Re: [committed, PATCH] Use mmap and cache the view buffer for get_view

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Fri, Feb 6, 2015 at 9:04 AM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> This patch uses mmap if it is available and works.  It also caches the
> view buffer for get_view.  I am checking it in.
>
>
> H.J.
> ---
>         * configure.ac: Add AC_FUNC_MMAP.
>         * config.in: Regenerated.
>         * configure: Likewise.
>         * plugin.c: Include <sys/mman.h>.
>         (MAP_FAILED): New.  Defined if not defined.
>         (PROT_READ): Likewise.
>         (MAP_PRIVATE): Likewise.
>         (view_buffer_t): New.
>         (plugin_input_file_t): Add view_buffer.
>         (get_view): Try mmap and cache the view buffer.
>         (plugin_maybe_claim): Initialize view_buffer.

Offset passed to mmap must be a multiple of the page size.  This patch
aligns offset passed to mmap.  I checked it in.

* plugin.c (get_view): Align offset passed to mmap.
---
 ld/ChangeLog |  4 ++++
 ld/plugin.c  | 15 ++++++++++++---
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/ld/ChangeLog b/ld/ChangeLog
index bf59ab3..facbbc1 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,7 @@
+2015-02-10  H.J. Lu  <hongjiu.lu@intel.com>
+
+ * plugin.c (get_view): Align offset passed to mmap.
+
 2015-02-08  H.J. Lu  <hongjiu.lu@intel.com>

  * ldfile.c (ldfile_try_open_bfd): Don't call bfd_check_format
diff --git a/ld/plugin.c b/ld/plugin.c
index 5b8a7cf..3254817 100644
--- a/ld/plugin.c
+++ b/ld/plugin.c
@@ -499,6 +499,9 @@ get_view (const void *handle, const void **viewp)
   plugin_input_file_t *input = (plugin_input_file_t *) handle;
   char *buffer;
   size_t size = input->filesize;
+#if HAVE_GETPAGESIZE
+  off_t offset, bias;
+#endif

   ASSERT (called_plugin);

@@ -520,9 +523,15 @@ get_view (const void *handle, const void **viewp)
   input->view_buffer.offset = input->offset;

 #if HAVE_MMAP
-  buffer = mmap (NULL, size, PROT_READ, MAP_PRIVATE, input->fd,
- input->offset);
-  if (buffer == MAP_FAILED)
+# if HAVE_GETPAGESIZE
+  bias = input->offset % getpagesize ();;
+  offset = input->offset - bias;
+  size += bias;
+# endif
+  buffer = mmap (NULL, size, PROT_READ, MAP_PRIVATE, input->fd, offset);
+  if (buffer != MAP_FAILED)
+    buffer += bias;
+  else
 #endif
     {
       char *p;
-- 
2.1.0


-- 
H.J.