dwarf: Read register number as unsigned in DW_CFA_def_cfa*

When displaying the .debug_frame section, the register numbers in the
DW_CFA_def_cfa* statements are read as signed numbers.  I have come
across a target that has register 121, encoded as 0x79 in unsigned LEB128.
Interpreting this as signed results in -7, which makes readelf display
"r-7".

The DWARF5 standard (6.4.2.2) states that the register numbers should be
treated as unsigned LEB128.

Simply replacing READ_SLEB with READ_ULEB resulted in warnings like
these:

/home/emaisin/src/binutils-gdb/binutils/dwarf.c: In function ‘display_debug_frames’:
/home/emaisin/src/binutils-gdb/binutils/dwarf.c:355:17: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
       if ((var) != _val)     \
                 ^
/home/emaisin/src/binutils-gdb/binutils/dwarf.c:7866:8: note: in expansion of macro ‘READ_ULEB’
        READ_ULEB (fc->cfa_reg);
        ^
... so I also changed Frame_Chunk::cfa_reg to an unsigned int.

binutils/ChangeLog:

	* dwarf.c (struct Frame_Chunk) <cfa_reg>: Change type to
	unsigned int.
	(display_debug_frames): Read CFA reg as an unsigned number.

diff --git a/binutils/ChangeLog b/binutils/ChangeLog
index ad9d33b..8d77c68 100644 (file)
--- a/binutils/ChangeLog
+++ b/binutils/ChangeLog
@@ -1,3 +1,9 @@
+2017-10-27  Simon Marchi  <simon.marchi@ericsson.com>
+
+       * dwarf.c (struct Frame_Chunk) <cfa_reg>: Change type to
+       unsigned int.
+       (display_debug_frames): Read CFA reg as an unsigned number.
+
 2017-10-25  Alan Modra  <amodra@gmail.com>
 
        * nm.c (filter_symbols): Match "__gnu_lto_slim" optionally prefixed

diff --git a/binutils/dwarf.c b/binutils/dwarf.c
index 06702ef..873f104 100644 (file)
--- a/binutils/dwarf.c
+++ b/binutils/dwarf.c
@@ -6646,7 +6646,7 @@ typedef struct Frame_Chunk
   int data_factor;
   dwarf_vma pc_begin;
   dwarf_vma pc_range;
-  int cfa_reg;
+  unsigned int cfa_reg;
   dwarf_vma cfa_offset;
   unsigned int ra;
   unsigned char fde_encoding;
@@ -7863,7 +7863,7 @@ display_debug_frames (struct dwarf_section *section,
              break;
 
            case DW_CFA_def_cfa:
-             READ_SLEB (fc->cfa_reg);
+             READ_ULEB (fc->cfa_reg);
              READ_ULEB (fc->cfa_offset);
              fc->cfa_exp = 0;
              if (! do_debug_frames_interp)
@@ -7872,7 +7872,7 @@ display_debug_frames (struct dwarf_section *section,
              break;
 
            case DW_CFA_def_cfa_register:
-             READ_SLEB (fc->cfa_reg);
+             READ_ULEB (fc->cfa_reg);
              fc->cfa_exp = 0;
              if (! do_debug_frames_interp)
                printf ("  DW_CFA_def_cfa_register: %s\n",
@@ -7991,7 +7991,7 @@ display_debug_frames (struct dwarf_section *section,
              break;
 
            case DW_CFA_def_cfa_sf:
-             READ_SLEB (fc->cfa_reg);
+             READ_ULEB (fc->cfa_reg);
              READ_ULEB (fc->cfa_offset);
              fc->cfa_offset = fc->cfa_offset * fc->data_factor;
              fc->cfa_exp = 0;