system-calls

Related to this other question. I am trying to run this simple C program in gem5: int main() { int a=1, b=2; int c=a+b; return c; } And it fails because gem5 doesn't have some syscalls implemented. My question is, why would a simple program like this require syscalls? This should run bare-metal without trouble. Is there a way to compile this to avoid syscalls? I am using arm-linux-gnueabi-gcc -static -DUNIX to compile it. Without syscalls the program cannot exit. The way it works is typically something like this: // Not how it's actually implemented... just a sketch. void _start() { char *

I'm trying to make a custom system call. my system call takes 2 parameters struct buffer **mybuffer & int size . it's imposed any change that happens to **mybuffer should reflect in the user-space, but it seems it doesn't work. so I've seen somewhere else that i can use copy_to_user(void *dest, void *src, int size) to copy data from kernel space to user space. in user-space i have a struct called buffer, also this struct appears the same in the system call. typedef struct buffer { int n; }buffer; int main(void) { buffer **buf = malloc(sizeof(buffer *)); int i = 0 for(;i<8;i++) buf[i] = malloc

In an application I am developing I use splice on Linux for socket-to-socket data transfer. Do other operating systems (specifically at least Windows, OS X and FreeBSD) implement splice or an equivalent solution? Is it possible to imitate socket-to-socket data splice ing on Windows with sendfile ¹ + memmap ¹? ¹ Both exist on Windows under different names which I do not remember. Update You can see the performance improvements of splice vs user space buffers on Linux. DF , DR , F , MF , MR are my application in its different tunneling modes, NX is NGINX web server -p+t uses the Linux system

As i'm writing this command after i shift to the kernel. When i compile it, it wasn't showing any list.Is there any other command to open the list ? open /arch/x86/syscalls/syscall_32.tbl Bug Remove first / character from your file path (as it should be relative path). Check file Now, check that this file exists, using file tool: $ file arch/x86/syscalls/syscall_32.tbl Print file If file exists, you can print it using cat or less commands. E.g.: $ less arch/x86/syscalls/syscall_32.tbl You can also open this file in editor, e.g. using vi command. If file absent This file comes with Linux kernel

I'm trying to intercept the openat() system call on Linux using a custom shared library that I can load via LD_PRELOAD . An example intercept-openat.c has this content: #define _GNU_SOURCE #include <sys/types.h> #include <sys/stat.h> #include <unistd.h> #include <stdio.h> #include <dlfcn.h> int (*_original_openat)(int dirfd, const char *pathname, int flags, mode_t mode); void init(void) __attribute__((constructor)); int openat(int dirfd, const char *pathname, int flags, mode_t mode); void init(void) { _original_openat = (int (*)(int, const char *, int, mode_t)) dlsym(RTLD_NEXT, "openat"); }

I am working in glibc and I need to get the id of the current thread. For this i use syscall(SYS_gettid); Issue is, i am forced to include bits/syscall.h instead of ideal case i.e sys/syscall.h . sys/syscall.h internally calls bits/syscall.h but that is wrapped with #ifndef _LIBC macro. i.e #ifndef _LIBC /* The Linux kernel header file defines macros `__NR_<name>', but some programs expect the traditional form `SYS_<name>'. So in building libc we scan the kernel's list and produce <bits/syscall.h> with macros for all the `SYS_' names. */ # include <bits/syscall.h> #endif also bits/syscall.h