aarch64: PLT entry recognition & fixes

Attached is a corrected version of my previous patch for aarch64 PLT
entry recognition. The comparison in the is_plt_entry function should
have been:

     ret = (((w0 & 0xff0000009f000000) == 0xf900000090000000)
            && ((w1 & 0xffffffffff000000) == 0xd61f022091000000));

src/aarch64/Gstep.c

@@ -27,6 +27,30 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #include "unwind_i.h"
 #include "offsets.h"
 
+/* Recognise PLT entries such as:
+  40ddf0:       b0000570        adrp    x16, 4ba000 <_GLOBAL_OFFSET_TABLE_+0x2a8>
+  40ddf4:       f9433611        ldr     x17, [x16,#1640]
+  40ddf8:       9119a210        add     x16, x16, #0x668
+  40ddfc:       d61f0220        br      x17 */
+static int
+is_plt_entry (struct dwarf_cursor *c)
+{
+  unw_word_t w0, w1;
+  unw_accessors_t *a;
+  int ret;
+
+  a = unw_get_accessors (c->as);
+  if ((ret = (*a->access_mem) (c->as, c->ip, &w0, 0, c->as_arg)) < 0
+      || (ret = (*a->access_mem) (c->as, c->ip + 8, &w1, 0, c->as_arg)) < 0)
+    return 0;
+
+  ret = (((w0 & 0xff0000009f000000) == 0xf900000090000000)
+         && ((w1 & 0xffffffffff000000) == 0xd61f022091000000));
+
+  Debug (14, "ip=0x%lx => 0x%016lx 0x%016lx, ret = %d\n", c->ip, w0, w1, ret);
+  return ret;
+}
+
 PROTECTED int
 unw_handle_signal_frame (unw_cursor_t *cursor)
 {
@@ -101,6 +125,7 @@ unw_handle_signal_frame (unw_cursor_t *cursor)
   dwarf_get (&c->dwarf, c->dwarf.loc[UNW_AARCH64_PC], &c->dwarf.ip);
 
   c->dwarf.pi_valid = 0;
+  c->dwarf.use_prev_instr = 0;
 
   return 1;
 }
@@ -125,7 +150,40 @@ unw_step (unw_cursor_t *cursor)
     return ret;
 
   if (unlikely (ret < 0))
-    return 0;
+    {
+      /* DWARF failed. */
+      if (is_plt_entry (&c->dwarf))
+        {
+          Debug (2, "found plt entry\n");
+          c->frame_info.frame_type = UNW_AARCH64_FRAME_STANDARD;
+        }
+      else
+        {
+          Debug (2, "fallback\n");
+          c->frame_info.frame_type = UNW_AARCH64_FRAME_GUESSED;
+        }
+      /* Use link register (X30). */
+      c->frame_info.cfa_reg_offset = 0;
+      c->frame_info.cfa_reg_sp = 0;
+      c->frame_info.fp_cfa_offset = -1;
+      c->frame_info.lr_cfa_offset = -1;
+      c->frame_info.sp_cfa_offset = -1;
+      c->dwarf.loc[UNW_AARCH64_PC] = c->dwarf.loc[UNW_AARCH64_X30];
+      c->dwarf.loc[UNW_AARCH64_X30] = DWARF_NULL_LOC;
+      if (!DWARF_IS_NULL_LOC (c->dwarf.loc[UNW_AARCH64_PC]))
+        {
+          ret = dwarf_get (&c->dwarf, c->dwarf.loc[UNW_AARCH64_PC], &c->dwarf.ip);
+          if (ret < 0)
+            {
+              Debug (2, "failed to get pc from link register: %d\n", ret);
+              return ret;
+            }
+          Debug (2, "link register (x30) = 0x%016lx\n", c->dwarf.ip);
+          ret = 1;
+        }
+      else
+        c->dwarf.ip = 0;
+    }
 
   return (c->dwarf.ip == 0) ? 0 : 1;
 }

src/dwarf/Gfde.c

@@ -32,7 +32,7 @@ is_cie_id (unw_word_t val, int is_debug_frame)
      0xffffffffffffffff (for 64-bit ELF).  However, .eh_frame
      uses 0.  */
   if (is_debug_frame)
-    return (val == - (uint32_t) 1 || val == - (uint64_t) 1);
+      return (val == (uint32_t)(-1) || val == (uint64_t)(-1));
   else
     return (val == 0);
 }

src/dwarf/Gfind_proc_info-lsb.c

@@ -199,7 +199,7 @@ locate_debug_info (unw_addr_space_t as, unw_word_t addr, const char *dlname,
     name = (char*) dlname;
 
   err = load_debug_frame (name, &buf, &bufsize, as == unw_local_addr_space);
-  
+
   if (!err)
     {
       fdesc = malloc (sizeof (struct unw_debug_frame_list));
@@ -210,10 +210,10 @@ locate_debug_info (unw_addr_space_t as, unw_word_t addr, const char *dlname,
       fdesc->debug_frame_size = bufsize;
       fdesc->index = NULL;
       fdesc->next = as->debug_frames;
-      
+
       as->debug_frames = fdesc;
     }
-  
+
   return fdesc;
 }
 
@@ -235,10 +235,10 @@ debug_frame_tab_append (struct debug_frame_tab *tab,
       tab->size *= 2;
       tab->tab = realloc (tab->tab, sizeof (struct table_entry) * tab->size);
     }
-  
+
   tab->tab[length].fde_offset = fde_offset;
   tab->tab[length].start_ip_offset = start_ip;
-  
+
   tab->length = length + 1;
 }
 
@@ -256,7 +256,7 @@ static int
 debug_frame_tab_compare (const void *a, const void *b)
 {
   const struct table_entry *fa = a, *fb = b;
-  
+
   if (fa->start_ip_offset > fb->start_ip_offset)
     return 1;
   else if (fa->start_ip_offset < fb->start_ip_offset)
@@ -522,7 +522,7 @@ dwarf_callback (struct dl_phdr_info *info, size_t size, void *ptr)
       else if (phdr->p_type == PT_DYNAMIC)
         p_dynamic = phdr;
     }
-  
+
   if (!p_text)
     return 0;