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shm_open2: Implement SHM_GROW_ON_WRITE

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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
This commit is contained in:
Kyle Evans 2020-07-10 00:43:45 +00:00
parent 2d68fac9bd
commit 3f07b9d9f8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=363065
2 changed files with 34 additions and 5 deletions
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37
sys/kern/uipc_shm.c
View File

@ -313,6 +313,7 @@ shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
struct shmfd *shmfd;
void *rl_cookie;
int error;
off_t size;
shmfd = fp->f_data;
#ifdef MAC
@ -321,17 +322,42 @@ shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
return (error);
#endif
foffset_lock_uio(fp, uio, flags);
if (uio->uio_resid > OFF_MAX - uio->uio_offset) {
/*
* Overflow is only an error if we're supposed to expand on
* write. Otherwise, we'll just truncate the write to the
* size of the file, which can only grow up to OFF_MAX.
*/
if ((shmfd->shm_flags & SHM_GROW_ON_WRITE) != 0) {
foffset_unlock_uio(fp, uio, flags);
return (EFBIG);
}
size = shmfd->shm_size;
} else {
size = uio->uio_offset + uio->uio_resid;
}
if ((flags & FOF_OFFSET) == 0) {
rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
&shmfd->shm_mtx);
} else {
rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
size, &shmfd->shm_mtx);
}
if ((shmfd->shm_seals & F_SEAL_WRITE) != 0)
if ((shmfd->shm_seals & F_SEAL_WRITE) != 0) {
error = EPERM;
else
error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
} else {
error = 0;
if ((shmfd->shm_flags & SHM_GROW_ON_WRITE) != 0 &&
size > shmfd->shm_size) {
VM_OBJECT_WLOCK(shmfd->shm_object);
error = shm_dotruncate_locked(shmfd, size, rl_cookie);
VM_OBJECT_WUNLOCK(shmfd->shm_object);
}
if (error == 0)
error = uiomove_object(shmfd->shm_object,
shmfd->shm_size, uio);
}
rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
foffset_unlock_uio(fp, uio, flags);
return (error);
@ -748,7 +774,7 @@ kern_shm_open2(struct thread *td, const char *userpath, int flags, mode_t mode,
mode_t cmode;
int error, fd, initial_seals;
if ((shmflags & ~SHM_ALLOW_SEALING) != 0)
if ((shmflags & ~(SHM_ALLOW_SEALING | SHM_GROW_ON_WRITE)) != 0)
return (EINVAL);
initial_seals = F_SEAL_SEAL;
@ -921,6 +947,7 @@ kern_shm_open2(struct thread *td, const char *userpath, int flags, mode_t mode,
}
}
shmfd->shm_flags = shmflags;
finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
td->td_retval[0] = fd;

2
sys/sys/mman.h
View File

@ -190,6 +190,7 @@
* shmflags for shm_open2()
*/
#define SHM_ALLOW_SEALING 0x00000001
#define SHM_GROW_ON_WRITE 0x00000002
/*
* Flags for memfd_create().
@ -278,6 +279,7 @@ struct shmfd {
struct rangelock shm_rl;
struct mtx shm_mtx;
int shm_flags;
int shm_seals;
};
#endif