[ARC] Fix stack unwinding for ARC

[ARC] Fix stack unwinding for ARC

[Cupertino Miranda]

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Hi everyone,

Here is patch to stack unwinding for ARC.

- Fix to unwinding. Now is is possible to unwind from syscall
wrappers, signals and functions with dynamic stack allocation.

- Patch also fixes millicode. Although millicode save and restore functions
would change blink, the calls to those functions were not clobbering blink.

Looking forward to your reviews.

Best regards,
Cupertino


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From 213a0f115b2c7459b2a65728f4c5a74d2ed89c9d Mon Sep 17 00:00:00 2001
From: Cupertino Miranda <cmiranda@synopsys.com>
Date: Mon, 4 Sep 2017 14:24:51 +0200
Subject: [PATCH] Fix to unwinding. Now is is possible to unwind from syscall
 wrappers, signals and functions with dynamic stack allocation.

Patch also fixes millicode. Although millicode save and restore functions
would change blink, the calls to those functions were not clobbering blink.

gcc/ChangeLog:

2017-09-04  Cupertino Miranda  <cmiranda@synopsys.com>

	* config/arc/arc.c (arc_save_restore): Corrected CFA note.
	(arc_expand_prologue): Restore blink for millicode.
	* config/arc/linux.h (LINK_EH_SPEC): Defined.

libgcc/ChangeLog:

2017-09-04  Cupertino Miranda  <cmiranda@synopsys.com>

	* config/arc/linux-unwind-reg.def: Created with register indexes info.
	* config/arc/linux-unwind-reg.h (registers_stack_order): Defined.
	(register_position): Likewise.
	(register_id_for_index): Likewise.
	(arc_fallback_frame_state): New function to define frame where frame
	information is missing and it refers to a syscall wrapper.
	(+arc_frob_update_context): New function to correct context information in
	case unwinding happens through fp register.
---
 gcc/config/arc/arc.c                   |  36 ++++++--
 gcc/config/arc/linux.h                 |   8 ++
 libgcc/config.host                     |   1 +
 libgcc/config/arc/linux-unwind-reg.def |  23 +++++
 libgcc/config/arc/linux-unwind.h       | 154 +++++++++++++++++++++++++++++++++
 5 files changed, 216 insertions(+), 6 deletions(-)
 create mode 100644 libgcc/config/arc/linux-unwind-reg.def
 create mode 100644 libgcc/config/arc/linux-unwind.h

diff --git a/gcc/config/arc/arc.c b/gcc/config/arc/arc.c
index d519063..ff2f8ae 100644
--- a/gcc/config/arc/arc.c
+++ b/gcc/config/arc/arc.c
@@ -2849,12 +2849,23 @@ arc_save_restore (rtx base_reg,
 	  else
 	    {
 	      insn = frame_insn (insn);
-	      if (epilogue_p)
-		for (r = start_call; r <= end_call; r++)
-		  {
-		    rtx reg = gen_rtx_REG (SImode, r);
-		    add_reg_note (insn, REG_CFA_RESTORE, reg);
-		  }
+	      for (r = start_call, off = 0;
+		   r <= end_call;
+		   r++, off += UNITS_PER_WORD)
+		{
+		  rtx reg = gen_rtx_REG (SImode, r);
+		  if (epilogue_p)
+		      add_reg_note (insn, REG_CFA_RESTORE, reg);
+		  else
+		    {
+		      rtx mem = gen_rtx_MEM (SImode, plus_constant (Pmode,
+								    base_reg,
+								    off));
+
+		      add_reg_note (insn, REG_CFA_OFFSET,
+				    gen_rtx_SET (mem, reg));
+		    }
+		}
 	    }
 	  offset += off;
 	}
@@ -3092,6 +3103,19 @@ arc_expand_prologue (void)
       frame_size_to_allocate -= cfun->machine->frame_info.reg_size;
     }
 
+  /* In the case of millicode thunk, we need to restore the clobbered
+     blink register.  */
+  if (cfun->machine->frame_info.millicode_end_reg > 0
+      && arc_must_save_return_addr (cfun))
+    {
+      HOST_WIDE_INT tmp = cfun->machine->frame_info.reg_size;
+      emit_insn (gen_rtx_SET (gen_rtx_REG (Pmode, RETURN_ADDR_REGNUM),
+			      gen_rtx_MEM (Pmode,
+					   plus_constant (Pmode,
+							  stack_pointer_rtx,
+							  tmp))));
+    }
+
   /* Save frame pointer if needed.  First save the FP on stack, if not
      autosaved.  */
   if (arc_frame_pointer_needed ()
diff --git a/gcc/config/arc/linux.h b/gcc/config/arc/linux.h
index d8e0063..7073471 100644
--- a/gcc/config/arc/linux.h
+++ b/gcc/config/arc/linux.h
@@ -91,3 +91,11 @@ along with GCC; see the file COPYING3.  If not see
 /* Pre/post modify with register displacement are default off.  */
 #undef TARGET_AUTO_MODIFY_REG_DEFAULT
 #define TARGET_AUTO_MODIFY_REG_DEFAULT 0
+
+#if DEFAULT_LIBC == LIBC_GLIBC
+/* Override linux.h LINK_EH_SPEC definition.
+   Signalize that because we have fde-glibc, we don't need all C shared libs
+   linked against -lgcc_s.  */
+#undef LINK_EH_SPEC
+#define LINK_EH_SPEC "--eh-frame-hdr"
+#endif
diff --git a/libgcc/config.host b/libgcc/config.host
index 2686d59..d05ed45 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -385,6 +385,7 @@ arc*-*-elf*)
 	tmake_file="arc/t-arc"
 	extra_parts="crti.o crtn.o crtend.o crtbegin.o crtendS.o crtbeginS.o"
 	extra_parts="$extra_parts crttls.o"
+	md_unwind_header=arc/linux-unwind.h
 	;;
 arc*-*-linux*)
 	tmake_file="${tmake_file} t-slibgcc-libgcc t-slibgcc-nolc-override arc/t-arc-uClibc arc/t-arc"
diff --git a/libgcc/config/arc/linux-unwind-reg.def b/libgcc/config/arc/linux-unwind-reg.def
new file mode 100644
index 0000000..763a32f
--- /dev/null
+++ b/libgcc/config/arc/linux-unwind-reg.def
@@ -0,0 +1,23 @@
+REGISTER_IN_STACK(bta, -1)
+REGISTER_IN_STACK(lp_start, -1)
+REGISTER_IN_STACK(lp_end, -1)
+REGISTER_IN_STACK(lp_count, -1)
+REGISTER_IN_STACK(status32, -1)
+REGISTER_IN_STACK(ret, -1)
+REGISTER_IN_STACK(blink, 31)
+REGISTER_IN_STACK(fp, 27)
+REGISTER_IN_STACK(gp, 26)
+REGISTER_IN_STACK(r12, 12)
+REGISTER_IN_STACK(r11, 11)
+REGISTER_IN_STACK(r10, 10)
+REGISTER_IN_STACK(r9, 9)
+REGISTER_IN_STACK(r8, 8)
+REGISTER_IN_STACK(r7, 7)
+REGISTER_IN_STACK(r6, 6)
+REGISTER_IN_STACK(r5, 5)
+REGISTER_IN_STACK(r4, 4)
+REGISTER_IN_STACK(r3, 3)
+REGISTER_IN_STACK(r2, 2)
+REGISTER_IN_STACK(r1, 1)
+REGISTER_IN_STACK(r0, 0)
+REGISTER_IN_STACK(sp, 28)
diff --git a/libgcc/config/arc/linux-unwind.h b/libgcc/config/arc/linux-unwind.h
new file mode 100644
index 0000000..7b97149
--- /dev/null
+++ b/libgcc/config/arc/linux-unwind.h
@@ -0,0 +1,154 @@
+/* DWARF2 EH unwinding support for ARC Linux.
+   Copyright (C) 2004-2016 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/>.  */
+
+/* This order is defined by a structure in the kernel,
+   in file arch/arc/kernel/signal.c.  */
+
+#define REGISTER_IN_STACK(REG_NAME, ID) \
+  REG_NAME,
+enum registers_stack_order {
+  REGISTER_STACK_ORDER_START = -1,
+  #include "config/arc/linux-unwind-reg.def"
+  REGISTER_STACK_ORDER_SIZE,
+};
+
+struct register_position {
+  int reg_id;
+  int offset_in_stack;
+};
+#undef REGISTER_IN_STACK
+
+#define REGISTER_SIZE_IN_WORDS 4
+#define REGISTER_IN_STACK(REG_NAME, ID) (int) ID,
+int
+register_id_for_index[REGISTER_STACK_ORDER_SIZE] = {
+  #include "config/arc/linux-unwind-reg.def"
+};
+#undef REGISTER_IN_STACK
+
+#ifndef inhibit_libc
+/* Do code reading to identify a signal frame, and set the frame
+   state data appropriately.  See unwind-dw2.c for the structs.  */
+
+#include <signal.h>
+#include <asm/unistd.h>
+
+/*
+00010edc <__default_rt_sa_restorer>:
+   10edc:	208a 12c2		mov     r8,139
+   10ee0:	781e			trap_s  0
+   10ee2:	7ee0			j_s     [blink]
+*/
+
+#if __BIG_ENDIAN__
+#define MOV_R8_139	  0x8a20c212
+#define TRAP_S_J_S_BLINK  0x1e78e07e
+#define SWI		  0x6f223f00
+#elif __LITTLE_ENDIAN__
+#define MOV_R8_139	  0x12c2208a
+#define TRAP_S_J_S_BLINK  0x7ee0781e
+#define SWI		  0x003f226f
+#endif
+
+#define MD_FALLBACK_FRAME_STATE_FOR arc_fallback_frame_state
+
+static __attribute__((noinline)) _Unwind_Reason_Code
+arc_fallback_frame_state (struct _Unwind_Context *context,
+			   _Unwind_FrameState *fs)
+{
+  struct rt_sigframe {
+    siginfo_t info;
+    struct ucontext uc;
+    unsigned int sigret_magic;
+  };
+
+  struct rt_sigframe *rt_;
+  u_int32_t *pc = (u_int32_t *) context->ra;
+  struct sigcontext *sc;
+  _Unwind_Ptr new_cfa;
+  int i;
+
+#ifdef __ARC700__
+  if (pc[1] != SWI)
+    return _URC_END_OF_STACK;
+#else
+  if (pc[1] != TRAP_S_J_S_BLINK)
+    return _URC_END_OF_STACK;
+#endif
+
+  if (pc[0] == MOV_R8_139)
+    {
+      rt_ = context->cfa;
+      sc = &rt_->uc.uc_mcontext;
+    }
+  else
+    return _URC_END_OF_STACK;
+
+  new_cfa = (_Unwind_Ptr) sc;
+  fs->regs.cfa_how = CFA_REG_OFFSET;
+  fs->regs.cfa_reg = __LIBGCC_STACK_POINTER_REGNUM__;
+  fs->regs.cfa_offset = new_cfa - (_Unwind_Ptr) context->cfa;
+
+  unsigned long *regs = &sc->regs.scratch.bta;
+  for (i = 0; i < REGISTER_STACK_ORDER_SIZE; i++)
+    {
+      if (register_id_for_index[i] == -1)
+	continue;
+      fs->regs.reg[register_id_for_index[i]].how = REG_SAVED_OFFSET;
+      fs->regs.reg[register_id_for_index[i]].loc.offset
+	= ((_Unwind_Ptr) &(regs[i])) - new_cfa;
+    }
+
+  fs->regs.reg[31].how = REG_SAVED_VAL_OFFSET;
+  fs->regs.reg[31].loc.offset = ((_Unwind_Ptr) (regs[ret])) - new_cfa;
+
+  fs->retaddr_column = 31;
+
+  return _URC_NO_REASON;
+}
+#endif
+
+#define MD_FROB_UPDATE_CONTEXT arc_frob_update_context
+/* Save fp register for unwinding to work.  */
+
+static void
+arc_frob_update_context (struct _Unwind_Context *context,
+			 _Unwind_FrameState *fs)
+{
+    //register _Unwind_Word fp_val asm ("fp");
+    _Unwind_Word fp_val;
+    asm ("mov %0,fp" : "=r" (fp_val));
+
+    switch (fs->regs.reg[27].how)
+      {
+      case REG_UNSAVED:
+      case REG_UNDEFINED:
+	if (context->reg[27] == NULL)
+	  _Unwind_SetGRValue (context, 27, fp_val);
+	break;
+
+      default:
+	break;
+      }
+}
-- 
2.9.0

RE: [ARC] Fix stack unwinding for ARC

[Claudiu Zissulescu]

> - Fix to unwinding. Now is is possible to unwind from syscall
> wrappers, signals and functions with dynamic stack allocation.
> 
> - Patch also fixes millicode. Although millicode save and restore functions
> would change blink, the calls to those functions were not clobbering blink.
> 

Approved and committed with minor modifications.

Cheers,
Claudiu