How to execute an object file: Part 3
Dealing with external libraries
In the part 2 of our series we learned how to process relocations in object files in order to properly wire up internal dependencies in the code. In this post we will look into what happens if the code has external dependencies — that is, it tries to call functions from external libraries. As before, we will be building upon the code from part 2. Let's add another function to our toy object file:
obj.c:
#include <stdio.h>
...
void say_hello(void)
{
puts("Hello, world!");
}
In the above scenario our say_hello function now depends on the puts function from the C standard library. To try it out we also need to modify our loader to import the new function and execute it:
loader.c:
...
static void execute_funcs(void)
{
/* pointers to imported functions */
int (*add5)(int);
int (*add10)(int);
const char *(*get_hello)(void);
int (*get_var)(void);
void (*set_var)(int num);
void (*say_hello)(void);
...
say_hello = lookup_function("say_hello");
if (!say_hello) {
fputs("Failed to find say_hello function\n", stderr);
exit(ENOENT);
}
puts("Executing say_hello...");
say_hello();
}
...
Let's run it:
$ gcc -c obj.c
$ gcc -o loader loader.c
$ ./loader
No runtime base address for section
Seems something went Continue reading
Lessons Learned: Fundamentals Haven’t Changed
Here’s another bitter pill to swallow if you desperately want to believe in the magic powers of unicorn dust: laws of physics and networking fundamentals haven’t changed (see also: RFC 1925 Rule 11).
Whenever someone is promising a miracle solution, it’s probably due to them working in marketing or having no clue what they’re talking about (or both)… or it might be another case of adding another layer of abstraction and pretending the problems disappeared because you can’t see them anymore.
You’ll need a Free ipSpace.net Subscription to watch the video.
Lessons Learned: Fundamentals Haven’t Changed
Here’s another bitter pill to swallow if you desperately want to believe in the magic powers of unicorn dust: laws of physics and networking fundamentals haven’t changed (see also: RFC 1925 Rule 11).
Whenever someone is promising a miracle solution, it’s probably due to them working in marketing or having no clue what they’re talking about (or both)… or it might be another case of adding another layer of abstraction and pretending the problems disappeared because you can’t see them anymore.
You’ll need a Free ipSpace.net Subscription to watch the video.
How Artificial Intelligence Will Change IT Jobs
As artificial intelligence grows increasingly powerful and reliable, some IT professionals worry that the technology could gradually make their jobs less meaningful and relevant.IPv6 Buzz 084: Wi-Fi 6E Adoption And IPv6
In this episode of IPv6 Buzz, we compare IPv6 adoption to Wi-Fi 6E adoption (and talk about IPv6 Wi-Fi at large) with guest Tom Hollingsworth of Gestalt IT and Tech Field Day.
The post IPv6 Buzz 084: Wi-Fi 6E Adoption And IPv6 appeared first on Packet Pushers.
IPv6 Buzz 084: Wi-Fi 6E Adoption And IPv6
In this episode of IPv6 Buzz, we compare IPv6 adoption to Wi-Fi 6E adoption (and talk about IPv6 Wi-Fi at large) with guest Tom Hollingsworth of Gestalt IT and Tech Field Day.Native Rust support on Cloudflare Workers
You can now write Cloudflare Workers in 100% Rust, no JavaScript required. Try it out: https://github.com/cloudflare/workers-rs
Cloudflare Workers has long supported the building blocks to run many languages using WebAssembly. However, there has always been a challenging “trampoline” step required to allow languages like Rust to talk to JavaScript APIs such as fetch().
In addition to the sizable amount of boilerplate needed, lots of “off the shelf” bindings between languages don’t include support for Cloudflare APIs such as KV and Durable Objects. What we wanted was a way to write a Worker in idiomatic Rust, quickly, and without needing knowledge of the host JavaScript environment. While we had a nice “starter” template that made it easy enough to pull in some Rust libraries and use them from JavaScript, the barrier was still too high if your goal was to write a full program in Rust and ship it to our edge.
Not anymore!
Introducing the worker crate, available on GitHub and crates.io, which makes Rust developers feel right at home on the Workers platform by running code inside the V8 WebAssembly engine. In the snippet below, you can see how the worker crate does all the heavy Continue reading
HelloKitty: The Victim’s Perspective
In the past few months, we have witnessed several indiscriminate attacks targeting big companies. Whereas years ago different threat actors focused on specific sectors, nowadays the same techniques, tactics, and procedures (e.g., how the perimeter is penetrated, which tools are used for lateral movement) are consistently applied regardless of company size, location, or industry. Target selection is much more dependent on an organization’s IT infrastructure: for example, recent trends show several actors (among them REvil, HelloKitty, or what was known as Darkside) increasingly targeting companies running workloads on VMware ESXi by adding to their ransomware capabilities to gracefully stop virtual machines before encrypting them (see Figure 1).
Figure 1: HelloKitty stopping virtual machines gracefully
Another important trend we have seen growing in the last few months is the use of ransomware to seize sensitive customer data — first by exfiltrating it, then encrypting it, and later pressuring the victim into paying a ransom under the threat of disclosing such data publicly (a technique called “double extortion”). Notable victims include CD Projekt RED, which faced the leak of the source code of some of its most famous video games.
While many threat reports have already dissected the technical Continue reading
netsim-tools Overview
In December 2020, I got sick-and-tired of handcrafting Vagrantfiles and decided to write a tool that would, given a target networking lab topology in a text file, produce the corresponding Vagrantfile for my favorite environment (libvirt on Ubuntu). Nine months later, that idea turned into a pretty comprehensive tool targeting networking engineers who like to work with CLI and text-based configuration files. If you happen to be of the GUI/mouse persuasion, please stop reading; this tool is not for you.
During those nine months, I slowly addressed most of the challenges I always had creating networking labs. Here’s how I would typically approach testing a novel technology or software feature:
netlab Overview
In December 2020, I got sick-and-tired of handcrafting Vagrantfiles and decided to write a tool that would, given a target networking lab topology in a text file, produce the corresponding Vagrantfile for my favorite environment (libvirt on Ubuntu). Nine months later, that idea turned into a pretty comprehensive tool targeting networking engineers who like to work with CLI and text-based configuration files. If you happen to be of the GUI/mouse persuasion, please stop reading; this tool is not for you.
During those nine months, I slowly addressed most of the challenges I always had creating networking labs. Here’s how I would typically approach testing a novel technology or software feature:
Hedge 99
Two things have been top of mind for those who watch the ‘net and global Internet policy—the increasing number of widespread outages, and the logical and physical centralization of the ‘net. How do these things relate to one another? Alban Kwan joins us to discuss the relationship between centralization and widespread outages. You can read Alban’s article on the topic here.
Explore VMware’s Modern App Connectivity Services with Amazon EKS-Anywhere
As enterprises accelerate their application modernization journey, there is a stronger need for running applications across multi-cloud environments. Today, AWS announced General Availability of Amazon EKS-Anywhere, expanding the AWS portfolio to support these use cases.
We are thrilled to integrate with and extend EKS by providing secure connectivity services that work cross-cluster and cross-cloud with VMware’s Modern App Connectivity Services. By delivering these capabilities, applications can enjoy the level of resiliency, scalability, and security needed for enterprise-critical applications.
VMware Modern App Connectivity Services accelerate the path to app modernization by extending connectivity and security between EKS and EKS-D, and to other platforms. Built on cloud-native principles, it enables a set of important use cases that automate the process of connecting, observing, scaling, and better-securing applications.
VMware enables EKS customers to leverage connectivity, resiliency, and security capabilities:
- Application connectivity
Across both multi-cluster and hybrid clouds, in addition to VM environments. This enables discoverability and connectivity between distributed microservices across hybrid EKS, EKS-D, and VMware vSphere environments. - Application resiliency
This enables cluster load balancing level on-prem to communicate with the rest of the customer’s environments both on-prem and on the cloud with this global load balancing solution. - Application security
This enables Continue reading