system-calls

The Mmap() syscall in the x/sys/unix package in Golang returns a []byte type, while the underlying syscall actually returns a pointer. How does it do this? More specifically, in this package by a Golang developer, the VirtualAlloc function simply returns a pointer. How can this be converted to a byte slice, the same way as it's done in the Unix package? Using the unsafe package you can do the same thing golang.org/x/sys/unix does in the Mmap method of its unexported mmapper type: // Slice memory layout var sl = struct { addr uintptr len int cap int }{addr, length, length} // Use unsafe to turn

I need to add an own system call to the Raspbian Linux Kernel. Now I am stuck after searching for about 2 days to find a solution. To add a system call, I am basically following the general outline ( http://elinux.org/RPi_Kernel_Compilation ) using the kernel sources from the following git repo: git://github.com/raspberrypi/tools.git I have installed a cross-compile environment using crosstool-ng ( http://www.kitware.com/blog/home/post/426 ). All these above works. I am able to compile and deploy a new kernel. I am furthermore able to cross-compile for the Raspbian. I am trying to add a 'hello

Okay so I am trying to teach myself on how to do signalling, and I came across a hiccup and I can't figure out what I'm doing wrong. What is going on right now is: it is executing the parent then goes to child and then back to parent.. It's not doing what I want it to do which is execute the parent (which the user defines the amount of time it runs) then kills it then go to child and run itself at the same amount of time. #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <signal.h> #include <sys/types.h> // for wait #include <sys/wait.h> // for wait void action(int); void

I was using the following code which actually gets me the contents in the registers (eax, ebx, ecx) whenever a open system call is called. Now after a lot of struggle I understood what the values signify from this Question . ebx contains the pointer to filename. But when I try to access it I was getting a segmentation fault. Where am I going wrong? The code can be accessed from the here Every process has its own address space. An address obtained from another process will not be valid in yours. One way to read memory in the other process would be to use PTRACE_PEEKDATA . On Linux, another way

i have been trying to undertand the system calls, and want to understand how set_tid_address works. bascially from what i have read is that it returns the pid of the program or process which is executed. I have tested this with ls, however with some commands like uptime, top etc i dont see set_tid_address being used. Why is that? The clone() syscall can take a CLONE_CHILD_CLEARTID flag, that the value at child_tidptr (another clone() argument) gets cleared and an associated futex signal a wake-up when the child thread exits. This is used to implement pthread_join() (the parent thread waits on

I was checking out clock() on cplusplus.com . Their example involves making the process wait for a second and then output a line, in a loop until 10 seconds have ellapsed. I need to do something similar in the homework assignment I'm working on. What I was wondering was this: if I just send my program into a loop, isn't that using system resources to just spin me around? In this case, wouldn't a system call be better? Thanks for your help! Yes, using a system call or library function like sleep() is much better. That clock() example is just meant to just show how to correctly call the function

I am using Ubuntu Linux to write two programs. I am attempting to change the value of an integer from another process. My first process (A) is a simple program that loops forever and displays the value to the screen. This program works as intended and simply displays the value -1430532899 (0xAABBCCDD) to the screen. #include <stdio.h> int main() { //The needle that I am looking for to change from another process int x = 0xAABBCCDD; //Loop forever printing out the value of x int counter = 0; while(1==1) { while(counter<100000000) { counter++; } counter = 0; printf("%d",x); fflush(stdout); }