From 83a4f1ef45a90d740bc6edf6a2533b14a3e5d183 Mon Sep 17 00:00:00 2001
From: Alexander Potapenko <glider@google.com>
Date: Thu, 15 Sep 2022 17:03:36 +0200
Subject: stackdepot: reserve 5 extra bits in depot_stack_handle_t

Some users (currently only KMSAN) may want to use spare bits in
depot_stack_handle_t.  Let them do so by adding @extra_bits to
__stack_depot_save() to store arbitrary flags, and providing
stack_depot_get_extra_bits() to retrieve those flags.

Also adapt KASAN to the new prototype by passing extra_bits=0, as KASAN
does not intend to store additional information in the stack handle.

Link: https://lkml.kernel.org/r/20220915150417.722975-3-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 include/linux/stackdepot.h | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'include/linux')

diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index bc2797955de9..9ca7798d7a31 100644
--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -14,9 +14,15 @@
 #include <linux/gfp.h>
 
 typedef u32 depot_stack_handle_t;
+/*
+ * Number of bits in the handle that stack depot doesn't use. Users may store
+ * information in them.
+ */
+#define STACK_DEPOT_EXTRA_BITS 5
 
 depot_stack_handle_t __stack_depot_save(unsigned long *entries,
 					unsigned int nr_entries,
+					unsigned int extra_bits,
 					gfp_t gfp_flags, bool can_alloc);
 
 /*
@@ -59,6 +65,8 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
 unsigned int stack_depot_fetch(depot_stack_handle_t handle,
 			       unsigned long **entries);
 
+unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle);
+
 int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
 		       int spaces);
 
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