Skip to content
  • Maciej W. Rozycki's avatar
    MIPS/LD: Accept high-part relocations in PIC code with absolute symbols · 3c7687b9
    Maciej W. Rozycki authored
    Accept R_MIPS_HI16, R_MIPS_HIGHER and R_MIPS_HIGHEST relocations and
    their compressed counterparts in PIC code where the symbol referred is
    absolute.  Such an operation is meaningful, because an absolute symbol
    effectively is a constant the calculation of the value of which has been
    deferred to the static link time, and which is not going to change any
    further at the dynamic load time.  Therefore there is no need ever to
    refuse the use of these relocations with such symbols, as the resulting
    run-time value observed by the program will be correct even in PIC code.
    
    This is not the case with R_MIPS_26 and its compressed counterparts,
    because the run-time value calculated by the instructions these
    relocations are used with depends on the address of the instruction
    itself, and that can change according to the base address used by the
    dynamic loader.  Therefore these relocations have to continue being
    rejected in PIC code even with absolute symbols.
    
    This allows successful linking of code that relies on previous linker
    behavior up to commit 861fb55a ("Defer allocation of R_MIPS_REL32
    GOT slots"), <https://sourceware.org/ml/binutils/2008-08/msg00096.html>,
    which introduced the problematic check missing this special exception
    for absolute symbols.
    
    	bfd/
    	* elfxx-mips.c (_bfd_mips_elf_check_relocs) <R_MIPS16_HI16>
    	<R_MIPS_HI16, R_MIPS_HIGHER, R_MIPS_HIGHEST, R_MICROMIPS_HI16>
    	<R_MICROMIPS_HIGHER, R_MICROMIPS_HIGHEST>: Also accept an
    	absolute symbol in PIC code.
    
    	ld/
    	* testsuite/ld-mips-elf/pic-reloc-0.d: New test.
    	* testsuite/ld-mips-elf/pic-reloc-1.d: New test.
    	* testsuite/ld-mips-elf/pic-reloc-2.d: New test.
    	* testsuite/ld-mips-elf/pic-reloc-3.d: New test.
    	* testsuite/ld-mips-elf/pic-reloc-4.d: New test.
    	* testsuite/ld-mips-elf/pic-reloc-absolute-hi.ld: New test
    	linker script.
    	* testsuite/ld-mips-elf/pic-reloc-absolute-lo.ld: New test
    	linker script.
    	* testsuite/ld-mips-elf/pic-reloc-ordinary.ld: New test linker
    	script.
    	* testsuite/ld-mips-elf/pic-reloc-j.s: New test source.
    	* testsuite/ld-mips-elf/pic-reloc-lui.s: New test source.
    	* testsuite/ld-mips-elf/mips-elf.exp: Run the new tests.
    3c7687b9
To find the state of this project's repository at the time of any of these versions, check out the tags.