• Andreas Schwab's avatar
    m68k: Define asmlinkage_protect · 46409b7e
    Andreas Schwab authored
    commit 8474ba74193d302e8340dddd1e16c85cc4b98caf upstream.
    
    Make sure the compiler does not modify arguments of syscall functions.
    This can happen if the compiler generates a tailcall to another
    function.  For example, without asmlinkage_protect sys_openat is compiled
    into this function:
    
    sys_openat:
    	clr.l %d0
    	move.w 18(%sp),%d0
    	move.l %d0,16(%sp)
    	jbra do_sys_open
    
    Note how the fourth argument is modified in place, modifying the register
    %d4 that gets restored from this stack slot when the function returns to
    user-space.  The caller may expect the register to be unmodified across
    system calls.
    Signed-off-by: default avatarAndreas Schwab <schwab@linux-m68k.org>
    Signed-off-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    46409b7e
linkage.h 1.51 KB