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![Alexander Potapenko](/assets/img/avatar_default.png)
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>
535 lines
15 KiB
C
535 lines
15 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Generic stack depot for storing stack traces.
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*
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* Some debugging tools need to save stack traces of certain events which can
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* be later presented to the user. For example, KASAN needs to safe alloc and
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* free stacks for each object, but storing two stack traces per object
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* requires too much memory (e.g. SLUB_DEBUG needs 256 bytes per object for
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* that).
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*
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* Instead, stack depot maintains a hashtable of unique stacktraces. Since alloc
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* and free stacks repeat a lot, we save about 100x space.
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* Stacks are never removed from depot, so we store them contiguously one after
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* another in a contiguous memory allocation.
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*
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* Author: Alexander Potapenko <glider@google.com>
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* Copyright (C) 2016 Google, Inc.
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*
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* Based on code by Dmitry Chernenkov.
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*/
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#include <linux/gfp.h>
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#include <linux/jhash.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/mutex.h>
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#include <linux/percpu.h>
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#include <linux/printk.h>
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#include <linux/slab.h>
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#include <linux/stacktrace.h>
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#include <linux/stackdepot.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/memblock.h>
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#include <linux/kasan-enabled.h>
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#define DEPOT_STACK_BITS (sizeof(depot_stack_handle_t) * 8)
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#define STACK_ALLOC_NULL_PROTECTION_BITS 1
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#define STACK_ALLOC_ORDER 2 /* 'Slab' size order for stack depot, 4 pages */
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#define STACK_ALLOC_SIZE (1LL << (PAGE_SHIFT + STACK_ALLOC_ORDER))
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#define STACK_ALLOC_ALIGN 4
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#define STACK_ALLOC_OFFSET_BITS (STACK_ALLOC_ORDER + PAGE_SHIFT - \
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STACK_ALLOC_ALIGN)
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#define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - \
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STACK_ALLOC_NULL_PROTECTION_BITS - \
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STACK_ALLOC_OFFSET_BITS - STACK_DEPOT_EXTRA_BITS)
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#define STACK_ALLOC_SLABS_CAP 8192
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#define STACK_ALLOC_MAX_SLABS \
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(((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \
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(1LL << (STACK_ALLOC_INDEX_BITS)) : STACK_ALLOC_SLABS_CAP)
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/* The compact structure to store the reference to stacks. */
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union handle_parts {
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depot_stack_handle_t handle;
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struct {
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u32 slabindex : STACK_ALLOC_INDEX_BITS;
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u32 offset : STACK_ALLOC_OFFSET_BITS;
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u32 valid : STACK_ALLOC_NULL_PROTECTION_BITS;
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u32 extra : STACK_DEPOT_EXTRA_BITS;
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};
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};
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struct stack_record {
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struct stack_record *next; /* Link in the hashtable */
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u32 hash; /* Hash in the hastable */
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u32 size; /* Number of frames in the stack */
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union handle_parts handle;
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unsigned long entries[]; /* Variable-sized array of entries. */
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};
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static bool __stack_depot_want_early_init __initdata = IS_ENABLED(CONFIG_STACKDEPOT_ALWAYS_INIT);
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static bool __stack_depot_early_init_passed __initdata;
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static void *stack_slabs[STACK_ALLOC_MAX_SLABS];
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static int depot_index;
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static int next_slab_inited;
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static size_t depot_offset;
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static DEFINE_RAW_SPINLOCK(depot_lock);
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unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle)
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{
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union handle_parts parts = { .handle = handle };
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return parts.extra;
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}
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EXPORT_SYMBOL(stack_depot_get_extra_bits);
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static bool init_stack_slab(void **prealloc)
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{
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if (!*prealloc)
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return false;
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/*
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* This smp_load_acquire() pairs with smp_store_release() to
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* |next_slab_inited| below and in depot_alloc_stack().
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*/
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if (smp_load_acquire(&next_slab_inited))
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return true;
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if (stack_slabs[depot_index] == NULL) {
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stack_slabs[depot_index] = *prealloc;
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*prealloc = NULL;
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} else {
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/* If this is the last depot slab, do not touch the next one. */
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if (depot_index + 1 < STACK_ALLOC_MAX_SLABS) {
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stack_slabs[depot_index + 1] = *prealloc;
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*prealloc = NULL;
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}
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/*
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* This smp_store_release pairs with smp_load_acquire() from
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* |next_slab_inited| above and in stack_depot_save().
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*/
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smp_store_release(&next_slab_inited, 1);
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}
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return true;
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}
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/* Allocation of a new stack in raw storage */
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static struct stack_record *
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depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
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{
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struct stack_record *stack;
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size_t required_size = struct_size(stack, entries, size);
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required_size = ALIGN(required_size, 1 << STACK_ALLOC_ALIGN);
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if (unlikely(depot_offset + required_size > STACK_ALLOC_SIZE)) {
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if (unlikely(depot_index + 1 >= STACK_ALLOC_MAX_SLABS)) {
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WARN_ONCE(1, "Stack depot reached limit capacity");
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return NULL;
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}
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depot_index++;
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depot_offset = 0;
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/*
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* smp_store_release() here pairs with smp_load_acquire() from
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* |next_slab_inited| in stack_depot_save() and
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* init_stack_slab().
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*/
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if (depot_index + 1 < STACK_ALLOC_MAX_SLABS)
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smp_store_release(&next_slab_inited, 0);
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}
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init_stack_slab(prealloc);
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if (stack_slabs[depot_index] == NULL)
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return NULL;
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stack = stack_slabs[depot_index] + depot_offset;
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stack->hash = hash;
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stack->size = size;
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stack->handle.slabindex = depot_index;
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stack->handle.offset = depot_offset >> STACK_ALLOC_ALIGN;
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stack->handle.valid = 1;
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stack->handle.extra = 0;
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memcpy(stack->entries, entries, flex_array_size(stack, entries, size));
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depot_offset += required_size;
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return stack;
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}
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/* one hash table bucket entry per 16kB of memory */
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#define STACK_HASH_SCALE 14
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/* limited between 4k and 1M buckets */
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#define STACK_HASH_ORDER_MIN 12
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#define STACK_HASH_ORDER_MAX 20
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#define STACK_HASH_SEED 0x9747b28c
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static unsigned int stack_hash_order;
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static unsigned int stack_hash_mask;
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static bool stack_depot_disable;
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static struct stack_record **stack_table;
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static int __init is_stack_depot_disabled(char *str)
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{
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int ret;
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ret = kstrtobool(str, &stack_depot_disable);
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if (!ret && stack_depot_disable) {
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pr_info("Stack Depot is disabled\n");
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stack_table = NULL;
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}
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return 0;
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}
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early_param("stack_depot_disable", is_stack_depot_disabled);
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void __init stack_depot_want_early_init(void)
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{
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/* Too late to request early init now */
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WARN_ON(__stack_depot_early_init_passed);
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__stack_depot_want_early_init = true;
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}
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int __init stack_depot_early_init(void)
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{
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unsigned long entries = 0;
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/* This is supposed to be called only once, from mm_init() */
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if (WARN_ON(__stack_depot_early_init_passed))
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return 0;
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__stack_depot_early_init_passed = true;
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if (kasan_enabled() && !stack_hash_order)
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stack_hash_order = STACK_HASH_ORDER_MAX;
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if (!__stack_depot_want_early_init || stack_depot_disable)
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return 0;
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if (stack_hash_order)
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entries = 1UL << stack_hash_order;
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stack_table = alloc_large_system_hash("stackdepot",
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sizeof(struct stack_record *),
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entries,
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STACK_HASH_SCALE,
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HASH_EARLY | HASH_ZERO,
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NULL,
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&stack_hash_mask,
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1UL << STACK_HASH_ORDER_MIN,
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1UL << STACK_HASH_ORDER_MAX);
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if (!stack_table) {
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pr_err("Stack Depot hash table allocation failed, disabling\n");
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stack_depot_disable = true;
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return -ENOMEM;
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}
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return 0;
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}
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int stack_depot_init(void)
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{
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static DEFINE_MUTEX(stack_depot_init_mutex);
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int ret = 0;
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mutex_lock(&stack_depot_init_mutex);
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if (!stack_depot_disable && !stack_table) {
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unsigned long entries;
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int scale = STACK_HASH_SCALE;
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if (stack_hash_order) {
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entries = 1UL << stack_hash_order;
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} else {
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entries = nr_free_buffer_pages();
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entries = roundup_pow_of_two(entries);
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if (scale > PAGE_SHIFT)
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entries >>= (scale - PAGE_SHIFT);
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else
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entries <<= (PAGE_SHIFT - scale);
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}
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if (entries < 1UL << STACK_HASH_ORDER_MIN)
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entries = 1UL << STACK_HASH_ORDER_MIN;
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if (entries > 1UL << STACK_HASH_ORDER_MAX)
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entries = 1UL << STACK_HASH_ORDER_MAX;
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pr_info("Stack Depot allocating hash table of %lu entries with kvcalloc\n",
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entries);
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stack_table = kvcalloc(entries, sizeof(struct stack_record *), GFP_KERNEL);
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if (!stack_table) {
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pr_err("Stack Depot hash table allocation failed, disabling\n");
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stack_depot_disable = true;
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ret = -ENOMEM;
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}
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stack_hash_mask = entries - 1;
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}
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mutex_unlock(&stack_depot_init_mutex);
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return ret;
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}
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EXPORT_SYMBOL_GPL(stack_depot_init);
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/* Calculate hash for a stack */
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static inline u32 hash_stack(unsigned long *entries, unsigned int size)
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{
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return jhash2((u32 *)entries,
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array_size(size, sizeof(*entries)) / sizeof(u32),
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STACK_HASH_SEED);
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}
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/* Use our own, non-instrumented version of memcmp().
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*
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* We actually don't care about the order, just the equality.
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*/
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static inline
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int stackdepot_memcmp(const unsigned long *u1, const unsigned long *u2,
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unsigned int n)
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{
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for ( ; n-- ; u1++, u2++) {
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if (*u1 != *u2)
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return 1;
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}
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return 0;
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}
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/* Find a stack that is equal to the one stored in entries in the hash */
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static inline struct stack_record *find_stack(struct stack_record *bucket,
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unsigned long *entries, int size,
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u32 hash)
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{
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struct stack_record *found;
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for (found = bucket; found; found = found->next) {
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if (found->hash == hash &&
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found->size == size &&
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!stackdepot_memcmp(entries, found->entries, size))
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return found;
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}
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return NULL;
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}
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/**
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* stack_depot_snprint - print stack entries from a depot into a buffer
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*
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* @handle: Stack depot handle which was returned from
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* stack_depot_save().
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* @buf: Pointer to the print buffer
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*
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* @size: Size of the print buffer
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*
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* @spaces: Number of leading spaces to print
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*
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* Return: Number of bytes printed.
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*/
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int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
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int spaces)
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{
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unsigned long *entries;
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unsigned int nr_entries;
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nr_entries = stack_depot_fetch(handle, &entries);
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return nr_entries ? stack_trace_snprint(buf, size, entries, nr_entries,
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spaces) : 0;
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}
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EXPORT_SYMBOL_GPL(stack_depot_snprint);
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/**
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* stack_depot_print - print stack entries from a depot
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*
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* @stack: Stack depot handle which was returned from
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* stack_depot_save().
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*
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*/
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void stack_depot_print(depot_stack_handle_t stack)
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{
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unsigned long *entries;
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unsigned int nr_entries;
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nr_entries = stack_depot_fetch(stack, &entries);
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if (nr_entries > 0)
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stack_trace_print(entries, nr_entries, 0);
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}
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EXPORT_SYMBOL_GPL(stack_depot_print);
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/**
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* stack_depot_fetch - Fetch stack entries from a depot
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*
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* @handle: Stack depot handle which was returned from
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* stack_depot_save().
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* @entries: Pointer to store the entries address
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*
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* Return: The number of trace entries for this depot.
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*/
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unsigned int stack_depot_fetch(depot_stack_handle_t handle,
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unsigned long **entries)
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{
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union handle_parts parts = { .handle = handle };
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void *slab;
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size_t offset = parts.offset << STACK_ALLOC_ALIGN;
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struct stack_record *stack;
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*entries = NULL;
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if (!handle)
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return 0;
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if (parts.slabindex > depot_index) {
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WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n",
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parts.slabindex, depot_index, handle);
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return 0;
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}
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slab = stack_slabs[parts.slabindex];
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if (!slab)
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return 0;
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stack = slab + offset;
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*entries = stack->entries;
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return stack->size;
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}
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EXPORT_SYMBOL_GPL(stack_depot_fetch);
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/**
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* __stack_depot_save - Save a stack trace from an array
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*
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* @entries: Pointer to storage array
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* @nr_entries: Size of the storage array
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* @extra_bits: Flags to store in unused bits of depot_stack_handle_t
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* @alloc_flags: Allocation gfp flags
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* @can_alloc: Allocate stack slabs (increased chance of failure if false)
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*
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* Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is
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* %true, is allowed to replenish the stack slab pool in case no space is left
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* (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids
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* any allocations and will fail if no space is left to store the stack trace.
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*
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* If the stack trace in @entries is from an interrupt, only the portion up to
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* interrupt entry is saved.
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*
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* Additional opaque flags can be passed in @extra_bits, stored in the unused
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* bits of the stack handle, and retrieved using stack_depot_get_extra_bits()
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* without calling stack_depot_fetch().
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*
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* Context: Any context, but setting @can_alloc to %false is required if
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* alloc_pages() cannot be used from the current context. Currently
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* this is the case from contexts where neither %GFP_ATOMIC nor
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* %GFP_NOWAIT can be used (NMI, raw_spin_lock).
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*
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* Return: The handle of the stack struct stored in depot, 0 on failure.
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*/
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depot_stack_handle_t __stack_depot_save(unsigned long *entries,
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unsigned int nr_entries,
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unsigned int extra_bits,
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gfp_t alloc_flags, bool can_alloc)
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{
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struct stack_record *found = NULL, **bucket;
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union handle_parts retval = { .handle = 0 };
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struct page *page = NULL;
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void *prealloc = NULL;
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unsigned long flags;
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u32 hash;
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/*
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* If this stack trace is from an interrupt, including anything before
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* interrupt entry usually leads to unbounded stackdepot growth.
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*
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* Because use of filter_irq_stacks() is a requirement to ensure
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* stackdepot can efficiently deduplicate interrupt stacks, always
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* filter_irq_stacks() to simplify all callers' use of stackdepot.
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*/
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nr_entries = filter_irq_stacks(entries, nr_entries);
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if (unlikely(nr_entries == 0) || stack_depot_disable)
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goto fast_exit;
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hash = hash_stack(entries, nr_entries);
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bucket = &stack_table[hash & stack_hash_mask];
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/*
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* Fast path: look the stack trace up without locking.
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* The smp_load_acquire() here pairs with smp_store_release() to
|
|
* |bucket| below.
|
|
*/
|
|
found = find_stack(smp_load_acquire(bucket), entries,
|
|
nr_entries, hash);
|
|
if (found)
|
|
goto exit;
|
|
|
|
/*
|
|
* Check if the current or the next stack slab need to be initialized.
|
|
* If so, allocate the memory - we won't be able to do that under the
|
|
* lock.
|
|
*
|
|
* The smp_load_acquire() here pairs with smp_store_release() to
|
|
* |next_slab_inited| in depot_alloc_stack() and init_stack_slab().
|
|
*/
|
|
if (unlikely(can_alloc && !smp_load_acquire(&next_slab_inited))) {
|
|
/*
|
|
* Zero out zone modifiers, as we don't have specific zone
|
|
* requirements. Keep the flags related to allocation in atomic
|
|
* contexts and I/O.
|
|
*/
|
|
alloc_flags &= ~GFP_ZONEMASK;
|
|
alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
|
|
alloc_flags |= __GFP_NOWARN;
|
|
page = alloc_pages(alloc_flags, STACK_ALLOC_ORDER);
|
|
if (page)
|
|
prealloc = page_address(page);
|
|
}
|
|
|
|
raw_spin_lock_irqsave(&depot_lock, flags);
|
|
|
|
found = find_stack(*bucket, entries, nr_entries, hash);
|
|
if (!found) {
|
|
struct stack_record *new = depot_alloc_stack(entries, nr_entries, hash, &prealloc);
|
|
|
|
if (new) {
|
|
new->next = *bucket;
|
|
/*
|
|
* This smp_store_release() pairs with
|
|
* smp_load_acquire() from |bucket| above.
|
|
*/
|
|
smp_store_release(bucket, new);
|
|
found = new;
|
|
}
|
|
} else if (prealloc) {
|
|
/*
|
|
* We didn't need to store this stack trace, but let's keep
|
|
* the preallocated memory for the future.
|
|
*/
|
|
WARN_ON(!init_stack_slab(&prealloc));
|
|
}
|
|
|
|
raw_spin_unlock_irqrestore(&depot_lock, flags);
|
|
exit:
|
|
if (prealloc) {
|
|
/* Nobody used this memory, ok to free it. */
|
|
free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER);
|
|
}
|
|
if (found)
|
|
retval.handle = found->handle.handle;
|
|
fast_exit:
|
|
retval.extra = extra_bits;
|
|
|
|
return retval.handle;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__stack_depot_save);
|
|
|
|
/**
|
|
* stack_depot_save - Save a stack trace from an array
|
|
*
|
|
* @entries: Pointer to storage array
|
|
* @nr_entries: Size of the storage array
|
|
* @alloc_flags: Allocation gfp flags
|
|
*
|
|
* Context: Contexts where allocations via alloc_pages() are allowed.
|
|
* See __stack_depot_save() for more details.
|
|
*
|
|
* Return: The handle of the stack struct stored in depot, 0 on failure.
|
|
*/
|
|
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, 0, alloc_flags, true);
|
|
}
|
|
EXPORT_SYMBOL_GPL(stack_depot_save);
|