mirror of
https://github.com/darlinghq/darling-gdb.git
synced 2025-03-04 15:37:54 +00:00
0c11728627
Fix a generic BFD issue with relocations against absolute symbols, which are installed without using any individual relocation handler provided by the backend. This causes any absolute section's addend to be lost on REL targets such as o32 MIPS, and also relocation-specific calculation adjustments are not made. As an example assembling this program: $ cat test.s .text foo: b bar b baz .set bar, 0x1234 $ as -EB -32 -o test-o32.o test.s $ as -EB -n32 -o test-n32.o test.s produces this binary code: $ objdump -dr test-o32.o test-n32.o test-o32.o: file format elf32-tradbigmips Disassembly of section .text: 00000000 <foo>: 0: 10000000 b 4 <foo+0x4> 0: R_MIPS_PC16 *ABS* 4: 00000000 nop 8: 1000ffff b 8 <foo+0x8> 8: R_MIPS_PC16 baz c: 00000000 nop test-n32.o: file format elf32-ntradbigmips Disassembly of section .text: 00000000 <foo>: 0: 10000000 b 4 <foo+0x4> 0: R_MIPS_PC16 *ABS*+0x1230 4: 00000000 nop 8: 10000000 b c <foo+0xc> 8: R_MIPS_PC16 baz-0x4 c: 00000000 nop $ where it is clearly visible in `test-o32.o', which uses REL relocations, that the absolute section's addend equivalent to the value of `bar' -- a reference to which cannot be fully resolved at the assembly time, because the reference is PC-relative -- has been lost, as has been the relocation-specific adjustment of -4, required to take into account the PC+4-relative calculation made by hardware with branches and seen in the external symbol reference to `baz' as the `ffff' addend encoded in the instruction word. In `test-n32.o', which uses RELA relocations, the absolute section's addend has been correctly retained. Give precedence then in `bfd_perform_relocation' and `bfd_install_relocation' to any individual relocation handler the backend selected may have provided, while still resorting to the generic calculation otherwise. This retains the semantics which we've had since forever or before the beginning of our repository history, and is at the very least compatible with `bfd_elf_generic_reloc' being used as the handler. Retain the `bfd_is_und_section' check unchanged at the beginning of `bfd_perform_relocation' since this does not affect the semantics of the function. The check returns the same `bfd_reloc_undefined' code the check for a null `howto' does, so swapping the two does not matter. Also the check is is mutually exclusive with the `bfd_is_abs_section' check, since a section cannot be absolute and undefined both at once, so swapping the two does not matter either. With this change applied the program quoted above now has the in-place addend correctly calculated and installed in the field being relocated: $ objdump -dr fixed-o32.o fixed-o32.o: file format elf32-tradbigmips Disassembly of section .text: 00000000 <foo>: 0: 1000048c b 1234 <bar> 0: R_MIPS_PC16 *ABS* 4: 00000000 nop 8: 1000ffff b 8 <foo+0x8> 8: R_MIPS_PC16 baz c: 00000000 nop $ Add a set of MIPS tests to cover the relevant cases, including absolute symbols with addends, and verifying that PC-relative relocations against symbols concerned resolve to the same value in the final link regardless of whether the REL or the RELA relocation form is used. Exclude linker tests though which would overflow the in-place addend on REL targets and use them as dump patterns for RELA targets only. bfd/ * reloc.c (bfd_perform_relocation): Try the `howto' handler first with relocations against absolute symbols. (bfd_install_relocation): Likewise. gas/ * testsuite/gas/mips/mips16-branch-absolute.d: Update patterns. * testsuite/gas/mips/branch-absolute.d: New test. * testsuite/gas/mips/branch-absolute-n32.d: New test. * testsuite/gas/mips/branch-absolute-n64.d: New test. * testsuite/gas/mips/branch-absolute-addend-n32.d: New test. * testsuite/gas/mips/branch-absolute-addend-n64.d: New test. * testsuite/gas/mips/mips16-branch-absolute-n32.d: New test. * testsuite/gas/mips/mips16-branch-absolute-n64.d: New test. * testsuite/gas/mips/mips16-branch-absolute-addend-n32.d: New test. * testsuite/gas/mips/mips16-branch-absolute-addend-n64.d: New test. * testsuite/gas/mips/micromips-branch-absolute.d: New test. * testsuite/gas/mips/micromips-branch-absolute-n32.d: New test. * testsuite/gas/mips/micromips-branch-absolute-n64.d: New test. * testsuite/gas/mips/micromips-branch-absolute-addend-n32.d: New test. * testsuite/gas/mips/micromips-branch-absolute-addend-n64.d: New test. * testsuite/gas/mips/branch-absolute.s: New test source. * testsuite/gas/mips/branch-absolute-addend.s: New test source. * testsuite/gas/mips/mips16-branch-absolute-addend.s: New test source. * testsuite/gas/mips/micromips-branch-absolute.s: New test source. * testsuite/gas/mips/micromips-branch-absolute-addend.s: New test source. * testsuite/gas/mips/mips.exp: Run the new tests. ld/ * testsuite/ld-mips-elf/branch-absolute.d: New test. * testsuite/ld-mips-elf/branch-absolute-n32.d: New test. * testsuite/ld-mips-elf/branch-absolute-n64.d: New test. * testsuite/ld-mips-elf/branch-absolute-addend.d: New test. * testsuite/ld-mips-elf/branch-absolute-addend-n32.d: New test. * testsuite/ld-mips-elf/branch-absolute-addend-n64.d: New test. * testsuite/ld-mips-elf/micromips-branch-absolute.d: New test. * testsuite/ld-mips-elf/micromips-branch-absolute-n32.d: New test. * testsuite/ld-mips-elf/micromips-branch-absolute-n64.d: New test. * testsuite/ld-mips-elf/micromips-branch-absolute-addend.d: New test. * testsuite/ld-mips-elf/micromips-branch-absolute-addend-n32.d: New test. * testsuite/ld-mips-elf/micromips-branch-absolute-addend-n64.d: New test. * testsuite/ld-mips-elf/mips-elf.exp: Run the new tests, except from `branch-absolute-addend' and `micromips-branch-absolute-addend', referred indirectly only.
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.