX512:
+      return tdesc_amd64_avx512_linux;
+    default:
+      internal_error (__FILE__, __LINE__,
+		      "unknown ipa tdesc index: %d", idx);
+      return tdesc_amd64_linux;
+    }
+}
+
 void
 initialize_low_tracepoint (void)
 {
   init_registers_amd64_linux ();
-  ipa_tdesc = tdesc_amd64_linux;
+  init_registers_amd64_avx_linux ();
+  init_registers_amd64_mpx_linux ();
+  init_registers_amd64_avx512_linux ();
 }
diff --git a/gdb/gdbserver/linux-i386-ipa.c b/gdb/gdbserver/linux-i386-ipa.c
index 11dc038..4860012 100644
--- a/gdb/gdbserver/linux-i386-ipa.c
+++ b/gdb/gdbserver/linux-i386-ipa.c
@@ -21,6 +21,7 @@
 #include "server.h"
 #include <sys/mman.h>
 #include "tracepoint.h"
+#include "linux-x86-tdesc.h"
 
 /* GDB register numbers.  */
 
@@ -47,10 +48,6 @@ enum i386_gdb_regnum
 
 #define i386_num_regs 16
 
-/* Defined in auto-generated file i386-linux.c.  */
-void init_registers_i386_linux (void);
-extern const struct target_desc *tdesc_i386_linux;
-
 #define FT_CR_EAX 15
 #define FT_CR_ECX 14
 #define FT_CR_EDX 13
@@ -247,10 +244,38 @@ initialize_fast_tracepoint_trampoline_buffer (void)
     }
 }
 
+/* Return target_desc to use for IPA, given the tdesc index passed by
+   gdbserver.  */
+
+const struct target_desc *
+get_ipa_tdesc (int idx)
+{
+  switch (idx)
+    {
+    case X86_TDESC_MMX:
+      return tdesc_i386_mmx_linux;
+    case X86_TDESC_SSE:
+      return tdesc_i386_linux;
+    case X86_TDESC_AVX:
+      return tdesc_i386_avx_linux;
+    case X86_TDESC_MPX:
+      return tdesc_i386_mpx_linux;
+    case X86_TDESC_AVX512:
+      return tdesc_i386_avx512_linux;
+    default:
+      internal_error (__FILE__, __LINE__,
+		      "unknown ipa tdesc index: %d", idx);
+      return tdesc_i386_linux;
+    }
+}
+
 void
 initialize_low_tracepoint (void)
 {
+  init_registers_i386_mmx_linux ();
   init_registers_i386_linux ();
-  ipa_tdesc = tdesc_i386_linux;
+  init_registers_i386_avx_linux ();
+  init_registers_i386_mpx_linux ();
+  init_registers_i386_avx512_linux ();
   initialize_fast_tracepoint_trampoline_buffer ();
 }
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 5e7560f..983b2d1 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -6406,6 +6406,15 @@ linux_supports_catch_syscall (void)
 }
 
 static int
+linux_get_ipa_tdesc_idx (void)
+{
+  if (the_low_target.get_ipa_tdesc_idx == NULL)
+    return 0;
+
+  return (*the_low_target.get_ipa_tdesc_idx) ();
+}
+
+static int
 linux_supports_tracepoints (void)
 {
   if (*the_low_target.supports_tracepoints == NULL)
@@ -7382,6 +7391,7 @@ static struct target_ops linux_target_ops = {
   linux_breakpoint_kind_from_current_state,
   linux_supports_software_single_step,
   linux_supports_catch_syscall,
+  linux_get_ipa_tdesc_idx,
 };
 
 #ifdef HAVE_LINUX_REGSETS
diff --git a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h
index 4ec8550..d4946c1 100644
--- a/gdb/gdbserver/linux-low.h
+++ b/gdb/gdbserver/linux-low.h
@@ -246,6 +246,9 @@ struct linux_target_ops
      due to SYSCALL_SIGTRAP.  */
   void (*get_syscall_trapinfo) (struct regcache *regcache,
 				int *sysno, int *sysret);
+
+  /* See target.h.  */
+  int (*get_ipa_tdesc_idx) (void);
 };
 
 extern struct linux_target_ops the_low_target;
diff --git a/gdb/gdbserver/linux-x86-low.c b/gdb/gdbserver/linux-x86-low.c
index 0c4954a..feaee92 100644
--- a/gdb/gdbserver/linux-x86-low.c
+++ b/gdb/gdbserver/linux-x86-low.c
@@ -45,57 +45,7 @@
 #include "nat/linux-nat.h"
 #include "nat/x86-linux.h"
 #include "nat/x86-linux-dregs.h"
-
-#ifdef __x86_64__
-/* Defined in auto-generated file amd64-linux.c.  */
-void init_registers_amd64_linux (void);
-extern const struct target_desc *tdesc_amd64_linux;
-
-/* Defined in auto-generated file amd64-avx-linux.c.  */
-void init_registers_amd64_avx_linux (void);
-extern const struct target_desc *tdesc_amd64_avx_linux;
-
-/* Defined in auto-generated file amd64-avx512-linux.c.  */
-void init_registers_amd64_avx512_linux (void);
-extern const struct target_desc *tdesc_amd64_avx512_linux;
-
-/* Defined in auto-generated file amd64-mpx-linux.c.  */
-void init_registers_amd64_mpx_linux (void);
-extern const struct target_desc *tdesc_amd64_mpx_linux;
-
-/* Defined in auto-generated file x32-linux.c.  */
-void init_registers_x32_linux (void);
-extern const struct target_desc *tdesc_x32_linux;
-
-/* Defined in auto-generated file x32-avx-linux.c.  */
-void init_registers_x32_avx_linux (void);
-extern const struct target_desc *tdesc_x32_avx_linux;
-
-/* Defined in auto-generated file x32-avx512-linux.c.  */
-void init_registers_x32_avx512_linux (void);
-extern const struct target_desc *tdesc_x32_avx512_linux;
-
-#endif
-
-/* Defined in auto-generated file i386-linux.c.  */
-void init_registers_i386_linux (void);
-extern const struct target_desc *tdesc_i386_linux;
-
-/* Defined in auto-generated file i386-mmx-linux.c.  */
-void init_registers_i386_mmx_linux (void);
-extern const struct target_desc *tdesc_i386_mmx_linux;
-
-/* Defined in auto-generated file i386-avx-linux.c.  */
-void init_registers_i386_avx_linux (void);
-extern const struct target_desc *tdesc_i386_avx_linux;
-
-/* Defined in auto-generated file i386-avx512-linux.c.  */
-void init_registers_i386_avx512_linux (void);
-extern const struct target_desc *tdesc_i386_avx512_linux;
-
-/* Defined in auto-generated file i386-mpx-linux.c.  */
-void init_registers_i386_mpx_linux (void);
-extern const struct target_desc *tdesc_i386_mpx_linux;
+#include "linux-x86-tdesc.h"
 
 #ifdef __x86_64__
 static struct target_desc *tdesc_amd64_linux_no_xml;
@@ -2891,6 +2841,38 @@ x86_supports_hardware_single_step (void)
   return 1;
 }
 
+static int
+x86_get_ipa_tdesc_idx (void)
+{
+  struct regcache *regcache = get_thread_regcache (current_thread, 0);
+  const struct target_desc *tdesc = regcache->tdesc;
+
+#ifdef __x86_64__
+  if (tdesc == tdesc_amd64_linux || tdesc == tdesc_amd64_linux_no_xml
+      || tdesc == tdesc_x32_linux)
+    return X86_TDESC_SSE;
+  if (tdesc == tdesc_amd64_avx_linux || tdesc == tdesc_x32_avx_linux)
+    return X86_TDESC_AVX;
+  if (tdesc == tdesc_amd64_mpx_linux)
+    return X86_TDESC_MPX;
+  if (tdesc == tdesc_amd64_avx512_linux || tdesc == tdesc_x32_avx512_linux)
+    return X86_TDESC_AVX512;
+#endif
+
+  if (tdesc == tdesc_i386_mmx_linux)
+    return X86_TDESC_MMX;
+  if (tdesc == tdesc_i386_linux || tdesc == tdesc_i386_linux_no_xml)
+    return X86_TDESC_SSE;
+  if (tdesc == tdesc_i386_avx_linux)
+    return X86_TDESC_AVX;
+  if (tdesc == tdesc_i386_mpx_linux)
+    return X86_TDESC_MPX;
+  if (tdesc == tdesc_i386_avx512_linux)
+    return X86_TDESC_AVX512;
+
+  return 0;
+}
+
 /* This is initialized assuming an amd64 target.
    x86_arch_setup will correct it for i386 or amd64 targets.  */
 
@@ -2934,6 +2916,7 @@ struct linux_target_ops the_low_target =
   NULL, /* breakpoint_kind_from_current_state */
   x86_supports_hardware_single_step,
   x86_get_syscall_trapinfo,
+  x86_get_ipa_tdesc_idx,
 };
 
 void
diff --git a/gdb/gdbserver/linux-x86-tdesc.h b/gdb/gdbserver/linux-x86-tdesc.h
new file mode 100644
index 0000000..33fdc27
--- /dev/null
+++ b/gdb/gdbserver/linux-x86-tdesc.h
@@ -0,0 +1,89 @@
+/* Low level support for x86 (i386 and x86-64), shared between gdbserver
+   and IPA.
+
+   Copyright (C) 2016 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+/* Note: since IPA obviously knows what ABI it's running on (i386 vs x86_64
+   vs x32), it's sufficient to pass only the register set here.  This,
+   together with the ABI known at IPA compile time, maps to a tdesc.  */
+
+enum x86_linux_tdesc {
+  X86_TDESC_MMX = 0,
+  X86_TDESC_SSE = 1,
+  X86_TDESC_AVX = 2,
+  X86_TDESC_MPX = 3,
+  X86_TDESC_AVX512 = 4,
+};
+
+#ifdef __x86_64__
+
+#if defined __LP64__  || !defined IN_PROCESS_AGENT
+/* Defined in auto-generated file amd64-linux.c.  */
+void init_registers_amd64_linux (void);
+extern const struct target_desc *tdesc_amd64_linux;
+
+/* Defined in auto-generated file amd64-avx-linux.c.  */
+void init_registers_amd64_avx_linux (void);
+extern const struct target_desc *tdesc_amd64_avx_linux;
+
+/* Defined in auto-generated file amd64-avx512-linux.c.  */
+void init_registers_amd64_avx512_linux (void);
+extern const struct target_desc *tdesc_amd64_avx512_linux;
+
+/* Defined in auto-generated file amd64-mpx-linux.c.  */
+void init_registers_amd64_mpx_linux (void);
+extern const struct target_desc *tdesc_amd64_mpx_linux;
+#endif
+
+#if defined __ILP32__ || !defined IN_PROCESS_AGENT
+/* Defined in auto-generated file x32-linux.c.  */
+void init_registers_x32_linux (void);
+extern const struct target_desc *tdesc_x32_linux;
+
+/* Defined in auto-generated file x32-avx-linux.c.  */
+void init_registers_x32_avx_linux (void);
+extern const struct target_desc *tdesc_x32_avx_linux;
+
+/* Defined in auto-generated file x32-avx512-linux.c.  */
+void init_registers_x32_avx512_linux (void);
+extern const struct target_desc *tdesc_x32_avx512_linux;
+#endif
+
+#endif
+
+#if defined __i386__ || !defined IN_PROCESS_AGENT
+/* Defined in auto-generated file i386-linux.c.  */
+void init_registers_i386_linux (void);
+extern const struct target_desc *tdesc_i386_linux;
+
+/* Defined in auto-generated file i386-mmx-linux.c.  */
+void init_registers_i386_mmx_linux (void);
+extern const struct target_desc *tdesc_i386_mmx_linux;
+
+/* Defined in auto-generated file i386-avx-linux.c.  */
+void init_registers_i386_avx_linux (void);
+extern const struct target_desc *tdesc_i386_avx_linux;
+
+/* Defined in auto-generated file i386-avx512-linux.c.  */
+void init_registers_i386_avx512_linux (void);
+extern const struct target_desc *tdesc_i386_avx512_linux;
+
+/* Defined in auto-generated file i386-mpx-linux.c.  */
+void init_registers_i386_mpx_linux (void);
+extern const struct target_desc *tdesc_i386_mpx_linux;
+#endif
diff --git a/gdb/gdbserver/target.h b/gdb/gdbserver/target.h
index 5af2051..4c14c20 100644
--- a/gdb/gdbserver/target.h
+++ b/gdb/gdbserver/target.h
@@ -471,6 +471,9 @@ struct target_ops
   /* Return 1 if the target supports catch syscall, 0 (or leave the
      callback NULL) otherwise.  */
   int (*supports_catch_syscall) (void);
+
+  /* Return tdesc index for IPA.  */
+  int (*get_ipa_tdesc_idx) (void);
 };
 
 extern struct target_ops *the_target;
@@ -550,6 +553,10 @@ int kill_inferior (int);
   (the_target->supports_catch_syscall ?			\
    (*the_target->supports_catch_syscall) () : 0)
 
+#define target_get_ipa_tdesc_idx()			\
+  (the_target->get_ipa_tdesc_idx			\
+   ? (*the_target->get_ipa_tdesc_idx) () : 0)
+
 #define target_supports_tracepoints()			\
   (the_target->supports_tracepoints			\
    ? (*the_target->supports_tracepoints) () : 0)
diff --git a/gdb/gdbserver/tracepoint.c b/gdb/gdbserver/tracepoint.c
index e7c18fd..dbd0b46 100644
--- a/gdb/gdbserver/tracepoint.c
+++ b/gdb/gdbserver/tracepoint.c
@@ -134,6 +134,7 @@ trace_vdebug (const char *fmt, ...)
 # define ust_loaded IPA_SYM_EXPORTED_NAME (ust_loaded)
 # define helper_thread_id IPA_SYM_EXPORTED_NAME (helper_thread_id)
 # define cmd_buf IPA_SYM_EXPORTED_NAME (cmd_buf)
+# define ipa_tdesc_idx IPA_SYM_EXPORTED_NAME (ipa_tdesc_idx)
 #endif
 
 #ifndef IN_PROCESS_AGENT
@@ -171,6 +172,7 @@ struct ipa_sym_addresses
   CORE_ADDR addr_get_trace_state_variable_value;
   CORE_ADDR addr_set_trace_state_variable_value;
   CORE_ADDR addr_ust_loaded;
+  CORE_ADDR addr_ipa_tdesc_idx;
 };
 
 static struct
@@ -207,6 +209,7 @@ static struct
   IPA_SYM(get_trace_state_variable_value),
   IPA_SYM(set_trace_state_variable_value),
   IPA_SYM(ust_loaded),
+  IPA_SYM(ipa_tdesc_idx),
 };
 
 static struct ipa_sym_addresses ipa_sym_addrs;
@@ -3211,6 +3214,11 @@ cmd_qtstart (char *packet)
 
   *packet = '\0';
 
+  /* Tell IPA about the correct tdesc.  */
+  if (write_inferior_integer (ipa_sym_addrs.addr_ipa_tdesc_idx,
+			      target_get_ipa_tdesc_idx ()))
+    error ("Error setting ipa_tdesc_idx variable in lib");
+
   /* Start out empty.  */
   if (agent_loaded_p ())
     write_inferior_data_pointer (ipa_sym_addrs.addr_tracepoints, 0);
@@ -4694,19 +4702,20 @@ collect_data_at_step (struct tracepoint_hit_ctx *ctx,
 #endif
 
 #ifdef IN_PROCESS_AGENT
-/* The target description used by the IPA.  Given that the IPA library
-   is built for a specific architecture that is loaded into the
-   inferior, there only needs to be one such description per
-   build.  */
-const struct target_desc *ipa_tdesc;
+/* The target description index for IPA.  Passed from gdbserver, used
+   to select ipa_tdesc.  */
+EXTERN_C_PUSH
+IP_AGENT_EXPORT_VAR int ipa_tdesc_idx;
+EXTERN_C_POP
 #endif
 
 static struct regcache *
 get_context_regcache (struct tracepoint_hit_ctx *ctx)
 {
   struct regcache *regcache = NULL;
-
 #ifdef IN_PROCESS_AGENT
+  const struct target_desc *ipa_tdesc = get_ipa_tdesc (ipa_tdesc_idx);
+
   if (ctx->type == fast_tracepoint)
     {
       struct fast_tracepoint_ctx *fctx = (struct fast_tracepoint_ctx *) ctx;
@@ -5779,11 +5788,13 @@ IP_AGENT_EXPORT_FUNC void
 gdb_collect (struct tracepoint *tpoint, unsigned char *regs)
 {
   struct fast_tracepoint_ctx ctx;
+  const struct target_desc *ipa_tdesc;
 
   /* Don't do anything until the trace run is completely set up.  */
   if (!tracing)
     return;
 
+  ipa_tdesc = get_ipa_tdesc (ipa_tdesc_idx);
   ctx.base.type = fast_tracepoint;
   ctx.regs = regs;
   ctx.regcache_initted = 0;
@@ -6629,6 +6640,7 @@ gdb_probe (const struct marker *mdata, void *probe_private,
 {
   struct tracepoint *tpoint;
   struct static_tracepoint_ctx ctx;
+  const struct target_desc *ipa_tdesc;
 
   /* Don't do anything until the trace run is completely set up.  */
   if (!tracing)
@@ -6637,6 +6649,7 @@ gdb_probe (const struct marker *mdata, void *probe_private,
       return;
     }
 
+  ipa_tdesc = get_ipa_tdesc (ipa_tdesc_idx);
   ctx.base.type = static_tracepoint;
   ctx.regcache_initted = 0;
   ctx.regs = regs;
diff --git a/gdb/gdbserver/tracepoint.h b/gdb/gdbserver/tracepoint.h
index cab89cf..e30f4f7 100644
--- a/gdb/gdbserver/tracepoint.h
+++ b/gdb/gdbserver/tracepoint.h
@@ -124,6 +124,7 @@ int handle_tracepoint_bkpts (struct thread_info *tinfo, CORE_ADDR stop_pc);
 
 #ifdef IN_PROCESS_AGENT
 void initialize_low_tracepoint (void);
+const struct target_desc *get_ipa_tdesc (int idx);
 void supply_fast_tracepoint_registers (struct regcache *regcache,
 				       const unsigned char *regs);
 void supply_static_tracepoint_registers (struct regcache *regcache,
@@ -131,9 +132,6 @@ void supply_static_tracepoint_registers (struct regcache *regcache,
 					 CORE_ADDR pc);
 void set_trampoline_buffer_space (CORE_ADDR begin, CORE_ADDR end,
 				  char *errmsg);
-
-extern const struct target_desc *ipa_tdesc;
-
 #else
 void stop_tracing (void);