Re: [RFC] [gdb/testsuite] Add xfail in gdb.base/hbreak.exp

[Luis Machado <luis.machado@arm.com>]

On 7/17/24 16:14, Luis Machado wrote:
> On 7/17/24 16:10, Tom de Vries wrote:
>> On an aarch64-linux system with 32-bit userland running in a chroot, and using
>> target board unix/mthumb I get:
>> ...
>> (gdb) hbreak hbreak.c:27^M
>> Hardware assisted breakpoint 2 at 0x4004e2: file hbreak.c, line 27.^M
> 
> That is a bit odd, but it goes through the compat layer, which is not exercised
> as often as the 32-bit code.
> 
> Let me see if I can reproduce this one on my end.

I managed to reproduce this. I checked with the kernel folks and this should
work, but I'm not sure where the error is coming from.

> 
> 
>> (gdb) PASS: gdb.base/hbreak.exp: hbreak
>> continue^M
>> Continuing.^M
>> Unexpected error setting breakpoint: Invalid argument.^M
>> (gdb) FAIL: gdb.base/hbreak.exp: continue to break-at-exit after hbreak
>> ...
>> due to this call in arm_linux_nat_target::low_prepare_to_resume:
>> ...
>>           if (ptrace (PTRACE_SETHBPREGS, pid,
>>               (PTRACE_TYPE_ARG3) ((i << 1) + 1), &bpts[i].address) < 0)
>>             perror_with_name (_("Unexpected error setting breakpoint"));
>> ...
>>
>> This problem does not happen if instead we use a 4-byte aligned address.
>>
>> I'm not sure if this is simply unsupported or if there's a kernel bug of some
>> sort, but I don't see what gdb can do about this.
>>
>> Tentatively mark this as xfail.
>>
>> Tested on aarch64-linux.
>> ---
>>  gdb/testsuite/gdb.base/hbreak.exp | 40 ++++++++++++++++++++++++++-----
>>  1 file changed, 34 insertions(+), 6 deletions(-)
>>
>> diff --git a/gdb/testsuite/gdb.base/hbreak.exp b/gdb/testsuite/gdb.base/hbreak.exp
>> index 73a3e2afb67..b140257a23e 100644
>> --- a/gdb/testsuite/gdb.base/hbreak.exp
>> +++ b/gdb/testsuite/gdb.base/hbreak.exp
>> @@ -27,10 +27,38 @@ if ![runto_main] {
>>  
>>  set breakline [gdb_get_line_number "break-at-exit"]
>>  
>> -gdb_test "hbreak ${srcfile}:${breakline}" \
>> -	 "Hardware assisted breakpoint \[0-9\]+ at 0x\[0-9a-f\]+: file .*${srcfile}, line ${breakline}\\." \
>> -	 "hbreak"
>> +set re_loc "file \[^\r\n\]*$srcfile, line $breakline"
>> +set re_dot [string_to_regexp .]
>>  
>> -gdb_test "continue" \
>> -	 "Continuing\\.\[ \r\n\]+Breakpoint \[0-9\]+, .*break-at-exit.*" \
>> -	 "continue to break-at-exit after hbreak"
>> +set addr 0x0
>> +gdb_test_multiple "hbreak ${srcfile}:${breakline}" "hbreak" {
>> +    -re -wrap "Hardware assisted breakpoint $decimal at ($hex): $re_loc$re_dot" {
>> +	set addr $expect_out(1,string)
>> +	pass $gdb_test_name
>> +    }
>> +}
>> +
>> +set have_xfail 0
>> +if { [istarget arm*-*-*] } {
>> +    # When running 32-bit userland on aarch64 kernel, thumb instructions that
>> +    # are not 4-byte aligned may not be supported for setting a hardware
>> +    # breakpoint on.
>> +    set have_xfail [expr ($addr & 0x2) == 2]
>> +}
>> +
>> +set re_xfail \
>> +    [string_to_regexp \
>> +	 "Unexpected error setting breakpoint: Invalid argument."]
>> +
>> +gdb_test_multiple "continue" "continue to break-at-exit after hbreak" {
>> +    -re -wrap "Continuing\\.\[ \r\n\]+Breakpoint \[0-9\]+, .*break-at-exit.*" {
>> +	pass $gdb_test_name
>> +    }
>> +    -re -wrap $re_xfail {
>> +	if { $have_xfail } {
>> +	    xfail $gdb_test_name
>> +	} else {
>> +	    fail $gdb_test_name
>> +	}
>> +    }
>> +}
>>
>> base-commit: 0ed152c5c6b3c72fc505b331ed77e08b438d643a
> 

In any case, I agree gdb doesn't have a better way to deal with it.

Approved-By: Luis Machado <luis.machado@arm.com>