From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Andy Lutomirski <luto@amacapital.net>,
Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Russell King <linux@arm.linux.org.uk>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>,
Ben Maurer <bmaurer@fb.com>, rostedt <rostedt@goodmis.org>,
Josh Triplett <josh@joshtriplett.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Michael
Subject: Re: [RFC PATCH for 4.18 3/5] rseq: uapi: declare rseq_cs field as union, update includes
Date: Fri, 6 Jul 2018 15:23:39 -0400 (EDT) [thread overview]
Message-ID: <436937568.1359.1530905019620.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <1846432971.1245.1530892973439.JavaMail.zimbra@efficios.com>
----- On Jul 6, 2018, at 12:02 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
> ----- On Jul 5, 2018, at 2:05 PM, Mathieu Desnoyers
> mathieu.desnoyers@efficios.com wrote:
>
[...]
> The 0-day bot noticed that __get_user() is unimplemented for 64-bit
> values on arm32 (although get_user() is implemented).
>
> The following diff fixes this discrepancy, and allows this rseq patch
> to build on arm32:
>
For -rc, I would favor the following simpler approach. Or I could even
just use get_user() instead. Thoughts ?
rseq: implement work-around for missing 8-byte __get_user on arm
Now that rseq uses __u64 for its pointer fields, 32-bit architectures
need to read this 64-bit value from user-space.
__get_user is used to read this value, given that its access check has
already been performed with access_ok() on rseq registration.
arm does not implement 8-byte __get_user. Work-around this limitation
by using get_user() on ARM instead, with its redundant access check.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: Thomas Gleixner <tglx@linutronix.de>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Chris Lameter <cl@linux.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Andrew Hunter <ahh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Maurer <bmaurer@fb.com>
Cc: linux-api@vger.kernel.org
CC: linux-arm-kernel@lists.infradead.org
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/rseq.c b/kernel/rseq.c
index 3081e67..0e67625 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -18,6 +18,16 @@
#define CREATE_TRACE_POINTS
#include <trace/events/rseq.h>
+/*
+ * ARM does not implement 8 bytes __get_user. Use get_user on that
+ * architecture instead.
+ */
+#ifdef CONFIG_ARM
+#define __rseq_get_user get_user
+#else
+#define __rseq_get_user __get_user
+#endif
+
#define RSEQ_CS_PREEMPT_MIGRATE_FLAGS (RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE | \
RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT)
@@ -120,7 +130,7 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rs
u32 sig;
int ret;
- ret = __get_user(ptr, &t->rseq->rseq_cs.ptr64);
+ ret = __rseq_get_user(ptr, &t->rseq->rseq_cs.ptr64);
if (ret)
return ret;
if (!ptr) {
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2018-07-06 19:23 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-05 18:05 [RFC PATCH for 4.18 0/5] Restartable Sequences updates Mathieu Desnoyers
2018-07-05 18:05 ` [RFC PATCH for 4.18 1/5] rseq: use __u64 for rseq_cs fields, validate user inputs Mathieu Desnoyers
2018-07-05 18:05 ` [RFC PATCH for 4.18 2/5] rseq: uapi: update uapi comments Mathieu Desnoyers
2018-07-05 18:05 ` [RFC PATCH for 4.18 3/5] rseq: uapi: declare rseq_cs field as union, update includes Mathieu Desnoyers
2018-07-06 16:02 ` Mathieu Desnoyers
2018-07-06 19:23 ` Mathieu Desnoyers [this message]
2018-07-06 19:31 ` Linus Torvalds
2018-07-06 19:35 ` Mathieu Desnoyers
2018-07-06 19:38 ` Mathieu Desnoyers
2018-07-06 19:56 ` Linus Torvalds
2018-07-07 15:06 ` Russell King - ARM Linux
2018-07-06 19:56 ` Andy Lutomirski
2018-07-05 18:06 ` [RFC PATCH for 4.18 4/5] rseq: remove unused types_32_64.h uapi header Mathieu Desnoyers
2018-07-05 18:06 ` [RFC PATCH for 4.18 5/5] rseq/selftests: cleanup: update comment above rseq_prepare_unload Mathieu Desnoyers
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