• Nicholas Piggin's avatar
    powerpc/64: modules support building with PCREL addresing · 77e69ee7
    Nicholas Piggin authored
    Build modules using PCREL addressing when CONFIG_PPC_KERNEL_PCREL=y.
    
    - The module loader must handle several new relocation types:
    
      * R_PPC64_REL24_NOTOC is a function call handled like R_PPC_REL24, but
        does not restore r2 upon return. The external function call stub is
        changed to use pcrel addressing to load the function pointer rather
        than based on the module TOC.
    
      * R_PPC64_GOT_PCREL34 is a reference to external data. A GOT table
        must be built by hand, because the linker adds this during the final
        link (which is not done for kernel modules). The GOT table is built
        similarly to the way the external function call stub table is. This
        section is called .mygot because .got has a special meaning for the
        linker and can become upset.
    
      * R_PPC64_PCREL34 is used for local data addressing, but there is a
        special case where the percpu section is moved at load-time to the
        percpu area which is out of range of this relocation. This requires
        the PCREL34 relocations are converted to use GOT_PCREL34 addressing.
    Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
    [mpe: Some coding style & formatting fixups]
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    Link: https://msgid.link/20230408021752.862660-7-npiggin@gmail.com
    77e69ee7
ppc_asm.h 22.1 KB