Re: [PATCH v3] Fix arm-netbsd build error: convert from FPA to VFP

[Kamil Rytarowski <n54 at gmx dot com>]

On 02.03.2020 18:28, Christian Biesinger via gdb-patches wrote:
> On Mon, Mar 2, 2020 at 5:42 AM Alan Hayward <Alan.Hayward@arm.com> wrote:
>>> On 28 Feb 2020, at 19:19, Christian Biesinger via gdb-patches <gdb-patches@sourceware.org> wrote:
>>>
>>> Hi Alan,
>>>
>>> there is already a num_vfp_registers field in tdep, so I thought it easiest
>>> to just use that. Does that look good? See below.
>>>
>>
>> That works for the ARM_FP_TYPE_NONE case.
>>
>> I had to convince myself it works for the aarch32_read_description case.
>> And after thinking it through, I’m happy because both have the same size
>> FP register banks.
>>
>> So, ok to push.
> 
> Thanks! Pushing now with a minor change in {fetch,store}_fp_register
> to not fetch/store ARM_FPSCR_REGNUM if tdep->vfp_register_count == 0.
> 

Thank you! Great work.

> Christian
> 
>>> The floating point register interface has changed to this:
>>> https://github.com/NetBSD/src/blob/trunk/sys/arch/arm/include/reg.h
>>>
>>> It now uses VFP instead of FPA registers. This patch updates
>>> arm-nbsd-nat.c accordingly.
>>>
>>> Also implements read_description so that these registers are correctly
>>> printed by "info registers" et al.
>>>
>>> Tested by compiling & running on arm-netbsd on qemu.
>>>
>>> gdb/ChangeLog:
>>>
>>> 2020-02-11  Christian Biesinger  <cbiesinger@google.com>
>>>
>>>       * arm-nbsd-nat.c (arm_supply_fparegset): Rename to...
>>>       (arm_supply_vfpregset): ...this, and update to use VFP registers.
>>>       (fetch_fp_register): Update.
>>>       (fetch_fp_regs): Update.
>>>       (store_fp_register): Update.
>>>       (store_fp_regs): Update.
>>>       (arm_netbsd_nat_target::read_description): New function.
>>>       (fetch_elfcore_registers): Update.
>>> ---
>>> gdb/arm-nbsd-nat.c | 121 +++++++++++++++++++++++++--------------------
>>> 1 file changed, 68 insertions(+), 53 deletions(-)
>>>
>>> diff --git a/gdb/arm-nbsd-nat.c b/gdb/arm-nbsd-nat.c
>>> index 11afc289c3..cee7917db2 100644
>>> --- a/gdb/arm-nbsd-nat.c
>>> +++ b/gdb/arm-nbsd-nat.c
>>> @@ -26,10 +26,12 @@
>>> #include "target.h"
>>> #include <sys/types.h>
>>> #include <sys/ptrace.h>
>>> +#include <sys/sysctl.h>
>>> #include <machine/reg.h>
>>> #include <machine/frame.h>
>>>
>>> #include "arm-tdep.h"
>>> +#include "aarch32-tdep.h"
>>> #include "inf-ptrace.h"
>>>
>>> class arm_netbsd_nat_target final : public inf_ptrace_target
>>> @@ -38,6 +40,7 @@ public:
>>>   /* Add our register access methods.  */
>>>   void fetch_registers (struct regcache *, int) override;
>>>   void store_registers (struct regcache *, int) override;
>>> +  const struct target_desc *read_description () override;
>>> };
>>>
>>> static arm_netbsd_nat_target the_arm_netbsd_nat_target;
>>> @@ -65,15 +68,17 @@ arm_supply_gregset (struct regcache *regcache, struct reg *gregset)
>>> }
>>>
>>> static void
>>> -arm_supply_fparegset (struct regcache *regcache, struct fpreg *fparegset)
>>> +arm_supply_vfpregset (struct regcache *regcache, struct fpreg *fpregset)
>>> {
>>> -  int regno;
>>> +  struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
>>> +  if (tdep->vfp_register_count == 0)
>>> +    return;
>>>
>>> -  for (regno = ARM_F0_REGNUM; regno <= ARM_F7_REGNUM; regno++)
>>> -    regcache->raw_supply (regno,
>>> -                       (char *) &fparegset->fpr[regno - ARM_F0_REGNUM]);
>>> +  struct vfpreg &vfp = fpregset->fpr_vfp;
>>> +  for (int regno = 0; regno <= tdep->vfp_register_count; regno++)
>>> +    regcache->raw_supply (regno + ARM_D0_REGNUM, (char *) &vfp.vfp_regs[regno]);
>>>
>>> -  regcache->raw_supply (ARM_FPS_REGNUM, (char *) &fparegset->fpr_fpsr);
>>> +  regcache->raw_supply (ARM_FPSCR_REGNUM, (char *) &vfp.vfp_fpscr);
>>> }
>>>
>>> static void
>>> @@ -147,10 +152,10 @@ static void
>>> fetch_fp_register (struct regcache *regcache, int regno)
>>> {
>>>   struct fpreg inferior_fp_registers;
>>> -  int ret;
>>> +  int ret = ptrace (PT_GETFPREGS, regcache->ptid ().pid (),
>>> +                 (PTRACE_TYPE_ARG3) &inferior_fp_registers, 0);
>>>
>>> -  ret = ptrace (PT_GETFPREGS, regcache->ptid ().pid (),
>>> -             (PTRACE_TYPE_ARG3) &inferior_fp_registers, 0);
>>> +  struct vfpreg &vfp = inferior_fp_registers.fpr_vfp;
>>>
>>>   if (ret < 0)
>>>     {
>>> @@ -158,18 +163,17 @@ fetch_fp_register (struct regcache *regcache, int regno)
>>>       return;
>>>     }
>>>
>>> -  switch (regno)
>>> +  struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
>>> +  if (regno == ARM_FPSCR_REGNUM)
>>> +    regcache->raw_supply (ARM_FPSCR_REGNUM, (char *) &vfp.vfp_fpscr);
>>> +  else if (regno >= ARM_D0_REGNUM
>>> +        && regno <= ARM_D0_REGNUM + tdep->vfp_register_count)
>>>     {
>>> -    case ARM_FPS_REGNUM:
>>> -      regcache->raw_supply (ARM_FPS_REGNUM,
>>> -                         (char *) &inferior_fp_registers.fpr_fpsr);
>>> -      break;
>>> -
>>> -    default:
>>> -      regcache->raw_supply
>>> -     (regno, (char *) &inferior_fp_registers.fpr[regno - ARM_F0_REGNUM]);
>>> -      break;
>>> +      regcache->raw_supply (regno,
>>> +                         (char *) &vfp.vfp_regs[regno - ARM_D0_REGNUM]);
>>>     }
>>> +  else
>>> +    warning (_("Invalid register number."));
>>> }
>>>
>>> static void
>>> @@ -188,7 +192,7 @@ fetch_fp_regs (struct regcache *regcache)
>>>       return;
>>>     }
>>>
>>> -  arm_supply_fparegset (regcache, &inferior_fp_registers);
>>> +  arm_supply_vfpregset (regcache, &inferior_fp_registers);
>>> }
>>>
>>> void
>>> @@ -327,10 +331,9 @@ static void
>>> store_fp_register (const struct regcache *regcache, int regno)
>>> {
>>>   struct fpreg inferior_fp_registers;
>>> -  int ret;
>>> -
>>> -  ret = ptrace (PT_GETFPREGS, regcache->ptid ().pid (),
>>> -             (PTRACE_TYPE_ARG3) &inferior_fp_registers, 0);
>>> +  int ret = ptrace (PT_GETFPREGS, regcache->ptid ().pid (),
>>> +                 (PTRACE_TYPE_ARG3) &inferior_fp_registers, 0);
>>> +  struct vfpreg &vfp = inferior_fp_registers.fpr_vfp;
>>>
>>>   if (ret < 0)
>>>     {
>>> @@ -338,18 +341,17 @@ store_fp_register (const struct regcache *regcache, int regno)
>>>       return;
>>>     }
>>>
>>> -  switch (regno)
>>> +  struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
>>> +  if (regno == ARM_FPSCR_REGNUM)
>>> +    regcache->raw_collect (ARM_FPSCR_REGNUM, (char *) &vfp.vfp_fpscr);
>>> +  else if (regno >= ARM_D0_REGNUM
>>> +        && regno <= ARM_D0_REGNUM + tdep->vfp_register_count)
>>>     {
>>> -    case ARM_FPS_REGNUM:
>>> -      regcache->raw_collect (ARM_FPS_REGNUM,
>>> -                          (char *) &inferior_fp_registers.fpr_fpsr);
>>> -      break;
>>> -
>>> -    default:
>>> -      regcache->raw_collect
>>> -     (regno, (char *) &inferior_fp_registers.fpr[regno - ARM_F0_REGNUM]);
>>> -      break;
>>> +      regcache->raw_collect (regno,
>>> +                          (char *) &vfp.vfp_regs[regno - ARM_D0_REGNUM]);
>>>     }
>>> +  else
>>> +    warning (_("Invalid register number."));
>>>
>>>   ret = ptrace (PT_SETFPREGS, regcache->ptid ().pid (),
>>>               (PTRACE_TYPE_ARG3) &inferior_fp_registers, 0);
>>> @@ -361,20 +363,20 @@ store_fp_register (const struct regcache *regcache, int regno)
>>> static void
>>> store_fp_regs (const struct regcache *regcache)
>>> {
>>> -  struct fpreg inferior_fp_registers;
>>> -  int ret;
>>> -  int regno;
>>> -
>>> +  struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
>>> +  if (tdep->vfp_register_count == 0)
>>> +    return;
>>>
>>> -  for (regno = ARM_F0_REGNUM; regno <= ARM_F7_REGNUM; regno++)
>>> +  struct fpreg fpregs;
>>> +  for (int regno = 0; regno <= tdep->vfp_register_count; regno++)
>>>     regcache->raw_collect
>>> -      (regno, (char *) &inferior_fp_registers.fpr[regno - ARM_F0_REGNUM]);
>>> +      (regno + ARM_D0_REGNUM, (char *) &fpregs.fpr_vfp.vfp_regs[regno]);
>>>
>>> -  regcache->raw_collect (ARM_FPS_REGNUM,
>>> -                      (char *) &inferior_fp_registers.fpr_fpsr);
>>> +  regcache->raw_collect (ARM_FPSCR_REGNUM,
>>> +                      (char *) &fpregs.fpr_vfp.vfp_fpscr);
>>>
>>> -  ret = ptrace (PT_SETFPREGS, regcache->ptid ().pid (),
>>> -             (PTRACE_TYPE_ARG3) &inferior_fp_registers, 0);
>>> +  int ret = ptrace (PT_SETFPREGS, regcache->ptid ().pid (),
>>> +                 (PTRACE_TYPE_ARG3) &fpregs, 0);
>>>
>>>   if (ret < 0)
>>>     warning (_("unable to store floating-point registers"));
>>> @@ -397,6 +399,23 @@ arm_netbsd_nat_target::store_registers (struct regcache *regcache, int regno)
>>>     }
>>> }
>>>
>>> +const struct target_desc *
>>> +arm_netbsd_nat_target::read_description ()
>>> +{
>>> +  int flag;
>>> +  size_t len = sizeof (flag);
>>> +
>>> +  if (sysctlbyname("machdep.fpu_present", &flag, &len, NULL, 0) != 0
>>> +      || !flag)
>>> +    return arm_read_description (ARM_FP_TYPE_NONE);
>>> +
>>> +  len = sizeof(flag);
>>> +  if (sysctlbyname("machdep.neon_present", &flag, &len, NULL, 0) == 0 && flag)
>>> +    return aarch32_read_description ();
>>> +
>>> +  return arm_read_description (ARM_FP_TYPE_VFPV3);
>>> +}
>>> +
>>> static void
>>> fetch_elfcore_registers (struct regcache *regcache,
>>>                        gdb_byte *core_reg_sect, unsigned core_reg_size,
>>> @@ -420,15 +439,11 @@ fetch_elfcore_registers (struct regcache *regcache,
>>>       break;
>>>
>>>     case 2:
>>> -      if (core_reg_size != sizeof (struct fpreg))
>>> -     warning (_("wrong size of FPA register set in core file"));
>>> -      else
>>> -     {
>>> -       /* The memcpy may be unnecessary, but we can't really be sure
>>> -          of the alignment of the data in the core file.  */
>>> -       memcpy (&fparegset, core_reg_sect, sizeof (fparegset));
>>> -       arm_supply_fparegset (regcache, &fparegset);
>>> -     }
>>> +      /* cbiesinger/2020-02-12 -- as far as I can tell, ARM/NetBSD does
>>> +         not write any floating point registers into the core file (tested
>>> +      with NetBSD 9.1_RC1).  When it does, this block will need to read them,
>>> +      and the arm-netbsd gdbarch will need a core_read_description function
>>> +      to return the right description for them.  */
>>>       break;
>>>
>>>     default:
>>> --
>>> 2.25.0.265.gbab2e86ba0-goog
>>>
>>

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