//! For detailed description of the ptrace requests, consult `man ptrace`.

use cfg_if::cfg_if;
use std::{mem, ptr};
use crate::Result;
use crate::errno::Errno;
use libc::{self, c_void, c_long, siginfo_t};
use crate::unistd::Pid;
use crate::sys::signal::Signal;

pub type AddressType = *mut ::libc::c_void;

#[cfg(all(
    target_os = "linux",
    any(all(target_arch = "x86_64",
            any(target_env = "gnu", target_env = "musl")),
        all(target_arch = "x86", target_env = "gnu"))
))]
use libc::user_regs_struct;

cfg_if! {
    if #[cfg(any(all(target_os = "linux", target_arch = "s390x"),
                 all(target_os = "linux", target_env = "gnu")))] {
        #[doc(hidden)]
        pub type RequestType = ::libc::c_uint;
    } else {
        #[doc(hidden)]
        pub type RequestType = ::libc::c_int;
    }
}

libc_enum!{
    #[cfg_attr(not(any(target_env = "musl", target_os = "android")), repr(u32))]
    #[cfg_attr(any(target_env = "musl", target_os = "android"), repr(i32))]
    /// Ptrace Request enum defining the action to be taken.
    #[non_exhaustive]
    pub enum Request {
        PTRACE_TRACEME,
        PTRACE_PEEKTEXT,
        PTRACE_PEEKDATA,
        PTRACE_PEEKUSER,
        PTRACE_POKETEXT,
        PTRACE_POKEDATA,
        PTRACE_POKEUSER,
        PTRACE_CONT,
        PTRACE_KILL,
        PTRACE_SINGLESTEP,
        #[cfg(any(all(target_os = "android", target_pointer_width = "32"),
                  all(target_os = "linux", any(target_env = "musl",
                                               target_arch = "mips",
                                               target_arch = "mips64",
                                               target_arch = "x86_64",
                                               target_pointer_width = "32"))))]
        PTRACE_GETREGS,
        #[cfg(any(all(target_os = "android", target_pointer_width = "32"),
                  all(target_os = "linux", any(target_env = "musl",
                                               target_arch = "mips",
                                               target_arch = "mips64",
                                               target_arch = "x86_64",
                                               target_pointer_width = "32"))))]
        PTRACE_SETREGS,
        #[cfg(any(all(target_os = "android", target_pointer_width = "32"),
                  all(target_os = "linux", any(target_env = "musl",
                                               target_arch = "mips",
                                               target_arch = "mips64",
                                               target_arch = "x86_64",
                                               target_pointer_width = "32"))))]
        PTRACE_GETFPREGS,
        #[cfg(any(all(target_os = "android", target_pointer_width = "32"),
                  all(target_os = "linux", any(target_env = "musl",
                                               target_arch = "mips",
                                               target_arch = "mips64",
                                               target_arch = "x86_64",
                                               target_pointer_width = "32"))))]
        PTRACE_SETFPREGS,
        PTRACE_ATTACH,
        PTRACE_DETACH,
        #[cfg(all(target_os = "linux", any(target_env = "musl",
                                           target_arch = "mips",
                                           target_arch = "mips64",
                                           target_arch = "x86",
                                           target_arch = "x86_64")))]
        PTRACE_GETFPXREGS,
        #[cfg(all(target_os = "linux", any(target_env = "musl",
                                           target_arch = "mips",
                                           target_arch = "mips64",
                                           target_arch = "x86",
                                           target_arch = "x86_64")))]
        PTRACE_SETFPXREGS,
        PTRACE_SYSCALL,
        PTRACE_SETOPTIONS,
        PTRACE_GETEVENTMSG,
        PTRACE_GETSIGINFO,
        PTRACE_SETSIGINFO,
        #[cfg(all(target_os = "linux", not(any(target_arch = "mips",
                                               target_arch = "mips64"))))]
        PTRACE_GETREGSET,
        #[cfg(all(target_os = "linux", not(any(target_arch = "mips",
                                               target_arch = "mips64"))))]
        PTRACE_SETREGSET,
        #[cfg(target_os = "linux")]
        PTRACE_SEIZE,
        #[cfg(target_os = "linux")]
        PTRACE_INTERRUPT,
        #[cfg(all(target_os = "linux", not(any(target_arch = "mips",
                                               target_arch = "mips64"))))]
        PTRACE_LISTEN,
        #[cfg(all(target_os = "linux", not(any(target_arch = "mips",
                                               target_arch = "mips64"))))]
        PTRACE_PEEKSIGINFO,
        #[cfg(all(target_os = "linux", target_env = "gnu",
                  any(target_arch = "x86", target_arch = "x86_64")))]
        PTRACE_SYSEMU,
        #[cfg(all(target_os = "linux", target_env = "gnu",
                  any(target_arch = "x86", target_arch = "x86_64")))]
        PTRACE_SYSEMU_SINGLESTEP,
    }
}

libc_enum!{
    #[repr(i32)]
    /// Using the ptrace options the tracer can configure the tracee to stop
    /// at certain events. This enum is used to define those events as defined
    /// in `man ptrace`.
    #[non_exhaustive]
    pub enum Event {
        /// Event that stops before a return from fork or clone.
        PTRACE_EVENT_FORK,
        /// Event that stops before a return from vfork or clone.
        PTRACE_EVENT_VFORK,
        /// Event that stops before a return from clone.
        PTRACE_EVENT_CLONE,
        /// Event that stops before a return from execve.
        PTRACE_EVENT_EXEC,
        /// Event for a return from vfork.
        PTRACE_EVENT_VFORK_DONE,
        /// Event for a stop before an exit. Unlike the waitpid Exit status program.
        /// registers can still be examined
        PTRACE_EVENT_EXIT,
        /// STop triggered by a seccomp rule on a tracee.
        PTRACE_EVENT_SECCOMP,
        // PTRACE_EVENT_STOP not provided by libc because it's defined in glibc 2.26
    }
}

libc_bitflags! {
    /// Ptrace options used in conjunction with the PTRACE_SETOPTIONS request.
    /// See `man ptrace` for more details.
    pub struct Options: libc::c_int {
        /// When delivering system call traps set a bit to allow tracer to
        /// distinguish between normal stops or syscall stops. May not work on
        /// all systems.
        PTRACE_O_TRACESYSGOOD;
        /// Stop tracee at next fork and start tracing the forked process.
        PTRACE_O_TRACEFORK;
        /// Stop tracee at next vfork call and trace the vforked process.
        PTRACE_O_TRACEVFORK;
        /// Stop tracee at next clone call and trace the cloned process.
        PTRACE_O_TRACECLONE;
        /// Stop tracee at next execve call.
        PTRACE_O_TRACEEXEC;
        /// Stop tracee at vfork completion.
        PTRACE_O_TRACEVFORKDONE;
        /// Stop tracee at next exit call. Stops before exit commences allowing
        /// tracer to see location of exit and register states.
        PTRACE_O_TRACEEXIT;
        /// Stop tracee when a SECCOMP_RET_TRACE rule is triggered. See `man seccomp` for more
        /// details.
        PTRACE_O_TRACESECCOMP;
        /// Send a SIGKILL to the tracee if the tracer exits.  This is useful
        /// for ptrace jailers to prevent tracees from escaping their control.
        #[cfg(any(target_os = "android", target_os = "linux"))]
        PTRACE_O_EXITKILL;
    }
}

fn ptrace_peek(request: Request, pid: Pid, addr: AddressType, data: *mut c_void) -> Result<c_long> {
    let ret = unsafe {
        Errno::clear();
        libc::ptrace(request as RequestType, libc::pid_t::from(pid), addr, data)
    };
    match Errno::result(ret) {
        Ok(..) | Err(Errno::UnknownErrno) => Ok(ret),
        err @ Err(..) => err,
    }
}

/// Get user registers, as with `ptrace(PTRACE_GETREGS, ...)`
#[cfg(all(
    target_os = "linux",
    any(all(target_arch = "x86_64",
            any(target_env = "gnu", target_env = "musl")),
        all(target_arch = "x86", target_env = "gnu"))
))]
pub fn getregs(pid: Pid) -> Result<user_regs_struct> {
    ptrace_get_data::<user_regs_struct>(Request::PTRACE_GETREGS, pid)
}

/// Set user registers, as with `ptrace(PTRACE_SETREGS, ...)`
#[cfg(all(
    target_os = "linux",
    any(all(target_arch = "x86_64",
            any(target_env = "gnu", target_env = "musl")),
        all(target_arch = "x86", target_env = "gnu"))
))]
pub fn setregs(pid: Pid, regs: user_regs_struct) -> Result<()> {
    let res = unsafe {
        libc::ptrace(Request::PTRACE_SETREGS as RequestType,
                     libc::pid_t::from(pid),
                     ptr::null_mut::<c_void>(),
                     &regs as *const _ as *const c_void)
    };
    Errno::result(res).map(drop)
}

/// Function for ptrace requests that return values from the data field.
/// Some ptrace get requests populate structs or larger elements than `c_long`
/// and therefore use the data field to return values. This function handles these
/// requests.
fn ptrace_get_data<T>(request: Request, pid: Pid) -> Result<T> {
    let mut data = mem::MaybeUninit::uninit();
    let res = unsafe {
        libc::ptrace(request as RequestType,
                     libc::pid_t::from(pid),
                     ptr::null_mut::<T>(),
                     data.as_mut_ptr() as *const _ as *const c_void)
    };
    Errno::result(res)?;
    Ok(unsafe{ data.assume_init() })
}

unsafe fn ptrace_other(request: Request, pid: Pid, addr: AddressType, data: *mut c_void) -> Result<c_long> {
    Errno::result(libc::ptrace(request as RequestType, libc::pid_t::from(pid), addr, data)).map(|_| 0)
}

/// Set options, as with `ptrace(PTRACE_SETOPTIONS,...)`.
pub fn setoptions(pid: Pid, options: Options) -> Result<()> {
    let res = unsafe {
        libc::ptrace(Request::PTRACE_SETOPTIONS as RequestType,
                     libc::pid_t::from(pid),
                     ptr::null_mut::<c_void>(),
                     options.bits() as *mut c_void)
    };
    Errno::result(res).map(drop)
}

/// Gets a ptrace event as described by `ptrace(PTRACE_GETEVENTMSG,...)`
pub fn getevent(pid: Pid) -> Result<c_long> {
    ptrace_get_data::<c_long>(Request::PTRACE_GETEVENTMSG, pid)
}

/// Get siginfo as with `ptrace(PTRACE_GETSIGINFO,...)`
pub fn getsiginfo(pid: Pid) -> Result<siginfo_t> {
    ptrace_get_data::<siginfo_t>(Request::PTRACE_GETSIGINFO, pid)
}

/// Set siginfo as with `ptrace(PTRACE_SETSIGINFO,...)`
pub fn setsiginfo(pid: Pid, sig: &siginfo_t) -> Result<()> {
    let ret = unsafe{
        Errno::clear();
        libc::ptrace(Request::PTRACE_SETSIGINFO as RequestType,
                     libc::pid_t::from(pid),
                     ptr::null_mut::<c_void>(),
                     sig as *const _ as *const c_void)
    };
    match Errno::result(ret) {
        Ok(_) => Ok(()),
        Err(e) => Err(e),
    }
}

/// Sets the process as traceable, as with `ptrace(PTRACE_TRACEME, ...)`
///
/// Indicates that this process is to be traced by its parent.
/// This is the only ptrace request to be issued by the tracee.
pub fn traceme() -> Result<()> {
    unsafe {
        ptrace_other(
            Request::PTRACE_TRACEME,
            Pid::from_raw(0),
            ptr::null_mut(),
            ptr::null_mut(),
        ).map(drop) // ignore the useless return value
    }
}

/// Continue execution until the next syscall, as with `ptrace(PTRACE_SYSCALL, ...)`
///
/// Arranges for the tracee to be stopped at the next entry to or exit from a system call,
/// optionally delivering a signal specified by `sig`.
pub fn syscall<T: Into<Option<Signal>>>(pid: Pid, sig: T) -> Result<()> {
    let data = match sig.into() {
        Some(s) => s as i32 as *mut c_void,
        None => ptr::null_mut(),
    };
    unsafe {
        ptrace_other(
            Request::PTRACE_SYSCALL,
            pid,
            ptr::null_mut(),
            data,
        ).map(drop) // ignore the useless return value
    }
}

/// Continue execution until the next syscall, as with `ptrace(PTRACE_SYSEMU, ...)`
///
/// In contrast to the `syscall` function, the syscall stopped at will not be executed.
/// Thus the the tracee will only be stopped once per syscall,
/// optionally delivering a signal specified by `sig`.
#[cfg(all(target_os = "linux", target_env = "gnu", any(target_arch = "x86", target_arch = "x86_64")))]
pub fn sysemu<T: Into<Option<Signal>>>(pid: Pid, sig: T) -> Result<()> {
    let data = match sig.into() {
        Some(s) => s as i32 as *mut c_void,
        None => ptr::null_mut(),
    };
    unsafe {
        ptrace_other(Request::PTRACE_SYSEMU, pid, ptr::null_mut(), data).map(drop)
        // ignore the useless return value
    }
}

/// Attach to a running process, as with `ptrace(PTRACE_ATTACH, ...)`
///
/// Attaches to the process specified by `pid`, making it a tracee of the calling process.
pub fn attach(pid: Pid) -> Result<()> {
    unsafe {
        ptrace_other(
            Request::PTRACE_ATTACH,
            pid,
            ptr::null_mut(),
            ptr::null_mut(),
        ).map(drop) // ignore the useless return value
    }
}

/// Attach to a running process, as with `ptrace(PTRACE_SEIZE, ...)`
///
/// Attaches to the process specified in pid, making it a tracee of the calling process.
#[cfg(target_os = "linux")]
pub fn seize(pid: Pid, options: Options) -> Result<()> {
    unsafe {
        ptrace_other(
            Request::PTRACE_SEIZE,
            pid,
            ptr::null_mut(),
            options.bits() as *mut c_void,
        ).map(drop) // ignore the useless return value
    }
}

/// Detaches the current running process, as with `ptrace(PTRACE_DETACH, ...)`
///
/// Detaches from the process specified by `pid` allowing it to run freely, optionally delivering a
/// signal specified by `sig`.
pub fn detach<T: Into<Option<Signal>>>(pid: Pid, sig: T) -> Result<()> {
    let data = match sig.into() {
        Some(s) => s as i32 as *mut c_void,
        None => ptr::null_mut(),
    };
    unsafe {
        ptrace_other(
            Request::PTRACE_DETACH,
            pid,
            ptr::null_mut(),
            data
        ).map(drop)
    }
}

/// Restart the stopped tracee process, as with `ptrace(PTRACE_CONT, ...)`
///
/// Continues the execution of the process with PID `pid`, optionally
/// delivering a signal specified by `sig`.
pub fn cont<T: Into<Option<Signal>>>(pid: Pid, sig: T) -> Result<()> {
    let data = match sig.into() {
        Some(s) => s as i32 as *mut c_void,
        None => ptr::null_mut(),
    };
    unsafe {
        ptrace_other(Request::PTRACE_CONT, pid, ptr::null_mut(), data).map(drop) // ignore the useless return value
    }
}

/// Stop a tracee, as with `ptrace(PTRACE_INTERRUPT, ...)`
///
/// This request is equivalent to `ptrace(PTRACE_INTERRUPT, ...)`
#[cfg(target_os = "linux")]
pub fn interrupt(pid: Pid) -> Result<()> {
    unsafe {
        ptrace_other(Request::PTRACE_INTERRUPT, pid, ptr::null_mut(), ptr::null_mut()).map(drop)
    }
}

/// Issues a kill request as with `ptrace(PTRACE_KILL, ...)`
///
/// This request is equivalent to `ptrace(PTRACE_CONT, ..., SIGKILL);`
pub fn kill(pid: Pid) -> Result<()> {
    unsafe {
        ptrace_other(Request::PTRACE_KILL, pid, ptr::null_mut(), ptr::null_mut()).map(drop)
    }
}

/// Move the stopped tracee process forward by a single step as with 
/// `ptrace(PTRACE_SINGLESTEP, ...)`
///
/// Advances the execution of the process with PID `pid` by a single step optionally delivering a
/// signal specified by `sig`.
///
/// # Example
/// ```rust
/// use nix::sys::ptrace::step;
/// use nix::unistd::Pid;
/// use nix::sys::signal::Signal; 
/// use nix::sys::wait::*;
/// fn main() {
///     // If a process changes state to the stopped state because of a SIGUSR1 
///     // signal, this will step the process forward and forward the user 
///     // signal to the stopped process
///     match waitpid(Pid::from_raw(-1), None) {
///         Ok(WaitStatus::Stopped(pid, Signal::SIGUSR1)) => {
///             let _ = step(pid, Signal::SIGUSR1);
///         }
///         _ => {},
///     }
/// }
/// ```
pub fn step<T: Into<Option<Signal>>>(pid: Pid, sig: T) -> Result<()> {
    let data = match sig.into() {
        Some(s) => s as i32 as *mut c_void,
        None => ptr::null_mut(),
    };
    unsafe {
        ptrace_other(Request::PTRACE_SINGLESTEP, pid, ptr::null_mut(), data).map(drop)
    }
}

/// Move the stopped tracee process forward by a single step or stop at the next syscall
/// as with `ptrace(PTRACE_SYSEMU_SINGLESTEP, ...)`
///
/// Advances the execution by a single step or until the next syscall.
/// In case the tracee is stopped at a syscall, the syscall will not be executed.
/// Optionally, the signal specified by `sig` is delivered to the tracee upon continuation.
#[cfg(all(target_os = "linux", target_env = "gnu", any(target_arch = "x86", target_arch = "x86_64")))]
pub fn sysemu_step<T: Into<Option<Signal>>>(pid: Pid, sig: T) -> Result<()> {
    let data = match sig.into() {
        Some(s) => s as i32 as *mut c_void,
        None => ptr::null_mut(),
    };
    unsafe {
        ptrace_other(
            Request::PTRACE_SYSEMU_SINGLESTEP,
            pid,
            ptr::null_mut(),
            data,
        )
        .map(drop) // ignore the useless return value
    }
}

/// Reads a word from a processes memory at the given address
pub fn read(pid: Pid, addr: AddressType) -> Result<c_long> {
    ptrace_peek(Request::PTRACE_PEEKDATA, pid, addr, ptr::null_mut())
}

/// Writes a word into the processes memory at the given address
///
/// # Safety
///
/// The `data` argument is passed directly to `ptrace(2)`.  Read that man page
/// for guidance.
pub unsafe fn write(
    pid: Pid,
    addr: AddressType,
    data: *mut c_void) -> Result<()>
{
    ptrace_other(Request::PTRACE_POKEDATA, pid, addr, data).map(drop)
}