[PATCH] D43470: [DWARF] Prevent crash when .debug_line line_range is zero

[James Henderson via Phabricator via llvm-commits]

jhenderson created this revision.
jhenderson added reviewers: probinson, JDevlieghere, dblaikie, aprantl.

The line_range field of the .debug_line program prolog is used to calculate the meaning of special opcodes. Specifically, it is used to divide another value, which means that it cannot be 0. With this change, the prolog parser warns when a line_range of 0 is found. This will prevent llvm-dwarfdump and other tools from crashing with a divide-by-zero failure when consuming such an output.


Repository:
  rL LLVM

https://reviews.llvm.org/D43470

Files:
  lib/DebugInfo/DWARF/DWARFDebugLine.cpp
  test/tools/llvm-dwarfdump/X86/bad_line_ranges.s


Index: test/tools/llvm-dwarfdump/X86/bad_line_ranges.s
===================================================================
--- test/tools/llvm-dwarfdump/X86/bad_line_ranges.s
+++ test/tools/llvm-dwarfdump/X86/bad_line_ranges.s
@@ -0,0 +1,58 @@
+# RUN: llvm-mc %s -filetype obj -triple x86_64-pc-linux -o %t.o
+# RUN: llvm-dwarfdump -debug-line %t.o | FileCheck %s -check-prefixes=CHECK
+# RUN: FileCheck %s -check-prefix=WARN -input-file=%t.err
+# RUN: not llvm-dwarfdump -debug-line -verify %t.o 2> %t2.err | FileCheck %s -check-prefix=ERR
+# RUN: FileCheck %s -check-prefix=WARN -input-file=%t2.err
+
+# CHECK-NOT: error:
+# CHECK-NOT: warning:
+# CHECK: line_range: 0
+# CHECK-NOT: error:
+# CHECK-NOT: warning:
+
+# WARN: warning: parsing line table prologue at 0x00000000 found a line_range of value 0
+# ERR: error: .debug_line[0x00000000] was not able to be parsed for CU:
+
+.section .debug_line,"", at progbits
+
+.Lline_table_start0:
+.long .Ldebug_line_end0 - .Ldebug_line_start0 # unit_length
+.Ldebug_line_start0:
+.short 4                                      # version
+.long .Lheader_end - .Lheader_start           # header_length
+.Lheader_start:
+.byte 1                                       # minimum_instruction_length
+.byte 1                                       # maximum_operations_per_instruction
+.byte 1                                       # default_is_stmt
+.byte -5                                      # line_base
+.byte 0                                       # line_range
+.byte 13                                      # opcode_base
+.byte 0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1      # standard_opcode_lengths
+.byte 0                                       # include directories
+.byte 0                                       # file_names
+.Lheader_end:
+.byte 25 # special opcode. In order to calculate its meaning, a division by line_range is required.
+.Ldebug_line_end0:
+
+.section    .debug_info,"", at progbits
+.Lsection_info:
+.long   .Lunit_end - .Lunit_start # Length of Unit
+.Lunit_start:
+.short  4                       # DWARF version number
+.long   .Lsection_abbrev        # Offset Into Abbrev. Section
+.byte   8                       # Address Size (in bytes)
+.byte   1                       # Abbrev [1] 0xb:0x59 DW_TAG_compile_unit
+.long   .Lline_table_start0     # DW_AT_stmt_list
+.byte   0                       # End Of Children Mark
+.Lunit_end:
+
+.section    .debug_abbrev,"", at progbits
+.Lsection_abbrev:
+.byte   1                       # Abbreviation Code
+.byte   17                      # DW_TAG_compile_unit
+.byte   0                       # DW_CHILDREN_no
+.byte   16                      # DW_AT_stmt_list
+.byte   23                      # DW_FORM_sec_offset
+.byte   0                       # EOM(1)
+.byte   0                       # EOM(2)
+.byte   0                       # EOM(3)
Index: lib/DebugInfo/DWARF/DWARFDebugLine.cpp
===================================================================
--- lib/DebugInfo/DWARF/DWARFDebugLine.cpp
+++ lib/DebugInfo/DWARF/DWARFDebugLine.cpp
@@ -305,6 +305,14 @@
             PrologueOffset, EndPrologueOffset, (uint64_t)*OffsetPtr);
     return false;
   }
+
+  if (LineRange == 0) {
+    fprintf(stderr, "warning: parsing line table prologue at 0x%8.8" PRIx64
+                    " found a line_range of value 0\n",
+            PrologueOffset);
+    return false;
+  }
+
   return true;
 }
 


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