Commit-ID: cdbaf0a372db2bc3c3127e8b63fd15bd6e6757ee
Gitweb: https://git.kernel.org/tip/cdbaf0a372db2bc3c3127e8b63fd15bd6e6757ee
Author: Joerg Roedel <[email protected]>
AuthorDate: Fri, 20 Jul 2018 18:22:22 +0200
Committer: Thomas Gleixner <[email protected]>
CommitDate: Fri, 20 Jul 2018 21:32:08 +0200
perf/core: Make sure the ring-buffer is mapped in all page-tables
The ring-buffer is accessed in the NMI handler, so it's better to avoid
faulting on it. Sync the vmalloc range with all page-tables in system to
make sure everyone has it mapped.
This fixes a WARN_ON_ONCE() that can be triggered with PTI enabled on
x86-32:
WARNING: CPU: 4 PID: 0 at arch/x86/mm/fault.c:320 vmalloc_fault+0x220/0x230
This triggers because with PTI enabled on an PAE kernel the PMDs are no
longer shared between the page-tables, so the vmalloc changes do not
propagate automatically.
Note: Andy said rightfully that we should try to fix the vmalloc code for
that case, but that's not a hot fix for the issue at hand.
Fixes: 7757d607c6b3 ("x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32")
Signed-off-by: Joerg Roedel <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: "H . Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: Linus Torvalds <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Juergen Gross <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Jiri Kosina <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: David Laight <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: Greg KH <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Andrea Arcangeli <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: "David H . Gutteridge" <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: [email protected]
Link:
https://lkml.kernel.org/r/[email protected]
---
kernel/events/ring_buffer.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 5d3cf407e374..7b0e9aafafdf 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -814,6 +814,9 @@ static void rb_free_work(struct work_struct *work)
vfree(base);
kfree(rb);
+
+ /* Make sure buffer is unmapped in all page-tables */
+ vmalloc_sync_all();
}
void rb_free(struct ring_buffer *rb)
@@ -840,6 +843,13 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark,
int cpu, int flags)
if (!all_buf)
goto fail_all_buf;
+ /*
+ * The buffer is accessed in NMI handlers, make sure it is
+ * mapped in all page-tables in the system so that we don't
+ * fault on the range in an NMI handler.
+ */
+ vmalloc_sync_all();
+
rb->user_page = all_buf;
rb->data_pages[0] = all_buf + PAGE_SIZE;
if (nr_pages) {
