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Filename : sysc_setuid.stp
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# setuid _____________________________________________________
#
# long sys_setuid(uid_t uid)
# long sys_setuid16(old_uid_t uid)
#

@define _SYSCALL_SETUID_NAME
%(
	name = "setuid"
%)

@define _SYSCALL_SETUID_ARGSTR
%(
	argstr = sprint(uid)
%)

@define _SYSCALL_GATE
%(
    %( arch == "x86_64" %?
	// There are actually 3 x86_64 setuid syscall numbers (which
	// get mapped to 2 syscall functions:
	//   - __NR_setuid which gets mapped to sys_setuid()
	//   - __NR_ia32_setuid32 which also gets mapped to
	//     sys_setuid() 
	//   - __NR_ia32_setuid which gets mapped to sys_setuid16()
	//     (which is a wrapper around sys_setuid())
	// So, we need to avoid sys_setuid() calls that come from
	// sys_setuid16().
	@__syscall_compat_gate(@const("__NR_setuid"),
			       @const("__NR_ia32_setuid32"))
    %:
	%( arch == "i386" %?
	    // On i386, there are 2 setuid syscall numbers:
	    //   - __NR_setuid which gets mapped to sys_setuid16
	    //   - __NR_setuid32 which gets mapped to sys_setuid
	    // Since this gets called from a probe on sys_setuid, we'll
	    // make sure this is really __NR_setuid32.
	    @__syscall_nr_gate(@const("__NR_setuid32"))
	%)
    %)
%)

@define _SYSCALL_SETUID_REGARGS
%(
	uid = int_arg(1)
%)

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

# dw_setuid _____________________________________________________

probe dw_syscall.setuid = kernel.function("sys_setuid16").call ?,
			  __syscall.setuid ?
{
	@_SYSCALL_SETUID_NAME
	uid = __int32($uid)
	@_SYSCALL_SETUID_ARGSTR
}
probe __syscall.setuid = kernel.function("sys_setuid").call ?
{
	@_SYSCALL_GATE
}
probe dw_syscall.setuid.return = kernel.function("sys_setuid16").return ?,
				 __syscall.setuid.return ?
{
	@_SYSCALL_SETUID_NAME
	@SYSC_RETVALSTR($return)
}
probe __syscall.setuid.return = kernel.function("sys_setuid").return ?
{
	@_SYSCALL_GATE
}

# nd_setuid _____________________________________________________

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

probe nd1_syscall.setuid = kprobe.function("sys_setuid16") ?,
			   __nd1_syscall.setuid ?
{
	@_SYSCALL_SETUID_NAME
	asmlinkage()
	@_SYSCALL_SETUID_REGARGS
	@_SYSCALL_SETUID_ARGSTR
}
probe __nd1_syscall.setuid = kprobe.function("sys_setuid") ?
{
	@_SYSCALL_GATE
}

/* kernel 4.17+ */
probe nd2_syscall.setuid = kprobe.function(@arch_syscall_prefix "sys_setuid") ?,
                           kprobe.function(@arch_syscall_prefix "sys_setuid16") ?
{
	__set_syscall_pt_regs(pointer_arg(1))
	@_SYSCALL_SETUID_NAME
	@_SYSCALL_SETUID_REGARGS
	@_SYSCALL_SETUID_ARGSTR
}

/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.setuid = __tp_syscall.setuid, __tp_syscall.setuid16
{
	__set_syscall_pt_regs($regs)
	@_SYSCALL_SETUID_NAME
	@_SYSCALL_SETUID_REGARGS
	@_SYSCALL_SETUID_ARGSTR
}
probe __tp_syscall.setuid = kernel.trace("sys_enter")
{
	@__syscall_compat_gate(@const("__NR_setuid"), @const("__NR_compat_setuid32"))
}
probe __tp_syscall.setuid16 = kernel.trace("sys_enter")
{
	@__compat_syscall_gate(@const("__NR_compat_setuid"))
}

probe nd_syscall.setuid.return = nd1_syscall.setuid.return!, nd2_syscall.setuid.return!, tp_syscall.setuid.return
  { }

probe nd1_syscall.setuid.return = kprobe.function("sys_setuid16").return ?,
				  __nd1_syscall.setuid.return ?
{
	@_SYSCALL_SETUID_NAME
	@SYSC_RETVALSTR(returnval())
}
probe __nd1_syscall.setuid.return = kprobe.function("sys_setuid").return ?
{
	@_SYSCALL_GATE
}

/* kernel 4.17+ */
probe nd2_syscall.setuid.return =
	kprobe.function(@arch_syscall_prefix "sys_setuid").return ?,
	kprobe.function(@arch_syscall_prefix "sys_setuid16").return ?
{
	@_SYSCALL_SETUID_NAME
	@SYSC_RETVALSTR(returnval())
}

/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.setuid.return = __tp_syscall.setuid.return, __tp_syscall.setuid16.return
{
	__set_syscall_pt_regs($regs)
	@_SYSCALL_SETUID_NAME
	@SYSC_RETVALSTR($ret)
}
probe __tp_syscall.setuid.return = kernel.trace("sys_exit")
{
	@__syscall_compat_gate(@const("__NR_setuid"), @const("__NR_compat_setuid32"))
}
probe __tp_syscall.setuid16.return = kernel.trace("sys_exit")
{
	@__compat_syscall_gate(@const("__NR_compat_setuid"))
}