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use ax_runtime::hal::cpu::uspace::{ExceptionKind, ReturnReason, UserContext};
use ax_task::TaskInner;
use starry_process::Pid;
use starry_signal::{FPE_INTDIV, SEGV_ACCERR, SEGV_MAPERR, SignalInfo, Signo};
use starry_vm::{VmMutPtr, VmPtr};
use syscalls::Sysno;
use super::{
AsThread, SyscallRestartInfo, SyscallTraceState, TimerState, check_signals, poll_process_timer,
ptrace_stop_current, ptrace_syscall_stop_current, raise_signal_fatal, set_timer_state,
unblock_next_signal, wait_existing_ptrace_stop_current,
};
use crate::syscall::{handle_syscall, syscall_allows_signal_restart};
/// Create a new user task.
pub fn new_user_task(name: &str, mut uctx: UserContext, set_child_tid: usize) -> TaskInner {
TaskInner::new(
move || {
let curr = ax_task::current();
if let Some(tid) = (set_child_tid as *mut Pid).nullable() {
tid.vm_write(curr.as_thread().tid() as Pid).ok();
}
info!("Enter user space: ip={:#x}, sp={:#x}", uctx.ip(), uctx.sp());
let thr = curr.as_thread();
if thr.proc_data.ptrace_stop_signo_for(thr.tid()).is_some() {
wait_existing_ptrace_stop_current(thr, &mut uctx);
} else if thr.tid() == thr.proc_data.proc.pid()
&& thr.proc_data.ptrace_stop_signo().is_some()
{
let _ = ptrace_stop_current(thr, Signo::SIGSTOP, &mut uctx);
}
while !thr.pending_exit() {
let tid = thr.tid();
let is_ptraced =
thr.proc_data.is_ptrace_traceme() || thr.proc_data.is_ptrace_attached();
if thr.proc_data.is_ptrace_singlestep_for(tid) && is_ptraced {
#[cfg(any(
target_arch = "riscv64",
target_arch = "aarch64",
target_arch = "loongarch64"
))]
{
// An IRQ can return here after the stepped branch reached
// the planted breakpoint PC but before the breakpoint trap
// was delivered. Report that as the completed single-step
// instead of restoring the breakpoint and running past it.
if crate::syscall::ptrace_complete_singlestep_breakpoint_if_at_ip(
&thr.proc_data,
tid,
&mut uctx,
) && ptrace_stop_current(thr, Signo::SIGTRAP, &mut uctx).is_some()
{
continue;
}
}
crate::syscall::ptrace_setup_singlestep(&thr.proc_data, tid, &mut uctx);
}
let reason = uctx.run();
set_timer_state(&curr, TimerState::Kernel);
let saved_a0 = uctx.arg0();
let saved_sysno = uctx.sysno();
let is_syscall = matches!(reason, ReturnReason::Syscall);
match reason {
ReturnReason::Syscall => {
let tid = thr.tid();
let trace_state = thr.proc_data.take_ptrace_syscall_trace_for(tid);
if matches!(trace_state, SyscallTraceState::Entry)
&& ptrace_syscall_stop_current(thr, Signo::SIGTRAP, &mut uctx).is_some()
{
match thr.proc_data.take_ptrace_syscall_trace_for(tid) {
SyscallTraceState::Entry | SyscallTraceState::Exit => {
thr.proc_data.set_ptrace_syscall_trace_state_for(
tid,
SyscallTraceState::Exit,
)
}
SyscallTraceState::None => {}
}
}
if let Some(exit_code) = ptrace_exit_event_code(saved_sysno, saved_a0)
&& crate::syscall::ptrace_notify_exit(
thr.proc_data.proc.pid(),
exit_code,
)
{
let _ = ptrace_stop_current(thr, Signo::SIGTRAP, &mut uctx);
}
handle_syscall(&mut uctx);
if thr.proc_data.has_ptrace_pending_event_for(tid)
&& let Some(_resume_sig) =
ptrace_stop_current(thr, Signo::SIGTRAP, &mut uctx)
{
continue;
}
if matches!(
thr.proc_data.take_ptrace_syscall_trace_for(tid),
SyscallTraceState::Exit
) {
let _ = ptrace_syscall_stop_current(thr, Signo::SIGTRAP, &mut uctx);
}
if thr.proc_data.take_ptrace_exec_stop_pending() {
let _is_event =
crate::syscall::ptrace_notify_exec(thr.proc_data.proc.pid());
if let Some(_resume_sig) =
ptrace_stop_current(thr, Signo::SIGTRAP, &mut uctx)
{
continue;
}
}
}
ReturnReason::PageFault(addr, flags) => {
// Count every user-mode fault for /proc/vmstat pgfault (mm/vmstat.c
// semantics: all faults, before resolution). Kernel-mode faults on user
// addresses are counted separately in the mm page-fault handler.
crate::mm::PAGE_FAULT_COUNT
.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
// Classify si_code while holding the aspace lock: an
// existing mapping that rejected the access is a
// permission violation (SEGV_ACCERR), otherwise the
// address is unmapped (SEGV_MAPERR) — matching Linux's
// do_user_addr_fault().
let si_code = {
let aspace = thr.proc_data.aspace();
let mut aspace = aspace.lock();
if aspace.handle_page_fault(addr, flags) {
None
} else if aspace.find_area(addr).is_some() {
Some(SEGV_ACCERR)
} else {
Some(SEGV_MAPERR)
}
};
if let Some(si_code) = si_code {
warn!(
"{:?}: segmentation fault at {:#x} {:?}",
thr.proc_data.proc, addr, flags
);
// POSIX: a synchronous SIGSEGV must carry the
// faulting address in si_addr so handlers can
// classify and recover from guard-page / implicit-
// null-check faults.
raise_signal_fatal(
SignalInfo::new_fault(Signo::SIGSEGV, si_code, addr.as_usize()),
&uctx,
)
.expect("Failed to send SIGSEGV");
}
}
ReturnReason::Interrupt => {}
#[allow(unused_labels)]
ReturnReason::Exception(exc_info) => 'exc: {
let kind = exc_info.kind();
// A uprobe plants an `int3` in user text (delivered as a
// #BP / Breakpoint exception) and completes its
// out-of-line single-step via a #DB / Debug exception.
// Route both to this process' uprobe manager before any
// ptrace / signal handling: if a uprobe owns the
// faulting address it fixes up `uctx` (sets the
// out-of-line PC + single-step, or restores PC after the
// step) and we resume directly. If not, fall through.
match kind {
ExceptionKind::Breakpoint
if crate::uprobe::break_uprobe_handler(&mut uctx).is_some() =>
{
break 'exc;
}
// x86_64 completes the out-of-line single-step via a
// #DB; other arches handle stepping inside the
// breakpoint path, so the debug hook is x86_64-only.
#[cfg(target_arch = "x86_64")]
ExceptionKind::Debug
if crate::uprobe::debug_uprobe_handler(&mut uctx).is_some() =>
{
break 'exc;
}
_ => {}
}
if matches!(kind, ExceptionKind::Breakpoint)
&& (thr.proc_data.is_ptrace_traceme()
|| thr.proc_data.is_ptrace_attached())
{
#[cfg(any(
target_arch = "riscv64",
target_arch = "aarch64",
target_arch = "loongarch64"
))]
{
let _ =
crate::syscall::ptrace_complete_singlestep_breakpoint_if_at_ip(
&thr.proc_data,
thr.tid(),
&mut uctx,
);
}
if let Some(_resume_sig) =
ptrace_stop_current(thr, Signo::SIGTRAP, &mut uctx)
{
break 'exc;
}
}
// On x86_64, PTRACE_SINGLESTEP sets TF in RFLAGS;
// the resulting #DB exception arrives here.
// ExceptionKind::Debug and uctx.rflags only exist on
// x86_64, so this whole block is arch-gated.
#[cfg(target_arch = "x86_64")]
if matches!(kind, ExceptionKind::Debug)
&& (thr.proc_data.is_ptrace_traceme()
|| thr.proc_data.is_ptrace_attached())
{
// Clear TF (bit 8) in the saved RFLAGS. The Intel
// SDM (Vol 3A §17.3.2) states the CPU clears TF
// when delivering a TF-induced #DB, but QEMU may
// not always honour this. Clearing explicitly
// prevents an unwanted extra single-step on resume.
let _ = uctx.clear_single_step_after_debug();
thr.proc_data.set_ptrace_singlestep_for(thr.tid(), false);
if let Some(_resume_sig) =
ptrace_stop_current(thr, Signo::SIGTRAP, &mut uctx)
{
break 'exc;
}
}
if matches!(kind, ExceptionKind::Misaligned) {
#[cfg(target_arch = "loongarch64")]
match unsafe { uctx.emulate_unaligned_at(exc_info.badv as u64) } {
Ok(()) => break 'exc,
Err(err) => {
let exe_path = thr.proc_data.exe_path.read().clone();
warn!(
"loongarch64 unaligned emulation failed: task={}, pid={}, \
exe='{}', ip={:#x}, fault_addr={:#x}, err={}, info={:?}",
curr.id_name(),
thr.proc_data.proc.pid(),
exe_path,
uctx.ip(),
exc_info.fault_addr().unwrap_or(0),
err,
exc_info,
);
}
}
}
let syndrome = exc_info.syndrome();
warn!(
"user exception: ip={:#x}, fault_addr={:#x}, kind={:?}, esr={:#x}, \
ec={:#x}, iss={:#x}, info={:?}",
uctx.ip(),
exc_info.fault_addr().unwrap_or(0),
kind,
syndrome.raw,
syndrome.class,
syndrome.iss,
exc_info
);
let sig_info = match kind {
ExceptionKind::Misaligned => SignalInfo::new_kernel(Signo::SIGBUS),
ExceptionKind::Breakpoint => SignalInfo::new_kernel(Signo::SIGTRAP),
ExceptionKind::IllegalInstruction => {
// AArch64 EL0 reads of ID_AA64*_EL1 (CPU feature
// detection, e.g. the Go runtime) trap as EC=0 /
// IllegalInstruction. Emulate them like Linux
// instead of killing the program with SIGILL.
#[cfg(target_arch = "aarch64")]
if unsafe { uctx.emulate_mrs_id_reg() } {
break 'exc;
}
SignalInfo::new_kernel(Signo::SIGILL)
}
// x86 `#DE`: integer divide-by-zero or the
// `INT_MIN / -1` overflow. POSIX/Linux deliver SIGFPE
// with si_code FPE_INTDIV and si_addr = faulting PC.
// The HotSpot JVM's x86 interpreter/JIT emit a bare
// `idiv` and rely on exactly this signal to raise a
// Java ArithmeticException; routing it through the old
// `_ => SIGTRAP` fall-through made the JVM abort mid
// javac compilation. (Other arches do not trap on
// integer divide-by-zero, so they never reach here.)
ExceptionKind::ArithmeticError => {
SignalInfo::new_fault(Signo::SIGFPE, FPE_INTDIV, uctx.ip())
}
_ => SignalInfo::new_kernel(Signo::SIGTRAP),
};
raise_signal_fatal(sig_info, &uctx)
.expect("Failed to send fatal exception signal");
}
r => {
warn!("Unexpected return reason: {r:?}");
raise_signal_fatal(SignalInfo::new_kernel(Signo::SIGSEGV), &uctx)
.expect("Failed to send SIGSEGV");
}
}
if !unblock_next_signal() {
// POSIX timers are also driven by the alarm task, but polling
// here closes the window where an expired timer is only noticed
// after the current syscall returns to userspace.
poll_process_timer(thr.proc_data.proc.pid());
let eintr_code = -(ax_errno::LinuxError::EINTR.code() as isize);
let restart = if is_syscall
&& (uctx.retval() as isize) == eintr_code
&& syscall_allows_signal_restart(saved_sysno)
{
Some(SyscallRestartInfo {
saved_a0,
saved_sysno,
})
} else {
None
};
// Single-shot: the first delivered signal decides
// whether to restart. Subsequent signals in the same
// loop must not re-apply the decision.
let mut pending_restart = restart.as_ref();
while check_signals(thr, &mut uctx, None, pending_restart) {
pending_restart = None;
}
}
set_timer_state(&curr, TimerState::User);
curr.clear_interrupt();
}
},
name.into(),
crate::config::KERNEL_STACK_SIZE,
)
}
fn ptrace_exit_event_code(sysno: usize, arg0: usize) -> Option<i32> {
match Sysno::new(sysno) {
Some(Sysno::exit | Sysno::exit_group) => Some((arg0 as i32) << 8),
_ => None,
}
}