From 3420339c04c7f093462134bcab9cf9db0c9d697d Mon Sep 17 00:00:00 2001
From: jD91mZM2 <me@krake.one>
Date: Mon, 15 Jun 2020 09:57:09 +0200
Subject: [PATCH] proc scheme: Rewrite try_stop_context
---
src/arch/x86_64/interrupt/exception.rs | 6 +-
src/arch/x86_64/interrupt/syscall.rs | 4 +-
src/ptrace.rs | 27 ++++-----
src/scheme/proc.rs | 83 ++++++++++++--------------
4 files changed, 56 insertions(+), 64 deletions(-)
diff --git a/src/arch/x86_64/interrupt/exception.rs b/src/arch/x86_64/interrupt/exception.rs
index e76f393..e132739 100644
--- a/src/arch/x86_64/interrupt/exception.rs
+++ b/src/arch/x86_64/interrupt/exception.rs
@@ -20,9 +20,9 @@ interrupt_stack!(debug, stack, {
let guard = ptrace::set_process_regs(stack);
- // Disable singlestep before their is a breakpoint, since the
- // breakpoint handler might end up setting it again but unless it
- // does we want the default to be false.
+ // Disable singlestep before there is a breakpoint, since the breakpoint
+ // handler might end up setting it again but unless it does we want the
+ // default to be false.
let had_singlestep = stack.iret.rflags & (1 << 8) == 1 << 8;
stack.set_singlestep(false);
diff --git a/src/arch/x86_64/interrupt/syscall.rs b/src/arch/x86_64/interrupt/syscall.rs
index f084f4c..9ddd3c7 100644
--- a/src/arch/x86_64/interrupt/syscall.rs
+++ b/src/arch/x86_64/interrupt/syscall.rs
@@ -22,10 +22,10 @@ macro_rules! with_interrupt_stack {
unsafe fn $wrapped(stack: *mut InterruptStack) {
let _guard = ptrace::set_process_regs(stack);
- let thumbs_up = ptrace::breakpoint_callback(PTRACE_STOP_PRE_SYSCALL, None)
+ let allowed = ptrace::breakpoint_callback(PTRACE_STOP_PRE_SYSCALL, None)
.and_then(|_| ptrace::next_breakpoint().map(|f| !f.contains(PTRACE_FLAG_IGNORE)));
- if thumbs_up.unwrap_or(true) {
+ if allowed.unwrap_or(true) {
// If syscall not ignored
let $stack = &mut *stack;
$stack.scratch.rax = $code;
diff --git a/src/ptrace.rs b/src/ptrace.rs
index 40e169c..521f154 100644
--- a/src/ptrace.rs
+++ b/src/ptrace.rs
@@ -71,15 +71,6 @@ struct Session {
tracee: WaitCondition,
tracer: WaitCondition,
}
-impl Session {
- fn send_event(&self, event: PtraceEvent) {
- // Add event to queue
- self.data.lock().add_event(event);
-
- // Alert blocking tracers
- self.tracer.notify();
- }
-}
type SessionMap = BTreeMap<ContextId, Arc<Session>>;
@@ -95,8 +86,8 @@ fn sessions_mut() -> RwLockWriteGuard<'static, SessionMap> {
SESSIONS.call_once(init_sessions).write()
}
-/// Try to create a new session, but fail if one already exists for
-/// this process
+/// Try to create a new session, but fail if one already exists for this
+/// process
pub fn try_new_session(pid: ContextId, file_id: usize) -> bool {
let mut sessions = sessions_mut();
@@ -159,14 +150,17 @@ pub fn send_event(event: PtraceEvent) -> Option<()> {
let sessions = sessions();
let session = sessions.get(&context.id)?;
- let data = session.data.lock();
+ let mut data = session.data.lock();
let breakpoint = data.breakpoint.as_ref()?;
if event.cause & breakpoint.flags != event.cause {
return None;
}
- session.send_event(event);
+ // Add event to queue
+ data.add_event(event);
+ // Notify tracer
+ session.tracer.notify();
Some(())
}
@@ -215,14 +209,19 @@ pub fn cont(pid: ContextId) {
/// Create a new breakpoint for the specified tracee, optionally with
/// a sysemu flag. Panics if the session is invalid.
-pub fn set_breakpoint(pid: ContextId, flags: PtraceFlags) {
+pub fn set_breakpoint(pid: ContextId, flags: PtraceFlags, should_continue: bool) {
let sessions = sessions_mut();
let session = sessions.get(&pid).expect("proc (set_breakpoint): invalid session");
let mut data = session.data.lock();
+
data.breakpoint = Some(Breakpoint {
reached: false,
flags
});
+
+ if should_continue {
+ session.tracee.notify();
+ }
}
/// Wait for the tracee to stop. If an event occurs, it returns a copy
diff --git a/src/scheme/proc.rs b/src/scheme/proc.rs
index 31672bc..c99e525 100644
--- a/src/scheme/proc.rs
+++ b/src/scheme/proc.rs
@@ -50,40 +50,34 @@ fn with_context_mut<F, T>(pid: ContextId, callback: F) -> Result<T>
fn try_stop_context<F, T>(pid: ContextId, restart_after: bool, mut callback: F) -> Result<T>
where F: FnMut(&mut Context) -> Result<T>
{
- let mut first = true;
- let mut was_stopped = false; // will never be read
+ // Stop process
+ let (was_stopped, mut running) = with_context_mut(pid, |context| {
+ let was_stopped = context.ptrace_stop;
+ context.ptrace_stop = true;
- loop {
- if !first {
- // We've tried this before, so lets wait before retrying
- unsafe { context::switch(); }
- }
- first = false;
+ Ok((was_stopped, context.running))
+ })?;
- let contexts = context::contexts();
- let context = contexts.get(pid).ok_or(Error::new(ESRCH))?;
- let mut context = context.write();
- if let Status::Exited(_) = context.status {
- return Err(Error::new(ESRCH));
- }
+ // Wait until stopped
+ while running {
+ unsafe { context::switch(); }
- // Stop the process until we've done our thing
- if first {
- was_stopped = context.ptrace_stop;
- }
- context.ptrace_stop = true;
+ running = with_context(pid, |context| {
+ Ok(context.running)
+ })?;
+ }
- if context.running {
- // Process still running, wait until it has stopped
- continue;
- }
+ with_context_mut(pid, |context| {
+ assert!(!context.running, "process can't have been restarted, we stopped it!");
- let ret = callback(&mut context);
+ let ret = callback(context);
- context.ptrace_stop = restart_after && was_stopped;
+ if !was_stopped || restart_after {
+ context.ptrace_stop = false;
+ }
- break ret;
- }
+ ret
+ })
}
#[derive(Clone, Copy, PartialEq, Eq)]
@@ -154,6 +148,7 @@ impl Handle {
fn continue_ignored_children(&mut self) -> Option<()> {
let data = self.data.trace_data()?;
let contexts = context::contexts();
+
for pid in data.clones.drain(..) {
if ptrace::is_traced(pid) {
continue;
@@ -222,8 +217,8 @@ impl Scheme for ProcScheme {
return Err(Error::new(EPERM));
}
- // Is it a subprocess of us? In the future, a capability
- // could bypass this check.
+ // Is it a subprocess of us? In the future, a capability could
+ // bypass this check.
match contexts.anchestors(target.ppid).find(|&(id, _context)| id == current.id) {
Some((id, context)) => {
// Paranoid sanity check, as ptrace security holes
@@ -240,8 +235,8 @@ impl Scheme for ProcScheme {
if let Operation::Trace { .. } = operation {
if !ptrace::try_new_session(pid, id) {
- // There is no good way to handle id being occupied
- // for nothing here, is there?
+ // There is no good way to handle id being occupied for nothing
+ // here, is there?
return Err(Error::new(EBUSY));
}
@@ -347,7 +342,7 @@ impl Scheme for ProcScheme {
let fx = context.arch.get_fx_regs().unwrap_or_default();
Ok((Output { float: fx }, mem::size_of::<FloatRegisters>()))
})?,
- RegsKind::Int => try_stop_context(info.pid, true, |context| match unsafe { ptrace::regs_for(&context) } {
+ RegsKind::Int => try_stop_context(info.pid, false, |context| match unsafe { ptrace::regs_for(&context) } {
None => {
println!("{}:{}: Couldn't read registers from stopped process", file!(), line!());
Err(Error::new(ENOTRECOVERABLE))
@@ -448,7 +443,7 @@ impl Scheme for ProcScheme {
*(buf as *const _ as *const IntRegisters)
};
- try_stop_context(info.pid, true, |context| match unsafe { ptrace::regs_for_mut(context) } {
+ try_stop_context(info.pid, false, |context| match unsafe { ptrace::regs_for_mut(context) } {
None => {
println!("{}:{}: Couldn't read registers from stopped process", file!(), line!());
Err(Error::new(ENOTRECOVERABLE))
@@ -472,21 +467,13 @@ impl Scheme for ProcScheme {
let op = u64::from_ne_bytes(bytes);
let op = PtraceFlags::from_bits(op).ok_or(Error::new(EINVAL))?;
- if !op.contains(PTRACE_FLAG_WAIT) || op.intersects(PTRACE_STOP_MASK) {
- ptrace::cont(info.pid);
- }
- if op.intersects(PTRACE_STOP_MASK) {
- ptrace::set_breakpoint(info.pid, op);
- }
+ let should_continue = !op.contains(PTRACE_FLAG_WAIT) || op.intersects(PTRACE_STOP_MASK);
if op.contains(PTRACE_STOP_SINGLESTEP) {
- // try_stop_context with `false` will
- // automatically disable ptrace_stop
- try_stop_context(info.pid, false, |context| {
+ // `true` to `try_stop_context` means we restart after, no
+ // matter if it was or wasn't stopped before
+ try_stop_context(info.pid, true, |context| {
match unsafe { ptrace::regs_for_mut(context) } {
- // If another CPU is running this process,
- // await for it to be stopped and in such
- // a way the registers can be read!
None => {
println!("{}:{}: Couldn't read registers from stopped process", file!(), line!());
Err(Error::new(ENOTRECOVERABLE))
@@ -505,6 +492,12 @@ impl Scheme for ProcScheme {
})?;
}
+ // Set next breakpoint, and potentially restart tracee
+ if op.intersects(PTRACE_STOP_MASK) {
+ ptrace::set_breakpoint(info.pid, op, should_continue);
+ }
+
+ // And await the tracee, if requested to
if op.contains(PTRACE_FLAG_WAIT) || info.flags & O_NONBLOCK != O_NONBLOCK {
ptrace::wait(info.pid)?;
}
--
GitLab