[PATCH v3.4] perf: Handle compat ioctl

[David Ahern]

Fixup of the following for v3.4 stable train. PERF_EVENT_IOC_ID
is not valid for v3.4 but PERF_EVENT_IOC_SET_FILTER is.

Cc: <***@vger.kernel.org> # 3.4.x
Cc: Ingo Molnar <***@kernel.org>
Cc: Peter Zijlstra <***@infradead.org>
Cc: Arnaldo Carvalho de Melo <***@kernel.org>

commit b3f207855f57b9c8f43a547a801340bb5cbc59e5
Author: Pawel Moll <***@arm.com>
Date: Fri Jun 13 16:03:32 2014 +0100

perf: Handle compat ioctl

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 <***@arm.com>
Signed-off-by: Pawel Moll <***@arm.com>
Signed-off-by: Peter Zijlstra <***@infradead.org>
Cc: Arnaldo Carvalho de Melo <***@kernel.org>
Cc: Jiri Olsa <***@redhat.com>
Link: http://lkml.kernel.org/r/1402671812-9078-1-git-send-email-***@arm.com
Signed-off-by: Ingo Molnar <***@kernel.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index b058731fc000..1ef6d2a33ec0 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -36,6 +36,7 @@
#include <linux/perf_event.h>
#include <linux/ftrace_event.h>
#include <linux/hw_breakpoint.h>
+#include <linux/compat.h>

#include "internal.h"

@@ -3310,6 +3311,25 @@ 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):
+ /* 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;
@@ -3702,7 +3722,7 @@ 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,
};