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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.
This commit is contained in:
Simon Marchi 2017-10-27 09:01:36 -04:00
parent 7453e6b2ea
commit 32ef30002c
2 changed files with 10 additions and 4 deletions
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6
binutils/ChangeLog
View File

@ -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

8
binutils/dwarf.c
View File

@ -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;