add in memory linking

src/bin/bpf-linker.rs

@@ -14,7 +14,7 @@ use std::{
     feature = "rust-llvm-21"
 ))]
 use aya_rustc_llvm_proxy as _;
-use bpf_linker::{Cpu, Linker, LinkerOptions, OptLevel, OutputType};
+use bpf_linker::{Cpu, Linker, LinkerInput, LinkerOptions, OptLevel, OutputType};
 use clap::{
     builder::{PathBufValueParser, TypedValueParser as _},
     error::ErrorKind,
@@ -117,9 +117,9 @@ struct CommandLine {
     #[clap(long)]
     allow_bpf_trap: bool,
 
-    /// Add a directory to the library search path
+    /// UNUSED: it only exists for compatibility with rustc
     #[clap(short = 'L', number_of_values = 1)]
-    libs: Vec<PathBuf>,
+    _libs: Vec<PathBuf>,
 
     /// Optimization level. 0-3, s, or z
     #[clap(short = 'O', default_value = "2")]
@@ -212,7 +212,6 @@ fn main() -> anyhow::Result<()> {
         emit,
         btf,
         allow_bpf_trap,
-        libs,
         optimize,
         export_symbols,
         log_file,
@@ -227,6 +226,7 @@ fn main() -> anyhow::Result<()> {
         export,
         fatal_errors,
         _debug,
+        _libs,
     } = match Parser::try_parse_from(args) {
         Ok(command_line) => command_line,
         Err(err) => match err.kind() {
@@ -271,15 +271,11 @@ fn main() -> anyhow::Result<()> {
 
     let export_symbols = export_symbols.map(fs::read_to_string).transpose()?;
 
-    // TODO: the data is owned by this call frame; we could make this zero-alloc.
     let export_symbols = export_symbols
         .as_deref()
         .into_iter()
         .flat_map(str::lines)
-        .map(str::to_owned)
-        .chain(export)
-        .map(Into::into)
-        .collect();
+        .chain(export.iter().map(String::as_str));
 
     let output_type = match *emit.as_slice() {
         [] => unreachable!("emit has a default value"),
@@ -294,23 +290,25 @@ fn main() -> anyhow::Result<()> {
         target,
         cpu,
         cpu_features,
-        inputs,
-        output,
-        output_type,
-        libs,
         optimize,
-        export_symbols,
         unroll_loops,
         ignore_inline_never,
-        dump_module,
         llvm_args,
         disable_expand_memcpy_in_order,
         disable_memory_builtins,
         btf,
         allow_bpf_trap,
     });
 
-    linker.link()?;
+    if let Some(path) = dump_module {
+        linker.set_dump_module_path(path);
+    }
+
+    let inputs = inputs
+        .iter()
+        .map(|p| LinkerInput::new_from_file(p.as_path()));
+
+    linker.link_to_file(inputs, &output, output_type, export_symbols)?;
 
     if fatal_errors && linker.has_errors() {
         return Err(anyhow::anyhow!(