[PATCH] Break out of while loop correctly to make sure loclists are adjusted.

[PATCH] Break out of while loop correctly to make sure loclists are adjusted.

[Mark Wielaard]

The reading and adjusting of DWARF5 .debug_loclists was modelled on
the DWARF4 .debug_loc section parsing. The .debug_loc parsing used
a while loop and breaks out when done. But .debug_loclists use a
switch statement inside the  while loop, so break doesn't actually
break out of the loop when done, and return on end of list exits
the functions too early. This meant that although the loclists were
parsed correctly, then were then not actually adjusted. Fix this
by using gotos inside the switch statements.

	* dwz.c (read_loclist_low_mem_phase1): Use again and done
	labels to goto inside switch.
	(read_loclist): Likewise.
	(adjust_loclist): Likewise.
---
 dwz.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/dwz.c b/dwz.c
index b3cf346..8903570 100644
--- a/dwz.c
+++ b/dwz.c
@@ -2807,6 +2807,7 @@ read_loclist_low_mem_phase1 (DSO *dso, dw_cu_ref cu, dw_die_ref die,
     }
   endsec = ptr + debug_sections[sec].size;
   ptr += offset;
+again:
   while (ptr < endsec)
     {
       if (sec == DEBUG_LOC)
@@ -2828,11 +2829,11 @@ read_loclist_low_mem_phase1 (DSO *dso, dw_cu_ref cu, dw_die_ref die,
 	  switch (lle)
 	    {
 	    case DW_LLE_end_of_list:
-	      return 0;
+	      goto done;
 
 	    case DW_LLE_base_addressx:
 	      skip_leb128 (ptr);
-	      continue;
+	      goto again;
 
 	    case DW_LLE_startx_endx:
 	      skip_leb128 (ptr);
@@ -2858,7 +2859,7 @@ read_loclist_low_mem_phase1 (DSO *dso, dw_cu_ref cu, dw_die_ref die,
 
 	    case DW_LLE_base_address:
 	      ptr += ptr_size;
-	      continue;
+	      goto again;
 
 	    case DW_LLE_start_end:
 	      ptr += 2 * ptr_size;
@@ -2878,7 +2879,7 @@ read_loclist_low_mem_phase1 (DSO *dso, dw_cu_ref cu, dw_die_ref die,
 		       dso->filename, cu->cu_version);
 	      skip_leb128 (ptr);
 	      skip_leb128 (ptr);
-	      continue;
+	      goto again;
 
 	    default:
 	      error (0, 0,
@@ -2903,6 +2904,7 @@ read_loclist_low_mem_phase1 (DSO *dso, dw_cu_ref cu, dw_die_ref die,
       ptr += len;
     }
 
+done:
   return 0;
 }
 
@@ -3061,6 +3063,7 @@ read_loclist (DSO *dso, dw_cu_ref cu, dw_die_ref die, GElf_Addr offset)
     }
   endsec = ptr + debug_sections[sec].size;
   ptr += offset;
+again:
   while (ptr < endsec)
     {
       if (cu->cu_version < 5)
@@ -3082,11 +3085,11 @@ read_loclist (DSO *dso, dw_cu_ref cu, dw_die_ref die, GElf_Addr offset)
 	  switch (lle)
 	    {
 	    case DW_LLE_end_of_list:
-	      return 0;
+	      goto done;
 
 	    case DW_LLE_base_addressx:
 	      skip_leb128 (ptr);
-	      continue;
+	      goto again;
 
 	    case DW_LLE_startx_endx:
 	      skip_leb128 (ptr);
@@ -3112,7 +3115,7 @@ read_loclist (DSO *dso, dw_cu_ref cu, dw_die_ref die, GElf_Addr offset)
 
 	    case DW_LLE_base_address:
 	      ptr += ptr_size;
-	      continue;
+	      goto again;
 
 	    case DW_LLE_start_end:
 	      ptr += 2 * ptr_size;
@@ -3132,7 +3135,7 @@ read_loclist (DSO *dso, dw_cu_ref cu, dw_die_ref die, GElf_Addr offset)
 		       dso->filename, cu->cu_version);
 	      skip_leb128 (ptr);
 	      skip_leb128 (ptr);
-	      continue;
+	      goto again;
 
 	    default:
 	      error (0, 0,
@@ -3156,6 +3159,7 @@ read_loclist (DSO *dso, dw_cu_ref cu, dw_die_ref die, GElf_Addr offset)
       ptr += len;
     }
 
+done:
   if (need_adjust)
     {
       struct debug_loc_adjust adj, *a;
@@ -12708,17 +12712,18 @@ adjust_loclists (void **slot, void *data)
   ptr = debug_sections[DEBUG_LOCLISTS].new_data + adj->start_offset;
   endsec = ptr + debug_sections[DEBUG_LOCLISTS].size;
 
+again:
   while (ptr < endsec)
     {
       uint8_t lle = *ptr++;
       switch (lle)
 	{
 	case DW_LLE_end_of_list:
-	  return 1;
+	  goto done;
 
 	case DW_LLE_base_addressx:
 	  skip_leb128 (ptr);
-	  continue;
+	  goto again;
 
 	case DW_LLE_startx_endx:
 	  skip_leb128 (ptr);
@@ -12744,7 +12749,7 @@ adjust_loclists (void **slot, void *data)
 
 	case DW_LLE_base_address:
 	  ptr += ptr_size;
-	  continue;
+	  goto again;
 
 	case DW_LLE_start_end:
 	  ptr += 2 * ptr_size;
@@ -12762,7 +12767,7 @@ adjust_loclists (void **slot, void *data)
 	     warning on the original parsing if CU version is not 5.*/
 	  skip_leb128 (ptr);
 	  skip_leb128 (ptr);
-	  continue;
+	  goto again;
 
 	default:
 	  error (0, 0, "unhandled location list entry 0x%x", lle);
@@ -12777,6 +12782,7 @@ adjust_loclists (void **slot, void *data)
       ptr += len;
     }
 
+done:
   return 1;
 }
 
-- 
2.18.4

Re: [PATCH] Break out of while loop correctly to make sure loclists are adjusted.

[Jakub Jelinek]

On Sun, Jan 17, 2021 at 11:25:59PM +0100, Mark Wielaard wrote:
> The reading and adjusting of DWARF5 .debug_loclists was modelled on
> the DWARF4 .debug_loc section parsing. The .debug_loc parsing used
> a while loop and breaks out when done. But .debug_loclists use a
> switch statement inside the  while loop, so break doesn't actually
> break out of the loop when done, and return on end of list exits
> the functions too early. This meant that although the loclists were
> parsed correctly, then were then not actually adjusted. Fix this
> by using gotos inside the switch statements.
> 
> 	* dwz.c (read_loclist_low_mem_phase1): Use again and done
> 	labels to goto inside switch.
> 	(read_loclist): Likewise.
> 	(adjust_loclist): Likewise.

Ok, thanks.

	Jakub