[PATCH 2/2,v3] [AArch64] Test handling of additional brk instruction patterns

[Simon Marchi]

On 2020-01-15 6:51 a.m., Luis Machado wrote:
> New in v3:
> 
> - Minor formatting and code cleanups.
> - Added count check to validate number of brk SIGTRAP's.
> - Moved count to SIGTRAP check conditional block.
> 
> This test exercises the previous patch's code and makes sure GDB can
> properly get a SIGTRAP from various brk instruction patterns.
> 
> GDB needs to be able to see the program exiting normally. If GDB doesn't
> support the additional brk instructions, we will see timeouts.
> 
> We bail out with the first timeout since we won't be able to step through
> the program breakpoint anyway, so it is no use carrying on.
> 
> gdb/testsuite/ChangeLog:
> 
> 2020-01-15  Luis Machado  <luis.machado@linaro.org>
> 
> 	* gdb.arch/aarch64-brk-patterns.c: New source file.
> 	* gdb.arch/aarch64-brk-patterns.exp: New test.
> ---
>  gdb/testsuite/gdb.arch/aarch64-brk-patterns.c | 30 ++++++++
>  .../gdb.arch/aarch64-brk-patterns.exp         | 74 +++++++++++++++++++
>  2 files changed, 104 insertions(+)
>  create mode 100644 gdb/testsuite/gdb.arch/aarch64-brk-patterns.c
>  create mode 100644 gdb/testsuite/gdb.arch/aarch64-brk-patterns.exp
> 
> diff --git a/gdb/testsuite/gdb.arch/aarch64-brk-patterns.c b/gdb/testsuite/gdb.arch/aarch64-brk-patterns.c
> new file mode 100644
> index 0000000000..ccf9a35a94
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/aarch64-brk-patterns.c
> @@ -0,0 +1,30 @@
> +/* This file is part of GDB, the GNU debugger.
> +
> +   Copyright 2020 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/>.  */
> +
> +int main(void)
> +{
> +  /* Dummy instruction just so GDB doesn't stop at the first breakpoint
> +     instruction.  */
> +  __asm __volatile ("nop\n\t");
> +
> +  /* Multiple BRK instruction patterns.  */
> +  __asm __volatile ("brk %0\n\t" ::"n"(0x0));
> +  __asm __volatile ("brk %0\n\t" ::"n"(0x900 + 0xf));
> +  __asm __volatile ("brk %0\n\t" ::"n"(0xf000));
> +
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.arch/aarch64-brk-patterns.exp b/gdb/testsuite/gdb.arch/aarch64-brk-patterns.exp
> new file mode 100644
> index 0000000000..9a0ec81efa
> --- /dev/null
> +++ b/gdb/testsuite/gdb.arch/aarch64-brk-patterns.exp
> @@ -0,0 +1,74 @@
> +# Copyright 2020 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/>.
> +#
> +# This file is part of the gdb testsuite.
> +
> +# Test if GDB stops at various BRK instruction patterns inserted into
> +# the code.
> +
> +if {![is_aarch64_target]} {
> +    verbose "Skipping ${gdb_test_file_name}."
> +    return
> +}
> +
> +standard_testfile
> +if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile}]} {
> +    return -1
> +}
> +
> +if {![runto_main]} {
> +    untested "could not run to main"
> +    return -1
> +}
> +
> +# Number of expected SIGTRAP's to get.  This needs to be kept in sync
> +# with the source file.
> +set expected_traps 3
> +set keep_going 1
> +set count 0
> +set old_timeout $timeout
> +set timeout 10

Any reason you are changing the timeout?  There is nothing in the test that
looks like it would take time.

If changing the timeout is really necessary, look into using with_timeout_factor.

> +
> +while {$keep_going} {
> +
> +  set test "brk instruction $count causes SIGTRAP"

Instead of setting the test name like that, look into using the special $gdb_test_name
variable, available inside the gdb_test_multiple body.

> +
> +  # Continue to next program breakpoint instruction.
> +  gdb_test_multiple "continue" $test {
> +      -re "Program received signal SIGTRAP, Trace/breakpoint trap.*$gdb_prompt $" {
> +	  pass $test
> +
> +	  # Insert a breakpoint at the program breakpoint instruction so GDB
> +	  # can step over it.
> +	  gdb_test "break" \
> +	    "Breakpoint $decimal at $hex: file .*$srcfile, line $decimal.*" \
> +	    "insert breakpoint at brk instruction $count"
> +	  incr count
> +      }
> +      -re "exited normally.*$gdb_prompt $" {
> +	  set keep_going 0
> +      }
> +      timeout {
> +	  fail $test
> +	  set keep_going 0
> +      }
> +  }
> +}
> +
> +set timeout $old_timeout
> +
> +if {$count < $expected_traps} {
> +  fail "all brk instructions triggered."
> +}

Use gdb_assert.

Is there any reason why $count would be greater than $expected_taps?  If no,
I would test for "$count == $expected_traps".

Simon