[PATCH 31/45] ipc: add semget syscall wrapper

From: Dominik Brodowski
Date: Thu Mar 22 2018 - 05:02:54 EST


Provide ksys_semget() wrapper to avoid in-kernel calls to this syscall.
The ksys_ prefix denotes that this function is meant as a drop-in
replacement for the syscall. In particular, it uses the same calling
convention as sys_semget().

This patch is part of a series which tries to remove in-kernel calls to
syscalls. On this basis, the syscall entry path can be streamlined.

Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
---
ipc/sem.c | 7 ++++++-
ipc/syscall.c | 4 ++--
ipc/util.h | 1 +
3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/ipc/sem.c b/ipc/sem.c
index e21ceb8b4af1..2e5f7ec7a7db 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -556,7 +556,7 @@ static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
return 0;
}

-SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
+long ksys_semget(key_t key, int nsems, int semflg)
{
struct ipc_namespace *ns;
static const struct ipc_ops sem_ops = {
@@ -578,6 +578,11 @@ SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
}

+SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
+{
+ return ksys_semget(key, nsems, semflg);
+}
+
/**
* perform_atomic_semop[_slow] - Attempt to perform semaphore
* operations on a given array.
diff --git a/ipc/syscall.c b/ipc/syscall.c
index 84d6a7691baa..21fcdf0b4836 100644
--- a/ipc/syscall.c
+++ b/ipc/syscall.c
@@ -35,7 +35,7 @@ SYSCALL_DEFINE6(ipc, unsigned int, call, int, first, unsigned long, second,
(const struct timespec __user *)fifth);

case SEMGET:
- return sys_semget(first, second, third);
+ return ksys_semget(first, second, third);
case SEMCTL: {
unsigned long arg;
if (!ptr)
@@ -132,7 +132,7 @@ COMPAT_SYSCALL_DEFINE6(ipc, u32, call, int, first, int, second,
return compat_ksys_semtimedop(first, compat_ptr(ptr), second,
compat_ptr(fifth));
case SEMGET:
- return sys_semget(first, second, third);
+ return ksys_semget(first, second, third);
case SEMCTL:
if (!ptr)
return -EINVAL;
diff --git a/ipc/util.h b/ipc/util.h
index 6deadf77547e..0f07056e5a73 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -240,6 +240,7 @@ static inline int compat_ipc_parse_version(int *cmd)
long ksys_semtimedop(int semid, struct sembuf __user *tsops,
unsigned int nsops,
const struct timespec __user *timeout);
+long ksys_semget(key_t key, int nsems, int semflg);

/* for CONFIG_ARCH_WANT_OLD_COMPAT_IPC */
#ifdef CONFIG_COMPAT
--
2.16.2