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UNIX BUILD NOTES

Some notes on how to build Axe Core in Unix.

(for OpenBSD specific instructions, see build-openbsd.md)

Base build dependencies

Building the dependencies and Axe Core requires some essential build tools and libraries to be installed before.

Run the following commands to install required packages:

Debian/Ubuntu:
$ sudo apt-get install curl build-essential libtool autotools-dev automake pkg-config python3 bsdmainutils cmake
Fedora:
$ sudo dnf install gcc-c++ libtool make autoconf automake python3 cmake libstdc++-static patch
Arch Linux:
$ pacman -S base-devel python3 cmake
Alpine Linux:
$ sudo apk --update --no-cache add autoconf automake cmake curl g++ gcc libexecinfo-dev libexecinfo-static libtool make perl pkgconfig python3 patch linux-headers
FreeBSD/OpenBSD:
pkg_add gmake cmake libtool
pkg_add autoconf # (select highest version, e.g. 2.69)
pkg_add automake # (select highest version, e.g. 1.15)
pkg_add python # (select highest version, e.g. 3.5)

Building

Follow the instructions in build-generic

Security

To help make your Axe installation more secure by making certain attacks impossible to exploit even if a vulnerability is found, binaries are hardened by default. This can be disabled with:

Hardening Flags:

./configure --prefix=<prefix> --enable-hardening
./configure --prefix=<prefix> --disable-hardening

Hardening enables the following features:

  • Position Independent Executable Build position independent code to take advantage of Address Space Layout Randomization offered by some kernels. Attackers who can cause execution of code at an arbitrary memory location are thwarted if they don't know where anything useful is located. The stack and heap are randomly located by default but this allows the code section to be randomly located as well.

    On an AMD64 processor where a library was not compiled with -fPIC, this will cause an error such as: "relocation R_X86_64_32 against `......' can not be used when making a shared object;"

    To test that you have built PIE executable, install scanelf, part of paxutils, and use:

      scanelf -e ./axed

    The output should contain:

    TYPE ET_DYN

  • Non-executable Stack If the stack is executable then trivial stack based buffer overflow exploits are possible if vulnerable buffers are found. By default, Axe Core should be built with a non-executable stack but if one of the libraries it uses asks for an executable stack or someone makes a mistake and uses a compiler extension which requires an executable stack, it will silently build an executable without the non-executable stack protection.

    To verify that the stack is non-executable after compiling use: scanelf -e ./axed

    the output should contain: STK/REL/PTL RW- R-- RW-

    The STK RW- means that the stack is readable and writeable but not executable.

Disable-wallet mode

When the intention is to run only a P2P node without a wallet, Axe Core may be compiled in disable-wallet mode with:

./configure --prefix=<prefix> --disable-wallet

In this case there is no dependency on Berkeley DB 4.8.

Mining is also possible in disable-wallet mode, but only using the getblocktemplate RPC call not getwork.

Additional Configure Flags

A list of additional configure flags can be displayed with:

./configure --help

Building on FreeBSD

(TODO, this is untested, please report if it works and if changes to this documentation are needed)

Building on FreeBSD is basically the same as on Linux based systems, with the difference that you have to use gmake instead of make.

Note on debugging: The version of gdb installed by default is ancient and considered harmful. It is not suitable for debugging a multi-threaded C++ program, not even for getting backtraces. Please install the package gdb and use the versioned gdb command e.g. gdb7111.

Building on OpenBSD

(TODO, this is untested, please report if it works and if changes to this documentation are needed)

Important: From OpenBSD 6.2 onwards a C++11-supporting clang compiler is part of the base image, and while building it is necessary to make sure that this compiler is used and not ancient g++ 4.2.1. This is done by appending CC=cc CXX=c++ to configuration commands. Mixing different compilers within the same executable will result in linker errors.

$ cd depends
$ make CC=cc CXX=c++
$ cd ..
$ export AUTOCONF_VERSION=2.69 # replace this with the autoconf version that you installed
$ export AUTOMAKE_VERSION=1.15 # replace this with the automake version that you installed
$ ./autogen.sh
$ ./configure --prefix=<prefix> CC=cc CXX=c++
$ gmake # use -jX here for parallelism

OpenBSD Resource limits

If the build runs into out-of-memory errors, the instructions in this section might help.

The standard ulimit restrictions in OpenBSD are very strict:

data(kbytes)         1572864

This, unfortunately, in some cases not enough to compile some .cpp files in the project, (see issue #6658). If your user is in the staff group the limit can be raised with:

ulimit -d 3000000

The change will only affect the current shell and processes spawned by it. To make the change system-wide, change datasize-cur and datasize-max in /etc/login.conf, and reboot.