hush.c

shell-HHARM9200.rar 华恒 AT91rm9200 中Busybox shell的源代码

/* vi: set sw=4 ts=4: */
/*
 * sh.c -- a prototype Bourne shell grammar parser
 *      Intended to follow the original Thompson and Ritchie
 *      "small and simple is beautiful" philosophy, which
 *      incidentally is a good match to today's BusyBox.
 *
 * Copyright (C) 2000,2001  Larry Doolittle  <[e-mail]>
 *
 * Credits:
 *      The parser routines proper are all original material, first
 *      written Dec 2000 and Jan 2001 by Larry Doolittle.  The
 *      execution engine, the builtins, and much of the underlying
 *      support has been adapted from busybox-0.49pre's lash, which is
 *      Copyright (C) 1999-2004 by Erik Andersen <[e-mail]>
 *      written by Erik Andersen <[e-mail]>.  That, in turn,
 *      is based in part on ladsh.c, by Michael K. Johnson and Erik W.
 *      Troan, which they placed in the public domain.  I don't know
 *      how much of the Johnson/Troan code has survived the repeated
 *      rewrites.
 *
 * Other credits:
 *      simple_itoa() was lifted from boa-0.93.15
 *      b_addchr() derived from similar w_addchar function in glibc-2.2
 *      setup_redirect(), redirect_opt_num(), and big chunks of main()
 *        and many builtins derived from contributions by Erik Andersen
 *      miscellaneous bugfixes from Matt Kraai
 *
 * There are two big (and related) architecture differences between
 * this parser and the lash parser.  One is that this version is
 * actually designed from the ground up to understand nearly all
 * of the Bourne grammar.  The second, consequential change is that
 * the parser and input reader have been turned inside out.  Now,
 * the parser is in control, and asks for input as needed.  The old
 * way had the input reader in control, and it asked for parsing to
 * take place as needed.  The new way makes it much easier to properly
 * handle the recursion implicit in the various substitutions, especially
 * across continuation lines.
 *
 * Bash grammar not implemented: (how many of these were in original sh?)
 *      $@ (those sure look like weird quoting rules)
 *      $_
 *      ! negation operator for pipes
 *      &> and >& redirection of stdout+stderr
 *      Brace Expansion
 *      Tilde Expansion
 *      fancy forms of Parameter Expansion
 *      aliases
 *      Arithmetic Expansion
 *      <(list) and >(list) Process Substitution
 *      reserved words: case, esac, select, function
 *      Here Documents ( << word )
 *      Functions
 * Major bugs:
 *      job handling woefully incomplete and buggy
 *      reserved word execution woefully incomplete and buggy
 * to-do:
 *      port selected bugfixes from post-0.49 busybox lash - done?
 *      finish implementing reserved words: for, while, until, do, done
 *      change { and } from special chars to reserved words
 *      builtins: break, continue, eval, return, set, trap, ulimit
 *      test magic exec
 *      handle children going into background
 *      clean up recognition of null pipes
 *      check setting of global_argc and global_argv
 *      control-C handling, probably with longjmp
 *      follow IFS rules more precisely, including update semantics
 *      figure out what to do with backslash-newline
 *      explain why we use signal instead of sigaction
 *      propagate syntax errors, die on resource errors?
 *      continuation lines, both explicit and implicit - done?
 *      memory leak finding and plugging - done?
 *      more testing, especially quoting rules and redirection
 *      document how quoting rules not precisely followed for variable assignments
 *      maybe change map[] to use 2-bit entries
 *      (eventually) remove all the printf's
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
#include <ctype.h>     /* isalpha, isdigit */
#include <unistd.h>    /* getpid */
#include <stdlib.h>    /* getenv, atoi */
#include <string.h>    /* strchr */
#include <stdio.h>     /* popen etc. */
#include <glob.h>      /* glob, of course */
#include <stdarg.h>    /* va_list */
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>    /* should be pretty obvious */

#include <sys/stat.h>  /* ulimit */
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>

/* #include <dmalloc.h> */
/* #define DEBUG_SHELL */

#if 1
#include "busybox.h"
#include "cmdedit.h"
#else
#define bb_applet_name "hush"
#include "standalone.h"
#define hush_main main
#undef CONFIG_FEATURE_SH_FANCY_PROMPT
#define BB_BANNER
#endif
#define SPECIAL_VAR_SYMBOL 03
#define FLAG_EXIT_FROM_LOOP 1
#define FLAG_PARSE_SEMICOLON (1 << 1)		/* symbol ';' is special for parser */
#define FLAG_REPARSING		 (1 << 2)		/* >=2nd pass */

typedef enum {
	REDIRECT_INPUT     = 1,
	REDIRECT_OVERWRITE = 2,
	REDIRECT_APPEND    = 3,
	REDIRECT_HEREIS    = 4,
	REDIRECT_IO        = 5
} redir_type;

/* The descrip member of this structure is only used to make debugging
 * output pretty */
struct {int mode; int default_fd; char *descrip;} redir_table[] = {
	{ 0,                         0, "()" },
	{ O_RDONLY,                  0, "<"  },
	{ O_CREAT|O_TRUNC|O_WRONLY,  1, ">"  },
	{ O_CREAT|O_APPEND|O_WRONLY, 1, ">>" },
	{ O_RDONLY,                 -1, "<<" },
	{ O_RDWR,                    1, "<>" }
};

typedef enum {
	PIPE_SEQ = 1,
	PIPE_AND = 2,
	PIPE_OR  = 3,
	PIPE_BG  = 4,
} pipe_style;

/* might eventually control execution */
typedef enum {
	RES_NONE  = 0,
	RES_IF    = 1,
	RES_THEN  = 2,
	RES_ELIF  = 3,
	RES_ELSE  = 4,
	RES_FI    = 5,
	RES_FOR   = 6,
	RES_WHILE = 7,
	RES_UNTIL = 8,
	RES_DO    = 9,
	RES_DONE  = 10,
	RES_XXXX  = 11,
	RES_IN    = 12,
	RES_SNTX  = 13
} reserved_style;
#define FLAG_END   (1<<RES_NONE)
#define FLAG_IF    (1<<RES_IF)
#define FLAG_THEN  (1<<RES_THEN)
#define FLAG_ELIF  (1<<RES_ELIF)
#define FLAG_ELSE  (1<<RES_ELSE)
#define FLAG_FI    (1<<RES_FI)
#define FLAG_FOR   (1<<RES_FOR)
#define FLAG_WHILE (1<<RES_WHILE)
#define FLAG_UNTIL (1<<RES_UNTIL)
#define FLAG_DO    (1<<RES_DO)
#define FLAG_DONE  (1<<RES_DONE)
#define FLAG_IN    (1<<RES_IN)
#define FLAG_START (1<<RES_XXXX)

/* This holds pointers to the various results of parsing */
struct p_context {
	struct child_prog *child;
	struct pipe *list_head;
	struct pipe *pipe;
	struct redir_struct *pending_redirect;
	reserved_style w;
	int old_flag;				/* for figuring out valid reserved words */
	struct p_context *stack;
	int type;			/* define type of parser : ";$" common or special symbol */
	/* How about quoting status? */
};

struct redir_struct {
	redir_type type;			/* type of redirection */
	int fd;						/* file descriptor being redirected */
	int dup;					/* -1, or file descriptor being duplicated */
	struct redir_struct *next;	/* pointer to the next redirect in the list */
	glob_t word;				/* *word.gl_pathv is the filename */
};

struct child_prog {
	pid_t pid;					/* 0 if exited */
	char **argv;				/* program name and arguments */
	struct pipe *group;			/* if non-NULL, first in group or subshell */
	int subshell;				/* flag, non-zero if group must be forked */
	struct redir_struct *redirects;	/* I/O redirections */
	glob_t glob_result;			/* result of parameter globbing */
	int is_stopped;				/* is the program currently running? */
	struct pipe *family;		/* pointer back to the child's parent pipe */
	int sp;				/* number of SPECIAL_VAR_SYMBOL */
	int type;
};

struct pipe {
	int jobid;					/* job number */
	int num_progs;				/* total number of programs in job */
	int running_progs;			/* number of programs running */
	char *text;					/* name of job */
	char *cmdbuf;				/* buffer various argv's point into */
	pid_t pgrp;					/* process group ID for the job */
	struct child_prog *progs;	/* array of commands in pipe */
	struct pipe *next;			/* to track background commands */
	int stopped_progs;			/* number of programs alive, but stopped */
	int job_context;			/* bitmask defining current context */
	pipe_style followup;		/* PIPE_BG, PIPE_SEQ, PIPE_OR, PIPE_AND */
	reserved_style r_mode;		/* supports if, for, while, until */
};

struct close_me {
	int fd;
	struct close_me *next;
};

struct variables {
	char *name;
	char *value;
	int flg_export;
	int flg_read_only;
	struct variables *next;
};

/* globals, connect us to the outside world
 * the first three support $?, $#, and $1 */
char **global_argv;
unsigned int global_argc;
unsigned int last_return_code;
extern char **environ; /* This is in <unistd.h>, but protected with __USE_GNU */

/* "globals" within this file */
static char *ifs;
static char map[256];
static int fake_mode;
static int interactive;
static struct close_me *close_me_head;
static const char *cwd;
static struct pipe *job_list;
static unsigned int last_bg_pid;
static unsigned int last_jobid;
static unsigned int shell_terminal;
static char *PS1;
static char *PS2;
struct variables shell_ver = { "HUSH_VERSION", "0.01", 1, 1, 0 };
struct variables *top_vars = &shell_ver;


#define B_CHUNK (100)
#define B_NOSPAC 1

typedef struct {
	char *data;
	int length;
	int maxlen;
	int quote;
	int nonnull;
} o_string;
#define NULL_O_STRING {NULL,0,0,0,0}
/* used for initialization:
	o_string foo = NULL_O_STRING; */

/* I can almost use ordinary FILE *.  Is open_memstream() universally
 * available?  Where is it documented? */
struct in_str {
	const char *p;
	char peek_buf[2];
	int __promptme;
	int promptmode;
	FILE *file;
	int (*get) (struct in_str *);
	int (*peek) (struct in_str *);
};
#define b_getch(input) ((input)->get(input))
#define b_peek(input) ((input)->peek(input))

#define JOB_STATUS_FORMAT "[%d] %-22s %.40s\n"

struct built_in_command {
	char *cmd;					/* name */
	char *descr;				/* description */
	int (*function) (struct child_prog *);	/* function ptr */
};

/* belongs in busybox.h */
static inline int max(int a, int b) {
	return (a>b)?a:b;
}

/* This should be in utility.c */
#ifdef DEBUG_SHELL
static void debug_printf(const char *format, ...)
{
	va_list args;
	va_start(args, format);
	vfprintf(stderr, format, args);
	va_end(args);
}
#else
static inline void debug_printf(const char *format, ...) { }
#endif
#define final_printf debug_printf

static void __syntax(char *file, int line) {
	bb_error_msg("syntax error %s:%d", file, line);
}
#define syntax() __syntax(__FILE__, __LINE__)

/* Index of subroutines: */
/*   function prototypes for builtins */
static int builtin_cd(struct child_prog *child);
static int builtin_env(struct child_prog *child);
static int builtin_eval(struct child_prog *child);
static int builtin_exec(struct child_prog *child);
static int builtin_exit(struct child_prog *child);
static int builtin_export(struct child_prog *child);
static int builtin_fg_bg(struct child_prog *child);
static int builtin_help(struct child_prog *child);
static int builtin_jobs(struct child_prog *child);
static int builtin_pwd(struct child_prog *child);
static int builtin_read(struct child_prog *child);
static int builtin_set(struct child_prog *child);
static int builtin_shift(struct child_prog *child);
static int builtin_source(struct child_prog *child);
static int builtin_umask(struct child_prog *child);
static int builtin_unset(struct child_prog *child);
static int builtin_not_written(struct child_prog *child);
/*   o_string manipulation: */
static int b_check_space(o_string *o, int len);
static int b_addchr(o_string *o, int ch);
static void b_reset(o_string *o);
static int b_addqchr(o_string *o, int ch, int quote);
static int b_adduint(o_string *o, unsigned int i);
/*  in_str manipulations: */
static int static_get(struct in_str *i);
static int static_peek(struct in_str *i);
static int file_get(struct in_str *i);
static int file_peek(struct in_str *i);
static void setup_file_in_str(struct in_str *i, FILE *f);
static void setup_string_in_str(struct in_str *i, const char *s);
/*  close_me manipulations: */
static void mark_open(int fd);
static void mark_closed(int fd);
static void close_all(void);
/*  "run" the final data structures: */
static char *indenter(int i);
static int free_pipe_list(struct pipe *head, int indent);
static int free_pipe(struct pipe *pi, int indent);
/*  really run the final data structures: */
static int setup_redirects(struct child_prog *prog, int squirrel[]);
static int run_list_real(struct pipe *pi);
static void pseudo_exec(struct child_prog *child) __attribute__ ((noreturn));
static int run_pipe_real(struct pipe *pi);
/*   extended glob support: */
static int globhack(const char *src, int flags, glob_t *pglob);
static int glob_needed(const char *s);
static int xglob(o_string *dest, int flags, glob_t *pglob);
/*   variable assignment: */
static int is_assignment(const char *s);
/*   data structure manipulation: */
static int setup_redirect(struct p_context *ctx, int fd, redir_type style, struct in_str *input);
static void initialize_context(struct p_context *ctx);
static int done_word(o_string *dest, struct p_context *ctx);
static int done_command(struct p_context *ctx);
static int done_pipe(struct p_context *ctx, pipe_style type);
/*   primary string parsing: */
static int redirect_dup_num(struct in_str *input);
static int redirect_opt_num(o_string *o);
static int process_command_subs(o_string *dest, struct p_context *ctx, struct in_str *input, int subst_end);
static int parse_group(o_string *dest, struct p_context *ctx, struct in_str *input, int ch);
static char *lookup_param(char *src);
static char *make_string(char **inp);
static int handle_dollar(o_string *dest, struct p_context *ctx, struct in_str *input);
static int parse_string(o_string *dest, struct p_context *ctx, const char *src);
static int parse_stream(o_string *dest, struct p_context *ctx, struct in_str *input0, int end_trigger);
/*   setup: */
static int parse_stream_outer(struct in_str *inp, int flag);
static int parse_string_outer(const char *s, int flag);
static int parse_file_outer(FILE *f);
/*   job management: */
static int checkjobs(struct pipe* fg_pipe);
static void insert_bg_job(struct pipe *pi);
static void remove_bg_job(struct pipe *pi);
/*     local variable support */
static char **make_list_in(char **inp, char *name);
static char *insert_var_value(char *inp);
static char *get_local_var(const char *var);
static void  unset_local_var(const char *name);
static int set_local_var(const char *s, int flg_export);

/* Table of built-in functions.  They can be forked or not, depending on
 * context: within pipes, they fork.  As simple commands, they do not.
 * When used in non-forking context, they can change global variables
 * in the parent shell process.  If forked, of course they can not.
 * For example, 'unset foo | whatever' will parse and run, but foo will
 * still be set at the end. */
static struct built_in_command bltins[] = {
	{"bg", "Resume a job in the background", builtin_fg_bg},
	{"break", "Exit for, while or until loop", builtin_not_written},
	{"cd", "Change working directory", builtin_cd},
	{"continue", "Continue for, while or until loop", builtin_not_written},
	{"env", "Print all environment variables", builtin_env},
	{"eval", "Construct and run shell command", builtin_eval},
	{"exec", "Exec command, replacing this shell with the exec'd process",
		builtin_exec},
	{"exit", "Exit from shell()", builtin_exit},
	{"export", "Set environment variable", builtin_export},
	{"fg", "Bring job into the foreground", builtin_fg_bg},
	{"jobs", "Lists the active jobs", builtin_jobs},
	{"pwd", "Print current directory", builtin_pwd},
	{"read", "Input environment variable", builtin_read},
	{"return", "Return from a function", builtin_not_written},
	{"set", "Set/unset shell local variables", builtin_set},
	{"shift", "Shift positional parameters", builtin_shift},
	{"trap", "Trap signals", builtin_not_written},
	{"ulimit","Controls resource limits", builtin_not_written},
	{"umask","Sets file creation mask", builtin_umask},
	{"unset", "Unset environment variable", builtin_unset},
	{".", "Source-in and run commands in a file", builtin_source},
	{"help", "List shell built-in commands", builtin_help},
	{NULL, NULL, NULL}
};

static const char *set_cwd(void)
{
	if(cwd==bb_msg_unknown)
		cwd = NULL;     /* xgetcwd(arg) called free(arg) */
	cwd = xgetcwd((char *)cwd);
	if (!cwd)
		cwd = bb_msg_unknown;
	return cwd;
}

/* built-in 'eval' handler */
static int builtin_eval(struct child_prog *child)
{
	char *str = NULL;
	int rcode = EXIT_SUCCESS;

	if (child->argv[1]) {
		str = make_string(child->argv + 1);
		parse_string_outer(str, FLAG_EXIT_FROM_LOOP |
					FLAG_PARSE_SEMICOLON);
		free(str);
		rcode = last_return_code;
	}