The current implementation of libhugetlbfs segment remapping requires that a
binary be linked with a custom linker script that is included in the library
distribution. Over time these custom linker scripts have needed updating to
keep them compatible with changes occuring in binutils. While we've been able
to keep up in the past, we are now at an impasse. The powerpc version of
binutils has introduced a new requirement concerning the placement of the .plt
and .got sections within the binary. To achieve this special placement,
binutils-2.18 has introduced a new, backwards-incompatible linker script
keyword: SPECIAL. Based on my investigation, this keyword must be used for
reliable linking of binaries. It also cannot be used on older versions of
binutils without syntax errors. These conflicting requirements forced a
decision to be made: start supporting linker scripts for each release of
binutils, or eliminate linker scripts altogether. This patch series implements
the latter approach.
A handy option has appeared in GNU ld on 05/30/2006 and was released in
binutils 2.18. The options -z common-page-size and -z max-page-size can be
used to create a gap between the text and data segments. This gap is all that
is strictly needed to allow remapping of those segments into huge pages. Our
library has a few dependencies on the custom linker scripts that must first be
removed before the remapping strategy in elflink.c can be used to remap these
"script-less" binaries.
---
Changes since V1:
Parts of V1 have already been merged
When fixing up unaligned segments, check for collisions with other mmaps
Identify segments as read-only or writable, not as text or data
Check that remapping "plan" follows slice restrictions
HUGETLB_ELFMAP parameter overrides PF_LINUX_HUGETLB ELF flag
ld.hugetlbfs supports new parameter --hugetlbfs-align (only 1 align option)
Various comment and code cleanups
Adam Litke (4):
ld.hugetlbfs: Add support for relinking with system scripts
elflink: Consolidate parsing code
elflink: Support full segment remapping with the system linker scripts
elflink: Handle unaligned segment starting addresses
elflink.c | 214 ++++++++++++++++++++++++++++++++++++++++++++--------------
ld.hugetlbfs | 15 ++++
2 files changed, 177 insertions(+), 52 deletions(-)
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