^^&&^^

Edit File: sysc_readahead.stp

# readahead __________________________________________________
#
# asmlinkage ssize_t
# sys_readahead(int fd,
#		   loff_t offset,
#		   size_t count)
#

@define _SYSCALL_READAHEAD_NAME
%(
	name = "readahead"
%)

@define _SYSCALL_READAHEAD_ARGSTR
%(
	argstr = sprintf("%d, %d, %u", fd, offset, count)
%)

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

# dw_readahead _____________________________________________________

probe dw_syscall.readahead = kernel.function("sys_readahead").call
{
	@__syscall_gate_compat_simple
	@_SYSCALL_READAHEAD_NAME
	fd = __int32($fd)
	offset = $offset
%( CONFIG_64BIT == "y" %?
	count = $count
%:
	count = __uint32($count)
%)
	@_SYSCALL_READAHEAD_ARGSTR
}
probe dw_syscall.readahead.return = kernel.function("sys_readahead").return
{
	@__syscall_gate_compat_simple
	@_SYSCALL_READAHEAD_NAME
	@SYSC_RETVALSTR($return)
}

# nd_readahead _____________________________________________________

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

probe nd1_syscall.readahead = kprobe.function("sys_readahead") ?
{
	@__syscall_gate_compat_simple
	@_SYSCALL_READAHEAD_NAME
	asmlinkage()
	fd = int_arg(1)
%( CONFIG_64BIT == "y" %?
	offset = longlong_arg(2)
	count = ulong_arg(3)
%:
%( arch == "arm" %?
	# arm has some odd rules regarding long long arguments.
	offset = longlong_arg(3)
	count = ulong_arg(5)
%:
	# On a 32-bit kernel, 'long long' arguments take the space of
	# 2 arguments, so we have to adjust the following argument
	# numbers.
	offset = longlong_arg(2)
	count = ulong_arg(4)
%)
%)
	@_SYSCALL_READAHEAD_ARGSTR
}

/* kernel 4.17+ */
probe nd2_syscall.readahead = kprobe.function(@arch_syscall_prefix "sys_readahead") ?
{
	__set_syscall_pt_regs(pointer_arg(1))
	@_SYSCALL_READAHEAD_NAME
	fd = int_arg(1)
	offset = longlong_arg(2)
	count = ulong_arg(3)
	@_SYSCALL_READAHEAD_ARGSTR
}

/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.readahead = kernel.trace("sys_enter")
{
	__set_syscall_pt_regs($regs)
	@__syscall_gate(@const("__NR_readahead"))
	@_SYSCALL_READAHEAD_NAME
	fd = int_arg(1)
	offset = longlong_arg(2)
	count = ulong_arg(3)
	@_SYSCALL_READAHEAD_ARGSTR
}

probe nd_syscall.readahead.return = nd1_syscall.readahead.return!, nd2_syscall.readahead.return!, tp_syscall.readahead.return
  { }
  
probe nd1_syscall.readahead.return = kprobe.function("sys_readahead").return ?
{
	@__syscall_gate_compat_simple
	@_SYSCALL_READAHEAD_NAME
	@SYSC_RETVALSTR(returnval())
}

/* kernel 4.17+ */
probe nd2_syscall.readahead.return = kprobe.function(@arch_syscall_prefix "sys_readahead").return ?
{
	@_SYSCALL_READAHEAD_NAME
	@SYSC_RETVALSTR(returnval())
}
 
/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.readahead.return = kernel.trace("sys_exit")
{
	__set_syscall_pt_regs($regs)
	@__syscall_gate(@const("__NR_readahead"))
	@_SYSCALL_READAHEAD_NAME
	@SYSC_RETVALSTR($ret)
}