misc: arch: drop extern crate, use modern rust

This commit is the first in a series of similar commits to clean up
obsolete `extern crate` statements

Since Rust 1.30, normal macros can be imported via `use`, and with Rust
1.31 and edition 2018 this has become the preferred approach.
`extern crate` is only needed for `alloc` in `no_std` crates, which does
not apply here.

By dropping these (often redundant or odd) `extern crate` lines, we
expose the actual dependencies more clearly and reduce technical debt.

## Auto-generation of the series

Most of this series was produced automatically:

1. Removed all "extern crate" references
2. Run the script [0] to add missing `use` statements
3. Run `cargo +nightly fmt --all`
4. Fix the remaining problems manually

The treewide changes were then split into per-folder commits.

[0]
```python
import os
import re

# Mapping of macro/function usage to imports
MACRO_IMPORTS = {
    "info!": "use log::info;\n",
    "debug!": "use log::debug;\n",
    "error!": "use log::error;\n",
    "trace!": "use log::trace;\n",
    "warn!": "use log::warn;\n",
    "event!": "use event_monitor::event;\n",
    "anyhow!(": "use anyhow::anyhow;\n",
    "bitflags!(": "use bitflags::bitflags;\n",
    "ioctl_ior_nr!": "use vmm_sys_util::{ioctl_ior_nr};\n",
    "ioctl_iow_nr!": "use vmm_sys_util::{ioctl_iow_nr};\n",
}

# Regex for finding the first use statement
USE_REGEX = re.compile(r"^\s*(use|pub use) .+?;")

def process_file(path):
    with open(path, "r", encoding="utf-8") as f:
        lines = f.readlines()

    content = "".join(lines)
    existing_imports = set(lines)
    needed_imports = set()

    # Check macros/functions against mapping, only add if not already present
    for key, import_stmt in MACRO_IMPORTS.items():
        if key in content and import_stmt not in existing_imports:
            needed_imports.add(import_stmt)

    if not needed_imports:
        print(f"Unmodified {path} (no new imports needed)")
        return  # Nothing to do

    # Find first use or pub use statement
    for i, line in enumerate(lines):
        if USE_REGEX.match(line):
            insertion_index = i + 1
            break
    else:
        print(f"Unmodified {path} (no use or pub use statement found)")
        return  # No use statement found, skip file

    # Insert imports
    lines[insertion_index:insertion_index] = list(needed_imports)

    # Write back file
    with open(path, "w", encoding="utf-8") as f:
        f.writelines(lines)

    print(f"Modified {path}, added imports: {''.join(needed_imports).strip()}")

for root, _, files in os.walk("."):
    for file in files:
        if file.endswith(".rs"):
            process_file(os.path.join(root, file))
```

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

arch/src/aarch64/fdt.rs

@@ -19,6 +19,7 @@ use hypervisor::arch::aarch64::regs::{
     AARCH64_ARCH_TIMER_HYP_IRQ, AARCH64_ARCH_TIMER_PHYS_NONSECURE_IRQ,
     AARCH64_ARCH_TIMER_PHYS_SECURE_IRQ, AARCH64_ARCH_TIMER_VIRT_IRQ, AARCH64_PMU_IRQ,
 };
+use log::{debug, warn};
 use thiserror::Error;
 use vm_fdt::{FdtWriter, FdtWriterResult};
 use vm_memory::{Address, Bytes, GuestMemory, GuestMemoryError, GuestMemoryRegion};

arch/src/lib.rs

@@ -8,9 +8,6 @@
 //! Implements platform specific functionality.
 //! Supported platforms: x86_64, aarch64, riscv64.
 
-#[macro_use]
-extern crate log;
-
 use std::collections::BTreeMap;
 use std::sync::Arc;
 use std::{fmt, result};

arch/src/riscv64/fdt.rs

@@ -15,6 +15,7 @@ use std::{cmp, result, str};
 
 use byteorder::{BigEndian, ByteOrder};
 use hypervisor::arch::riscv64::aia::Vaia;
+use log::debug;
 use thiserror::Error;
 use vm_fdt::{FdtWriter, FdtWriterResult};
 use vm_memory::{Address, Bytes, GuestMemory, GuestMemoryError, GuestMemoryRegion};

arch/src/x86_64/mod.rs

@@ -6,11 +6,19 @@
 // Portions Copyright 2017 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE-BSD-3-Clause file.
+
 pub mod interrupts;
 pub mod layout;
+pub mod regs;
+
+#[cfg(feature = "tdx")]
+pub mod tdx;
+
 mod mpspec;
 mod mptable;
-pub mod regs;
+mod smbios;
+
+use std::arch::x86_64;
 use std::mem;
 
 use hypervisor::arch::x86::{CPUID_FLAG_VALID_INDEX, CpuIdEntry};
@@ -19,6 +27,7 @@ use linux_loader::loader::bootparam::{boot_params, setup_header};
 use linux_loader::loader::elf::start_info::{
     hvm_memmap_table_entry, hvm_modlist_entry, hvm_start_info,
 };
+use log::{debug, error, info};
 use thiserror::Error;
 use vm_memory::{
     Address, Bytes, GuestAddress, GuestAddressSpace, GuestMemory, GuestMemoryAtomic,
@@ -26,10 +35,6 @@ use vm_memory::{
 };
 
 use crate::{GuestMemoryMmap, InitramfsConfig, RegionType};
-mod smbios;
-use std::arch::x86_64;
-#[cfg(feature = "tdx")]
-pub mod tdx;
 
 // While modern architectures support more than 255 CPUs via x2APIC,
 // legacy devices such as mptable support at most 254 CPUs.

arch/src/x86_64/mptable.rs

@@ -8,6 +8,7 @@
 use std::{mem, result, slice};
 
 use libc::c_uchar;
+use log::{info, warn};
 use thiserror::Error;
 use vm_memory::{Address, ByteValued, Bytes, GuestAddress, GuestMemory, GuestMemoryError};
 

arch/src/x86_64/tdx/mod.rs

@@ -5,6 +5,7 @@ use std::fs::File;
 use std::io::{Read, Seek, SeekFrom};
 use std::str::FromStr;
 
+use log::{debug, info};
 use thiserror::Error;
 use uuid::Uuid;
 use vm_memory::{ByteValued, Bytes, GuestAddress, GuestMemoryError};