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Filename : sysc_readdir.stp
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# readdir ___________________________________________________
#
# long compat_sys_old_readdir(unsigned int fd, struct compat_old_linux_dirent __user *dirent, unsigned int count)
# int old32_readdir(unsigned int fd, struct old_linux_dirent32 *dirent, unsigned int count)
# long sys_old_readdir(unsigned int fd, struct old_linux_dirent __user *dirent, unsigned int count);
#

@define _SYSCALL_READDIR_NAME
%(
	name = "readdir"
%)

@define _SYSCALL_READDIR_ARGSTR
%(
	argstr = sprintf("%u, %p, %u", fd, dirent, count)
%)

@define _SYSCALL_READDIR_REGARGS
%(
	fd = uint_arg(1)
	dirent = pointer_arg(2)
	count = uint_arg(3)
%)

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

# dw_readdir _____________________________________________________

probe dw_syscall.readdir = kernel.function("compat_sys_old_readdir").call ?,
                        kernel.function("old32_readdir").call ?,
                        kernel.function("old_readdir").call ?,
                        kernel.function("sys_old_readdir").call ?
{
	@_SYSCALL_READDIR_NAME
	fd = __uint32($fd)
	dirent = $dirent
	count = __uint32($count)
	@_SYSCALL_READDIR_ARGSTR
}
probe dw_syscall.readdir.return = kernel.function("compat_sys_old_readdir").return ?,
                               kernel.function("old32_readdir").return ?,
                               kernel.function("old_readdir").return ?,
                               kernel.function("sys_old_readdir").return ?
{
	@_SYSCALL_READDIR_NAME
	@SYSC_RETVALSTR($return)
}

# nd_readdir _____________________________________________________

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

probe nd1_syscall.readdir = kprobe.function("compat_sys_old_readdir") ?,
                            kprobe.function("old32_readdir") ?,
                            kprobe.function("old_readdir") ?,
                            kprobe.function("sys_old_readdir").call ?
{
	@_SYSCALL_READDIR_NAME
	asmlinkage()
	@_SYSCALL_READDIR_REGARGS
	@_SYSCALL_READDIR_ARGSTR
}

/* kernel 4.17+ */
probe nd2_syscall.readdir = kprobe.function(@arch_syscall_prefix "compat_sys_old_readdir") ?
{
	__set_syscall_pt_regs(pointer_arg(1))
	@_SYSCALL_READDIR_NAME
	@_SYSCALL_READDIR_REGARGS
	@_SYSCALL_READDIR_ARGSTR
}

/* kernel 3.5+, but undesirable because it affects all syscalls */
probe tp_syscall.readdir = kernel.trace("sys_enter")
{
	__set_syscall_pt_regs($regs)
	@__syscall_compat_gate(@const("__NR_readdir"), @const("__NR_compat_readdir"))
	@_SYSCALL_READDIR_NAME
	@_SYSCALL_READDIR_REGARGS
	@_SYSCALL_READDIR_ARGSTR
}

probe nd_syscall.readdir.return = nd1_syscall.readdir.return!, nd2_syscall.readdir.return!, tp_syscall.readdir.return
  { }
  
probe nd1_syscall.readdir.return = kprobe.function("compat_sys_old_readdir").return ?,
                                   kprobe.function("old32_readdir").return ?,
                                   kprobe.function("old_readdir").return ?,
                                   kprobe.function("sys_old_readdir").return ?
{
	@_SYSCALL_READDIR_NAME
	@SYSC_RETVALSTR(returnval())
}

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