gcc/libgcc/config/rs6000/linux-unwind.h

/* DWARF2 EH unwinding support for PowerPC and PowerPC64 Linux.
   Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.

   This file is part of GCC.

   GCC 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, or (at your
   option) any later version.

   GCC 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.

   Under Section 7 of GPL version 3, you are granted additional
   permissions described in the GCC Runtime Library Exception, version
   3.1, as published by the Free Software Foundation.

   You should have received a copy of the GNU General Public License and
   a copy of the GCC Runtime Library Exception along with this program;
   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
   <http://www.gnu.org/licenses/>.  */

#define R_LR		65
#define R_CR2		70
#define R_VR0		77
#define R_VRSAVE	109
#define R_VSCR		110

struct gcc_vregs
{
  __attribute__ ((vector_size (16))) int vr[32];
#ifdef __powerpc64__
  unsigned int pad1[3];
  unsigned int vscr;
  unsigned int vsave;
  unsigned int pad2[3];
#else
  unsigned int vsave;
  unsigned int pad[2];
  unsigned int vscr;
#endif
};

struct gcc_regs
{
  unsigned long gpr[32];
  unsigned long nip;
  unsigned long msr;
  unsigned long orig_gpr3;
  unsigned long ctr;
  unsigned long link;
  unsigned long xer;
  unsigned long ccr;
  unsigned long softe;
  unsigned long trap;
  unsigned long dar;
  unsigned long dsisr;
  unsigned long result;
  unsigned long pad1[4];
  double fpr[32];
  unsigned int pad2;
  unsigned int fpscr;
#ifdef __powerpc64__
  struct gcc_vregs *vp;
#else
  unsigned int pad3[2];
#endif
  struct gcc_vregs vregs;
};

struct gcc_ucontext
{
#ifdef __powerpc64__
  unsigned long pad[28];
#else
  unsigned long pad[12];
#endif
  struct gcc_regs *regs;
  struct gcc_regs rsave;
};

#ifdef __powerpc64__

enum { SIGNAL_FRAMESIZE = 128 };

/* If PC is at a sigreturn trampoline, return a pointer to the
   regs.  Otherwise return NULL.  */

static struct gcc_regs *
get_regs (struct _Unwind_Context *context)
{
  const unsigned int *pc = context->ra;

  /* addi r1, r1, 128; li r0, 0x0077; sc  (sigreturn) */
  /* addi r1, r1, 128; li r0, 0x00AC; sc  (rt_sigreturn) */
  if (pc[0] != 0x38210000 + SIGNAL_FRAMESIZE || pc[2] != 0x44000002)
    return NULL;
  if (pc[1] == 0x38000077)
    {
      struct sigframe {
	char gap[SIGNAL_FRAMESIZE];
	unsigned long pad[7];
	struct gcc_regs *regs;
      } *frame = (struct sigframe *) context->cfa;
      return frame->regs;
    }
  else if (pc[1] == 0x380000AC)
    {
      /* This works for 2.4 kernels, but not for 2.6 kernels with vdso
	 because pc isn't pointing into the stack.  Can be removed when
	 no one is running 2.4.19 or 2.4.20, the first two ppc64
	 kernels released.  */
      const struct rt_sigframe_24 {
	int tramp[6];
	void *pinfo;
	struct gcc_ucontext *puc;
      } *frame24 = (const struct rt_sigframe_24 *) context->ra;

      /* Test for magic value in *puc of vdso.  */
      if ((long) frame24->puc != -21 * 8)
	return frame24->puc->regs;
      else
	{
	  /* This works for 2.4.21 and later kernels.  */
	  struct rt_sigframe {
	    char gap[SIGNAL_FRAMESIZE];
	    struct gcc_ucontext uc;
	    unsigned long pad[2];
	    int tramp[6];
	    void *pinfo;
	    struct gcc_ucontext *puc;
	  } *frame = (struct rt_sigframe *) context->cfa;
	  return frame->uc.regs;
	}
    }
  return NULL;
}

#else  /* !__powerpc64__ */

enum { SIGNAL_FRAMESIZE = 64 };

static struct gcc_regs *
get_regs (struct _Unwind_Context *context)
{
  const unsigned int *pc = context->ra;

  /* li r0, 0x7777; sc  (sigreturn old)  */
  /* li r0, 0x0077; sc  (sigreturn new)  */
  /* li r0, 0x6666; sc  (rt_sigreturn old)  */
  /* li r0, 0x00AC; sc  (rt_sigreturn new)  */
  if (pc[1] != 0x44000002)
    return NULL;
  if (pc[0] == 0x38007777 || pc[0] == 0x38000077)
    {
      struct sigframe {
	char gap[SIGNAL_FRAMESIZE];
	unsigned long pad[7];
	struct gcc_regs *regs;
      } *frame = (struct sigframe *) context->cfa;
      return frame->regs;
    }
  else if (pc[0] == 0x38006666 || pc[0] == 0x380000AC)
    {
      struct rt_sigframe {
	char gap[SIGNAL_FRAMESIZE + 16];
	char siginfo[128];
	struct gcc_ucontext uc;
      } *frame = (struct rt_sigframe *) context->cfa;
      return frame->uc.regs;
    }
  return NULL;
}
#endif

/* Find an entry in the process auxiliary vector.  The canonical way to
   test for VMX is to look at AT_HWCAP.  */

static long
ppc_linux_aux_vector (long which)
{
  /* __libc_stack_end holds the original stack passed to a process.  */
  extern long *__libc_stack_end;
  long argc;
  char **argv;
  char **envp;
  struct auxv
  {
    long a_type;
    long a_val;
  } *auxp;

  /* The Linux kernel puts argc first on the stack.  */
  argc = __libc_stack_end[0];
  /* Followed by argv, NULL terminated.  */
  argv = (char **) __libc_stack_end + 1;
  /* Followed by environment string pointers, NULL terminated. */
  envp = argv + argc + 1;
  while (*envp++)
    continue;
  /* Followed by the aux vector, zero terminated.  */
  for (auxp = (struct auxv *) envp; auxp->a_type != 0; ++auxp)
    if (auxp->a_type == which)
      return auxp->a_val;
  return 0;
}

/* Do code reading to identify a signal frame, and set the frame
   state data appropriately.  See unwind-dw2.c for the structs.  */

#define MD_FALLBACK_FRAME_STATE_FOR ppc_fallback_frame_state

static _Unwind_Reason_Code
ppc_fallback_frame_state (struct _Unwind_Context *context,
			  _Unwind_FrameState *fs)
{
  static long hwcap = 0;
  struct gcc_regs *regs = get_regs (context);
  long new_cfa;
  int i;

  if (regs == NULL)
    return _URC_END_OF_STACK;

  new_cfa = regs->gpr[STACK_POINTER_REGNUM];
  fs->regs.cfa_how = CFA_REG_OFFSET;
  fs->regs.cfa_reg = STACK_POINTER_REGNUM;
  fs->regs.cfa_offset = new_cfa - (long) context->cfa;

  for (i = 0; i < 32; i++)
    if (i != STACK_POINTER_REGNUM)
      {
	fs->regs.reg[i].how = REG_SAVED_OFFSET;
	fs->regs.reg[i].loc.offset = (long) &regs->gpr[i] - new_cfa;
      }

  fs->regs.reg[R_CR2].how = REG_SAVED_OFFSET;
  /* CR? regs are always 32-bit and PPC is big-endian, so in 64-bit
     libgcc loc.offset needs to point to the low 32 bits of regs->ccr.  */
  fs->regs.reg[R_CR2].loc.offset = (long) &regs->ccr - new_cfa
				   + sizeof (long) - 4;

  fs->regs.reg[R_LR].how = REG_SAVED_OFFSET;
  fs->regs.reg[R_LR].loc.offset = (long) &regs->link - new_cfa;

  fs->regs.reg[ARG_POINTER_REGNUM].how = REG_SAVED_OFFSET;
  fs->regs.reg[ARG_POINTER_REGNUM].loc.offset = (long) &regs->nip - new_cfa;
  fs->retaddr_column = ARG_POINTER_REGNUM;
  fs->signal_frame = 1;

  if (hwcap == 0)
    {
      hwcap = ppc_linux_aux_vector (16);
      /* These will already be set if we found AT_HWCAP.  A nonzero
	 value stops us looking again if for some reason we couldn't
	 find AT_HWCAP.  */
#ifdef __powerpc64__
      hwcap |= 0xc0000000;
#else
      hwcap |= 0x80000000;
#endif
    }

  /* If we have a FPU...  */
  if (hwcap & 0x08000000)
    for (i = 0; i < 32; i++)
      {
	fs->regs.reg[i + 32].how = REG_SAVED_OFFSET;
	fs->regs.reg[i + 32].loc.offset = (long) &regs->fpr[i] - new_cfa;
      }

  /* If we have a VMX unit...  */
  if (hwcap & 0x10000000)
    {
      struct gcc_vregs *vregs;
#ifdef __powerpc64__
      vregs = regs->vp;
#else
      vregs = &regs->vregs;
#endif
      if (regs->msr & (1 << 25))
	{
	  for (i = 0; i < 32; i++)
	    {
	      fs->regs.reg[i + R_VR0].how = REG_SAVED_OFFSET;
	      fs->regs.reg[i + R_VR0].loc.offset
		= (long) &vregs->vr[i] - new_cfa;
	    }

	  fs->regs.reg[R_VSCR].how = REG_SAVED_OFFSET;
	  fs->regs.reg[R_VSCR].loc.offset = (long) &vregs->vscr - new_cfa;
	}

      fs->regs.reg[R_VRSAVE].how = REG_SAVED_OFFSET;
      fs->regs.reg[R_VRSAVE].loc.offset = (long) &vregs->vsave - new_cfa;
    }

  /* If we have SPE register high-parts... we check at compile-time to
     avoid expanding the code for all other PowerPC.  */
#ifdef __SPE__
  for (i = 0; i < 32; i++)
    {
      fs->regs.reg[i + FIRST_PSEUDO_REGISTER - 1].how = REG_SAVED_OFFSET;
      fs->regs.reg[i + FIRST_PSEUDO_REGISTER - 1].loc.offset
	= (long) &regs->vregs - new_cfa + 4 * i;
    }
#endif

  return _URC_NO_REASON;
}

#define MD_FROB_UPDATE_CONTEXT frob_update_context

static void
frob_update_context (struct _Unwind_Context *context, _Unwind_FrameState *fs ATTRIBUTE_UNUSED)
{
  const unsigned int *pc = (const unsigned int *) context->ra;

  /* Fix up for 2.6.12 - 2.6.16 Linux kernels that have vDSO, but don't
     have S flag in it.  */
#ifdef __powerpc64__
  /* addi r1, r1, 128; li r0, 0x0077; sc  (sigreturn) */
  /* addi r1, r1, 128; li r0, 0x00AC; sc  (rt_sigreturn) */
  if (pc[0] == 0x38210000 + SIGNAL_FRAMESIZE
      && (pc[1] == 0x38000077 || pc[1] == 0x380000AC)
      && pc[2] == 0x44000002)
    _Unwind_SetSignalFrame (context, 1);
#else
  /* li r0, 0x7777; sc  (sigreturn old)  */
  /* li r0, 0x0077; sc  (sigreturn new)  */
  /* li r0, 0x6666; sc  (rt_sigreturn old)  */
  /* li r0, 0x00AC; sc  (rt_sigreturn new)  */
  if ((pc[0] == 0x38007777 || pc[0] == 0x38000077
       || pc[0] == 0x38006666 || pc[0] == 0x380000AC)
      && pc[1] == 0x44000002)
    _Unwind_SetSignalFrame (context, 1);
#endif

#ifdef __powerpc64__
  if (fs->regs.reg[2].how == REG_UNSAVED)
    {
      /* If the current unwind info (FS) does not contain explicit info
	 saving R2, then we have to do a minor amount of code reading to
	 figure out if it was saved.  The big problem here is that the
	 code that does the save/restore is generated by the linker, so
	 we have no good way to determine at compile time what to do.  */
      if (pc[0] == 0xF8410028
	  || ((pc[0] & 0xFFFF0000) == 0x3D820000
	      && pc[1] == 0xF8410028))
	{
	  /* We are in a plt call stub or r2 adjusting long branch stub,
	     before r2 has been saved.  Keep REG_UNSAVED.  */
	}
      else if (pc[0] == 0x4E800421
	       && pc[1] == 0xE8410028)
	{
	  /* We are at the bctrl instruction in a call via function
	     pointer.  gcc always emits the load of the new r2 just
	     before the bctrl.  */
	  _Unwind_SetGRPtr (context, 2, context->cfa + 40);
	}
      else
	{
	  unsigned int *insn
	    = (unsigned int *) _Unwind_GetGR (context, R_LR);
	  if (insn && *insn == 0xE8410028)
	    _Unwind_SetGRPtr (context, 2, context->cfa + 40);
	}
    }
#endif
}