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authorCary Coutant <ccoutant@gmail.com>2018-04-24 21:57:37 -0700
committerCary Coutant <ccoutant@gmail.com>2018-04-24 22:13:56 -0700
commit651d16203867f8013a0f78a2f2e24df8c02d1377 (patch)
tree80412e416cf3ffc70a81030fb558eae8f233dda0 /gold/icf.cc
parent2ac93be706418f3b2aebeb22159a328023faed52 (diff)
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Fix bug with relocation addends and merge sections with --icf.
During --icf processing, gold was incorrectly processing the relocation addend for references to items in a merge section. PC-relative references and other forms of reference with a biased base address require a non-section local symbol, where the addend is purely the bias. gold/ PR gold/20642 PR gold/22820 * gc.h (gc_process_relocs): Flag STT_SECTION symbols in symvec. * icf.cc (get_section_contents): For merge sections, ignore the addend for relocations against non-section symbols.
Diffstat (limited to 'gold/icf.cc')
-rw-r--r--gold/icf.cc84
1 files changed, 54 insertions, 30 deletions
diff --git a/gold/icf.cc b/gold/icf.cc
index 62dade8..378a56b 100644
--- a/gold/icf.cc
+++ b/gold/icf.cc
@@ -327,6 +327,16 @@ get_section_contents(bool first_iteration,
for (; it_v != v.end(); ++it_v, ++it_s, ++it_a, ++it_o, ++it_addend_size)
{
+ Symbol* gsym = *it_s;
+ bool is_section_symbol = false;
+
+ // A -1 value in the symbol vector indicates a local section symbol.
+ if (gsym == reinterpret_cast<Symbol*>(-1))
+ {
+ is_section_symbol = true;
+ gsym = NULL;
+ }
+
if (first_iteration
&& it_v->first != NULL)
{
@@ -354,7 +364,7 @@ get_section_contents(bool first_iteration,
// It would be nice if we could use format macros in inttypes.h
// here but there are not in ISO/IEC C++ 1998.
- snprintf(addend_str, sizeof(addend_str), "%llx %llx %llux",
+ snprintf(addend_str, sizeof(addend_str), "%llx %llx %llx",
static_cast<long long>((*it_a).first),
static_cast<long long>((*it_a).second),
static_cast<unsigned long long>(*it_o));
@@ -367,8 +377,8 @@ get_section_contents(bool first_iteration,
if (first_iteration)
{
// If the symbol name is available, use it.
- if ((*it_s) != NULL)
- buffer.append((*it_s)->name());
+ if (gsym != NULL)
+ buffer.append(gsym->name());
// Append the addend.
buffer.append(addend_str);
buffer.append("@");
@@ -395,10 +405,10 @@ get_section_contents(bool first_iteration,
symtab->icf()->section_to_int_map();
Icf::Uniq_secn_id_map::iterator section_id_map_it =
section_id_map.find(reloc_secn);
- bool is_sym_preemptible = (*it_s != NULL
- && !(*it_s)->is_from_dynobj()
- && !(*it_s)->is_undefined()
- && (*it_s)->is_preemptible());
+ bool is_sym_preemptible = (gsym != NULL
+ && !gsym->is_from_dynobj()
+ && !gsym->is_undefined()
+ && gsym->is_preemptible());
if (!is_sym_preemptible
&& section_id_map_it != section_id_map.end())
{
@@ -436,27 +446,41 @@ get_section_contents(bool first_iteration,
uint64_t entsize =
(it_v->first)->section_entsize(it_v->second);
long long offset = it_a->first;
- // Handle SHT_RELA and SHT_REL addends, only one of these
- // addends exists.
- // Get the SHT_RELA addend. For RELA relocations, we have
- // the addend from the relocation.
- uint64_t reloc_addend_value = it_a->second;
-
- // Handle SHT_REL addends.
- // For REL relocations, we need to fetch the addend from the
- // section contents.
- const unsigned char* reloc_addend_ptr =
- contents + static_cast<unsigned long long>(*it_o);
-
- // Update the addend value with the SHT_REL addend if
- // available.
- get_rel_addend(reloc_addend_ptr, *it_addend_size,
- &reloc_addend_value);
-
- // Ignore the addend when it is a negative value. See the
- // comments in Merged_symbol_value::value in object.h.
- if (reloc_addend_value < 0xffffff00)
- offset = offset + reloc_addend_value;
+
+ // Handle SHT_RELA and SHT_REL addends. Only one of these
+ // addends exists. When pointing to a merge section, the
+ // addend only matters if it's relative to a section
+ // symbol. In order to unambiguously identify the target
+ // of the relocation, the compiler (and assembler) must use
+ // a local non-section symbol unless Symbol+Addend does in
+ // fact point directly to the target. (In other words,
+ // a bias for a pc-relative reference or a non-zero based
+ // access forces the use of a local symbol, and the addend
+ // is used only to provide that bias.)
+ uint64_t reloc_addend_value = 0;
+ if (is_section_symbol)
+ {
+ // Get the SHT_RELA addend. For RELA relocations,
+ // we have the addend from the relocation.
+ reloc_addend_value = it_a->second;
+
+ // Handle SHT_REL addends.
+ // For REL relocations, we need to fetch the addend
+ // from the section contents.
+ const unsigned char* reloc_addend_ptr =
+ contents + static_cast<unsigned long long>(*it_o);
+
+ // Update the addend value with the SHT_REL addend if
+ // available.
+ get_rel_addend(reloc_addend_ptr, *it_addend_size,
+ &reloc_addend_value);
+
+ // Ignore the addend when it is a negative value.
+ // See the comments in Merged_symbol_value::value
+ // in object.h.
+ if (reloc_addend_value < 0xffffff00)
+ offset = offset + reloc_addend_value;
+ }
section_size_type secn_len;
@@ -517,10 +541,10 @@ get_section_contents(bool first_iteration,
}
buffer.append("@");
}
- else if ((*it_s) != NULL)
+ else if (gsym != NULL)
{
// If symbol name is available use that.
- buffer.append((*it_s)->name());
+ buffer.append(gsym->name());
// Append the addend.
buffer.append(addend_str);
buffer.append("@");