[llvm-bugs] [Bug 40807] New: Don't abort printing of dynamic table if string reference is invalid

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=40807

            Bug ID: 40807
           Summary: Don't abort printing of dynamic table if string
                    reference is invalid
           Product: tools
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: llvm-readobj
          Assignee: unassignedbugs at nondot.org
          Reporter: jh7370.2008 at my.bristol.ac.uk
                CC: jh7370.2008 at my.bristol.ac.uk, llvm-bugs at lists.llvm.org

llvm-readelf, like GNU readelf, attempts to load strings from the dynamic
string table if a dyanmic tag is encountered which means an offset into that
table (e.g. DT_NEEDED), in order to print meaningful interpretation. However,
unlike GNU readelf, if that value is bogus, either because no DT_STRTAB tag
exists, or the offset is greater than DT_STRSZ, then both llvm-readobj and
llvm-readelf print an error mid-table, and stop printing the table, unlike GNU
readelf, which simply prints the hex value instead and then continues.

llvm-readelf:
DynamicSection [ (5 entries)
  Tag                Type                 Name/Value
  0x0000000000000005 STRTAB               0x1000
  0x000000000000000a STRSZ                3 (bytes)
  0x0000000000000001 NEEDED

Error reading file: Invalid dynamic string table reference.

GNU readelf:
Dynamic section at offset 0x1003 contains 5 entries:
  Tag        Type                         Name/Value
 0x0000000000000005 (STRTAB)             0x1000
 0x000000000000000a (STRSZ)              3 (bytes)
 0x0000000000000001 (NEEDED)             0x42
 0x0000000000000015 (DEBUG)              0x0
 0x0000000000000000 (NULL)               0x0

I think we can do better both than our current implementation, and than GNU's
behaviour, by printing the whole table, but indicating in the table where the
offset is an invalid offset, e.g:
DynamicSection [ (5 entries)
  Tag                Type                 Name/Value
  0x0000000000000005 STRTAB               0x1000
  0x000000000000000a STRSZ                3 (bytes)
  0x0000000000000001 NEEDED               Invalid Offset<0x42>
  0x0000000000000015 DEBUG                0x0
  0x0000000000000000 NULL                 0x0

This will aid in debugging issues in the dynamic table.

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