[PATCH for 4.18 0/6] Restartable Sequences updates

[PATCH for 4.18 0/6] Restartable Sequences updates

[Mathieu Desnoyers]

Following the recent discussion thread [1] about rseq uapi, here is
a set of updates submitted for integration into 4.18. Those change all
rseq __get_user/__put_user for get_user/put_user as discussed.

Thanks,

Mathieu

[1] https://lkml.kernel.org/r/20180702223143.4663-1-mathieu.desnoyers@efficios.com

Mathieu Desnoyers (6):
  rseq: use __u64 for rseq_cs fields, validate user inputs
  rseq: use get_user/put_user rather than __get_user/__put_user
  rseq: uapi: update uapi comments
  rseq: uapi: declare rseq_cs field as union, update includes
  rseq: remove unused types_32_64.h uapi header
  rseq/selftests: cleanup: update comment above rseq_prepare_unload

 include/uapi/linux/rseq.h           | 102 ++++++++++++++++++++----------------
 include/uapi/linux/types_32_64.h    |  50 ------------------
 kernel/rseq.c                       |  36 ++++++++-----
 tools/testing/selftests/rseq/rseq.h |  24 ++++++---
 4 files changed, 97 insertions(+), 115 deletions(-)
 delete mode 100644 include/uapi/linux/types_32_64.h

-- 
2.11.0

[PATCH for 4.18 1/6] rseq: use __u64 for rseq_cs fields, validate user inputs

[Mathieu Desnoyers]

Change the rseq ABI so rseq_cs start_ip, post_commit_offset and abort_ip
fields are seen as 64-bit fields by both 32-bit and 64-bit kernels rather
that ignoring the 32 upper bits on 32-bit kernels. This ensures we have a
consistent behavior for a 32-bit binary executed on 32-bit kernels and in
compat mode on 64-bit kernels.

Validating the value of abort_ip field to be below TASK_SIZE ensures the
kernel don't return to an invalid address when returning to userspace
after an abort. I don't fully trust each architecture code to consistently
deal with invalid return addresses.

Validating the value of the start_ip and post_commit_offset fields
prevents overflow on arithmetic performed on those values, used to
check whether abort_ip is within the rseq critical section.

If validation fails, the process is killed with a segmentation fault.

When the signature encountered before abort_ip does not match the expected
signature, return -EINVAL rather than -EPERM to be consistent with other
input validation return codes from rseq_get_rseq_cs().

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Paul Turner <pjt@google.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Andi Kleen <andi@firstfloor.org>
CC: Dave Watson <davejwatson@fb.com>
CC: Chris Lameter <cl@linux.com>
CC: Ingo Molnar <mingo@redhat.com>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Ben Maurer <bmaurer@fb.com>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Russell King <linux@arm.linux.org.uk>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: linux-api@vger.kernel.org
---
 include/uapi/linux/rseq.h |  6 +++---
 kernel/rseq.c             | 14 ++++++++++----
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h
index d620fa43756c..519ad6e176d1 100644
--- a/include/uapi/linux/rseq.h
+++ b/include/uapi/linux/rseq.h
@@ -52,10 +52,10 @@ struct rseq_cs {
 	__u32 version;
 	/* enum rseq_cs_flags */
 	__u32 flags;
-	LINUX_FIELD_u32_u64(start_ip);
+	__u64 start_ip;
 	/* Offset from start_ip. */
-	LINUX_FIELD_u32_u64(post_commit_offset);
-	LINUX_FIELD_u32_u64(abort_ip);
+	__u64 post_commit_offset;
+	__u64 abort_ip;
 } __attribute__((aligned(4 * sizeof(__u64))));
 
 /*
diff --git a/kernel/rseq.c b/kernel/rseq.c
index 22b6acf1ad63..16b38c5342f9 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -130,14 +130,20 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs)
 	urseq_cs = (struct rseq_cs __user *)ptr;
 	if (copy_from_user(rseq_cs, urseq_cs, sizeof(*rseq_cs)))
 		return -EFAULT;
-	if (rseq_cs->version > 0)
-		return -EINVAL;
 
+	if (rseq_cs->start_ip >= TASK_SIZE ||
+	    rseq_cs->start_ip + rseq_cs->post_commit_offset >= TASK_SIZE ||
+	    rseq_cs->abort_ip >= TASK_SIZE ||
+	    rseq_cs->version > 0)
+		return -EINVAL;
+	/* Check for overflow. */
+	if (rseq_cs->start_ip + rseq_cs->post_commit_offset < rseq_cs->start_ip)
+		return -EINVAL;
 	/* Ensure that abort_ip is not in the critical section. */
 	if (rseq_cs->abort_ip - rseq_cs->start_ip < rseq_cs->post_commit_offset)
 		return -EINVAL;
 
-	usig = (u32 __user *)(rseq_cs->abort_ip - sizeof(u32));
+	usig = (u32 __user *)(unsigned long)(rseq_cs->abort_ip - sizeof(u32));
 	ret = get_user(sig, usig);
 	if (ret)
 		return ret;
@@ -146,7 +152,7 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs)
 		printk_ratelimited(KERN_WARNING
 			"Possible attack attempt. Unexpected rseq signature 0x%x, expecting 0x%x (pid=%d, addr=%p).\n",
 			sig, current->rseq_sig, current->pid, usig);
-		return -EPERM;
+		return -EINVAL;
 	}
 	return 0;
 }
-- 
2.11.0

[PATCH for 4.18 2/6] rseq: use get_user/put_user rather than __get_user/__put_user

[Mathieu Desnoyers]

In preparation to use __u64 for the rseq_cs pointer field, 32-bit
architectures need to read this 64-bit value located in user-space
addresses.

__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. Rather than trying to
improve __get_user on ARM, use get_user/put_user across rseq instead.

If those end up showing up in benchmarks, the proper approach would be to
use user_access_begin() / unsafe_get/put_user() / user_access_end()
anyway.

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>
---
 kernel/rseq.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/rseq.c b/kernel/rseq.c
index 16b38c5342f9..2c8463acb50d 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -85,9 +85,9 @@ static int rseq_update_cpu_id(struct task_struct *t)
 {
 	u32 cpu_id = raw_smp_processor_id();
 
-	if (__put_user(cpu_id, &t->rseq->cpu_id_start))
+	if (put_user(cpu_id, &t->rseq->cpu_id_start))
 		return -EFAULT;
-	if (__put_user(cpu_id, &t->rseq->cpu_id))
+	if (put_user(cpu_id, &t->rseq->cpu_id))
 		return -EFAULT;
 	trace_rseq_update(t);
 	return 0;
@@ -100,14 +100,14 @@ static int rseq_reset_rseq_cpu_id(struct task_struct *t)
 	/*
 	 * Reset cpu_id_start to its initial state (0).
 	 */
-	if (__put_user(cpu_id_start, &t->rseq->cpu_id_start))
+	if (put_user(cpu_id_start, &t->rseq->cpu_id_start))
 		return -EFAULT;
 	/*
 	 * Reset cpu_id to RSEQ_CPU_ID_UNINITIALIZED, so any user coming
 	 * in after unregistration can figure out that rseq needs to be
 	 * registered again.
 	 */
-	if (__put_user(cpu_id, &t->rseq->cpu_id))
+	if (put_user(cpu_id, &t->rseq->cpu_id))
 		return -EFAULT;
 	return 0;
 }
@@ -120,7 +120,7 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs)
 	u32 sig;
 	int ret;
 
-	ret = __get_user(ptr, &t->rseq->rseq_cs);
+	ret = get_user(ptr, &t->rseq->rseq_cs);
 	if (ret)
 		return ret;
 	if (!ptr) {
@@ -163,7 +163,7 @@ static int rseq_need_restart(struct task_struct *t, u32 cs_flags)
 	int ret;
 
 	/* Get thread flags. */
-	ret = __get_user(flags, &t->rseq->flags);
+	ret = get_user(flags, &t->rseq->flags);
 	if (ret)
 		return ret;
 
@@ -203,7 +203,7 @@ static int clear_rseq_cs(struct task_struct *t)
 	 *
 	 * Set rseq_cs to NULL with single-copy atomicity.
 	 */
-	return __put_user(0UL, &t->rseq->rseq_cs);
+	return put_user(0UL, &t->rseq->rseq_cs);
 }
 
 /*
-- 
2.11.0

Re: [PATCH for 4.18 2/6] rseq: use get_user/put_user rather than __get_user/__put_user

[Mathieu Desnoyers]

----- On Jul 8, 2018, at 5:03 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:

> In preparation to use __u64 for the rseq_cs pointer field, 32-bit
> architectures need to read this 64-bit value located in user-space
> addresses.
> 
> __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. Rather than trying to
> improve __get_user on ARM, use get_user/put_user across rseq instead.
> 
> If those end up showing up in benchmarks, the proper approach would be to
> use user_access_begin() / unsafe_get/put_user() / user_access_end()
> anyway.

So, another twist to this story: ppc32 does not implement u64 get_user().

I am tempted to ditch this patch (leaving the __get_user()/__put_user as is
for 32-bit accesses), and simply use __copy_from_user()/__copy_to_user() to
load/store the rseq_cs pointer. Considering that we don't need to load/store
the rseq_cs field with single-copy atomicity from the kernel anymore, it
should be fine.

Any objection ?

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/rseq/linux-rseq.git rseq/dev
head:   a100323919af0c11a150a9ba58c3f8ac986ea42d
commit: 23d0f99d280fa97ebcf8b915157468f457bc6e11 [4/21] rseq: uapi: declare rseq_cs field as union, update includes
config: powerpc-ppc6xx_defconfig (attached as .config)
compiler: powerpc-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout 23d0f99d280fa97ebcf8b915157468f457bc6e11
        # save the attached .config to linux build tree
        GCC_VERSION=7.2.0 make.cross ARCH=powerpc

All errors (new ones prefixed by >>):

   kernel/rseq.o: In function `__rseq_handle_notify_resume':
>> (.text+0x648): undefined reference to `__get_user_bad'

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Thanks,

Mathieu

> 
> 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>
> ---
> kernel/rseq.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/rseq.c b/kernel/rseq.c
> index 16b38c5342f9..2c8463acb50d 100644
> --- a/kernel/rseq.c
> +++ b/kernel/rseq.c
> @@ -85,9 +85,9 @@ static int rseq_update_cpu_id(struct task_struct *t)
> {
> 	u32 cpu_id = raw_smp_processor_id();
> 
> -	if (__put_user(cpu_id, &t->rseq->cpu_id_start))
> +	if (put_user(cpu_id, &t->rseq->cpu_id_start))
> 		return -EFAULT;
> -	if (__put_user(cpu_id, &t->rseq->cpu_id))
> +	if (put_user(cpu_id, &t->rseq->cpu_id))
> 		return -EFAULT;
> 	trace_rseq_update(t);
> 	return 0;
> @@ -100,14 +100,14 @@ static int rseq_reset_rseq_cpu_id(struct task_struct *t)
> 	/*
> 	 * Reset cpu_id_start to its initial state (0).
> 	 */
> -	if (__put_user(cpu_id_start, &t->rseq->cpu_id_start))
> +	if (put_user(cpu_id_start, &t->rseq->cpu_id_start))
> 		return -EFAULT;
> 	/*
> 	 * Reset cpu_id to RSEQ_CPU_ID_UNINITIALIZED, so any user coming
> 	 * in after unregistration can figure out that rseq needs to be
> 	 * registered again.
> 	 */
> -	if (__put_user(cpu_id, &t->rseq->cpu_id))
> +	if (put_user(cpu_id, &t->rseq->cpu_id))
> 		return -EFAULT;
> 	return 0;
> }
> @@ -120,7 +120,7 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct
> rseq_cs *rseq_cs)
> 	u32 sig;
> 	int ret;
> 
> -	ret = __get_user(ptr, &t->rseq->rseq_cs);
> +	ret = get_user(ptr, &t->rseq->rseq_cs);
> 	if (ret)
> 		return ret;
> 	if (!ptr) {
> @@ -163,7 +163,7 @@ static int rseq_need_restart(struct task_struct *t, u32
> cs_flags)
> 	int ret;
> 
> 	/* Get thread flags. */
> -	ret = __get_user(flags, &t->rseq->flags);
> +	ret = get_user(flags, &t->rseq->flags);
> 	if (ret)
> 		return ret;
> 
> @@ -203,7 +203,7 @@ static int clear_rseq_cs(struct task_struct *t)
> 	 *
> 	 * Set rseq_cs to NULL with single-copy atomicity.
> 	 */
> -	return __put_user(0UL, &t->rseq->rseq_cs);
> +	return put_user(0UL, &t->rseq->rseq_cs);
> }
> 
> /*
> --
> 2.11.0

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

Re: [PATCH for 4.18 2/6] rseq: use get_user/put_user rather than __get_user/__put_user

[Linus Torvalds]

On Mon, Jul 9, 2018 at 10:28 AM Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
>
> So, another twist to this story: ppc32 does not implement u64 get_user().

I was going to say that "that's not possible", since we actually have
64-bit arguments at least in the form of "loff_t __user *".

But when I started looking, it turns out that yeah, we do
"copy_from_user()" on them, and instead made the x86 copy_from_user()
have special cases for constant sizes.

So a 8-byte copy_from_user() is fine. It ends up being a "get_user()"
on x86 anyway.

                Linus

Re: [PATCH for 4.18 2/6] rseq: use get_user/put_user rather than __get_user/__put_user

[Mathieu Desnoyers]

----- On Jul 9, 2018, at 2:04 PM, Linus Torvalds torvalds@linux-foundation.org wrote:

> On Mon, Jul 9, 2018 at 10:28 AM Mathieu Desnoyers
> <mathieu.desnoyers@efficios.com> wrote:
>>
>> So, another twist to this story: ppc32 does not implement u64 get_user().
> 
> I was going to say that "that's not possible", since we actually have
> 64-bit arguments at least in the form of "loff_t __user *".
> 
> But when I started looking, it turns out that yeah, we do
> "copy_from_user()" on them, and instead made the x86 copy_from_user()
> have special cases for constant sizes.
> 
> So a 8-byte copy_from_user() is fine. It ends up being a "get_user()"
> on x86 anyway.

Given that this memory area has already been checked with access_ok()
on rseq registration, are you fine with leaving
__get_user/__put_user/__copy_{from,to}_user in place so we do the
minimal change at this stage of rc, or should I go ahead and replace
the lot with get_user/put_user/copy_{from,to}_user ?

Thanks,

Mathieu


-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

Re: [PATCH for 4.18 2/6] rseq: use get_user/put_user rather than __get_user/__put_user

[Linus Torvalds]

On Mon, Jul 9, 2018 at 11:19 AM Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
>
> Given that this memory area has already been checked with access_ok()
> on rseq registration, are you fine with leaving
> __get_user/__put_user/__copy_{from,to}_user in place so we do the
> minimal change at this stage of rc, or should I go ahead and replace
> the lot with get_user/put_user/copy_{from,to}_user ?

Do the full replacement, and let's get this over and done with.

              Linus

Re: [PATCH for 4.18 2/6] rseq: use get_user/put_user rather than __get_user/__put_user

[Michael Ellerman]

Mathieu Desnoyers <mathieu.desnoyers@efficios.com> writes:
> ----- On Jul 8, 2018, at 5:03 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
>
>> In preparation to use __u64 for the rseq_cs pointer field, 32-bit
>> architectures need to read this 64-bit value located in user-space
>> addresses.
>> 
>> __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. Rather than trying to
>> improve __get_user on ARM, use get_user/put_user across rseq instead.
>> 
>> If those end up showing up in benchmarks, the proper approach would be to
>> use user_access_begin() / unsafe_get/put_user() / user_access_end()
>> anyway.
>
> So, another twist to this story: ppc32 does not implement u64 get_user().

Or __get_user() for that matter.

But we should just fix it.

We have the asm to do it, it's just the fact that __gu_val is unsigned
long causes the size > sizeof(x) check here to fail:

#define __get_user_size(x, ptr, size, retval)			\
do {								\
	retval = 0;						\
	__chk_user_ptr(ptr);					\
	if (size > sizeof(x))					\
		(x) = __get_user_bad();				\



We seem to be able to fix that with the __inttype() trick that x86 uses.

That's probably not 4.18 material though. But if you want to go with
copy_from_user() for now you could then switch to get_user() for 4.19.

cheers

Re: [PATCH for 4.18 2/6] rseq: use get_user/put_user rather than __get_user/__put_user

[Mathieu Desnoyers]

----- On Jul 10, 2018, at 2:16 AM, Michael Ellerman mpe@ellerman.id.au wrote:

> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> writes:
>> ----- On Jul 8, 2018, at 5:03 PM, Mathieu Desnoyers
>> mathieu.desnoyers@efficios.com wrote:
>>
>>> In preparation to use __u64 for the rseq_cs pointer field, 32-bit
>>> architectures need to read this 64-bit value located in user-space
>>> addresses.
>>> 
>>> __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. Rather than trying to
>>> improve __get_user on ARM, use get_user/put_user across rseq instead.
>>> 
>>> If those end up showing up in benchmarks, the proper approach would be to
>>> use user_access_begin() / unsafe_get/put_user() / user_access_end()
>>> anyway.
>>
>> So, another twist to this story: ppc32 does not implement u64 get_user().
> 
> Or __get_user() for that matter.
> 
> But we should just fix it.
> 
> We have the asm to do it, it's just the fact that __gu_val is unsigned
> long causes the size > sizeof(x) check here to fail:
> 
> #define __get_user_size(x, ptr, size, retval)			\
> do {								\
>	retval = 0;						\
>	__chk_user_ptr(ptr);					\
>	if (size > sizeof(x))					\
>		(x) = __get_user_bad();				\
> 
> 
> 
> We seem to be able to fix that with the __inttype() trick that x86 uses.
> 
> That's probably not 4.18 material though. But if you want to go with
> copy_from_user() for now you could then switch to get_user() for 4.19.

I agree. Let's use copy_from_user() for 4.18. Once get_user() ends up supporting
u64 on ppc32 for 4.19, rseq will happily move back to it.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

[PATCH for 4.18 3/6] rseq: uapi: update uapi comments

[Mathieu Desnoyers]

Update rseq uapi header comments to reflect that user-space need to do
thread-local loads/stores from/to the struct rseq fields.

As a consequence of this added requirement, the kernel does not need
to perform loads/stores with single-copy atomicity.

Update the comment associated to the "flags" fields to describe
more accurately that it's only useful to facilitate single-stepping
through rseq critical sections with debuggers.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Paul Turner <pjt@google.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Andi Kleen <andi@firstfloor.org>
CC: Dave Watson <davejwatson@fb.com>
CC: Chris Lameter <cl@linux.com>
CC: Ingo Molnar <mingo@redhat.com>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Ben Maurer <bmaurer@fb.com>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Russell King <linux@arm.linux.org.uk>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: linux-api@vger.kernel.org
---
 include/uapi/linux/rseq.h | 69 ++++++++++++++++++++++++-----------------------
 kernel/rseq.c             |  2 +-
 2 files changed, 37 insertions(+), 34 deletions(-)

diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h
index 519ad6e176d1..bf4188c13bec 100644
--- a/include/uapi/linux/rseq.h
+++ b/include/uapi/linux/rseq.h
@@ -67,28 +67,30 @@ struct rseq_cs {
 struct rseq {
 	/*
 	 * Restartable sequences cpu_id_start field. Updated by the
-	 * kernel, and read by user-space with single-copy atomicity
-	 * semantics. Aligned on 32-bit. Always contains a value in the
-	 * range of possible CPUs, although the value may not be the
-	 * actual current CPU (e.g. if rseq is not initialized). This
-	 * CPU number value should always be compared against the value
-	 * of the cpu_id field before performing a rseq commit or
-	 * returning a value read from a data structure indexed using
-	 * the cpu_id_start value.
+	 * kernel. Read by user-space with single-copy atomicity
+	 * semantics. This field should only be read by the thread which
+	 * registered this data structure. Aligned on 32-bit. Always
+	 * contains a value in the range of possible CPUs, although the
+	 * value may not be the actual current CPU (e.g. if rseq is not
+	 * initialized). This CPU number value should always be compared
+	 * against the value of the cpu_id field before performing a rseq
+	 * commit or returning a value read from a data structure indexed
+	 * using the cpu_id_start value.
 	 */
 	__u32 cpu_id_start;
 	/*
-	 * Restartable sequences cpu_id field. Updated by the kernel,
-	 * and read by user-space with single-copy atomicity semantics.
-	 * Aligned on 32-bit. Values RSEQ_CPU_ID_UNINITIALIZED and
-	 * RSEQ_CPU_ID_REGISTRATION_FAILED have a special semantic: the
-	 * former means "rseq uninitialized", and latter means "rseq
-	 * initialization failed". This value is meant to be read within
-	 * rseq critical sections and compared with the cpu_id_start
-	 * value previously read, before performing the commit instruction,
-	 * or read and compared with the cpu_id_start value before returning
-	 * a value loaded from a data structure indexed using the
-	 * cpu_id_start value.
+	 * Restartable sequences cpu_id field. Updated by the kernel.
+	 * Read by user-space with single-copy atomicity semantics. This
+	 * field should only be read by the thread which registered this
+	 * data structure. Aligned on 32-bit. Values
+	 * RSEQ_CPU_ID_UNINITIALIZED and RSEQ_CPU_ID_REGISTRATION_FAILED
+	 * have a special semantic: the former means "rseq uninitialized",
+	 * and latter means "rseq initialization failed". This value is
+	 * meant to be read within rseq critical sections and compared
+	 * with the cpu_id_start value previously read, before performing
+	 * the commit instruction, or read and compared with the
+	 * cpu_id_start value before returning a value loaded from a data
+	 * structure indexed using the cpu_id_start value.
 	 */
 	__u32 cpu_id;
 	/*
@@ -105,27 +107,28 @@ struct rseq {
 	 * targeted by the rseq_cs. Also needs to be set to NULL by user-space
 	 * before reclaiming memory that contains the targeted struct rseq_cs.
 	 *
-	 * Read and set by the kernel with single-copy atomicity semantics.
-	 * Set by user-space with single-copy atomicity semantics. Aligned
-	 * on 64-bit.
+	 * Read and set by the kernel. Set by user-space with single-copy
+	 * atomicity semantics. This field should only be updated by the
+	 * thread which registered this data structure. Aligned on 64-bit.
 	 */
 	LINUX_FIELD_u32_u64(rseq_cs);
 	/*
-	 * - RSEQ_DISABLE flag:
+	 * Restartable sequences flags field.
+	 *
+	 * This field should only be updated by the thread which
+	 * registered this data structure. Read by the kernel.
+	 * Mainly used for single-stepping through rseq critical sections
+	 * with debuggers.
 	 *
-	 * Fallback fast-track flag for single-stepping.
-	 * Set by user-space if lack of progress is detected.
-	 * Cleared by user-space after rseq finish.
-	 * Read by the kernel.
 	 * - RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT
-	 *     Inhibit instruction sequence block restart and event
-	 *     counter increment on preemption for this thread.
+	 *     Inhibit instruction sequence block restart on preemption
+	 *     for this thread.
 	 * - RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL
-	 *     Inhibit instruction sequence block restart and event
-	 *     counter increment on signal delivery for this thread.
+	 *     Inhibit instruction sequence block restart on signal
+	 *     delivery for this thread.
 	 * - RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE
-	 *     Inhibit instruction sequence block restart and event
-	 *     counter increment on migration for this thread.
+	 *     Inhibit instruction sequence block restart on migration for
+	 *     this thread.
 	 */
 	__u32 flags;
 } __attribute__((aligned(4 * sizeof(__u64))));
diff --git a/kernel/rseq.c b/kernel/rseq.c
index 2c8463acb50d..2a7748675be7 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -201,7 +201,7 @@ static int clear_rseq_cs(struct task_struct *t)
 	 * of code outside of the rseq assembly block. This performs
 	 * a lazy clear of the rseq_cs field.
 	 *
-	 * Set rseq_cs to NULL with single-copy atomicity.
+	 * Set rseq_cs to NULL.
 	 */
 	return put_user(0UL, &t->rseq->rseq_cs);
 }
-- 
2.11.0

[PATCH for 4.18 4/6] rseq: uapi: declare rseq_cs field as union, update includes

[Mathieu Desnoyers]

Declaring the rseq_cs field as a union between __u64 and two __u32
allows both 32-bit and 64-bit kernels to read the full __u64, and
therefore validate that a 32-bit user-space cleared the upper 32
bits, thus ensuring a consistent behavior between native 32-bit
kernels and 32-bit compat tasks on 64-bit kernels.

Check that the rseq_cs value read is < TASK_SIZE.

The asm/byteorder.h header needs to be included by rseq.h, now
that it is not using linux/types_32_64.h anymore.

Considering that only __32 and __u64 types are declared in linux/rseq.h,
the linux/types.h header should always be included for both kernel and
user-space code: including stdint.h is just for u64 and u32, which are
not used in this header at all.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Paul Turner <pjt@google.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Andi Kleen <andi@firstfloor.org>
CC: Dave Watson <davejwatson@fb.com>
CC: Chris Lameter <cl@linux.com>
CC: Ingo Molnar <mingo@redhat.com>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Ben Maurer <bmaurer@fb.com>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Russell King <linux@arm.linux.org.uk>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: linux-api@vger.kernel.org
---
 include/uapi/linux/rseq.h           | 27 +++++++++++++++++++--------
 kernel/rseq.c                       | 10 ++++++----
 tools/testing/selftests/rseq/rseq.h | 11 ++++++++++-
 3 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/include/uapi/linux/rseq.h b/include/uapi/linux/rseq.h
index bf4188c13bec..9a402fdb60e9 100644
--- a/include/uapi/linux/rseq.h
+++ b/include/uapi/linux/rseq.h
@@ -10,13 +10,8 @@
  * Copyright (c) 2015-2018 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  */
 
-#ifdef __KERNEL__
-# include <linux/types.h>
-#else
-# include <stdint.h>
-#endif
-
-#include <linux/types_32_64.h>
+#include <linux/types.h>
+#include <asm/byteorder.h>
 
 enum rseq_cpu_id_state {
 	RSEQ_CPU_ID_UNINITIALIZED		= -1,
@@ -111,7 +106,23 @@ struct rseq {
 	 * atomicity semantics. This field should only be updated by the
 	 * thread which registered this data structure. Aligned on 64-bit.
 	 */
-	LINUX_FIELD_u32_u64(rseq_cs);
+	union {
+		__u64 ptr64;
+#ifdef __LP64__
+		__u64 ptr;
+#else
+		struct {
+#if (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || defined(__BIG_ENDIAN)
+			__u32 padding;		/* Initialized to zero. */
+			__u32 ptr32;
+#else /* LITTLE */
+			__u32 ptr32;
+			__u32 padding;		/* Initialized to zero. */
+#endif /* ENDIAN */
+		} ptr;
+#endif
+	} rseq_cs;
+
 	/*
 	 * Restartable sequences flags field.
 	 *
diff --git a/kernel/rseq.c b/kernel/rseq.c
index 2a7748675be7..fcc5ea1daa1f 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -115,19 +115,21 @@ static int rseq_reset_rseq_cpu_id(struct task_struct *t)
 static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs)
 {
 	struct rseq_cs __user *urseq_cs;
-	unsigned long ptr;
+	u64 ptr;
 	u32 __user *usig;
 	u32 sig;
 	int ret;
 
-	ret = get_user(ptr, &t->rseq->rseq_cs);
+	ret = get_user(ptr, &t->rseq->rseq_cs.ptr64);
 	if (ret)
 		return ret;
 	if (!ptr) {
 		memset(rseq_cs, 0, sizeof(*rseq_cs));
 		return 0;
 	}
-	urseq_cs = (struct rseq_cs __user *)ptr;
+	if (ptr >= TASK_SIZE)
+		return -EINVAL;
+	urseq_cs = (struct rseq_cs __user *)(unsigned long)ptr;
 	if (copy_from_user(rseq_cs, urseq_cs, sizeof(*rseq_cs)))
 		return -EFAULT;
 
@@ -203,7 +205,7 @@ static int clear_rseq_cs(struct task_struct *t)
 	 *
 	 * Set rseq_cs to NULL.
 	 */
-	return put_user(0UL, &t->rseq->rseq_cs);
+	return put_user(0ULL, &t->rseq->rseq_cs.ptr64);
 }
 
 /*
diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index a4684112676c..f2073cfa4448 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -133,6 +133,15 @@ static inline uint32_t rseq_current_cpu(void)
 	return cpu;
 }
 
+static inline void rseq_clear_rseq_cs(void)
+{
+#ifdef __LP64__
+	__rseq_abi.rseq_cs.ptr = 0;
+#else
+	__rseq_abi.rseq_cs.ptr.ptr32 = 0;
+#endif
+}
+
 /*
  * rseq_prepare_unload() should be invoked by each thread using rseq_finish*()
  * at least once between their last rseq_finish*() and library unload of the
@@ -143,7 +152,7 @@ static inline uint32_t rseq_current_cpu(void)
  */
 static inline void rseq_prepare_unload(void)
 {
-	__rseq_abi.rseq_cs = 0;
+	rseq_clear_rseq_cs();
 }
 
 #endif  /* RSEQ_H_ */
-- 
2.11.0

[PATCH for 4.18 5/6] rseq: remove unused types_32_64.h uapi header

[Mathieu Desnoyers]

This header was introduced in the 4.18 merge window, and rseq does
not need it anymore. Nuke it before the final release.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Paul Turner <pjt@google.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Andi Kleen <andi@firstfloor.org>
CC: Dave Watson <davejwatson@fb.com>
CC: Chris Lameter <cl@linux.com>
CC: Ingo Molnar <mingo@redhat.com>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Ben Maurer <bmaurer@fb.com>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Russell King <linux@arm.linux.org.uk>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: linux-api@vger.kernel.org
---
 include/uapi/linux/types_32_64.h | 50 ----------------------------------------
 1 file changed, 50 deletions(-)
 delete mode 100644 include/uapi/linux/types_32_64.h

diff --git a/include/uapi/linux/types_32_64.h b/include/uapi/linux/types_32_64.h
deleted file mode 100644
index 0a87ace34a57..000000000000
--- a/include/uapi/linux/types_32_64.h
+++ /dev/null
@@ -1,50 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
-#ifndef _UAPI_LINUX_TYPES_32_64_H
-#define _UAPI_LINUX_TYPES_32_64_H
-
-/*
- * linux/types_32_64.h
- *
- * Integer type declaration for pointers across 32-bit and 64-bit systems.
- *
- * Copyright (c) 2015-2018 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- */
-
-#ifdef __KERNEL__
-# include <linux/types.h>
-#else
-# include <stdint.h>
-#endif
-
-#include <asm/byteorder.h>
-
-#ifdef __BYTE_ORDER
-# if (__BYTE_ORDER == __BIG_ENDIAN)
-#  define LINUX_BYTE_ORDER_BIG_ENDIAN
-# else
-#  define LINUX_BYTE_ORDER_LITTLE_ENDIAN
-# endif
-#else
-# ifdef __BIG_ENDIAN
-#  define LINUX_BYTE_ORDER_BIG_ENDIAN
-# else
-#  define LINUX_BYTE_ORDER_LITTLE_ENDIAN
-# endif
-#endif
-
-#ifdef __LP64__
-# define LINUX_FIELD_u32_u64(field)			__u64 field
-# define LINUX_FIELD_u32_u64_INIT_ONSTACK(field, v)	field = (intptr_t)v
-#else
-# ifdef LINUX_BYTE_ORDER_BIG_ENDIAN
-#  define LINUX_FIELD_u32_u64(field)	__u32 field ## _padding, field
-#  define LINUX_FIELD_u32_u64_INIT_ONSTACK(field, v)	\
-	field ## _padding = 0, field = (intptr_t)v
-# else
-#  define LINUX_FIELD_u32_u64(field)	__u32 field, field ## _padding
-#  define LINUX_FIELD_u32_u64_INIT_ONSTACK(field, v)	\
-	field = (intptr_t)v, field ## _padding = 0
-# endif
-#endif
-
-#endif /* _UAPI_LINUX_TYPES_32_64_H */
-- 
2.11.0

[PATCH for 4.18 6/6] rseq/selftests: cleanup: update comment above rseq_prepare_unload

[Mathieu Desnoyers]

rseq as it was merged does not have rseq_finish_*() in the user-space
selftests anymore. Update the rseq_prepare_unload() helper comment to
adapt to this reality.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Paul Turner <pjt@google.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Andi Kleen <andi@firstfloor.org>
CC: Dave Watson <davejwatson@fb.com>
CC: Chris Lameter <cl@linux.com>
CC: Ingo Molnar <mingo@redhat.com>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Ben Maurer <bmaurer@fb.com>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Russell King <linux@arm.linux.org.uk>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: linux-api@vger.kernel.org
---
 tools/testing/selftests/rseq/rseq.h | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index f2073cfa4448..86ce22417e0d 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -143,12 +143,13 @@ static inline void rseq_clear_rseq_cs(void)
 }
 
 /*
- * rseq_prepare_unload() should be invoked by each thread using rseq_finish*()
- * at least once between their last rseq_finish*() and library unload of the
- * library defining the rseq critical section (struct rseq_cs). This also
- * applies to use of rseq in code generated by JIT: rseq_prepare_unload()
- * should be invoked at least once by each thread using rseq_finish*() before
- * reclaim of the memory holding the struct rseq_cs.
+ * rseq_prepare_unload() should be invoked by each thread executing a rseq
+ * critical section at least once between their last critical section and
+ * library unload of the library defining the rseq critical section
+ * (struct rseq_cs). This also applies to use of rseq in code generated by
+ * JIT: rseq_prepare_unload() should be invoked at least once by each
+ * thread executing a rseq critical section before reclaim of the memory
+ * holding the struct rseq_cs.
  */
 static inline void rseq_prepare_unload(void)
 {
-- 
2.11.0

Re: [PATCH for 4.18 0/6] Restartable Sequences updates

[Linus Torvalds]

On Sun, Jul 8, 2018 at 2:03 PM Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
>
> Following the recent discussion thread [1] about rseq uapi, here is
> a set of updates submitted for integration into 4.18. Those change all
> rseq __get_user/__put_user for get_user/put_user as discussed.

LGTM, FWIW. I didn't test it, but the patches look sane.

         Linus

Re: [PATCH for 4.18 0/6] Restartable Sequences updates

[Mathieu Desnoyers]

----- On Jul 8, 2018, at 5:03 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:

> Following the recent discussion thread [1] about rseq uapi, here is
> a set of updates submitted for integration into 4.18. Those change all
> rseq __get_user/__put_user for get_user/put_user as discussed.

Considering that ppc32 does not implement 64-bit get_user(), I will re-spin
the whole series using __copy_from_user/__copy_to_user() to replace
__get_user()/__put_user() to load/store the 64-bit rseq_cs field.

I'm aiming for a minimal change at this stage of the rc cycle.

Thanks,

Mathieu

> 
> Thanks,
> 
> Mathieu
> 
> [1]
> https://lkml.kernel.org/r/20180702223143.4663-1-mathieu.desnoyers@efficios.com
> 
> Mathieu Desnoyers (6):
>  rseq: use __u64 for rseq_cs fields, validate user inputs
>  rseq: use get_user/put_user rather than __get_user/__put_user
>  rseq: uapi: update uapi comments
>  rseq: uapi: declare rseq_cs field as union, update includes
>  rseq: remove unused types_32_64.h uapi header
>  rseq/selftests: cleanup: update comment above rseq_prepare_unload
> 
> include/uapi/linux/rseq.h           | 102 ++++++++++++++++++++----------------
> include/uapi/linux/types_32_64.h    |  50 ------------------
> kernel/rseq.c                       |  36 ++++++++-----
> tools/testing/selftests/rseq/rseq.h |  24 ++++++---
> 4 files changed, 97 insertions(+), 115 deletions(-)
> delete mode 100644 include/uapi/linux/types_32_64.h
> 
> --
> 2.11.0

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

[PATCH v2 for 4.18 0/6] Restartable Sequences updates

[Mathieu Desnoyers]

Following the recent discussion thread [1] about rseq uapi, here is
a set of updates submitted for integration into 4.18. Those change all
rseq __get_user/__put_user for get_user/put_user as discussed, and
use copy_from_user()/clear_user() to load and clear the rseq_cs __u64.

Thanks,

Mathieu

[1] https://lkml.kernel.org/r/20180702223143.4663-1-mathieu.desnoyers@efficios.com

Mathieu Desnoyers (6):
  rseq: use __u64 for rseq_cs fields, validate user inputs
  rseq: use get_user/put_user rather than __get_user/__put_user
  rseq: uapi: update uapi comments
  rseq: uapi: declare rseq_cs field as union, update includes
  rseq: remove unused types_32_64.h uapi header
  rseq/selftests: cleanup: update comment above rseq_prepare_unload

 include/uapi/linux/rseq.h           | 102 ++++++++++++++++++++----------------
 include/uapi/linux/types_32_64.h    |  50 ------------------
 kernel/rseq.c                       |  41 +++++++++------
 tools/testing/selftests/rseq/rseq.h |  24 ++++++---
 4 files changed, 100 insertions(+), 117 deletions(-)
 delete mode 100644 include/uapi/linux/types_32_64.h

-- 
2.11.0

[PATCH for 4.18 6/6] rseq/selftests: cleanup: update comment above rseq_prepare_unload

[Mathieu Desnoyers]

rseq as it was merged does not have rseq_finish_*() in the user-space
selftests anymore. Update the rseq_prepare_unload() helper comment to
adapt to this reality.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Paul Turner <pjt@google.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Andi Kleen <andi@firstfloor.org>
CC: Dave Watson <davejwatson@fb.com>
CC: Chris Lameter <cl@linux.com>
CC: Ingo Molnar <mingo@redhat.com>
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Ben Maurer <bmaurer@fb.com>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Russell King <linux@arm.linux.org.uk>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
CC: Boqun Feng <boqun.feng@gmail.com>
CC: linux-api@vger.kernel.org
---
 tools/testing/selftests/rseq/rseq.h | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/rseq/rseq.h b/tools/testing/selftests/rseq/rseq.h
index f2073cfa4448..86ce22417e0d 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -143,12 +143,13 @@ static inline void rseq_clear_rseq_cs(void)
 }
 
 /*
- * rseq_prepare_unload() should be invoked by each thread using rseq_finish*()
- * at least once between their last rseq_finish*() and library unload of the
- * library defining the rseq critical section (struct rseq_cs). This also
- * applies to use of rseq in code generated by JIT: rseq_prepare_unload()
- * should be invoked at least once by each thread using rseq_finish*() before
- * reclaim of the memory holding the struct rseq_cs.
+ * rseq_prepare_unload() should be invoked by each thread executing a rseq
+ * critical section at least once between their last critical section and
+ * library unload of the library defining the rseq critical section
+ * (struct rseq_cs). This also applies to use of rseq in code generated by
+ * JIT: rseq_prepare_unload() should be invoked at least once by each
+ * thread executing a rseq critical section before reclaim of the memory
+ * holding the struct rseq_cs.
  */
 static inline void rseq_prepare_unload(void)
 {
-- 
2.11.0