NOTE: we have stopped maintaining the x86 version of xv6, and switched our efforts to the RISC-V version (https://github.com/mit-pdos/xv6-riscv.git)

xv6 is a re-implementation of Dennis Ritchie's and Ken Thompson's Unix Version 6 (v6). xv6 loosely follows the structure and style of v6, but is implemented for a modern x86-based multiprocessor using ANSI C.

ACKNOWLEDGMENTS

xv6 is inspired by John Lions's Commentary on UNIX 6th Edition (Peer to Peer Communications; ISBN: 1-57398-013-7; 1st edition (June 14, 2000)). See also https://pdos.csail.mit.edu/6.828/, which provides pointers to on-line resources for v6.

xv6 borrows code from the following sources: JOS (asm.h, elf.h, mmu.h, bootasm.S, ide.c, console.c, and others) Plan 9 (entryother.S, mp.h, mp.c, lapic.c) FreeBSD (ioapic.c) NetBSD (console.c)

The following people have made contributions: Russ Cox (context switching, locking), Cliff Frey (MP), Xiao Yu (MP), Nickolai Zeldovich, and Austin Clements.

We are also grateful for the bug reports and patches contributed by Silas Boyd-Wickizer, Anton Burtsev, Cody Cutler, Mike CAT, Tej Chajed, eyalz800, Nelson Elhage, Saar Ettinger, Alice Ferrazzi, Nathaniel Filardo, Peter Froehlich, Yakir Goaron,Shivam Handa, Bryan Henry, Jim Huang, Alexander Kapshuk, Anders Kaseorg, kehao95, Wolfgang Keller, Eddie Kohler, Austin Liew, Imbar Marinescu, Yandong Mao, Matan Shabtay, Hitoshi Mitake, Carmi Merimovich, Mark Morrissey, mtasm, Joel Nider, Greg Price, Ayan Shafqat, Eldar Sehayek, Yongming Shen, Cam Tenny, tyfkda, Rafael Ubal, Warren Toomey, Stephen Tu, Pablo Ventura, Xi Wang, Keiichi Watanabe, Nicolas Wolovick, wxdao, Grant Wu, Jindong Zhang, Icenowy Zheng, and Zou Chang Wei.

The code in the files that constitute xv6 is Copyright 2006-2018 Frans Kaashoek, Robert Morris, and Russ Cox.

ERROR REPORTS

We don't process error reports (see note on top of this file).

BUILDING AND RUNNING XV6

To build xv6 on an x86 ELF machine (like Linux or FreeBSD), run "make". On non-x86 or non-ELF machines (like OS X, even on x86), you will need to install a cross-compiler gcc suite capable of producing x86 ELF binaries (see https://pdos.csail.mit.edu/6.828/). Then run "make TOOLPREFIX=i386-jos-elf-". Now install the QEMU PC simulator and run "make qemu".

• kfree panic - cause: inappropriate calculation of flags in page table entry
• TRAP PG_FAULT - cause: values of proc may not properly initialized in all case
• Keep things compressed in first pages when writeing fresh swap file
• Star this repo if you find it helpful

• Added size check in mappages
• Added PGADDRBIT constant in mmu.h
• Added rcr3() in x86.h
• Added control+ 'O' to call procdump
• Added AssertPanic in defs.h
• Added Page Table printing in procdump
• Added Page Mappings printing in procdump
• Added Trap No description printing in trap.c
• Added nulltest user program
• Added q target as clean & qemu-nox in Makefile
• Added modification of PTE_U flags in upper part of page directory in setupkvm
• Added colorfull output in terminal
• Added logging mechanism in defs.h
• Added createSwapFile in proc:fork [ init process doesnot have swapfile ]
• Added removeSwapFile in proc:exit
• Added printing total free pages in proc:procdump
• Added pagetest user program
• Added refactored swapfile operation to swap.c
• Added basic swapfile linking [for new pages allocated] in swap.c
• Sufferred from many trap
• Added time.c in user programs
• Added bit lebel checking in swap metadata[ faaaster]
• Added Null Page Pointer protection
• Added NFU + FIFO page replacement algorithm
• Changed FSSIZE [1000 -> 5000] in params.h
• Tested code for FIFO+NFU ['pageforktest' , 'pagetest' ,'nulltest']
• Tested code for FIFO+NFU ['usertests']
• Changed NFU counter to 12 bit