libgcc/config/rs6000/linux-unwind.h

   1 /* DWARF2 EH unwinding support for PowerPC and PowerPC64 Linux.
   2    Copyright (C) 2004-2022 Free Software Foundation, Inc.
   3
   4    This file is part of GCC.
   5
   6    GCC is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published
   8    by the Free Software Foundation; either version 3, or (at your
   9    option) any later version.
  10
  11    GCC is distributed in the hope that it will be useful, but WITHOUT
  12    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  13    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
  14    License for more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 #define R_LR            65
  26 #define R_CR2           70
  27 #define R_CR3           71
  28 #define R_CR4           72
  29 #define R_VR0           77
  30 #define R_VRSAVE        109
  31
  32 #ifdef __powerpc64__
  33 #if _CALL_ELF == 2
  34 #define TOC_SAVE_SLOT   24
  35 #else
  36 #define TOC_SAVE_SLOT   40
  37 #endif
  38 #endif
  39
  40 struct gcc_vregs
  41 {
  42   __attribute__ ((vector_size (16))) int vr[32];
  43 #ifdef __powerpc64__
  44   unsigned int pad1[3];
  45   unsigned int vscr;
  46   unsigned int vsave;
  47   unsigned int pad2[3];
  48 #else
  49   unsigned int vsave;
  50   unsigned int pad[2];
  51   unsigned int vscr;
  52 #endif
  53 };
  54
  55 struct gcc_regs
  56 {
  57   unsigned long gpr[32];
  58   unsigned long nip;
  59   unsigned long msr;
  60   unsigned long orig_gpr3;
  61   unsigned long ctr;
  62   unsigned long link;
  63   unsigned long xer;
  64   unsigned long ccr;
  65   unsigned long softe;
  66   unsigned long trap;
  67   unsigned long dar;
  68   unsigned long dsisr;
  69   unsigned long result;
  70   unsigned long pad1[4];
  71   double fpr[32];
  72   unsigned int pad2;
  73   unsigned int fpscr;
  74 #ifdef __powerpc64__
  75   struct gcc_vregs *vp;
  76 #else
  77   unsigned int pad3[2];
  78 #endif
  79   struct gcc_vregs vregs;
  80 };
  81
  82 struct gcc_ucontext
  83 {
  84 #ifdef __powerpc64__
  85   unsigned long pad[28];
  86 #else
  87   unsigned long pad[12];
  88 #endif
  89   struct gcc_regs *regs;
  90   struct gcc_regs rsave;
  91 };
  92
  93 #ifdef __powerpc64__
  94
  95 enum { SIGNAL_FRAMESIZE = 128 };
  96
  97 struct rt_sigframe {
  98   char gap[SIGNAL_FRAMESIZE];
  99   struct gcc_ucontext uc;
 100   unsigned long pad[2];
 101   int tramp[6];
 102   void *pinfo;
 103   struct gcc_ucontext *puc;
 104 };
 105
 106 /* If PC is at a sigreturn trampoline, return a pointer to the
 107    regs.  Otherwise return NULL.  */
 108
 109 static struct gcc_regs *
 110 get_regs (struct _Unwind_Context *context)
 111 {
 112   const unsigned int *pc = context->ra;
 113
 114   /* addi r1, r1, 128; li r0, 0x0077; sc  (sigreturn) */
 115   /* addi r1, r1, 128; li r0, 0x00AC; sc  (rt_sigreturn) */
 116   if (pc[0] != 0x38210000 + SIGNAL_FRAMESIZE || pc[2] != 0x44000002)
 117     return NULL;
 118   if (pc[1] == 0x38000077)
 119     {
 120       struct sigframe {
 121         char gap[SIGNAL_FRAMESIZE];
 122         unsigned long pad[7];
 123         struct gcc_regs *regs;
 124       } *frame = (struct sigframe *) context->cfa;
 125       return frame->regs;
 126     }
 127   else if (pc[1] == 0x380000AC)
 128     {
 129 #if _CALL_ELF != 2
 130       /* These old kernel versions never supported ELFv2.  */
 131       /* This works for 2.4 kernels, but not for 2.6 kernels with vdso
 132          because pc isn't pointing into the stack.  Can be removed when
 133          no one is running 2.4.19 or 2.4.20, the first two ppc64
 134          kernels released.  */
 135       const struct rt_sigframe_24 {
 136         int tramp[6];
 137         void *pinfo;
 138         struct gcc_ucontext *puc;
 139       } *frame24 = (const struct rt_sigframe_24 *) context->ra;
 140
 141       /* Test for magic value in *puc of vdso.  */
 142       if ((long) frame24->puc != -21 * 8)
 143         return frame24->puc->regs;
 144       else
 145 #endif
 146         {
 147           /* This works for 2.4.21 and later kernels.  */
 148           struct rt_sigframe *frame = (struct rt_sigframe *) context->cfa;
 149           return frame->uc.regs;
 150         }
 151     }
 152   return NULL;
 153 }
 154
 155 #else  /* !__powerpc64__ */
 156
 157 enum { SIGNAL_FRAMESIZE = 64 };
 158
 159 struct rt_sigframe {
 160   char gap[SIGNAL_FRAMESIZE + 16];
 161   char siginfo[128];
 162   struct gcc_ucontext uc;
 163 };
 164
 165 static struct gcc_regs *
 166 get_regs (struct _Unwind_Context *context)
 167 {
 168   const unsigned int *pc = context->ra;
 169
 170   /* li r0, 0x7777; sc  (sigreturn old)  */
 171   /* li r0, 0x0077; sc  (sigreturn new)  */
 172   /* li r0, 0x6666; sc  (rt_sigreturn old)  */
 173   /* li r0, 0x00AC; sc  (rt_sigreturn new)  */
 174   if (pc[1] != 0x44000002)
 175     return NULL;
 176   if (pc[0] == 0x38007777 || pc[0] == 0x38000077)
 177     {
 178       struct sigframe {
 179         char gap[SIGNAL_FRAMESIZE];
 180         unsigned long pad[7];
 181         struct gcc_regs *regs;
 182       } *frame = (struct sigframe *) context->cfa;
 183       return frame->regs;
 184     }
 185   else if (pc[0] == 0x38006666 || pc[0] == 0x380000AC)
 186     {
 187       struct rt_sigframe *frame = (struct rt_sigframe *) context->cfa;
 188       return frame->uc.regs;
 189     }
 190   return NULL;
 191 }
 192 #endif
 193
 194 /* Do code reading to identify a signal frame, and set the frame
 195    state data appropriately.  See unwind-dw2.c for the structs.  */
 196
 197 #define MD_FALLBACK_FRAME_STATE_FOR ppc_fallback_frame_state
 198
 199 static _Unwind_Reason_Code
 200 ppc_fallback_frame_state (struct _Unwind_Context *context,
 201                           _Unwind_FrameState *fs)
 202 {
 203   struct gcc_regs *regs = get_regs (context);
 204   struct gcc_vregs *vregs;
 205   long cr_offset;
 206   long new_cfa;
 207   int i;
 208
 209   if (regs == NULL)
 210     return _URC_NORMAL_STOP;
 211
 212   new_cfa = regs->gpr[__LIBGCC_STACK_POINTER_REGNUM__];
 213   fs->regs.cfa_how = CFA_REG_OFFSET;
 214   fs->regs.cfa_reg = __LIBGCC_STACK_POINTER_REGNUM__;
 215   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 216
 217 #ifdef __powerpc64__
 218   fs->regs.reg[2].how = REG_SAVED_OFFSET;
 219   fs->regs.reg[2].loc.offset = (long) &regs->gpr[2] - new_cfa;
 220 #endif
 221   for (i = 14; i < 32; i++)
 222     {
 223       fs->regs.reg[i].how = REG_SAVED_OFFSET;
 224       fs->regs.reg[i].loc.offset = (long) &regs->gpr[i] - new_cfa;
 225     }
 226
 227   /* The CR is saved in the low 32 bits of regs->ccr.  */
 228   cr_offset = (long) &regs->ccr - new_cfa;
 229 #ifndef __LITTLE_ENDIAN__
 230   cr_offset += sizeof (long) - 4;
 231 #endif
 232   /* In the ELFv1 ABI, CR2 stands in for the whole CR.  */
 233   fs->regs.reg[R_CR2].how = REG_SAVED_OFFSET;
 234   fs->regs.reg[R_CR2].loc.offset = cr_offset;
 235 #if _CALL_ELF == 2
 236   /* In the ELFv2 ABI, every CR field has a separate CFI entry.  */
 237   fs->regs.reg[R_CR3].how = REG_SAVED_OFFSET;
 238   fs->regs.reg[R_CR3].loc.offset = cr_offset;
 239   fs->regs.reg[R_CR4].how = REG_SAVED_OFFSET;
 240   fs->regs.reg[R_CR4].loc.offset = cr_offset;
 241 #endif
 242
 243   fs->regs.reg[R_LR].how = REG_SAVED_OFFSET;
 244   fs->regs.reg[R_LR].loc.offset = (long) &regs->link - new_cfa;
 245
 246   fs->regs.reg[ARG_POINTER_REGNUM].how = REG_SAVED_OFFSET;
 247   fs->regs.reg[ARG_POINTER_REGNUM].loc.offset = (long) &regs->nip - new_cfa;
 248   fs->retaddr_column = ARG_POINTER_REGNUM;
 249   fs->signal_frame = 1;
 250
 251   /* If we have a FPU...  */
 252   for (i = 14; i < 32; i++)
 253     {
 254       fs->regs.reg[i + 32].how = REG_SAVED_OFFSET;
 255       fs->regs.reg[i + 32].loc.offset = (long) &regs->fpr[i] - new_cfa;
 256     }
 257
 258   /* If we have a VMX unit...  */
 259 #ifdef __powerpc64__
 260   vregs = regs->vp;
 261 #else
 262   vregs = &regs->vregs;
 263 #endif
 264   if (regs->msr & (1 << 25))
 265     {
 266       for (i = 20; i < 32; i++)
 267         {
 268           fs->regs.reg[i + R_VR0].how = REG_SAVED_OFFSET;
 269           fs->regs.reg[i + R_VR0].loc.offset = (long) &vregs->vr[i] - new_cfa;
 270         }
 271     }
 272
 273   fs->regs.reg[R_VRSAVE].how = REG_SAVED_OFFSET;
 274   fs->regs.reg[R_VRSAVE].loc.offset = (long) &vregs->vsave - new_cfa;
 275
 276   /* If we have SPE register high-parts... we check at compile-time to
 277      avoid expanding the code for all other PowerPC.  */
 278 #ifdef __SPE__
 279   for (i = 14; i < 32; i++)
 280     {
 281       fs->regs.reg[i + FIRST_SPE_HIGH_REGNO - 4].how = REG_SAVED_OFFSET;
 282       fs->regs.reg[i + FIRST_SPE_HIGH_REGNO - 4].loc.offset
 283         = (long) &regs->vregs - new_cfa + 4 * i;
 284     }
 285 #endif
 286
 287   return _URC_NO_REASON;
 288 }
 289
 290 #define MD_FROB_UPDATE_CONTEXT frob_update_context
 291
 292 static void
 293 frob_update_context (struct _Unwind_Context *context, _Unwind_FrameState *fs ATTRIBUTE_UNUSED)
 294 {
 295   const unsigned int *pc = (const unsigned int *) context->ra;
 296
 297   /* Fix up for 2.6.12 - 2.6.16 Linux kernels that have vDSO, but don't
 298      have S flag in it.  */
 299 #ifdef __powerpc64__
 300   /* addi r1, r1, 128; li r0, 0x0077; sc  (sigreturn) */
 301   /* addi r1, r1, 128; li r0, 0x00AC; sc  (rt_sigreturn) */
 302   if (pc[0] == 0x38210000 + SIGNAL_FRAMESIZE
 303       && (pc[1] == 0x38000077 || pc[1] == 0x380000AC)
 304       && pc[2] == 0x44000002)
 305     _Unwind_SetSignalFrame (context, 1);
 306 #else
 307   /* li r0, 0x7777; sc  (sigreturn old)  */
 308   /* li r0, 0x0077; sc  (sigreturn new)  */
 309   /* li r0, 0x6666; sc  (rt_sigreturn old)  */
 310   /* li r0, 0x00AC; sc  (rt_sigreturn new)  */
 311   if ((pc[0] == 0x38007777 || pc[0] == 0x38000077
 312        || pc[0] == 0x38006666 || pc[0] == 0x380000AC)
 313       && pc[1] == 0x44000002)
 314     _Unwind_SetSignalFrame (context, 1);
 315 #endif
 316
 317 #ifdef __powerpc64__
 318   if (fs->regs.reg[2].how == REG_UNSAVED)
 319     {
 320       /* If the current unwind info (FS) does not contain explicit info
 321          saving R2, then we have to do a minor amount of code reading to
 322          figure out if it was saved.  The big problem here is that the
 323          code that does the save/restore is generated by the linker, so
 324          we have no good way to determine at compile time what to do.  */
 325       if (pc[0] == 0xF8410000 + TOC_SAVE_SLOT
 326 #if _CALL_ELF != 2
 327           /* The ELFv2 linker never generates the old PLT stub form.  */
 328           || ((pc[0] & 0xFFFF0000) == 0x3D820000
 329               && pc[1] == 0xF8410000 + TOC_SAVE_SLOT)
 330 #endif
 331           )
 332         {
 333           /* We are in a plt call stub or r2 adjusting long branch stub,
 334              before r2 has been saved.  Keep REG_UNSAVED.  */
 335         }
 336       else
 337         {
 338           unsigned int *insn
 339             = (unsigned int *) _Unwind_GetGR (context, R_LR);
 340           if (insn && *insn == 0xE8410000 + TOC_SAVE_SLOT)
 341             _Unwind_SetGRPtr (context, 2, context->cfa + TOC_SAVE_SLOT);
 342 #if _CALL_ELF != 2
 343           /* ELFv2 does not use this function pointer call sequence.  */
 344           else if (pc[0] == 0x4E800421
 345                    && pc[1] == 0xE8410000 + TOC_SAVE_SLOT)
 346             {
 347               /* We are at the bctrl instruction in a call via function
 348                  pointer.  gcc always emits the load of the new R2 just
 349                  before the bctrl so this is the first and only place
 350                  we need to use the stored R2.  */
 351               _Unwind_Word sp = _Unwind_GetGR (context, 1);
 352               _Unwind_SetGRPtr (context, 2, (void *)(sp + TOC_SAVE_SLOT));
 353             }
 354 #endif
 355         }
 356     }
 357 #endif
 358 }
 359
 360 #define MD_BACKCHAIN_FALLBACK ppc_backchain_fallback
 361
 362 struct trace_arg
 363 {
 364   /* Stores the list of addresses.  */
 365   void **array;
 366   struct unwind_link *unwind_link;
 367   _Unwind_Word cfa;
 368   /* Number of addresses currently stored.  */
 369   int count;
 370   /* Maximum number of addresses.  */
 371   int size;
 372 };
 373
 374 /* This is the stack layout we see with every stack frame.
 375    Note that every routine is required by the ABI to lay out the stack
 376    like this.
 377
 378             +----------------+        +-----------------+
 379     %r1  -> | previous frame--------> | previous frame--->...  --> NULL
 380             |                |        |                 |
 381             | cr save        |        | cr save         |
 382             |                |        |                 |
 383             | (unused)       |        | lr save         |
 384             +----------------+        +-----------------+
 385
 386   The CR save is only present on 64-bit ABIs.
 387 */
 388 struct frame_layout
 389 {
 390   struct frame_layout *backchain;
 391 #ifdef __powerpc64__
 392   long int cr_save;
 393 #endif
 394   void *lr_save;
 395 };
 396
 397
 398 static void
 399 ppc_backchain_fallback (struct _Unwind_Context *context, void *a)
 400 {
 401   struct frame_layout *current;
 402   struct trace_arg *arg = a;
 403   int count;
 404
 405   /* Get the last address computed.  */
 406   current = context->cfa;
 407
 408   /* If the trace CFA is not the context CFA the backtrace is done.  */
 409   if (arg == NULL || arg->cfa != current)
 410         return;
 411
 412   /* Start with next address.  */
 413   current = current->backchain;
 414
 415   for (count = arg->count; current != NULL; current = current->backchain)
 416     {
 417       arg->array[count] = current->lr_save;
 418
 419       /* Check if the symbol is the signal trampoline and get the interrupted
 420          symbol address from the trampoline saved area.  */
 421       context->ra = current->lr_save;
 422       if (current->lr_save && get_regs (context))
 423         {
 424           struct rt_sigframe *sigframe = (struct rt_sigframe *) current;
 425           if (count + 1 == arg->size)
 426             break;
 427           arg->array[++count] = (void *) sigframe->uc.rsave.nip;
 428           current = (void *) sigframe->uc.rsave.gpr[1];
 429         }
 430       if (count++ >= arg->size)
 431         break;
 432     }
 433
 434   arg->count = count-1;
 435 }