hush.c

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

	if(cur) {
		if(strcmp(cur->value, value)==0) {
			if(flg_export>0 && cur->flg_export==0)
				cur->flg_export=flg_export;
			else
				result++;
		} else {
			if(cur->flg_read_only) {
				bb_error_msg("%s: readonly variable", name);
				result = -1;
			} else {
				if(flg_export>0 || cur->flg_export>1)
					cur->flg_export=1;
				free(cur->value);

				cur->value = strdup(value);
			}
		}
	} else {
		cur = malloc(sizeof(struct variables));
		if(!cur) {
			result = -1;
		} else {
			cur->name = strdup(name);
			if(cur->name == 0) {
				free(cur);
				result = -1;
			} else {
				struct variables *bottom = top_vars;
				cur->value = strdup(value);
				cur->next = 0;
				cur->flg_export = flg_export;
				cur->flg_read_only = 0;
				while(bottom->next) bottom=bottom->next;
				bottom->next = cur;
			}
		}
	}

	if(result==0 && cur->flg_export==1) {
		*(value-1) = '=';
		result = putenv(name);
	} else {
		free(name);
		if(result>0)            /* equivalent to previous set */
			result = 0;
	}
	return result;
}

static void unset_local_var(const char *name)
{
	struct variables *cur;

	if (name) {
		for (cur = top_vars; cur; cur=cur->next) {
			if(strcmp(cur->name, name)==0)
				break;
		}
		if(cur!=0) {
			struct variables *next = top_vars;
			if(cur->flg_read_only) {
				bb_error_msg("%s: readonly variable", name);
				return;
			} else {
				if(cur->flg_export)
					unsetenv(cur->name);
				free(cur->name);
				free(cur->value);
				while (next->next != cur)
					next = next->next;
				next->next = cur->next;
			}
			free(cur);
		}
	}
}

static int is_assignment(const char *s)
{
	if (s==NULL || !isalpha(*s)) return 0;
	++s;
	while(isalnum(*s) || *s=='_') ++s;
	return *s=='=';
}

/* the src parameter allows us to peek forward to a possible &n syntax
 * for file descriptor duplication, e.g., "2>&1".
 * Return code is 0 normally, 1 if a syntax error is detected in src.
 * Resource errors (in xmalloc) cause the process to exit */
static int setup_redirect(struct p_context *ctx, int fd, redir_type style,
	struct in_str *input)
{
	struct child_prog *child=ctx->child;
	struct redir_struct *redir = child->redirects;
	struct redir_struct *last_redir=NULL;

	/* Create a new redir_struct and drop it onto the end of the linked list */
	while(redir) {
		last_redir=redir;
		redir=redir->next;
	}
	redir = xmalloc(sizeof(struct redir_struct));
	redir->next=NULL;
	redir->word.gl_pathv=NULL;
	if (last_redir) {
		last_redir->next=redir;
	} else {
		child->redirects=redir;
	}

	redir->type=style;
	redir->fd= (fd==-1) ? redir_table[style].default_fd : fd ;

	debug_printf("Redirect type %d%s\n", redir->fd, redir_table[style].descrip);

	/* Check for a '2>&1' type redirect */
	redir->dup = redirect_dup_num(input);
	if (redir->dup == -2) return 1;  /* syntax error */
	if (redir->dup != -1) {
		/* Erik had a check here that the file descriptor in question
		 * is legit; I postpone that to "run time"
		 * A "-" representation of "close me" shows up as a -3 here */
		debug_printf("Duplicating redirect '%d>&%d'\n", redir->fd, redir->dup);
	} else {
		/* We do _not_ try to open the file that src points to,
		 * since we need to return and let src be expanded first.
		 * Set ctx->pending_redirect, so we know what to do at the
		 * end of the next parsed word.
		 */
		ctx->pending_redirect = redir;
	}
	return 0;
}

struct pipe *new_pipe(void) {
	struct pipe *pi;
	pi = xmalloc(sizeof(struct pipe));
	pi->num_progs = 0;
	pi->progs = NULL;
	pi->next = NULL;
	pi->followup = 0;  /* invalid */
	return pi;
}

static void initialize_context(struct p_context *ctx)
{
	ctx->pipe=NULL;
	ctx->pending_redirect=NULL;
	ctx->child=NULL;
	ctx->list_head=new_pipe();
	ctx->pipe=ctx->list_head;
	ctx->w=RES_NONE;
	ctx->stack=NULL;
	ctx->old_flag=0;
	done_command(ctx);   /* creates the memory for working child */
}

/* normal return is 0
 * if a reserved word is found, and processed, return 1
 * should handle if, then, elif, else, fi, for, while, until, do, done.
 * case, function, and select are obnoxious, save those for later.
 */
int reserved_word(o_string *dest, struct p_context *ctx)
{
	struct reserved_combo {
		char *literal;
		int code;
		long flag;
	};
	/* Mostly a list of accepted follow-up reserved words.
	 * FLAG_END means we are done with the sequence, and are ready
	 * to turn the compound list into a command.
	 * FLAG_START means the word must start a new compound list.
	 */
	static struct reserved_combo reserved_list[] = {
		{ "if",    RES_IF,    FLAG_THEN | FLAG_START },
		{ "then",  RES_THEN,  FLAG_ELIF | FLAG_ELSE | FLAG_FI },
		{ "elif",  RES_ELIF,  FLAG_THEN },
		{ "else",  RES_ELSE,  FLAG_FI   },
		{ "fi",    RES_FI,    FLAG_END  },
		{ "for",   RES_FOR,   FLAG_IN   | FLAG_START },
		{ "while", RES_WHILE, FLAG_DO   | FLAG_START },
		{ "until", RES_UNTIL, FLAG_DO   | FLAG_START },
		{ "in",    RES_IN,    FLAG_DO   },
		{ "do",    RES_DO,    FLAG_DONE },
		{ "done",  RES_DONE,  FLAG_END  }
	};
	struct reserved_combo *r;
	for (r=reserved_list;
#define NRES sizeof(reserved_list)/sizeof(struct reserved_combo)
		r<reserved_list+NRES; r++) {
		if (strcmp(dest->data, r->literal) == 0) {
			debug_printf("found reserved word %s, code %d\n",r->literal,r->code);
			if (r->flag & FLAG_START) {
				struct p_context *new = xmalloc(sizeof(struct p_context));
				debug_printf("push stack\n");
				if (ctx->w == RES_IN || ctx->w == RES_FOR) {
					syntax();
					free(new);
					ctx->w = RES_SNTX;
					b_reset(dest);
					return 1;
				}
				*new = *ctx;   /* physical copy */
				initialize_context(ctx);
				ctx->stack=new;
			} else if ( ctx->w == RES_NONE || ! (ctx->old_flag & (1<<r->code))) {
				syntax();
				ctx->w = RES_SNTX;
				b_reset(dest);
				return 1;
			}
			ctx->w=r->code;
			ctx->old_flag = r->flag;
			if (ctx->old_flag & FLAG_END) {
				struct p_context *old;
				debug_printf("pop stack\n");
				done_pipe(ctx,PIPE_SEQ);
				old = ctx->stack;
				old->child->group = ctx->list_head;
				old->child->subshell = 0;
				*ctx = *old;   /* physical copy */
				free(old);
			}
			b_reset (dest);
			return 1;
		}
	}
	return 0;
}

/* normal return is 0.
 * Syntax or xglob errors return 1. */
static int done_word(o_string *dest, struct p_context *ctx)
{
	struct child_prog *child=ctx->child;
	glob_t *glob_target;
	int gr, flags = 0;

	debug_printf("done_word: %s %p\n", dest->data, child);
	if (dest->length == 0 && !dest->nonnull) {
		debug_printf("  true null, ignored\n");
		return 0;
	}
	if (ctx->pending_redirect) {
		glob_target = &ctx->pending_redirect->word;
	} else {
		if (child->group) {
			syntax();
			return 1;  /* syntax error, groups and arglists don't mix */
		}
		if (!child->argv && (ctx->type & FLAG_PARSE_SEMICOLON)) {
			debug_printf("checking %s for reserved-ness\n",dest->data);
			if (reserved_word(dest,ctx)) return ctx->w==RES_SNTX;
		}
		glob_target = &child->glob_result;
 		if (child->argv) flags |= GLOB_APPEND;
	}
	gr = xglob(dest, flags, glob_target);
	if (gr != 0) return 1;

	b_reset(dest);
	if (ctx->pending_redirect) {
		ctx->pending_redirect=NULL;
		if (glob_target->gl_pathc != 1) {
			bb_error_msg("ambiguous redirect");
			return 1;
		}
	} else {
		child->argv = glob_target->gl_pathv;
	}
	if (ctx->w == RES_FOR) {
		done_word(dest,ctx);
		done_pipe(ctx,PIPE_SEQ);
	}
	return 0;
}

/* The only possible error here is out of memory, in which case
 * xmalloc exits. */
static int done_command(struct p_context *ctx)
{
	/* The child is really already in the pipe structure, so
	 * advance the pipe counter and make a new, null child.
	 * Only real trickiness here is that the uncommitted
	 * child structure, to which ctx->child points, is not
	 * counted in pi->num_progs. */
	struct pipe *pi=ctx->pipe;
	struct child_prog *prog=ctx->child;

	if (prog && prog->group == NULL
	         && prog->argv == NULL
	         && prog->redirects == NULL) {
		debug_printf("done_command: skipping null command\n");
		return 0;
	} else if (prog) {
		pi->num_progs++;
		debug_printf("done_command: num_progs incremented to %d\n",pi->num_progs);
	} else {
		debug_printf("done_command: initializing\n");
	}
	pi->progs = xrealloc(pi->progs, sizeof(*pi->progs) * (pi->num_progs+1));

	prog = pi->progs + pi->num_progs;
	prog->redirects = NULL;
	prog->argv = NULL;
	prog->is_stopped = 0;
	prog->group = NULL;
	prog->glob_result.gl_pathv = NULL;
	prog->family = pi;
	prog->sp = 0;
	ctx->child = prog;
	prog->type = ctx->type;

	/* but ctx->pipe and ctx->list_head remain unchanged */
	return 0;
}

static int done_pipe(struct p_context *ctx, pipe_style type)
{
	struct pipe *new_p;
	done_command(ctx);  /* implicit closure of previous command */
	debug_printf("done_pipe, type %d\n", type);
	ctx->pipe->followup = type;
	ctx->pipe->r_mode = ctx->w;
	new_p=new_pipe();
	ctx->pipe->next = new_p;
	ctx->pipe = new_p;
	ctx->child = NULL;
	done_command(ctx);  /* set up new pipe to accept commands */
	return 0;
}

/* peek ahead in the in_str to find out if we have a "&n" construct,
 * as in "2>&1", that represents duplicating a file descriptor.
 * returns either -2 (syntax error), -1 (no &), or the number found.
 */
static int redirect_dup_num(struct in_str *input)
{
	int ch, d=0, ok=0;
	ch = b_peek(input);
	if (ch != '&') return -1;

	b_getch(input);  /* get the & */
	ch=b_peek(input);
	if (ch == '-') {
		b_getch(input);
		return -3;  /* "-" represents "close me" */
	}
	while (isdigit(ch)) {
		d = d*10+(ch-'0');
		ok=1;
		b_getch(input);
		ch = b_peek(input);
	}
	if (ok) return d;

	bb_error_msg("ambiguous redirect");
	return -2;
}

/* If a redirect is immediately preceded by a number, that number is
 * supposed to tell which file descriptor to redirect.  This routine
 * looks for such preceding numbers.  In an ideal world this routine
 * needs to handle all the following classes of redirects...
 *     echo 2>foo     # redirects fd  2 to file "foo", nothing passed to echo
 *     echo 49>foo    # redirects fd 49 to file "foo", nothing passed to echo
 *     echo -2>foo    # redirects fd  1 to file "foo",    "-2" passed to echo
 *     echo 49x>foo   # redirects fd  1 to file "foo",   "49x" passed to echo
 * A -1 output from this program means no valid number was found, so the
 * caller should use the appropriate default for this redirection.
 */
static int redirect_opt_num(o_string *o)
{
	int num;

	if (o->length==0) return -1;
	for(num=0; num<o->length; num++) {
		if (!isdigit(*(o->data+num))) {
			return -1;
		}
	}
	/* reuse num (and save an int) */
	num=atoi(o->data);
	b_reset(o);
	return num;
}

FILE *generate_stream_from_list(struct pipe *head)
{
	FILE *pf;
#if 1
	int pid, channel[2];
	if (pipe(channel)<0) bb_perror_msg_and_die("pipe");
#if !defined(__UCLIBC__) || defined(__ARCH_HAS_MMU__)
	pid=fork();
#else
	pid=vfork();
#endif
	if (pid<0) {
		bb_perror_msg_and_die("fork");
	} else if (pid==0) {
		close(channel[0]);
		if (channel[1] != 1) {
			dup2(channel[1],1);
			close(channel[1]);
		}
#if 0
#define SURROGATE "surrogate response"
		write(1,SURROGATE,sizeof(SURROGATE));
		_exit(run_list(head));
#else
		_exit(run_list_real(head));   /* leaks memory */
#endif
	}
	debug_printf("forked child %d\n",pid);
	close(channel[1]);
	pf = fdopen(channel[0],"r");
	debug_printf("pipe on FILE *%p\n",pf);
#else
	free_pipe_list(head,0);
	pf=popen("echo surrogate response","r");
	debug_printf("started fake pipe on FILE *%p\n",pf);
#endif
	return pf;
}

/* this version hacked for testing purposes */
/* return code is exit status of the process that is run. */
static int process_command_subs(o_string *dest, struct p_context *ctx, struct in_str *input, int subst_end)
{
	int retcode;
	o_string result=NULL_O_STRING;
	struct p_context inner;
	FILE *p;
	struct in_str pipe_str;
	initialize_context(&inner);

	/* recursion to generate command */
	retcode = parse_stream(&result, &inner, input, subst_end);
	if (retcode != 0) return retcode;  /* syntax error or EOF */
	done_word(&result, &inner);
	done_pipe(&inner, PIPE_SEQ);
	b_free(&result);

	p=generate_stream_from_list(inner.list_head);
	if (p==NULL) return 1;
	mark_open(fileno(p));
	setup_file_in_str(&pipe_str, p);

	/* now send results of command back into original context */
	retcode = parse_stream(dest, ctx, &pipe_str, '\0');
	/* XXX In case of a syntax error, should we try to kill the child?
	 * That would be tough to do right, so just read until EOF. */
	if (retcode == 1) {
		while (b_getch(&pipe_str)!=EOF) { /* discard */ };
	}

	debug_printf("done reading from pipe, pclose()ing\n");
	/* This is the step that wait()s for the child.  Should be pretty
	 * safe, since we just read an EOF from its stdout.  We could try
	 * to better, by us