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linuxolator: implement memfd_create syscall

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This effectively mirrors our libc implementation, but with minor fudging --
name needs to be copied in from userspace, so we just copy it straight into
stack-allocated memfd_name into the correct position rather than allocating
memory that needs to be cleaned up.

The sealing-related fcntl(2) commands, F_GET_SEALS and F_ADD_SEALS, have
also been implemented now that we support them.

Note that this implementation is still not quite at feature parity w.r.t.
the actual Linux version; some caveats, from my foggy memory:

- Need to implement SHM_GROW_ON_WRITE, default for memfd (in progress)
- LTP wants the memfd name exposed to fdescfs
- Linux allows open() of an fdescfs fd with O_TRUNC to truncate after dup.
  (?)

Interested parties can install and run LTP from ports (devel/linux-ltp) to
confirm any fixes.

PR:		240874
Reviewed by:	kib, trasz
Differential Revision:	https://reviews.freebsd.org/D21845
This commit is contained in:
Kyle Evans 2020-06-29 03:09:14 +00:00
parent 0ed1d2e484
commit 5403f186a7
8 changed files with 239 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
sys/amd64/linux/linux_dummy.c
View File

@ -138,7 +138,6 @@ DUMMY(sched_getattr);
/* Linux 3.15: */
DUMMY(kexec_file_load);
/* Linux 3.17: */
DUMMY(memfd_create);
DUMMY(seccomp);
/* Linux 3.18: */
DUMMY(bpf);

1
sys/amd64/linux32/linux32_dummy.c
View File

@ -133,7 +133,6 @@ DUMMY(finit_module);
DUMMY(sched_setattr);
DUMMY(sched_getattr);
/* Linux 3.17: */
DUMMY(memfd_create);
DUMMY(seccomp);
/* Linux 3.18: */
DUMMY(bpf);

1
sys/arm64/linux/linux_dummy.c
View File

@ -127,7 +127,6 @@ DUMMY(finit_module);
DUMMY(sched_setattr);
DUMMY(sched_getattr);
/* Linux 3.17: */
DUMMY(memfd_create);
DUMMY(seccomp);
/* Linux 3.18: */
DUMMY(bpf);

76
sys/compat/linux/linux.c
View File

@ -551,3 +551,79 @@ linux_dev_shm_destroy(void)
destroy_dev(dev_shm_cdev);
}
int
bsd_to_linux_bits_(int value, struct bsd_to_linux_bitmap *bitmap,
size_t mapcnt, int no_value)
{
int bsd_mask, bsd_value, linux_mask, linux_value;
int linux_ret;
size_t i;
bool applied;
applied = false;
linux_ret = 0;
for (i = 0; i < mapcnt; ++i) {
bsd_mask = bitmap[i].bsd_mask;
bsd_value = bitmap[i].bsd_value;
if (bsd_mask == 0)
bsd_mask = bsd_value;
linux_mask = bitmap[i].linux_mask;
linux_value = bitmap[i].linux_value;
if (linux_mask == 0)
linux_mask = linux_value;
/*
* If a mask larger than just the value is set, we explicitly
* want to make sure that only this bit we mapped within that
* mask is set.
*/
if ((value & bsd_mask) == bsd_value) {
linux_ret = (linux_ret & ~linux_mask) | linux_value;
applied = true;
}
}
if (!applied)
return (no_value);
return (linux_ret);
}
int
linux_to_bsd_bits_(int value, struct bsd_to_linux_bitmap *bitmap,
size_t mapcnt, int no_value)
{
int bsd_mask, bsd_value, linux_mask, linux_value;
int bsd_ret;
size_t i;
bool applied;
applied = false;
bsd_ret = 0;
for (i = 0; i < mapcnt; ++i) {
bsd_mask = bitmap[i].bsd_mask;
bsd_value = bitmap[i].bsd_value;
if (bsd_mask == 0)
bsd_mask = bsd_value;
linux_mask = bitmap[i].linux_mask;
linux_value = bitmap[i].linux_value;
if (linux_mask == 0)
linux_mask = linux_value;
/*
* If a mask larger than just the value is set, we explicitly
* want to make sure that only this bit we mapped within that
* mask is set.
*/
if ((value & linux_mask) == linux_value) {
bsd_ret = (bsd_ret & ~bsd_mask) | bsd_value;
applied = true;
}
}
if (!applied)
return (no_value);
return (bsd_ret);
}

45
sys/compat/linux/linux.h
View File

@ -148,4 +148,49 @@ extern struct mtx futex_mtx;
void linux_dev_shm_create(void);
void linux_dev_shm_destroy(void);
/*
* mask=0 is not sensible for this application, so it will be taken to mean
* a mask equivalent to the value. Otherwise, (word & mask) == value maps to
* (word & ~mask) | value in a bitfield for the platform we're converting to.
*/
struct bsd_to_linux_bitmap {
int bsd_mask;
int bsd_value;
int linux_mask;
int linux_value;
};
int bsd_to_linux_bits_(int value, struct bsd_to_linux_bitmap *bitmap,
size_t mapcnt, int no_value);
int linux_to_bsd_bits_(int value, struct bsd_to_linux_bitmap *bitmap,
size_t mapcnt, int no_value);
#define bsd_to_linux_bits(_val, _bmap, _noval) \
bsd_to_linux_bits_((_val), (_bmap), nitems((_bmap)), (_noval))
/*
* These functions are used for simplification of BSD <-> Linux bit conversions.
* Given `value`, a bit field, these functions will walk the given bitmap table
* and set the appropriate bits for the target platform. If any bits were
* successfully converted, then the return value is the equivalent of value
* represented with the bit values appropriate for the target platform.
* Otherwise, the value supplied as `no_value` is returned.
*/
#define linux_to_bsd_bits(_val, _bmap, _noval) \
linux_to_bsd_bits_((_val), (_bmap), nitems((_bmap)), (_noval))
/*
* Easy mapping helpers. BITMAP_EASY_LINUX represents a single bit to be
* translated, and the FreeBSD and Linux values are supplied. BITMAP_1t1_LINUX
* is the extreme version of this, where not only is it a single bit, but the
* name of the macro used to represent the Linux version of a bit literally has
* LINUX_ prepended to the normal name.
*/
#define BITMAP_EASY_LINUX(_name, _linux_name) \
{ \
.bsd_value = (_name), \
.linux_value = (_linux_name), \
}
#define BITMAP_1t1_LINUX(_name) BITMAP_EASY_LINUX(_name, LINUX_##_name)
#endif /* _LINUX_MI_H_ */

90
sys/compat/linux/linux_file.c
View File

@ -41,6 +41,7 @@ __FBSDID("$FreeBSD$");
#include <sys/filedesc.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/namei.h>
@ -68,6 +69,37 @@ __FBSDID("$FreeBSD$");
static int linux_common_open(struct thread *, int, char *, int, int);
static int linux_getdents_error(struct thread *, int, int);
static struct bsd_to_linux_bitmap seal_bitmap[] = {
BITMAP_1t1_LINUX(F_SEAL_SEAL),
BITMAP_1t1_LINUX(F_SEAL_SHRINK),
BITMAP_1t1_LINUX(F_SEAL_GROW),
BITMAP_1t1_LINUX(F_SEAL_WRITE),
};
#define MFD_HUGETLB_ENTRY(_size) \
{ \
.bsd_value = MFD_HUGE_##_size, \
.linux_value = LINUX_HUGETLB_FLAG_ENCODE_##_size \
}
static struct bsd_to_linux_bitmap mfd_bitmap[] = {
BITMAP_1t1_LINUX(MFD_CLOEXEC),
BITMAP_1t1_LINUX(MFD_ALLOW_SEALING),
BITMAP_1t1_LINUX(MFD_HUGETLB),
MFD_HUGETLB_ENTRY(64KB),
MFD_HUGETLB_ENTRY(512KB),
MFD_HUGETLB_ENTRY(1MB),
MFD_HUGETLB_ENTRY(2MB),
MFD_HUGETLB_ENTRY(8MB),
MFD_HUGETLB_ENTRY(16MB),
MFD_HUGETLB_ENTRY(32MB),
MFD_HUGETLB_ENTRY(256MB),
MFD_HUGETLB_ENTRY(512MB),
MFD_HUGETLB_ENTRY(1GB),
MFD_HUGETLB_ENTRY(2GB),
MFD_HUGETLB_ENTRY(16GB),
};
#undef MFD_HUGETLB_ENTRY
#ifdef LINUX_LEGACY_SYSCALLS
int
linux_creat(struct thread *td, struct linux_creat_args *args)
@ -1371,6 +1403,21 @@ fcntl_common(struct thread *td, struct linux_fcntl_args *args)
case LINUX_F_DUPFD_CLOEXEC:
return (kern_fcntl(td, args->fd, F_DUPFD_CLOEXEC, args->arg));
/*
* Our F_SEAL_* values match Linux one for maximum compatibility. So we
* only needed to account for different values for fcntl(2) commands.
*/
case LINUX_F_GET_SEALS:
error = kern_fcntl(td, args->fd, F_GET_SEALS, 0);
if (error != 0)
return (error);
td->td_retval[0] = bsd_to_linux_bits(td->td_retval[0],
seal_bitmap, 0);
return (0);
case LINUX_F_ADD_SEALS:
return (kern_fcntl(td, args->fd, F_ADD_SEALS,
linux_to_bsd_bits(args->arg, seal_bitmap, 0)));
default:
linux_msg(td, "unsupported fcntl cmd %d\n", args->cmd);
return (EINVAL);
@ -1676,3 +1723,46 @@ linux_copy_file_range(struct thread *td, struct linux_copy_file_range_args
return (error);
}
#define LINUX_MEMFD_PREFIX "memfd:"
int
linux_memfd_create(struct thread *td, struct linux_memfd_create_args *args)
{
char memfd_name[LINUX_NAME_MAX + 1];
int error, flags, shmflags, oflags;
/*
* This is our clever trick to avoid the heap allocation to copy in the
* uname. We don't really need to go this far out of our way, but it
* does keep the rest of this function fairly clean as they don't have
* to worry about cleanup on the way out.
*/
error = copyinstr(args->uname_ptr,
memfd_name + sizeof(LINUX_MEMFD_PREFIX) - 1,
LINUX_NAME_MAX - sizeof(LINUX_MEMFD_PREFIX) - 1, NULL);
if (error != 0) {
if (error == ENAMETOOLONG)
error = EINVAL;
return (error);
}
memcpy(memfd_name, LINUX_MEMFD_PREFIX, sizeof(LINUX_MEMFD_PREFIX) - 1);
flags = linux_to_bsd_bits(args->flags, mfd_bitmap, 0);
if ((flags & ~(MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB |
MFD_HUGE_MASK)) != 0)
return (EINVAL);
/* Size specified but no HUGETLB. */
if ((flags & MFD_HUGE_MASK) != 0 && (flags & MFD_HUGETLB) == 0)
return (EINVAL);
/* We don't actually support HUGETLB. */
if ((flags & MFD_HUGETLB) != 0)
return (ENOSYS);
oflags = O_RDWR;
shmflags = 0;
if ((flags & MFD_CLOEXEC) != 0)
oflags |= O_CLOEXEC;
if ((flags & MFD_ALLOW_SEALING) != 0)
shmflags |= SHM_ALLOW_SEALING;
return (kern_shm_open2(td, SHM_ANON, oflags, 0, shmflags, NULL,
memfd_name));
}

28
sys/compat/linux/linux_file.h
View File

@ -118,6 +118,9 @@
#define LINUX_F_SETPIPE_SZ (LINUX_F_SPECIFIC_BASE + 7)
#define LINUX_F_GETPIPE_SZ (LINUX_F_SPECIFIC_BASE + 8)
#define LINUX_F_ADD_SEALS (LINUX_F_SPECIFIC_BASE + 9)
#define LINUX_F_GET_SEALS (LINUX_F_SPECIFIC_BASE + 10)
#define LINUX_F_GETLKP 36
#define LINUX_F_SETLKP 37
#define LINUX_F_SETLKPW 38
@ -146,4 +149,29 @@
#define LINUX_SYNC_FILE_RANGE_WRITE 2
#define LINUX_SYNC_FILE_RANGE_WAIT_AFTER 4
#define LINUX_F_SEAL_SEAL 0x0001
#define LINUX_F_SEAL_SHRINK 0x0002
#define LINUX_F_SEAL_GROW 0x0004
#define LINUX_F_SEAL_WRITE 0x0008
#define LINUX_MFD_CLOEXEC 0x0001
#define LINUX_MFD_ALLOW_SEALING 0x0002
#define LINUX_MFD_HUGETLB 0x0004
#define LINUX_HUGETLB_FLAG_ENCODE_SHIFT 26
#define LINUX_HUGETLB_FLAG_ENCODE_MASK 0x3f
#define LINUX_HUGETLB_FLAG_ENCODE_64KB (16 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_512KB (19 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_1MB (20 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_2MB (21 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_8MB (23 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_16MB (24 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_32MB (25 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_256MB (28 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_512MB (29 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_1GB (30 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_2GB (31 << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#define LINUX_HUGETLB_FLAG_ENCODE_16GB (34U << LINUX_HUGETLB_FLAG_ENCODE_SHIFT)
#endif /* !_LINUX_FILE_H_ */

1
sys/i386/linux/linux_dummy.c
View File

@ -129,7 +129,6 @@ DUMMY(finit_module);
DUMMY(sched_setattr);
DUMMY(sched_getattr);
/* Linux 3.17: */
DUMMY(memfd_create);
DUMMY(seccomp);
/* Linux 3.18: */
DUMMY(bpf);