A system call is used by programs to request services from the operating system's kernel.
Questions tagged [system-calls]
3690 questions
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How can I test that a program handles partial read()s and write()s correctly?
It's well-known that the read and write syscalls can operate on fewer bytes than requested. But this is relatively rare and often not tested well. Consider this buggy C program:
#include
int main(void) {
const char *buf = "Hello,…
Joseph Sible-Reinstate Monica
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Problem with hooking ntdll.dll calls
I'm currently working on hooking ntdll.dll calls via dll injection.
At first, I create thread in existing process via CreateRemoteThread() then I load my dll via LoadLibrary and finally hook calls on PROCESS_ATTACH.
Injection works fine, but then I…
qutron
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How can I check if my syscall failed in NASM
I would like to know if anybody has a solution to my problem.
I'm doing a project for school. This project is about creating a function (only in NASM) that uses a syscall (I have to create ft_read which reproduces the behaviour of the real read…
Alexandre de Temmerman
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Get list of fixed drives
How can I get a list of all mount points for physical drives only? I see there is a similar answer on here but this lists all mount points including network shares.
How can I get a listing of all drives on Windows using golang?
Jack bladk
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Using syscall open() to open a file in FUSE
I'm recently working on fuse, but yet still cant have a grasp of how it works since i have very little knowledge about filesystem in linux. One of the most confusing thing is that what will happen if i use syscall open() to open a file within the…
juicyliberty
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ptrace system call returns -1 with errno=0
I am trying to do some very basic stuff using ptrace but I am a getting a really odd behavior.
unsigned long start=strtoul(start_text,NULL,16);
long start_data;
if ((start_data = ptrace(PTRACE_PEEKTEXT,child_pid,(void*)start,NULL))<0){
…
EL_9
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XV6 - Pass parameters to systemcall and get return value
I need to write a system call in XV6 that gets a few integers and a few integer pointers as arguments, and I don't understand how to do it. I read about argint and argptr, but I don't understand how to use them. For example, I don't understand if…
Dani
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strace -c doesn't report exit system calls
I'm working through some homework, and I need to report which system calls a C program makes use of.
I noticed though that exit doesn't show up in strace reports.
#include
int main() {
…
Carcigenicate
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NASM program doesn't print constant integer (macOS)
I try to print b, but it prints nothing. Also I wanted to find length of b to hardcode it (because dws have the same length), but it printed nothing too (that's why I created lenlen — len of blen, so that I can print blen). Don't pay attention to k…
Martian
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Syscall Constant syscall.ENONET Undefined in Go
I tried to run the following bar.go script
package main
import (
"fmt"
"syscall"
)
func main() {
fmt.Printf("%d\n", uintptr(syscall.ENONET))
}
by calling go run bar.go and get this error:
# command-line-arguments
./bar.go:9:29:…
dekauliya
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Comparing Go Win32 syscall and cgo: does it have the same overhead?
In Windows, this is the most common way to call a Win32 function (resumed steps to call GetForegroundWindow function):
dllUser32 := syscall.NewLazyDLL("user32.dll")
GetForegroundWindow := dllUser32.NewProc("GetForegroundWindow")
hwnd, _, _ :=…
rodrigocfd
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Linux syscalls: PTRACE_O_TRACECLONE causes indefinite hanging
I have a binary from which I need to intercept a certain syscall--in this case unlinkat--and make it do nothing. I have the following code which works fine for a single process; however, with PTRACE_O_TRACECLONE added to the ptrace opts, after the…
stuart
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How to change errno value in asm x64
I write assembly for a school project and I'm stuck on a point, i need re rewrite Read in asm, so i got it, but i need to set the errno variable, then my read can return -1 in case of an error and set value of errno to 9 for example. And i don't…
Maxime Crespo
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Unable to make successive system calls to print to STDOUT
I'm attempting to get ahead of my schooling by teaching myself assembly. I created a Hello World that prints the entire string in one go, and as far as I can tell, it works fine:
global _start
section .data
hello db "Hello World", 0xa
section…
Carcigenicate
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My syscall cause segmentation fault (core dumped)
I'm writing a simple syscall based on this tutorial, and boot into the new kernel with my syscall in it, but when I compile a test, and execute it, it cause segmentation fault (core dumped).
My my_syscall.h (hello.c equivalent in the tutorial) looks…
Felis
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