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.richard...@arm.com>
Signed-off-by: Pawel Moll <pawel.m...@arm.com>
---
kernel/events/core.c | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 24d35cc..967af2c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3700,6 +3700,26 @@ 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;
@@ -4205,7 +4225,7 @@ 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,
};
--
1.9.1
--
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