• Denys Vlasenko's avatar
    x86/asm/entry/64: Use local label to skip around sycall dispatch · a6de5a21
    Denys Vlasenko authored
    Logically, we just want to jump around the following instruction
    and its prologue/epilogue:
    
      call *sys_call_table(,%rax,8)
    
    if the syscall number is too big - we do not specifically target
    the "int_ret_from_sys_call" label.
    
    Use a local, numerical label for this jump, for more clarity.
    
    This also makes the code smaller:
    
     -ffffffff8187756b:      0f 87 0f 00 00 00       ja     ffffffff81877580 <int_ret_from_sys_call>
     +ffffffff8187756b:      77 0f                   ja     ffffffff8187757c <int_ret_from_sys_call>
    
    because jumps to global labels are never translated to short jump
    instructions by GAS.
    Signed-off-by: default avatarDenys Vlasenko <dvlasenk@redhat.com>
    Cc: Alexei Starovoitov <ast@plumgrid.com>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Will Drewry <wad@chromium.org>
    Link: http://lkml.kernel.org/r/1427821211-25099-9-git-send-email-dvlasenk@redhat.com
    [ Improved the changelog. ]
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    a6de5a21
entry_64.S 41.1 KB