binutils-gdb/gdb/ppc-obsd-tdep.c

/* Target-dependent code for OpenBSD/powerpc.

   Copyright (C) 2004-2025 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "arch-utils.h"
#include "extract-store-integer.h"
#include "frame.h"
#include "frame-unwind.h"
#include "gdbtypes.h"
#include "osabi.h"
#include "regcache.h"
#include "regset.h"
#include "symtab.h"
#include "trad-frame.h"

#include "ppc-tdep.h"
#include "ppc-obsd-tdep.h"
#include "solib-svr4.h"

/* Register offsets from <machine/reg.h>.  */
struct ppc_reg_offsets ppcobsd_reg_offsets;
struct ppc_reg_offsets ppcobsd_fpreg_offsets;


/* Core file support.  */

/* Supply register REGNUM in the general-purpose register set REGSET
   from the buffer specified by GREGS and LEN to register cache
   REGCACHE.  If REGNUM is -1, do this for all registers in REGSET.  */

void
ppcobsd_supply_gregset (const struct regset *regset,
			struct regcache *regcache, int regnum,
			const void *gregs, size_t len)
{
  ppc_supply_gregset (regset, regcache, regnum, gregs, len);
  ppc_supply_fpregset (regset, regcache, regnum, gregs, len);
}

/* Collect register REGNUM in the general-purpose register set
   REGSET, from register cache REGCACHE into the buffer specified by
   GREGS and LEN.  If REGNUM is -1, do this for all registers in
   REGSET.  */

void
ppcobsd_collect_gregset (const struct regset *regset,
			 const struct regcache *regcache, int regnum,
			 void *gregs, size_t len)
{
  ppc_collect_gregset (regset, regcache, regnum, gregs, len);
  ppc_collect_fpregset (regset, regcache, regnum, gregs, len);
}

/* OpenBSD/powerpc register set.  */

const struct regset ppcobsd_gregset =
{
  &ppcobsd_reg_offsets,
  ppcobsd_supply_gregset
};

const struct regset ppcobsd_fpregset =
{
  &ppcobsd_fpreg_offsets,
  ppc_supply_fpregset
};

/* Iterate over core file register note sections.  */

static void
ppcobsd_iterate_over_regset_sections (struct gdbarch *gdbarch,
				      iterate_over_regset_sections_cb *cb,
				      void *cb_data,
				      const struct regcache *regcache)
{
  cb (".reg", 412, 412, &ppcobsd_gregset, NULL, cb_data);
}


/* Signal trampolines.  */

/* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page
   in virtual memory.  The randomness makes it somewhat tricky to
   detect it, but fortunately we can rely on the fact that the start
   of the sigtramp routine is page-aligned.  We recognize the
   trampoline by looking for the code that invokes the sigreturn
   system call.  The offset where we can find that code varies from
   release to release.

   By the way, the mapping mentioned above is read-only, so you cannot
   place a breakpoint in the signal trampoline.  */

/* Default page size.  */
static const int ppcobsd_page_size = 4096;

/* Offset for sigreturn(2).  */
static const int ppcobsd_sigreturn_offset[] = {
  0x98,				/* OpenBSD 3.8 */
  0x0c,				/* OpenBSD 3.2 */
  -1
};

static int
ppcobsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
				const frame_info_ptr &this_frame,
				void **this_cache)
{
  struct gdbarch *gdbarch = get_frame_arch (this_frame);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  CORE_ADDR pc = get_frame_pc (this_frame);
  CORE_ADDR start_pc = (pc & ~(ppcobsd_page_size - 1));
  const int *offset;
  const char *name;

  find_pc_partial_function (pc, &name, NULL, NULL);
  if (name)
    return 0;

  for (offset = ppcobsd_sigreturn_offset; *offset != -1; offset++)
    {
      gdb_byte buf[2 * PPC_INSN_SIZE];
      unsigned long insn;

      if (!safe_frame_unwind_memory (this_frame, start_pc + *offset,
				     {buf, sizeof buf}))
	continue;

      /* Check for "li r0,SYS_sigreturn".  */
      insn = extract_unsigned_integer (buf, PPC_INSN_SIZE, byte_order);
      if (insn != 0x38000067)
	continue;

      /* Check for "sc".  */
      insn = extract_unsigned_integer (buf + PPC_INSN_SIZE,
				       PPC_INSN_SIZE, byte_order);
      if (insn != 0x44000002)
	continue;

      return 1;
    }

  return 0;
}

static struct trad_frame_cache *
ppcobsd_sigtramp_frame_cache (const frame_info_ptr &this_frame, void **this_cache)
{
  struct gdbarch *gdbarch = get_frame_arch (this_frame);
  ppc_gdbarch_tdep *tdep = gdbarch_tdep<ppc_gdbarch_tdep> (gdbarch);
  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  struct trad_frame_cache *cache;
  CORE_ADDR addr, base, func;
  gdb_byte buf[PPC_INSN_SIZE];
  unsigned long insn, sigcontext_offset;
  int i;

  if (*this_cache)
    return (struct trad_frame_cache *) *this_cache;

  cache = trad_frame_cache_zalloc (this_frame);
  *this_cache = cache;

  func = get_frame_pc (this_frame);
  func &= ~(ppcobsd_page_size - 1);
  if (!safe_frame_unwind_memory (this_frame, func, {buf, sizeof buf}))
    return cache;

  /* Calculate the offset where we can find `struct sigcontext'.  We
     base our calculation on the amount of stack space reserved by the
     first instruction of the signal trampoline.  */
  insn = extract_unsigned_integer (buf, PPC_INSN_SIZE, byte_order);
  sigcontext_offset = (0x10000 - (insn & 0x0000ffff)) + 8;

  base = get_frame_register_unsigned (this_frame, gdbarch_sp_regnum (gdbarch));
  addr = base + sigcontext_offset + 2 * tdep->wordsize;
  for (i = 0; i < ppc_num_gprs; i++, addr += tdep->wordsize)
    {
      int regnum = i + tdep->ppc_gp0_regnum;
      trad_frame_set_reg_addr (cache, regnum, addr);
    }
  trad_frame_set_reg_addr (cache, tdep->ppc_lr_regnum, addr);
  addr += tdep->wordsize;
  trad_frame_set_reg_addr (cache, tdep->ppc_cr_regnum, addr);
  addr += tdep->wordsize;
  trad_frame_set_reg_addr (cache, tdep->ppc_xer_regnum, addr);
  addr += tdep->wordsize;
  trad_frame_set_reg_addr (cache, tdep->ppc_ctr_regnum, addr);
  addr += tdep->wordsize;
  trad_frame_set_reg_addr (cache, gdbarch_pc_regnum (gdbarch), addr);
  /* SRR0?  */
  addr += tdep->wordsize;

  /* Construct the frame ID using the function start.  */
  trad_frame_set_id (cache, frame_id_build (base, func));

  return cache;
}

static void
ppcobsd_sigtramp_frame_this_id (const frame_info_ptr &this_frame,
				void **this_cache, struct frame_id *this_id)
{
  struct trad_frame_cache *cache =
    ppcobsd_sigtramp_frame_cache (this_frame, this_cache);

  trad_frame_get_id (cache, this_id);
}

static struct value *
ppcobsd_sigtramp_frame_prev_register (const frame_info_ptr &this_frame,
				      void **this_cache, int regnum)
{
  struct trad_frame_cache *cache =
    ppcobsd_sigtramp_frame_cache (this_frame, this_cache);

  return trad_frame_get_register (cache, this_frame, regnum);
}

static const struct frame_unwind_legacy ppcobsd_sigtramp_frame_unwind (
  "ppc openbsd sigtramp",
  SIGTRAMP_FRAME,
  FRAME_UNWIND_ARCH,
  default_frame_unwind_stop_reason,
  ppcobsd_sigtramp_frame_this_id,
  ppcobsd_sigtramp_frame_prev_register,
  NULL,
  ppcobsd_sigtramp_frame_sniffer
);


static void
ppcobsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
{
  /* OpenBSD doesn't support the 128-bit `long double' from the psABI.  */
  set_gdbarch_long_double_bit (gdbarch, 64);
  set_gdbarch_long_double_format (gdbarch, floatformats_ieee_double);

  /* OpenBSD currently uses a broken GCC.  */
  set_gdbarch_return_value (gdbarch, ppc_sysv_abi_broken_return_value);

  /* OpenBSD uses SVR4-style shared libraries.  */
  set_solib_svr4_ops (gdbarch, make_svr4_ilp32_solib_ops);

  set_gdbarch_iterate_over_regset_sections
    (gdbarch, ppcobsd_iterate_over_regset_sections);

  frame_unwind_append_unwinder (gdbarch, &ppcobsd_sigtramp_frame_unwind);
}

INIT_GDB_FILE (ppcobsd_tdep)
{
  gdbarch_register_osabi (bfd_arch_rs6000, 0, GDB_OSABI_OPENBSD,
			  ppcobsd_init_abi);
  gdbarch_register_osabi (bfd_arch_powerpc, 0, GDB_OSABI_OPENBSD,
			  ppcobsd_init_abi);

  /* Avoid initializing the register offsets again if they were
     already initialized by ppcobsd-nat.c.  */
  if (ppcobsd_reg_offsets.pc_offset == 0)
    {
      /* General-purpose registers.  */
      ppcobsd_reg_offsets.r0_offset = 0;
      ppcobsd_reg_offsets.gpr_size = 4;
      ppcobsd_reg_offsets.xr_size = 4;
      ppcobsd_reg_offsets.pc_offset = 384;
      ppcobsd_reg_offsets.ps_offset = 388;
      ppcobsd_reg_offsets.cr_offset = 392;
      ppcobsd_reg_offsets.lr_offset = 396;
      ppcobsd_reg_offsets.ctr_offset = 400;
      ppcobsd_reg_offsets.xer_offset = 404;
      ppcobsd_reg_offsets.mq_offset = 408;

      /* Floating-point registers.  */
      ppcobsd_reg_offsets.f0_offset = 128;
      ppcobsd_reg_offsets.fpscr_offset = -1;

    }

  if (ppcobsd_fpreg_offsets.fpscr_offset == 0)
    {
      /* Floating-point registers.  */
      ppcobsd_reg_offsets.f0_offset = 0;
      ppcobsd_reg_offsets.fpscr_offset = 256;
      ppcobsd_reg_offsets.fpscr_size = 4;
    }
}