• Paul Mackerras's avatar
    powerpc: Make the 64-bit kernel as a position-independent executable · 549e8152
    Paul Mackerras authored
    This implements CONFIG_RELOCATABLE for 64-bit by making the kernel as
    a position-independent executable (PIE) when it is set.  This involves
    processing the dynamic relocations in the image in the early stages of
    booting, even if the kernel is being run at the address it is linked at,
    since the linker does not necessarily fill in words in the image for
    which there are dynamic relocations.  (In fact the linker does fill in
    such words for 64-bit executables, though not for 32-bit executables,
    so in principle we could avoid calling relocate() entirely when we're
    running a 64-bit kernel at the linked address.)
    
    The dynamic relocations are processed by a new function relocate(addr),
    where the addr parameter is the virtual address where the image will be
    run.  In fact we call it twice; once before calling prom_init, and again
    when starting the main kernel.  This means that reloc_offset() returns
    0 in prom_init (since it has been relocated to the address it is running
    at), which necessitated a few adjustments.
    
    This also changes __va and __pa to use an equivalent definition that is
    simpler.  With the relocatable kernel, PAGE_OFFSET and MEMORY_START are
    constants (for 64-bit) whereas PHYSICAL_START is a variable (and
    KERNELBASE ideally should be too, but isn't yet).
    
    With this, relocatable kernels still copy themselves down to physical
    address 0 and run there.
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    549e8152
prom_init.c 66.7 KB