Dmitry Levin

strace is a diagnostic, debugging and instructional utility for Linux. It is used to monitor and tamper with interactions between processes and the Linux kernel, which include system calls, signal deliveries, and changes of process state. In this talk the maintainer of strace will describe new features implemented since FOSDEM 2018.

Several interesting features were implemented within strace project since FOSDEM 2018, including:

• seccomp-assisted system call filtering
• system call return status filtering
• PTRACE_GET_SYSCALL_INFO API support
• new options: -DD, -DDD, -X, -z, -Z

In this talk the maintainer of strace will describe these new features and demonstrate what kinds of problems they help to solve.

Set-versioned package dependencies is a free software technology invented in ALT and implemented in ALT package repositories and distributions since 2010 to prevent breakages caused by updates of shared libraries containing incompatible changes.

Every time a shared library is going to be updated, there is a chance of incompatible changes in the library that will cause breakages in some of its clients. This happens, for example, when a symbol provided by the library is removed but the soname remains unchanged. Detecting such changes manually is getting more problematic nowadays when packages are updated automatically by scripts.

The approach implemented in ALT package repositories to address this problem is to encode all symbols provided by shared libraries in package Provide tags, and to encode all symbols required by clients of shared libraries in package Require tags.

In this talk the speaker will describe in detail how to implement such encoding efficiently, explain the computational costs associated with set-versioned package dependencies, and share his experience of maintaining package repositories based on set-versions.

The primary auditory of this talk are maintainers of package repositories and distributions who might be interested in addressing the problem of shared library updates.

strace is a diagnostic, debugging and instructional utility for Linux. It is used to monitor and tamper with interactions between processes and the Linux kernel, which include system calls, signal deliveries, and changes of process state. In this talk the maintainer of strace will describe new features implemented since FOSDEM 2017.

In 2017, several interesting features were implemented within strace project, including * syscall specification improvements: new syscall classes, regular expressions, conditional expressions; * detailed parsers of netlink protocols; * advanced syscall filtering syntax; * advanced syscall tampering and filtering with Lua; * asinfo: advanced syscall information tool; * gdbserver backend.

In this talk the maintainer of strace will describe these new features and demonstrate what kinds of problems they help to solve.

strace is a diagnostic, debugging and instructional utility for Linux. It is used to monitor interactions between processes and the Linux kernel, which include system calls, signal deliveries, and changes of process state. In 2016, strace has been extended to tamper with tracees using syscall fault injection, making strace also a syscall fault injection tool, the only unprivileged userspace command-line runtime tool of this kind for Linux.

The last summer as a part of strace GSoC 2016 project Nahim El Atmani has implemented a prototype of syscall fault injection - a software testing technique used for improving test coverage of error handling code paths that might otherwise rarely be followed by introducing faults. Now the feature has finally been implemented and is a part of strace 4.15 released in December 2016.

In this talk the maintainer of strace will demonstrate the new feature, describe its implementation, and show examples of real bugs found with its help.