It is the starting point to make liburing can work without the libc.
Make it possible to remove the dependency of `errno` variable (which
comes from libc). Do it incrementally, start from `__sys_io_uring_*`
functions.
@@ Notes:
1) We do not plan to remove the libc support.
2) The return value for each syscall API to indicate error is a
negative value within range [-4095, -1].
3) In the liburing sources, the `errno` variable is only allowed to
be used in file `src/syscall.c` (just to emulate the kernel
style return value).
@@ Extra notes for backward compatibility:
Currently, we expose these functions (**AAA**) to userland:
**AAA**:
1) `__sys_io_uring_register`
2) `__sys_io_uring_setup`
3) `__sys_io_uring_enter2`
4) `__sys_io_uring_enter`
As the userland needs to check the `errno` value to use them properly,
this means those functions always depend on libc. So we cannot change
their behavior.
As such, only for the **no libc** environment case, we remove those
functions (**AAA**).
Then we introduce new functions (**BBB**) with the same name (with
extra underscore as prefix, 4 underscores). These functions do not
use `errno` variable on the caller (they use the kernel style return
value) and always exist regardless the libc existence.
**BBB**:
1) `____sys_io_uring_register`
2) `____sys_io_uring_setup`
3) `____sys_io_uring_enter2`
4) `____sys_io_uring_enter`
@@ Summary
1) **AAA** will only exist for the libc environment.
2) **BBB** always exists.
3) Do not use **AAA** for the liburing internal (it's just for the
userland backward compatibility).
4) For the libc environment, **BBB** may use `syscall(2)` and
`errno` variable, only to emulate the kernel style return value.
5) For the no libc environment, **BBB** will use Assembly interface
to perform the syscall (arch dependent).
6) Tests should not be affected, this is because of (1) and (4),
which keep the compatibility.
Link: https://github.com/axboe/liburing/issues/443
Signed-off-by: Ammar Faizi <ammar.faizi@xxxxxxxxxxxxxxxxxxxxx>
---
src/queue.c | 27 +++-----
src/register.c | 184 ++++++++++++++++---------------------------------
src/setup.c | 4 +-
src/syscall.c | 45 +++++++++++-
src/syscall.h | 8 +++
5 files changed, 120 insertions(+), 148 deletions(-)
diff --git a/src/queue.c b/src/queue.c
index 10ef31c..e85ea1d 100644
--- a/src/queue.c
+++ b/src/queue.c
@@ -117,11 +117,11 @@ static int _io_uring_get_cqe(struct io_uring *ring, struct io_uring_cqe **cqe_pt
if (!need_enter)
break;
- ret = __sys_io_uring_enter2(ring->ring_fd, data->submit,
- data->wait_nr, flags, data->arg,
- data->sz);
+ ret = ____sys_io_uring_enter2(ring->ring_fd, data->submit,
+ data->wait_nr, flags, data->arg,
+ data->sz);
if (ret < 0) {
- err = -errno;
+ err = ret;
break;
}
@@ -178,8 +178,8 @@ again:
goto done;
if (cq_ring_needs_flush(ring)) {
- __sys_io_uring_enter(ring->ring_fd, 0, 0,
- IORING_ENTER_GETEVENTS, NULL);
+ ____sys_io_uring_enter(ring->ring_fd, 0, 0,
+ IORING_ENTER_GETEVENTS, NULL);
overflow_checked = true;
goto again;
}
@@ -333,10 +333,8 @@ static int __io_uring_submit(struct io_uring *ring, unsigned submitted,
if (wait_nr || (ring->flags & IORING_SETUP_IOPOLL))
flags |= IORING_ENTER_GETEVENTS;
- ret = __sys_io_uring_enter(ring->ring_fd, submitted, wait_nr,
- flags, NULL);
- if (ret < 0)
- return -errno;
+ ret = ____sys_io_uring_enter(ring->ring_fd, submitted, wait_nr,
+ flags, NULL);
} else
ret = submitted;
@@ -391,11 +389,6 @@ struct io_uring_sqe *io_uring_get_sqe(struct io_uring *ring)
int __io_uring_sqring_wait(struct io_uring *ring)
{
- int ret;
-
- ret = __sys_io_uring_enter(ring->ring_fd, 0, 0, IORING_ENTER_SQ_WAIT,
- NULL);
- if (ret < 0)
- ret = -errno;
- return ret;
+ return ____sys_io_uring_enter(ring->ring_fd, 0, 0, IORING_ENTER_SQ_WAIT,
+ NULL);
}
diff --git a/src/register.c b/src/register.c
index 5ea4331..944852e 100644
--- a/src/register.c
+++ b/src/register.c
@@ -26,12 +26,10 @@ int io_uring_register_buffers_update_tag(struct io_uring *ring, unsigned off,
.tags = (unsigned long)tags,
.nr = nr,
};
- int ret;
- ret = __sys_io_uring_register(ring->ring_fd,
- IORING_REGISTER_BUFFERS_UPDATE,
- &up, sizeof(up));
- return ret < 0 ? -errno : ret;
+ return ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_BUFFERS_UPDATE, &up,
+ sizeof(up));
}
int io_uring_register_buffers_tags(struct io_uring *ring,
@@ -44,11 +42,10 @@ int io_uring_register_buffers_tags(struct io_uring *ring,
.data = (unsigned long)iovecs,
.tags = (unsigned long)tags,
};
- int ret;
- ret = __sys_io_uring_register(ring->ring_fd, IORING_REGISTER_BUFFERS2,
- ®, sizeof(reg));
- return ret < 0 ? -errno : ret;
+ return ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_BUFFERS2, ®,
+ sizeof(reg));
}
int io_uring_register_buffers(struct io_uring *ring, const struct iovec *iovecs,
@@ -56,24 +53,18 @@ int io_uring_register_buffers(struct io_uring *ring, const struct iovec *iovecs,
{
int ret;
- ret = __sys_io_uring_register(ring->ring_fd, IORING_REGISTER_BUFFERS,
+ ret = ____sys_io_uring_register(ring->ring_fd, IORING_REGISTER_BUFFERS,
iovecs, nr_iovecs);
- if (ret < 0)
- return -errno;
-
- return 0;
+ return (ret < 0) ? ret : 0;
}
int io_uring_unregister_buffers(struct io_uring *ring)
{
int ret;
- ret = __sys_io_uring_register(ring->ring_fd, IORING_UNREGISTER_BUFFERS,
+ ret = ____sys_io_uring_register(ring->ring_fd, IORING_UNREGISTER_BUFFERS,
NULL, 0);
- if (ret < 0)
- return -errno;
-
- return 0;
+ return (ret < 0) ? ret : 0;
}
int io_uring_register_files_update_tag(struct io_uring *ring, unsigned off,
@@ -86,12 +77,10 @@ int io_uring_register_files_update_tag(struct io_uring *ring, unsigned off,
.tags = (unsigned long)tags,
.nr = nr_files,
};
- int ret;
- ret = __sys_io_uring_register(ring->ring_fd,
- IORING_REGISTER_FILES_UPDATE2,
- &up, sizeof(up));
- return ret < 0 ? -errno : ret;
+ return ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_FILES_UPDATE2, &up,
+ sizeof(up));
}
/*
@@ -108,15 +97,10 @@ int io_uring_register_files_update(struct io_uring *ring, unsigned off,
.offset = off,
.fds = (unsigned long) files,
};
- int ret;
-
- ret = __sys_io_uring_register(ring->ring_fd,
- IORING_REGISTER_FILES_UPDATE, &up,
- nr_files);
- if (ret < 0)
- return -errno;
- return ret;
+ return ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_FILES_UPDATE, &up,
+ nr_files);
}
static int increase_rlimit_nofile(unsigned nr)
@@ -145,12 +129,12 @@ int io_uring_register_files_tags(struct io_uring *ring,
int ret, did_increase = 0;
do {
- ret = __sys_io_uring_register(ring->ring_fd,
- IORING_REGISTER_FILES2, ®,
- sizeof(reg));
+ ret = ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_FILES2, ®,
+ sizeof(reg));
if (ret >= 0)
break;
- if (errno == EMFILE && !did_increase) {
+ if (ret == -EMFILE && !did_increase) {
did_increase = 1;
increase_rlimit_nofile(nr);
continue;
@@ -158,7 +142,7 @@ int io_uring_register_files_tags(struct io_uring *ring,
break;
} while (1);
- return ret < 0 ? -errno : ret;
+ return (ret < 0) ? ret : 0;
}
int io_uring_register_files(struct io_uring *ring, const int *files,
@@ -167,12 +151,12 @@ int io_uring_register_files(struct io_uring *ring, const int *files,
int ret, did_increase = 0;
do {
- ret = __sys_io_uring_register(ring->ring_fd,
- IORING_REGISTER_FILES, files,
- nr_files);
+ ret = ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_FILES, files,
+ nr_files);
if (ret >= 0)
break;
- if (errno == EMFILE && !did_increase) {
+ if (ret == -EMFILE && !did_increase) {
did_increase = 1;
increase_rlimit_nofile(nr_files);
continue;
@@ -180,55 +164,44 @@ int io_uring_register_files(struct io_uring *ring, const int *files,
break;
} while (1);
- return ret < 0 ? -errno : ret;
+ return (ret < 0) ? ret : 0;
}
int io_uring_unregister_files(struct io_uring *ring)
{
int ret;
- ret = __sys_io_uring_register(ring->ring_fd, IORING_UNREGISTER_FILES,
+ ret = ____sys_io_uring_register(ring->ring_fd, IORING_UNREGISTER_FILES,
NULL, 0);
- if (ret < 0)
- return -errno;
-
- return 0;
+ return (ret < 0) ? ret : 0;
}
int io_uring_register_eventfd(struct io_uring *ring, int event_fd)
{
int ret;
- ret = __sys_io_uring_register(ring->ring_fd, IORING_REGISTER_EVENTFD,
+ ret = ____sys_io_uring_register(ring->ring_fd, IORING_REGISTER_EVENTFD,
&event_fd, 1);
- if (ret < 0)
- return -errno;
-
- return 0;
+ return (ret < 0) ? ret : 0;
}
int io_uring_unregister_eventfd(struct io_uring *ring)
{
int ret;
- ret = __sys_io_uring_register(ring->ring_fd, IORING_UNREGISTER_EVENTFD,
- NULL, 0);
- if (ret < 0)
- return -errno;
-
- return 0;
+ ret = ____sys_io_uring_register(ring->ring_fd,
+ IORING_UNREGISTER_EVENTFD, NULL, 0);
+ return (ret < 0) ? ret : 0;
}
int io_uring_register_eventfd_async(struct io_uring *ring, int event_fd)
{
int ret;
- ret = __sys_io_uring_register(ring->ring_fd, IORING_REGISTER_EVENTFD_ASYNC,
- &event_fd, 1);
- if (ret < 0)
- return -errno;
-
- return 0;
+ ret = ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_EVENTFD_ASYNC,
+ &event_fd, 1);
+ return (ret < 0) ? ret : 0;
}
int io_uring_register_probe(struct io_uring *ring, struct io_uring_probe *p,
@@ -236,36 +209,22 @@ int io_uring_register_probe(struct io_uring *ring, struct io_uring_probe *p,
{
int ret;
- ret = __sys_io_uring_register(ring->ring_fd, IORING_REGISTER_PROBE,
- p, nr_ops);
- if (ret < 0)
- return -errno;
-
- return 0;
+ ret = ____sys_io_uring_register(ring->ring_fd, IORING_REGISTER_PROBE, p,
+ nr_ops);
+ return (ret < 0) ? ret : 0;
}
int io_uring_register_personality(struct io_uring *ring)
{
- int ret;
-
- ret = __sys_io_uring_register(ring->ring_fd, IORING_REGISTER_PERSONALITY,
- NULL, 0);
- if (ret < 0)
- return -errno;
-
- return ret;
+ return ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_PERSONALITY, NULL, 0);
}
int io_uring_unregister_personality(struct io_uring *ring, int id)
{
- int ret;
-
- ret = __sys_io_uring_register(ring->ring_fd, IORING_UNREGISTER_PERSONALITY,
- NULL, id);
- if (ret < 0)
- return -errno;
-
- return ret;
+ return ____sys_io_uring_register(ring->ring_fd,
+ IORING_UNREGISTER_PERSONALITY, NULL,
+ id);
}
int io_uring_register_restrictions(struct io_uring *ring,
@@ -274,61 +233,34 @@ int io_uring_register_restrictions(struct io_uring *ring,
{
int ret;
- ret = __sys_io_uring_register(ring->ring_fd, IORING_REGISTER_RESTRICTIONS,
- res, nr_res);
- if (ret < 0)
- return -errno;
-
- return 0;
+ ret = ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_RESTRICTIONS, res,
+ nr_res);
+ return (ret < 0) ? ret : 0;
}
int io_uring_enable_rings(struct io_uring *ring)
{
- int ret;
-
- ret = __sys_io_uring_register(ring->ring_fd,
- IORING_REGISTER_ENABLE_RINGS, NULL, 0);
- if (ret < 0)
- return -errno;
-
- return ret;
+ return ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_ENABLE_RINGS, NULL, 0);
}
int io_uring_register_iowq_aff(struct io_uring *ring, size_t cpusz,
const cpu_set_t *mask)
{
- int ret;
-
- ret = __sys_io_uring_register(ring->ring_fd,
- IORING_REGISTER_IOWQ_AFF, mask, cpusz);
- if (ret < 0)
- return -errno;
-
- return ret;
+ return ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_IOWQ_AFF, mask, cpusz);
}
int io_uring_unregister_iowq_aff(struct io_uring *ring)
{
- int ret;
-
- ret = __sys_io_uring_register(ring->ring_fd,
- IORING_REGISTER_IOWQ_AFF, NULL, 0);
- if (ret < 0)
- return -errno;
-
- return ret;
+ return ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_IOWQ_AFF, NULL, 0);
}
int io_uring_register_iowq_max_workers(struct io_uring *ring, unsigned int *val)
{
- int ret;
-
- ret = __sys_io_uring_register(ring->ring_fd,
- IORING_REGISTER_IOWQ_MAX_WORKERS,
- val, 2);
- if (ret < 0)
- return -errno;
-
- return ret;
-
+ return ____sys_io_uring_register(ring->ring_fd,
+ IORING_REGISTER_IOWQ_MAX_WORKERS, val,
+ 2);
}
diff --git a/src/setup.c b/src/setup.c
index 54225e8..edfe94e 100644
--- a/src/setup.c
+++ b/src/setup.c
@@ -140,9 +140,9 @@ int io_uring_queue_init_params(unsigned entries, struct io_uring *ring,
{
int fd, ret;
- fd = __sys_io_uring_setup(entries, p);
+ fd = ____sys_io_uring_setup(entries, p);
if (fd < 0)
- return -errno;
+ return fd;
ret = io_uring_queue_mmap(fd, p, ring);
if (ret) {
diff --git a/src/syscall.c b/src/syscall.c
index 69027e5..0ecc17b 100644
--- a/src/syscall.c
+++ b/src/syscall.c
@@ -4,6 +4,7 @@
/*
* Will go away once libc support is there
*/
+#include <errno.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/uio.h>
@@ -59,15 +60,53 @@ int __sys_io_uring_setup(unsigned entries, struct io_uring_params *p)
}
int __sys_io_uring_enter2(int fd, unsigned to_submit, unsigned min_complete,
- unsigned flags, sigset_t *sig, int sz)
+ unsigned flags, sigset_t *sig, int sz)
{
return syscall(__NR_io_uring_enter, fd, to_submit, min_complete,
- flags, sig, sz);
+ flags, sig, sz);
}
int __sys_io_uring_enter(int fd, unsigned to_submit, unsigned min_complete,
unsigned flags, sigset_t *sig)
{
return __sys_io_uring_enter2(fd, to_submit, min_complete, flags, sig,
- _NSIG / 8);
+ _NSIG / 8);
+}
+
+
+/*
+ * Syscall with kernel style return value.
+ */
+int ____sys_io_uring_register(int fd, unsigned opcode, const void *arg,
+ unsigned nr_args)
+{
+ int ret;
+
+ ret = syscall(__NR_io_uring_register, fd, opcode, arg, nr_args);
+ return (ret < 0) ? -errno : ret;
+}
+
+int ____sys_io_uring_setup(unsigned entries, struct io_uring_params *p)
+{
+ int ret;
+
+ ret = syscall(__NR_io_uring_setup, entries, p);
+ return (ret < 0) ? -errno : ret;
+}
+
+int ____sys_io_uring_enter2(int fd, unsigned to_submit, unsigned min_complete,
+ unsigned flags, sigset_t *sig, int sz)
+{
+ int ret;
+
+ ret = syscall(__NR_io_uring_enter, fd, to_submit, min_complete,
+ flags, sig, sz);
+ return (ret < 0) ? -errno : ret;
+}
+
+int ____sys_io_uring_enter(int fd, unsigned to_submit, unsigned min_complete,
+ unsigned flags, sigset_t *sig)
+{
+ return ____sys_io_uring_enter2(fd, to_submit, min_complete, flags, sig,
+ _NSIG / 8);
}
diff --git a/src/syscall.h b/src/syscall.h
index 2368f83..8cd2d4c 100644
--- a/src/syscall.h
+++ b/src/syscall.h
@@ -17,4 +17,12 @@ int __sys_io_uring_enter2(int fd, unsigned to_submit, unsigned min_complete,
int __sys_io_uring_register(int fd, unsigned int opcode, const void *arg,
unsigned int nr_args);
+int ____sys_io_uring_setup(unsigned entries, struct io_uring_params *p);
+int ____sys_io_uring_enter(int fd, unsigned to_submit, unsigned min_complete,
+ unsigned flags, sigset_t *sig);
+int ____sys_io_uring_enter2(int fd, unsigned to_submit, unsigned min_complete,
+ unsigned flags, sigset_t *sig, int sz);
+int ____sys_io_uring_register(int fd, unsigned int opcode, const void *arg,
+ unsigned int nr_args);
+
#endif
--
2.30.2
