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    • Heiko Carstens's avatar
      s390/syscalls: get rid of system call alias functions · 2213d44e
      Heiko Carstens authored
      bpftrace and friends only consider functions present in
      /sys/kernel/tracing/available_filter_functions.
      
      For system calls there is the s390 specific problem that the system call
      function itself is present via __se_sys##name() while the system call
      itself is wired up via an __s390x_sys##name() alias. The required DWARF
      debug information however is only available for the original function, not
      the alias, but within available_filter_functions only the functions with
      __s390x_ prefix are available. Which means the required DWARF debug
      information cannot be found.
      While this could be solved via tooling, it is easier to change the s390
      specific system call wrapper handling.
      
      Therefore get rid of this alias handling and implement system call wrappers
      like most other architectures are doing. In result the implementation
      generates the following functions:
      
      long __s390x_sys##name(struct pt_regs *regs)
      static inline long __se_sys##name(...)
      static inline long __do_sys##name(...)
      
      __s390x_sys##name() is the visible system call function which is also wired
      up in the system call table. Its only parameter is a pt_regs variable.
      
      This function calls the corresponding __se_sys##name() function, which has
      as many parameters like the system call definition. This function in turn
      performs all zero and sign extensions of all system call parameters, taken
      from the pt_regs structure, and finally calls __do_sys##name().
      
      __do_sys##name() is the actual inlined system call function implementation.
      
      For all 64 bit system calls there is a 31/32 bit system call function
      __s390_sys##name() generated, which handles all system call parameters
      correctly as required by compat handling. This function may be wired
      up within the compat system call table, unless there exists an
      explicit compat system call function, which is then used instead.
      Reported-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
      Tested-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
      Reviewed-by: default avatarSven Schnelle <svens@linux.ibm.com>
      Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
      2213d44e