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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>
This commit is contained in:
Alexander Potapenko 2022-09-15 17:03:36 +02:00 committed by Andrew Morton
parent e41e614f6a
commit 83a4f1ef45
3 changed files with 33 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/stackdepot.h
View File

@ -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);

29
lib/stackdepot.c
View File

@ -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);

2
mm/kasan/common.c
View File

@ -43,7 +43,7 @@ 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)