WSL1 Bun build --compile ELF ENOEXEC repro

README.md

WSL1 Bun build --compile ELF repro

Repro bundle for oven-sh/bun#29963.

Run inside WSL1:

sudo apt-get update
sudo apt-get install -y curl unzip file binutils strace
bash repro-bun-compile-wsl1.sh

Files:

• repro-bun-compile-wsl1.sh: minimal Bun-only repro using official Bun 1.3.11 and 1.3.13 releases.
• repro-opencode-release-wsl1.sh: real-world confirmation with public opencode releases.
• experiment-move-bun-into-rw-load.sh: validates the alternate ELF shape where .bun is mapped through the existing RW PT_LOAD and runs on WSL1.
• experiment-extend-rw-segment.sh: failed intermediate experiment showing why .bun must be moved past old BSS before extending RW PT_LOAD.

Expected primary repro result on WSL1:

Bun 1.3.11 compiled output: runs
Bun 1.3.13 compiled output: execve(...) = -1 ENOEXEC
/lib64/ld-linux-x86-64.so.2 ./hello-1.3.13: runs

experiment-extend-rw-segment.sh

#!/usr/bin/env bash
set -euo pipefail

cd "${1:-/tmp/bun-wsl1-elf-repro-verified}"

cp hello-1.3.13 hello-1.3.13-extend-rw-current

new_filesz=$((0x603a000 + 0x1000 - 0x5f96050))
new_vaddr=$((0x62ae050 + 0x603a000 - 0x5f96050))

printf "new_filesz=0x%x new_vaddr=0x%x\n" "$new_filesz" "$new_vaddr"

perl -e '
  open my $f, "+<", $ARGV[0] or die $!;
  binmode $f;
  sub w64 { my ($off, $v) = @_; seek $f, $off, 0; print $f pack("Q<", $v); }
  sub w32 { my ($off, $v) = @_; seek $f, $off, 0; print $f pack("L<", $v); }
  w64(320, $ARGV[1]);          # RW PT_LOAD p_filesz
  w64(328, $ARGV[1]);          # RW PT_LOAD p_memsz
  w32(456, 0x6474e551);        # appended .bun PT_LOAD -> PT_GNU_STACK
  w64(0x6020000, $ARGV[2]);    # BUN_COMPILED.size original slot -> mapped vaddr
  close $f;
' hello-1.3.13-extend-rw-current "$new_filesz" "$new_vaddr"

readelf -lW hello-1.3.13-extend-rw-current | awk '/Program Headers:/,/Section to Segment mapping:/'

./hello-1.3.13-extend-rw-current

experiment-move-bun-into-rw-load.sh

#!/usr/bin/env bash
set -euo pipefail

cd "${1:-/tmp/bun-wsl1-elf-repro-verified}"

cp hello-1.3.13 hello-1.3.13-rw-load-fixed-shape

perl -e '
  use strict;
  use warnings;
  use Fcntl qw(SEEK_SET);

  my $path = shift;
  open my $f, "+<", $path or die $!;
  binmode $f;
  local $/;
  my $data = <$f>;

  sub u64 { unpack("Q<", substr($data, $_[0], 8)) }
  sub w64 { substr($data, $_[0], 8) = pack("Q<", $_[1]) }
  sub w32 { substr($data, $_[0], 4) = pack("L<", $_[1]) }

  my $rw_ph = 64 + 4 * 56;
  my $extra_ph = 64 + 7 * 56;
  my $shnum = unpack("S<", substr($data, 60, 2));
  my $shentsize = unpack("S<", substr($data, 58, 2));
  my $old_shoff = u64(40);
  my $old_shdr_size = $shnum * $shentsize;

  my $rw_off = u64($rw_ph + 8);
  my $rw_vaddr = u64($rw_ph + 16);
  my $rw_filesz = u64($rw_ph + 32);
  my $rw_memsz = u64($rw_ph + 40);
  my $rw_align = u64($rw_ph + 48);

  my $old_file_backed_end = $rw_off + $rw_filesz;
  my $old_mem_end_vaddr = $rw_vaddr + $rw_memsz;
  my $new_vaddr = ($old_mem_end_vaddr + $rw_align - 1) & ~($rw_align - 1);
  my $new_file_offset = $rw_off + ($new_vaddr - $rw_vaddr);
  my $aligned_payload_size = 0x1000;
  my $new_shoff = $new_file_offset + $aligned_payload_size;
  my $new_file_size = $new_shoff + $old_shdr_size;
  my $new_filesz = $new_file_offset + $aligned_payload_size - $rw_off;

  my $payload = substr($data, 0x603a000, $aligned_payload_size);
  my $shdrs = substr($data, $old_shoff, $old_shdr_size);

  if (length($data) < $new_file_size) {
    $data .= "\0" x ($new_file_size - length($data));
  }

  # Any bytes between the old file-backed data and the moved payload become
  # file-backed BSS after extending the RW segment. They must be zero.
  substr($data, $old_file_backed_end, $new_file_offset - $old_file_backed_end) = "\0" x ($new_file_offset - $old_file_backed_end);
  substr($data, $new_file_offset, $aligned_payload_size) = $payload;
  substr($data, $new_shoff, $old_shdr_size) = $shdrs;

  w64(40, $new_shoff);
  w64($rw_ph + 32, $new_filesz);
  w64($rw_ph + 40, $new_filesz);
  w32($extra_ph, 0x6474e551);
  w64(0x6020000, $new_vaddr);

  # Section header #25 is .bun.
  my $bun_sh = $new_shoff + 25 * $shentsize;
  w64($bun_sh + 16, $new_vaddr);
  w64($bun_sh + 24, $new_file_offset);

  truncate $f, 0;
  seek $f, 0, SEEK_SET;
  print $f $data;
  close $f;

  printf "rw_off=0x%x rw_vaddr=0x%x old_file_backed_end=0x%x old_mem_end_vaddr=0x%x\n", $rw_off, $rw_vaddr, $old_file_backed_end, $old_mem_end_vaddr;
  printf "new_file_offset=0x%x new_vaddr=0x%x new_filesz=0x%x new_shoff=0x%x\n", $new_file_offset, $new_vaddr, $new_filesz, $new_shoff;
' hello-1.3.13-rw-load-fixed-shape

readelf -lW hello-1.3.13-rw-load-fixed-shape | awk '/Program Headers:/,/Section to Segment mapping:/'
readelf -SW hello-1.3.13-rw-load-fixed-shape | grep -E '(^  \[Nr\]|\.bun)'

./hello-1.3.13-rw-load-fixed-shape

repro-bun-compile-wsl1.sh

#!/usr/bin/env bash
set -euo pipefail

# Minimal WSL1 repro for Bun compiled executables failing with ENOEXEC.
# Run inside WSL1. Dependencies: bash, curl, unzip, file, binutils/readelf, strace.

export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

need() {
  if ! command -v "$1" >/dev/null 2>&1; then
    echo "missing dependency: $1" >&2
    echo "install on Debian/Ubuntu with: sudo apt-get update && sudo apt-get install -y curl unzip file binutils strace" >&2
    exit 1
  fi
}

need curl
need unzip
need file
need readelf
need strace
need dd

workdir="${1:-/tmp/bun-wsl1-elf-repro}"
rm -rf "$workdir"
mkdir -p "$workdir"
cd "$workdir"

echo "== environment =="
uname -a
case "$(uname -r)" in
  *Microsoft*) echo "WSL kernel string detected" ;;
  *) echo "warning: this does not look like WSL1" ;;
esac

cat > hello.js <<'JS'
console.log("hello from compiled bun")
JS

download_bun() {
  local version="$1"
  local zip="bun-linux-x64-baseline.zip"
  local url="https://github.com/oven-sh/bun/releases/download/bun-v${version}/${zip}"

  echo "== downloading Bun ${version} =="
  mkdir -p "bun-${version}"
  curl -fsSLo "bun-${version}.zip" "$url"
  unzip -q "bun-${version}.zip" -d "bun-${version}"
  mv "bun-${version}/bun-linux-x64-baseline/bun" "bun-${version}/bun"
  chmod +x "bun-${version}/bun"
  "./bun-${version}/bun" --version
}

compile_with() {
  local version="$1"
  echo "== compiling hello.js with Bun ${version} =="
  "./bun-${version}/bun" build --compile ./hello.js --outfile "./hello-${version}"
  file "./hello-${version}"
}

run_direct() {
  local version="$1"
  echo "== direct exec: hello-${version} =="
  set +e
  "./hello-${version}" >"run-${version}.stdout" 2>"run-${version}.stderr"
  local status=$?
  set -e
  echo "exit=${status}"
  sed -n '1,20p' "run-${version}.stdout"
  sed -n '1,20p' "run-${version}.stderr"
}

show_elf() {
  local version="$1"
  echo "== ELF program headers: hello-${version} =="
  readelf -lW "./hello-${version}" | awk '/Program Headers:/,/Section to Segment mapping:/'
  echo "== .bun section: hello-${version} =="
  readelf -SW "./hello-${version}" | grep -E '(^  \[Nr\]|\.bun)' || true
}

trace_exec() {
  local version="$1"
  echo "== strace execve: hello-${version} =="
  set +e
  strace -f -o "strace-${version}.log" "./hello-${version}" >/dev/null 2>&1
  local status=$?
  set -e
  echo "exit=${status}"
  sed -n '1,12p' "strace-${version}.log"
}

loader_bypass() {
  local version="$1"
  echo "== dynamic loader invocation: hello-${version} =="
  set +e
  /lib64/ld-linux-x86-64.so.2 "./hello-${version}" >"loader-${version}.stdout" 2>"loader-${version}.stderr"
  local status=$?
  set -e
  echo "exit=${status}"
  sed -n '1,20p' "loader-${version}.stdout"
  sed -n '1,20p' "loader-${version}.stderr"
}

patch_extra_load_to_gnu_stack() {
  # Bun 1.3.13 emits 9 program headers. Header #7 (zero-based) is the appended
  # .bun PT_LOAD. Change only p_type from PT_LOAD (1) to PT_GNU_STACK
  # (0x6474e551). This should make WSL1 accept execve, proving the extra PT_LOAD
  # is the loader rejection trigger. The program then crashes because .bun is no
  # longer mapped; that crash is expected.
  echo "== control patch: PT_LOAD -> PT_GNU_STACK for appended .bun segment =="
  cp ./hello-1.3.13 ./hello-1.3.13-no-extra-load
  printf '\x51\xe5\x74\x64' | dd of=./hello-1.3.13-no-extra-load bs=1 seek=456 conv=notrunc status=none
  readelf -lW ./hello-1.3.13-no-extra-load | awk '/Program Headers:/,/Section to Segment mapping:/'
  set +e
  ./hello-1.3.13-no-extra-load >patched.stdout 2>patched.stderr
  local status=$?
  set -e
  echo "exit=${status}"
  sed -n '1,20p' patched.stdout
  sed -n '1,30p' patched.stderr
}

download_bun 1.3.11
download_bun 1.3.13

compile_with 1.3.11
compile_with 1.3.13

run_direct 1.3.11
run_direct 1.3.13

show_elf 1.3.11
show_elf 1.3.13

trace_exec 1.3.13
loader_bypass 1.3.13
patch_extra_load_to_gnu_stack

echo "== output directory =="
pwd

repro-opencode-release-wsl1.sh

#!/usr/bin/env bash
set -euo pipefail

# Real-world confirmation using public opencode release binaries.
# This is not the primary minimal repro; use repro-bun-compile-wsl1.sh first.

export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

need() {
  if ! command -v "$1" >/dev/null 2>&1; then
    echo "missing dependency: $1" >&2
    echo "install on Debian/Ubuntu with: sudo apt-get update && sudo apt-get install -y curl file binutils strace" >&2
    exit 1
  fi
}

need curl
need tar
need file
need readelf
need strace

workdir="${1:-/tmp/opencode-wsl1-elf-repro}"
rm -rf "$workdir"
mkdir -p "$workdir"
cd "$workdir"

echo "== environment =="
uname -a

download_opencode() {
  local version="$1"
  local url="https://github.com/anomalyco/opencode/releases/download/v${version}/opencode-linux-x64.tar.gz"
  echo "== downloading opencode ${version} =="
  mkdir -p "$version"
  curl -fsSL "$url" | tar -xz -C "$version"
  file "$version/opencode"
}

run_direct() {
  local version="$1"
  echo "== direct exec: opencode ${version} =="
  set +e
  "$version/opencode" --version >"run-${version}.stdout" 2>"run-${version}.stderr"
  local status=$?
  set -e
  echo "exit=${status}"
  sed -n '1,20p' "run-${version}.stdout"
  sed -n '1,20p' "run-${version}.stderr"
}

show_elf() {
  local version="$1"
  echo "== ELF program headers: opencode ${version} =="
  readelf -lW "$version/opencode" | awk '/Program Headers:/,/Section to Segment mapping:/'
  echo "== .bun section: opencode ${version} =="
  readelf -SW "$version/opencode" | grep -E '(^  \[Nr\]|\.bun)' || true
}

trace_exec() {
  local version="$1"
  echo "== strace execve: opencode ${version} =="
  set +e
  strace -f -o "strace-${version}.log" "$version/opencode" --version >/dev/null 2>&1
  local status=$?
  set -e
  echo "exit=${status}"
  sed -n '1,12p' "strace-${version}.log"
}

loader_bypass() {
  local version="$1"
  echo "== dynamic loader invocation: opencode ${version} =="
  set +e
  /lib64/ld-linux-x86-64.so.2 "$version/opencode" --version >"loader-${version}.stdout" 2>"loader-${version}.stderr"
  local status=$?
  set -e
  echo "exit=${status}"
  sed -n '1,20p' "loader-${version}.stdout"
  sed -n '1,20p' "loader-${version}.stderr"
}

download_opencode 1.14.20
download_opencode 1.14.21
download_opencode 1.14.30

run_direct 1.14.20
run_direct 1.14.21
run_direct 1.14.30

show_elf 1.14.20
show_elf 1.14.21
show_elf 1.14.30

trace_exec 1.14.30
loader_bypass 1.14.30

echo "== output directory =="
pwd