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Re: [patch] Fix occasional 2MB gap in the linked binary
On Wed, 13 Aug 2008 07:13:41 +0200, Alan Modra wrote:
> I was hoping Jakub would review this change since it is his code..
> My opinion is that this would be cleaner if you just saved dot to
> min_base here, and moved all the aligning and tweaking to one place,
> in ldlang.c.
My former patch nullified/regressed the excessive VMA skip optimization:
http://www.sourceware.org/ml/binutils/2004-12/msg00152.html
The MIN_BASE value should be used in its original way. I just moved its
computing to ldlang.c.
The value I formerly computed was already stored in BASE so I reused it for
not overlapping the file offsets inside a MAXPAGE.
Regards,
Jan
2008-08-20 Jan Kratochvil <jan.kratochvil@redhat.com>
PR ld/6833
* ldexp.c (fold_binary <DATA_SEGMENT_ALIGN>): Do not align
EXPLD.DATASEG.MIN_BASE.
* ldlang.c (lang_size_sections): New variable OLD_BASE. Rename
OLD_MIN_BASE to MIN_BASE with the former alignment from `ldexp.c'.
Use OLD_BASE now for the minimal base check after the base decrease by
the maximum alignment found.
--- ld/ldexp.c 7 May 2008 14:30:41 -0000 1.74
+++ ld/ldexp.c 20 Aug 2008 13:10:57 -0000
@@ -415,7 +415,7 @@ fold_binary (etree_type *tree)
if (expld.phase == lang_allocating_phase_enum)
{
expld.dataseg.phase = exp_dataseg_align_seen;
- expld.dataseg.min_base = align_n (expld.dot, maxpage);
+ expld.dataseg.min_base = expld.dot;
expld.dataseg.base = expld.result.value;
expld.dataseg.pagesize = commonpage;
expld.dataseg.maxpagesize = maxpage;
--- ld/ldlang.c 17 Aug 2008 03:12:50 -0000 1.290
+++ ld/ldlang.c 20 Aug 2008 13:11:02 -0000
@@ -5056,17 +5056,23 @@ lang_size_sections (bfd_boolean *relax,
{
/* If DATA_SEGMENT_ALIGN DATA_SEGMENT_RELRO_END pair was seen, try
to put expld.dataseg.relro on a (common) page boundary. */
- bfd_vma old_min_base, relro_end, maxpage;
+ bfd_vma min_base, old_base, relro_end, maxpage;
expld.dataseg.phase = exp_dataseg_relro_adjust;
- old_min_base = expld.dataseg.min_base;
maxpage = expld.dataseg.maxpagesize;
+ /* MIN_BASE is the absolute minimum address we are allowed to start the
+ read-write segment (byte before will be mapped read-only). */
+ min_base = (expld.dataseg.min_base + maxpage - 1) & ~(maxpage - 1);
+ /* OLD_BASE is the address for a feasible minimum address which will
+ still not cause a data overlap inside MAXPAGE causing file offset skip
+ by MAXPAGE. */
+ old_base = expld.dataseg.base;
expld.dataseg.base += (-expld.dataseg.relro_end
& (expld.dataseg.pagesize - 1));
/* Compute the expected PT_GNU_RELRO segment end. */
relro_end = ((expld.dataseg.relro_end + expld.dataseg.pagesize - 1)
& ~(expld.dataseg.pagesize - 1));
- if (old_min_base + maxpage < expld.dataseg.base)
+ if (min_base + maxpage < expld.dataseg.base)
{
expld.dataseg.base -= maxpage;
relro_end -= maxpage;
@@ -5077,7 +5083,8 @@ lang_size_sections (bfd_boolean *relax,
{
/* The alignment of sections between DATA_SEGMENT_ALIGN
and DATA_SEGMENT_RELRO_END caused huge padding to be
- inserted at DATA_SEGMENT_RELRO_END. Try some other base. */
+ inserted at DATA_SEGMENT_RELRO_END. Try to start a bit lower so
+ that the section alignments will fit in. */
asection *sec;
unsigned int max_alignment_power = 0;
@@ -5091,8 +5098,7 @@ lang_size_sections (bfd_boolean *relax,
if (((bfd_vma) 1 << max_alignment_power) < expld.dataseg.pagesize)
{
- if (expld.dataseg.base - (1 << max_alignment_power)
- < old_min_base)
+ if (expld.dataseg.base - (1 << max_alignment_power) < old_base)
expld.dataseg.base += expld.dataseg.pagesize;
expld.dataseg.base -= (1 << max_alignment_power);
lang_reset_memory_regions ();