linux-api.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=436937568.1359.1530905019620.JavaMail.zimbra@efficios.com \
    --to=mathieu.desnoyers@efficios.com \
    --cc=akpm@linux-foundation.org \
    --cc=andi@firstfloor.org \
    --cc=bmaurer@fb.com \
    --cc=boqun.feng@gmail.com \
    --cc=catalin.marinas@arm.com \
    --cc=cl@linux.com \
    --cc=davejwatson@fb.com \
    --cc=hpa@zytor.com \
    --cc=josh@joshtriplett.org \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@arm.linux.org.uk \
    --cc=luto@amacapital.net \
    --cc=mingo@redhat.com \
    --cc=paulmck@linux.vnet.ibm.com \
    --cc=peterz@infradead.org \
    --cc=pjt@google.com \
    --cc=rostedt@goodmis.org \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --cc=will.deacon@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).