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Filename : sysc_modify_ldt.stp
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# modify_ldt _________________________________________________
# int sys_modify_ldt(int func, void __user *ptr, unsigned long bytecount)
#

@define _SYSCALL_MODIFY_LDT_NAME
%(
	name = "modify_ldt"
%)

@define _SYSCALL_MODIFY_LDT_ARGSTR
%(
	argstr = sprintf("%d, %p, %u", func, ptr_uaddr, bytecount)
%)

@define _SYSCALL_MODIFY_LDT_REGARGS
%(
	func = int_arg(1)
	ptr_uaddr = pointer_arg(2)
	bytecount = ulong_arg(3)
%)

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

# dw_modify_ldt _____________________________________________________

probe dw_syscall.modify_ldt = kernel.function("sys_modify_ldt").call ?
{
	@_SYSCALL_MODIFY_LDT_NAME
	func = __int32($func)
	ptr_uaddr = $ptr
	bytecount = __ulong($bytecount)
	@_SYSCALL_MODIFY_LDT_ARGSTR
}
probe dw_syscall.modify_ldt.return = kernel.function("sys_modify_ldt").return ?
{
	@_SYSCALL_MODIFY_LDT_NAME
	@SYSC_RETVALSTR($return)
}

# nd_modify_ldt _____________________________________________________

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

probe nd1_syscall.modify_ldt = kprobe.function("sys_modify_ldt") ?
{
	@_SYSCALL_MODIFY_LDT_NAME
	asmlinkage()
	@_SYSCALL_MODIFY_LDT_REGARGS
	@_SYSCALL_MODIFY_LDT_ARGSTR
}

/* kernel 4.17+ */
probe nd2_syscall.modify_ldt = kprobe.function(@arch_syscall_prefix "sys_modify_ldt") ?
{
	__set_syscall_pt_regs(pointer_arg(1))
	@_SYSCALL_MODIFY_LDT_NAME
	@_SYSCALL_MODIFY_LDT_REGARGS
	@_SYSCALL_MODIFY_LDT_ARGSTR
}

/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.modify_ldt = kernel.trace("sys_enter")
{
	__set_syscall_pt_regs($regs)
	@__syscall_compat_gate(@const("__NR_modify_ldt"), @const("__NR_compat_modify_ldt"))
	@_SYSCALL_MODIFY_LDT_NAME
	@_SYSCALL_MODIFY_LDT_REGARGS
	@_SYSCALL_MODIFY_LDT_ARGSTR
}

probe nd_syscall.modify_ldt.return = nd1_syscall.modify_ldt.return!, nd2_syscall.modify_ldt.return!, tp_syscall.modify_ldt.return
  { }
  
probe nd1_syscall.modify_ldt.return = kprobe.function("sys_modify_ldt").return ?
{
	@_SYSCALL_MODIFY_LDT_NAME
	@SYSC_RETVALSTR(returnval())
}

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