• Alex Smith's avatar
    MIPS: Initial implementation of a VDSO · ebb5e78c
    Alex Smith authored
    Add an initial implementation of a proper (i.e. an ELF shared library)
    VDSO. With this commit it does not export any symbols, it only replaces
    the current signal return trampoline page. A later commit will add user
    implementations of gettimeofday()/clock_gettime().
    
    To support both new toolchains and old ones which don't generate ABI
    flags section, we define its content manually and then use a tool
    (genvdso) to patch up the section to have the correct name and type.
    genvdso also extracts symbol offsets ({,rt_}sigreturn) needed by the
    kernel, and generates a C file containing a "struct mips_vdso_image"
    containing both the VDSO data and these offsets. This C file is
    compiled into the kernel.
    
    On 64-bit kernels we require a different VDSO for each supported ABI,
    so we may build up to 3 different VDSOs. The VDSO to use is selected by
    the mips_abi structure.
    
    A kernel/user shared data page is created and mapped below the VDSO
    image. This is currently empty, but will be used by the user time
    function implementations which are added later.
    
    [markos.chandras@imgtec.com:
    - Add more comments
    - Move abi detection in genvdso.h since it's the get_symbol function
    that needs it.
    - Add an R6 specific way to calculate the base address of VDSO in order
    to avoid the branch instruction which affects performance.
    - Do not patch .gnu.attributes since it's not needed for dynamic linking.
    - Simplify Makefile a little bit.
    - checkpatch fixes
    - Restrict VDSO support for binutils < 2.25 for pre-R6
    - Include atomic64.h for O32 variant on MIPS64]
    Signed-off-by: default avatarAlex Smith <alex.smith@imgtec.com>
    Signed-off-by: default avatarMarkos Chandras <markos.chandras@imgtec.com>
    Cc: Matthew Fortune <matthew.fortune@imgtec.com>
    Cc: linux-mips@linux-mips.org
    Patchwork: https://patchwork.linux-mips.org/patch/11337/Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
    ebb5e78c
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