shm_open2: Implement SHM_GROW_ON_WRITE
Lack of SHM_GROW_ON_WRITE is actively breaking Python's memfd_create tests, so go ahead and implement it. A future change will make memfd_create always set SHM_GROW_ON_WRITE, to match Linux behavior and unbreak Python's tests on -CURRENT. Reviewed by: kib Differential Revision: https://reviews.freebsd.org/D25502
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=363065
@ -313,6 +313,7 @@ shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
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struct shmfd *shmfd;
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void *rl_cookie;
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int error;
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off_t size;
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shmfd = fp->f_data;
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#ifdef MAC
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@ -321,17 +322,42 @@ shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
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return (error);
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#endif
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foffset_lock_uio(fp, uio, flags);
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if (uio->uio_resid > OFF_MAX - uio->uio_offset) {
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/*
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* Overflow is only an error if we're supposed to expand on
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* write. Otherwise, we'll just truncate the write to the
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* size of the file, which can only grow up to OFF_MAX.
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*/
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if ((shmfd->shm_flags & SHM_GROW_ON_WRITE) != 0) {
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foffset_unlock_uio(fp, uio, flags);
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return (EFBIG);
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}
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size = shmfd->shm_size;
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} else {
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size = uio->uio_offset + uio->uio_resid;
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}
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if ((flags & FOF_OFFSET) == 0) {
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rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
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&shmfd->shm_mtx);
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} else {
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rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
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uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
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size, &shmfd->shm_mtx);
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}
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if ((shmfd->shm_seals & F_SEAL_WRITE) != 0)
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if ((shmfd->shm_seals & F_SEAL_WRITE) != 0) {
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error = EPERM;
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else
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error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
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} else {
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error = 0;
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if ((shmfd->shm_flags & SHM_GROW_ON_WRITE) != 0 &&
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size > shmfd->shm_size) {
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VM_OBJECT_WLOCK(shmfd->shm_object);
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error = shm_dotruncate_locked(shmfd, size, rl_cookie);
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VM_OBJECT_WUNLOCK(shmfd->shm_object);
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}
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if (error == 0)
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error = uiomove_object(shmfd->shm_object,
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shmfd->shm_size, uio);
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}
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rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
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foffset_unlock_uio(fp, uio, flags);
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return (error);
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@ -748,7 +774,7 @@ kern_shm_open2(struct thread *td, const char *userpath, int flags, mode_t mode,
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mode_t cmode;
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int error, fd, initial_seals;
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if ((shmflags & ~SHM_ALLOW_SEALING) != 0)
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if ((shmflags & ~(SHM_ALLOW_SEALING | SHM_GROW_ON_WRITE)) != 0)
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return (EINVAL);
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initial_seals = F_SEAL_SEAL;
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@ -921,6 +947,7 @@ kern_shm_open2(struct thread *td, const char *userpath, int flags, mode_t mode,
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}
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}
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shmfd->shm_flags = shmflags;
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finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
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td->td_retval[0] = fd;
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@ -190,6 +190,7 @@
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* shmflags for shm_open2()
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*/
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#define SHM_ALLOW_SEALING 0x00000001
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#define SHM_GROW_ON_WRITE 0x00000002
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/*
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* Flags for memfd_create().
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@ -278,6 +279,7 @@ struct shmfd {
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struct rangelock shm_rl;
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struct mtx shm_mtx;
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int shm_flags;
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int shm_seals;
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};
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#endif
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