[PATCH] Enable hardware watchpoints on attach for aarch64

[PATCH] Enable hardware watchpoints on attach for aarch64

[Richard Bunt]

This patch fixes a bug whereby hardware watchpoints are not used on
aarch64 when attaching to a target.  The fix adds an aarch64 specialization
of post_attach which records the number of available hardware debug registers
using aarch64_linux_get_debug_reg_capacity.  This implementation mirrors that
of aarch64_linux_child_post_startup_inferior which successfully enables the
use of hardware watchpoints when launching the target under the debugger.

2018-05-14  Richard Bunt<richard.bunt@arm.com>
		Dirk Schubert<dirk.schubert@arm.com>

     * aarch64-linux-nat.c (post_attach): New.
       (aarch64_linux_nat_target::post_attach): Override post_attach to
       record the number of hardware debug registers.

gdb/testsuite/ChangeLog:

2018-05-14  Richard Bunt<richard.bunt@arm.com>

     * gdb.base/watchpoint-hw-attach.c: New test.
     * gdb.base/watchpoint-hw-attach.exp: New file.
---
  Annotation for this patch
  gdb/aarch64-linux-nat.c                         | 18 ++++++
  gdb/testsuite/gdb.base/watchpoint-hw-attach.c   | 44 +++++++++++++
  gdb/testsuite/gdb.base/watchpoint-hw-attach.exp | 85 +++++++++++++++++++++++++
  3 files changed, 147 insertions(+)
  create mode 100644 gdb/testsuite/gdb.base/watchpoint-hw-attach.c
  create mode 100644 gdb/testsuite/gdb.base/watchpoint-hw-attach.exp

diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index 908b83a..e0f75d0 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -76,6 +76,9 @@ public:
    /* Override the GNU/Linux inferior startup hook.  */
    void post_startup_inferior (ptid_t) override;
  
+  /* Override the GNU/Linux post attach hook.  */
+  void post_attach (int pid) override;
+
    /* These three defer to common nat/ code.  */
    void low_new_thread (struct lwp_info *lp) override
    { aarch64_linux_new_thread (lp); }
@@ -521,6 +524,21 @@ aarch64_linux_nat_target::post_startup_inferior (ptid_t ptid)
    linux_nat_target::post_startup_inferior (ptid);
  }
  
+/* Implement the "post_attach" target_ops method.  */
+
+void
+aarch64_linux_nat_target::post_attach (int pid)
+{
+  low_forget_process (pid);
+  /* Set the hardware debug register capacity.  If
+     aarch64_linux_get_debug_reg_capacity is not called
+     (as it is in aarch64_linux_child_post_startup_inferior) then
+     software watchpoints will be used instead of hardware
+     watchpoints when attaching to a target.  */
+  aarch64_linux_get_debug_reg_capacity (pid);
+  linux_nat_target::post_attach (pid);
+}
+
  extern struct target_desc *tdesc_arm_with_neon;
  
  /* Implement the "read_description" target_ops method.  */
diff --git a/gdb/testsuite/gdb.base/watchpoint-hw-attach.c b/gdb/testsuite/gdb.base/watchpoint-hw-attach.c
new file mode 100644
index 0000000..9d55b28
--- /dev/null
+++ b/gdb/testsuite/gdb.base/watchpoint-hw-attach.c
@@ -0,0 +1,44 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2018 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/>.  */
+
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+/* This is set to 1 by the debugger post attach to continue to the
+ watchpoint trigger.  */
+volatile int should_continue = 0;
+/* The variable to place a watchpoint on.  */
+volatile int watched_variable = 0;
+
+int
+main (void)
+{
+  unsigned int counter = 1;
+  int mypid = getpid ();
+
+  /* Wait for the debugger to attach, but not indefinitely so this
+     test program is not left hanging around.  */
+  for (counter = 0; !should_continue && counter < 100; counter++)
+    sleep (1);			/* pidacquired */
+
+  watched_variable = 0;		/* prewatchtrigger */
+  /* Trigger a watchpoint.  */
+  watched_variable = 4;
+  printf ("My variable is %d\n", watched_variable);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp b/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp
new file mode 100644
index 0000000..a030cb7
--- /dev/null
+++ b/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp
@@ -0,0 +1,85 @@
+# Copyright 2018 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/>.
+
+# watchpoint-hw-attach.exp -- Test if hardware watchpoints are used
+# when attaching to a target.
+
+if {[skip_hw_watchpoint_tests]} {
+    return 0
+}
+
+if {![can_spawn_for_attach]} {
+    return 0
+}
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
+    return -1
+}
+
+clean_restart $binfile
+
+if ![runto_main] {
+    untested "can't run to main"
+    return -1
+}
+# Run to the point where mypid in the test program has been
+# populated.
+gdb_breakpoint [gdb_get_line_number "pidacquired"]
+gdb_continue_to_breakpoint "pidacquired"
+
+# Get the PID of the test process.
+set testpid ""
+set test "get inferior process ID"
+    gdb_test_multiple "p mypid" $test {
+	-re " = ($decimal)\r\n$gdb_prompt $" {
+	set testpid $expect_out(1,string)
+	pass $test
+    }
+}
+
+gdb_test "detach" "Detaching from program: .*"
+
+if {$testpid == ""} {
+    return -1
+}
+
+# A clean restart is needed to force the hardware watchpoint setup
+# logic to run post attach rather than post inferior launch.
+clean_restart $binfile
+
+set test "attach $testpid"
+gdb_test_multiple $test $test {
+    -re "Attaching to program.*process $testpid\r\n.*$gdb_prompt $" {
+	pass "$test"
+    }
+    timeout {
+	fail "$test"
+    }
+}
+
+gdb_test_no_output "set should_continue = 1"
+# Ensure the test program is in the top frame so the required
+# variables are in scope.
+gdb_breakpoint [gdb_get_line_number "prewatchtrigger"]
+gdb_continue_to_breakpoint "prewatchtrigger"
+
+gdb_test "watch watched_variable" \
+	 "Hardware watchpoint $decimal: watched_variable"
+
+gdb_test "continue" \
+	 "continue.*Continuing.*\.Hardware watchpoint $decimal:\
+         watched_variable.*Old value = 0.*New value = 4.*"
-- 1.8.5.6

[PING] [PATCH] Enable hardware watchpoints on attach for aarch64

[Richard Bunt]

Polite ping.


On 05/23/2018 09:48 AM, Richard Bunt wrote:
> This patch fixes a bug whereby hardware watchpoints are not used on
> aarch64 when attaching to a target.  The fix adds an aarch64 
> specialization
> of post_attach which records the number of available hardware debug 
> registers
> using aarch64_linux_get_debug_reg_capacity.  This implementation 
> mirrors that
> of aarch64_linux_child_post_startup_inferior which successfully 
> enables the
> use of hardware watchpoints when launching the target under the debugger.
>
> 2018-05-14  Richard Bunt<richard.bunt@arm.com>
>         Dirk Schubert<dirk.schubert@arm.com>
>
>     * aarch64-linux-nat.c (post_attach): New.
>       (aarch64_linux_nat_target::post_attach): Override post_attach to
>       record the number of hardware debug registers.
>
> gdb/testsuite/ChangeLog:
>
> 2018-05-14  Richard Bunt<richard.bunt@arm.com>
>
>     * gdb.base/watchpoint-hw-attach.c: New test.
>     * gdb.base/watchpoint-hw-attach.exp: New file.
> ---
>  Annotation for this patch
>  gdb/aarch64-linux-nat.c                         | 18 ++++++
>  gdb/testsuite/gdb.base/watchpoint-hw-attach.c   | 44 +++++++++++++
>  gdb/testsuite/gdb.base/watchpoint-hw-attach.exp | 85 
> +++++++++++++++++++++++++
>  3 files changed, 147 insertions(+)
>  create mode 100644 gdb/testsuite/gdb.base/watchpoint-hw-attach.c
>  create mode 100644 gdb/testsuite/gdb.base/watchpoint-hw-attach.exp
>
> diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
> index 908b83a..e0f75d0 100644
> --- a/gdb/aarch64-linux-nat.c
> +++ b/gdb/aarch64-linux-nat.c
> @@ -76,6 +76,9 @@ public:
>    /* Override the GNU/Linux inferior startup hook.  */
>    void post_startup_inferior (ptid_t) override;
>
> +  /* Override the GNU/Linux post attach hook.  */
> +  void post_attach (int pid) override;
> +
>    /* These three defer to common nat/ code.  */
>    void low_new_thread (struct lwp_info *lp) override
>    { aarch64_linux_new_thread (lp); }
> @@ -521,6 +524,21 @@ aarch64_linux_nat_target::post_startup_inferior 
> (ptid_t ptid)
>    linux_nat_target::post_startup_inferior (ptid);
>  }
>
> +/* Implement the "post_attach" target_ops method.  */
> +
> +void
> +aarch64_linux_nat_target::post_attach (int pid)
> +{
> +  low_forget_process (pid);
> +  /* Set the hardware debug register capacity.  If
> +     aarch64_linux_get_debug_reg_capacity is not called
> +     (as it is in aarch64_linux_child_post_startup_inferior) then
> +     software watchpoints will be used instead of hardware
> +     watchpoints when attaching to a target.  */
> +  aarch64_linux_get_debug_reg_capacity (pid);
> +  linux_nat_target::post_attach (pid);
> +}
> +
>  extern struct target_desc *tdesc_arm_with_neon;
>
>  /* Implement the "read_description" target_ops method.  */
> diff --git a/gdb/testsuite/gdb.base/watchpoint-hw-attach.c 
> b/gdb/testsuite/gdb.base/watchpoint-hw-attach.c
> new file mode 100644
> index 0000000..9d55b28
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/watchpoint-hw-attach.c
> @@ -0,0 +1,44 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2018 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/>.  */
> +
> +#include <stdio.h>
> +#include <sys/types.h>
> +#include <unistd.h>
> +
> +/* This is set to 1 by the debugger post attach to continue to the
> + watchpoint trigger.  */
> +volatile int should_continue = 0;
> +/* The variable to place a watchpoint on.  */
> +volatile int watched_variable = 0;
> +
> +int
> +main (void)
> +{
> +  unsigned int counter = 1;
> +  int mypid = getpid ();
> +
> +  /* Wait for the debugger to attach, but not indefinitely so this
> +     test program is not left hanging around.  */
> +  for (counter = 0; !should_continue && counter < 100; counter++)
> +    sleep (1);            /* pidacquired */
> +
> +  watched_variable = 0;        /* prewatchtrigger */
> +  /* Trigger a watchpoint.  */
> +  watched_variable = 4;
> +  printf ("My variable is %d\n", watched_variable);
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp 
> b/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp
> new file mode 100644
> index 0000000..a030cb7
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp
> @@ -0,0 +1,85 @@
> +# Copyright 2018 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/>.
> +
> +# watchpoint-hw-attach.exp -- Test if hardware watchpoints are used
> +# when attaching to a target.
> +
> +if {[skip_hw_watchpoint_tests]} {
> +    return 0
> +}
> +
> +if {![can_spawn_for_attach]} {
> +    return 0
> +}
> +
> +standard_testfile
> +
> +if {[prepare_for_testing "failed to prepare" $testfile $srcfile 
> debug]} {
> +    return -1
> +}
> +
> +clean_restart $binfile
> +
> +if ![runto_main] {
> +    untested "can't run to main"
> +    return -1
> +}
> +# Run to the point where mypid in the test program has been
> +# populated.
> +gdb_breakpoint [gdb_get_line_number "pidacquired"]
> +gdb_continue_to_breakpoint "pidacquired"
> +
> +# Get the PID of the test process.
> +set testpid ""
> +set test "get inferior process ID"
> +    gdb_test_multiple "p mypid" $test {
> +    -re " = ($decimal)\r\n$gdb_prompt $" {
> +    set testpid $expect_out(1,string)
> +    pass $test
> +    }
> +}
> +
> +gdb_test "detach" "Detaching from program: .*"
> +
> +if {$testpid == ""} {
> +    return -1
> +}
> +
> +# A clean restart is needed to force the hardware watchpoint setup
> +# logic to run post attach rather than post inferior launch.
> +clean_restart $binfile
> +
> +set test "attach $testpid"
> +gdb_test_multiple $test $test {
> +    -re "Attaching to program.*process $testpid\r\n.*$gdb_prompt $" {
> +    pass "$test"
> +    }
> +    timeout {
> +    fail "$test"
> +    }
> +}
> +
> +gdb_test_no_output "set should_continue = 1"
> +# Ensure the test program is in the top frame so the required
> +# variables are in scope.
> +gdb_breakpoint [gdb_get_line_number "prewatchtrigger"]
> +gdb_continue_to_breakpoint "prewatchtrigger"
> +
> +gdb_test "watch watched_variable" \
> +     "Hardware watchpoint $decimal: watched_variable"
> +
> +gdb_test "continue" \
> +     "continue.*Continuing.*\.Hardware watchpoint $decimal:\
> +         watched_variable.*Old value = 0.*New value = 4.*"
> -- 1.8.5.6
>

Re: [PING] [PATCH] Enable hardware watchpoints on attach for aarch64

[Alan Hayward]

Aarch64 changes look good to me.
I’m not up to speed enough with .exp files to comment on that part.
I tested it on an aarch64 box, and it works fine for me.

Alan.

> On 7 Jun 2018, at 09:54, Richard Bunt <richard.bunt@arm.com> wrote:
> 
> Polite ping.
> 
> 
> On 05/23/2018 09:48 AM, Richard Bunt wrote:
>> This patch fixes a bug whereby hardware watchpoints are not used on
>> aarch64 when attaching to a target.  The fix adds an aarch64 specialization
>> of post_attach which records the number of available hardware debug registers
>> using aarch64_linux_get_debug_reg_capacity.  This implementation mirrors that
>> of aarch64_linux_child_post_startup_inferior which successfully enables the
>> use of hardware watchpoints when launching the target under the debugger.
>> 
>> 2018-05-14  Richard Bunt<richard.bunt@arm.com>
>>         Dirk Schubert<dirk.schubert@arm.com>
>> 
>>     * aarch64-linux-nat.c (post_attach): New.
>>       (aarch64_linux_nat_target::post_attach): Override post_attach to
>>       record the number of hardware debug registers.
>> 
>> gdb/testsuite/ChangeLog:
>> 
>> 2018-05-14  Richard Bunt<richard.bunt@arm.com>
>> 
>>     * gdb.base/watchpoint-hw-attach.c: New test.
>>     * gdb.base/watchpoint-hw-attach.exp: New file.
>> ---
>>  Annotation for this patch
>>  gdb/aarch64-linux-nat.c                         | 18 ++++++
>>  gdb/testsuite/gdb.base/watchpoint-hw-attach.c   | 44 +++++++++++++
>>  gdb/testsuite/gdb.base/watchpoint-hw-attach.exp | 85 +++++++++++++++++++++++++
>>  3 files changed, 147 insertions(+)
>>  create mode 100644 gdb/testsuite/gdb.base/watchpoint-hw-attach.c
>>  create mode 100644 gdb/testsuite/gdb.base/watchpoint-hw-attach.exp
>> 
>> diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
>> index 908b83a..e0f75d0 100644
>> --- a/gdb/aarch64-linux-nat.c
>> +++ b/gdb/aarch64-linux-nat.c
>> @@ -76,6 +76,9 @@ public:
>>    /* Override the GNU/Linux inferior startup hook.  */
>>    void post_startup_inferior (ptid_t) override;
>> 
>> +  /* Override the GNU/Linux post attach hook.  */
>> +  void post_attach (int pid) override;
>> +
>>    /* These three defer to common nat/ code.  */
>>    void low_new_thread (struct lwp_info *lp) override
>>    { aarch64_linux_new_thread (lp); }
>> @@ -521,6 +524,21 @@ aarch64_linux_nat_target::post_startup_inferior (ptid_t ptid)
>>    linux_nat_target::post_startup_inferior (ptid);
>>  }
>> 
>> +/* Implement the "post_attach" target_ops method.  */
>> +
>> +void
>> +aarch64_linux_nat_target::post_attach (int pid)
>> +{
>> +  low_forget_process (pid);
>> +  /* Set the hardware debug register capacity.  If
>> +     aarch64_linux_get_debug_reg_capacity is not called
>> +     (as it is in aarch64_linux_child_post_startup_inferior) then
>> +     software watchpoints will be used instead of hardware
>> +     watchpoints when attaching to a target.  */
>> +  aarch64_linux_get_debug_reg_capacity (pid);
>> +  linux_nat_target::post_attach (pid);
>> +}
>> +
>>  extern struct target_desc *tdesc_arm_with_neon;
>> 
>>  /* Implement the "read_description" target_ops method.  */
>> diff --git a/gdb/testsuite/gdb.base/watchpoint-hw-attach.c b/gdb/testsuite/gdb.base/watchpoint-hw-attach.c
>> new file mode 100644
>> index 0000000..9d55b28
>> --- /dev/null
>> +++ b/gdb/testsuite/gdb.base/watchpoint-hw-attach.c
>> @@ -0,0 +1,44 @@
>> +/* This testcase is part of GDB, the GNU debugger.
>> +
>> +   Copyright 2018 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/>.  */
>> +
>> +#include <stdio.h>
>> +#include <sys/types.h>
>> +#include <unistd.h>
>> +
>> +/* This is set to 1 by the debugger post attach to continue to the
>> + watchpoint trigger.  */
>> +volatile int should_continue = 0;
>> +/* The variable to place a watchpoint on.  */
>> +volatile int watched_variable = 0;
>> +
>> +int
>> +main (void)
>> +{
>> +  unsigned int counter = 1;
>> +  int mypid = getpid ();
>> +
>> +  /* Wait for the debugger to attach, but not indefinitely so this
>> +     test program is not left hanging around.  */
>> +  for (counter = 0; !should_continue && counter < 100; counter++)
>> +    sleep (1);            /* pidacquired */
>> +
>> +  watched_variable = 0;        /* prewatchtrigger */
>> +  /* Trigger a watchpoint.  */
>> +  watched_variable = 4;
>> +  printf ("My variable is %d\n", watched_variable);
>> +  return 0;
>> +}
>> diff --git a/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp b/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp
>> new file mode 100644
>> index 0000000..a030cb7
>> --- /dev/null
>> +++ b/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp
>> @@ -0,0 +1,85 @@
>> +# Copyright 2018 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/>.
>> +
>> +# watchpoint-hw-attach.exp -- Test if hardware watchpoints are used
>> +# when attaching to a target.
>> +
>> +if {[skip_hw_watchpoint_tests]} {
>> +    return 0
>> +}
>> +
>> +if {![can_spawn_for_attach]} {
>> +    return 0
>> +}
>> +
>> +standard_testfile
>> +
>> +if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
>> +    return -1
>> +}
>> +
>> +clean_restart $binfile
>> +
>> +if ![runto_main] {
>> +    untested "can't run to main"
>> +    return -1
>> +}
>> +# Run to the point where mypid in the test program has been
>> +# populated.
>> +gdb_breakpoint [gdb_get_line_number "pidacquired"]
>> +gdb_continue_to_breakpoint "pidacquired"
>> +
>> +# Get the PID of the test process.
>> +set testpid ""
>> +set test "get inferior process ID"
>> +    gdb_test_multiple "p mypid" $test {
>> +    -re " = ($decimal)\r\n$gdb_prompt $" {
>> +    set testpid $expect_out(1,string)
>> +    pass $test
>> +    }
>> +}
>> +
>> +gdb_test "detach" "Detaching from program: .*"
>> +
>> +if {$testpid == ""} {
>> +    return -1
>> +}
>> +
>> +# A clean restart is needed to force the hardware watchpoint setup
>> +# logic to run post attach rather than post inferior launch.
>> +clean_restart $binfile
>> +
>> +set test "attach $testpid"
>> +gdb_test_multiple $test $test {
>> +    -re "Attaching to program.*process $testpid\r\n.*$gdb_prompt $" {
>> +    pass "$test"
>> +    }
>> +    timeout {
>> +    fail "$test"
>> +    }
>> +}
>> +
>> +gdb_test_no_output "set should_continue = 1"
>> +# Ensure the test program is in the top frame so the required
>> +# variables are in scope.
>> +gdb_breakpoint [gdb_get_line_number "prewatchtrigger"]
>> +gdb_continue_to_breakpoint "prewatchtrigger"
>> +
>> +gdb_test "watch watched_variable" \
>> +     "Hardware watchpoint $decimal: watched_variable"
>> +
>> +gdb_test "continue" \
>> +     "continue.*Continuing.*\.Hardware watchpoint $decimal:\
>> +         watched_variable.*Old value = 0.*New value = 4.*"
>> -- 1.8.5.6
>> 
> 

Re: [PING] [PATCH] Enable hardware watchpoints on attach for aarch64

[Simon Marchi]

On 2018-06-07 09:19, Alan Hayward wrote:
> Aarch64 changes look good to me.
> I’m not up to speed enough with .exp files to comment on that part.
> I tested it on an aarch64 box, and it works fine for me.

Hi,

I looked at the test, if Alan is fine with the code changes then I am 
fine with them.  I noted some nits, but otherwise it looks good.  Please 
push after addressing them.

>>> +# Get the PID of the test process.
>>> +set testpid ""
>>> +set test "get inferior process ID"
>>> +    gdb_test_multiple "p mypid" $test {
>>> +    -re " = ($decimal)\r\n$gdb_prompt $" {
>>> +    set testpid $expect_out(1,string)
>>> +    pass $test
>>> +    }
>>> +}

You can use get_integer_valueof for this.

>>> +set test "attach $testpid"
>>> +gdb_test_multiple $test $test {
>>> +    -re "Attaching to program.*process $testpid\r\n.*$gdb_prompt $" 
>>> {
>>> +    pass "$test"
>>> +    }
>>> +    timeout {
>>> +    fail "$test"
>>> +    }
>>> +}

Just wondering, can't simple gdb_test be used here?

>>> +
>>> +gdb_test_no_output "set should_continue = 1"
>>> +# Ensure the test program is in the top frame so the required
>>> +# variables are in scope.
>>> +gdb_breakpoint [gdb_get_line_number "prewatchtrigger"]
>>> +gdb_continue_to_breakpoint "prewatchtrigger"
>>> +
>>> +gdb_test "watch watched_variable" \
>>> +     "Hardware watchpoint $decimal: watched_variable"
>>> +
>>> +gdb_test "continue" \
>>> +     "continue.*Continuing.*\.Hardware watchpoint $decimal:\
>>> +         watched_variable.*Old value = 0.*New value = 4.*"

8 spaces -> tab on the last line.  Though for test patterns, it's fine 
to go over 80 columns, IMO.

Simon

[PATCH] Enable hardware watchpoints on attach for aarch64

[Richard Bunt]

This commit fixes a bug whereby hardware watchpoints are not used on
aarch64 when attaching to a target. The fix adds an aarch64 specialization
of post_attach which records the number of available hardware debug registers
using aarch64_linux_get_debug_reg_capacity. This implementation mirrors that
of aarch64_linux_child_post_startup_inferior which successfully enables the
use of hardware watchpoints when launching the target under the debugger.

2018-05-14  Richard Bunt  <richard.bunt@arm.com>
	Dirk Schubert  <dirk.schubert@arm.com>

	* aarch64-linux-nat.c (post_attach): New.
	(aarch64_linux_nat_target::post_attach): Override post_attach to
	record the number of hardware debug registers.

gdb/testsuite/ChangeLog:

2018-05-14  Richard Bunt  <richard.bunt@arm.com>

	* gdb.base/watchpoint-hw-attach.c: New test.
	* gdb.base/watchpoint-hw-attach.exp: New file.
---

Updated based on Simon's feedback; thanks for the review.

The feedback has been addressed as detailed below.

>On 2018-06-07 09:19, Alan Hayward wrote:
>> Aarch64 changes look good to me.
>> I'm not up to speed enough with .exp files to comment on that part.
>> I tested it on an aarch64 box, and it works fine for me.
>
>Hi,
>
>I looked at the test, if Alan is fine with the code changes then I am
>fine with them.  I noted some nits, but otherwise it looks good.  Please
>push after addressing them.
>
>>>> +# Get the PID of the test process.
>>>> +set testpid ""
>>>> +set test "get inferior process ID"
>>>> +    gdb_test_multiple "p mypid" $test {
>>>> +    -re " = ($decimal)\r\n$gdb_prompt $" {
>>>> +    set testpid $expect_out(1,string)
>>>> +    pass $test
>>>> +    }
>>>> +}
>
>You can use get_integer_valueof for this.
>

Fixed, and good to know about this one.

>>>> +set test "attach $testpid"
>>>> +gdb_test_multiple $test $test {
>>>> +    -re "Attaching to program.*process $testpid\r\n.*$gdb_prompt $" 
>>>> {
>>>> +    pass "$test"
>>>> +    }
>>>> +    timeout {
>>>> +    fail "$test"
>>>> +    }
>>>> +}
>
>Just wondering, can't simple gdb_test be used here?
>

Changed. There is no reason that I am aware of that this cannot be a
gdb_test. I think this was just the structure used in the attach test that I
borrowed from.

>>>> +
>>>> +gdb_test_no_output "set should_continue = 1"
>>>> +# Ensure the test program is in the top frame so the required
>>>> +# variables are in scope.
>>>> +gdb_breakpoint [gdb_get_line_number "prewatchtrigger"]
>>>> +gdb_continue_to_breakpoint "prewatchtrigger"
>>>> +
>>>> +gdb_test "watch watched_variable" \
>>>> +     "Hardware watchpoint $decimal: watched_variable"
>>>> +
>>>> +gdb_test "continue" \
>>>> +     "continue.*Continuing.*\.Hardware watchpoint $decimal:\
>>>> +         watched_variable.*Old value = 0.*New value = 4.*"
>
>8 spaces -> tab on the last line.  Though for test patterns, it's fine
>to go over 80 columns, IMO.
>

Fixed, that certainly makes it easier to read.

>Simon

Will push (as per the review) in a few days if there are no more objections.

Many thanks,

Rich

 gdb/aarch64-linux-nat.c                         | 18 +++++++
 gdb/testsuite/gdb.base/watchpoint-hw-attach.c   | 44 +++++++++++++++
 gdb/testsuite/gdb.base/watchpoint-hw-attach.exp | 71 +++++++++++++++++++++++++
 3 files changed, 133 insertions(+)
 create mode 100644 gdb/testsuite/gdb.base/watchpoint-hw-attach.c
 create mode 100644 gdb/testsuite/gdb.base/watchpoint-hw-attach.exp

diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index 1e7db29..c9fd062 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -77,6 +77,9 @@ public:
   /* Override the GNU/Linux inferior startup hook.  */
   void post_startup_inferior (ptid_t) override;
 
+  /* Override the GNU/Linux post attach hook.  */
+  void post_attach (int pid) override;
+
   /* These three defer to common nat/ code.  */
   void low_new_thread (struct lwp_info *lp) override
   { aarch64_linux_new_thread (lp); }
@@ -568,6 +571,21 @@ aarch64_linux_nat_target::post_startup_inferior (ptid_t ptid)
   linux_nat_target::post_startup_inferior (ptid);
 }
 
+/* Implement the "post_attach" target_ops method.  */
+
+void
+aarch64_linux_nat_target::post_attach (int pid)
+{
+  low_forget_process (pid);
+  /* Set the hardware debug register capacity.  If
+     aarch64_linux_get_debug_reg_capacity is not called
+     (as it is in aarch64_linux_child_post_startup_inferior) then
+     software watchpoints will be used instead of hardware
+     watchpoints when attaching to a target.  */
+  aarch64_linux_get_debug_reg_capacity (pid);
+  linux_nat_target::post_attach (pid);
+}
+
 extern struct target_desc *tdesc_arm_with_neon;
 
 /* Implement the "read_description" target_ops method.  */
diff --git a/gdb/testsuite/gdb.base/watchpoint-hw-attach.c b/gdb/testsuite/gdb.base/watchpoint-hw-attach.c
new file mode 100644
index 0000000..9d55b28
--- /dev/null
+++ b/gdb/testsuite/gdb.base/watchpoint-hw-attach.c
@@ -0,0 +1,44 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2018 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/>.  */
+
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+/* This is set to 1 by the debugger post attach to continue to the
+ watchpoint trigger.  */
+volatile int should_continue = 0;
+/* The variable to place a watchpoint on.  */
+volatile int watched_variable = 0;
+
+int
+main (void)
+{
+  unsigned int counter = 1;
+  int mypid = getpid ();
+
+  /* Wait for the debugger to attach, but not indefinitely so this
+     test program is not left hanging around.  */
+  for (counter = 0; !should_continue && counter < 100; counter++)
+    sleep (1);			/* pidacquired */
+
+  watched_variable = 0;		/* prewatchtrigger */
+  /* Trigger a watchpoint.  */
+  watched_variable = 4;
+  printf ("My variable is %d\n", watched_variable);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp b/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp
new file mode 100644
index 0000000..0c5037c
--- /dev/null
+++ b/gdb/testsuite/gdb.base/watchpoint-hw-attach.exp
@@ -0,0 +1,71 @@
+# Copyright 2018 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/>.
+
+# watchpoint-hw-attach.exp -- Test if hardware watchpoints are used
+# when attaching to a target.
+
+if {[skip_hw_watchpoint_tests]} {
+    return 0
+}
+
+if {![can_spawn_for_attach]} {
+    return 0
+}
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile debug]} {
+    return -1
+}
+
+clean_restart $binfile
+
+if ![runto_main] {
+    untested "can't run to main"
+    return -1
+}
+
+# Run to the point where mypid in the test program has been
+# populated.
+gdb_breakpoint [gdb_get_line_number "pidacquired"]
+gdb_continue_to_breakpoint "pidacquired"
+
+# Get the PID of the test process.
+set testpid [get_integer_valueof "mypid" 0]
+
+gdb_test "detach" "Detaching from program: .*, process $testpid\r\n\\\[Inferior $decimal \\(process $testpid\\) detached\\\]"
+
+if {$testpid == ""} {
+    return -1
+}
+
+# A clean restart is needed to force the hardware watchpoint setup
+# logic to run post attach rather than post inferior launch.
+clean_restart $binfile
+
+gdb_test "attach $testpid" "Attaching to program: .*, process $testpid.*"
+
+gdb_test_no_output "set should_continue = 1"
+
+# Ensure the test program is in the top frame so the required
+# variables are in scope.
+gdb_breakpoint [gdb_get_line_number "prewatchtrigger"]
+gdb_continue_to_breakpoint "prewatchtrigger"
+
+gdb_test "watch watched_variable" \
+	 "Hardware watchpoint $decimal: watched_variable"
+
+gdb_test "continue" \
+	 "continue.*Continuing.*\.Hardware watchpoint $decimal: watched_variable.*Old value = 0.*New value = 4.*watched_variable\\);"
-- 
1.8.5.6