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Commit b3f20785 authored by Pawel Moll's avatar Pawel Moll Committed by Ingo Molnar
Browse files

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: default avatarDrew Richardson <drew.richardson@arm.com>
Signed-off-by: default avatarPawel Moll <pawel.moll@arm.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1402671812-9078-1-git-send-email-pawel.moll@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent f96f5678

kernel/events/core.c

+22 −1
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ 
#include <linux/cgroup.h>

#include <linux/module.h>

#include <linux/mman.h>

#include <linux/compat.h>



#include "internal.h"
@@ -3717,6 +3718,26 @@ 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;
@@ -4222,7 +4243,7 @@ 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,

};