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![Imran Khan](/assets/img/avatar_default.png)
To print stack entries into a buffer, users of stackdepot, first get a list of stack entries using stack_depot_fetch and then print this list into a buffer using stack_trace_snprint. Provide a helper in stackdepot for this purpose. Also change above mentioned users to use this helper. [imran.f.khan@oracle.com: fix build error] Link: https://lkml.kernel.org/r/20210915175321.3472770-4-imran.f.khan@oracle.com [imran.f.khan@oracle.com: export stack_depot_snprint() to modules] Link: https://lkml.kernel.org/r/20210916133535.3592491-4-imran.f.khan@oracle.com Link: https://lkml.kernel.org/r/20210915014806.3206938-4-imran.f.khan@oracle.com Signed-off-by: Imran Khan <imran.f.khan@oracle.com> Suggested-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Jani Nikula <jani.nikula@intel.com> [i915] Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: David Airlie <airlied@linux.ie> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: Thomas Zimmermann <tzimmermann@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
418 lines
12 KiB
C
418 lines
12 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/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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#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[]; /* 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_RAW_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 *
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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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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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#define STACK_HASH_SIZE (1L << CONFIG_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 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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int __init stack_depot_init(void)
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{
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if (!stack_depot_disable) {
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size_t size = (STACK_HASH_SIZE * sizeof(struct stack_record *));
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int i;
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stack_table = memblock_alloc(size, size);
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for (i = 0; i < STACK_HASH_SIZE; i++)
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stack_table[i] = NULL;
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}
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return 0;
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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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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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* @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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* 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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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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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) || 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
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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(can_alloc && !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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raw_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 = depot_alloc_stack(entries, nr_entries, hash, &prealloc);
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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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raw_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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/**
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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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* Context: Contexts where allocations via alloc_pages() are allowed.
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* See __stack_depot_save() for more details.
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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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gfp_t alloc_flags)
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{
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return __stack_depot_save(entries, nr_entries, alloc_flags, true);
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}
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EXPORT_SYMBOL_GPL(stack_depot_save);
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