Attachment 593295 Details for Bug 834068 – Support lzma compressed .gnu_debugdata sections

[patch] Support lzma compressed .gnu_debugdata sections

0002-Support-lzma-compressed-.gnu_debugdata-sections.patch (text/plain), 7.71 KB, created by Alexander Larsson on 2012-06-20 18:31:26 UTC

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Creator: Alexander Larsson

Created: 2012-06-20 18:31:26 UTC

Size: 7.71 KB

patch

obsolete

>From fc1649874e6559a16763afabec59986e8d6ecf40 Mon Sep 17 00:00:00 2001
>From: Alexander Larsson <alexl@redhat.com>
>Date: Fri, 27 Apr 2012 11:31:52 +0200
>Subject: [PATCH 2/2] Support lzma compressed .gnu_debugdata sections
>
>In addition to normal separate debuginfo as an external file we also allow
>putting a xz compressed debuginfo file into the .gnu_debugdata section of
>the ELF file.
>
>This allows us to e.g. have a minimized debuginfo file (say one with
>only a subset of the symbols) efficiently stored in the executable file.
>---
> gdb/elfread.c |  246 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 243 insertions(+), 3 deletions(-)
>
>diff --git a/gdb/elfread.c b/gdb/elfread.c
>index 117e674..fdac6fe 100644
>--- a/gdb/elfread.c
>+++ b/gdb/elfread.c
>@@ -42,6 +42,10 @@
> #include "gdbthread.h"
> #include "regcache.h"
> #include "bcache.h"
>+#include "gdbcore.h"
>+#ifdef HAVE_LIBLZMA
>+# include <lzma.h>
>+#endif
> 
> extern void _initialize_elfread (void);
> 
>@@ -1202,6 +1206,236 @@ find_separate_debug_file_by_buildid (struct objfile *objfile)
>   return NULL;
> }
> 
>+#ifdef HAVE_LIBLZMA
>+
>+/* Custom allocator for the lzma functions so they use the gdb ones.  */
>+
>+static void *
>+alloc_lzma (void *opaque, size_t nmemb, size_t size)
>+{
>+  return xmalloc (nmemb * size);
>+}
>+
>+static void
>+free_lzma (void *opaque, void *ptr)
>+{
>+  xfree (ptr);
>+}
>+
>+static lzma_allocator gdb_lzma_allocator = { alloc_lzma, free_lzma, NULL};
>+
>+/* Custom bfd_openr_iovec implementation to read compressed data from a
>+   section. This keeps only the last decompressed block in memory to
>+   allow larger data without using to much memory.  */
>+
>+struct lzma_stream
>+{
>+  asection *section;
>+  lzma_index *index;
>+
>+  /* Currently decoded block.  */
>+  bfd_size_type data_start;
>+  bfd_size_type data_end;
>+  gdb_byte *data;
>+};
>+
>+static void *
>+lzma_open (struct bfd *nbfd,
>+	   void *open_closure)
>+{
>+  asection *section;
>+  bfd_size_type size, offset;
>+  lzma_stream_flags options;
>+  gdb_byte footer[LZMA_STREAM_HEADER_SIZE];
>+  gdb_byte *indexdata;
>+  lzma_index *index;
>+  int ret;
>+  uint64_t memlimit = UINT64_MAX;
>+  struct lzma_stream *lstream;
>+  size_t pos;
>+
>+  section = open_closure;
>+
>+  size = bfd_get_section_size (section);
>+  offset = section->filepos + size - LZMA_STREAM_HEADER_SIZE;
>+  if (bfd_seek (section->owner, offset, SEEK_SET) != 0
>+      || !bfd_bread (footer, (bfd_size_type) LZMA_STREAM_HEADER_SIZE,
>+		     section->owner)
>+      || lzma_stream_footer_decode (&options, (uint8_t *)footer))
>+    {
>+      bfd_set_error (bfd_error_wrong_format);
>+      return NULL;
>+    }
>+
>+  offset -= options.backward_size;
>+  indexdata = xmalloc (options.backward_size);
>+  index = NULL;
>+  pos = 0;
>+  if (bfd_seek (section->owner, offset, SEEK_SET) != 0
>+      || !bfd_bread (indexdata, (bfd_size_type) options.backward_size,
>+		     section->owner)
>+      || lzma_index_buffer_decode (&index, &memlimit, &gdb_lzma_allocator,
>+				   indexdata, &pos, options.backward_size)
>+      || lzma_index_size (index) != options.backward_size)
>+    {
>+      xfree (indexdata);
>+      bfd_set_error (bfd_error_wrong_format);
>+      return NULL;
>+    }
>+  xfree (indexdata);
>+
>+  lstream = xcalloc (1, sizeof (struct lzma_stream));
>+  lstream->section = section;
>+  lstream->index = index;
>+
>+  return lstream;
>+}
>+
>+static file_ptr
>+lzma_pread (struct bfd *nbfd,
>+	    void *stream,
>+	    void *buf,
>+	    file_ptr nbytes,
>+	    file_ptr offset)
>+{
>+  struct lzma_stream *lstream = stream;
>+  bfd_size_type chunk_size;
>+  lzma_index_iter iter;
>+  gdb_byte *compressed, *uncompressed;
>+  file_ptr block_offset;
>+  lzma_filter filters[LZMA_FILTERS_MAX + 1];
>+  lzma_block block;
>+  size_t compressed_pos, uncompressed_pos;
>+  file_ptr res;
>+
>+  res = 0;
>+  while (nbytes > 0)
>+    {
>+      if (lstream->data == NULL
>+	  || lstream->data_start > offset || offset >= lstream->data_end)
>+	{
>+	  asection *section = lstream->section;
>+
>+	  lzma_index_iter_init (&iter, lstream->index);
>+	  if (lzma_index_iter_locate (&iter, offset))
>+	    break;
>+
>+	  compressed = xmalloc (iter.block.total_size);
>+	  block_offset = section->filepos + iter.block.compressed_file_offset;
>+	  if (bfd_seek (section->owner, block_offset, SEEK_SET) != 0
>+	      || !bfd_bread (compressed, (bfd_size_type) iter.block.total_size,
>+			     section->owner))
>+	    {
>+	      xfree (compressed);
>+	      break;
>+	    }
>+
>+	  uncompressed = xmalloc (iter.block.uncompressed_size);
>+
>+	  memset (&block, 0, sizeof (block));
>+	  block.filters = filters;
>+	  block.header_size = lzma_block_header_size_decode(compressed[0]);
>+	  if (lzma_block_header_decode (&block, &gdb_lzma_allocator,
>+					compressed))
>+	    {
>+	      xfree (compressed);
>+	      xfree (uncompressed);
>+	      break;
>+	    }
>+
>+	  compressed_pos = block.header_size;
>+	  uncompressed_pos = 0;
>+	  if (lzma_block_buffer_decode (&block, &gdb_lzma_allocator,
>+					compressed, &compressed_pos,
>+					iter.block.total_size,
>+					uncompressed, &uncompressed_pos,
>+					iter.block.uncompressed_size))
>+	    {
>+	      xfree (compressed);
>+	      xfree (uncompressed);
>+	      break;
>+	    }
>+
>+	  xfree (compressed);
>+
>+	  xfree (lstream->data);
>+	  lstream->data = uncompressed;
>+	  lstream->data_start = iter.block.uncompressed_file_offset;
>+	  lstream->data_end =
>+	    iter.block.uncompressed_file_offset + iter.block.uncompressed_size;
>+	}
>+
>+      chunk_size = min (nbytes, lstream->data_end - offset);
>+      memcpy (buf, lstream->data + offset - lstream->data_start, chunk_size);
>+      buf = (void *)((gdb_byte *)buf + chunk_size);
>+      offset += chunk_size;
>+      nbytes -= chunk_size;
>+      res += chunk_size;
>+    }
>+
>+  return res;
>+}
>+
>+static int
>+lzma_close (struct bfd *nbfd,
>+	    void *stream)
>+{
>+  struct lzma_stream *lstream = stream;
>+
>+  lzma_index_end (lstream->index, &gdb_lzma_allocator);
>+  xfree (lstream->data);
>+  xfree (lstream);
>+  return 0;
>+}
>+
>+static int
>+lzma_stat (struct bfd *abfd,
>+	   void *stream,
>+	   struct stat *sb)
>+{
>+  struct lzma_stream *lstream = stream;
>+
>+  sb->st_size = lzma_index_uncompressed_size (lstream->index);
>+  return 0;
>+}
>+
>+/* This looks for a xz compressed separate debug info object file embedded
>+   in a section called .gnu_debugdata. If we find one we create a iovec
>+   based bfd that decompresses the object data on demand.  */
>+
>+static bfd *
>+find_separate_debug_file_in_section (struct objfile *objfile)
>+{
>+  asection *section;
>+  bfd *abfd;
>+
>+  section = bfd_get_section_by_name (objfile->obfd, ".gnu_debugdata");
>+  if (section == NULL)
>+    return NULL;
>+
>+  abfd = bfd_openr_iovec (xstrdup (objfile->name), gnutarget,
>+			  lzma_open, section,
>+			  lzma_pread, lzma_close, lzma_stat);
>+
>+  if (!bfd_check_format (abfd, bfd_object))
>+    {
>+      bfd_close (abfd);
>+      return NULL;
>+    }
>+
>+  return abfd;
>+}
>+
>+#else
>+
>+static bfd *
>+find_separate_debug_file_in_section (struct objfile *objfile)
>+{
>+  return NULL;
>+}
>+
>+#endif
>+
> /* Scan and build partial symbols for a symbol file.
>    We have been initialized by a call to elf_symfile_init, which
>    currently does nothing.
>@@ -1417,6 +1651,7 @@ elf_symfile_read (struct objfile *objfile, int symfile_flags)
>      `.note.gnu.build-id'.  */
>   else if (!objfile_has_partial_symbols (objfile))
>     {
>+      bfd *abfd = NULL;
>       char *debugfile;
> 
>       debugfile = find_separate_debug_file_by_buildid (objfile);
>@@ -1426,11 +1661,16 @@ elf_symfile_read (struct objfile *objfile, int symfile_flags)
> 
>       if (debugfile)
> 	{
>-	  bfd *abfd = symfile_bfd_open (debugfile);
>-
>-	  symbol_file_add_separate (abfd, symfile_flags, objfile);
>+	  abfd = symfile_bfd_open (debugfile);
> 	  xfree (debugfile);
> 	}
>+
>+      if (abfd == NULL)
>+	abfd = find_separate_debug_file_in_section (objfile);
>+
>+      if (abfd != NULL)
>+	symbol_file_add_separate (abfd, symfile_flags, objfile);
>+
>     }
> }
> 
>-- 
>1.7.10.2
>

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