^^&&^^

Edit File: sysc_fork.stp

# fork _______________________________________________________
#
# SYSCALL_DEFINE0(fork)
#

@define _SYSCALL_FORK_NAME
%(
	name = "fork"
%)

@define _SYSCALL_FORK_ARGSTR
%(
	argstr = ""
%)

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

# dw_fork _____________________________________________________

probe dw_syscall.fork = kernel.function("sys_fork").call ?
{
%(systemtap_v < "2.3" %?
	regs = 0
%)
%(systemtap_v < "2.5" %?
	clone_flags = 0
	stack_start = 0
	stack_size = 0
	parent_tid_uaddr = 0
	child_tid_uaddr = 0
%)
	@_SYSCALL_FORK_NAME
	@_SYSCALL_FORK_ARGSTR
}
probe dw_syscall.fork.return = kernel.function("sys_fork").return ?
{
	@_SYSCALL_FORK_NAME
	@SYSC_RETVALSTR($return)
}

# nd_fork _____________________________________________________

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

probe nd1_syscall.fork = kprobe.function("sys_fork").call ?
{
%(systemtap_v < "2.3" %?
	regs = 0
%)
%(systemtap_v < "2.5" %?
	clone_flags = 0
	stack_start = 0
	stack_size = 0
	parent_tid_uaddr = 0
	child_tid_uaddr = 0
%)
	@_SYSCALL_FORK_NAME
	@_SYSCALL_FORK_ARGSTR
}

/* kernel 4.17+ */
probe nd2_syscall.fork = kprobe.function(@arch_syscall0_prefix "sys_fork") ?
{
%(systemtap_v < "2.3" %?
	regs = 0
%)
%(systemtap_v < "2.5" %?
	clone_flags = 0
	stack_start = 0
	stack_size = 0
	parent_tid_uaddr = 0
	child_tid_uaddr = 0
%)
	@_SYSCALL_FORK_NAME
	@_SYSCALL_FORK_ARGSTR
}

/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.fork = kernel.trace("sys_enter")
{
	@__syscall_compat_gate(@const("__NR_fork"), @const("__NR_compat_fork"))
%(systemtap_v < "2.3" %?
	regs = 0
%)
%(systemtap_v < "2.5" %?
	clone_flags = 0
	stack_start = 0
	stack_size = 0
	parent_tid_uaddr = 0
	child_tid_uaddr = 0
%)
	@_SYSCALL_FORK_NAME
	@_SYSCALL_FORK_ARGSTR
}

probe nd_syscall.fork.return = nd1_syscall.fork.return!, nd2_syscall.fork.return!, tp_syscall.fork.return
  { }
  
probe nd1_syscall.fork.return = kprobe.function("sys_fork").return ?
{
	@_SYSCALL_FORK_NAME
	@SYSC_RETVALSTR(returnval())
}

/* kernel 4.17+ */
probe nd2_syscall.fork.return = kprobe.function(@arch_syscall0_prefix "sys_fork").return ?
{
	@_SYSCALL_FORK_NAME
	@SYSC_RETVALSTR(returnval())
}
 
/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.fork.return = kernel.trace("sys_exit")
{
	__set_syscall_pt_regs($regs)
	@__syscall_compat_gate(@const("__NR_fork"), @const("__NR_compat_fork"))
	@_SYSCALL_FORK_NAME
	@SYSC_RETVALSTR($ret)
}