libbb: introduce and use nonblock_safe_read(). Yay!
Our shells are immune from this nasty O_NONBLOCK now! function old new delta nonblock_safe_read - 78 +78 file_get 276 295 +19 generateMTFValues 428 435 +7 read_line_input 1776 1772 -4 preadbuffer 543 450 -93 ------------------------------------------------------------------------------ (add/remove: 1/0 grow/shrink: 2/2 up/down: 104/-97) Total: 7 bytes text data bss dec hex filename 615190 715 23924 639829 9c355 busybox_old 615168 715 23924 639807 9c33f busybox_unstripped
This commit is contained in:
parent
ae86a338b8
commit
e376d454bb
@ -475,6 +475,7 @@ extern void *xzalloc(size_t size);
|
||||
extern void *xrealloc(void *old, size_t size);
|
||||
|
||||
extern ssize_t safe_read(int fd, void *buf, size_t count);
|
||||
extern ssize_t nonblock_safe_read(int fd, void *buf, size_t count);
|
||||
extern ssize_t full_read(int fd, void *buf, size_t count);
|
||||
extern void xread(int fd, void *buf, size_t count);
|
||||
extern unsigned char xread_char(int fd);
|
||||
@ -482,6 +483,7 @@ extern unsigned char xread_char(int fd);
|
||||
extern char *reads(int fd, char *buf, size_t count);
|
||||
// Read one line a-la fgets. Reads byte-by-byte.
|
||||
// Useful when it is important to not read ahead.
|
||||
// Bytes are appended to pfx (which must be malloced, or NULL).
|
||||
extern char *xmalloc_reads(int fd, char *pfx);
|
||||
extern ssize_t read_close(int fd, void *buf, size_t count);
|
||||
extern ssize_t open_read_close(const char *filename, void *buf, size_t count);
|
||||
|
@ -1408,9 +1408,9 @@ int read_line_input(const char *prompt, char *command, int maxsize, line_input_t
|
||||
parse_and_put_prompt(prompt);
|
||||
|
||||
while (1) {
|
||||
fflush(stdout);
|
||||
fflush(NULL);
|
||||
|
||||
if (safe_read(STDIN_FILENO, &c, 1) < 1) {
|
||||
if (nonblock_safe_read(STDIN_FILENO, &c, 1) < 1) {
|
||||
/* if we can't read input then exit */
|
||||
goto prepare_to_die;
|
||||
}
|
||||
|
56
libbb/read.c
56
libbb/read.c
@ -20,6 +20,58 @@ ssize_t safe_read(int fd, void *buf, size_t count)
|
||||
return n;
|
||||
}
|
||||
|
||||
/* Suppose that you are a shell. You start child processes.
|
||||
* They work and eventually exit. You want to get user input.
|
||||
* You read stdin. But what happens if last child switched
|
||||
* its stdin into O_NONBLOCK mode?
|
||||
*
|
||||
* *** SURPRISE! It will affect the parent too! ***
|
||||
* *** BIG SURPRISE! It stays even after child exits! ***
|
||||
*
|
||||
* This is a design bug in UNIX API.
|
||||
* fcntl(0, F_SETFL, fcntl(0, F_GETFL, 0) | O_NONBLOCK);
|
||||
* will set nonblocking mode not only on _your_ stdin, but
|
||||
* also on stdin of your parent, etc.
|
||||
*
|
||||
* In general,
|
||||
* fd2 = dup(fd1);
|
||||
* fcntl(fd2, F_SETFL, fcntl(fd2, F_GETFL, 0) | O_NONBLOCK);
|
||||
* sets both fd1 and fd2 to O_NONBLOCK. This includes cases
|
||||
* where duping is done implicitly by fork() etc.
|
||||
*
|
||||
* We need
|
||||
* fcntl(fd2, F_SETFD, fcntl(fd2, F_GETFD, 0) | O_NONBLOCK);
|
||||
* (note SETFD, not SETFL!) but such thing doesn't exist.
|
||||
*
|
||||
* Alternatively, we need nonblocking_read(fd, ...) which doesn't
|
||||
* require O_NONBLOCK dance at all. Actually, it exists:
|
||||
* n = recv(fd, buf, len, MSG_DONTWAIT);
|
||||
* "MSG_DONTWAIT:
|
||||
* Enables non-blocking operation; if the operation
|
||||
* would block, EAGAIN is returned."
|
||||
* but recv() works only for sockets!
|
||||
*
|
||||
* So far I don't see any good solution, I can only propose
|
||||
* that affected readers should be careful and use this routine,
|
||||
* which detects EAGAIN and uses poll() to wait on the fd.
|
||||
* Thanksfully, poll() doesn't give rat's ass about O_NONBLOCK flag.
|
||||
*/
|
||||
ssize_t nonblock_safe_read(int fd, void *buf, size_t count)
|
||||
{
|
||||
struct pollfd pfd[1];
|
||||
ssize_t n;
|
||||
|
||||
while (1) {
|
||||
n = safe_read(fd, buf, count);
|
||||
if (n >= 0 || errno != EAGAIN)
|
||||
return n;
|
||||
/* fd is in O_NONBLOCK mode. Wait using poll and repeat */
|
||||
pfd[0].fd = fd;
|
||||
pfd[0].events = POLLIN;
|
||||
safe_poll(pfd, 1, -1);
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Read all of the supplied buffer from a file.
|
||||
* This does multiple reads as necessary.
|
||||
@ -93,6 +145,7 @@ char *reads(int fd, char *buffer, size_t size)
|
||||
|
||||
// Read one line a-la fgets. Reads byte-by-byte.
|
||||
// Useful when it is important to not read ahead.
|
||||
// Bytes are appended to pfx (which must be malloced, or NULL).
|
||||
char *xmalloc_reads(int fd, char *buf)
|
||||
{
|
||||
char *p;
|
||||
@ -106,7 +159,8 @@ char *xmalloc_reads(int fd, char *buf)
|
||||
p = buf + sz;
|
||||
sz += 128;
|
||||
}
|
||||
if (safe_read(fd, p, 1) != 1) { /* EOF/error */
|
||||
/* nonblock_safe_read() because we are used by e.g. shells */
|
||||
if (nonblock_safe_read(fd, p, 1) != 1) { /* EOF/error */
|
||||
if (p == buf) {
|
||||
/* we read nothing [and buf was NULL initially] */
|
||||
free(buf);
|
||||
|
11
shell/ash.c
11
shell/ash.c
@ -5428,7 +5428,7 @@ expbackq(union node *cmd, int quoted, int quotes)
|
||||
read:
|
||||
if (in.fd < 0)
|
||||
break;
|
||||
i = safe_read(in.fd, buf, sizeof(buf));
|
||||
i = nonblock_safe_read(in.fd, buf, sizeof(buf));
|
||||
TRACE(("expbackq: read returns %d\n", i));
|
||||
if (i <= 0)
|
||||
break;
|
||||
@ -8678,7 +8678,7 @@ preadfd(void)
|
||||
retry:
|
||||
#if ENABLE_FEATURE_EDITING
|
||||
if (!iflag || parsefile->fd)
|
||||
nr = safe_read(parsefile->fd, buf, BUFSIZ - 1);
|
||||
nr = nonblock_safe_read(parsefile->fd, buf, BUFSIZ - 1);
|
||||
else {
|
||||
#if ENABLE_FEATURE_TAB_COMPLETION
|
||||
line_input_state->path_lookup = pathval();
|
||||
@ -8700,9 +8700,11 @@ preadfd(void)
|
||||
}
|
||||
}
|
||||
#else
|
||||
nr = safe_read(parsefile->fd, buf, BUFSIZ - 1);
|
||||
nr = nonblock_safe_read(parsefile->fd, buf, BUFSIZ - 1);
|
||||
#endif
|
||||
|
||||
#if 0
|
||||
/* nonblock_safe_read() handles this problem */
|
||||
if (nr < 0) {
|
||||
if (parsefile->fd == 0 && errno == EWOULDBLOCK) {
|
||||
int flags = fcntl(0, F_GETFL);
|
||||
@ -8715,6 +8717,7 @@ preadfd(void)
|
||||
}
|
||||
}
|
||||
}
|
||||
#endif
|
||||
return nr;
|
||||
}
|
||||
|
||||
@ -11801,7 +11804,7 @@ readcmd(int argc, char **argv)
|
||||
backslash = 0;
|
||||
STARTSTACKSTR(p);
|
||||
do {
|
||||
if (read(0, &c, 1) != 1) {
|
||||
if (nonblock_safe_read(0, &c, 1) != 1) {
|
||||
status = 1;
|
||||
break;
|
||||
}
|
||||
|
@ -1273,10 +1273,10 @@ static void get_user_input(struct in_str *i)
|
||||
prompt_str = setup_prompt_string(i->promptmode);
|
||||
#if ENABLE_FEATURE_EDITING
|
||||
/* Enable command line editing only while a command line
|
||||
* is actually being read; otherwise, we'll end up bequeathing
|
||||
* atexit() handlers and other unwanted stuff to our
|
||||
* child processes (rob@sysgo.de) */
|
||||
r = read_line_input(prompt_str, user_input_buf, BUFSIZ-1, line_input_state);
|
||||
* is actually being read */
|
||||
do {
|
||||
r = read_line_input(prompt_str, user_input_buf, BUFSIZ-1, line_input_state);
|
||||
} while (r == 0); /* repeat if Ctrl-C */
|
||||
i->eof_flag = (r < 0);
|
||||
if (i->eof_flag) { /* EOF/error detected */
|
||||
user_input_buf[0] = EOF; /* yes, it will be truncated, it's ok */
|
||||
|
@ -42,6 +42,7 @@
|
||||
# define xmalloc(size) malloc(size)
|
||||
# define msh_main(argc,argv) main(argc,argv)
|
||||
# define safe_read(fd,buf,count) read(fd,buf,count)
|
||||
# define nonblock_safe_read(fd,buf,count) read(fd,buf,count)
|
||||
# define NOT_LONE_DASH(s) ((s)[0] != '-' || (s)[1])
|
||||
# define LONE_CHAR(s,c) ((s)[0] == (c) && !(s)[1])
|
||||
# define ATTRIBUTE_NORETURN __attribute__ ((__noreturn__))
|
||||
@ -3376,7 +3377,7 @@ static int doread(struct op *t)
|
||||
}
|
||||
for (wp = t->words + 1; *wp; wp++) {
|
||||
for (cp = global_env.linep; !nl && cp < elinep - 1; cp++) {
|
||||
nb = read(0, cp, sizeof(*cp));
|
||||
nb = nonblock_safe_read(0, cp, sizeof(*cp));
|
||||
if (nb != sizeof(*cp))
|
||||
break;
|
||||
nl = (*cp == '\n');
|
||||
@ -4799,7 +4800,7 @@ static int filechar(struct ioarg *ap)
|
||||
if (i)
|
||||
lseek(ap->afile, ap->afpos, SEEK_SET);
|
||||
|
||||
i = safe_read(ap->afile, bp->buf, sizeof(bp->buf));
|
||||
i = nonblock_safe_read(ap->afile, bp->buf, sizeof(bp->buf));
|
||||
if (i <= 0) {
|
||||
closef(ap->afile);
|
||||
return 0;
|
||||
@ -4830,7 +4831,7 @@ static int filechar(struct ioarg *ap)
|
||||
return c;
|
||||
}
|
||||
#endif
|
||||
i = safe_read(ap->afile, &c, sizeof(c));
|
||||
i = nonblock_safe_read(ap->afile, &c, sizeof(c));
|
||||
return i == sizeof(c) ? (c & 0x7f) : (closef(ap->afile), 0);
|
||||
}
|
||||
|
||||
@ -4841,7 +4842,7 @@ static int herechar(struct ioarg *ap)
|
||||
{
|
||||
char c;
|
||||
|
||||
if (read(ap->afile, &c, sizeof(c)) != sizeof(c)) {
|
||||
if (nonblock_safe_read(ap->afile, &c, sizeof(c)) != sizeof(c)) {
|
||||
close(ap->afile);
|
||||
c = '\0';
|
||||
}
|
||||
|
Loading…
Reference in New Issue
Block a user