A target that sets EMBEDDED non-empty is one that doesn't want to put
the ELF file header or program header in a memory image. Likely the
target isn't interested in supporting dynamically loaded executables,
shared libraries, or PIEs, because loaders for such binaries generally
require program headers to be present. This isn't 100% true though.
The target might be one where the loader accesses the file system in
order to retrieve headers.
Also, note that not all "shared libraries" require gcc -shared or the
shared library support in the linker. I believe one implementation of
shared libraries on uclinux is like this.
So, this patch removes GENERATE_SHLIB_SCRIPT and GENERATE_PIE_SCRIPT
in most emulparams files where EMBEDDED is set, restoring the shared
lib and pie support in emulparams files that unset EMBEDDED after
including a file where the support is removed.
Exceptions to the general rule that EMBEDDED disables shared libs are:
arm*-*-symbianelf*, where the OS wants shared library support
without ELF program headers in the image, and
sh*-*-uclinux*, where I've left things as they were, ie. both
EMBEDDED and GENERATE_SHLIB_SCRIPT because I'm unsure as to the
shared library scheme.
* emulparams/aarch64elf.sh (GENERATE_SHLIB_SCRIPT),
(GENERATE_PIE_SCRIPT): Don't set.
* emulparams/aarch64elf32.sh (GENERATE_SHLIB_SCRIPT),
(GENERATE_PIE_SCRIPT): Don't set.
* emulparams/arcelf.sh (GENERATE_SHLIB_SCRIPT): Don't set.
* emulparams/armelf.sh (GENERATE_SHLIB_SCRIPT),
(GENERATE_PIE_SCRIPT): Don't set.
* emulparams/armelf_fbsd.sh (GENERATE_SHLIB_SCRIPT): Set.
* emulparams/armelf_nbsd.sh (GENERATE_SHLIB_SCRIPT),
(GENERATE_PIE_SCRIPT): Set.
* emulparams/armelf_vxworks.sh (GENERATE_SHLIB_SCRIPT): Set.
* emulparams/armsymbian.sh (GENERATE_SHLIB_SCRIPT): Set.
* emulparams/elf32bfin.sh (GENERATE_SHLIB_SCRIPT): Don't set.
* emulparams/elf32microblaze.sh (GENERATE_SHLIB_SCRIPT): Don't set.
* emulparams/score3_elf.sh (GENERATE_SHLIB_SCRIPT): Don't set.
* emulparams/shelf.sh (GENERATE_SHLIB_SCRIPT): Don't set.
* emulparams/shelf_nbsd.sh (GENERATE_SHLIB_SCRIPT),
(GENERATE_PIE_SCRIPT): Set.
* emulparams/shelf_uclinux.sh (GENERATE_SHLIB_SCRIPT): Set.
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README for LD
This is the GNU linker. It is distributed with other "binary
utilities" which should be in ../binutils. See ../binutils/README for
more general notes, including where to send bug reports.
There are many features of the linker:
* The linker uses a Binary File Descriptor library (../bfd)
that it uses to read and write object files. This helps
insulate the linker itself from the format of object files.
* The linker supports a number of different object file
formats. It can even handle multiple formats at once:
Read two input formats and write a third.
* The linker can be configured for cross-linking.
* The linker supports a control language.
* There is a user manual (ld.texi), as well as the
beginnings of an internals manual (ldint.texi).
Installation
============
See ../binutils/README.
If you want to make a cross-linker, you may want to specify
a different search path of -lfoo libraries than the default.
You can do this by setting the LIB_PATH variable in ./Makefile
or using the --with-lib-path configure switch.
To build just the linker, make the target all-ld from the top level
directory (one directory above this one).
Porting to a new target
=======================
See the ldint.texi manual.
Reporting bugs etc
===========================
See ../binutils/README.
Known problems
==============
The Solaris linker normally exports all dynamic symbols from an
executable. The GNU linker does not do this by default. This is
because the GNU linker tries to present the same interface for all
similar targets (in this case, all native ELF targets). This does not
matter for normal programs, but it can make a difference for programs
which try to dlopen an executable, such as PERL or Tcl. You can make
the GNU linker export all dynamic symbols with the -E or
--export-dynamic command line option.
HP/UX 9.01 has a shell bug that causes the linker scripts to be
generated incorrectly. The symptom of this appears to be "fatal error
- scanner input buffer overflow" error messages. There are various
workarounds to this:
* Build and install bash, and build with "make SHELL=bash".
* Update to a version of HP/UX with a working shell (e.g., 9.05).
* Replace "(. ${srcdir}/scripttempl/${SCRIPT_NAME}.sc)" in
genscripts.sh with "sh ${srcdir}..." (no parens) and make sure the
emulparams script used exports any shell variables it sets.
Copyright (C) 2012-2019 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.
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