xv6 is a small Unix-like teaching operating system made by MIT for its 6.828 OS course. It is inspired by Unix Version 6.
Questions tagged [xv6]
326 questions
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why fields like limit and base is separately stored in gdt in os?
rt,
for example, in xv6 code mmu.h,
segdesc is designed like this
struct segdesc {
uint lim_15_0 : 16; // Low bits of segment limit
uint base_15_0 : 16; // Low bits of segment base address
uint base_23_16 : 8; // Middle bits of segment base…
minglotus
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How to add a system call to get the count of a particular system call when process invokes it in XV6 OS
Can some one help me in adding a system call called getcount(system call) to XV6? which has an argument system call. when ever a system call is made by the process it should increase the count and should keep track of the count. after the completion…
user3342616
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Scheduler in xv6
I am trying to implement mixture of MLFQ and lottery scheduler in xv6. The problem I am encountering is I am making a function which calculates the total number of processes with high priority in a queue and the sum of their tickets. When I print…
Anmol Yousaf
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how make a new scheduler in xv6?
i am new to XV6 so be patient with me :D .
i want to make a new scheduler and it is a mix of two scheduler the multi-level feedback queue (MLFQ) and another one the lottery scheduler.
The basic idea is simple: Build a two-level scheduler which…
Halawa
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2 answers
How two virtual address spaces can be mapped to the same physical address range?
I think that they might override each other's data.
I understand that two same virtual address spaces can be mapped to physical memory.
Sharon182
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xv6 Scheduler - proc never != 0
Basically, I'm implementing a scheduler for the xv6 kernel that is implementing a multilevel priority queue. I'm having a serious issue I do not understand, the TAs for my course do not understand, and I've missed the deadline for this project, so…
katiea
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Implementing vfork() in xv6
If I want to add my system call vfork(copy on write) what exactly need to be edited in syscall.c? Where would I add my fragment of vfork's code. In short, how would I implement vfork in xv6?
ahmad
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a recursive function to manipulate a given path
I am working on modifying the didactic OS xv6 (written in c) to support symbolic links (AKA shortcuts).
A symbolic link is a file of type T_SYM that contains a path to it's destination.
For doing that, i wrote a recursive function that gets a path…
Eyal
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c6.s081 lab1 xargs：I don't know why the program below can't get the answer?
when I was finishing the c6.s081(2021) lab1 xargs, I found a function from other person which is below:
#include "kernel/types.h"
#include "kernel/param.h"
#include "user/user.h"
#define STDIN_FILENO 0
#define MAXLINE 1024
int main(int argc, char…
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In RISC-V, when will an interrupt be handled?
I learned that every core in RISC-V can handle an interrupt. So when one core is running in u-mode, will it trap into s-mode and handle the interrupt? Or only in s-mode core can handle this interrupt?
I tried debug xv6 os, seems like every uart…
Kevin
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MMIO address unmatched in Xv6 operating system?
I recently found some problems while working on the Xv6 kernel. When the kernel booting up, it initializes the PLIC to receive interrupt signals from the UART, but I found that the address used here is different from definitions in SiFive_U…
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How to Track References in Copy-On-Write VM Mappings
I'm trying to modify xv6-riscv to perform a copy-on-write mapping when executing fork().
Most sources I can find online suggest to keep track of how many processes currently are able to read from a given copy-on-write page in the PTE. Once that…
VanceR
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Forking system calls
#include "kernel/types.h"
#include "kernel/stat.h"
#include "user.h"
#include "kernel/fs.h"
int main(int argc, char *argv[]) {
int i;
int pid1 = fork();
if (pid1 < 0 || argc < 2) {
fprintf(2, "Fork failed.\n");
…
user287102
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xv6 stack dynamic memory management
I'm trying to implement a new dynamic memory logic (malloc/free) in xv6, which has the following behavior.
The main point is that memory blocks will follow LIFO concept, meaning that free() can only free the last block allocated in memory.
when…
galyoss
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Program doesn't finish well after mapping new shared memory pages in xv6
The problem is parent process in xv6 system doesn't enter the exit() function after waiting child to execute. I also made a change to exec() where I mapped the shared structures so that parent and child process points to same page directory (share…
xyz
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