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filter_irq_stacks() can be used by other tools (e.g. KMSAN), so it needs to be moved to a common location. lib/stackdepot.c seems a good place, as filter_irq_stacks() is usually applied to the output of stack_trace_save(). This patch has been previously mailed as part of KMSAN RFC patch series. [glider@google.co: nds32: linker script: add SOFTIRQENTRY_TEXT\ Link: http://lkml.kernel.org/r/20200311121002.241430-1-glider@google.com [glider@google.com: add IRQENTRY_TEXT and SOFTIRQENTRY_TEXT to linker script] Link: http://lkml.kernel.org/r/20200311121124.243352-1-glider@google.com Signed-off-by: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Vegard Nossum <vegard.nossum@oracle.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Marco Elver <elver@google.com> Cc: Andrey Konovalov <andreyknvl@google.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Link: http://lkml.kernel.org/r/20200220141916.55455-3-glider@google.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
343 lines
9.5 KiB
C
343 lines
9.5 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 contiguos 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/interrupt.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/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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#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 - STACK_ALLOC_OFFSET_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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};
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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[1]; /* Variable-sized array of entries. */
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};
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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_SPINLOCK(depot_lock);
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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 *depot_alloc_stack(unsigned long *entries, int size,
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u32 hash, void **prealloc, gfp_t alloc_flags)
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{
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int required_size = offsetof(struct stack_record, entries) +
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sizeof(unsigned long) * size;
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struct stack_record *stack;
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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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memcpy(stack->entries, entries, size * sizeof(unsigned long));
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depot_offset += required_size;
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return stack;
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}
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#define STACK_HASH_ORDER 20
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#define STACK_HASH_SIZE (1L << STACK_HASH_ORDER)
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#define STACK_HASH_MASK (STACK_HASH_SIZE - 1)
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#define STACK_HASH_SEED 0x9747b28c
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static struct stack_record *stack_table[STACK_HASH_SIZE] = {
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[0 ... STACK_HASH_SIZE - 1] = NULL
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};
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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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size * sizeof(unsigned long) / 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_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 (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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* @alloc_flags: Allocation gfp flags
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*
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* Return: The handle of the stack struct stored in depot
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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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gfp_t alloc_flags)
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{
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struct stack_record *found = NULL, **bucket;
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depot_stack_handle_t retval = 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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if (unlikely(nr_entries == 0))
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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
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* |bucket| below.
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*/
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found = find_stack(smp_load_acquire(bucket), entries,
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nr_entries, hash);
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if (found)
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goto exit;
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/*
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* Check if the current or the next stack slab need to be initialized.
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* If so, allocate the memory - we won't be able to do that under the
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* lock.
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*
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* The smp_load_acquire() here pairs with smp_store_release() to
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* |next_slab_inited| in depot_alloc_stack() and init_stack_slab().
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*/
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if (unlikely(!smp_load_acquire(&next_slab_inited))) {
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/*
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* Zero out zone modifiers, as we don't have specific zone
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* requirements. Keep the flags related to allocation in atomic
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* contexts and I/O.
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*/
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alloc_flags &= ~GFP_ZONEMASK;
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alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
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alloc_flags |= __GFP_NOWARN;
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page = alloc_pages(alloc_flags, STACK_ALLOC_ORDER);
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if (page)
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prealloc = page_address(page);
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}
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spin_lock_irqsave(&depot_lock, flags);
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found = find_stack(*bucket, entries, nr_entries, hash);
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if (!found) {
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struct stack_record *new =
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depot_alloc_stack(entries, nr_entries,
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hash, &prealloc, alloc_flags);
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if (new) {
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new->next = *bucket;
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/*
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* This smp_store_release() pairs with
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* smp_load_acquire() from |bucket| above.
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*/
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smp_store_release(bucket, new);
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found = new;
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}
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} else if (prealloc) {
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/*
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* We didn't need to store this stack trace, but let's keep
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* the preallocated memory for the future.
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*/
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WARN_ON(!init_stack_slab(&prealloc));
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}
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spin_unlock_irqrestore(&depot_lock, flags);
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exit:
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if (prealloc) {
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/* Nobody used this memory, ok to free it. */
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free_pages((unsigned long)prealloc, STACK_ALLOC_ORDER);
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}
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if (found)
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retval = found->handle.handle;
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fast_exit:
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return retval;
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}
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EXPORT_SYMBOL_GPL(stack_depot_save);
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static inline int in_irqentry_text(unsigned long ptr)
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{
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return (ptr >= (unsigned long)&__irqentry_text_start &&
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ptr < (unsigned long)&__irqentry_text_end) ||
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(ptr >= (unsigned long)&__softirqentry_text_start &&
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ptr < (unsigned long)&__softirqentry_text_end);
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}
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unsigned int filter_irq_stacks(unsigned long *entries,
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unsigned int nr_entries)
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{
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unsigned int i;
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for (i = 0; i < nr_entries; i++) {
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if (in_irqentry_text(entries[i])) {
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/* Include the irqentry function into the stack. */
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return i + 1;
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}
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}
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return nr_entries;
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}
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EXPORT_SYMBOL_GPL(filter_irq_stacks);
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