Do not escape newlines on Err(LoadError).unwrap()

Wrap verifier logs in a newtype whose `Debug` impl emits unescaped
newlines. This improves ergonomics in tests where we `Result::unwrap()`
those load errors; when these fail today they emit the errors with
newlines escaped, making them incredibly difficult to read.

aya-obj/src/btf/btf.rs

@@ -13,6 +13,7 @@ use log::debug;
 use object::{Endianness, SectionIndex};
 
 use crate::{
+    VerifierLog,
     btf::{
         info::{FuncSecInfo, LineSecInfo},
         relocation::Relocation,
@@ -135,7 +136,7 @@ pub enum BtfError {
         #[source]
         io_error: std::io::Error,
         /// The error log produced by the kernel verifier.
-        verifier_log: String,
+        verifier_log: VerifierLog,
     },
 
     /// offset not found for symbol

aya-obj/src/lib.rs

@@ -89,3 +89,28 @@ mod util;
 
 pub use maps::Map;
 pub use obj::*;
+
+/// An error returned from the verifier.
+///
+/// Provides a [`Debug`] implementation that doesn't escape newlines.
+pub struct VerifierLog(alloc::string::String);
+
+impl VerifierLog {
+    /// Create a new verifier log.
+    pub fn new(log: alloc::string::String) -> Self {
+        Self(log)
+    }
+}
+
+impl std::fmt::Debug for VerifierLog {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        let Self(log) = self;
+        f.write_str(log)
+    }
+}
+
+impl std::fmt::Display for VerifierLog {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        <Self as std::fmt::Debug>::fmt(self, f)
+    }
+}

aya/src/programs/mod.rs

@@ -106,7 +106,7 @@ pub use xdp::{Xdp, XdpError, XdpFlags};
 use crate::{
     generated::{bpf_attach_type, bpf_prog_info, bpf_prog_type},
     maps::MapError,
-    obj::{self, btf::BtfError, Function},
+    obj::{self, btf::BtfError, Function, VerifierLog},
     pin::PinError,
     sys::{
         bpf_btf_get_fd_by_id, bpf_get_object, bpf_load_program, bpf_pin_object,
@@ -142,7 +142,7 @@ pub enum ProgramError {
         #[source]
         io_error: io::Error,
         /// The error log produced by the kernel verifier.
-        verifier_log: String,
+        verifier_log: VerifierLog,
     },
 
     /// A syscall failed.

aya/src/sys/bpf.rs

@@ -10,6 +10,7 @@ use std::{
 use crate::util::KernelVersion;
 use libc::{c_char, c_long, close, ENOENT, ENOSPC};
 use obj::{
+    VerifierLog,
     maps::{bpf_map_def, LegacyMap},
     BpfSectionKind,
 };
@@ -1005,7 +1006,7 @@ pub(crate) fn bpf_prog_get_next_id(id: u32) -> Result<Option<u32>, (c_long, io::
 pub(crate) fn retry_with_verifier_logs(
     max_retries: usize,
     f: impl Fn(&mut [u8]) -> SysResult,
-) -> (SysResult, String) {
+) -> (SysResult, VerifierLog) {
     const MIN_LOG_BUF_SIZE: usize = 1024 * 10;
     const MAX_LOG_BUF_SIZE: usize = (std::u32::MAX >> 8) as usize;
 
@@ -1031,7 +1032,7 @@ pub(crate) fn retry_with_verifier_logs(
         }
         let log_buf = String::from_utf8(log_buf).unwrap();
 
-        break (ret, log_buf);
+        break (ret, VerifierLog::new(log_buf));
     }
 }