Lions' Commentary on UNIX 6th Edition
Table of Contents
Overview
The most famous suppressed book in computer history! Used as an Operating System textbook at MIT"After 20 years, this is still the best expostion of the workings of a 'real' operating system." — Ken Thompson
Source code listing for the Lions' Commentary in PDF and PostScript
Chapter 5 Two Files
/* * Structure of the coremap and swapmap * arrays. Consists of non-zero count * and base address of that many * contiguous units. * (The coremap unit is 64 bytes, * the swapmap unit is 512 bytes) * The addresses are increasing and * the list is terminated with the * first zero count. */ struct map { char *m_size; char *m_addr; };
5.3 malloc
Algorithm is first fit.
/* * Allocate size units from the given * map. Return the base of the allocated * space. * Algorithm is first fit. */ malloc(mp, size) struct map *mp; { register int a; register struct map *bp; for (bp = mp; bp->m_size; bp++) { if (bp->m_size >= size) { a = bp->m_addr; bp->m_addr =+ size; if ((bp->m_size =- size) == 0) do { bp++; (bp-1)->m_addr = bp->m_addr; } while ((bp-1)->m_size = bp->m_size); return(a); } } return(0); }
5.4 mfree
- 根据地址搜索释放内存的所在位置
- 3 cases：
- 与前面一段合并
- 与后面一段合并
- 插入空内存列表
/* * Free the previously allocated space aa * of size units into the specified map. * Sort aa into map and combine on * one or both ends if possible. */ mfree(mp, size, aa) struct map *mp; { register struct map *bp; register int t; register int a; a = aa; for (bp = mp; bp->m_addr<=a && bp->m_size!=0; bp++); if (bp>mp && (bp-1)->m_addr+(bp-1)->m_size == a) { (bp-1)->m_size =+ size; if (a+size == bp->m_addr) { (bp-1)->m_size =+ bp->m_size; while (bp->m_size) { bp++; (bp-1)->m_addr = bp->m_addr; (bp-1)->m_size = bp->m_size; } } } else { if (a+size == bp->m_addr && bp->m_size) { bp->m_addr =- size; bp->m_size =+ size; } else if (size) do { t = bp->m_addr; bp->m_addr = a; a = t; t = bp->m_size; bp->m_size = size; bp++; } while (size = t); } }
5.6 prf.c
panic--printf--printn--putchar deverror--prdev--printf--printn--putchar
5.10 panic
"update" causes all the large block buffers to be written out. 一旦产生panic，就进入运行idle的死循环。
Chapter 6 Getting Started
main函数
- 创建进程0
- 创建进程1(exec /etc/init)
- sched–>sleep–>switch从进程0调度到进程1
Chapter 7 Processes
The definition for "process" given, "a program in execution".
7.2 The pro Structure
struct proc { char p_stat; char p_flag; char p_pri; /* priority, negative is high */ char p_sig; /* signal number sent to this process */ char p_uid; /* user id, used to direct tty signals */ char p_time; /* resident time for scheduling */ char p_cpu; /* cpu usage for scheduling */ char p_nice; /* nice for scheduling */ int p_ttyp; /* controlling tty */ int p_pid; /* unique process id */ int p_ppid; /* process id of parent */ int p_addr; /* address of swappable image */ int p_size; /* size of swappable image (*64 bytes) */ int p_wchan; /* event process is awaiting */ int *p_textp; /* pointer to text structure */ } proc[NPROC];
p_textp is either null or pointer to an entry in the "text" arary.
/* * Text structure. * One allocated per pure * procedure on swap device. * Manipulated by text.c */ struct text { int x_daddr; /* disk address of segment */ int x_caddr; /* core address, if loaded */ int x_size; /* size (*64) */ int *x_iptr; /* inode of prototype */ char x_count; /* reference count */ char x_ccount; /* number of loaded references */ } text[NTEXT];
7.3 The user Structure
/* * The user structure. * One allocated per process. * Contains all per process data * that doesn't need to be referenced * while the process is swapped. * The user block is USIZE*64 bytes * long; resides at virtual kernel * loc 140000; contains the system * stack per user; is cross referenced * with the proc structure for the * same process. */ struct user { int u_rsav[2]; /* save r5,r6 when exchanging stacks */ int u_fsav[25]; /* save fp registers */ /* rsav and fsav must be first in structure */ char u_segflg; /* flag for IO; user or kernel space */ char u_error; /* return error code */ char u_uid; /* effective user id */ char u_gid; /* effective group id */ char u_ruid; /* real user id */ char u_rgid; /* real group id */ int u_procp; /* pointer to proc structure */ char *u_base; /* base address for IO */ char *u_count; /* bytes remaining for IO */ char *u_offset[2]; /* offset in file for IO */ int *u_cdir; /* pointer to inode of current directory */ char u_dbuf[DIRSIZ]; /* current pathname component */ char *u_dirp; /* current pointer to inode */ struct { /* current directory entry */ int u_ino; char u_name[DIRSIZ]; } u_dent; int *u_pdir; /* inode of parent directory of dirp */ int u_uisa[16]; /* prototype of segmentation addresses */ int u_uisd[16]; /* prototype of segmentation descriptors */ int u_ofile[NOFILE]; /* pointers to file structures of open files */ int u_arg[5]; /* arguments to current system call */ int u_tsize; /* text size (*64) */ int u_dsize; /* data size (*64) */ int u_ssize; /* stack size (*64) */ int u_sep; /* flag for I and D separation */ int u_qsav[2]; /* label variable for quits and interrupts */ int u_ssav[2]; /* label variable for swapping */ int u_signal[NSIG]; /* disposition of signals */ int u_utime; /* this process user time */ int u_stime; /* this process system time */ int u_cutime[2]; /* sum of childs' utimes */ int u_cstime[2]; /* sum of childs' stimes */ int *u_ar0; /* address of users saved R0 */ int u_prof[4]; /* profile arguments */ char u_intflg; /* catch intr from sys */ /* kernel stack per user * extends from u + USIZE*64 * backward not to reach here */ } u;
Chapter 8 Process Management
8.9 swtch
2247: If you check, you will find that none of the procedures which call "swtch" directly examines the value returned here.
Only the procedures which call "newproc" which are interested in this value, because of the way the child process is first activated!
Chapter 9
9.3 Interrupt Handlers
clock pcrint rkintr pcpint klxint lpint klrint