Skip to content

qemu_execution.md

Latest commit

 

History

History
204 lines (153 loc) · 4.28 KB

qemu_execution.md

File metadata and controls

204 lines (153 loc) · 4.28 KB

QEMU Execution Guide

Reference: For ARM64 architecture details, see ../references/arm_architecture.md. For cross-compilation setup, see cross_compilation.md.

Overview

QEMU user-mode emulation allows running ARM64 binaries on x86-64 systems. Proper execution requires understanding static vs dynamic linking and library paths.

Static vs Dynamic Linking

Static Linking (Recommended)

Advantages:

  • No library dependencies
  • Works directly with QEMU (no -L flag needed)
  • Portable - can run on any system with QEMU
  • Simpler execution

Compilation:

aarch64-linux-gnu-gcc -nostdlib -static -o program program.s

Execution:

qemu-aarch64 ./program

Verification:

file program
# Should show: "statically linked"

Dynamic Linking

Requirements:

  • ARM64 library path must be available
  • Requires -L flag with QEMU or binfmt support
  • More complex setup

Compilation:

aarch64-linux-gnu-gcc -nostdlib -o program program.s
# Note: Without -static flag

Execution Options:

Option 1: With Library Path

qemu-aarch64 -L /usr/aarch64-linux-gnu ./program

Option 2: With binfmt Support

# Install binfmt support (automatic library resolution)
sudo apt-get install qemu-user-binfmt
qemu-aarch64 ./program

Common Errors and Solutions

Error: "No such file or directory"

Cause: Dynamic binary can't find ARM64 libraries

Solutions:

  1. Recompile with static linking (recommended):

    aarch64-linux-gnu-gcc -nostdlib -static -o program program.s
qemu-aarch64 ./program

  2. Use -L flag with library path:

    qemu-aarch64 -L /usr/aarch64-linux-gnu ./program

  3. Install binfmt support:

    sudo apt-get install qemu-user-binfmt
qemu-aarch64 ./program

Error: "Exec format error"

Cause: Binary format mismatch or missing interpreter

Solutions:

  1. Verify binary format:

    file program
readelf -h program | grep Machine
# Should show: "ARM aarch64"

  2. Use static linking:

    aarch64-linux-gnu-gcc -nostdlib -static -o program program.s

  3. Check QEMU installation:

    qemu-aarch64 --version

Error: "Cannot find library"

Cause: Dynamic library not found in library path

Solutions:

  1. Find ARM64 library path:

    dpkg -L libc6-dev-arm64-cross | grep libc.so

  2. Use correct library path:

    qemu-aarch64 -L /usr/aarch64-linux-gnu ./program

  3. Install missing libraries:

    sudo apt-get install libc6-dev-arm64-cross

Finding Library Paths

Common ARM64 Library Paths

# Debian/Ubuntu
/usr/aarch64-linux-gnu/
/usr/lib/aarch64-linux-gnu/

# Arch Linux
/usr/aarch64-linux-gnu/
/usr/lib/aarch64-linux-gnu/

# Find installed paths
# Debian/Ubuntu:
dpkg -L libc6-dev-arm64-cross | grep -E "libc\.so|ld-linux"

# Arch Linux:
pacman -Ql aarch64-linux-gnu-glibc | grep -E "libc\.so|ld-linux"

Note: All project Makefiles auto-detect library paths for your distribution.

Verify Library Path

# Check if path exists
ls -la /usr/aarch64-linux-gnu/lib/

# Check for libc
ls -la /usr/aarch64-linux-gnu/lib/libc.so*

Best Practices

  1. Use static linking for standalone programs

    • Simplifies execution
    • No library path issues
    • More portable

  2. Verify binary type before execution

    file program

  3. Test with simple program first

    echo 'int main(){return 0;}' > test.c
aarch64-linux-gnu-gcc -static test.c -o test
qemu-aarch64 ./test

  4. Use binfmt for development (if needed)

    • Automatic library resolution
    • Transparent execution

Debugging with QEMU

Static Binary

qemu-aarch64 -g 1234 ./program &
gdb-multiarch ./program
(gdb) target remote :1234

Dynamic Binary

qemu-aarch64 -g 1234 -L /usr/aarch64-linux-gnu ./program &
gdb-multiarch ./program
(gdb) target remote :1234

References