cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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ringbuf.c (14863B)


      1#include <linux/bpf.h>
      2#include <linux/btf.h>
      3#include <linux/err.h>
      4#include <linux/irq_work.h>
      5#include <linux/slab.h>
      6#include <linux/filter.h>
      7#include <linux/mm.h>
      8#include <linux/vmalloc.h>
      9#include <linux/wait.h>
     10#include <linux/poll.h>
     11#include <linux/kmemleak.h>
     12#include <uapi/linux/btf.h>
     13#include <linux/btf_ids.h>
     14
     15#define RINGBUF_CREATE_FLAG_MASK (BPF_F_NUMA_NODE)
     16
     17/* non-mmap()'able part of bpf_ringbuf (everything up to consumer page) */
     18#define RINGBUF_PGOFF \
     19	(offsetof(struct bpf_ringbuf, consumer_pos) >> PAGE_SHIFT)
     20/* consumer page and producer page */
     21#define RINGBUF_POS_PAGES 2
     22
     23#define RINGBUF_MAX_RECORD_SZ (UINT_MAX/4)
     24
     25/* Maximum size of ring buffer area is limited by 32-bit page offset within
     26 * record header, counted in pages. Reserve 8 bits for extensibility, and take
     27 * into account few extra pages for consumer/producer pages and
     28 * non-mmap()'able parts. This gives 64GB limit, which seems plenty for single
     29 * ring buffer.
     30 */
     31#define RINGBUF_MAX_DATA_SZ \
     32	(((1ULL << 24) - RINGBUF_POS_PAGES - RINGBUF_PGOFF) * PAGE_SIZE)
     33
     34struct bpf_ringbuf {
     35	wait_queue_head_t waitq;
     36	struct irq_work work;
     37	u64 mask;
     38	struct page **pages;
     39	int nr_pages;
     40	spinlock_t spinlock ____cacheline_aligned_in_smp;
     41	/* Consumer and producer counters are put into separate pages to allow
     42	 * mapping consumer page as r/w, but restrict producer page to r/o.
     43	 * This protects producer position from being modified by user-space
     44	 * application and ruining in-kernel position tracking.
     45	 */
     46	unsigned long consumer_pos __aligned(PAGE_SIZE);
     47	unsigned long producer_pos __aligned(PAGE_SIZE);
     48	char data[] __aligned(PAGE_SIZE);
     49};
     50
     51struct bpf_ringbuf_map {
     52	struct bpf_map map;
     53	struct bpf_ringbuf *rb;
     54};
     55
     56/* 8-byte ring buffer record header structure */
     57struct bpf_ringbuf_hdr {
     58	u32 len;
     59	u32 pg_off;
     60};
     61
     62static struct bpf_ringbuf *bpf_ringbuf_area_alloc(size_t data_sz, int numa_node)
     63{
     64	const gfp_t flags = GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL |
     65			    __GFP_NOWARN | __GFP_ZERO;
     66	int nr_meta_pages = RINGBUF_PGOFF + RINGBUF_POS_PAGES;
     67	int nr_data_pages = data_sz >> PAGE_SHIFT;
     68	int nr_pages = nr_meta_pages + nr_data_pages;
     69	struct page **pages, *page;
     70	struct bpf_ringbuf *rb;
     71	size_t array_size;
     72	int i;
     73
     74	/* Each data page is mapped twice to allow "virtual"
     75	 * continuous read of samples wrapping around the end of ring
     76	 * buffer area:
     77	 * ------------------------------------------------------
     78	 * | meta pages |  real data pages  |  same data pages  |
     79	 * ------------------------------------------------------
     80	 * |            | 1 2 3 4 5 6 7 8 9 | 1 2 3 4 5 6 7 8 9 |
     81	 * ------------------------------------------------------
     82	 * |            | TA             DA | TA             DA |
     83	 * ------------------------------------------------------
     84	 *                               ^^^^^^^
     85	 *                                  |
     86	 * Here, no need to worry about special handling of wrapped-around
     87	 * data due to double-mapped data pages. This works both in kernel and
     88	 * when mmap()'ed in user-space, simplifying both kernel and
     89	 * user-space implementations significantly.
     90	 */
     91	array_size = (nr_meta_pages + 2 * nr_data_pages) * sizeof(*pages);
     92	pages = bpf_map_area_alloc(array_size, numa_node);
     93	if (!pages)
     94		return NULL;
     95
     96	for (i = 0; i < nr_pages; i++) {
     97		page = alloc_pages_node(numa_node, flags, 0);
     98		if (!page) {
     99			nr_pages = i;
    100			goto err_free_pages;
    101		}
    102		pages[i] = page;
    103		if (i >= nr_meta_pages)
    104			pages[nr_data_pages + i] = page;
    105	}
    106
    107	rb = vmap(pages, nr_meta_pages + 2 * nr_data_pages,
    108		  VM_MAP | VM_USERMAP, PAGE_KERNEL);
    109	if (rb) {
    110		kmemleak_not_leak(pages);
    111		rb->pages = pages;
    112		rb->nr_pages = nr_pages;
    113		return rb;
    114	}
    115
    116err_free_pages:
    117	for (i = 0; i < nr_pages; i++)
    118		__free_page(pages[i]);
    119	kvfree(pages);
    120	return NULL;
    121}
    122
    123static void bpf_ringbuf_notify(struct irq_work *work)
    124{
    125	struct bpf_ringbuf *rb = container_of(work, struct bpf_ringbuf, work);
    126
    127	wake_up_all(&rb->waitq);
    128}
    129
    130static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
    131{
    132	struct bpf_ringbuf *rb;
    133
    134	rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
    135	if (!rb)
    136		return NULL;
    137
    138	spin_lock_init(&rb->spinlock);
    139	init_waitqueue_head(&rb->waitq);
    140	init_irq_work(&rb->work, bpf_ringbuf_notify);
    141
    142	rb->mask = data_sz - 1;
    143	rb->consumer_pos = 0;
    144	rb->producer_pos = 0;
    145
    146	return rb;
    147}
    148
    149static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
    150{
    151	struct bpf_ringbuf_map *rb_map;
    152
    153	if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
    154		return ERR_PTR(-EINVAL);
    155
    156	if (attr->key_size || attr->value_size ||
    157	    !is_power_of_2(attr->max_entries) ||
    158	    !PAGE_ALIGNED(attr->max_entries))
    159		return ERR_PTR(-EINVAL);
    160
    161#ifdef CONFIG_64BIT
    162	/* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */
    163	if (attr->max_entries > RINGBUF_MAX_DATA_SZ)
    164		return ERR_PTR(-E2BIG);
    165#endif
    166
    167	rb_map = kzalloc(sizeof(*rb_map), GFP_USER | __GFP_ACCOUNT);
    168	if (!rb_map)
    169		return ERR_PTR(-ENOMEM);
    170
    171	bpf_map_init_from_attr(&rb_map->map, attr);
    172
    173	rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node);
    174	if (!rb_map->rb) {
    175		kfree(rb_map);
    176		return ERR_PTR(-ENOMEM);
    177	}
    178
    179	return &rb_map->map;
    180}
    181
    182static void bpf_ringbuf_free(struct bpf_ringbuf *rb)
    183{
    184	/* copy pages pointer and nr_pages to local variable, as we are going
    185	 * to unmap rb itself with vunmap() below
    186	 */
    187	struct page **pages = rb->pages;
    188	int i, nr_pages = rb->nr_pages;
    189
    190	vunmap(rb);
    191	for (i = 0; i < nr_pages; i++)
    192		__free_page(pages[i]);
    193	kvfree(pages);
    194}
    195
    196static void ringbuf_map_free(struct bpf_map *map)
    197{
    198	struct bpf_ringbuf_map *rb_map;
    199
    200	rb_map = container_of(map, struct bpf_ringbuf_map, map);
    201	bpf_ringbuf_free(rb_map->rb);
    202	kfree(rb_map);
    203}
    204
    205static void *ringbuf_map_lookup_elem(struct bpf_map *map, void *key)
    206{
    207	return ERR_PTR(-ENOTSUPP);
    208}
    209
    210static int ringbuf_map_update_elem(struct bpf_map *map, void *key, void *value,
    211				   u64 flags)
    212{
    213	return -ENOTSUPP;
    214}
    215
    216static int ringbuf_map_delete_elem(struct bpf_map *map, void *key)
    217{
    218	return -ENOTSUPP;
    219}
    220
    221static int ringbuf_map_get_next_key(struct bpf_map *map, void *key,
    222				    void *next_key)
    223{
    224	return -ENOTSUPP;
    225}
    226
    227static int ringbuf_map_mmap(struct bpf_map *map, struct vm_area_struct *vma)
    228{
    229	struct bpf_ringbuf_map *rb_map;
    230
    231	rb_map = container_of(map, struct bpf_ringbuf_map, map);
    232
    233	if (vma->vm_flags & VM_WRITE) {
    234		/* allow writable mapping for the consumer_pos only */
    235		if (vma->vm_pgoff != 0 || vma->vm_end - vma->vm_start != PAGE_SIZE)
    236			return -EPERM;
    237	} else {
    238		vma->vm_flags &= ~VM_MAYWRITE;
    239	}
    240	/* remap_vmalloc_range() checks size and offset constraints */
    241	return remap_vmalloc_range(vma, rb_map->rb,
    242				   vma->vm_pgoff + RINGBUF_PGOFF);
    243}
    244
    245static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb)
    246{
    247	unsigned long cons_pos, prod_pos;
    248
    249	cons_pos = smp_load_acquire(&rb->consumer_pos);
    250	prod_pos = smp_load_acquire(&rb->producer_pos);
    251	return prod_pos - cons_pos;
    252}
    253
    254static __poll_t ringbuf_map_poll(struct bpf_map *map, struct file *filp,
    255				 struct poll_table_struct *pts)
    256{
    257	struct bpf_ringbuf_map *rb_map;
    258
    259	rb_map = container_of(map, struct bpf_ringbuf_map, map);
    260	poll_wait(filp, &rb_map->rb->waitq, pts);
    261
    262	if (ringbuf_avail_data_sz(rb_map->rb))
    263		return EPOLLIN | EPOLLRDNORM;
    264	return 0;
    265}
    266
    267BTF_ID_LIST_SINGLE(ringbuf_map_btf_ids, struct, bpf_ringbuf_map)
    268const struct bpf_map_ops ringbuf_map_ops = {
    269	.map_meta_equal = bpf_map_meta_equal,
    270	.map_alloc = ringbuf_map_alloc,
    271	.map_free = ringbuf_map_free,
    272	.map_mmap = ringbuf_map_mmap,
    273	.map_poll = ringbuf_map_poll,
    274	.map_lookup_elem = ringbuf_map_lookup_elem,
    275	.map_update_elem = ringbuf_map_update_elem,
    276	.map_delete_elem = ringbuf_map_delete_elem,
    277	.map_get_next_key = ringbuf_map_get_next_key,
    278	.map_btf_id = &ringbuf_map_btf_ids[0],
    279};
    280
    281/* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself,
    282 * calculate offset from record metadata to ring buffer in pages, rounded
    283 * down. This page offset is stored as part of record metadata and allows to
    284 * restore struct bpf_ringbuf * from record pointer. This page offset is
    285 * stored at offset 4 of record metadata header.
    286 */
    287static size_t bpf_ringbuf_rec_pg_off(struct bpf_ringbuf *rb,
    288				     struct bpf_ringbuf_hdr *hdr)
    289{
    290	return ((void *)hdr - (void *)rb) >> PAGE_SHIFT;
    291}
    292
    293/* Given pointer to ring buffer record header, restore pointer to struct
    294 * bpf_ringbuf itself by using page offset stored at offset 4
    295 */
    296static struct bpf_ringbuf *
    297bpf_ringbuf_restore_from_rec(struct bpf_ringbuf_hdr *hdr)
    298{
    299	unsigned long addr = (unsigned long)(void *)hdr;
    300	unsigned long off = (unsigned long)hdr->pg_off << PAGE_SHIFT;
    301
    302	return (void*)((addr & PAGE_MASK) - off);
    303}
    304
    305static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size)
    306{
    307	unsigned long cons_pos, prod_pos, new_prod_pos, flags;
    308	u32 len, pg_off;
    309	struct bpf_ringbuf_hdr *hdr;
    310
    311	if (unlikely(size > RINGBUF_MAX_RECORD_SZ))
    312		return NULL;
    313
    314	len = round_up(size + BPF_RINGBUF_HDR_SZ, 8);
    315	if (len > rb->mask + 1)
    316		return NULL;
    317
    318	cons_pos = smp_load_acquire(&rb->consumer_pos);
    319
    320	if (in_nmi()) {
    321		if (!spin_trylock_irqsave(&rb->spinlock, flags))
    322			return NULL;
    323	} else {
    324		spin_lock_irqsave(&rb->spinlock, flags);
    325	}
    326
    327	prod_pos = rb->producer_pos;
    328	new_prod_pos = prod_pos + len;
    329
    330	/* check for out of ringbuf space by ensuring producer position
    331	 * doesn't advance more than (ringbuf_size - 1) ahead
    332	 */
    333	if (new_prod_pos - cons_pos > rb->mask) {
    334		spin_unlock_irqrestore(&rb->spinlock, flags);
    335		return NULL;
    336	}
    337
    338	hdr = (void *)rb->data + (prod_pos & rb->mask);
    339	pg_off = bpf_ringbuf_rec_pg_off(rb, hdr);
    340	hdr->len = size | BPF_RINGBUF_BUSY_BIT;
    341	hdr->pg_off = pg_off;
    342
    343	/* pairs with consumer's smp_load_acquire() */
    344	smp_store_release(&rb->producer_pos, new_prod_pos);
    345
    346	spin_unlock_irqrestore(&rb->spinlock, flags);
    347
    348	return (void *)hdr + BPF_RINGBUF_HDR_SZ;
    349}
    350
    351BPF_CALL_3(bpf_ringbuf_reserve, struct bpf_map *, map, u64, size, u64, flags)
    352{
    353	struct bpf_ringbuf_map *rb_map;
    354
    355	if (unlikely(flags))
    356		return 0;
    357
    358	rb_map = container_of(map, struct bpf_ringbuf_map, map);
    359	return (unsigned long)__bpf_ringbuf_reserve(rb_map->rb, size);
    360}
    361
    362const struct bpf_func_proto bpf_ringbuf_reserve_proto = {
    363	.func		= bpf_ringbuf_reserve,
    364	.ret_type	= RET_PTR_TO_ALLOC_MEM_OR_NULL,
    365	.arg1_type	= ARG_CONST_MAP_PTR,
    366	.arg2_type	= ARG_CONST_ALLOC_SIZE_OR_ZERO,
    367	.arg3_type	= ARG_ANYTHING,
    368};
    369
    370static void bpf_ringbuf_commit(void *sample, u64 flags, bool discard)
    371{
    372	unsigned long rec_pos, cons_pos;
    373	struct bpf_ringbuf_hdr *hdr;
    374	struct bpf_ringbuf *rb;
    375	u32 new_len;
    376
    377	hdr = sample - BPF_RINGBUF_HDR_SZ;
    378	rb = bpf_ringbuf_restore_from_rec(hdr);
    379	new_len = hdr->len ^ BPF_RINGBUF_BUSY_BIT;
    380	if (discard)
    381		new_len |= BPF_RINGBUF_DISCARD_BIT;
    382
    383	/* update record header with correct final size prefix */
    384	xchg(&hdr->len, new_len);
    385
    386	/* if consumer caught up and is waiting for our record, notify about
    387	 * new data availability
    388	 */
    389	rec_pos = (void *)hdr - (void *)rb->data;
    390	cons_pos = smp_load_acquire(&rb->consumer_pos) & rb->mask;
    391
    392	if (flags & BPF_RB_FORCE_WAKEUP)
    393		irq_work_queue(&rb->work);
    394	else if (cons_pos == rec_pos && !(flags & BPF_RB_NO_WAKEUP))
    395		irq_work_queue(&rb->work);
    396}
    397
    398BPF_CALL_2(bpf_ringbuf_submit, void *, sample, u64, flags)
    399{
    400	bpf_ringbuf_commit(sample, flags, false /* discard */);
    401	return 0;
    402}
    403
    404const struct bpf_func_proto bpf_ringbuf_submit_proto = {
    405	.func		= bpf_ringbuf_submit,
    406	.ret_type	= RET_VOID,
    407	.arg1_type	= ARG_PTR_TO_ALLOC_MEM | OBJ_RELEASE,
    408	.arg2_type	= ARG_ANYTHING,
    409};
    410
    411BPF_CALL_2(bpf_ringbuf_discard, void *, sample, u64, flags)
    412{
    413	bpf_ringbuf_commit(sample, flags, true /* discard */);
    414	return 0;
    415}
    416
    417const struct bpf_func_proto bpf_ringbuf_discard_proto = {
    418	.func		= bpf_ringbuf_discard,
    419	.ret_type	= RET_VOID,
    420	.arg1_type	= ARG_PTR_TO_ALLOC_MEM | OBJ_RELEASE,
    421	.arg2_type	= ARG_ANYTHING,
    422};
    423
    424BPF_CALL_4(bpf_ringbuf_output, struct bpf_map *, map, void *, data, u64, size,
    425	   u64, flags)
    426{
    427	struct bpf_ringbuf_map *rb_map;
    428	void *rec;
    429
    430	if (unlikely(flags & ~(BPF_RB_NO_WAKEUP | BPF_RB_FORCE_WAKEUP)))
    431		return -EINVAL;
    432
    433	rb_map = container_of(map, struct bpf_ringbuf_map, map);
    434	rec = __bpf_ringbuf_reserve(rb_map->rb, size);
    435	if (!rec)
    436		return -EAGAIN;
    437
    438	memcpy(rec, data, size);
    439	bpf_ringbuf_commit(rec, flags, false /* discard */);
    440	return 0;
    441}
    442
    443const struct bpf_func_proto bpf_ringbuf_output_proto = {
    444	.func		= bpf_ringbuf_output,
    445	.ret_type	= RET_INTEGER,
    446	.arg1_type	= ARG_CONST_MAP_PTR,
    447	.arg2_type	= ARG_PTR_TO_MEM | MEM_RDONLY,
    448	.arg3_type	= ARG_CONST_SIZE_OR_ZERO,
    449	.arg4_type	= ARG_ANYTHING,
    450};
    451
    452BPF_CALL_2(bpf_ringbuf_query, struct bpf_map *, map, u64, flags)
    453{
    454	struct bpf_ringbuf *rb;
    455
    456	rb = container_of(map, struct bpf_ringbuf_map, map)->rb;
    457
    458	switch (flags) {
    459	case BPF_RB_AVAIL_DATA:
    460		return ringbuf_avail_data_sz(rb);
    461	case BPF_RB_RING_SIZE:
    462		return rb->mask + 1;
    463	case BPF_RB_CONS_POS:
    464		return smp_load_acquire(&rb->consumer_pos);
    465	case BPF_RB_PROD_POS:
    466		return smp_load_acquire(&rb->producer_pos);
    467	default:
    468		return 0;
    469	}
    470}
    471
    472const struct bpf_func_proto bpf_ringbuf_query_proto = {
    473	.func		= bpf_ringbuf_query,
    474	.ret_type	= RET_INTEGER,
    475	.arg1_type	= ARG_CONST_MAP_PTR,
    476	.arg2_type	= ARG_ANYTHING,
    477};
    478
    479BPF_CALL_4(bpf_ringbuf_reserve_dynptr, struct bpf_map *, map, u32, size, u64, flags,
    480	   struct bpf_dynptr_kern *, ptr)
    481{
    482	struct bpf_ringbuf_map *rb_map;
    483	void *sample;
    484	int err;
    485
    486	if (unlikely(flags)) {
    487		bpf_dynptr_set_null(ptr);
    488		return -EINVAL;
    489	}
    490
    491	err = bpf_dynptr_check_size(size);
    492	if (err) {
    493		bpf_dynptr_set_null(ptr);
    494		return err;
    495	}
    496
    497	rb_map = container_of(map, struct bpf_ringbuf_map, map);
    498
    499	sample = __bpf_ringbuf_reserve(rb_map->rb, size);
    500	if (!sample) {
    501		bpf_dynptr_set_null(ptr);
    502		return -EINVAL;
    503	}
    504
    505	bpf_dynptr_init(ptr, sample, BPF_DYNPTR_TYPE_RINGBUF, 0, size);
    506
    507	return 0;
    508}
    509
    510const struct bpf_func_proto bpf_ringbuf_reserve_dynptr_proto = {
    511	.func		= bpf_ringbuf_reserve_dynptr,
    512	.ret_type	= RET_INTEGER,
    513	.arg1_type	= ARG_CONST_MAP_PTR,
    514	.arg2_type	= ARG_ANYTHING,
    515	.arg3_type	= ARG_ANYTHING,
    516	.arg4_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | MEM_UNINIT,
    517};
    518
    519BPF_CALL_2(bpf_ringbuf_submit_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
    520{
    521	if (!ptr->data)
    522		return 0;
    523
    524	bpf_ringbuf_commit(ptr->data, flags, false /* discard */);
    525
    526	bpf_dynptr_set_null(ptr);
    527
    528	return 0;
    529}
    530
    531const struct bpf_func_proto bpf_ringbuf_submit_dynptr_proto = {
    532	.func		= bpf_ringbuf_submit_dynptr,
    533	.ret_type	= RET_VOID,
    534	.arg1_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
    535	.arg2_type	= ARG_ANYTHING,
    536};
    537
    538BPF_CALL_2(bpf_ringbuf_discard_dynptr, struct bpf_dynptr_kern *, ptr, u64, flags)
    539{
    540	if (!ptr->data)
    541		return 0;
    542
    543	bpf_ringbuf_commit(ptr->data, flags, true /* discard */);
    544
    545	bpf_dynptr_set_null(ptr);
    546
    547	return 0;
    548}
    549
    550const struct bpf_func_proto bpf_ringbuf_discard_dynptr_proto = {
    551	.func		= bpf_ringbuf_discard_dynptr,
    552	.ret_type	= RET_VOID,
    553	.arg1_type	= ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_RINGBUF | OBJ_RELEASE,
    554	.arg2_type	= ARG_ANYTHING,
    555};