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Filename : sysc_chmod.stp
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# chmod ______________________________________________________
# long sys_chmod(const char __user * filename, mode_t mode)

@define _SYSCALL_CHMOD_NAME
%(
	name = "chmod"
%)

@define _SYSCALL_CHMOD_ARGSTR
%(
	argstr = sprintf("%s, %#o", path, mode)
%)

@define _SYSCALL_CHMOD_REGARGS
%(
	path = user_string_quoted(pointer_arg(1))
	mode = uint_arg(2)
%)

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

# dw_chmod _____________________________________________________

probe dw_syscall.chmod = kernel.function("sys_chmod").call
{
	@_SYSCALL_CHMOD_NAME
	path = user_string_quoted($filename)
%( arch == "i386" %?
	# Why @cast() here? Even though the user passes an unsigned
	# int (32-bits), some kernels (2.6.32-431.el6.i686) get an
	# unsigned short (16-bits).
	mode = @uint_cast(&$mode)
%:
	mode = __uint32($mode)
%)
	@_SYSCALL_CHMOD_ARGSTR
}
probe dw_syscall.chmod.return = kernel.function("sys_chmod").return
{
	@_SYSCALL_CHMOD_NAME
	@SYSC_RETVALSTR($return)
}

# nd_chmod _____________________________________________________

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

probe nd1_syscall.chmod = kprobe.function("sys_chmod") ?
{
	@_SYSCALL_CHMOD_NAME
	asmlinkage()
	@_SYSCALL_CHMOD_REGARGS
	@_SYSCALL_CHMOD_ARGSTR
}

/* kernel 4.17+ */
probe nd2_syscall.chmod = kprobe.function(@arch_syscall_prefix "sys_chmod") ?
{
	__set_syscall_pt_regs(pointer_arg(1))
	@_SYSCALL_CHMOD_NAME
	@_SYSCALL_CHMOD_REGARGS
	@_SYSCALL_CHMOD_ARGSTR
}

/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.chmod = kernel.trace("sys_enter")
{
	__set_syscall_pt_regs($regs)
	@__syscall_compat_gate(@const("__NR_chmod"), @const("__NR_compat_chmod"))
	@_SYSCALL_CHMOD_NAME
	@_SYSCALL_CHMOD_REGARGS
	@_SYSCALL_CHMOD_ARGSTR
}

probe nd_syscall.chmod.return = nd1_syscall.chmod.return!, nd2_syscall.chmod.return!, tp_syscall.chmod.return
  { }
  
probe nd1_syscall.chmod.return = kprobe.function("sys_chmod").return ?
{
	@_SYSCALL_CHMOD_NAME
	@SYSC_RETVALSTR(returnval())
}

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