Miri subtree update

src/tools/miri/CONTRIBUTING.md

@@ -212,6 +212,15 @@ Miri comes with a few benchmarks; you can run `./miri bench` to run them with th
 Miri. Note: this will run `./miri install` as a side-effect. Also requires `hyperfine` to be
 installed (`cargo install hyperfine`).
 
+To compare the benchmark results with a baseline, do the following:
+- Before applying your changes, run `./miri bench --save-baseline=baseline.json`.
+- Then do your changes.
+- Then run `./miri bench --load-baseline=baseline.json`; the results will include
+  a comparison with the baseline.
+
+You can run only some of the benchmarks by listing them, e.g. `./miri bench mse`.
+The names refer to the folders in `bench-cargo-miri`.
+
 ## Configuring `rust-analyzer`
 
 To configure `rust-analyzer` and the IDE for working on Miri, copy one of the provided

src/tools/miri/README.md

@@ -160,14 +160,14 @@ Certain parts of the execution are picked randomly by Miri, such as the exact ba
 allocations are stored at and the interleaving of concurrently executing threads. Sometimes, it can
 be useful to explore multiple different execution, e.g. to make sure that your code does not depend
 on incidental "super-alignment" of new allocations and to test different thread interleavings.
-This can be done with the `--many-seeds` flag:
+This can be done with the `-Zmiri-many-seeds` flag:
 
 ```
-cargo miri test --many-seeds # tries the seeds in 0..64
-cargo miri test --many-seeds=0..16
+MIRIFLAGS="-Zmiri-many-seeds" cargo miri test # tries the seeds in 0..64
+MIRIFLAGS="-Zmiri-many-seeds=0..16" cargo miri test
 ```
 
-The default of 64 different seeds is quite slow, so you probably want to specify a smaller range.
+The default of 64 different seeds can be quite slow, so you often want to specify a smaller range.
 
 ### Running Miri on CI
 
@@ -294,9 +294,10 @@ environment variable. We first document the most relevant and most commonly used
   will always fail and `0.0` means it will never fail. Note that setting it to
   `1.0` will likely cause hangs, since it means programs using
   `compare_exchange_weak` cannot make progress.
-* `-Zmiri-disable-isolation` disables host isolation.  As a consequence,
+* `-Zmiri-disable-isolation` disables host isolation. As a consequence,
   the program has access to host resources such as environment variables, file
   systems, and randomness.
+  This overwrites a previous `-Zmiri-isolation-error`.
 * `-Zmiri-disable-leak-backtraces` disables backtraces reports for memory leaks. By default, a
   backtrace is captured for every allocation when it is created, just in case it leaks. This incurs
   some memory overhead to store data that is almost never used. This flag is implied by
@@ -317,6 +318,15 @@ environment variable. We first document the most relevant and most commonly used
   execution with a "permission denied" error being returned to the program.
   `warn` prints a full backtrace each time that happens; `warn-nobacktrace` is less
   verbose and shown at most once per operation. `hide` hides the warning entirely.
+  This overwrites a previous `-Zmiri-disable-isolation`.
+* `-Zmiri-many-seeds=[<from>]..<to>` runs the program multiple times with different seeds for Miri's
+  RNG. With different seeds, Miri will make different choices to resolve non-determinism such as the
+  order in which concurrent threads are scheduled, or the exact addresses assigned to allocations.
+  This is useful to find bugs that only occur under particular interleavings of concurrent threads,
+  or that otherwise depend on non-determinism. If the `<from>` part is skipped, it defaults to `0`.
+  Can be used without a value; in that case the range defaults to `0..64`.
+* `-Zmiri-many-seeds-keep-going` tells Miri to really try all the seeds in the given range, even if
+  a failing seed has already been found. This is useful to determine which fraction of seeds fails.
 * `-Zmiri-num-cpus` states the number of available CPUs to be reported by miri. By default, the
   number of available CPUs is `1`. Note that this flag does not affect how miri handles threads in
   any way.
@@ -339,8 +349,8 @@ environment variable. We first document the most relevant and most commonly used
   can increase test coverage by running Miri multiple times with different seeds.
 * `-Zmiri-strict-provenance` enables [strict
   provenance](https://github.com/rust-lang/rust/issues/95228) checking in Miri. This means that
-  casting an integer to a pointer yields a result with 'invalid' provenance, i.e., with provenance
-  that cannot be used for any memory access.
+  casting an integer to a pointer will stop execution because the provenance of the pointer
+  cannot be determined.
 * `-Zmiri-symbolic-alignment-check` makes the alignment check more strict.  By default, alignment is
   checked by casting the pointer to an integer, and making sure that is a multiple of the alignment.
   This can lead to cases where a program passes the alignment check by pure chance, because things
@@ -429,6 +439,8 @@ to Miri failing to detect cases of undefined behavior in a program.
   of Rust will be stricter than Tree Borrows. In other words, if you use Tree Borrows,
   even if your code is accepted today, it might be declared UB in the future.
   This is much less likely with Stacked Borrows.
+  Using Tree Borrows currently implies `-Zmiri-strict-provenance` because integer-to-pointer
+  casts are not supported in this mode, but that may change in the future.
 * `-Zmiri-force-page-size=<num>` overrides the default page size for an architecture, in multiples of 1k.
   `4` is default for most targets. This value should always be a power of 2 and nonzero.
 * `-Zmiri-unique-is-unique` performs additional aliasing checks for `core::ptr::Unique` to ensure

src/tools/miri/cargo-miri/src/phases.rs

@@ -1,10 +1,10 @@
 //! Implements the various phases of `cargo miri run/test`.
 
+use std::env;
 use std::fs::{self, File};
-use std::io::{BufReader, Write};
+use std::io::BufReader;
 use std::path::{Path, PathBuf};
 use std::process::Command;
-use std::{env, thread};
 
 use rustc_version::VersionMeta;
 
@@ -24,10 +24,7 @@ Subcommands:
     clean                    Clean the Miri cache & target directory
 
 The cargo options are exactly the same as for `cargo run` and `cargo test`, respectively.
-Furthermore, the following extra flags and environment variables are recognized for `run` and `test`:
-
-    --many-seeds[=from..to]  Run the program/tests many times with different seeds in the given range.
-                             The range defaults to `0..64`.
+Furthermore, the following environment variables are recognized for `run` and `test`:
 
     MIRIFLAGS                Extra flags to pass to the Miri driver. Use this to pass `-Zmiri-...` flags.
 
@@ -41,8 +38,6 @@ Examples:
 
 ";
 
-const DEFAULT_MANY_SEEDS: &str = "0..64";
-
 fn show_help() {
     println!("{CARGO_MIRI_HELP}");
 }
@@ -182,17 +177,15 @@ pub fn phase_cargo_miri(mut args: impl Iterator<Item = String>) {
     let target_dir = get_target_dir(&metadata);
     cmd.arg("--target-dir").arg(target_dir);
 
-    // Store many-seeds argument.
-    let mut many_seeds = None;
     // *After* we set all the flags that need setting, forward everything else. Make sure to skip
-    // `--target-dir` (which would otherwise be set twice) and `--many-seeds` (which is our flag, not cargo's).
+    // `--target-dir` (which would otherwise be set twice).
     for arg in
         ArgSplitFlagValue::from_string_iter(&mut args, "--target-dir").filter_map(Result::err)
     {
-        if arg == "--many-seeds" {
-            many_seeds = Some(DEFAULT_MANY_SEEDS.to_owned());
-        } else if let Some(val) = arg.strip_prefix("--many-seeds=") {
-            many_seeds = Some(val.to_owned());
+        if arg == "--many-seeds" || arg.starts_with("--many-seeds=") {
+            show_error!(
+                "ERROR: the `--many-seeds` flag has been removed from cargo-miri; use MIRIFLAGS=-Zmiri-many-seeds instead"
+            );
         } else {
             cmd.arg(arg);
         }
@@ -249,9 +242,6 @@ pub fn phase_cargo_miri(mut args: impl Iterator<Item = String>) {
     // Forward some crucial information to our own re-invocations.
     cmd.env("MIRI_SYSROOT", miri_sysroot);
     cmd.env("MIRI_LOCAL_CRATES", local_crates(&metadata));
-    if let Some(many_seeds) = many_seeds {
-        cmd.env("MIRI_MANY_SEEDS", many_seeds);
-    }
     if verbose > 0 {
         cmd.env("MIRI_VERBOSE", verbose.to_string()); // This makes the other phases verbose.
     }
@@ -407,14 +397,11 @@ pub fn phase_rustc(mut args: impl Iterator<Item = String>, phase: RustcPhase) {
 
             // Alter the `-o` parameter so that it does not overwrite the JSON file we stored above.
             let mut args = env.args;
-            let mut out_filename = None;
             for i in 0..args.len() {
                 if args[i] == "-o" {
-                    out_filename = Some(args[i + 1].clone());
                     args[i + 1].push_str(".miri");
                 }
             }
-            let out_filename = out_filename.expect("rustdoc must pass `-o`");
 
             cmd.args(&args);
             cmd.env("MIRI_BE_RUSTC", "target");
@@ -427,7 +414,7 @@ pub fn phase_rustc(mut args: impl Iterator<Item = String>, phase: RustcPhase) {
                 eprintln!("[cargo-miri rustc inside rustdoc] going to run:\n{cmd:?}");
             }
 
-            exec_with_pipe(cmd, &env.stdin, format!("{out_filename}.stdin"));
+            exec_with_pipe(cmd, &env.stdin);
         }
 
         return;
@@ -589,111 +576,81 @@ pub fn phase_runner(mut binary_args: impl Iterator<Item = String>, phase: Runner
         }
     };
 
-    let many_seeds = env::var("MIRI_MANY_SEEDS");
-    run_many_seeds(many_seeds.ok(), |seed| {
-        let mut cmd = miri();
-
-        // Set missing env vars. We prefer build-time env vars over run-time ones; see
-        // <https://github.com/rust-lang/miri/issues/1661> for the kind of issue that fixes.
-        for (name, val) in &info.env {
-            // `CARGO_MAKEFLAGS` contains information about how to reach the jobserver, but by the time
-            // the program is being run, that jobserver no longer exists (cargo only runs the jobserver
-            // for the build portion of `cargo run`/`cargo test`). Hence we shouldn't forward this.
-            // Also see <https://github.com/rust-lang/rust/pull/113730>.
-            if name == "CARGO_MAKEFLAGS" {
-                continue;
-            }
-            if let Some(old_val) = env::var_os(name) {
-                if *old_val == *val {
-                    // This one did not actually change, no need to re-set it.
-                    // (This keeps the `debug_cmd` below more manageable.)
-                    continue;
-                } else if verbose > 0 {
-                    eprintln!(
-                        "[cargo-miri runner] Overwriting run-time env var {name:?}={old_val:?} with build-time value {val:?}"
-                    );
-                }
-            }
-            cmd.env(name, val);
-        }
+    let mut cmd = miri();
 
-        if phase != RunnerPhase::Rustdoc {
-            // Set the sysroot. Not necessary in rustdoc, where we already set the sysroot in
-            // `phase_rustdoc`. rustdoc will forward that flag when invoking rustc (i.e., us), so the
-            // flag is present in `info.args`.
-            cmd.arg("--sysroot").arg(env::var_os("MIRI_SYSROOT").unwrap());
+    // Set missing env vars. We prefer build-time env vars over run-time ones; see
+    // <https://github.com/rust-lang/miri/issues/1661> for the kind of issue that fixes.
+    for (name, val) in &info.env {
+        // `CARGO_MAKEFLAGS` contains information about how to reach the jobserver, but by the time
+        // the program is being run, that jobserver no longer exists (cargo only runs the jobserver
+        // for the build portion of `cargo run`/`cargo test`). Hence we shouldn't forward this.
+        // Also see <https://github.com/rust-lang/rust/pull/113730>.
+        if name == "CARGO_MAKEFLAGS" {
+            continue;
         }
-        // Forward rustc arguments.
-        // We need to patch "--extern" filenames because we forced a check-only
-        // build without cargo knowing about that: replace `.rlib` suffix by
-        // `.rmeta`.
-        // We also need to remove `--error-format` as cargo specifies that to be JSON,
-        // but when we run here, cargo does not interpret the JSON any more. `--json`
-        // then also needs to be dropped.
-        let mut args = info.args.iter();
-        while let Some(arg) = args.next() {
-            if arg == "--extern" {
-                forward_patched_extern_arg(&mut (&mut args).cloned(), &mut cmd);
-            } else if let Some(suffix) = arg.strip_prefix("--error-format") {
-                assert!(suffix.starts_with('='));
-                // Drop this argument.
-            } else if let Some(suffix) = arg.strip_prefix("--json") {
-                assert!(suffix.starts_with('='));
-                // Drop this argument.
-            } else {
-                cmd.arg(arg);
+        if let Some(old_val) = env::var_os(name) {
+            if *old_val == *val {
+                // This one did not actually change, no need to re-set it.
+                // (This keeps the `debug_cmd` below more manageable.)
+                continue;
+            } else if verbose > 0 {
+                eprintln!(
+                    "[cargo-miri runner] Overwriting run-time env var {name:?}={old_val:?} with build-time value {val:?}"
+                );
             }
         }
-        // Respect `MIRIFLAGS`.
-        if let Ok(a) = env::var("MIRIFLAGS") {
-            let args = flagsplit(&a);
-            cmd.args(args);
-        }
-        // Set the current seed.
-        if let Some(seed) = seed {
-            eprintln!("Trying seed: {seed}");
-            cmd.arg(format!("-Zmiri-seed={seed}"));
-        }
+        cmd.env(name, val);
+    }
 
-        // Then pass binary arguments.
-        cmd.arg("--");
-        cmd.args(&binary_args);
-
-        // Make sure we use the build-time working directory for interpreting Miri/rustc arguments.
-        // But then we need to switch to the run-time one, which we instruct Miri to do by setting `MIRI_CWD`.
-        cmd.current_dir(&info.current_dir);
-        cmd.env("MIRI_CWD", env::current_dir().unwrap());
-
-        // Run it.
-        debug_cmd("[cargo-miri runner]", verbose, &cmd);
-
-        match phase {
-            RunnerPhase::Rustdoc => {
-                cmd.stdin(std::process::Stdio::piped());
-                // the warning is wrong, we have a `wait` inside the `scope` closure.
-                let mut child = cmd.spawn().expect("failed to spawn process");
-                let child_stdin = child.stdin.take().unwrap();
-                // Write stdin in a background thread, as it may block.
-                let exit_status = thread::scope(|s| {
-                    s.spawn(|| {
-                        let mut child_stdin = child_stdin;
-                        // Ignore failure, it is most likely due to the process having terminated.
-                        let _ = child_stdin.write_all(&info.stdin);
-                    });
-                    child.wait().expect("failed to run command")
-                });
-                if !exit_status.success() {
-                    std::process::exit(exit_status.code().unwrap_or(-1));
-                }
-            }
-            RunnerPhase::Cargo => {
-                let exit_status = cmd.status().expect("failed to run command");
-                if !exit_status.success() {
-                    std::process::exit(exit_status.code().unwrap_or(-1));
-                }
-            }
+    if phase != RunnerPhase::Rustdoc {
+        // Set the sysroot. Not necessary in rustdoc, where we already set the sysroot in
+        // `phase_rustdoc`. rustdoc will forward that flag when invoking rustc (i.e., us), so the
+        // flag is present in `info.args`.
+        cmd.arg("--sysroot").arg(env::var_os("MIRI_SYSROOT").unwrap());
+    }
+    // Forward rustc arguments.
+    // We need to patch "--extern" filenames because we forced a check-only
+    // build without cargo knowing about that: replace `.rlib` suffix by
+    // `.rmeta`.
+    // We also need to remove `--error-format` as cargo specifies that to be JSON,
+    // but when we run here, cargo does not interpret the JSON any more. `--json`
+    // then also needs to be dropped.
+    let mut args = info.args.iter();
+    while let Some(arg) = args.next() {
+        if arg == "--extern" {
+            forward_patched_extern_arg(&mut (&mut args).cloned(), &mut cmd);
+        } else if let Some(suffix) = arg.strip_prefix("--error-format") {
+            assert!(suffix.starts_with('='));
+            // Drop this argument.
+        } else if let Some(suffix) = arg.strip_prefix("--json") {
+            assert!(suffix.starts_with('='));
+            // Drop this argument.
+        } else {
+            cmd.arg(arg);
         }
-    });
+    }
+    // Respect `MIRIFLAGS`.
+    if let Ok(a) = env::var("MIRIFLAGS") {
+        let args = flagsplit(&a);
+        cmd.args(args);
+    }
+
+    // Then pass binary arguments.
+    cmd.arg("--");
+    cmd.args(&binary_args);
+
+    // Make sure we use the build-time working directory for interpreting Miri/rustc arguments.
+    // But then we need to switch to the run-time one, which we instruct Miri to do by setting `MIRI_CWD`.
+    cmd.current_dir(&info.current_dir);
+    cmd.env("MIRI_CWD", env::current_dir().unwrap());
+
+    // Run it.
+    debug_cmd("[cargo-miri runner]", verbose, &cmd);
+
+    match phase {
+        RunnerPhase::Rustdoc => exec_with_pipe(cmd, &info.stdin),
+        RunnerPhase::Cargo => exec(cmd),
+    }
 }
 
 pub fn phase_rustdoc(mut args: impl Iterator<Item = String>) {