1 /* DWARF2 EH unwinding support for PowerPC and PowerPC64 Linux.
2    Copyright (C) 2004-2020 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 /* If PC is at a sigreturn trampoline, return a pointer to the
98    regs.  Otherwise return NULL.  */
99 
100 static struct gcc_regs *
get_regs(struct _Unwind_Context * context)101 get_regs (struct _Unwind_Context *context)
102 {
103   const unsigned int *pc = context->ra;
104 
105   /* addi r1, r1, 128; li r0, 0x0077; sc  (sigreturn) */
106   /* addi r1, r1, 128; li r0, 0x00AC; sc  (rt_sigreturn) */
107   if (pc[0] != 0x38210000 + SIGNAL_FRAMESIZE || pc[2] != 0x44000002)
108     return NULL;
109   if (pc[1] == 0x38000077)
110     {
111       struct sigframe {
112 	char gap[SIGNAL_FRAMESIZE];
113 	unsigned long pad[7];
114 	struct gcc_regs *regs;
115       } *frame = (struct sigframe *) context->cfa;
116       return frame->regs;
117     }
118   else if (pc[1] == 0x380000AC)
119     {
120 #if _CALL_ELF != 2
121       /* These old kernel versions never supported ELFv2.  */
122       /* This works for 2.4 kernels, but not for 2.6 kernels with vdso
123 	 because pc isn't pointing into the stack.  Can be removed when
124 	 no one is running 2.4.19 or 2.4.20, the first two ppc64
125 	 kernels released.  */
126       const struct rt_sigframe_24 {
127 	int tramp[6];
128 	void *pinfo;
129 	struct gcc_ucontext *puc;
130       } *frame24 = (const struct rt_sigframe_24 *) context->ra;
131 
132       /* Test for magic value in *puc of vdso.  */
133       if ((long) frame24->puc != -21 * 8)
134 	return frame24->puc->regs;
135       else
136 #endif
137 	{
138 	  /* This works for 2.4.21 and later kernels.  */
139 	  struct rt_sigframe {
140 	    char gap[SIGNAL_FRAMESIZE];
141 	    struct gcc_ucontext uc;
142 	    unsigned long pad[2];
143 	    int tramp[6];
144 	    void *pinfo;
145 	    struct gcc_ucontext *puc;
146 	  } *frame = (struct rt_sigframe *) context->cfa;
147 	  return frame->uc.regs;
148 	}
149     }
150   return NULL;
151 }
152 
153 #else  /* !__powerpc64__ */
154 
155 enum { SIGNAL_FRAMESIZE = 64 };
156 
157 static struct gcc_regs *
get_regs(struct _Unwind_Context * context)158 get_regs (struct _Unwind_Context *context)
159 {
160   const unsigned int *pc = context->ra;
161 
162   /* li r0, 0x7777; sc  (sigreturn old)  */
163   /* li r0, 0x0077; sc  (sigreturn new)  */
164   /* li r0, 0x6666; sc  (rt_sigreturn old)  */
165   /* li r0, 0x00AC; sc  (rt_sigreturn new)  */
166   if (pc[1] != 0x44000002)
167     return NULL;
168   if (pc[0] == 0x38007777 || pc[0] == 0x38000077)
169     {
170       struct sigframe {
171 	char gap[SIGNAL_FRAMESIZE];
172 	unsigned long pad[7];
173 	struct gcc_regs *regs;
174       } *frame = (struct sigframe *) context->cfa;
175       return frame->regs;
176     }
177   else if (pc[0] == 0x38006666 || pc[0] == 0x380000AC)
178     {
179       struct rt_sigframe {
180 	char gap[SIGNAL_FRAMESIZE + 16];
181 	char siginfo[128];
182 	struct gcc_ucontext uc;
183       } *frame = (struct rt_sigframe *) context->cfa;
184       return frame->uc.regs;
185     }
186   return NULL;
187 }
188 #endif
189 
190 /* Do code reading to identify a signal frame, and set the frame
191    state data appropriately.  See unwind-dw2.c for the structs.  */
192 
193 #define MD_FALLBACK_FRAME_STATE_FOR ppc_fallback_frame_state
194 
195 static _Unwind_Reason_Code
ppc_fallback_frame_state(struct _Unwind_Context * context,_Unwind_FrameState * fs)196 ppc_fallback_frame_state (struct _Unwind_Context *context,
197 			  _Unwind_FrameState *fs)
198 {
199   struct gcc_regs *regs = get_regs (context);
200   struct gcc_vregs *vregs;
201   long cr_offset;
202   long new_cfa;
203   int i;
204 
205   if (regs == NULL)
206     return _URC_END_OF_STACK;
207 
208   new_cfa = regs->gpr[__LIBGCC_STACK_POINTER_REGNUM__];
209   fs->regs.cfa_how = CFA_REG_OFFSET;
210   fs->regs.cfa_reg = __LIBGCC_STACK_POINTER_REGNUM__;
211   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
212 
213 #ifdef __powerpc64__
214   fs->regs.reg[2].how = REG_SAVED_OFFSET;
215   fs->regs.reg[2].loc.offset = (long) &regs->gpr[2] - new_cfa;
216 #endif
217   for (i = 14; i < 32; i++)
218     {
219       fs->regs.reg[i].how = REG_SAVED_OFFSET;
220       fs->regs.reg[i].loc.offset = (long) &regs->gpr[i] - new_cfa;
221     }
222 
223   /* The CR is saved in the low 32 bits of regs->ccr.  */
224   cr_offset = (long) &regs->ccr - new_cfa;
225 #ifndef __LITTLE_ENDIAN__
226   cr_offset += sizeof (long) - 4;
227 #endif
228   /* In the ELFv1 ABI, CR2 stands in for the whole CR.  */
229   fs->regs.reg[R_CR2].how = REG_SAVED_OFFSET;
230   fs->regs.reg[R_CR2].loc.offset = cr_offset;
231 #if _CALL_ELF == 2
232   /* In the ELFv2 ABI, every CR field has a separate CFI entry.  */
233   fs->regs.reg[R_CR3].how = REG_SAVED_OFFSET;
234   fs->regs.reg[R_CR3].loc.offset = cr_offset;
235   fs->regs.reg[R_CR4].how = REG_SAVED_OFFSET;
236   fs->regs.reg[R_CR4].loc.offset = cr_offset;
237 #endif
238 
239   fs->regs.reg[R_LR].how = REG_SAVED_OFFSET;
240   fs->regs.reg[R_LR].loc.offset = (long) &regs->link - new_cfa;
241 
242   fs->regs.reg[ARG_POINTER_REGNUM].how = REG_SAVED_OFFSET;
243   fs->regs.reg[ARG_POINTER_REGNUM].loc.offset = (long) &regs->nip - new_cfa;
244   fs->retaddr_column = ARG_POINTER_REGNUM;
245   fs->signal_frame = 1;
246 
247   /* If we have a FPU...  */
248   for (i = 14; i < 32; i++)
249     {
250       fs->regs.reg[i + 32].how = REG_SAVED_OFFSET;
251       fs->regs.reg[i + 32].loc.offset = (long) &regs->fpr[i] - new_cfa;
252     }
253 
254   /* If we have a VMX unit...  */
255 #ifdef __powerpc64__
256   vregs = regs->vp;
257 #else
258   vregs = &regs->vregs;
259 #endif
260   if (regs->msr & (1 << 25))
261     {
262       for (i = 20; i < 32; i++)
263 	{
264 	  fs->regs.reg[i + R_VR0].how = REG_SAVED_OFFSET;
265 	  fs->regs.reg[i + R_VR0].loc.offset = (long) &vregs->vr[i] - new_cfa;
266 	}
267     }
268 
269   fs->regs.reg[R_VRSAVE].how = REG_SAVED_OFFSET;
270   fs->regs.reg[R_VRSAVE].loc.offset = (long) &vregs->vsave - new_cfa;
271 
272   /* If we have SPE register high-parts... we check at compile-time to
273      avoid expanding the code for all other PowerPC.  */
274 #ifdef __SPE__
275   for (i = 14; i < 32; i++)
276     {
277       fs->regs.reg[i + FIRST_SPE_HIGH_REGNO - 4].how = REG_SAVED_OFFSET;
278       fs->regs.reg[i + FIRST_SPE_HIGH_REGNO - 4].loc.offset
279 	= (long) &regs->vregs - new_cfa + 4 * i;
280     }
281 #endif
282 
283   return _URC_NO_REASON;
284 }
285 
286 #define MD_FROB_UPDATE_CONTEXT frob_update_context
287 
288 static void
frob_update_context(struct _Unwind_Context * context,_Unwind_FrameState * fs ATTRIBUTE_UNUSED)289 frob_update_context (struct _Unwind_Context *context, _Unwind_FrameState *fs ATTRIBUTE_UNUSED)
290 {
291   const unsigned int *pc = (const unsigned int *) context->ra;
292 
293   /* Fix up for 2.6.12 - 2.6.16 Linux kernels that have vDSO, but don't
294      have S flag in it.  */
295 #ifdef __powerpc64__
296   /* addi r1, r1, 128; li r0, 0x0077; sc  (sigreturn) */
297   /* addi r1, r1, 128; li r0, 0x00AC; sc  (rt_sigreturn) */
298   if (pc[0] == 0x38210000 + SIGNAL_FRAMESIZE
299       && (pc[1] == 0x38000077 || pc[1] == 0x380000AC)
300       && pc[2] == 0x44000002)
301     _Unwind_SetSignalFrame (context, 1);
302 #else
303   /* li r0, 0x7777; sc  (sigreturn old)  */
304   /* li r0, 0x0077; sc  (sigreturn new)  */
305   /* li r0, 0x6666; sc  (rt_sigreturn old)  */
306   /* li r0, 0x00AC; sc  (rt_sigreturn new)  */
307   if ((pc[0] == 0x38007777 || pc[0] == 0x38000077
308        || pc[0] == 0x38006666 || pc[0] == 0x380000AC)
309       && pc[1] == 0x44000002)
310     _Unwind_SetSignalFrame (context, 1);
311 #endif
312 
313 #ifdef __powerpc64__
314   if (fs->regs.reg[2].how == REG_UNSAVED)
315     {
316       /* If the current unwind info (FS) does not contain explicit info
317 	 saving R2, then we have to do a minor amount of code reading to
318 	 figure out if it was saved.  The big problem here is that the
319 	 code that does the save/restore is generated by the linker, so
320 	 we have no good way to determine at compile time what to do.  */
321       if (pc[0] == 0xF8410000 + TOC_SAVE_SLOT
322 #if _CALL_ELF != 2
323 	  /* The ELFv2 linker never generates the old PLT stub form.  */
324 	  || ((pc[0] & 0xFFFF0000) == 0x3D820000
325 	      && pc[1] == 0xF8410000 + TOC_SAVE_SLOT)
326 #endif
327 	  )
328 	{
329 	  /* We are in a plt call stub or r2 adjusting long branch stub,
330 	     before r2 has been saved.  Keep REG_UNSAVED.  */
331 	}
332       else
333 	{
334 	  unsigned int *insn
335 	    = (unsigned int *) _Unwind_GetGR (context, R_LR);
336 	  if (insn && *insn == 0xE8410000 + TOC_SAVE_SLOT)
337 	    _Unwind_SetGRPtr (context, 2, context->cfa + TOC_SAVE_SLOT);
338 #if _CALL_ELF != 2
339 	  /* ELFv2 does not use this function pointer call sequence.  */
340 	  else if (pc[0] == 0x4E800421
341 		   && pc[1] == 0xE8410000 + TOC_SAVE_SLOT)
342 	    {
343 	      /* We are at the bctrl instruction in a call via function
344 		 pointer.  gcc always emits the load of the new R2 just
345 		 before the bctrl so this is the first and only place
346 		 we need to use the stored R2.  */
347 	      _Unwind_Word sp = _Unwind_GetGR (context, 1);
348 	      _Unwind_SetGRPtr (context, 2, (void *)(sp + TOC_SAVE_SLOT));
349 	    }
350 #endif
351 	}
352     }
353 #endif
354 }
355