[PATCH] btrace: indicate speculative execution

Markus Metzger
2015-08-06T13:20:46Z

Indicate speculatively executed instructions with a leading '?'. We use the
space that is normally used for the PC prefix. In the case where the
instruction at the current PC had been executed speculatively before, the PC
prefix will be partially overwritten resulting in "?> ".

As a side-effect, the /p modifier to omit the PC prefix in the "record
instruction-history" command now uses a 3-space PC prefix " " in order to
have enough space for the speculative execution indication.

CC: Eli Zaretskii <eliz@gnu.org>

2015-08-06 Markus Metzger <markus.t.metzger@intel.com>

* btrace.c (btrace_compute_ftrace_bts): Clear insn flags.
(pt_btrace_insn_flags): New.
(ftrace_add_pt): Call pt_btrace_insn_flags.
* btrace.h (btrace_insn_flag): New.
(btrace_insn) <flags>: New.
* record-btrace.c (btrace_insn_history): Print insn prefix.
* NEWS: Announce it.

doc/
* gdb.texinfo (Process Record and Replay): Document it.

testsuite/
* gdb.btrace/instruction_history.exp: Update.
* gdb.btrace/tsx.exp: New.
* gdb.btrace/tsx.c: New.
* lib/gdb.exp (skip_tsx_tests, skip_btrace_pt_tests): New.
---
gdb/NEWS | 3 +
gdb/btrace.c | 15 +++
gdb/btrace.h | 10 ++
gdb/doc/gdb.texinfo | 9 +-
gdb/record-btrace.c | 25 ++++-
gdb/testsuite/gdb.btrace/instruction_history.exp | 20 ++--
gdb/testsuite/gdb.btrace/tsx.c | 26 +++++
gdb/testsuite/gdb.btrace/tsx.exp | 41 ++++++++
gdb/testsuite/gdb.btrace/x86-tsx.S | 29 ++++++
gdb/testsuite/lib/gdb.exp | 124 +++++++++++++++++++++++
10 files changed, 288 insertions(+), 14 deletions(-)
create mode 100644 gdb/testsuite/gdb.btrace/tsx.c
create mode 100644 gdb/testsuite/gdb.btrace/tsx.exp
create mode 100644 gdb/testsuite/gdb.btrace/x86-tsx.S

diff --git a/gdb/NEWS b/gdb/NEWS
index 7ce9758..e2877d4 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -421,6 +421,9 @@ VAX running Ultrix vax-*-ultrix*
and "assf"), have been removed. Use the "sharedlibrary" command, or
its alias "share", instead.

+* The 'record instruction-history' command now indicates speculative execution
+ when using the Intel(R) Processor Trace recording format.
+
*** Changes in GDB 7.8

* New command line options
diff --git a/gdb/btrace.c b/gdb/btrace.c
index 94942f4..abdf639 100644
--- a/gdb/btrace.c
+++ b/gdb/btrace.c
@@ -660,6 +660,7 @@ btrace_compute_ftrace_bts (struct thread_info *tp,
insn.pc = pc;
insn.size = size;
insn.iclass = ftrace_classify_insn (gdbarch, pc);
+ insn.flags = 0;

ftrace_update_insns (end, &insn);

@@ -725,6 +726,19 @@ pt_reclassify_insn (enum pt_insn_class iclass)
}
}

+/* Return the btrace instruction flags for INSN. */
+
+static enum btrace_insn_flag
+pt_btrace_insn_flags (const struct pt_insn *insn)
+{
+ enum btrace_insn_flag flags = 0;
+
+ if (insn->speculative)
+ flags |= BTRACE_INSN_FLAG_SPECULATIVE;
+
+ return flags;
+}
+
/* Add function branch trace using DECODER. */

static void
@@ -792,6 +806,7 @@ ftrace_add_pt (struct pt_insn_decoder *decoder,
btinsn.pc = (CORE_ADDR) insn.ip;
btinsn.size = (gdb_byte) insn.size;
btinsn.iclass = pt_reclassify_insn (insn.iclass);
+ btinsn.flags = pt_btrace_insn_flags (&insn);

ftrace_update_insns (end, &btinsn);
}
diff --git a/gdb/btrace.h b/gdb/btrace.h
index 93c84ff..756a778 100644
--- a/gdb/btrace.h
+++ b/gdb/btrace.h
@@ -52,6 +52,13 @@ enum btrace_insn_class
BTRACE_INSN_JUMP
};

+/* Instruction flags. */
+enum btrace_insn_flag
+{
+ /* The instruction has been executed speculatively. */
+ BTRACE_INSN_FLAG_SPECULATIVE = (1 << 0)
+};
+
/* A branch trace instruction.

This represents a single instruction in a branch trace. */
@@ -65,6 +72,9 @@ struct btrace_insn

/* The instruction class of this instruction. */
enum btrace_insn_class iclass;
+
+ /* A bit vector of BTRACE_INSN_FLAGS. */
+ enum btrace_insn_flag flags;
};

/* A vector of branch trace instructions. */
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 9e2ecd1..d13bcc5 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -6736,8 +6736,13 @@ recorded ``future'' and begin recording a new ``future''.
Disassembles instructions from the recorded execution log. By
default, ten instructions are disassembled. This can be changed using
the @code{set record instruction-history-size} command. Instructions
-are printed in execution order. There are several ways to specify
-what part of the execution log to disassemble:
+are printed in execution order.
+
+Speculatively executed instructions are prefixed with @code{?}. This
+feature is not available for all recording formats.
+
+There are several ways to specify what part of the execution log to
+disassemble:

@table @code
@item record instruction-history @var{insn}
diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
index 6f4ee66..2f43171 100644
--- a/gdb/record-btrace.c
+++ b/gdb/record-btrace.c
@@ -567,14 +567,35 @@ btrace_insn_history (struct ui_out *uiout,
}
else
{
+ char prefix[4];
+
+ /* We may add a speculation prefix later. We use the same space
+ that is used for the pc prefix. */
+ if ((flags & DISASSEMBLY_OMIT_PC) == 0)
+ strncpy (prefix, pc_prefix (insn->pc), 3);
+ else
+ {
+ prefix[0] = ' ';
+ prefix[1] = ' ';
+ prefix[2] = ' ';
+ }
+ prefix[3] = 0;
+
/* Print the instruction index. */
ui_out_field_uint (uiout, "index", btrace_insn_number (&it));
ui_out_text (uiout, "\t");

+ /* Indicate speculative execution by a leading '?'. */
+ if ((insn->flags & BTRACE_INSN_FLAG_SPECULATIVE) != 0)
+ prefix[0] = '?';
+
+ /* Print the prefix; we tell gdb_disassembly below to omit it. */
+ ui_out_field_fmt (uiout, "prefix", "%s", prefix);
+
/* Disassembly with '/m' flag may not produce the expected result.
See PR gdb/11833. */
- gdb_disassembly (gdbarch, uiout, NULL, flags, 1, insn->pc,
- insn->pc + 1);
+ gdb_disassembly (gdbarch, uiout, NULL, flags | DISASSEMBLY_OMIT_PC,
+ 1, insn->pc, insn->pc + 1);
}
}
}
diff --git a/gdb/testsuite/gdb.btrace/instruction_history.exp b/gdb/testsuite/gdb.btrace/instruction_history.exp
index ba06647..0348f70 100644
--- a/gdb/testsuite/gdb.btrace/instruction_history.exp
+++ b/gdb/testsuite/gdb.btrace/instruction_history.exp
@@ -82,19 +82,19 @@ gdb_test "record instruction-history /f 3,+5" [multi_line \
]

gdb_test "record instruction-history /p 7,-5" [multi_line \
- "3\t0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tje 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>" \
- "4\t0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tdec %eax" \
- "5\t0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tjmp 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>" \
- "6\t0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tcmp \\\$0x0,%eax" \
- "7\t0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tje 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>\r" \
+ "3\t 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tje 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>" \
+ "4\t 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tdec %eax" \
+ "5\t 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tjmp 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>" \
+ "6\t 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tcmp \\\$0x0,%eax" \
+ "7\t 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tje 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>\r" \
]

gdb_test "record instruction-history /pf 3,7" [multi_line \
- "3\t0x\[0-9a-f\]+ <\\+\[0-9\]+>:\tje 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>" \
- "4\t0x\[0-9a-f\]+ <\\+\[0-9\]+>:\tdec %eax" \
- "5\t0x\[0-9a-f\]+ <\\+\[0-9\]+>:\tjmp 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>" \
- "6\t0x\[0-9a-f\]+ <\\+\[0-9\]+>:\tcmp \\\$0x0,%eax" \
- "7\t0x\[0-9a-f\]+ <\\+\[0-9\]+>:\tje 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>\r" \
+ "3\t 0x\[0-9a-f\]+ <\\+\[0-9\]+>:\tje 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>" \
+ "4\t 0x\[0-9a-f\]+ <\\+\[0-9\]+>:\tdec %eax" \
+ "5\t 0x\[0-9a-f\]+ <\\+\[0-9\]+>:\tjmp 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>" \
+ "6\t 0x\[0-9a-f\]+ <\\+\[0-9\]+>:\tcmp \\\$0x0,%eax" \
+ "7\t 0x\[0-9a-f\]+ <\\+\[0-9\]+>:\tje 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>\r" \
]

gdb_test "record instruction-history 3,3" "3\t 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>:\tje 0x\[0-9a-f\]+ <loop\\+\[0-9\]+>\r"
diff --git a/gdb/testsuite/gdb.btrace/tsx.c b/gdb/testsuite/gdb.btrace/tsx.c
new file mode 100644
index 0000000..f06046d
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/tsx.c
@@ -0,0 +1,26 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2015 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/>. */
+
+
+extern void test (void);
+
+int
+main (void)
+{
+ test ();
+ return 0;
+}
diff --git a/gdb/testsuite/gdb.btrace/tsx.exp b/gdb/testsuite/gdb.btrace/tsx.exp
new file mode 100644
index 0000000..525d4d2
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/tsx.exp
@@ -0,0 +1,41 @@
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2015 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/>.
+
+if { [skip_btrace_pt_tests] } { return -1 }
+if { [skip_tsx_tests] } { return -1 }
+
+# compile and run to main
+standard_testfile .c x86-tsx.S
+if [prepare_for_testing tsx.exp $testfile "$srcfile $srcfile2" {debug}] {
+ return -1
+}
+if ![runto_main] {
+ return -1
+}
+
+# record the test
+gdb_test_no_output "record btrace pt"
+gdb_test "next"
+
+# look at the instruction trace
+gdb_test "record instruction-history" [multi_line \
+ ".*" \
+ "\[0-9\]*\t\\? 0x\[0-9a-f\]+ <test\\+\[0-9\]+>:\txbegin\[^\\\r\\\n\]*" \
+ "\[0-9\]*\t\\? 0x\[0-9a-f\]+ <test\\+\[0-9\]+>:\tmov\[^\\\r\\\n\]*" \
+ "\[0-9\]*\t 0x\[0-9a-f\]+ <test\\+\[0-9\]+>:\txend\[^\\\r\\\n\]*" \
+ ".*" \
+ ]
diff --git a/gdb/testsuite/gdb.btrace/x86-tsx.S b/gdb/testsuite/gdb.btrace/x86-tsx.S
new file mode 100644
index 0000000..640d969
--- /dev/null
+++ b/gdb/testsuite/gdb.btrace/x86-tsx.S
@@ -0,0 +1,29 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2015 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/>. */
+
+ .text
+ .globl test
+ .type test, @function
+
+test:
+ xbegin .Lhandler
+ mov $0, %eax
+ xend
+ ret
+.Lhandler:
+ mov $1, %eax
+ ret
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 5659906..ad2ad6e 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -2562,6 +2562,63 @@ gdb_caching_proc skip_vsx_tests {
return $skip_vsx_tests
}

+# Run a test on the target to see if it supports TSX hardware. Return 0 if so,
+# 1 if it does not. Based on 'check_vmx_hw_available' from the GCC testsuite.
+
+gdb_caching_proc skip_tsx_tests {
+ global srcdir subdir gdb_prompt inferior_exited_re
+
+ set me "skip_tsx_tests"
+
+ set src [standard_temp_file tsx[pid].c]
+ set exe [standard_temp_file tsx[pid].x]
+
+ gdb_produce_source $src {
+ int main() {
+ asm volatile ("xbegin .L0");
+ asm volatile ("xend");
+ asm volatile (".L0: nop");
+ return 0;
+ }
+ }
+
+ verbose "$me: compiling testfile $src" 2
+ set lines [gdb_compile $src $exe executable {nowarnings quiet}]
+ file delete $src
+
+ if ![string match "" $lines] then {
+ verbose "$me: testfile compilation failed." 2
+ return 1
+ }
+
+ # No error message, compilation succeeded so now run it via gdb.
+
+ gdb_exit
+ gdb_start
+ gdb_reinitialize_dir $srcdir/$subdir
+ gdb_load "$exe"
+ gdb_run_cmd
+ gdb_expect {
+ -re ".*Illegal instruction.*${gdb_prompt} $" {
+ verbose -log "$me: TSX hardware not detected."
+ set skip_tsx_tests 1
+ }
+ -re ".*$inferior_exited_re normally.*${gdb_prompt} $" {
+ verbose -log "$me: TSX hardware detected."
+ set skip_tsx_tests 0
+ }
+ default {
+ warning "\n$me: default case taken."
+ set skip_tsx_tests 1
+ }
+ }
+ gdb_exit
+ remote_file build delete $exe
+
+ verbose "$me: returning $skip_tsx_tests" 2
+ return $skip_tsx_tests
+}
+
# Run a test on the target to see if it supports btrace hardware. Return 0 if so,
# 1 if it does not. Based on 'check_vmx_hw_available' from the GCC testsuite.

@@ -2628,6 +2685,73 @@ gdb_caching_proc skip_btrace_tests {
return $skip_btrace_tests
}

+# Run a test on the target to see if it supports btrace pt hardware.
+# Return 0 if so, 1 if it does not. Based on 'check_vmx_hw_available'
+# from the GCC testsuite.
+
+gdb_caching_proc skip_btrace_pt_tests {
+ global srcdir subdir gdb_prompt inferior_exited_re
+
+ set me "skip_btrace_tests"
+ if { ![istarget "i?86-*-*"] && ![istarget "x86_64-*-*"] } {
+ verbose "$me: target does not support btrace, returning 1" 2
+ return 1
+ }
+
+ # Set up, compile, and execute a test program.
+ # Include the current process ID in the file names to prevent conflicts
+ # with invocations for multiple testsuites.
+ set src [standard_temp_file btrace[pid].c]
+ set exe [standard_temp_file btrace[pid].x]
+
+ gdb_produce_source $src {
+ int main(void) { return 0; }
+ }
+
+ verbose "$me: compiling testfile $src" 2
+ set compile_flags {debug nowarnings quiet}
+ set lines [gdb_compile $src $exe executable $compile_flags]
+
+ if ![string match "" $lines] then {
+ verbose "$me: testfile compilation failed, returning 1" 2
+ file delete $src
+ return 1
+ }
+
+ # No error message, compilation succeeded so now run it via gdb.
+
+ gdb_exit
+ gdb_start
+ gdb_reinitialize_dir $srcdir/$subdir
+ gdb_load $exe
+ if ![runto_main] {
+ file delete $src
+ return 1
+ }
+ file delete $src
+ # In case of an unexpected output, we return 2 as a fail value.
+ set skip_btrace_tests 2
+ gdb_test_multiple "record btrace pt" "check btrace support" {
+ -re "You can't do that when your target is.*\r\n$gdb_prompt $" {
+ set skip_btrace_tests 1
+ }
+ -re "Target does not support branch tracing.*\r\n$gdb_prompt $" {
+ set skip_btrace_tests 1
+ }
+ -re "Could not enable branch tracing.*\r\n$gdb_prompt $" {
+ set skip_btrace_tests 1
+ }
+ -re "^record btrace pt\r\n$gdb_prompt $" {
+ set skip_btrace_tests 0
+ }
+ }
+ gdb_exit
+ remote_file build delete $exe
+
+ verbose "$me: returning $skip_btrace_tests" 2
+ return $skip_btrace_tests
+}
+
# Skip all the tests in the file if you are not on an hppa running
# hpux target.

--
1.8.3.1