forked from Imagelibrary/binutils-gdb
8dcea93252
This patch adds -mshared option to x86 ELF assembler. By default, assembler will optimize out non-PLT relocations against defined non-weak global branch targets with default visibility. The -mshared option tells the assembler to generate code which may go into a shared library where all non-weak global branch targets with default visibility can be preempted. The resulting code is slightly bigger. This option only affects the handling of branch instructions. This Linux kernel patch is needed to create a working x86 Linux kernel if it hasn't been applied: diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index ae6588b..b91a00c 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -339,8 +339,8 @@ early_idt_handlers: i = i + 1 .endr -/* This is global to keep gas from relaxing the jumps */ -ENTRY(early_idt_handler) +/* This is weak to keep gas from relaxing the jumps */ +WEAK(early_idt_handler) cld cmpl $2,(%rsp) # X86_TRAP_NMI -- gas/ * config/tc-i386.c (shared): New. (OPTION_MSHARED): Likewise. (elf_symbol_resolved_in_segment_p): Add relocation argument. Check PLT relocations and shared. (md_estimate_size_before_relax): Pass fragP->fr_var to elf_symbol_resolved_in_segment_p. (md_longopts): Add -mshared. (md_show_usage): Likewise. (md_parse_option): Handle OPTION_MSHARED. * doc/c-i386.texi: Document -mshared. gas/testsuite/ * gas/i386/i386.exp: Don't run pcrel for ELF targets. Run pcrel-elf, relax-4 and x86-64-relax-3 for ELF targets. * gas/i386/pcrel-elf.d: New file. * gas/i386/relax-4.d: Likewise. * gas/i386/x86-64-relax-3.d: Likewise. * gas/i386/relax-3.d: Pass -mshared to assembler. Updated. * gas/i386/x86-64-relax-2.d: Likewise. * gas/i386/relax-3.s: Add test for PLT relocation.
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.