refactor(got-patching): extract shared GOT-patching primitives into libdd-got-hook (#2282)

Stacked under [feat(got-hook): add DT_HASH fallback, relocation type
guard, and hook_symbol](#2297)

# What does this PR do?

Moves the ELF GOT-patching infrastructure out of
libdd-profiling-heap-gotter into a new shared crate libdd-got-hook, so
multiple crates can reuse the same machinery for runtime function
interposition.

This is a pure code move. I tried to have no behavioral changes here.

What moves to `libdd-got-hook`
- `DynamicInfo::from_phdr`: parse PT_DYNAMIC from a loaded ELF object
- `gnu_hash` / `gnu_hash_symbol_count` / `gnu_hash_lookup` /
`check_sym`: GNU hash table utilities
- `iterate_libraries`: this is a `dl_iterate_phdr` wrapper with
panic-safe trampoline
- `PageProtGuard` / `read_proc_maps` / `MapEntry`: RELRO-aware page
protection management
- `lookup_symbol` / `LookupResult`: used for resolving a symbol across
all loaded objects
- `elf64_r_sym`: relocation info helper
-  ELF types and constants

What stays in `libdd-profiling-heap-gotter`
- `SymbolOverrides`: multi-symbol registry
- `hooks.rs`: the actual `malloc`/`free`/`calloc`/`realloc` hook
functions
- lib.rs: `install_heap_overrides` / `update_heap_overrides` public API

# Motivation

What inspired you to submit this pull request?

# Additional Notes
Gated on @scottgerring's approval

# How to test the change?

Describe here in detail how the change can be validated.

Author: gyuheon0h

.github/CODEOWNERS

@@ -43,21 +43,22 @@ deny.toml                            @DataDog/libdatadog
 docker-bake.hcl                      @DataDog/apm-common-components-core
 docs                                 @DataDog/libdatadog
 examples                             @DataDog/libdatadog
+libdd-agent-client                   @DataDog/apm-common-components-core
 libdd-alloc/                         @DataDog/libdatadog-profiling
 libdd-capabilities*/                 @DataDog/apm-common-components-core
 libdd-common*/                       @DataDog/libdatadog
 libdd-crashtracker*/                 @DataDog/libdatadog-profiling
 libdd-data-pipeline*/                @DataDog/libdatadog-apm
 libdd-ddsketch*/                     @DataDog/libdatadog-apm @DataDog/apm-common-components-core
 libdd-dogstatsd-client               @DataDog/apm-common-components-core
-libdd-profiling-heap-*/                        @DataDog/libdatadog-profiling
+libdd-gotter/                      @DataDog/libdatadog @DataDog/libdatadog-profiling
 libdd-http-client                    @DataDog/apm-common-components-core
-libdd-agent-client                   @DataDog/apm-common-components-core
 libdd-library-config*/               @DataDog/apm-sdk-capabilities-rust
 libdd-log*/                          @DataDog/apm-common-components-core
 libdd-otel-thread-ctx/               @DataDog/apm-common-components-core
 libdd-otel-thread-ctx-ffi/           @DataDog/apm-common-components-core
 libdd-profiling*/                    @DataDog/libdatadog-profiling
+libdd-profiling-heap-*/              @DataDog/libdatadog-profiling
 libdd-sampling/                      @DataDog/apm-common-components-core
 libdd-shared-runtime*/               @DataDog/apm-common-components-core
 libdd-telemetry*/                    @DataDog/apm-common-components-core

Cargo.lock

@@ -7,6 +7,7 @@ members = [
   "libdd-alloc",
   "libdd-profiling-heap-sampler",
   "libdd-profiling-heap-allocator",
+  "libdd-gotter",
   "libdd-profiling-heap-gotter",
   "libdd-profiling-heap-gotter-ffi",
   "libdd-crashtracker",

Cargo.toml

@@ -220,7 +220,7 @@ js-sys,https://github.com/rustwasm/wasm-bindgen/tree/master/crates/js-sys,MIT OR
 kernel32-sys,https://github.com/retep998/winapi-rs,MIT,Peter Atashian <retep998@gmail.com>
 kv-log-macro,https://github.com/yoshuawuyts/kv-log-macro,MIT OR Apache-2.0,Yoshua Wuyts <yoshuawuyts@gmail.com>
 lazy_static,https://github.com/rust-lang-nursery/lazy-static.rs,MIT OR Apache-2.0,Marvin Löbel <loebel.marvin@gmail.com>
-libc,https://github.com/rust-lang/libc,MIT OR Apache-2.0,The Rust Project Developers
+libc,https://github.com/rust-lang/libc,MIT OR Apache-2.0,The libc Authors
 libdd-libunwind-sys,https://github.com/DataDog/libdatadog/tree/main/libdd-libunwind-sys,Apache-2.0,The libdd-libunwind-sys Authors
 libloading,https://github.com/nagisa/rust_libloading,ISC,Simonas Kazlauskas <libloading@kazlauskas.me>
 libredox,https://gitlab.redox-os.org/redox-os/libredox,MIT,4lDO2 <4lDO2@protonmail.com>

LICENSE-3rdparty.csv

@@ -0,0 +1,18 @@
+# Copyright 2025-Present Datadog, Inc. https://www.datadoghq.com/
+# SPDX-License-Identifier: Apache-2.0
+
+[package]
+name = "libdd-gotter"
+version = "0.1.0"
+description = "ELF GOT-patching primitives for runtime function interposition on 64-bit Linux."
+homepage = "https://github.com/DataDog/libdatadog/tree/main/libdd-gotter"
+repository = "https://github.com/DataDog/libdatadog/tree/main/libdd-gotter"
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+
+[lib]
+bench = false
+
+[dependencies]
+libc.workspace = true

libdd-gotter/Cargo.toml

@@ -0,0 +1,41 @@
+# libdd-gotter
+
+> [!WARNING]
+> This library does runtime function interposition by patching the Global Offset Table (GOT) of loaded ELF objects. This is a substantial intervention in a running process — it modifies function pointers that the dynamic linker has already resolved, affecting all code that calls through those GOT entries. Incorrect use can cause crashes, infinite recursion, heap corruption, or silent data loss. Understand the ELF dynamic linking model before using this crate.
+
+## What it does
+
+When a shared library calls an external function like `malloc`, it jumps through a pointer in its **Global Offset Table** -- a writable table that the dynamic linker fills at load time. This crate walks every loaded ELF object via `dl_iterate_phdr`, parses its `PT_DYNAMIC` segment, and rewrites GOT entries so calls are redirected to a hook function. The original function address is resolved and returned so the hook can forward to it.
+
+## Usage
+
+### Single-symbol hook (crashtracker intercepting `__assert_fail`)
+
+```rust
+use libdd_got_hook::hook_symbol;
+
+static ORIG_FN: AtomicUsize = AtomicUsize::new(0);
+
+unsafe extern "C" fn my_hook(/* same signature as target */) {
+    // ... do work ...
+    // forward to original via ORIG_FN
+}
+
+let mut orig_addr: usize = 0;
+unsafe {
+    hook_symbol(c"__assert_fail", my_hook as *const () as usize, &mut orig_addr);
+}
+// Release pairs with the Acquire load in my_hook, ensuring the GOT
+// patches from hook_symbol are visible before the hook reads orig_addr.
+ORIG_FN.store(orig_addr, Ordering::Release);
+```
+
+### Multi-symbol registry (heap profiling hooking malloc/free/calloc/realloc)
+
+See [`libdd-profiling-heap-gotter`](../libdd-profiling-heap-gotter) which builds a `SymbolOverrides` registry on top of the primitives exported by this crate.
+
+## Support
+This library can be used on ARM64 and AMD64 Linux in processes using glibc or musl runtimes.
+Only symbols that have been dynamically linked can be intercept.
+For instance, if you want to intercept the `malloc` of your C runtime,
+you _cannot_ do so if the application has been statically linked against musl.