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Message-ID: <20220905122452.2258262-3-glider@google.com>
Date: Mon, 5 Sep 2022 14:24:10 +0200
From: Alexander Potapenko <glider@...gle.com>
To: glider@...gle.com
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
Alexei Starovoitov <ast@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Andrey Konovalov <andreyknvl@...gle.com>,
Andy Lutomirski <luto@...nel.org>,
Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
Christoph Hellwig <hch@....de>,
Christoph Lameter <cl@...ux.com>,
David Rientjes <rientjes@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Eric Dumazet <edumazet@...gle.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Herbert Xu <herbert@...dor.apana.org.au>,
Ilya Leoshkevich <iii@...ux.ibm.com>,
Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Kees Cook <keescook@...omium.org>,
Marco Elver <elver@...gle.com>,
Mark Rutland <mark.rutland@....com>,
Matthew Wilcox <willy@...radead.org>,
"Michael S. Tsirkin" <mst@...hat.com>,
Pekka Enberg <penberg@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Petr Mladek <pmladek@...e.com>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
Vasily Gorbik <gor@...ux.ibm.com>,
Vegard Nossum <vegard.nossum@...cle.com>,
Vlastimil Babka <vbabka@...e.cz>, kasan-dev@...glegroups.com,
linux-mm@...ck.org, linux-arch@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v6 02/44] 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.
Signed-off-by: Alexander Potapenko <glider@...gle.com>
Reviewed-by: Marco Elver <elver@...gle.com>
---
v4:
-- per Marco Elver's request, fold "kasan: common: adapt to the new
prototype of __stack_depot_save()" into this patch to prevent
bisection breakages.
Link: https://linux-review.googlesource.com/id/I0587f6c777667864768daf07821d594bce6d8ff9
---
include/linux/stackdepot.h | 8 ++++++++
lib/stackdepot.c | 29 ++++++++++++++++++++++++-----
mm/kasan/common.c | 2 +-
3 files changed, 33 insertions(+), 6 deletions(-)
diff --git a/include/linux/stackdepot.h b/include/linux/stackdepot.h
index bc2797955de90..9ca7798d7a318 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);
diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index e73fda23388d8..79e894cf84064 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -43,7 +43,8 @@
#define STACK_ALLOC_OFFSET_BITS (STACK_ALLOC_ORDER + PAGE_SHIFT - \
STACK_ALLOC_ALIGN)
#define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - \
- STACK_ALLOC_NULL_PROTECTION_BITS - STACK_ALLOC_OFFSET_BITS)
+ STACK_ALLOC_NULL_PROTECTION_BITS - \
+ STACK_ALLOC_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS)
#define STACK_ALLOC_SLABS_CAP 8192
#define STACK_ALLOC_MAX_SLABS \
(((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \
@@ -56,6 +57,7 @@ union handle_parts {
u32 slabindex : STACK_ALLOC_INDEX_BITS;
u32 offset : STACK_ALLOC_OFFSET_BITS;
u32 valid : STACK_ALLOC_NULL_PROTECTION_BITS;
+ u32 extra : STACK_DEPOT_EXTRA_BITS;
};
};
@@ -77,6 +79,14 @@ static int next_slab_inited;
static size_t depot_offset;
static DEFINE_RAW_SPINLOCK(depot_lock);
+unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle)
+{
+ union handle_parts parts = { .handle = handle };
+
+ return parts.extra;
+}
+EXPORT_SYMBOL(stack_depot_get_extra_bits);
+
static bool init_stack_slab(void **prealloc)
{
if (!*prealloc)
@@ -140,6 +150,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
stack->handle.slabindex = depot_index;
stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN;
stack->handle.valid = 1;
+ stack->handle.extra = 0;
memcpy(stack->entries, entries, flex_array_size(stack, entries, size));
depot_offset += required_size;
@@ -382,6 +393,7 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch);
*
* @entries: Pointer to storage array
* @nr_entries: Size of the storage array
+ * @extra_bits: Flags to store in unused bits of depot_stack_handle_t
* @alloc_flags: Allocation gfp flags
* @can_alloc: Allocate stack slabs (increased chance of failure if false)
*
@@ -393,6 +405,10 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch);
* If the stack trace in @entries is from an interrupt, only the portion up to
* interrupt entry is saved.
*
+ * Additional opaque flags can be passed in @extra_bits, stored in the unused
+ * bits of the stack handle, and retrieved using stack_depot_get_extra_bits()
+ * without calling stack_depot_fetch().
+ *
* Context: Any context, but setting @can_alloc to %false is required if
* alloc_pages() cannot be used from the current context. Currently
* this is the case from contexts where neither %GFP_ATOMIC nor
@@ -402,10 +418,11 @@ EXPORT_SYMBOL_GPL(stack_depot_fetch);
*/
depot_stack_handle_t __stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
+ unsigned int extra_bits,
gfp_t alloc_flags, bool can_alloc)
{
struct stack_record *found = NULL, **bucket;
- depot_stack_handle_t retval = 0;
+ union handle_parts retval = { .handle = 0 };
struct page *page = NULL;
void *prealloc = NULL;
unsigned long flags;
@@ -489,9 +506,11 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER);
}
if (found)
- retval = found->handle.handle;
+ retval.handle = found->handle.handle;
fast_exit:
- return retval;
+ retval.extra = extra_bits;
+
+ return retval.handle;
}
EXPORT_SYMBOL_GPL(__stack_depot_save);
@@ -511,6 +530,6 @@ depot_stack_handle_t stack_depot_save(unsigned long *entries,
unsigned int nr_entries,
gfp_t alloc_flags)
{
- return __stack_depot_save(entries, nr_entries, alloc_flags, true);
+ return __stack_depot_save(entries, nr_entries, 0, alloc_flags, true);
}
EXPORT_SYMBOL_GPL(stack_depot_save);
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 69f583855c8be..94caa2d46a327 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -36,7 +36,7 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc)
unsigned int nr_entries;
nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
- return __stack_depot_save(entries, nr_entries, flags, can_alloc);
+ return __stack_depot_save(entries, nr_entries, 0, flags, can_alloc);
}
void kasan_set_track(struct kasan_track *track, gfp_t flags)
--
2.37.2.789.g6183377224-goog
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