Re: [PATCH] PR gold/18609

[Andrew Senkevich <andrew dot n dot senkevich at gmail dot com>]

2015-07-09 20:49 GMT+03:00 Cary Coutant <ccoutant@gmail.com>:
>> 2015-07-09  Andrew Senkevich  <andrew.senkevich@intel.com>
>>
>>         * gold/x86_64.cc: Added overflow check for converting
>>         R_X86_64_GOTPCREL to R_X86_64_PC32.
>
> Factor out "gold/" from the filename, add the PR number, and prefer
> present tense:
>
> gold/
>         PR gold/18609
>         * x86_64.cc: Add overflow check for converting
>         R_X86_64_GOTPCREL to R_X86_64_PC32.
>
>
>> @@ -3543,7 +3511,9 @@ Target_x86_64<size>::Relocate::relocate(
>>        // mov foo@GOTPCREL(%rip), %reg
>>        // to lea foo(%rip), %reg.
>>        // if possible.
>> -      if (rela.get_r_offset() >= 2
>> +      int64_t x = psymval->value(object, addend) - address;
>> +      if (x == static_cast<int64_t>(static_cast<int32_t>(x))
>> +         && rela.get_r_offset() >= 2
>
> Please use Bits<32>::has_overflow(x) to check for overflow (from reloc.h).

Here is corrected patch (we need to overload has_overflow() to handle x32 case):

diff --git a/gold/ChangeLog b/gold/ChangeLog
index a8c2507..7218f6f 100644
--- a/gold/ChangeLog
+++ b/gold/ChangeLog
@@ -1,3 +1,9 @@
+2015-07-14  Andrew Senkevich  <andrew.senkevich@intel.com>
+
+       PR gold/18609
+       * x86_64.cc: Overflow check for converting R_X86_64_GOTPCREL
+       to R_X86_64_PC32.
+
 2015-07-12  H.J. Lu  <hongjiu.lu@intel.com>

        PR gold/18322
diff --git a/gold/reloc.h b/gold/reloc.h
index 559206e..fd95238 100644
--- a/gold/reloc.h
+++ b/gold/reloc.h
@@ -807,6 +807,12 @@ class Bits
     return as_signed > max || as_signed < min;
   }

+  static inline bool
+  has_overflow(uint32_t val)
+  {
+    return has_overflow32(val);
+  }
+
   // Return true if VAL (stored in a uint64_t) has overflowed both a
   // signed and an unsigned value.  E.g.,
   // Bits<8>::has_signed_unsigned_overflow would check -128 <= VAL <
diff --git a/gold/x86_64.cc b/gold/x86_64.cc
index 007af1d..8f53bfc 100644
--- a/gold/x86_64.cc
+++ b/gold/x86_64.cc
@@ -2480,23 +2480,6 @@ Target_x86_64<size>::Scan::local(Symbol_table* symtab,
        // The symbol requires a GOT section.
        Output_data_got<64, false>* got = target->got_section(symtab, layout);

-       // If the relocation symbol isn't IFUNC,
-       // and is local, then we will convert
-       // mov foo@GOTPCREL(%rip), %reg
-       // to lea foo(%rip), %reg.
-       // in Relocate::relocate.
-       if (r_type == elfcpp::R_X86_64_GOTPCREL
-           && reloc.get_r_offset() >= 2
-           && !is_ifunc)
-         {
-           section_size_type stype;
-           const unsigned char* view = object->section_contents(data_shndx,
-                                                                &stype, true);
-           if (view[reloc.get_r_offset() - 2] == 0x8b)
-             break;
-         }
-
-
        // The symbol requires a GOT entry.
        unsigned int r_sym = elfcpp::elf_r_sym<size>(reloc.get_r_info());

@@ -2906,21 +2889,6 @@ Target_x86_64<size>::Scan::global(Symbol_table* symtab,
        // The symbol requires a GOT entry.
        Output_data_got<64, false>* got = target->got_section(symtab, layout);

-       // If we convert this from
-       // mov foo@GOTPCREL(%rip), %reg
-       // to lea foo(%rip), %reg.
-       // in Relocate::relocate, then there is nothing to do here.
-       if (r_type == elfcpp::R_X86_64_GOTPCREL
-           && reloc.get_r_offset() >= 2
-           && Target_x86_64<size>::can_convert_mov_to_lea(gsym))
-         {
-           section_size_type stype;
-           const unsigned char* view = object->section_contents(data_shndx,
-                                                                &stype, true);
-           if (view[reloc.get_r_offset() - 2] == 0x8b)
-             break;
-         }
-
        if (gsym->final_value_is_known())
          {
            // For a STT_GNU_IFUNC symbol we want the PLT address.
@@ -3543,7 +3511,8 @@ Target_x86_64<size>::Relocate::relocate(
       // mov foo@GOTPCREL(%rip), %reg
       // to lea foo(%rip), %reg.
       // if possible.
-      if (rela.get_r_offset() >= 2
+      if (!Bits<32>::has_overflow(psymval->value(object, addend) - address)
+         && rela.get_r_offset() >= 2
          && view[-2] == 0x8b
          && ((gsym == NULL && !psymval->is_ifunc_symbol())
              || (gsym != NULL

Is it ok?


--
WBR,
Andrew