x0nu11byt3

ELF Format Cheatsheet

Introduction

Executable and Linkable Format (ELF), is the default binary format on Linux-based systems.

Compilation

murphypei

#ifndef SAFE_QUEUE
#define SAFE_QUEUE

#include <condition_variable>
#include <mutex>
#include <queue>

// A threadsafe-queue.
template <class T>
class SafeQueue

mcastelino

With seabios

1. QEMU includes bundled option ROMs which are loaded by default unless a device is specifically setup with --romfile="".
2. These options roms are bundled as binaries. The source code for the same can be found at http://ipxe.org/
3. These options roms are useful for example when you want to PXE boot over a virtio-net device.

Here is an example of booting via Network PXE using the option ROM

qemu-system-x86_64 \

wbenny

VMCS field encoding

Values of VMCS fields are encoded as per section VMREAD, VMWRITE, and Encodings of VMCS Field (24.11.2, Intel Manual Volume 3C - May 2018).

This encoding can be transcribed into C:

union vmcs_component_encoding
{
 struct

mcastelino

virtio is a kernel virtual bus. From drivers/virtio/virtio.c:

static struct bus_type virtio_bus = {
	.name  = "virtio",
	.match = virtio_dev_match,
	.dev_groups = virtio_dev_groups,
	.uevent = virtio_uevent,
	.probe = virtio_dev_probe,
	.remove = virtio_dev_remove,

gustavorv86

/**
 * Compile:
 *     gcc -std=gnu11 -Wall -Wextra c_priority_queue_threads.c -o priority_queue_threads -lpthread -lrt
 */

#include <errno.h>
#include <mqueue.h>
#include <fcntl.h>    /* For O_* constants. */
#include <sys/stat.h> /* For mode constants. */

Pulimet

adb help // List all comands

== Adb Server
adb kill-server
adb start-server 

== Adb Reboot
adb reboot
adb reboot recovery 
adb reboot-bootloader

mcastelino

Tracing QEMU-KVM Interactions

But default in linux you can figure out how many times and for what reasons there is a VM Exit from a VM into the kvm kernel module. However given the ubiquity of vhost and the ability of kvm to emulate most device models directly in the kernel, most of those VM exits do not result in a transition from host kernel into the QEMU. The transitions from VM -> kvm -> QEMU are typically the most expensive.

Here we try to figure out how many of the VM Exits result in the invocation of QEMU.

Tracking VM-KVM Interactions

This can be done very simply with perf

laoar

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/init.h> 
#include <linux/fs.h> 
#include <linux/mm.h> 
#include <asm/uaccess.h>

#define MAX_SIZE (PAGE_SIZE * 2)   /* max size mmaped to userspace */
#define DEVICE_NAME "mchar"

BrotherJing

#include<linux/module.h>
#include<linux/kernel.h>
#include<linux/string.h>
#include<linux/vmalloc.h>
#include<linux/mm.h>
#include<linux/init.h>
#include<linux/proc_fs.h>
#include<linux/sched.h>
#include<linux/uaccess.h>
#include<linux/fs.h>