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diff --git a/tools/perf/util/demangle-rust-v0.h b/tools/perf/util/demangle-rust-v0.h
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+++ b/tools/perf/util/demangle-rust-v0.h
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+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// The contents of this file come from the Rust rustc-demangle library, hosted
+// in the <https://github.com/rust-lang/rustc-demangle> repository, licensed
+// under "Apache-2.0 OR MIT". For copyright details, see
+// <https://github.com/rust-lang/rustc-demangle/blob/main/README.md>.
+// Please note that the file should be kept as close as possible to upstream.
+
+#ifndef _H_DEMANGLE_V0_H
+#define _H_DEMANGLE_V0_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stddef.h>
+
+#if defined(__GNUC__) || defined(__clang__)
+#define DEMANGLE_NODISCARD __attribute__((warn_unused_result))
+#else
+#define DEMANGLE_NODISCARD
+#endif
+
+typedef enum {
+    OverflowOk,
+    OverflowOverflow
+} overflow_status;
+
+enum demangle_style {
+    DemangleStyleUnknown = 0,
+    DemangleStyleLegacy,
+    DemangleStyleV0,
+};
+
+// Not using a union here to make the struct easier to copy-paste if needed.
+struct demangle {
+    enum demangle_style style;
+    // points to the "mangled" part of the name,
+    // not including `ZN` or `R` prefixes.
+    const char *mangled;
+    size_t mangled_len;
+    // In DemangleStyleLegacy, is the number of path elements
+    size_t elements;
+    // while it's called "original", it will not contain `.llvm.9D1C9369@@16` suffixes
+    // that are to be ignored.
+    const char *original;
+    size_t original_len;
+    // Contains the part after the mangled name that is to be outputted,
+    // which can be `.exit.i.i` suffixes LLVM sometimes adds.
+    const char *suffix;
+    size_t suffix_len;
+};
+
+// if the length of the output buffer is less than `output_len-OVERFLOW_MARGIN`,
+// the demangler will return `OverflowOverflow` even if there is no overflow.
+#define OVERFLOW_MARGIN 4
+
+/// Demangle a C string that refers to a Rust symbol and put the demangle intermediate result in `res`.
+/// Beware that `res` contains references into `s`. If `s` is modified (or free'd) before calling
+/// `rust_demangle_display_demangle` behavior is undefined.
+///
+/// Use `rust_demangle_display_demangle` to convert it to an actual string.
+void rust_demangle_demangle(const char *s, struct demangle *res);
+
+/// Write the string in a `struct demangle` into a buffer.
+///
+/// Return `OverflowOk` if the output buffer was sufficiently big, `OverflowOverflow` if it wasn't.
+/// This function is `O(n)` in the length of the input + *output* [$], but the demangled output of demangling a symbol can
+/// be exponentially[$$] large, therefore it is recommended to have a sane bound (`rust-demangle`
+/// uses 1,000,000 bytes) on `len`.
+///
+/// `alternate`, if true, uses the less verbose alternate formatting (Rust `{:#}`) is used, which does not show
+/// symbol hashes and types of constant ints.
+///
+/// [$] It's `O(n * MAX_DEPTH)`, but `MAX_DEPTH` is a constant 300 and therefore it's `O(n)`
+/// [$$] Technically, bounded by `O(n^MAX_DEPTH)`, but this is practically exponential.
+DEMANGLE_NODISCARD overflow_status rust_demangle_display_demangle(struct demangle const *res, char *out, size_t len, bool alternate);
+
+/// Returns true if `res` refers to a known valid Rust demangling style, false if it's an unknown style.
+bool rust_demangle_is_known(struct demangle *res);
+
+#undef DEMANGLE_NODISCARD
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif