1. 11 Nov, 2015 1 commit
    • 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