Re: [RFC PATCH] tests/tcg: finesse the registers check for "hidden" regs

["Nicholas Piggin" <npiggin@gmail.com>]

On Fri Nov 17, 2023 at 3:39 AM AEST, Alex Bennée wrote:
> The reason the ppc64 and s390x test where failing was because gdb
> hides them although they are still accessible via regnum. We can
> re-arrange the test a little bit and include these two arches in our
> test.
>
> We still don't explicitly fail for registers that just disappear like
> in the ARM case:
>
>   xml-tdesc has 228 registers
>   remote-registers has 219 registers
>   of which 0 are hidden
>   {'name': 'CNTP_CVAL', 'regnum': 96} wasn't seen in remote-registers
>   {'name': 'CNTV_CVAL', 'regnum': 101} wasn't seen in remote-registers
>   {'name': 'PAR', 'regnum': 113} wasn't seen in remote-registers
>   {'name': 'CPUACTLR', 'regnum': 114} wasn't seen in remote-registers
>   {'name': 'CPUECTLR', 'regnum': 127} wasn't seen in remote-registers
>   {'name': 'CPUMERRSR', 'regnum': 140} wasn't seen in remote-registers
>   {'name': 'TTBR1', 'regnum': 148} wasn't seen in remote-registers
>   {'name': 'L2MERRSR', 'regnum': 161} wasn't seen in remote-registers
>   {'name': 'TTBR0', 'regnum': 168} wasn't seen in remote-registers

Nice! Thanks for getting ppc64 working, comment below.

>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> Cc: Ilya Leoshkevich <iii@linux.ibm.com>
> Cc: qemu-s390x@nongnu.org
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Daniel Henrique Barboza <danielhb413@gmail.com>
> Cc: qemu-ppc@nongnu.org
> Cc: Luis Machado <luis.machado@arm.com>
> ---
>  tests/tcg/multiarch/gdbstub/registers.py | 80 ++++++++++++++++++------
>  tests/tcg/ppc64/Makefile.target          |  7 ---
>  tests/tcg/s390x/Makefile.target          |  4 --
>  3 files changed, 61 insertions(+), 30 deletions(-)
>
> diff --git a/tests/tcg/multiarch/gdbstub/registers.py b/tests/tcg/multiarch/gdbstub/registers.py
> index ff6076b09e..342d6fd78f 100644
> --- a/tests/tcg/multiarch/gdbstub/registers.py
> +++ b/tests/tcg/multiarch/gdbstub/registers.py
> @@ -44,7 +44,6 @@ def fetch_xml_regmap():
>  
>      total_regs = 0
>      reg_map = {}
> -    frame = gdb.selected_frame()
>  
>      tree = ET.fromstring(xml)
>      for f in tree.findall("feature"):
> @@ -61,12 +60,8 @@ def fetch_xml_regmap():
>          for r in regs:
>              name = r.attrib["name"]
>              regnum = int(r.attrib["regnum"])
> -            try:
> -                value = frame.read_register(name)
> -            except ValueError:
> -                report(False, f"failed to read reg: {name}")
>  
> -            entry = { "name": name, "initial": value, "regnum": regnum }
> +            entry = { "name": name, "regnum": regnum }
>  
>              if name in reg_map:
>                  report(False, f"duplicate register {entry} vs {reg_map[name]}")
> @@ -80,6 +75,15 @@ def fetch_xml_regmap():
>  
>      return reg_map
>  
> +def get_register_by_regnum(reg_map, regnum):
> +    """
> +    Helper to find a register from the map via its XML regnum
> +    """
> +    for regname, entry in reg_map.items():
> +        if entry['regnum'] == regnum:
> +            return entry
> +    return None
> +
>  def crosscheck_remote_xml(reg_map):
>      """
>      Cross-check the list of remote-registers with the XML info.
> @@ -90,6 +94,7 @@ def crosscheck_remote_xml(reg_map):
>  
>      total_regs = len(reg_map.keys())
>      total_r_regs = 0
> +    total_r_elided_regs = 0
>  
>      for r in r_regs:
>          fields = r.split()
> @@ -100,6 +105,15 @@ def crosscheck_remote_xml(reg_map):
>              r_name = fields[0]
>              r_regnum = int(fields[6])
>  
> +            # Some registers are "hidden" so don't have a name
> +            # although they still should have a register number
> +            if r_name == "''":
> +                total_r_elided_regs += 1

Should this also increment total_r_regs so that it doesn't trip the
warning?

Thanks,
Nick

> +                x_reg = get_register_by_regnum(reg_map, r_regnum)
> +                if x_reg is not None:
> +                    x_reg["hidden"] = True
> +                continue
> +
>              # check in the XML
>              try:
>                  x_reg = reg_map[r_name]
> @@ -118,14 +132,40 @@ def crosscheck_remote_xml(reg_map):
>      # registers on a 32 bit machine. Also print what is missing to
>      # help with debug.
>      if total_regs != total_r_regs:
> -        print(f"xml-tdesc has ({total_regs}) registers")
> -        print(f"remote-registers has ({total_r_regs}) registers")
> +        print(f"xml-tdesc has {total_regs} registers")
> +        print(f"remote-registers has {total_r_regs} registers")
> +        print(f"of which {total_r_elided_regs} are hidden")
>  
>          for x_key in reg_map.keys():
>              x_reg = reg_map[x_key]
> -            if "seen" not in x_reg:
> +            if "hidden" in x_reg:
> +                print(f"{x_reg} elided by gdb")
> +            elif "seen" not in x_reg:
>                  print(f"{x_reg} wasn't seen in remote-registers")
>  
> +def initial_register_read(reg_map):
> +    """
> +    Do an initial read of all registers that we know gdb cares about
> +    (so ignore the elided ones).
> +    """
> +    frame = gdb.selected_frame()
> +
> +    for e in reg_map.values():
> +        name = e["name"]
> +        regnum = e["regnum"]
> +
> +        try:
> +            if "hidden" in e:
> +                value = frame.read_register(regnum)
> +                e["initial"] = value
> +            elif "seen" in e:
> +                value = frame.read_register(name)
> +                e["initial"] = value
> +
> +        except ValueError:
> +                report(False, f"failed to read reg: {name}")
> +
> +
>  def complete_and_diff(reg_map):
>      """
>      Let the program run to (almost) completion and then iterate
> @@ -144,18 +184,19 @@ def complete_and_diff(reg_map):
>      changed = 0
>  
>      for e in reg_map.values():
> -        name = e["name"]
> -        old_val = e["initial"]
> +        if "initial" in e and "hidden" not in e:
> +            name = e["name"]
> +            old_val = e["initial"]
>  
> -        try:
> -            new_val = frame.read_register(name)
> -        except:
> -            report(False, f"failed to read {name} at end of run")
> -            continue
> +            try:
> +                new_val = frame.read_register(name)
> +            except ValueError:
> +                report(False, f"failed to read {name} at end of run")
> +                continue
>  
> -        if new_val != old_val:
> -            print(f"{name} changes from {old_val} to {new_val}")
> -            changed += 1
> +            if new_val != old_val:
> +                print(f"{name} changes from {old_val} to {new_val}")
> +                changed += 1
>  
>      # as long as something changed we can be confident its working
>      report(changed > 0, f"{changed} registers were changed")
> @@ -168,6 +209,7 @@ def run_test():
>  
>      if reg_map is not None:
>          crosscheck_remote_xml(reg_map)
> +        initial_register_read(reg_map)
>          complete_and_diff(reg_map)
>  
>  
> diff --git a/tests/tcg/ppc64/Makefile.target b/tests/tcg/ppc64/Makefile.target
> index 1d08076756..5721c159f2 100644
> --- a/tests/tcg/ppc64/Makefile.target
> +++ b/tests/tcg/ppc64/Makefile.target
> @@ -38,11 +38,4 @@ PPC64_TESTS += signal_save_restore_xer
>  PPC64_TESTS += xxspltw
>  PPC64_TESTS += test-aes
>  
> -ifneq ($(GDB),)
> -# Skip for now until vsx registers sorted out
> -run-gdbstub-registers:
> -	$(call skip-test, $<, "BROKEN reading VSX registers")
> -endif
> -
> -
>  TESTS += $(PPC64_TESTS)
> diff --git a/tests/tcg/s390x/Makefile.target b/tests/tcg/s390x/Makefile.target
> index 46544fecd4..0e670f3f8b 100644
> --- a/tests/tcg/s390x/Makefile.target
> +++ b/tests/tcg/s390x/Makefile.target
> @@ -103,10 +103,6 @@ run-gdbstub-svc: hello-s390x-asm
>  		--bin $< --test $(S390X_SRC)/gdbstub/test-svc.py, \
>  	single-stepping svc)
>  
> -# Skip for now until vx registers sorted out
> -run-gdbstub-registers:
> -	$(call skip-test, $<, "BROKEN reading VX registers")
> -
>  EXTRA_RUNS += run-gdbstub-signals-s390x run-gdbstub-svc
>  endif
>