• Nathan Lynch's avatar
    ARM: 8384/1: VDSO: force use of BFD linker · d2b30cd4
    Nathan Lynch authored
    When using a toolchain with gold as the default linker, the VDSO build
    fails:
    
      VDSO    arch/arm/vdso/vdso.so.raw
      HOSTCC  arch/arm/vdso/vdsomunge
      MUNGE   arch/arm/vdso/vdso.so.dbg
      OBJCOPY arch/arm/vdso/vdso.so
    BFD: arch/arm/vdso/vdso.so: Not enough room for program headers, try
    linking with -N
    
    For whatever reason, ld.gold is omitting an exidx program header that
    ld.bfd emits, and even when I work around that, I don't get a working
    VDSO.
    
    For now, instead of supporting gold (which will fail to link the
    kernel anyway since it does not implement --pic-veneer), direct the
    compiler to use the traditional bfd linker.  This is accomplished by
    using -fuse-ld, which is implemented in GCC 4.8 and later.
    
    Note: one limitation of this is that if the toolchain is configured
    to use gold by default, and the bfd linker is not in $PATH, the VDSO
    build will fail:
    
      VDSO    arch/arm/vdso/vdso.so.raw
    collect2: fatal error: cannot find 'ld'
    
    This will happen if CROSS_COMPILE begins with a path such as
    /opt/bin/arm-linux-gnu- but /opt/bin is not in $PATH.  This is
    considered an acceptable corner-case limitation and is easily worked
    around.
    
    Additonal note: we use cc-option instead of cc-ldoption so that
    -fuse-ld=bfd is placed in the command line if the compiler recognizes
    the option.  Using cc-ldoption results in an attempt to link, which
    fails in the situation just described, causing -fuse-ld=bfd to be
    omitted and gold to be used for the VDSO link, which is what we're
    trying to prevent.
    Reported-by: default avatarStefan Agner <stefan@agner.ch>
    Signed-off-by: default avatarNathan Lynch <nathan_lynch@mentor.com>
    Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
    d2b30cd4
Makefile 2.3 KB