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Re: [PATCH] gold: Get alignment of uncompressed section from ch_addralign


On Sat, Dec 01, 2018 at 05:06:59PM -0800, Cary Coutant wrote:
>               if (is_zcompressed)
>                 {
>                   // Skip over the ".zdebug" prefix.
>                   name += 7;
>                   uncompressed_size = get_uncompressed_size(contents, len);
> +                 info.addralign = shdr.get_sh_flags();
> 
> This should be shdr.get_sh_addralign().
> 
>  Object::decompressed_section_contents(
>      unsigned int shndx,
>      section_size_type* plen,
> -    bool* is_new)
> +    bool* is_new,
> +    uint64_t *palign)
> 
> Should be "uint64_t* palign".
> 
>    bool
>    section_is_compressed(unsigned int shndx,
> -                       section_size_type* uncompressed_size) const
> +                       section_size_type* uncompressed_size,
> +                       elfcpp::Elf_Xword *palign = NULL) const
> 
> Likewise.
> 
>    const unsigned char*
>    decompressed_section_contents(unsigned int shndx, section_size_type* plen,
> -                               bool* is_cached);
> +                               bool* is_cached, uint64_t *palign = NULL);
> 
> Likewise.
> 
> -cary

Like this?

H.J.
---
The ELF compression header has a field (ch_addralign) that is set to
the alignment of the uncompressed section. This way the section itself
can have a different alignment than the decompressed section.  Update
decompress_input_section to get alignment of the decompressed section
and use it when merging decompressed strings.

	PR binutils/23919
	* merge.cc (Output_merge_string<Char_type>::do_add_input_section):
	Get addralign from decompressed_section_contents.
	* object.cc (build_compressed_section_map): Set info.addralign.
	(Object::decompressed_section_contents): Add a palign
	argument and store p->second.addralign in *palign if it isn't
	NULL.
	* object.h (Compressed_section_info): Add addralign.
	(section_is_compressed): Add a palign argument, default it
	to NULL, store p->second.addralign in *palign if it isn't NULL.
	(Object::decompressed_section_contents): Likewise.
	* output.cc (Output_section::add_input_section): Get addralign
	from section_is_compressed.
---
 gold/merge.cc  |  8 +++++---
 gold/object.cc | 11 +++++++++--
 gold/object.h  |  8 ++++++--
 gold/output.cc | 11 ++++++-----
 4 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/gold/merge.cc b/gold/merge.cc
index de00ee9ae9..d7de11789f 100644
--- a/gold/merge.cc
+++ b/gold/merge.cc
@@ -440,9 +440,11 @@ Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
 {
   section_size_type sec_len;
   bool is_new;
+  uint64_t addralign = this->addralign();
   const unsigned char* pdata = object->decompressed_section_contents(shndx,
 								     &sec_len,
-								     &is_new);
+								     &is_new,
+								     &addralign);
 
   const Char_type* p = reinterpret_cast<const Char_type*>(pdata);
   const Char_type* pend = p + sec_len / sizeof(Char_type);
@@ -494,7 +496,7 @@ Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
   // aligned, so each string within the section must retain the same
   // modulo.
   uintptr_t init_align_modulo = (reinterpret_cast<uintptr_t>(pdata)
-				 & (this->addralign() - 1));
+				 & (addralign - 1));
   bool has_misaligned_strings = false;
 
   while (p < pend)
@@ -503,7 +505,7 @@ Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
 
       // Within merge input section each string must be aligned.
       if (len != 0
-	  && ((reinterpret_cast<uintptr_t>(p) & (this->addralign() - 1))
+	  && ((reinterpret_cast<uintptr_t>(p) & (addralign - 1))
 	      != init_align_modulo))
 	  has_misaligned_strings = true;
 
diff --git a/gold/object.cc b/gold/object.cc
index cbeddb9158..7930de66fe 100644
--- a/gold/object.cc
+++ b/gold/object.cc
@@ -751,11 +751,13 @@ build_compressed_section_map(
 	      const unsigned char* contents =
 		  obj->section_contents(i, &len, false);
 	      uint64_t uncompressed_size;
+	      Compressed_section_info info;
 	      if (is_zcompressed)
 		{
 		  // Skip over the ".zdebug" prefix.
 		  name += 7;
 		  uncompressed_size = get_uncompressed_size(contents, len);
+		  info.addralign = shdr.get_sh_addralign();
 		}
 	      else
 		{
@@ -763,8 +765,8 @@ build_compressed_section_map(
 		  name += 6;
 		  elfcpp::Chdr<size, big_endian> chdr(contents);
 		  uncompressed_size = chdr.get_ch_size();
+		  info.addralign = chdr.get_ch_addralign();
 		}
-	      Compressed_section_info info;
 	      info.size = convert_to_section_size_type(uncompressed_size);
 	      info.flag = shdr.get_sh_flags();
 	      info.contents = NULL;
@@ -3064,7 +3066,8 @@ const unsigned char*
 Object::decompressed_section_contents(
     unsigned int shndx,
     section_size_type* plen,
-    bool* is_new)
+    bool* is_new,
+    uint64_t* palign)
 {
   section_size_type buffer_size;
   const unsigned char* buffer = this->do_section_contents(shndx, &buffer_size,
@@ -3091,6 +3094,8 @@ Object::decompressed_section_contents(
     {
       *plen = uncompressed_size;
       *is_new = false;
+      if (palign != NULL)
+	*palign = p->second.addralign;
       return p->second.contents;
     }
 
@@ -3112,6 +3117,8 @@ Object::decompressed_section_contents(
   // once in this pass.
   *plen = uncompressed_size;
   *is_new = true;
+  if (palign != NULL)
+    *palign = p->second.addralign;
   return uncompressed_data;
 }
 
diff --git a/gold/object.h b/gold/object.h
index 0b786a5471..b99548463d 100644
--- a/gold/object.h
+++ b/gold/object.h
@@ -373,6 +373,7 @@ struct Compressed_section_info
 {
   section_size_type size;
   elfcpp::Elf_Xword flag;
+  uint64_t addralign;
   const unsigned char* contents;
 };
 typedef std::map<unsigned int, Compressed_section_info> Compressed_section_map;
@@ -808,7 +809,8 @@ class Object
 
   bool
   section_is_compressed(unsigned int shndx,
-			section_size_type* uncompressed_size) const
+			section_size_type* uncompressed_size,
+			elfcpp::Elf_Xword* palign = NULL) const
   {
     if (this->compressed_sections_ == NULL)
       return false;
@@ -818,6 +820,8 @@ class Object
       {
 	if (uncompressed_size != NULL)
 	  *uncompressed_size = p->second.size;
+	if (palign != NULL)
+	  *palign = p->second.addralign;
 	return true;
       }
     return false;
@@ -828,7 +832,7 @@ class Object
   // by the caller.
   const unsigned char*
   decompressed_section_contents(unsigned int shndx, section_size_type* plen,
-				bool* is_cached);
+				bool* is_cached, uint64_t* palign = NULL);
 
   // Discard any buffers of decompressed sections.  This is done
   // at the end of the Add_symbols task.
diff --git a/gold/output.cc b/gold/output.cc
index 8c71f0217c..24db722214 100644
--- a/gold/output.cc
+++ b/gold/output.cc
@@ -2448,7 +2448,13 @@ Output_section::add_input_section(Layout* layout,
 				  unsigned int reloc_shndx,
 				  bool have_sections_script)
 {
+  section_size_type input_section_size = shdr.get_sh_size();
+  section_size_type uncompressed_size;
   elfcpp::Elf_Xword addralign = shdr.get_sh_addralign();
+  if (object->section_is_compressed(shndx, &uncompressed_size,
+				    &addralign))
+    input_section_size = uncompressed_size;
+
   if ((addralign & (addralign - 1)) != 0)
     {
       object->error(_("invalid alignment %lu for section \"%s\""),
@@ -2498,11 +2504,6 @@ Output_section::add_input_section(Layout* layout,
 	}
     }
 
-  section_size_type input_section_size = shdr.get_sh_size();
-  section_size_type uncompressed_size;
-  if (object->section_is_compressed(shndx, &uncompressed_size))
-    input_section_size = uncompressed_size;
-
   off_t offset_in_section;
 
   if (this->has_fixed_layout())
-- 
2.19.2


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