From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: [PATCH for 5.1 2/3] rseq: cleanup: remove rseq_len from task_struct Date: Tue, 5 Mar 2019 14:47:54 -0500 Message-ID: <20190305194755.2602-3-mathieu.desnoyers@efficios.com> References: <20190305194755.2602-1-mathieu.desnoyers@efficios.com> Return-path: In-Reply-To: <20190305194755.2602-1-mathieu.desnoyers@efficios.com> Sender: linux-kernel-owner@vger.kernel.org To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Peter Zijlstra , "Paul E . McKenney" , Boqun Feng , Andy Lutomirski , Dave Watson , Paul Turner , Andrew Morton , Russell King , Ingo Molnar , "H . Peter Anvin" , Andi Kleen , Chris Lameter , Ben Maurer , Steven Rostedt , Josh Triplett , Linus Torvalds , Catalin Marinas , Will Deacon , Michael Kerrisk List-Id: linux-api@vger.kernel.org The rseq system call, when invoked with flags of "0" or "RSEQ_FLAG_UNREGISTER" values, expects the rseq_len parameter to be equal to sizeof(struct rseq), which is fixed-size and fixed-layout, specified in uapi linux/rseq.h. Expecting a fixed size for rseq_len is a design choice that ensures multiple libraries and application defining __rseq_abi in the same process agree on its exact size. Considering that this size is and will always be the same value, there is no point in saving this value within task_struct rseq_len. Remove this field from task_struct. Signed-off-by: Mathieu Desnoyers CC: "Paul E. McKenney" CC: Peter Zijlstra CC: Paul Turner CC: Thomas Gleixner CC: Andy Lutomirski CC: Andi Kleen CC: Dave Watson CC: Chris Lameter CC: Ingo Molnar CC: "H. Peter Anvin" CC: Ben Maurer CC: Steven Rostedt CC: Josh Triplett CC: Linus Torvalds CC: Andrew Morton CC: Russell King CC: Catalin Marinas CC: Will Deacon CC: Michael Kerrisk CC: Boqun Feng CC: linux-api@vger.kernel.org --- include/linux/sched.h | 4 ---- kernel/rseq.c | 6 ++---- 2 files changed, 2 insertions(+), 8 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index f9b43c989577..e355688fa82c 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1059,7 +1059,6 @@ struct task_struct { #ifdef CONFIG_RSEQ struct rseq __user *rseq; - u32 rseq_len; u32 rseq_sig; /* * RmW on rseq_event_mask must be performed atomically @@ -1852,12 +1851,10 @@ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags) { if (clone_flags & CLONE_THREAD) { t->rseq = NULL; - t->rseq_len = 0; t->rseq_sig = 0; t->rseq_event_mask = 0; } else { t->rseq = current->rseq; - t->rseq_len = current->rseq_len; t->rseq_sig = current->rseq_sig; t->rseq_event_mask = current->rseq_event_mask; } @@ -1866,7 +1863,6 @@ static inline void rseq_fork(struct task_struct *t, unsigned long clone_flags) static inline void rseq_execve(struct task_struct *t) { t->rseq = NULL; - t->rseq_len = 0; t->rseq_sig = 0; t->rseq_event_mask = 0; } diff --git a/kernel/rseq.c b/kernel/rseq.c index 849afe749131..9424ee90589e 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -313,7 +313,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, /* Unregister rseq for current thread. */ if (current->rseq != rseq || !current->rseq) return -EINVAL; - if (current->rseq_len != rseq_len) + if (rseq_len != sizeof(*rseq)) return -EINVAL; if (current->rseq_sig != sig) return -EPERM; @@ -321,7 +321,6 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, if (ret) return ret; current->rseq = NULL; - current->rseq_len = 0; current->rseq_sig = 0; return 0; } @@ -335,7 +334,7 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, * the provided address differs from the prior * one. */ - if (current->rseq != rseq || current->rseq_len != rseq_len) + if (current->rseq != rseq || rseq_len != sizeof(*rseq)) return -EINVAL; if (current->rseq_sig != sig) return -EPERM; @@ -353,7 +352,6 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len, if (!access_ok(rseq, rseq_len)) return -EFAULT; current->rseq = rseq; - current->rseq_len = rseq_len; current->rseq_sig = sig; /* * If rseq was previously inactive, and has just been -- 2.11.0