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

["Christian Biesinger via gdb-patches" <gdb-patches@sourceware.org>]

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.

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
> >
>