[v2] perf: Handle compat ioctl

Message ID 1403009029-30967-1-git-send-email-pawel.moll@arm.com
State New
Headers show

Commit Message

Pawel Moll June 17, 2014, 12:43 p.m.
When running a 32-bit userspace on a 64-bit kernel (eg. i386
application on x86_64 kernel or 32-bit arm userspace on arm64
kernel) some of the perf ioctls must be treated with special
care, as they have a pointer size encoded in the command.

For example, PERF_EVENT_IOC_ID in 32-bit world will be encoded
as 0x80042407, but 64-bit kernel will expect 0x80082407. In
result the ioctl will fail returning -ENOTTY.

This patch solves the problem by adding code fixing up the
size as compat_ioctl file operation.

Reported-by: Drew Richardson <drew.richardson@arm.com>
Signed-off-by: Pawel Moll <pawel.moll@arm.com>
---
 kernel/events/core.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

Changes from v1:
- added missing #include

Comments

Pawel Moll July 1, 2014, 4:06 p.m. | #1
On Tue, 2014-06-17 at 13:43 +0100, Pawel Moll wrote:
> When running a 32-bit userspace on a 64-bit kernel (eg. i386
> application on x86_64 kernel or 32-bit arm userspace on arm64
> kernel) some of the perf ioctls must be treated with special
> care, as they have a pointer size encoded in the command.
> 
> For example, PERF_EVENT_IOC_ID in 32-bit world will be encoded
> as 0x80042407, but 64-bit kernel will expect 0x80082407. In
> result the ioctl will fail returning -ENOTTY.
> 
> This patch solves the problem by adding code fixing up the
> size as compat_ioctl file operation.
> 
> Reported-by: Drew Richardson <drew.richardson@arm.com>
> Signed-off-by: Pawel Moll <pawel.moll@arm.com>

This just is a polite and friendly nag...

Any, strong or not, opinions on the matter?

Cheers!

Pawel

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Peter Zijlstra July 7, 2014, 12:43 p.m. | #2
On Tue, Jul 01, 2014 at 05:06:00PM +0100, Pawel Moll wrote:
> On Tue, 2014-06-17 at 13:43 +0100, Pawel Moll wrote:
> > When running a 32-bit userspace on a 64-bit kernel (eg. i386
> > application on x86_64 kernel or 32-bit arm userspace on arm64
> > kernel) some of the perf ioctls must be treated with special
> > care, as they have a pointer size encoded in the command.
> > 
> > For example, PERF_EVENT_IOC_ID in 32-bit world will be encoded
> > as 0x80042407, but 64-bit kernel will expect 0x80082407. In
> > result the ioctl will fail returning -ENOTTY.
> > 
> > This patch solves the problem by adding code fixing up the
> > size as compat_ioctl file operation.
> > 
> > Reported-by: Drew Richardson <drew.richardson@arm.com>
> > Signed-off-by: Pawel Moll <pawel.moll@arm.com>
> 
> This just is a polite and friendly nag...
> 
> Any, strong or not, opinions on the matter?

Sorry, travel, cracks, falling, etc..

Queued it, we'll see what happens with this one ;-)
Pawel Moll Aug. 14, 2014, 10:17 a.m. | #3
On Mon, 2014-07-07 at 13:43 +0100, Peter Zijlstra wrote:
> On Tue, Jul 01, 2014 at 05:06:00PM +0100, Pawel Moll wrote:
> > On Tue, 2014-06-17 at 13:43 +0100, Pawel Moll wrote:
> > > When running a 32-bit userspace on a 64-bit kernel (eg. i386
> > > application on x86_64 kernel or 32-bit arm userspace on arm64
> > > kernel) some of the perf ioctls must be treated with special
> > > care, as they have a pointer size encoded in the command.
> > > 
> > > For example, PERF_EVENT_IOC_ID in 32-bit world will be encoded
> > > as 0x80042407, but 64-bit kernel will expect 0x80082407. In
> > > result the ioctl will fail returning -ENOTTY.
> > > 
> > > This patch solves the problem by adding code fixing up the
> > > size as compat_ioctl file operation.
> > > 
> > > Reported-by: Drew Richardson <drew.richardson@arm.com>
> > > Signed-off-by: Pawel Moll <pawel.moll@arm.com>
> > 
> > This just is a polite and friendly nag...
> > 
> > Any, strong or not, opinions on the matter?
> 
> Sorry, travel, cracks, falling, etc..
> 
> Queued it, we'll see what happens with this one ;-)

Has it managed to hold on to the ground between the cracks then? ;-)

(asking because can't see it in your perf/core branch on git.kernel.org)

Pawel

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Peter Zijlstra Aug. 14, 2014, 10:51 a.m. | #4
On Thu, Aug 14, 2014 at 11:17:48AM +0100, Pawel Moll wrote:
> Has it managed to hold on to the ground between the cracks then? ;-)
> 
> (asking because can't see it in your perf/core branch on git.kernel.org)

Damn this patch is cursed; I've no idea where it went. Lemme stick it in
perf/urgent, this is ridiculous.

Patch

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5fa58e4..f081335 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -40,6 +40,7 @@ 
 #include <linux/mm_types.h>
 #include <linux/cgroup.h>
 #include <linux/module.h>
+#include <linux/compat.h>
 
 #include "internal.h"
 
@@ -3716,6 +3717,26 @@  static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	return 0;
 }
 
+#ifdef CONFIG_COMPAT
+static long perf_compat_ioctl(struct file *file, unsigned int cmd,
+				unsigned long arg)
+{
+	switch (_IOC_NR(cmd)) {
+	case _IOC_NR(PERF_EVENT_IOC_SET_FILTER):
+	case _IOC_NR(PERF_EVENT_IOC_ID):
+		/* Fix up pointer size (usually 4 -> 8 in 32-on-64-bit case */
+		if (_IOC_SIZE(cmd) == sizeof(compat_uptr_t)) {
+			cmd &= ~IOCSIZE_MASK;
+			cmd |= sizeof(void *) << IOCSIZE_SHIFT;
+		}
+		break;
+	}
+	return perf_ioctl(file, cmd, arg);
+}
+#else
+#define perf_compat_ioctl NULL
+#endif
+
 int perf_event_task_enable(void)
 {
 	struct perf_event *event;
@@ -4221,7 +4242,7 @@  static const struct file_operations perf_fops = {
 	.read			= perf_read,
 	.poll			= perf_poll,
 	.unlocked_ioctl		= perf_ioctl,
-	.compat_ioctl		= perf_ioctl,
+	.compat_ioctl		= perf_compat_ioctl,
 	.mmap			= perf_mmap,
 	.fasync			= perf_fasync,
 };