Rollup merge of #122249 - RalfJung:machine-read-hook, r=oli-obk

interpret: do not call machine read hooks during validation

Fixes #3347

r? ``@oli-obk``

tests/pass/alloc-access-tracking.rs

@@ -0,0 +1,25 @@
+#![feature(start)]
+#![no_std]
+//@compile-flags: -Zmiri-track-alloc-id=17 -Zmiri-track-alloc-accesses -Cpanic=abort
+//@only-target-linux: alloc IDs differ between OSes for some reason
+
+extern "Rust" {
+    fn miri_alloc(size: usize, align: usize) -> *mut u8;
+    fn miri_dealloc(ptr: *mut u8, size: usize, align: usize);
+}
+
+#[start]
+fn start(_: isize, _: *const *const u8) -> isize {
+    unsafe {
+        let ptr = miri_alloc(123, 1);
+        *ptr = 42; // Crucially, only a write is printed here, no read!
+        assert_eq!(*ptr, 42);
+        miri_dealloc(ptr, 123, 1);
+    }
+    0
+}
+
+#[panic_handler]
+fn panic_handler(_: &core::panic::PanicInfo) -> ! {
+    loop {}
+}

tests/pass/alloc-access-tracking.stderr

@@ -0,0 +1,37 @@
+note: tracking was triggered
+  --> $DIR/alloc-access-tracking.rs:LL:CC
+   |
+LL |         let ptr = miri_alloc(123, 1);
+   |                   ^^^^^^^^^^^^^^^^^^ created Miri bare-metal heap allocation of 123 bytes (alignment ALIGN bytes) with id 17
+   |
+   = note: BACKTRACE:
+   = note: inside `start` at $DIR/alloc-access-tracking.rs:LL:CC
+
+note: tracking was triggered
+  --> $DIR/alloc-access-tracking.rs:LL:CC
+   |
+LL |         *ptr = 42; // Crucially, only a write is printed here, no read!
+   |         ^^^^^^^^^ write access to allocation with id 17
+   |
+   = note: BACKTRACE:
+   = note: inside `start` at $DIR/alloc-access-tracking.rs:LL:CC
+
+note: tracking was triggered
+  --> $DIR/alloc-access-tracking.rs:LL:CC
+   |
+LL |         assert_eq!(*ptr, 42);
+   |         ^^^^^^^^^^^^^^^^^^^^ read access to allocation with id 17
+   |
+   = note: BACKTRACE:
+   = note: inside `start` at RUSTLIB/core/src/macros/mod.rs:LL:CC
+   = note: this note originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+note: tracking was triggered
+  --> $DIR/alloc-access-tracking.rs:LL:CC
+   |
+LL |         miri_dealloc(ptr, 123, 1);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^ freed allocation with id 17
+   |
+   = note: BACKTRACE:
+   = note: inside `start` at $DIR/alloc-access-tracking.rs:LL:CC
+