Message ID | 20210504015152.31064-3-ericonr@disroot.org |
---|---|
State | New |
Headers | show |
Series | [1/3] misc: use _fitoa_word to implement __fd_to_filename. | expand |
On 03/05/2021 22:51, Érico Nogueira via Libc-alpha wrote: > Big win in binary size and avoids duplicating the logic in multiple > places. > > On x86_64, dropped from 1883206 to 1881790, a 1416 byte decrease. > > Also changed logic to track if ttyname_buf has been allocated by > checking if it's NULL instead of tracking buflen as an additional > variable. > --- > > I was going to simply change the function to use __fd_to_filename, like > the 2/3 patch, but this felt like a better improvement. However, I > haven't studied the implications deeply or verified if the ttyname() > logic behaved noticeably (or subtly) different than what ttyname_r() > did. > > sysdeps/unix/sysv/linux/ttyname.c | 161 ++---------------------------- > 1 file changed, 9 insertions(+), 152 deletions(-) > > diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c > index d561ac12f2..a2bb81c78b 100644 > --- a/sysdeps/unix/sysv/linux/ttyname.c > +++ b/sysdeps/unix/sysv/linux/ttyname.c > @@ -17,17 +17,9 @@ > > #include <errno.h> > #include <limits.h> > -#include <stddef.h> > -#include <dirent.h> > -#include <sys/types.h> > -#include <sys/stat.h> > #include <termios.h> > -#include <unistd.h> > -#include <string.h> > #include <stdlib.h> > > -#include <_itoa.h> > - > #include "ttyname.h" > > #if 0 > @@ -35,170 +27,35 @@ > char *__ttyname; > #endif Maybe remove this dead code as well. > > -static char *getttyname (const char *dev, const struct stat64 *mytty, > - int save, int *dostat); > - > -libc_freeres_ptr (static char *getttyname_name); > - > -static char * > -attribute_compat_text_section > -getttyname (const char *dev, const struct stat64 *mytty, int save, int *dostat) > -{ > - static size_t namelen; > - struct stat64 st; > - DIR *dirstream; > - struct dirent64 *d; > - size_t devlen = strlen (dev) + 1; > - > - dirstream = __opendir (dev); > - if (dirstream == NULL) > - { > - *dostat = -1; > - return NULL; > - } > - > - /* Prepare for the loop. If we already have a buffer copy the directory > - name we look at into it. */ > - if (devlen < namelen) > - *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/'; > - > - while ((d = __readdir64 (dirstream)) != NULL) > - if ((d->d_fileno == mytty->st_ino || *dostat) > - && strcmp (d->d_name, "stdin") > - && strcmp (d->d_name, "stdout") > - && strcmp (d->d_name, "stderr")) > - { > - size_t dlen = _D_ALLOC_NAMLEN (d); > - if (devlen + dlen > namelen) > - { > - free (getttyname_name); > - namelen = 2 * (devlen + dlen); /* Big enough. */ > - getttyname_name = malloc (namelen); > - if (! getttyname_name) > - { > - *dostat = -1; > - /* Perhaps it helps to free the directory stream buffer. */ > - (void) __closedir (dirstream); > - return NULL; > - } > - *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/'; > - } > - memcpy (&getttyname_name[devlen], d->d_name, dlen); > - if (__stat64 (getttyname_name, &st) == 0 > - && is_mytty (mytty, &st)) > - { > - (void) __closedir (dirstream); > -#if 0 > - __ttyname = getttyname_name; > -#endif > - __set_errno (save); > - return getttyname_name; > - } > - } > - > - (void) __closedir (dirstream); > - __set_errno (save); > - return NULL; > -} > - > - > +#define TTYNAME_BUFLEN (PATH_MAX-1) > /* Static buffer in `ttyname'. */ > libc_freeres_ptr (static char *ttyname_buf); Although not really related to this change, since you are touching it I think it should use a libc_freeres_fn instead: | static char *ttyname_buf; | | libc_freeres_fn (free_mem) | { | free (ttyname_buf); | } > > - > /* Return the pathname of the terminal FD is open on, or NULL on errors. > The returned storage is good only until the next call to this function. */ > char * > ttyname (int fd) > { > - static size_t buflen; > - char procname[30]; > - struct stat64 st, st1; > - int dostat = 0; > - int doispty = 0; > - char *name; > - int save = errno; > - struct termios term; > - > /* isatty check, tcgetattr is used because it sets the correct > - errno (EBADF resp. ENOTTY) on error. */ > + errno (EBADF resp. ENOTTY) on error. Fast error path to avoid the allocation */ Double space after period and line too long. > + struct termios term; > if (__glibc_unlikely (__tcgetattr (fd, &term) < 0)) > return NULL; > > - if (__fstat64 (fd, &st) < 0) > - return NULL; > - > - /* We try using the /proc filesystem. */ > - *_fitoa_word (fd, __stpcpy (procname, "/proc/self/fd/"), 10, 0) = '\0'; > - > - if (buflen == 0) > + if (ttyname_buf == NULL) > { > - buflen = 4095; > - ttyname_buf = (char *) malloc (buflen + 1); > + ttyname_buf = malloc (TTYNAME_BUFLEN + 1); > if (ttyname_buf == NULL) > { > - buflen = 0; > return NULL; > } > } > Ok. > - ssize_t len = __readlink (procname, ttyname_buf, buflen); > - if (__glibc_likely (len != -1)) > - { > - if ((size_t) len >= buflen) > - return NULL; > - > -#define UNREACHABLE_LEN strlen ("(unreachable)") > - if (len > UNREACHABLE_LEN > - && memcmp (ttyname_buf, "(unreachable)", UNREACHABLE_LEN) == 0) > - { > - memmove (ttyname_buf, ttyname_buf + UNREACHABLE_LEN, > - len - UNREACHABLE_LEN); > - len -= UNREACHABLE_LEN; > - } > - > - /* readlink need not terminate the string. */ > - ttyname_buf[len] = '\0'; > - > - /* Verify readlink result, fall back on iterating through devices. */ > - if (ttyname_buf[0] == '/' > - && __stat64 (ttyname_buf, &st1) == 0 > - && is_mytty (&st, &st1)) > - return ttyname_buf; > - > - doispty = 1; > - } > - > - if (__stat64 ("/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode)) > - { > - name = getttyname ("/dev/pts", &st, save, &dostat); > - } > - else > - { > - __set_errno (save); > - name = NULL; > - } > - > - if (!name && dostat != -1) > + int result = ttyname_r (fd, ttyname_buf, TTYNAME_BUFLEN); > + if (result != 0) Why do you need to pass the allocated buffer size minus 1? The ttyname_r should handle it, it already pass buflen - 1 on readlink for instance. > { > - name = getttyname ("/dev", &st, save, &dostat); > - } > - > - if (!name && dostat != -1) > - { > - dostat = 1; > - name = getttyname ("/dev", &st, save, &dostat); > - } > - > - if (!name && doispty && is_pty (&st)) > - { > - /* We failed to figure out the TTY's name, but we can at least > - signal that we did verify that it really is a PTY slave. > - This happens when we have inherited the file descriptor from > - a different mount namespace. */ > - __set_errno (ENODEV); > + __set_errno (result); > return NULL; > } > - > - return name; > + return ttyname_buf; > } > With this change ttyname now returns ERANGE instead of ENAMETOOLONG if readlink returns a link larger than the specified buffer, but I think it should be ok.
On 04/05/2021 13:37, Adhemerval Zanella wrote: >> - >> - if (!name && dostat != -1) >> + int result = ttyname_r (fd, ttyname_buf, TTYNAME_BUFLEN); >> + if (result != 0) > > Why do you need to pass the allocated buffer size minus 1? The ttyname_r > should handle it, it already pass buflen - 1 on readlink for instance. You also need a libc_hidden_{proto,def} ttyname_r to avoid the intra PLT (the elf/check-localplt should have warned you about it).
On 04/05/2021 13:43, Adhemerval Zanella wrote: > > > On 04/05/2021 13:37, Adhemerval Zanella wrote: >>> - >>> - if (!name && dostat != -1) >>> + int result = ttyname_r (fd, ttyname_buf, TTYNAME_BUFLEN); >>> + if (result != 0) >> >> Why do you need to pass the allocated buffer size minus 1? The ttyname_r >> should handle it, it already pass buflen - 1 on readlink for instance. > > You also need a libc_hidden_{proto,def} ttyname_r to avoid the intra > PLT (the elf/check-localplt should have warned you about it). > I fixed my previous noted issues along with this one and push it upstream, thanks for the patch.
On Fri May 7, 2021 at 2:21 PM -03, Adhemerval Zanella wrote: > > > On 04/05/2021 13:43, Adhemerval Zanella wrote: > > > > > > On 04/05/2021 13:37, Adhemerval Zanella wrote: > >>> - > >>> - if (!name && dostat != -1) > >>> + int result = ttyname_r (fd, ttyname_buf, TTYNAME_BUFLEN); > >>> + if (result != 0) > >> > >> Why do you need to pass the allocated buffer size minus 1? The ttyname_r > >> should handle it, it already pass buflen - 1 on readlink for instance. > > > > You also need a libc_hidden_{proto,def} ttyname_r to avoid the intra > > PLT (the elf/check-localplt should have warned you about it). > > > > I fixed my previous noted issues along with this one and push it > upstream, thanks for the patch. Ah, great! I hadn't gotten to this yet, thanks a lot for the help and reviews :)
diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c index d561ac12f2..a2bb81c78b 100644 --- a/sysdeps/unix/sysv/linux/ttyname.c +++ b/sysdeps/unix/sysv/linux/ttyname.c @@ -17,17 +17,9 @@ #include <errno.h> #include <limits.h> -#include <stddef.h> -#include <dirent.h> -#include <sys/types.h> -#include <sys/stat.h> #include <termios.h> -#include <unistd.h> -#include <string.h> #include <stdlib.h> -#include <_itoa.h> - #include "ttyname.h" #if 0 @@ -35,170 +27,35 @@ char *__ttyname; #endif -static char *getttyname (const char *dev, const struct stat64 *mytty, - int save, int *dostat); - -libc_freeres_ptr (static char *getttyname_name); - -static char * -attribute_compat_text_section -getttyname (const char *dev, const struct stat64 *mytty, int save, int *dostat) -{ - static size_t namelen; - struct stat64 st; - DIR *dirstream; - struct dirent64 *d; - size_t devlen = strlen (dev) + 1; - - dirstream = __opendir (dev); - if (dirstream == NULL) - { - *dostat = -1; - return NULL; - } - - /* Prepare for the loop. If we already have a buffer copy the directory - name we look at into it. */ - if (devlen < namelen) - *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/'; - - while ((d = __readdir64 (dirstream)) != NULL) - if ((d->d_fileno == mytty->st_ino || *dostat) - && strcmp (d->d_name, "stdin") - && strcmp (d->d_name, "stdout") - && strcmp (d->d_name, "stderr")) - { - size_t dlen = _D_ALLOC_NAMLEN (d); - if (devlen + dlen > namelen) - { - free (getttyname_name); - namelen = 2 * (devlen + dlen); /* Big enough. */ - getttyname_name = malloc (namelen); - if (! getttyname_name) - { - *dostat = -1; - /* Perhaps it helps to free the directory stream buffer. */ - (void) __closedir (dirstream); - return NULL; - } - *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/'; - } - memcpy (&getttyname_name[devlen], d->d_name, dlen); - if (__stat64 (getttyname_name, &st) == 0 - && is_mytty (mytty, &st)) - { - (void) __closedir (dirstream); -#if 0 - __ttyname = getttyname_name; -#endif - __set_errno (save); - return getttyname_name; - } - } - - (void) __closedir (dirstream); - __set_errno (save); - return NULL; -} - - +#define TTYNAME_BUFLEN (PATH_MAX-1) /* Static buffer in `ttyname'. */ libc_freeres_ptr (static char *ttyname_buf); - /* Return the pathname of the terminal FD is open on, or NULL on errors. The returned storage is good only until the next call to this function. */ char * ttyname (int fd) { - static size_t buflen; - char procname[30]; - struct stat64 st, st1; - int dostat = 0; - int doispty = 0; - char *name; - int save = errno; - struct termios term; - /* isatty check, tcgetattr is used because it sets the correct - errno (EBADF resp. ENOTTY) on error. */ + errno (EBADF resp. ENOTTY) on error. Fast error path to avoid the allocation */ + struct termios term; if (__glibc_unlikely (__tcgetattr (fd, &term) < 0)) return NULL; - if (__fstat64 (fd, &st) < 0) - return NULL; - - /* We try using the /proc filesystem. */ - *_fitoa_word (fd, __stpcpy (procname, "/proc/self/fd/"), 10, 0) = '\0'; - - if (buflen == 0) + if (ttyname_buf == NULL) { - buflen = 4095; - ttyname_buf = (char *) malloc (buflen + 1); + ttyname_buf = malloc (TTYNAME_BUFLEN + 1); if (ttyname_buf == NULL) { - buflen = 0; return NULL; } } - ssize_t len = __readlink (procname, ttyname_buf, buflen); - if (__glibc_likely (len != -1)) - { - if ((size_t) len >= buflen) - return NULL; - -#define UNREACHABLE_LEN strlen ("(unreachable)") - if (len > UNREACHABLE_LEN - && memcmp (ttyname_buf, "(unreachable)", UNREACHABLE_LEN) == 0) - { - memmove (ttyname_buf, ttyname_buf + UNREACHABLE_LEN, - len - UNREACHABLE_LEN); - len -= UNREACHABLE_LEN; - } - - /* readlink need not terminate the string. */ - ttyname_buf[len] = '\0'; - - /* Verify readlink result, fall back on iterating through devices. */ - if (ttyname_buf[0] == '/' - && __stat64 (ttyname_buf, &st1) == 0 - && is_mytty (&st, &st1)) - return ttyname_buf; - - doispty = 1; - } - - if (__stat64 ("/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode)) - { - name = getttyname ("/dev/pts", &st, save, &dostat); - } - else - { - __set_errno (save); - name = NULL; - } - - if (!name && dostat != -1) + int result = ttyname_r (fd, ttyname_buf, TTYNAME_BUFLEN); + if (result != 0) { - name = getttyname ("/dev", &st, save, &dostat); - } - - if (!name && dostat != -1) - { - dostat = 1; - name = getttyname ("/dev", &st, save, &dostat); - } - - if (!name && doispty && is_pty (&st)) - { - /* We failed to figure out the TTY's name, but we can at least - signal that we did verify that it really is a PTY slave. - This happens when we have inherited the file descriptor from - a different mount namespace. */ - __set_errno (ENODEV); + __set_errno (result); return NULL; } - - return name; + return ttyname_buf; }