1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
use ax_memory_addr::VirtAddr;
use ax_runtime::hal::cpu::{
trap::PageFaultFlags,
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;
#[cfg(target_arch = "loongarch64")]
use super::unaligned::{UnalignedEmulationResult, emulate_user_unaligned};
use super::{
AsThread, SyscallRestartInfo, SyscallTraceState, Thread, 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};
fn handle_user_page_fault(
thread: &Thread,
address: VirtAddr,
flags: PageFaultFlags,
context: &UserContext,
) {
// 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 = thread.proc_data.aspace();
let mut aspace = aspace.lock();
if aspace.handle_page_fault(address, flags) {
None
} else if aspace.find_area(address).is_some() {
Some(SEGV_ACCERR)
} else {
Some(SEGV_MAPERR)
}
};
if let Some(si_code) = si_code {
warn!(
"{:?}: segmentation fault at {:#x} {:?}",
thread.proc_data.proc, address, flags
);
raise_signal_fatal(
SignalInfo::new_fault(Signo::SIGSEGV, si_code, address.as_usize()),
context,
)
.expect("Failed to send SIGSEGV");
}
}
/// 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();
let resumed_from_initial_ptrace_stop =
if thr.proc_data.ptrace_stop_signo_for(thr.tid()).is_some() {
wait_existing_ptrace_stop_current(thr, &mut uctx);
true
} 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);
true
} else {
false
};
if resumed_from_initial_ptrace_stop {
// `block_on_user` consumes the interruption that aborted the
// stop. Re-scan pending signals before the first user
// instruction so SIGKILL cannot be replaced by a racing
// `_exit(0)`.
while check_signals(thr, &mut uctx, None, None) {}
}
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);
if stop_for_pending_ptrace_event(thr, &mut uctx) {
continue;
}
match reason {
ReturnReason::Syscall => {
let trace_state = thr.proc_data.ptrace_syscall_trace_state_for(tid);
if matches!(trace_state, SyscallTraceState::Entry)
&& let Some(resume_signo) = ptrace_syscall_stop_current(
thr,
Signo::SIGTRAP,
&mut uctx,
saved_sysno,
)
{
enqueue_ptrace_syscall_resume_signal(thr, resume_signo);
}
let syscall_no = uctx.sysno();
let syscall_arg0 = uctx.arg0();
if let Some(exit_code) = ptrace_exit_event_code(syscall_no, syscall_arg0)
&& 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 stop_for_pending_ptrace_event(thr, &mut uctx) {
continue;
}
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;
}
}
if matches!(
thr.proc_data.ptrace_syscall_trace_state_for(tid),
SyscallTraceState::Exit
) {
let resume_signo = ptrace_syscall_stop_current(
thr,
Signo::SIGTRAP,
&mut uctx,
syscall_no,
);
enqueue_ptrace_syscall_resume_signal(thr, resume_signo.flatten());
}
}
ReturnReason::PageFault(addr, flags) => {
handle_user_page_fault(thr, addr, flags, &uctx);
}
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 emulate_user_unaligned(thr, &mut uctx, exc_info.badv) {
Ok(UnalignedEmulationResult::Complete) => break 'exc,
Ok(UnalignedEmulationResult::PageFault { address, flags }) => {
handle_user_page_fault(thr, address, flags, &uctx);
// A resolved fault leaves ERA unchanged; exiting this
// exception block returns to the outer user loop and retries
// the same instruction. A fatal fault is delivered below.
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() {
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();
let mut poll_timer = true;
loop {
// Only acknowledge publications visible before this
// return-to-userspace safe-point scan. A signal that
// races after the snapshot remains pending and forces
// another pass before an interruptible syscall parks.
let interrupt_snapshot = curr.interrupt_snapshot();
if poll_timer {
// 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());
poll_timer = false;
}
while check_signals(thr, &mut uctx, None, pending_restart) {
pending_restart = None;
}
curr.acknowledge_interrupt(interrupt_snapshot);
if !curr.interrupted() {
break;
}
}
}
set_timer_state(&curr, TimerState::User);
}
},
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,
}
}
fn stop_for_pending_ptrace_event(thr: &super::Thread, uctx: &mut UserContext) -> bool {
thr.proc_data.has_ptrace_pending_event_for(thr.tid())
&& ptrace_stop_current(thr, Signo::SIGTRAP, uctx).is_some()
}
fn enqueue_ptrace_syscall_resume_signal(thr: &super::Thread, resume_signo: Option<Signo>) {
let Some(signo) = resume_signo else {
return;
};
// A PTRACE_SYSCALL resume signal is delivered after the matching syscall
// exit stop. Do not arm the ptrace bypass: the tracer must observe its
// subsequent signal-delivery stop.
let _ = thr.signal.send_signal(SignalInfo::new_kernel(signo));
}