• Ard Biesheuvel's avatar
    arm64: module: split core and init PLT sections · 24af6c4e
    Ard Biesheuvel authored
    The arm64 module PLT code allocates all PLT entries in a single core
    section, since the overhead of having a separate init PLT section is
    not justified by the small number of PLT entries usually required for
    init code.
    
    However, the core and init module regions are allocated independently,
    and there is a corner case where the core region may be allocated from
    the VMALLOC region if the dedicated module region is exhausted, but the
    init region, being much smaller, can still be allocated from the module
    region. This leads to relocation failures if the distance between those
    regions exceeds 128 MB. (In fact, this corner case is highly unlikely to
    occur on arm64, but the issue has been observed on ARM, whose module
    region is much smaller).
    
    So split the core and init PLT regions, and name the latter ".init.plt"
    so it gets allocated along with (and sufficiently close to) the .init
    sections that it serves. Also, given that init PLT entries may need to
    be emitted for branches that target the core module, modify the logic
    that disregards defined symbols to only disregard symbols that are
    defined in the same section as the relocated branch instruction.
    
    Since there may now be two PLT entries associated with each entry in
    the symbol table, we can no longer hijack the symbol::st_size fields
    to record the addresses of PLT entries as we emit them for zero-addend
    relocations. So instead, perform an explicit comparison to check for
    duplicate entries.
    Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
    Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    24af6c4e
module.h 1.19 KB