Re: [PATCH] Fix arm-netbsd build error

["Christian Biesinger via gdb-patches" <gdb-patches at sourceware dot org>]

On Wed, Feb 12, 2020 at 7:29 AM Alan Hayward <Alan.Hayward@arm.com> wrote:
>
>
>
> > On 11 Feb 2020, at 23:34, Christian Biesinger via gdb-patches <gdb-patches@sourceware.org> wrote:
> >
> > On Tue, Feb 11, 2020 at 4:55 PM Christian Biesinger
> > <cbiesinger@google.com> wrote:
> >>
> >> 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.
> >>
> >> Tested by compiling on arm-netbsd on qemu. For actually testing, there
> >> seems to be something missing as "info registers" only shows FPA
> >> registers and no VFP ones. I am still investigating why this is;
> >> please let me know if you know. However, I think this is still good
> >> to check in as-is.
> >
> > Hm... this is perhaps because arm_netbsd_nat_target does not implement
> > read_description; if it returned arm_read_description
> > (ARM_FP_TYPE_VFPV2) this may work?
> >
>
> Yes, looks like netbsd isn’t using any target description functionality.
>
> I suspect the code is getting into arm_gdbarch_init() with a null tdesc,
> and then using the AUTO setting. But that’s just a guess.
>
> Implementing read_description as you suggest should help. However,
> read_description should probably do HWCAP checking similar to the
> arm_linux_nat_target and arm_fbsd_nat_target versions.
>
> Without that, I’d worry that your patch below might start writing off the
> end of the regcache that had been allocated for a fewer number of registers.

Hm... well, I've probably spent entirely too much time on this
already, but just in case there's an easy fix -- Kamil, does NetBSD
provide an API similar to Linux's HWCAP API that would let me check
which VFP version the current CPU is using? It seems AUXV does not
contain HWCAP data on NetBSD, unlike Linux/FreeBSD, though I may be
missing something.

(Compare arm_fbsd_read_description_auxv /
arm_linux_nat_target::read_description)

Christian

>
> >>
> >> 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.
> >>        (fetch_elfcore_registers): Update.
> >> ---
> >> gdb/arm-nbsd-nat.c | 80 ++++++++++++++++++++--------------------------
> >> 1 file changed, 34 insertions(+), 46 deletions(-)
> >>
> >> diff --git a/gdb/arm-nbsd-nat.c b/gdb/arm-nbsd-nat.c
> >> index 11afc289c3..8027f54dfe 100644
> >> --- a/gdb/arm-nbsd-nat.c
> >> +++ b/gdb/arm-nbsd-nat.c
> >> @@ -65,15 +65,13 @@ 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;
> >> -
> >> -  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 = ARM_D0_REGNUM; regno <= ARM_D31_REGNUM; regno++)
> >> +    regcache->raw_supply (regno, (char *) &vfp.vfp_regs[regno - ARM_D0_REGNUM]);
> >>
> >> -  regcache->raw_supply (ARM_FPS_REGNUM, (char *) &fparegset->fpr_fpsr);
> >> +  regcache->raw_supply (ARM_FPSCR_REGNUM, (char *) &vfp.vfp_fpscr);
> >> }
> >>
> >> static void
> >> @@ -147,10 +145,10 @@ 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 +156,15 @@ fetch_fp_register (struct regcache *regcache, int regno)
> >>       return;
> >>     }
> >>
> >> -  switch (regno)
> >> +  if (regno == ARM_FPSCR_REGNUM)
> >> +    regcache->raw_supply (ARM_FPSCR_REGNUM, (char *) &vfp.vfp_fpscr);
> >> +  else if (regno >= ARM_D0_REGNUM && regno <= ARM_D31_REGNUM)
> >>     {
> >> -    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 +183,7 @@ fetch_fp_regs (struct regcache *regcache)
> >>       return;
> >>     }
> >>
> >> -  arm_supply_fparegset (regcache, &inferior_fp_registers);
> >> +  arm_supply_vfpregset (regcache, &inferior_fp_registers);
> >> }
> >>
> >> void
> >> @@ -327,10 +322,9 @@ 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 +332,15 @@ store_fp_register (const struct regcache *regcache, int regno)
> >>       return;
> >>     }
> >>
> >> -  switch (regno)
> >> +  if (regno == ARM_FPSCR_REGNUM)
> >> +    regcache->raw_collect (ARM_FPSCR_REGNUM, (char *) &vfp.vfp_fpscr);
> >> +  else if (regno >= ARM_D0_REGNUM && regno <= ARM_D31_REGNUM)
> >>     {
> >> -    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 +352,17 @@ 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 fpreg fpregs;
> >>
> >> -
> >> -  for (regno = ARM_F0_REGNUM; regno <= ARM_F7_REGNUM; regno++)
> >> +  for (int regno = ARM_D0_REGNUM; regno <= ARM_D31_REGNUM; regno++)
> >>     regcache->raw_collect
> >> -      (regno, (char *) &inferior_fp_registers.fpr[regno - ARM_F0_REGNUM]);
> >> +      (regno, (char *) &fpregs.fpr_vfp.vfp_regs[regno - ARM_D0_REGNUM]);
> >>
> >> -  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"));
> >> @@ -427,7 +415,7 @@ fetch_elfcore_registers (struct regcache *regcache,
> >>          /* 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);
> >> +         arm_supply_vfpregset (regcache, &fparegset);
> >>        }
> >>       break;
> >>
> >> --
> >> 2.25.0.225.g125e21ebc7-goog
> >>
>