diff --git a/configure.in b/configure.in
index 100df65d..f09a3230 100644
--- a/configure.in
+++ b/configure.in
@@ -169,6 +169,12 @@ if test x$enable_block_signals = xyes; then
   AC_DEFINE([CONFIG_BLOCK_SIGNALS], [], [Block signals before mutex operations])
 fi
 
+AC_ARG_ENABLE(conservative_checks,
+[ --enable-conservative-checks Validate all memory addresses before use],
+[enable_conservative_checks=$enableval], [enable_conservative_checks=yes])
+if test x$enable_conservative_checks = xyes; then
+  CPPFLAGS="${CPPFLAGS} -DCONSERVATIVE_CHECKS"
+fi
 
 LIBUNWIND___THREAD
 
diff --git a/include/dwarf.h b/include/dwarf.h
index 37b5ec1c..5dcc6ec9 100644
--- a/include/dwarf.h
+++ b/include/dwarf.h
@@ -247,6 +247,7 @@ typedef struct dwarf_reg_state
     unsigned short lru_chain;	  /* used for least-recently-used chain */
     unsigned short coll_chain;	/* used for hash collisions */
     unsigned short hint;	      /* hint for next rs to try (or -1) */
+    unsigned short signal_frame; /* optional machine-dependent signal info */
   }
 dwarf_reg_state_t;
 
@@ -266,6 +267,7 @@ typedef struct dwarf_cie_info
     uint8_t lsda_encoding;
     unsigned int sized_augmentation : 1;
     unsigned int have_abi_marker : 1;
+    unsigned int signal_frame : 1;
   }
 dwarf_cie_info_t;
 
@@ -293,6 +295,7 @@ typedef struct dwarf_cursor
 
     dwarf_loc_t loc[DWARF_NUM_PRESERVED_REGS];
 
+    unsigned int use_prev_instr :1; /* use previous (= call) or current (= signal) instruction? */
     unsigned int pi_valid :1;	/* is proc_info valid? */
     unsigned int pi_is_dynamic :1; /* proc_info found via dynamic proc info? */
     unw_proc_info_t pi;		/* info about current procedure */
diff --git a/include/tdep-arm/libunwind_i.h b/include/tdep-arm/libunwind_i.h
index 3424d86a..2e1c4285 100644
--- a/include/tdep-arm/libunwind_i.h
+++ b/include/tdep-arm/libunwind_i.h
@@ -217,6 +217,9 @@ dwarf_put (struct dwarf_cursor *c, dwarf_loc_t loc, unw_word_t val)
 #define tdep_get_elf_image		UNW_ARCH_OBJ(get_elf_image)
 #define tdep_access_reg			UNW_OBJ(access_reg)
 #define tdep_access_fpreg		UNW_OBJ(access_fpreg)
+#define tdep_fetch_frame(c,ip,n)	do {} while(0)
+#define tdep_cache_frame(c,rs)		do {} while(0)
+#define tdep_reuse_frame(c,rs)		do {} while(0)
 
 #ifdef UNW_LOCAL_ONLY
 # define tdep_find_proc_info(c,ip,n)				\
diff --git a/include/tdep-hppa/libunwind_i.h b/include/tdep-hppa/libunwind_i.h
index 553e97d8..d89cc65e 100644
--- a/include/tdep-hppa/libunwind_i.h
+++ b/include/tdep-hppa/libunwind_i.h
@@ -224,6 +224,9 @@ dwarf_put (struct dwarf_cursor *c, dwarf_loc_t loc, unw_word_t val)
 #define tdep_get_elf_image		UNW_ARCH_OBJ(get_elf_image)
 #define tdep_access_reg			UNW_OBJ(access_reg)
 #define tdep_access_fpreg		UNW_OBJ(access_fpreg)
+#define tdep_fetch_frame(c,ip,n)	do {} while(0)
+#define tdep_cache_frame(c,rs)		do {} while(0)
+#define tdep_reuse_frame(c,rs)		do {} while(0)
 
 #ifdef UNW_LOCAL_ONLY
 # define tdep_find_proc_info(c,ip,n)				\
diff --git a/include/tdep-ia64/libunwind_i.h b/include/tdep-ia64/libunwind_i.h
index 552c9498..4936d516 100644
--- a/include/tdep-ia64/libunwind_i.h
+++ b/include/tdep-ia64/libunwind_i.h
@@ -220,6 +220,9 @@ struct ia64_global_unwind_state
 #define tdep_get_elf_image		UNW_ARCH_OBJ(get_elf_image)
 #define tdep_access_reg			UNW_OBJ(access_reg)
 #define tdep_access_fpreg		UNW_OBJ(access_fpreg)
+#define tdep_fetch_frame(c,ip,n)	do {} while(0)
+#define tdep_cache_frame(c,rs)		do {} while(0)
+#define tdep_reuse_frame(c,rs)		do {} while(0)
 #define tdep_get_as(c)			((c)->as)
 #define tdep_get_as_arg(c)		((c)->as_arg)
 #define tdep_get_ip(c)			((c)->ip)
diff --git a/include/tdep-mips/libunwind_i.h b/include/tdep-mips/libunwind_i.h
index c2f756a1..298fae81 100644
--- a/include/tdep-mips/libunwind_i.h
+++ b/include/tdep-mips/libunwind_i.h
@@ -279,6 +279,9 @@ dwarf_put (struct dwarf_cursor *c, dwarf_loc_t loc, unw_word_t val)
 #define tdep_get_elf_image		UNW_ARCH_OBJ(get_elf_image)
 #define tdep_access_reg			UNW_OBJ(access_reg)
 #define tdep_access_fpreg		UNW_OBJ(access_fpreg)
+#define tdep_fetch_frame(c,ip,n)	do {} while(0)
+#define tdep_cache_frame(c,rs)		do {} while(0)
+#define tdep_reuse_frame(c,rs)		do {} while(0)
 
 #ifdef UNW_LOCAL_ONLY
 # define tdep_find_proc_info(c,ip,n)				\
diff --git a/include/tdep-ppc32/libunwind_i.h b/include/tdep-ppc32/libunwind_i.h
index 05dd1356..b963bca8 100644
--- a/include/tdep-ppc32/libunwind_i.h
+++ b/include/tdep-ppc32/libunwind_i.h
@@ -256,6 +256,9 @@ dwarf_put (struct dwarf_cursor *c, dwarf_loc_t loc, unw_word_t val)
 #define tdep_get_elf_image		UNW_ARCH_OBJ(get_elf_image)
 #define tdep_access_reg			UNW_OBJ(access_reg)
 #define tdep_access_fpreg		UNW_OBJ(access_fpreg)
+#define tdep_fetch_frame(c,ip,n)	do {} while(0)
+#define tdep_cache_frame(c,rs)		do {} while(0)
+#define tdep_reuse_frame(c,rs)		do {} while(0)
 #define tdep_get_func_addr		UNW_OBJ(get_func_addr)
 
 #ifdef UNW_LOCAL_ONLY
diff --git a/include/tdep-ppc64/libunwind_i.h b/include/tdep-ppc64/libunwind_i.h
index 192a0343..799b511f 100644
--- a/include/tdep-ppc64/libunwind_i.h
+++ b/include/tdep-ppc64/libunwind_i.h
@@ -256,6 +256,9 @@ dwarf_put (struct dwarf_cursor *c, dwarf_loc_t loc, unw_word_t val)
 #define tdep_get_elf_image		UNW_ARCH_OBJ(get_elf_image)
 #define tdep_access_reg			UNW_OBJ(access_reg)
 #define tdep_access_fpreg		UNW_OBJ(access_fpreg)
+#define tdep_fetch_frame(c,ip,n)	do {} while(0)
+#define tdep_cache_frame(c,rs)		do {} while(0)
+#define tdep_reuse_frame(c,rs)		do {} while(0)
 #define tdep_get_func_addr		UNW_OBJ(get_func_addr)
 
 #ifdef UNW_LOCAL_ONLY
diff --git a/include/tdep-x86/libunwind_i.h b/include/tdep-x86/libunwind_i.h
index 9af007d1..bed8cbf0 100644
--- a/include/tdep-x86/libunwind_i.h
+++ b/include/tdep-x86/libunwind_i.h
@@ -240,6 +240,9 @@ dwarf_put (struct dwarf_cursor *c, dwarf_loc_t loc, unw_word_t val)
 #define tdep_get_elf_image		UNW_ARCH_OBJ(get_elf_image)
 #define tdep_access_reg			UNW_OBJ(access_reg)
 #define tdep_access_fpreg		UNW_OBJ(access_fpreg)
+#define tdep_fetch_frame(c,ip,n)	do {} while(0)
+#define tdep_cache_frame(c,rs)		do {} while(0)
+#define tdep_reuse_frame(c,rs)		do {} while(0)
 
 #ifdef UNW_LOCAL_ONLY
 # define tdep_find_proc_info(c,ip,n)				\
diff --git a/include/tdep-x86_64/libunwind_i.h b/include/tdep-x86_64/libunwind_i.h
index f6a02897..c0227251 100644
--- a/include/tdep-x86_64/libunwind_i.h
+++ b/include/tdep-x86_64/libunwind_i.h
@@ -163,6 +163,15 @@ dwarf_put (struct dwarf_cursor *c, dwarf_loc_t loc, unw_word_t val)
 #define tdep_get_elf_image		UNW_ARCH_OBJ(get_elf_image)
 #define tdep_access_reg			UNW_OBJ(access_reg)
 #define tdep_access_fpreg		UNW_OBJ(access_fpreg)
+#if __linux__
+# define tdep_fetch_frame		UNW_OBJ(fetch_frame)
+# define tdep_cache_frame		UNW_OBJ(cache_frame)
+# define tdep_reuse_frame		UNW_OBJ(reuse_frame)
+#else
+# define tdep_fetch_frame(c,ip,n)	do {} while(0)
+# define tdep_cache_frame(c,rs)		do {} while(0)
+# define tdep_reuse_frame(c,rs)		do {} while(0)
+#endif
 
 #ifdef UNW_LOCAL_ONLY
 # define tdep_find_proc_info(c,ip,n)				\
@@ -196,5 +205,14 @@ extern int tdep_access_reg (struct cursor *c, unw_regnum_t reg,
 			    unw_word_t *valp, int write);
 extern int tdep_access_fpreg (struct cursor *c, unw_regnum_t reg,
 			      unw_fpreg_t *valp, int write);
+#if __linux__
+extern void tdep_fetch_frame (struct dwarf_cursor *c, unw_word_t ip,
+			      int need_unwind_info);
+extern void tdep_cache_frame (struct dwarf_cursor *c,
+			      struct dwarf_reg_state *rs);
+extern void tdep_reuse_frame (struct dwarf_cursor *c,
+			      struct dwarf_reg_state *rs);
+#endif
+
 
 #endif /* X86_64_LIBUNWIND_I_H */
diff --git a/src/arm/Ginit_local.c b/src/arm/Ginit_local.c
index 7b2881e3..debf5bb5 100644
--- a/src/arm/Ginit_local.c
+++ b/src/arm/Ginit_local.c
@@ -47,7 +47,7 @@ unw_init_local (unw_cursor_t *cursor, ucontext_t *uc)
 
   c->dwarf.as = unw_local_addr_space;
   c->dwarf.as_arg = uc;
-  return common_init (c);
+  return common_init (c, 1);
 }
 
 #endif /* !UNW_REMOTE_ONLY */
diff --git a/src/arm/Ginit_remote.c b/src/arm/Ginit_remote.c
index 3baf3f60..854f3b62 100644
--- a/src/arm/Ginit_remote.c
+++ b/src/arm/Ginit_remote.c
@@ -40,6 +40,6 @@ unw_init_remote (unw_cursor_t *cursor, unw_addr_space_t as, void *as_arg)
 
   c->dwarf.as = as;
   c->dwarf.as_arg = as_arg;
-  return common_init (c);
+  return common_init (c, 0);
 #endif /* !UNW_LOCAL_ONLY */
 }
diff --git a/src/arm/init.h b/src/arm/init.h
index 5b3f927d..a3025698 100644
--- a/src/arm/init.h
+++ b/src/arm/init.h
@@ -25,7 +25,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #include "unwind_i.h"
 
 static inline int
-common_init (struct cursor *c)
+common_init (struct cursor *c, unsigned use_prev_instr)
 {
   int ret, i;
 
@@ -62,6 +62,7 @@ common_init (struct cursor *c)
 
   c->dwarf.args_size = 0;
   c->dwarf.ret_addr_column = 0;
+  c->dwarf.use_prev_instr = use_prev_instr;
   c->dwarf.pi_valid = 0;
   c->dwarf.pi_is_dynamic = 0;
   c->dwarf.hint = 0;
diff --git a/src/dwarf/Gfde.c b/src/dwarf/Gfde.c
index 49e21db8..8659624b 100644
--- a/src/dwarf/Gfde.c
+++ b/src/dwarf/Gfde.c
@@ -187,6 +187,9 @@ parse_cie (unw_addr_space_t as, unw_accessors_t *a, unw_word_t addr,
 	break;
 
       case 'S':
+	/* This is a signal frame. */
+	dci->signal_frame = 1;
+
 	/* Temporarily set it to one so dwarf_parse_fde() knows that
 	   it should fetch the actual ABI/TAG pair from the FDE.  */
 	dci->have_abi_marker = 1;
@@ -293,7 +296,7 @@ dwarf_extract_proc_info_from_fde (unw_addr_space_t as, unw_accessors_t *a,
 	cie_addr = (unw_word_t) ((uint64_t) cie_offset_addr - cie_offset);
     }
 
-  Debug (15, "looking for CIE at address %x\n", (int) cie_addr);
+  Debug (15, "looking for CIE at address %lx\n", (long) cie_addr);
 
   if ((ret = parse_cie (as, a, cie_addr, pi, &dci, base, arg)) < 0)
     return ret;
diff --git a/src/dwarf/Gfind_proc_info-lsb.c b/src/dwarf/Gfind_proc_info-lsb.c
index d7405301..1b0a5292 100644
--- a/src/dwarf/Gfind_proc_info-lsb.c
+++ b/src/dwarf/Gfind_proc_info-lsb.c
@@ -275,7 +275,7 @@ locate_debug_info (unw_addr_space_t as, struct dl_phdr_info *info,
 
   for (w = as->debug_frames; w; w = w->next)
     {
-      Debug (4, "checking %p: %x-%x\n", w, (int)w->start, (int)w->end);
+      Debug (4, "checking %p: %lx-%lx\n", w, (long)w->start, (long)w->end);
       if (addr >= w->start && addr < w->end)
 	return w;
     }
@@ -316,7 +316,7 @@ locate_debug_info (unw_addr_space_t as, struct dl_phdr_info *info,
 	end = hdrlimit;
     }
 
-  Debug (4, "calculated bounds of %x-%x for '%s'\n", (int)start, (int)end,
+  Debug (4, "calculated bounds of %lx-%lx for '%s'\n", (long)start, (long)end,
 	 name);
   
   err = load_debug_frame (name, &buf, &bufsize, as == unw_local_addr_space);
@@ -667,8 +667,8 @@ callback (struct dl_phdr_info *info, size_t size, void *ptr)
           						  NULL);
           	  if (err == 0)
           	    {
-          	      Debug (15, "start_ip = %x, end_ip = %x\n",
-          		     (int) this_pi.start_ip, (int) this_pi.end_ip);
+		      Debug (15, "start_ip = %lx, end_ip = %lx\n",
+			     (long) this_pi.start_ip, (long) this_pi.end_ip);
           	      debug_frame_tab_append (tab,
           				      item_start - (unw_word_t) (uintptr_t) buf,
           				      this_pi.start_ip);
@@ -771,7 +771,7 @@ lookup (const struct table_entry *table, size_t table_size, int32_t rel_ip)
     {
       mid = (lo + hi) / 2;
       e = table + mid;
-      Debug (1, "e->start_ip_offset = %x\n", (int) e->start_ip_offset);
+      Debug (1, "e->start_ip_offset = %lx\n", (long) e->start_ip_offset);
       if (rel_ip < e->start_ip_offset)
 	hi = mid;
       else
@@ -897,8 +897,8 @@ dwarf_search_unwind_table (unw_addr_space_t as, unw_word_t ip,
     }
   if (!e)
     {
-      Debug (1, "IP %x inside range %x-%x, but no explicit unwind info found\n",
-	     (int) ip, (int) di->start_ip, (int) di->end_ip);
+      Debug (1, "IP %lx inside range %lx-%lx, but no explicit unwind info found\n",
+	     (long) ip, (long) di->start_ip, (long) di->end_ip);
       /* IP is inside this table's range, but there is no explicit
 	 unwind info.  */
       return -UNW_ENOINFO;
@@ -909,9 +909,9 @@ dwarf_search_unwind_table (unw_addr_space_t as, unw_word_t ip,
     fde_addr = e->fde_offset + debug_frame_base;
   else
     fde_addr = e->fde_offset + segbase;
-  Debug (1, "e->fde_offset = %x, segbase = %x, debug_frame_base = %x, "
-	    "fde_addr = %x\n", (int) e->fde_offset, (int) segbase,
-	    (int) debug_frame_base, (int) fde_addr);
+  Debug (1, "e->fde_offset = %lx, segbase = %lx, debug_frame_base = %lx, "
+	    "fde_addr = %lx\n", (long) e->fde_offset, (long) segbase,
+	    (long) debug_frame_base, (long) fde_addr);
   if ((ret = dwarf_extract_proc_info_from_fde (as, a, &fde_addr, pi,
 					       need_unwind_info,
 					       debug_frame_base, arg)) < 0)
diff --git a/src/dwarf/Gparser.c b/src/dwarf/Gparser.c
index db64b920..3b1a2b40 100644
--- a/src/dwarf/Gparser.c
+++ b/src/dwarf/Gparser.c
@@ -76,7 +76,10 @@ run_cfi_program (struct dwarf_cursor *c, dwarf_state_record_t *sr,
   a = unw_get_accessors (as);
   curr_ip = c->pi.start_ip;
 
-  while (curr_ip < ip && *addr < end_addr)
+  /* Process everything up to and including the current 'ip',
+     including all the DW_CFA_advance_loc instructions.  See
+     'c->use_prev_instr' use in 'fetch_proc_info' for details. */
+  while (curr_ip <= ip && *addr < end_addr)
     {
       if ((ret = dwarf_readu8 (as, a, addr, &op, arg)) < 0)
 	return ret;
@@ -381,7 +384,23 @@ fetch_proc_info (struct dwarf_cursor *c, unw_word_t ip, int need_unwind_info)
 {
   int ret, dynamic = 1;
 
-  --ip;
+  /* The 'ip' can point either to the previous or next instruction
+     depending on what type of frame we have: normal call or a place
+     to resume execution (e.g. after signal frame).
+
+     For a normal call frame we need to back up so we point within the
+     call itself; this is important because a) the call might be the
+     very last instruction of the function and the edge of the FDE,
+     and b) so that run_cfi_program() runs locations up to the call
+     but not more.
+
+     For execution resume, we need to do the exact opposite and look
+     up using the current 'ip' value.  That is where execution will
+     continue, and it's important we get this right, as 'ip' could be
+     right at the function entry and hence FDE edge, or at instruction
+     that manipulates CFA (push/pop). */
+  if (c->use_prev_instr)
+    --ip;
 
   if (c->pi_valid && !need_unwind_info)
     return 0;
@@ -400,6 +419,19 @@ fetch_proc_info (struct dwarf_cursor *c, unw_word_t ip, int need_unwind_info)
 
   c->pi_valid = 1;
   c->pi_is_dynamic = dynamic;
+
+  /* Let system/machine-dependent code determine frame-specific attributes. */
+  if (ret >= 0)
+    tdep_fetch_frame (c, ip, need_unwind_info);
+
+  /* Update use_prev_instr for the next frame. */
+  if (need_unwind_info)
+  {
+    assert(c->pi.unwind_info);
+    struct dwarf_cie_info *dci = c->pi.unwind_info;
+    c->use_prev_instr = ! dci->signal_frame;
+  }
+
   return ret;
 }
 
@@ -604,6 +636,8 @@ rs_new (struct dwarf_rs_cache *cache, struct dwarf_cursor * c)
   rs->hint = 0;
   rs->ip = c->ip;
   rs->ret_addr_column = c->ret_addr_column;
+  rs->signal_frame = 0;
+  tdep_cache_frame (c, rs);
 
   return rs;
 }
@@ -743,13 +777,20 @@ apply_reg_state (struct dwarf_cursor *c, struct dwarf_reg_state *rs)
 	  break;
 	}
     }
-  c->cfa = cfa;
-  ret = dwarf_get (c, c->loc[c->ret_addr_column], &ip);
-  if (ret < 0)
-    return ret;
-  c->ip = ip;
-  /* XXX: check for ip to be code_aligned */
 
+  c->cfa = cfa;
+  /* DWARF spec says undefined return address location means end of stack. */
+  if (DWARF_IS_NULL_LOC (c->loc[c->ret_addr_column]))
+    c->ip = 0;
+  else
+  {
+    ret = dwarf_get (c, c->loc[c->ret_addr_column], &ip);
+    if (ret < 0)
+      return ret;
+    c->ip = ip;
+  }
+
+  /* XXX: check for ip to be code_aligned */
   if (c->ip == prev_ip && c->cfa == prev_cfa)
     {
       Dprintf ("%s: ip and cfa unchanged; stopping here (ip=0x%lx)\n",
@@ -796,7 +837,10 @@ dwarf_find_save_locs (struct dwarf_cursor *c)
   rs = rs_lookup(cache, c);
 
   if (rs)
-    c->ret_addr_column = rs->ret_addr_column;
+    {
+      c->ret_addr_column = rs->ret_addr_column;
+      c->use_prev_instr = ! rs->signal_frame;
+    }
   else
     {
       if ((ret = fetch_proc_info (c, c->ip, 1)) < 0 ||
@@ -818,6 +862,8 @@ dwarf_find_save_locs (struct dwarf_cursor *c)
 
   memcpy (&rs_copy, rs, sizeof (rs_copy));
   put_rs_cache (c->as, cache, &saved_mask);
+
+  tdep_reuse_frame (c, &rs_copy);
   if ((ret = apply_reg_state (c, &rs_copy)) < 0)
     return ret;
 
diff --git a/src/hppa/Ginit_local.c b/src/hppa/Ginit_local.c
index 243ffd49..6d4dd3df 100644
--- a/src/hppa/Ginit_local.c
+++ b/src/hppa/Ginit_local.c
@@ -48,7 +48,7 @@ unw_init_local (unw_cursor_t *cursor, ucontext_t *uc)
 
   c->dwarf.as = unw_local_addr_space;
   c->dwarf.as_arg = uc;
-  return common_init (c);
+  return common_init (c, 1);
 }
 
 #endif /* !UNW_REMOTE_ONLY */
diff --git a/src/hppa/Ginit_remote.c b/src/hppa/Ginit_remote.c
index 3d6606df..bd6093f1 100644
--- a/src/hppa/Ginit_remote.c
+++ b/src/hppa/Ginit_remote.c
@@ -41,6 +41,6 @@ unw_init_remote (unw_cursor_t *cursor, unw_addr_space_t as, void *as_arg)
 
   c->dwarf.as = as;
   c->dwarf.as_arg = as_arg;
-  return common_init (c);
+  return common_init (c, 0);
 #endif /* !UNW_LOCAL_ONLY */
 }
diff --git a/src/hppa/init.h b/src/hppa/init.h
index d5f900d4..d14354f6 100644
--- a/src/hppa/init.h
+++ b/src/hppa/init.h
@@ -26,7 +26,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #include "unwind_i.h"
 
 static inline int
-common_init (struct cursor *c)
+common_init (struct cursor *c, unsigned use_prev_instr)
 {
   int ret;
 
@@ -40,5 +40,7 @@ common_init (struct cursor *c)
   ret = hppa_get (c, HPPA_REG_LOC (c, UNW_HPPA_SP), &c->sp);
   if (ret < 0)
     return ret;
+
+  c->dwarf.use_prev_instr = use_prev_instr;
   return 0;
 }
diff --git a/src/mips/Ginit_local.c b/src/mips/Ginit_local.c
index 7b2881e3..debf5bb5 100644
--- a/src/mips/Ginit_local.c
+++ b/src/mips/Ginit_local.c
@@ -47,7 +47,7 @@ unw_init_local (unw_cursor_t *cursor, ucontext_t *uc)
 
   c->dwarf.as = unw_local_addr_space;
   c->dwarf.as_arg = uc;
-  return common_init (c);
+  return common_init (c, 1);
 }
 
 #endif /* !UNW_REMOTE_ONLY */
diff --git a/src/mips/Ginit_remote.c b/src/mips/Ginit_remote.c
index 3baf3f60..854f3b62 100644
--- a/src/mips/Ginit_remote.c
+++ b/src/mips/Ginit_remote.c
@@ -40,6 +40,6 @@ unw_init_remote (unw_cursor_t *cursor, unw_addr_space_t as, void *as_arg)
 
   c->dwarf.as = as;
   c->dwarf.as_arg = as_arg;
-  return common_init (c);
+  return common_init (c, 0);
 #endif /* !UNW_LOCAL_ONLY */
 }
diff --git a/src/mips/init.h b/src/mips/init.h
index 98956d4a..e32e3c9e 100644
--- a/src/mips/init.h
+++ b/src/mips/init.h
@@ -25,7 +25,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #include "unwind_i.h"
 
 static inline int
-common_init (struct cursor *c)
+common_init (struct cursor *c, unsigned use_prev_instr)
 {
   int ret, i;
 
@@ -47,6 +47,7 @@ common_init (struct cursor *c)
 
   c->dwarf.args_size = 0;
   c->dwarf.ret_addr_column = 0;
+  c->dwarf.use_prev_instr = use_prev_instr;
   c->dwarf.pi_valid = 0;
   c->dwarf.pi_is_dynamic = 0;
   c->dwarf.hint = 0;
diff --git a/src/ppc/Ginit_local.c b/src/ppc/Ginit_local.c
index 2d9ab2ce..b931b5b6 100644
--- a/src/ppc/Ginit_local.c
+++ b/src/ppc/Ginit_local.c
@@ -56,9 +56,9 @@ unw_init_local (unw_cursor_t *cursor, ucontext_t *uc)
   c->dwarf.as = unw_local_addr_space;
   c->dwarf.as_arg = uc;
   #ifdef UNW_TARGET_PPC64
-    return common_init_ppc64 (c);
+    return common_init_ppc64 (c, 1);
   #else
-    return common_init_ppc32 (c);
+    return common_init_ppc32 (c, 1);
   #endif
 }
 
diff --git a/src/ppc/Ginit_remote.c b/src/ppc/Ginit_remote.c
index 66269d2c..0f4b0fdb 100644
--- a/src/ppc/Ginit_remote.c
+++ b/src/ppc/Ginit_remote.c
@@ -50,9 +50,9 @@ unw_init_remote (unw_cursor_t *cursor, unw_addr_space_t as, void *as_arg)
   c->dwarf.as_arg = as_arg;
 
   #ifdef UNW_TARGET_PPC64
-    return common_init_ppc64(c);
+    return common_init_ppc64 (c, 0);
   #elif UNW_TARGET_PPC32
-    return common_init_ppc32 (c);
+    return common_init_ppc32 (c, 0);
   #else
     #error init_remote :: NO VALID PPC ARCH!
   #endif
diff --git a/src/ppc32/init.h b/src/ppc32/init.h
index 8badb178..c2208ad9 100644
--- a/src/ppc32/init.h
+++ b/src/ppc32/init.h
@@ -30,7 +30,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 /* Here is the "common" init, for remote and local debuging" */
 
 static inline int
-common_init_ppc32 (struct cursor *c)
+common_init_ppc32 (struct cursor *c, unsigned use_prev_instr)
 {
   int ret;
   int i;
@@ -62,6 +62,7 @@ common_init_ppc32 (struct cursor *c)
 
   c->dwarf.args_size = 0;
   c->dwarf.ret_addr_column = 0;
+  c->dwarf.use_prev_instr = use_prev_instr;
   c->dwarf.pi_valid = 0;
   c->dwarf.pi_is_dynamic = 0;
   c->dwarf.hint = 0;
diff --git a/src/ppc64/init.h b/src/ppc64/init.h
index 886f14c4..64847b84 100644
--- a/src/ppc64/init.h
+++ b/src/ppc64/init.h
@@ -28,7 +28,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #include "unwind_i.h"
 
 static inline int
-common_init_ppc64 (struct cursor *c)
+common_init_ppc64 (struct cursor *c, unsigned use_prev_instr)
 {
   int ret;
   int i;
@@ -72,6 +72,7 @@ common_init_ppc64 (struct cursor *c)
 
   c->dwarf.args_size = 0;
   c->dwarf.ret_addr_column = 0;
+  c->dwarf.use_prev_instr = use_prev_instr;
   c->dwarf.pi_valid = 0;
   c->dwarf.pi_is_dynamic = 0;
   c->dwarf.hint = 0;
diff --git a/src/x86/Ginit_local.c b/src/x86/Ginit_local.c
index 55ab7490..5e8b6972 100644
--- a/src/x86/Ginit_local.c
+++ b/src/x86/Ginit_local.c
@@ -50,7 +50,7 @@ unw_init_local (unw_cursor_t *cursor, ucontext_t *uc)
   c->dwarf.as_arg = c;
   c->uc = uc;
   c->validate = 0;
-  return common_init (c);
+  return common_init (c, 1);
 }
 
 #endif /* !UNW_REMOTE_ONLY */
diff --git a/src/x86/Ginit_remote.c b/src/x86/Ginit_remote.c
index 6949a73e..aa924052 100644
--- a/src/x86/Ginit_remote.c
+++ b/src/x86/Ginit_remote.c
@@ -51,6 +51,6 @@ unw_init_remote (unw_cursor_t *cursor, unw_addr_space_t as, void *as_arg)
       c->dwarf.as_arg = as_arg;
       c->uc = 0;
     }
-  return common_init (c);
+  return common_init (c, 0);
 #endif /* !UNW_LOCAL_ONLY */
 }
diff --git a/src/x86/getcontext-freebsd.S b/src/x86/getcontext-freebsd.S
index 17adade8..dfeb4328 100644
--- a/src/x86/getcontext-freebsd.S
+++ b/src/x86/getcontext-freebsd.S
@@ -27,6 +27,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 	.global _Ux86_getcontext
 	.type _Ux86_getcontext, @function
 _Ux86_getcontext:
+	.cfi_startproc
 	pushl	%eax
 	mov	8(%esp),%eax  /* ucontext_t* */
 	popl	FREEBSD_UC_MCONTEXT_EAX_OFF(%eax)
@@ -97,6 +98,7 @@ _Ux86_getcontext:
 
 	xorl	%eax, %eax
 	ret
+	.cfi_endproc
 	.size	_Ux86_getcontext, . - _Ux86_getcontext
 
 	/* We do not need executable stack.  */
diff --git a/src/x86/getcontext-linux.S b/src/x86/getcontext-linux.S
index a0714cd1..c469dadb 100644
--- a/src/x86/getcontext-linux.S
+++ b/src/x86/getcontext-linux.S
@@ -36,6 +36,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 	.global _Ux86_getcontext
 	.type _Ux86_getcontext, @function
 _Ux86_getcontext:
+	.cfi_startproc
 	mov	4(%esp),%eax  /* ucontext_t* */
 
 	/* EAX is not preserved. */
@@ -66,6 +67,7 @@ _Ux86_getcontext:
 
 	xor	%eax, %eax
 	ret
+	.cfi_endproc
 	.size	_Ux86_getcontext, . - _Ux86_getcontext
 
 	/* We do not need executable stack.  */
diff --git a/src/x86/init.h b/src/x86/init.h
index 675b77e5..b59ad842 100644
--- a/src/x86/init.h
+++ b/src/x86/init.h
@@ -26,7 +26,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #include "unwind_i.h"
 
 static inline int
-common_init (struct cursor *c)
+common_init (struct cursor *c, unsigned use_prev_instr)
 {
   int ret, i;
 
@@ -59,6 +59,7 @@ common_init (struct cursor *c)
 
   c->dwarf.args_size = 0;
   c->dwarf.ret_addr_column = 0;
+  c->dwarf.use_prev_instr = use_prev_instr;
   c->dwarf.pi_valid = 0;
   c->dwarf.pi_is_dynamic = 0;
   c->dwarf.hint = 0;
diff --git a/src/x86_64/Ginit_local.c b/src/x86_64/Ginit_local.c
index 1e80cb85..18b3d989 100644
--- a/src/x86_64/Ginit_local.c
+++ b/src/x86_64/Ginit_local.c
@@ -51,8 +51,12 @@ unw_init_local (unw_cursor_t *cursor, ucontext_t *uc)
   c->dwarf.as = unw_local_addr_space;
   c->dwarf.as_arg = c;
   c->uc = uc;
+#if CONSERVATIVE_CHECKS
+  c->validate = 1;
+#else
   c->validate = 0;
-  return common_init (c);
+#endif
+  return common_init (c, 1);
 }
 
 #endif /* !UNW_REMOTE_ONLY */
diff --git a/src/x86_64/Ginit_remote.c b/src/x86_64/Ginit_remote.c
index 8aa644d3..25dd6860 100644
--- a/src/x86_64/Ginit_remote.c
+++ b/src/x86_64/Ginit_remote.c
@@ -52,6 +52,6 @@ unw_init_remote (unw_cursor_t *cursor, unw_addr_space_t as, void *as_arg)
       c->dwarf.as_arg = as_arg;
       c->uc = 0;
     }
-  return common_init (c);
+  return common_init (c, 0);
 #endif /* !UNW_LOCAL_ONLY */
 }
diff --git a/src/x86_64/Gos-linux.c b/src/x86_64/Gos-linux.c
index 1bf4ba2f..957f3e30 100644
--- a/src/x86_64/Gos-linux.c
+++ b/src/x86_64/Gos-linux.c
@@ -30,74 +30,76 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 
 #include <sys/syscall.h>
 
+HIDDEN void
+tdep_fetch_frame (struct dwarf_cursor *dw, unw_word_t ip, int need_unwind_info)
+{
+  struct cursor *c = (struct cursor *) dw;
+  assert(! need_unwind_info || dw->pi_valid);
+  assert(! need_unwind_info || dw->pi.unwind_info);
+  if (dw->pi_valid
+      && dw->pi.unwind_info
+      && ((struct dwarf_cie_info *) dw->pi.unwind_info)->signal_frame)
+  {
+    c->sigcontext_format = X86_64_SCF_LINUX_RT_SIGFRAME;
+    c->sigcontext_addr = dw->cfa;
+  }
+  else
+  {
+    c->sigcontext_format = X86_64_SCF_NONE;
+    c->sigcontext_addr = 0;
+  }
+
+  Debug(15, "fetch frame ip=0x%lx cfa=0x%lx format=%d addr=0x%lx\n",
+        dw->ip, dw->cfa, c->sigcontext_format, c->sigcontext_addr);
+}
+
+HIDDEN void
+tdep_cache_frame (struct dwarf_cursor *dw, struct dwarf_reg_state *rs)
+{
+  struct cursor *c = (struct cursor *) dw;
+  rs->signal_frame = c->sigcontext_format;
+
+  Debug(15, "cache frame ip=0x%lx cfa=0x%lx format=%d addr=0x%lx\n",
+        dw->ip, dw->cfa, c->sigcontext_format, c->sigcontext_addr);
+}
+
+HIDDEN void
+tdep_reuse_frame (struct dwarf_cursor *dw, struct dwarf_reg_state *rs)
+{
+  struct cursor *c = (struct cursor *) dw;
+  c->sigcontext_format = rs->signal_frame;
+  if (c->sigcontext_format == X86_64_SCF_LINUX_RT_SIGFRAME)
+    c->sigcontext_addr = dw->cfa;
+  else
+    c->sigcontext_addr = 0;
+
+  Debug(15, "reuse frame ip=0x%lx cfa=0x%lx format=%d addr=0x%lx\n",
+        dw->ip, dw->cfa, c->sigcontext_format, c->sigcontext_addr);
+}
+
 PROTECTED int
 unw_is_signal_frame (unw_cursor_t *cursor)
 {
   struct cursor *c = (struct cursor *) cursor;
-  unw_word_t w0, w1, ip;
-  unw_addr_space_t as;
-  unw_accessors_t *a;
-  void *arg;
-  int ret;
-
-  as = c->dwarf.as;
-  a = unw_get_accessors (as);
-  arg = c->dwarf.as_arg;
-
-  /* Check if RIP points at sigreturn sequence.
-     on x86_64 Linux that is (see libc.so):
-     48 c7 c0 0f 00 00 00 mov $0xf,%rax
-     0f 05                syscall
-     66                   data16
-  */
-
-  ip = c->dwarf.ip;
-  if ((ret = (*a->access_mem) (as, ip, &w0, 0, arg)) < 0
-      || (ret = (*a->access_mem) (as, ip + 8, &w1, 0, arg)) < 0)
-    return 0;
-  w1 &= 0xff;
-  return (w0 == 0x0f0000000fc0c748 && w1 == 0x05);
+  return c->sigcontext_format != X86_64_SCF_NONE;
 }
 
 PROTECTED int
 unw_handle_signal_frame (unw_cursor_t *cursor)
 {
-  struct cursor *c = (struct cursor *) cursor;
-  int ret;
-  unw_word_t ucontext = c->dwarf.cfa;
-
-  Debug(1, "signal frame, skip over trampoline\n");
-
-  c->sigcontext_format = X86_64_SCF_LINUX_RT_SIGFRAME;
-  c->sigcontext_addr = c->dwarf.cfa;
-
-  struct dwarf_loc rsp_loc = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_RSP, 0);
-  ret = dwarf_get (&c->dwarf, rsp_loc, &c->dwarf.cfa);
-  if (ret < 0)
-    {
-      Debug (2, "returning %d\n", ret);
-      return ret;
-    }
-
-  c->dwarf.loc[RAX] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_RAX, 0);
-  c->dwarf.loc[RDX] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_RDX, 0);
-  c->dwarf.loc[RCX] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_RCX, 0);
-  c->dwarf.loc[RBX] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_RBX, 0);
-  c->dwarf.loc[RSI] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_RSI, 0);
-  c->dwarf.loc[RDI] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_RDI, 0);
-  c->dwarf.loc[RBP] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_RBP, 0);
-  c->dwarf.loc[RSP] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_RSP, 0);
-  c->dwarf.loc[ R8] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_R8, 0);
-  c->dwarf.loc[ R9] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_R9, 0);
-  c->dwarf.loc[R10] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_R10, 0);
-  c->dwarf.loc[R11] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_R11, 0);
-  c->dwarf.loc[R12] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_R12, 0);
-  c->dwarf.loc[R13] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_R13, 0);
-  c->dwarf.loc[R14] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_R14, 0);
-  c->dwarf.loc[R15] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_R15, 0);
-  c->dwarf.loc[RIP] = DWARF_LOC (ucontext + UC_MCONTEXT_GREGS_RIP, 0);
-
-  return 0;
+#if UNW_DEBUG /* To silence compiler warnings */
+  /* Should not get here because we now use kernel-provided dwarf
+     information for the signal trampoline and dwarf_step() works.
+     Hence dwarf_step() should never call this function. Maybe
+     restore old non-dwarf signal handling here, but then the
+     gating on unw_is_signal_frame() needs to be removed. */
+  Debug(1, "old format signal frame? format=%d addr=0x%lx cfa=0x%lx\n",
+	c->sigcontext_format, c->sigcontext_addr, c->dwarf.cfa);
+  assert(c->sigcontext_format == X86_64_SCF_LINUX_RT_SIGFRAME);
+  assert(c->sigcontext_addr == c->dwarf.cfa);
+  assert(0);
+#endif
+  return 1;
 }
 
 #ifndef UNW_REMOTE_ONLY
diff --git a/src/x86_64/Gstep.c b/src/x86_64/Gstep.c
index d23be8ea..237811ce 100644
--- a/src/x86_64/Gstep.c
+++ b/src/x86_64/Gstep.c
@@ -38,6 +38,7 @@ unw_step (unw_cursor_t *cursor)
 	 c, (unsigned long long) c->dwarf.ip);
 
   /* Try DWARF-based unwinding... */
+  c->sigcontext_format = X86_64_SCF_NONE;
   ret = dwarf_step (&c->dwarf);
 
   if (ret < 0 && ret != -UNW_ENOINFO)
@@ -85,6 +86,11 @@ unw_step (unw_cursor_t *cursor)
 	      return 0;
 	    }
 	}
+      else if (DWARF_IS_NULL_LOC (c->dwarf.loc[RBP]))
+        {
+	  for (i = 0; i < DWARF_NUM_PRESERVED_REGS; ++i)
+	    c->dwarf.loc[i] = DWARF_NULL_LOC;
+	}
       else
 	{
 	  unw_word_t rbp;
@@ -92,7 +98,8 @@ unw_step (unw_cursor_t *cursor)
 	  ret = dwarf_get (&c->dwarf, c->dwarf.loc[RBP], &rbp);
 	  if (ret < 0)
 	    {
-	      Debug (2, "returning %d\n", ret);
+	      Debug (2, "returning %d [RBP=0x%lx]\n", ret,
+		     DWARF_GET_LOC (c->dwarf.loc[RBP]));
 	      return ret;
 	    }
 
diff --git a/src/x86_64/getcontext.S b/src/x86_64/getcontext.S
index a0df6f15..15fff283 100644
--- a/src/x86_64/getcontext.S
+++ b/src/x86_64/getcontext.S
@@ -37,6 +37,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 	.global _Ux86_64_getcontext
 	.type _Ux86_64_getcontext, @function
 _Ux86_64_getcontext:
+	.cfi_startproc
 
 	/* Callee saved: RBX, RBP, R12-R15  */
 	movq %r12, UC_MCONTEXT_GREGS_R12(%rdi)
@@ -70,7 +71,9 @@ _Ux86_64_getcontext:
 	/* Save rflags and segment registers, so that sigreturn(2)
 	does not complain. */
 	pushfq
+	.cfi_adjust_cfa_offset 8
 	popq UC_MCONTEXT_RFLAGS(%rdi)
+	.cfi_adjust_cfa_offset -8
 	movl $0, UC_MCONTEXT_FLAGS(%rdi)
 	movw %cs, UC_MCONTEXT_CS(%rdi)
 	movw %ss, UC_MCONTEXT_SS(%rdi)
@@ -95,6 +98,7 @@ _Ux86_64_getcontext:
 
 	xorq	%rax, %rax
 	retq
+	.cfi_endproc
 	.size _Ux86_64_getcontext, . - _Ux86_64_getcontext
 
       /* We do not need executable stack.  */
diff --git a/src/x86_64/init.h b/src/x86_64/init.h
index ae108b24..dcd4aea2 100644
--- a/src/x86_64/init.h
+++ b/src/x86_64/init.h
@@ -28,7 +28,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #include "unwind_i.h"
 
 static inline int
-common_init (struct cursor *c)
+common_init (struct cursor *c, unsigned use_prev_instr)
 {
   int ret;
 
@@ -64,6 +64,7 @@ common_init (struct cursor *c)
 
   c->dwarf.args_size = 0;
   c->dwarf.ret_addr_column = RIP;
+  c->dwarf.use_prev_instr = use_prev_instr;
   c->dwarf.pi_valid = 0;
   c->dwarf.pi_is_dynamic = 0;
   c->dwarf.hint = 0;
diff --git a/tests/run-ptrace-mapper b/tests/run-ptrace-mapper
index f51cf9a1..dc3010d4 100755
--- a/tests/run-ptrace-mapper
+++ b/tests/run-ptrace-mapper
@@ -1,2 +1,2 @@
 #!/bin/sh
-./test-ptrace -c -n -t ./mapper
+./test-ptrace -c -n -t ./mapper $*