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Re: GNU attribute output on errors
On Thu, Jul 05, 2018 at 10:43:43AM -0400, Carlos O'Donell wrote:
> I don't suggest warning by default on the missing tag, but let me reiterate
> again my position:
>
> (1) gcc should always emit the tag.
>
> (2) we should have the capability to warn if the tag is missing.
That's not too unreasonable. ;-) I'll worry about (2) after (1)
happens. Right now there are more pressing linker issues. I
discovered today that PowerPC gold currently ignores
.gnu.attributes. First pass at the support attached.
--
Alan Modra
Australia Development Lab, IBM
>From 77ff74442fb949cdf5e01f733f936bf64d2509c4 Mon Sep 17 00:00:00 2001
From: Alan Modra <amodra@gmail.com>
Date: Fri, 6 Jul 2018 01:08:16 +0930
Subject: [PATCH] [GOLD] PowerPC .gnu.attributes support
diff --git a/elfcpp/powerpc.h b/elfcpp/powerpc.h
index 71de45970f..5996691602 100644
--- a/elfcpp/powerpc.h
+++ b/elfcpp/powerpc.h
@@ -230,6 +230,32 @@ enum
EF_PPC64_ABI = 3
};
+// Object attribute tags. 0-3 are generic.
+enum
+{
+ // FP ABI, low 2 bits:
+ // 1 for double precision hard-float,
+ // 2 for soft-float,
+ // 3 for single precision hard-float.
+ // 0 for not tagged or not using any ABIs affected by the differences.
+ // Next 2 bits:
+ // 1 for ibm long double
+ // 2 for 64-bit long double
+ // 3 for IEEE long double.
+ // 0 for not tagged or not using any ABIs affected by the differences.
+ Tag_GNU_Power_ABI_FP = 4,
+
+ // Value 1 for general purpose registers only, 2 for AltiVec
+ // registers, 3 for SPE registers; 0 for not tagged or not using any
+ // ABIs affected by the differences.
+ Tag_GNU_Power_ABI_Vector = 8,
+
+ // Value 1 for ABIs using r3/r4 for returning structures <= 8 bytes,
+ // 2 for ABIs using memory; 0 for not tagged or not using any ABIs
+ // affected by the differences.
+ Tag_GNU_Power_ABI_Struct_Return = 12
+};
+
// DT_PPC_OPT bits
enum
{
diff --git a/gold/powerpc.cc b/gold/powerpc.cc
index 314eaa7e56..ae4127bd5a 100644
--- a/gold/powerpc.cc
+++ b/gold/powerpc.cc
@@ -41,6 +41,7 @@
#include "tls.h"
#include "errors.h"
#include "gc.h"
+#include "attributes.h"
namespace
{
@@ -100,13 +101,14 @@ public:
uniq_(object_id++), special_(0), relatoc_(0), toc_(0),
has_small_toc_reloc_(false), opd_valid_(false),
e_flags_(ehdr.get_e_flags()), no_toc_opt_(), opd_ent_(),
- access_from_map_(), has14_(), stub_table_index_(), st_other_()
+ access_from_map_(), has14_(), stub_table_index_(), st_other_(),
+ attributes_section_data_(NULL)
{
this->set_abiversion(0);
}
~Powerpc_relobj()
- { }
+ { delete this->attributes_section_data_; }
// Read the symbols then set up st_other vector.
void
@@ -388,6 +390,11 @@ public:
ppc64_local_entry_offset(unsigned int symndx) const
{ return elfcpp::ppc64_decode_local_entry(this->st_other_[symndx] >> 5); }
+ // The contents of the .gnu.attributes section if there is one.
+ const Attributes_section_data*
+ attributes_section_data() const
+ { return this->attributes_section_data_; }
+
private:
struct Opd_ent
{
@@ -458,6 +465,9 @@ private:
// ELF st_other field for local symbols.
std::vector<unsigned char> st_other_;
+
+ // Object attributes if there is a .gnu.attributes section.
+ Attributes_section_data* attributes_section_data_;
};
template<int size, bool big_endian>
@@ -469,13 +479,14 @@ public:
Powerpc_dynobj(const std::string& name, Input_file* input_file, off_t offset,
const typename elfcpp::Ehdr<size, big_endian>& ehdr)
: Sized_dynobj<size, big_endian>(name, input_file, offset, ehdr),
- opd_shndx_(0), e_flags_(ehdr.get_e_flags()), opd_ent_()
+ opd_shndx_(0), e_flags_(ehdr.get_e_flags()), opd_ent_(),
+ attributes_section_data_(NULL)
{
this->set_abiversion(0);
}
~Powerpc_dynobj()
- { }
+ { delete this->attributes_section_data_; }
// Call Sized_dynobj::do_read_symbols to read the symbols then
// read .opd from a dynamic object, filling in opd_ent_ vector,
@@ -534,6 +545,11 @@ public:
void
set_abiversion(int ver);
+ // The contents of the .gnu.attributes section if there is one.
+ const Attributes_section_data*
+ attributes_section_data() const
+ { return this->attributes_section_data_; }
+
private:
// Used to specify extent of executable sections.
struct Sec_info
@@ -574,6 +590,9 @@ private:
// corresponding to the address. Note that in dynamic objects,
// offset is *not* relative to the section.
std::vector<Opd_ent> opd_ent_;
+
+ // Object attributes if there is a .gnu.attributes section.
+ Attributes_section_data* attributes_section_data_;
};
// Powerpc_copy_relocs class. Needed to peek at dynamic relocs the
@@ -618,7 +637,9 @@ class Target_powerpc : public Sized_target<size, big_endian>
has_tls_get_addr_opt_(false),
relax_failed_(false), relax_fail_count_(0),
stub_group_size_(0), savres_section_(0),
- tls_get_addr_(NULL), tls_get_addr_opt_(NULL)
+ tls_get_addr_(NULL), tls_get_addr_opt_(NULL),
+ attributes_section_data_(NULL),
+ last_fp_(NULL), last_ld_(NULL), last_vec_(NULL), last_struct_(NULL)
{
}
@@ -1156,6 +1177,10 @@ class Target_powerpc : public Sized_target<size, big_endian>
stk_linker() const
{ return this->abiversion() < 2 ? 32 : 8; }
+ // Merge object attributes from input object with those in the output.
+ void
+ merge_object_attributes(const char*, const Attributes_section_data*);
+
private:
class Track_tls
@@ -1647,6 +1672,15 @@ class Target_powerpc : public Sized_target<size, big_endian>
Symbol* tls_get_addr_;
// If optimizing __tls_get_addr calls, the "__tls_get_addr_opt" symbol.
Symbol* tls_get_addr_opt_;
+
+ // Attributes in output.
+ Attributes_section_data* attributes_section_data_;
+
+ // Last input file to change various attribute tags
+ const char* last_fp_;
+ const char* last_ld_;
+ const char* last_vec_;
+ const char* last_struct_;
};
template<>
@@ -2312,6 +2346,8 @@ void
Powerpc_relobj<size, big_endian>::do_read_symbols(Read_symbols_data* sd)
{
this->base_read_symbols(sd);
+ if (this->input_file()->format() != Input_file::FORMAT_ELF)
+ return;
if (size == 64)
{
const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
@@ -2345,6 +2381,56 @@ Powerpc_relobj<size, big_endian>::do_read_symbols(Read_symbols_data* sd)
}
}
}
+
+ const size_t shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
+ const unsigned char* ps = sd->section_headers->data() + shdr_size;
+ bool merge_attributes = false;
+ for (unsigned int i = 1; i < this->shnum(); ++i, ps += shdr_size)
+ {
+ elfcpp::Shdr<size, big_endian> shdr(ps);
+ switch (shdr.get_sh_type())
+ {
+ case elfcpp::SHT_GNU_ATTRIBUTES:
+ {
+ gold_assert(this->attributes_section_data_ == NULL);
+ section_offset_type section_offset = shdr.get_sh_offset();
+ section_size_type section_size =
+ convert_to_section_size_type(shdr.get_sh_size());
+ const unsigned char* view =
+ this->get_view(section_offset, section_size, true, false);
+ this->attributes_section_data_ =
+ new Attributes_section_data(view, section_size);
+ }
+ break;
+
+ case elfcpp::SHT_SYMTAB:
+ {
+ // Sometimes an object has no contents except the section
+ // name string table and an empty symbol table with the
+ // undefined symbol. We don't want to merge
+ // processor-specific flags from such an object.
+ const typename elfcpp::Elf_types<size>::Elf_WXword sym_size =
+ elfcpp::Elf_sizes<size>::sym_size;
+ if (shdr.get_sh_size() > sym_size)
+ merge_attributes = true;
+ }
+ break;
+
+ case elfcpp::SHT_STRTAB:
+ break;
+
+ default:
+ merge_attributes = true;
+ break;
+ }
+ }
+
+ if (!merge_attributes)
+ {
+ // Should rarely happen.
+ delete this->attributes_section_data_;
+ this->attributes_section_data_ = NULL;
+ }
}
template<int size, bool big_endian>
@@ -2376,9 +2462,26 @@ void
Powerpc_dynobj<size, big_endian>::do_read_symbols(Read_symbols_data* sd)
{
this->base_read_symbols(sd);
+ const size_t shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
+ const unsigned char* ps =
+ sd->section_headers->data() + shdr_size * (this->shnum() - 1);
+ for (unsigned int i = this->shnum(); i > 0; --i, ps -= shdr_size)
+ {
+ elfcpp::Shdr<size, big_endian> shdr(ps);
+ if (shdr.get_sh_type() == elfcpp::SHT_GNU_ATTRIBUTES)
+ {
+ section_offset_type section_offset = shdr.get_sh_offset();
+ section_size_type section_size =
+ convert_to_section_size_type(shdr.get_sh_size());
+ const unsigned char* view =
+ this->get_view(section_offset, section_size, true, false);
+ this->attributes_section_data_ =
+ new Attributes_section_data(view, section_size);
+ break;
+ }
+ }
if (size == 64)
{
- const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
const unsigned char* const pshdrs = sd->section_headers->data();
const unsigned char* namesu = sd->section_names->data();
const char* names = reinterpret_cast<const char*>(namesu);
@@ -8298,7 +8401,7 @@ template<int size, bool big_endian>
void
Target_powerpc<size, big_endian>::do_finalize_sections(
Layout* layout,
- const Input_objects*,
+ const Input_objects* input_objects,
Symbol_table* symtab)
{
if (parameters->doing_static_link())
@@ -8401,6 +8504,241 @@ Target_powerpc<size, big_endian>::do_finalize_sections(
// relocs.
if (this->copy_relocs_.any_saved_relocs())
this->copy_relocs_.emit(this->rela_dyn_section(layout));
+
+ for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
+ p != input_objects->relobj_end();
+ ++p)
+ {
+ Powerpc_relobj<size, big_endian>* ppc_relobj
+ = static_cast<Powerpc_relobj<size, big_endian>*>(*p);
+ if (ppc_relobj->attributes_section_data())
+ this->merge_object_attributes(ppc_relobj->name().c_str(),
+ ppc_relobj->attributes_section_data());
+ }
+ for (Input_objects::Dynobj_iterator p = input_objects->dynobj_begin();
+ p != input_objects->dynobj_end();
+ ++p)
+ {
+ Powerpc_dynobj<size, big_endian>* ppc_dynobj
+ = static_cast<Powerpc_dynobj<size, big_endian>*>(*p);
+ if (ppc_dynobj->attributes_section_data())
+ this->merge_object_attributes(ppc_dynobj->name().c_str(),
+ ppc_dynobj->attributes_section_data());
+ }
+
+ // Create a .gnu.attributes section if we have merged any attributes
+ // from inputs.
+ if (this->attributes_section_data_ != NULL
+ && this->attributes_section_data_->size() != 0)
+ {
+ Output_attributes_section_data* attributes_section
+ = new Output_attributes_section_data(*this->attributes_section_data_);
+ layout->add_output_section_data(".gnu.attributes",
+ elfcpp::SHT_GNU_ATTRIBUTES, 0,
+ attributes_section, ORDER_INVALID, false);
+ }
+}
+
+// Merge object attributes from input file called NAME with those of the
+// output. The input object attributes are in the object pointed by PASD.
+
+template<int size, bool big_endian>
+void
+Target_powerpc<size, big_endian>::merge_object_attributes(
+ const char* name,
+ const Attributes_section_data* pasd)
+{
+ // Return if there is no attributes section data.
+ if (pasd == NULL)
+ return;
+
+ // Create output object attributes.
+ if (this->attributes_section_data_ == NULL)
+ this->attributes_section_data_ = new Attributes_section_data(NULL, 0);
+
+ const int vendor = Object_attribute::OBJ_ATTR_GNU;
+ const Object_attribute* in_attr = pasd->known_attributes(vendor);
+ Object_attribute* out_attr
+ = this->attributes_section_data_->known_attributes(vendor);
+
+ const char* err;
+ const char* first;
+ const char* second;
+ int tag = elfcpp::Tag_GNU_Power_ABI_FP;
+ int in_fp = in_attr[tag].int_value() & 0xf;
+ int out_fp = out_attr[tag].int_value() & 0xf;
+ if (in_fp != out_fp)
+ {
+ err = NULL;
+ if ((in_fp & 3) == 0)
+ ;
+ else if ((out_fp & 3) == 0)
+ {
+ out_fp |= in_fp & 3;
+ out_attr[tag].set_int_value(out_fp);
+ out_attr[tag].set_type(Object_attribute::ATTR_TYPE_FLAG_INT_VAL);
+ this->last_fp_ = name;
+ }
+ else if ((out_fp & 3) != 2 && (in_fp & 3) == 2)
+ {
+ err = N_("%s uses hard float, %s uses soft float");
+ first = this->last_fp_;
+ second = name;
+ }
+ else if ((out_fp & 3) == 2 && (in_fp & 3) != 2)
+ {
+ err = N_("%s uses hard float, %s uses soft float");
+ first = name;
+ second = this->last_fp_;
+ }
+ else if ((out_fp & 3) == 1 && (in_fp & 3) == 3)
+ {
+ err = N_("%s uses double-precision hard float, "
+ "%s uses single-precision hard float");
+ first = this->last_fp_;
+ second = name;
+ }
+ else if ((out_fp & 3) == 3 && (in_fp & 3) == 1)
+ {
+ err = N_("%s uses double-precision hard float, "
+ "%s uses single-precision hard float");
+ first = name;
+ second = this->last_fp_;
+ }
+
+ if (err || (in_fp & 0xc) == 0)
+ ;
+ else if ((out_fp & 0xc) == 0)
+ {
+ out_fp |= in_fp & 0xc;
+ out_attr[tag].set_int_value(out_fp);
+ out_attr[tag].set_type(Object_attribute::ATTR_TYPE_FLAG_INT_VAL);
+ this->last_ld_ = name;
+ }
+ else if ((out_fp & 0xc) != 2 * 4 && (in_fp & 0xc) == 2 * 4)
+ {
+ err = N_("%s uses 64-bit long double, %s uses 128-bit long double");
+ first = name;
+ second = this->last_ld_;
+ }
+ else if ((in_fp & 0xc) != 2 * 4 && (out_fp & 0xc) == 2 * 4)
+ {
+ err = N_("%s uses 64-bit long double, %s uses 128-bit long double");
+ first = this->last_ld_;
+ second = name;
+ }
+ else if ((out_fp & 0xc) == 1 * 4 && (in_fp & 0xc) == 3 * 4)
+ {
+ err = N_("%s uses IBM long double, %s uses IEEE long double");
+ first = this->last_ld_;
+ second = name;
+ }
+ else if ((out_fp & 0xc) == 3 * 4 && (in_fp & 0xc) == 1 * 4)
+ {
+ err = N_("%s uses IBM long double, %s uses IEEE long double");
+ first = name;
+ second = this->last_ld_;
+ }
+
+ if (err)
+ {
+ if (parameters->options().warn_mismatch())
+ gold_error(_(err), first, second);
+ out_attr[tag].set_type(0);
+ }
+ }
+
+ if (size == 32)
+ {
+ tag = elfcpp::Tag_GNU_Power_ABI_Vector;
+ int in_vec = in_attr[tag].int_value() & 3;
+ int out_vec = out_attr[tag].int_value() & 3;
+ if (in_vec != out_vec)
+ {
+ err = NULL;
+ if (in_vec == 0)
+ ;
+ else if (out_vec == 0)
+ {
+ out_vec = in_vec;
+ out_attr[tag].set_int_value(out_vec);
+ out_attr[tag].set_type(Object_attribute::ATTR_TYPE_FLAG_INT_VAL);
+ this->last_vec_ = name;
+ }
+ // For now, allow generic to transition to AltiVec or SPE
+ // without a warning. If GCC marked files with their stack
+ // alignment and used don't-care markings for files which are
+ // not affected by the vector ABI, we could warn about this
+ // case too. */
+ else if (in_vec == 1)
+ ;
+ else if (out_vec == 1)
+ {
+ out_vec = in_vec;
+ out_attr[tag].set_int_value(out_vec);
+ out_attr[tag].set_type(Object_attribute::ATTR_TYPE_FLAG_INT_VAL);
+ this->last_vec_ = name;
+ }
+ else if (out_vec < in_vec)
+ {
+ err = N_("%s uses AltiVec vector ABI, %s uses SPE vector ABI");
+ first = this->last_vec_;
+ second = name;
+ }
+ else if (out_vec > in_vec)
+ {
+ err = N_("%s uses AltiVec vector ABI, %s uses SPE vector ABI");
+ first = name;
+ second = this->last_vec_;
+ }
+ if (err)
+ {
+ if (parameters->options().warn_mismatch())
+ gold_error(_(err), first, second);
+ out_attr[tag].set_type(0);
+ }
+ }
+
+ tag = elfcpp::Tag_GNU_Power_ABI_Struct_Return;
+ int in_struct = in_attr[tag].int_value() & 3;
+ int out_struct = out_attr[tag].int_value() & 3;
+ if (in_struct != out_struct)
+ {
+ err = NULL;
+ if (in_struct == 0 || in_struct == 3)
+ ;
+ else if (out_struct == 0)
+ {
+ out_struct = in_struct;
+ out_attr[tag].set_int_value(out_struct);
+ out_attr[tag].set_type(Object_attribute::ATTR_TYPE_FLAG_INT_VAL);
+ this->last_struct_ = name;
+ }
+ else if (out_struct < in_struct)
+ {
+ err = N_("%s uses r3/r4 for small structure returns, "
+ "%s uses memory");
+ first = this->last_struct_;
+ second = name;
+ }
+ else if (out_struct > in_struct)
+ {
+ err = N_("%s uses r3/r4 for small structure returns, "
+ "%s uses memory");
+ first = name;
+ second = this->last_struct_;
+ }
+ if (err)
+ {
+ if (parameters->options().warn_mismatch())
+ gold_error(_(err), first, second);
+ out_attr[tag].set_type(0);
+ }
+ }
+ }
+
+ // Merge Tag_compatibility attributes and any common GNU ones.
+ this->attributes_section_data_->merge(name, pasd);
}
// Emit any saved relocs, and mark toc entries using any of these