From cbb17327aad64621c8150736aa2fe3a34764ea96 Mon Sep 17 00:00:00 2001
From: jD91mZM2 <me@krake.one>
Date: Tue, 16 Jun 2020 13:00:27 +0200
Subject: [PATCH] ptrace: Block on read, not on write
---
src/ptrace.rs | 6 ++++
src/scheme/proc.rs | 68 ++++++++++++++++++++++++----------------------
syscall | 2 +-
3 files changed, 43 insertions(+), 33 deletions(-)
diff --git a/src/ptrace.rs b/src/ptrace.rs
index b55b3f6..7029d84 100644
--- a/src/ptrace.rs
+++ b/src/ptrace.rs
@@ -73,6 +73,12 @@ impl SessionData {
});
}
+ /// Returns true if the breakpoint is reached, or if there isn't a
+ /// breakpoint
+ pub fn is_reached(&self) -> bool {
+ self.breakpoint.as_ref().map(|b| b.reached).unwrap_or(false)
+ }
+
/// Used for getting the flags in fevent
pub fn session_fevent_flags(&self) -> EventFlags {
let mut flags = EventFlags::empty();
diff --git a/src/scheme/proc.rs b/src/scheme/proc.rs
index 37f640d..f80f166 100644
--- a/src/scheme/proc.rs
+++ b/src/scheme/proc.rs
@@ -365,27 +365,42 @@ impl Scheme for ProcScheme {
Ok(len)
},
Operation::Trace => {
+ let mut handles = self.handles.write();
+ let handle = handles.get_mut(&id).ok_or(Error::new(EBADF))?;
+ let data = handle.data.trace_data().expect("operations can't change");
+
+ // Wait for event
+ if handle.info.flags & O_NONBLOCK != O_NONBLOCK {
+ ptrace::wait(handle.info.pid)?;
+ }
+
+ // Read events
let slice = unsafe {
slice::from_raw_parts_mut(
buf.as_mut_ptr() as *mut PtraceEvent,
buf.len() / mem::size_of::<PtraceEvent>()
)
};
- let read = ptrace::Session::with_session(info.pid, |session| {
- Ok(session.data.lock().recv_events(slice))
+ let (read, reached) = ptrace::Session::with_session(info.pid, |session| {
+ let mut data = session.data.lock();
+ Ok((data.recv_events(slice), data.is_reached()))
})?;
- // Won't context switch, don't worry about the locks
- let mut handles = self.handles.write();
- let handle = handles.get_mut(&id).ok_or(Error::new(EBADF))?;
- let data = handle.data.trace_data().expect("operations can't change");
-
+ // Save child processes in a list of processes to restart
for event in &slice[..read] {
if event.cause == PTRACE_EVENT_CLONE {
data.clones.push(ContextId::from(event.a));
}
}
+ // If there are no events, and breakpoint isn't reached, we
+ // must not have waited.
+ if read == 0 && !reached {
+ assert!(handle.info.flags & O_NONBLOCK == O_NONBLOCK, "wait woke up spuriously??");
+ return Err(Error::new(EAGAIN));
+ }
+
+ // Return read events
Ok(read * mem::size_of::<PtraceEvent>())
}
}
@@ -470,15 +485,12 @@ impl Scheme for ProcScheme {
let op = u64::from_ne_bytes(bytes);
let op = PtraceFlags::from_bits(op).ok_or(Error::new(EINVAL))?;
- let should_continue = !op.contains(PTRACE_FLAG_WAIT) || op.intersects(PTRACE_STOP_MASK);
-
// Set next breakpoint
ptrace::Session::with_session(info.pid, |session| {
- if op.intersects(PTRACE_STOP_MASK) {
- session.data.lock().set_breakpoint(Some(op));
- } else if should_continue {
- session.data.lock().set_breakpoint(None);
- }
+ session.data.lock().set_breakpoint(
+ Some(op)
+ .filter(|op| op.intersects(PTRACE_STOP_MASK | PTRACE_EVENT_MASK))
+ );
Ok(())
})?;
@@ -497,25 +509,17 @@ impl Scheme for ProcScheme {
})?;
}
- // Continue execution, if requested
- if should_continue {
- // disable the ptrace_stop flag, which is used in some cases
- with_context_mut(info.pid, |context| {
- context.ptrace_stop = false;
- Ok(())
- })?;
-
- // and notify the tracee's WaitCondition, which is used in other cases
- ptrace::Session::with_session(info.pid, |session| {
- session.tracee.notify();
- Ok(())
- })?;
- }
+ // disable the ptrace_stop flag, which is used in some cases
+ with_context_mut(info.pid, |context| {
+ context.ptrace_stop = false;
+ Ok(())
+ })?;
- // And await the tracee, if requested
- if op.contains(PTRACE_FLAG_WAIT) || info.flags & O_NONBLOCK != O_NONBLOCK {
- ptrace::wait(info.pid)?;
- }
+ // and notify the tracee's WaitCondition, which is used in other cases
+ ptrace::Session::with_session(info.pid, |session| {
+ session.tracee.notify();
+ Ok(())
+ })?;
Ok(mem::size_of::<u64>())
}
diff --git a/syscall b/syscall
index 6ba71e7..1c637e7 160000
--- a/syscall
+++ b/syscall
@@ -1 +1 @@
-Subproject commit 6ba71e7e065d37309b7d5c4fc86835dd350f61b7
+Subproject commit 1c637e72b2f3be8e8f942372e8414101e463df98
--
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