trace: incorporate events

src/shims/native_lib/mod.rs

@@ -34,18 +34,34 @@ pub struct MemEvents {
 /// A single memory access.
 #[allow(dead_code)]
 #[cfg_attr(target_os = "linux", derive(serde::Serialize, serde::Deserialize))]
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub enum AccessEvent {
-    /// A read may have occurred on this memory range.
-    /// Some instructions *may* read memory without *always* doing that,
-    /// so this can be an over-approximation.
-    /// The range info, however, is reliable if the access did happen.
+    /// A read occurred on this memory range.
     Read(AccessRange),
-    /// A read may have occurred on this memory range.
+    /// A write may have occurred on this memory range.
     /// Some instructions *may* write memory without *always* doing that,
     /// so this can be an over-approximation.
     /// The range info, however, is reliable if the access did happen.
-    Write(AccessRange),
+    /// If the second field is true, the access definitely happened.
+    Write(AccessRange, bool),
+}
+
+impl AccessEvent {
+    fn get_range(&self) -> AccessRange {
+        match self {
+            AccessEvent::Read(access_range) => access_range.clone(),
+            AccessEvent::Write(access_range, _) => access_range.clone(),
+        }
+    }
+
+    fn is_read(&self) -> bool {
+        matches!(self, AccessEvent::Read(_))
+    }
+
+    fn definitely_happened(&self) -> bool {
+        // Anything except a maybe-write is definitive.
+        !matches!(self, AccessEvent::Write(_, false))
+    }
 }
 
 /// The memory touched by a given access.
@@ -59,6 +75,12 @@ pub struct AccessRange {
     pub size: usize,
 }
 
+impl AccessRange {
+    fn end(&self) -> usize {
+        self.addr.strict_add(self.size)
+    }
+}
+
 impl<'tcx> EvalContextExtPriv<'tcx> for crate::MiriInterpCx<'tcx> {}
 trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
     /// Call native host function and return the output as an immediate.
@@ -196,6 +218,43 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
         }
         None
     }
+
+    /// Applies the `events` to Miri's internal state. The event vector must be
+    /// ordered sequentially by when the accesses happened, and the sizes are
+    /// assumed to be exact.
+    fn tracing_apply_accesses(&mut self, events: MemEvents) -> InterpResult<'tcx> {
+        let this = self.eval_context_mut();
+
+        for evt in events.acc_events {
+            let evt_rg = evt.get_range();
+            // We're assuming an access only touches 1 allocation.
+            let alloc_id = this
+                .alloc_id_from_addr(evt_rg.addr.to_u64(), evt_rg.size.try_into().unwrap(), true)
+                .expect("Foreign code did an out-of-bounds access!");
+
+            let alloc = this.get_alloc_raw(alloc_id)?;
+            let alloc_addr = alloc.get_bytes_unchecked_raw().addr();
+
+            // Shift the overlap range to be an offset from the allocation base addr.
+            let overlap = evt_rg.addr.strict_sub(alloc_addr)..evt_rg.end().strict_sub(alloc_addr);
+
+            // Reads are infallible, writes might not be.
+            if evt.is_read() {
+                let p_map = alloc.provenance();
+                for idx in overlap {
+                    // If a provenance was read by the foreign code, expose it.
+                    if let Some(prov) = p_map.get(Size::from_bytes(idx), this) {
+                        this.expose_provenance(prov)?;
+                    }
+                }
+            } else if evt.definitely_happened() || alloc.mutability.is_mut() {
+                //let (alloc, cx) = this.get_alloc_raw_mut(alloc_id)?;
+                //alloc.process_native_write(AllocRange { start: overlap.start, size: overlap.len() })
+            }
+        }
+
+        interp_ok(())
+    }
 }
 
 impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
@@ -221,6 +280,9 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             }
         };
 
+        // Do we have ptrace?
+        let tracing = trace::Supervisor::is_enabled();
+
         // Get the function arguments, and convert them to `libffi`-compatible form.
         let mut libffi_args = Vec::<CArg>::with_capacity(args.len());
         for arg in args.iter() {
@@ -240,9 +302,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 // The first time this happens, print a warning.
                 if !this.machine.native_call_mem_warned.replace(true) {
                     // Newly set, so first time we get here.
-                    this.emit_diagnostic(NonHaltingDiagnostic::NativeCallSharedMem {
-                        tracing: self::trace::Supervisor::is_enabled(),
-                    });
+                    this.emit_diagnostic(NonHaltingDiagnostic::NativeCallSharedMem { tracing });
                 }
 
                 this.expose_provenance(prov)?;
@@ -268,15 +328,21 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             // be read by FFI. The `black_box` is defensive programming as LLVM likes
             // to (incorrectly) optimize away ptr2int casts whose result is unused.
             std::hint::black_box(alloc.get_bytes_unchecked_raw().expose_provenance());
-            // Expose all provenances in this allocation, since the native code can do $whatever.
-            for prov in alloc.provenance().provenances() {
-                this.expose_provenance(prov)?;
+
+            if !tracing {
+                // Expose all provenances in this allocation, since the native code can do $whatever.
+                for prov in alloc.provenance().provenances() {
+                    this.expose_provenance(prov)?;
+                }
             }
 
             // Prepare for possible write from native code if mutable.
             if info.mutbl.is_mut() {
-                let alloc = &mut this.get_alloc_raw_mut(alloc_id)?.0;
+                let (alloc, _cx) = this.get_alloc_raw_mut(alloc_id)?;
                 alloc.prepare_for_native_access();
+                if tracing {
+                    //alloc.process_native_write(&cx.tcx, None);
+                }
                 // Also expose *mutable* provenance for the interpreter-level allocation.
                 std::hint::black_box(alloc.get_bytes_unchecked_raw_mut().expose_provenance());
             }
@@ -288,10 +354,8 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let (ret, maybe_memevents) =
             this.call_native_with_args(link_name, dest, code_ptr, libffi_args)?;
 
-        if cfg!(target_os = "linux")
-            && let Some(events) = maybe_memevents
-        {
-            trace!("Registered FFI events:\n{events:#0x?}");
+        if tracing {
+            this.tracing_apply_accesses(maybe_memevents.unwrap())?;
         }
 
         this.write_immediate(*ret, dest)?;

src/shims/native_lib/trace/parent.rs

@@ -386,7 +386,11 @@ fn capstone_find_events(
                         acc_events.push(AccessEvent::Read(push.clone()));
                     }
                     if acc_ty.is_writable() {
-                        acc_events.push(AccessEvent::Write(push));
+                        // FIXME: This could be made certain; either determine all cases where
+                        // only reads happen, or have an intermediate mempr_* function to first
+                        // map the page(s) as readonly and check if a segfault occurred.
+                        // If this did a read as well, it's possible the write didn't happen.
+                        acc_events.push(AccessEvent::Write(push, !acc_ty.is_readable()));
                     }
 
                     return true;
@@ -442,8 +446,7 @@ fn handle_segfault(
     // Get information on what caused the segfault. This contains the address
     // that triggered it.
     let siginfo = ptrace::getsiginfo(pid).unwrap();
-    // All x86, ARM, etc. instructions only have at most one memory operand
-    // (thankfully!)
+    // All x86 instructions only have at most one memory operand (thankfully!)
     // SAFETY: si_addr is safe to call.
     let addr = unsafe { siginfo.si_addr().addr() };
     let page_addr = addr.strict_sub(addr.strict_rem(page_size));

tests/native-lib/fail/trace_read.rs

@@ -0,0 +1,26 @@
+//@only-target: linux
+//@only-target: gnu
+//@only-target: x86
+//@only-on-host
+//@compile-flags: -Zmiri-native-lib-enable-tracing
+
+extern "C" {
+    fn do_nothing();
+}
+
+fn main() {
+    unexposed_reachable_alloc();
+}
+
+fn unexposed_reachable_alloc() {
+    let inner = 42;
+    let intermediate = &raw const inner;
+    let exposed = (&raw const intermediate).expose_provenance();
+    unsafe { do_nothing() };
+    let invalid: *const i32 = std::ptr::with_exposed_provenance(intermediate.addr());
+    let valid: *const *const i32 = std::ptr::with_exposed_provenance(exposed);
+    unsafe {
+        assert_ne!((*valid).addr(), 0);
+        println!("{}", *invalid); //~ ERROR: Undefined Behavior: pointer not dereferenceable: pointer must be dereferenceable for 4 bytes, but got
+    }
+}

tests/native-lib/fail/trace_read.stderr

@@ -0,0 +1,21 @@
+error: Undefined Behavior: pointer not dereferenceable: pointer must be dereferenceable for 4 bytes, but got $HEX[noalloc] which is a dangling pointer (it has no provenance)
+  --> tests/native-lib/fail/trace_read.rs:LL:CC
+   |
+LL |         println!("{}", *invalid);
+   |                        ^^^^^^^^ Undefined Behavior occurred here
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE:
+   = note: inside `unexposed_reachable_alloc` at tests/native-lib/fail/trace_read.rs:LL:CC
+note: inside `main`
+  --> tests/native-lib/fail/trace_read.rs:LL:CC
+   |
+LL |     unexposed_reachable_alloc();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+

tests/native-lib/fail/trace_write.rs

@@ -0,0 +1,22 @@
+//@only-target: linux
+//@only-target: gnu
+//@only-target: x86
+//@only-on-host
+//@compile-flags: -Zmiri-native-lib-enable-tracing
+
+extern "C" {
+    fn init_n(n: i32, ptr: *mut u8);
+}
+
+fn main() {
+    partial_init();
+}
+
+fn partial_init() {
+    let mut slice: [u8; 10];
+    unsafe {
+        init_n(5, (&raw mut slice).cast());
+        assert!(slice[3] == 0);
+        println!("{}", slice[6]);
+    }
+}

tests/native-lib/pass/ptr_read_access.rs

@@ -1,3 +1,10 @@
+//revisions: trace notrace
+//@[trace] only-target: linux
+//@[trace] only-target: gnu
+//@[trace] only-target: x86
+//@[trace] only-on-host
+//@[trace] compile-flags: -Zmiri-native-lib-enable-tracing
+
 fn main() {
     test_access_pointer();
     test_access_simple();

tests/native-lib/pass/ptr_write_access.rs

@@ -1,3 +1,9 @@
+//revisions: trace notrace
+//@[trace] only-target: linux
+//@[trace] only-target: gnu
+//@[trace] only-target: x86
+//@[trace] only-on-host
+//@[trace] compile-flags: -Zmiri-native-lib-enable-tracing
 //@compile-flags: -Zmiri-permissive-provenance
 
 #![feature(box_as_ptr)]

tests/native-lib/ptr_write_access.c

@@ -107,3 +107,11 @@ EXPORT void set_shared_mem(int32_t** ptr) {
 EXPORT void init_ptr_stored_in_shared_mem(int32_t val) {
   **shared_place = val;
 }
+
+/* Test: partial_init */
+
+EXPORT void init_n(int32_t n, char* ptr) {
+  for (int i=0; i<n; i++) {
+    *ptr = 0;
+  }
+}

tests/native-lib/scalar_arguments.c

@@ -34,3 +34,7 @@ EXPORT int64_t add_short_to_long(int16_t x, int64_t y) {
 int32_t not_exported(void) {
   return 0;
 }
+
+EXPORT void do_nothing(void) {
+  return;
+}