^^&&^^

Edit File: sysc_readlink.stp

# readlink ___________________________________________________
#
# long sys_readlink(const char __user * path,
#		  char __user * buf,
#		  int bufsiz)
#

@define _SYSCALL_READLINK_NAME
%(
	name = "readlink"
%)

@define _SYSCALL_READLINK_ARGSTR
%(
	argstr = sprintf("%s, %p, %d", path, buf_uaddr, bufsiz)
%)

@define _SYSCALL_READLINK_REGARGS
%(
	path = user_string_quoted(pointer_arg(1))
	buf_uaddr = pointer_arg(2)
	bufsiz = int_arg(3)
%)

probe syscall.readlink = dw_syscall.readlink !, nd_syscall.readlink ? {}
probe syscall.readlink.return = dw_syscall.readlink.return !,
                                nd_syscall.readlink.return ? {}

# dw_readlink _____________________________________________________

probe dw_syscall.readlink = kernel.function("sys_readlink").call
{
	@_SYSCALL_READLINK_NAME
	path = user_string_quoted($path)
	buf_uaddr = $buf
	bufsiz = __int32($bufsiz)
	@_SYSCALL_READLINK_ARGSTR
}
probe dw_syscall.readlink.return = kernel.function("sys_readlink").return
{
	@_SYSCALL_READLINK_NAME
	@SYSC_RETVALSTR($return)
}

# nd_readlink _____________________________________________________

probe nd_syscall.readlink = nd1_syscall.readlink!, nd2_syscall.readlink!, tp_syscall.readlink
  { }

probe nd1_syscall.readlink = kprobe.function("sys_readlink") ?
{
	@_SYSCALL_READLINK_NAME
	asmlinkage()
	@_SYSCALL_READLINK_REGARGS
	@_SYSCALL_READLINK_ARGSTR
}

/* kernel 4.17+ */
probe nd2_syscall.readlink = kprobe.function(@arch_syscall_prefix "sys_readlink") ?
{
	__set_syscall_pt_regs(pointer_arg(1))
	@_SYSCALL_READLINK_NAME
	@_SYSCALL_READLINK_REGARGS
	@_SYSCALL_READLINK_ARGSTR
}

/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.readlink = kernel.trace("sys_enter")
{
	__set_syscall_pt_regs($regs)
	@__syscall_compat_gate(@const("__NR_readlink"), @const("__NR_compat_readlink"))
	@_SYSCALL_READLINK_NAME
	@_SYSCALL_READLINK_REGARGS
	@_SYSCALL_READLINK_ARGSTR
}

probe nd_syscall.readlink.return = nd1_syscall.readlink.return!, nd2_syscall.readlink.return!, tp_syscall.readlink.return
  { }
  
probe nd1_syscall.readlink.return = kprobe.function("sys_readlink").return ?
{
	@_SYSCALL_READLINK_NAME
	@SYSC_RETVALSTR(returnval())
}

/* kernel 4.17+ */
probe nd2_syscall.readlink.return = kprobe.function(@arch_syscall_prefix "sys_readlink").return ?
{
	@_SYSCALL_READLINK_NAME
	@SYSC_RETVALSTR(returnval())
}
 
/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.readlink.return = kernel.trace("sys_exit")
{
	__set_syscall_pt_regs($regs)
	@__syscall_compat_gate(@const("__NR_readlink"), @const("__NR_compat_readlink"))
	@_SYSCALL_READLINK_NAME
	@SYSC_RETVALSTR($ret)
}