Revision 63cae12bce9861cec309798d34701cf3da20bc71 authored by Peter Zijlstra on 09 December 2016, 13:59:00 UTC, committed by Ingo Molnar on 14 January 2017, 09:56:10 UTC
There is problem with installing an event in a task that is 'stuck' on
an offline CPU.
Blocked tasks are not dis-assosciated from offlined CPUs, after all, a
blocked task doesn't run and doesn't require a CPU etc.. Only on
wakeup do we ammend the situation and place the task on a available
CPU.
If we hit such a task with perf_install_in_context() we'll loop until
either that task wakes up or the CPU comes back online, if the task
waking depends on the event being installed, we're stuck.
While looking into this issue, I also spotted another problem, if we
hit a task with perf_install_in_context() that is in the middle of
being migrated, that is we observe the old CPU before sending the IPI,
but run the IPI (on the old CPU) while the task is already running on
the new CPU, things also go sideways.
Rework things to rely on task_curr() -- outside of rq->lock -- which
is rather tricky. Imagine the following scenario where we're trying to
install the first event into our task 't':
CPU0 CPU1 CPU2
(current == t)
t->perf_event_ctxp[] = ctx;
smp_mb();
cpu = task_cpu(t);
switch(t, n);
migrate(t, 2);
switch(p, t);
ctx = t->perf_event_ctxp[]; // must not be NULL
smp_function_call(cpu, ..);
generic_exec_single()
func();
spin_lock(ctx->lock);
if (task_curr(t)) // false
add_event_to_ctx();
spin_unlock(ctx->lock);
perf_event_context_sched_in();
spin_lock(ctx->lock);
// sees event
So its CPU0's store of t->perf_event_ctxp[] that must not go 'missing'.
Because if CPU2's load of that variable were to observe NULL, it would
not try to schedule the ctx and we'd have a task running without its
counter, which would be 'bad'.
As long as we observe !NULL, we'll acquire ctx->lock. If we acquire it
first and not see the event yet, then CPU0 must observe task_curr()
and retry. If the install happens first, then we must see the event on
sched-in and all is well.
I think we can translate the first part (until the 'must not be NULL')
of the scenario to a litmus test like:
C C-peterz
{
}
P0(int *x, int *y)
{
int r1;
WRITE_ONCE(*x, 1);
smp_mb();
r1 = READ_ONCE(*y);
}
P1(int *y, int *z)
{
WRITE_ONCE(*y, 1);
smp_store_release(z, 1);
}
P2(int *x, int *z)
{
int r1;
int r2;
r1 = smp_load_acquire(z);
smp_mb();
r2 = READ_ONCE(*x);
}
exists
(0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
Where:
x is perf_event_ctxp[],
y is our tasks's CPU, and
z is our task being placed on the rq of CPU2.
The P0 smp_mb() is the one added by this patch, ordering the store to
perf_event_ctxp[] from find_get_context() and the load of task_cpu()
in task_function_call().
The smp_store_release/smp_load_acquire model the RCpc locking of the
rq->lock and the smp_mb() of P2 is the context switch switching from
whatever CPU2 was running to our task 't'.
This litmus test evaluates into:
Test C-peterz Allowed
States 7
0:r1=0; 2:r1=0; 2:r2=0;
0:r1=0; 2:r1=0; 2:r2=1;
0:r1=0; 2:r1=1; 2:r2=1;
0:r1=1; 2:r1=0; 2:r2=0;
0:r1=1; 2:r1=0; 2:r2=1;
0:r1=1; 2:r1=1; 2:r2=0;
0:r1=1; 2:r1=1; 2:r2=1;
No
Witnesses
Positive: 0 Negative: 7
Condition exists (0:r1=0 /\ 2:r1=1 /\ 2:r2=0)
Observation C-peterz Never 0 7
Hash=e427f41d9146b2a5445101d3e2fcaa34
And the strong and weak model agree.
Reported-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Will Deacon <will.deacon@arm.com>
Cc: jeremy.linton@arm.com
Link: http://lkml.kernel.org/r/20161209135900.GU3174@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1 parent ad5013d
blkcipher.c
/*
* Block chaining cipher operations.
*
* Generic encrypt/decrypt wrapper for ciphers, handles operations across
* multiple page boundaries by using temporary blocks. In user context,
* the kernel is given a chance to schedule us once per page.
*
* Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
*/
#include <crypto/aead.h>
#include <crypto/internal/skcipher.h>
#include <crypto/scatterwalk.h>
#include <linux/errno.h>
#include <linux/hardirq.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/cryptouser.h>
#include <net/netlink.h>
#include "internal.h"
enum {
BLKCIPHER_WALK_PHYS = 1 << 0,
BLKCIPHER_WALK_SLOW = 1 << 1,
BLKCIPHER_WALK_COPY = 1 << 2,
BLKCIPHER_WALK_DIFF = 1 << 3,
};
static int blkcipher_walk_next(struct blkcipher_desc *desc,
struct blkcipher_walk *walk);
static int blkcipher_walk_first(struct blkcipher_desc *desc,
struct blkcipher_walk *walk);
static inline void blkcipher_map_src(struct blkcipher_walk *walk)
{
walk->src.virt.addr = scatterwalk_map(&walk->in);
}
static inline void blkcipher_map_dst(struct blkcipher_walk *walk)
{
walk->dst.virt.addr = scatterwalk_map(&walk->out);
}
static inline void blkcipher_unmap_src(struct blkcipher_walk *walk)
{
scatterwalk_unmap(walk->src.virt.addr);
}
static inline void blkcipher_unmap_dst(struct blkcipher_walk *walk)
{
scatterwalk_unmap(walk->dst.virt.addr);
}
/* Get a spot of the specified length that does not straddle a page.
* The caller needs to ensure that there is enough space for this operation.
*/
static inline u8 *blkcipher_get_spot(u8 *start, unsigned int len)
{
u8 *end_page = (u8 *)(((unsigned long)(start + len - 1)) & PAGE_MASK);
return max(start, end_page);
}
static inline unsigned int blkcipher_done_slow(struct blkcipher_walk *walk,
unsigned int bsize)
{
u8 *addr;
addr = (u8 *)ALIGN((unsigned long)walk->buffer, walk->alignmask + 1);
addr = blkcipher_get_spot(addr, bsize);
scatterwalk_copychunks(addr, &walk->out, bsize, 1);
return bsize;
}
static inline unsigned int blkcipher_done_fast(struct blkcipher_walk *walk,
unsigned int n)
{
if (walk->flags & BLKCIPHER_WALK_COPY) {
blkcipher_map_dst(walk);
memcpy(walk->dst.virt.addr, walk->page, n);
blkcipher_unmap_dst(walk);
} else if (!(walk->flags & BLKCIPHER_WALK_PHYS)) {
if (walk->flags & BLKCIPHER_WALK_DIFF)
blkcipher_unmap_dst(walk);
blkcipher_unmap_src(walk);
}
scatterwalk_advance(&walk->in, n);
scatterwalk_advance(&walk->out, n);
return n;
}
int blkcipher_walk_done(struct blkcipher_desc *desc,
struct blkcipher_walk *walk, int err)
{
unsigned int nbytes = 0;
if (likely(err >= 0)) {
unsigned int n = walk->nbytes - err;
if (likely(!(walk->flags & BLKCIPHER_WALK_SLOW)))
n = blkcipher_done_fast(walk, n);
else if (WARN_ON(err)) {
err = -EINVAL;
goto err;
} else
n = blkcipher_done_slow(walk, n);
nbytes = walk->total - n;
err = 0;
}
scatterwalk_done(&walk->in, 0, nbytes);
scatterwalk_done(&walk->out, 1, nbytes);
err:
walk->total = nbytes;
walk->nbytes = nbytes;
if (nbytes) {
crypto_yield(desc->flags);
return blkcipher_walk_next(desc, walk);
}
if (walk->iv != desc->info)
memcpy(desc->info, walk->iv, walk->ivsize);
if (walk->buffer != walk->page)
kfree(walk->buffer);
if (walk->page)
free_page((unsigned long)walk->page);
return err;
}
EXPORT_SYMBOL_GPL(blkcipher_walk_done);
static inline int blkcipher_next_slow(struct blkcipher_desc *desc,
struct blkcipher_walk *walk,
unsigned int bsize,
unsigned int alignmask)
{
unsigned int n;
unsigned aligned_bsize = ALIGN(bsize, alignmask + 1);
if (walk->buffer)
goto ok;
walk->buffer = walk->page;
if (walk->buffer)
goto ok;
n = aligned_bsize * 3 - (alignmask + 1) +
(alignmask & ~(crypto_tfm_ctx_alignment() - 1));
walk->buffer = kmalloc(n, GFP_ATOMIC);
if (!walk->buffer)
return blkcipher_walk_done(desc, walk, -ENOMEM);
ok:
walk->dst.virt.addr = (u8 *)ALIGN((unsigned long)walk->buffer,
alignmask + 1);
walk->dst.virt.addr = blkcipher_get_spot(walk->dst.virt.addr, bsize);
walk->src.virt.addr = blkcipher_get_spot(walk->dst.virt.addr +
aligned_bsize, bsize);
scatterwalk_copychunks(walk->src.virt.addr, &walk->in, bsize, 0);
walk->nbytes = bsize;
walk->flags |= BLKCIPHER_WALK_SLOW;
return 0;
}
static inline int blkcipher_next_copy(struct blkcipher_walk *walk)
{
u8 *tmp = walk->page;
blkcipher_map_src(walk);
memcpy(tmp, walk->src.virt.addr, walk->nbytes);
blkcipher_unmap_src(walk);
walk->src.virt.addr = tmp;
walk->dst.virt.addr = tmp;
return 0;
}
static inline int blkcipher_next_fast(struct blkcipher_desc *desc,
struct blkcipher_walk *walk)
{
unsigned long diff;
walk->src.phys.page = scatterwalk_page(&walk->in);
walk->src.phys.offset = offset_in_page(walk->in.offset);
walk->dst.phys.page = scatterwalk_page(&walk->out);
walk->dst.phys.offset = offset_in_page(walk->out.offset);
if (walk->flags & BLKCIPHER_WALK_PHYS)
return 0;
diff = walk->src.phys.offset - walk->dst.phys.offset;
diff |= walk->src.virt.page - walk->dst.virt.page;
blkcipher_map_src(walk);
walk->dst.virt.addr = walk->src.virt.addr;
if (diff) {
walk->flags |= BLKCIPHER_WALK_DIFF;
blkcipher_map_dst(walk);
}
return 0;
}
static int blkcipher_walk_next(struct blkcipher_desc *desc,
struct blkcipher_walk *walk)
{
unsigned int bsize;
unsigned int n;
int err;
n = walk->total;
if (unlikely(n < walk->cipher_blocksize)) {
desc->flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
return blkcipher_walk_done(desc, walk, -EINVAL);
}
bsize = min(walk->walk_blocksize, n);
walk->flags &= ~(BLKCIPHER_WALK_SLOW | BLKCIPHER_WALK_COPY |
BLKCIPHER_WALK_DIFF);
if (!scatterwalk_aligned(&walk->in, walk->alignmask) ||
!scatterwalk_aligned(&walk->out, walk->alignmask)) {
walk->flags |= BLKCIPHER_WALK_COPY;
if (!walk->page) {
walk->page = (void *)__get_free_page(GFP_ATOMIC);
if (!walk->page)
n = 0;
}
}
n = scatterwalk_clamp(&walk->in, n);
n = scatterwalk_clamp(&walk->out, n);
if (unlikely(n < bsize)) {
err = blkcipher_next_slow(desc, walk, bsize, walk->alignmask);
goto set_phys_lowmem;
}
walk->nbytes = n;
if (walk->flags & BLKCIPHER_WALK_COPY) {
err = blkcipher_next_copy(walk);
goto set_phys_lowmem;
}
return blkcipher_next_fast(desc, walk);
set_phys_lowmem:
if (walk->flags & BLKCIPHER_WALK_PHYS) {
walk->src.phys.page = virt_to_page(walk->src.virt.addr);
walk->dst.phys.page = virt_to_page(walk->dst.virt.addr);
walk->src.phys.offset &= PAGE_SIZE - 1;
walk->dst.phys.offset &= PAGE_SIZE - 1;
}
return err;
}
static inline int blkcipher_copy_iv(struct blkcipher_walk *walk)
{
unsigned bs = walk->walk_blocksize;
unsigned aligned_bs = ALIGN(bs, walk->alignmask + 1);
unsigned int size = aligned_bs * 2 +
walk->ivsize + max(aligned_bs, walk->ivsize) -
(walk->alignmask + 1);
u8 *iv;
size += walk->alignmask & ~(crypto_tfm_ctx_alignment() - 1);
walk->buffer = kmalloc(size, GFP_ATOMIC);
if (!walk->buffer)
return -ENOMEM;
iv = (u8 *)ALIGN((unsigned long)walk->buffer, walk->alignmask + 1);
iv = blkcipher_get_spot(iv, bs) + aligned_bs;
iv = blkcipher_get_spot(iv, bs) + aligned_bs;
iv = blkcipher_get_spot(iv, walk->ivsize);
walk->iv = memcpy(iv, walk->iv, walk->ivsize);
return 0;
}
int blkcipher_walk_virt(struct blkcipher_desc *desc,
struct blkcipher_walk *walk)
{
walk->flags &= ~BLKCIPHER_WALK_PHYS;
walk->walk_blocksize = crypto_blkcipher_blocksize(desc->tfm);
walk->cipher_blocksize = walk->walk_blocksize;
walk->ivsize = crypto_blkcipher_ivsize(desc->tfm);
walk->alignmask = crypto_blkcipher_alignmask(desc->tfm);
return blkcipher_walk_first(desc, walk);
}
EXPORT_SYMBOL_GPL(blkcipher_walk_virt);
int blkcipher_walk_phys(struct blkcipher_desc *desc,
struct blkcipher_walk *walk)
{
walk->flags |= BLKCIPHER_WALK_PHYS;
walk->walk_blocksize = crypto_blkcipher_blocksize(desc->tfm);
walk->cipher_blocksize = walk->walk_blocksize;
walk->ivsize = crypto_blkcipher_ivsize(desc->tfm);
walk->alignmask = crypto_blkcipher_alignmask(desc->tfm);
return blkcipher_walk_first(desc, walk);
}
EXPORT_SYMBOL_GPL(blkcipher_walk_phys);
static int blkcipher_walk_first(struct blkcipher_desc *desc,
struct blkcipher_walk *walk)
{
if (WARN_ON_ONCE(in_irq()))
return -EDEADLK;
walk->iv = desc->info;
walk->nbytes = walk->total;
if (unlikely(!walk->total))
return 0;
walk->buffer = NULL;
if (unlikely(((unsigned long)walk->iv & walk->alignmask))) {
int err = blkcipher_copy_iv(walk);
if (err)
return err;
}
scatterwalk_start(&walk->in, walk->in.sg);
scatterwalk_start(&walk->out, walk->out.sg);
walk->page = NULL;
return blkcipher_walk_next(desc, walk);
}
int blkcipher_walk_virt_block(struct blkcipher_desc *desc,
struct blkcipher_walk *walk,
unsigned int blocksize)
{
walk->flags &= ~BLKCIPHER_WALK_PHYS;
walk->walk_blocksize = blocksize;
walk->cipher_blocksize = crypto_blkcipher_blocksize(desc->tfm);
walk->ivsize = crypto_blkcipher_ivsize(desc->tfm);
walk->alignmask = crypto_blkcipher_alignmask(desc->tfm);
return blkcipher_walk_first(desc, walk);
}
EXPORT_SYMBOL_GPL(blkcipher_walk_virt_block);
int blkcipher_aead_walk_virt_block(struct blkcipher_desc *desc,
struct blkcipher_walk *walk,
struct crypto_aead *tfm,
unsigned int blocksize)
{
walk->flags &= ~BLKCIPHER_WALK_PHYS;
walk->walk_blocksize = blocksize;
walk->cipher_blocksize = crypto_aead_blocksize(tfm);
walk->ivsize = crypto_aead_ivsize(tfm);
walk->alignmask = crypto_aead_alignmask(tfm);
return blkcipher_walk_first(desc, walk);
}
EXPORT_SYMBOL_GPL(blkcipher_aead_walk_virt_block);
static int setkey_unaligned(struct crypto_tfm *tfm, const u8 *key,
unsigned int keylen)
{
struct blkcipher_alg *cipher = &tfm->__crt_alg->cra_blkcipher;
unsigned long alignmask = crypto_tfm_alg_alignmask(tfm);
int ret;
u8 *buffer, *alignbuffer;
unsigned long absize;
absize = keylen + alignmask;
buffer = kmalloc(absize, GFP_ATOMIC);
if (!buffer)
return -ENOMEM;
alignbuffer = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1);
memcpy(alignbuffer, key, keylen);
ret = cipher->setkey(tfm, alignbuffer, keylen);
memset(alignbuffer, 0, keylen);
kfree(buffer);
return ret;
}
static int setkey(struct crypto_tfm *tfm, const u8 *key, unsigned int keylen)
{
struct blkcipher_alg *cipher = &tfm->__crt_alg->cra_blkcipher;
unsigned long alignmask = crypto_tfm_alg_alignmask(tfm);
if (keylen < cipher->min_keysize || keylen > cipher->max_keysize) {
tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
return -EINVAL;
}
if ((unsigned long)key & alignmask)
return setkey_unaligned(tfm, key, keylen);
return cipher->setkey(tfm, key, keylen);
}
static int async_setkey(struct crypto_ablkcipher *tfm, const u8 *key,
unsigned int keylen)
{
return setkey(crypto_ablkcipher_tfm(tfm), key, keylen);
}
static int async_encrypt(struct ablkcipher_request *req)
{
struct crypto_tfm *tfm = req->base.tfm;
struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;
struct blkcipher_desc desc = {
.tfm = __crypto_blkcipher_cast(tfm),
.info = req->info,
.flags = req->base.flags,
};
return alg->encrypt(&desc, req->dst, req->src, req->nbytes);
}
static int async_decrypt(struct ablkcipher_request *req)
{
struct crypto_tfm *tfm = req->base.tfm;
struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;
struct blkcipher_desc desc = {
.tfm = __crypto_blkcipher_cast(tfm),
.info = req->info,
.flags = req->base.flags,
};
return alg->decrypt(&desc, req->dst, req->src, req->nbytes);
}
static unsigned int crypto_blkcipher_ctxsize(struct crypto_alg *alg, u32 type,
u32 mask)
{
struct blkcipher_alg *cipher = &alg->cra_blkcipher;
unsigned int len = alg->cra_ctxsize;
if ((mask & CRYPTO_ALG_TYPE_MASK) == CRYPTO_ALG_TYPE_MASK &&
cipher->ivsize) {
len = ALIGN(len, (unsigned long)alg->cra_alignmask + 1);
len += cipher->ivsize;
}
return len;
}
static int crypto_init_blkcipher_ops_async(struct crypto_tfm *tfm)
{
struct ablkcipher_tfm *crt = &tfm->crt_ablkcipher;
struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;
crt->setkey = async_setkey;
crt->encrypt = async_encrypt;
crt->decrypt = async_decrypt;
crt->base = __crypto_ablkcipher_cast(tfm);
crt->ivsize = alg->ivsize;
return 0;
}
static int crypto_init_blkcipher_ops_sync(struct crypto_tfm *tfm)
{
struct blkcipher_tfm *crt = &tfm->crt_blkcipher;
struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;
unsigned long align = crypto_tfm_alg_alignmask(tfm) + 1;
unsigned long addr;
crt->setkey = setkey;
crt->encrypt = alg->encrypt;
crt->decrypt = alg->decrypt;
addr = (unsigned long)crypto_tfm_ctx(tfm);
addr = ALIGN(addr, align);
addr += ALIGN(tfm->__crt_alg->cra_ctxsize, align);
crt->iv = (void *)addr;
return 0;
}
static int crypto_init_blkcipher_ops(struct crypto_tfm *tfm, u32 type, u32 mask)
{
struct blkcipher_alg *alg = &tfm->__crt_alg->cra_blkcipher;
if (alg->ivsize > PAGE_SIZE / 8)
return -EINVAL;
if ((mask & CRYPTO_ALG_TYPE_MASK) == CRYPTO_ALG_TYPE_MASK)
return crypto_init_blkcipher_ops_sync(tfm);
else
return crypto_init_blkcipher_ops_async(tfm);
}
#ifdef CONFIG_NET
static int crypto_blkcipher_report(struct sk_buff *skb, struct crypto_alg *alg)
{
struct crypto_report_blkcipher rblkcipher;
strncpy(rblkcipher.type, "blkcipher", sizeof(rblkcipher.type));
strncpy(rblkcipher.geniv, alg->cra_blkcipher.geniv ?: "<default>",
sizeof(rblkcipher.geniv));
rblkcipher.blocksize = alg->cra_blocksize;
rblkcipher.min_keysize = alg->cra_blkcipher.min_keysize;
rblkcipher.max_keysize = alg->cra_blkcipher.max_keysize;
rblkcipher.ivsize = alg->cra_blkcipher.ivsize;
if (nla_put(skb, CRYPTOCFGA_REPORT_BLKCIPHER,
sizeof(struct crypto_report_blkcipher), &rblkcipher))
goto nla_put_failure;
return 0;
nla_put_failure:
return -EMSGSIZE;
}
#else
static int crypto_blkcipher_report(struct sk_buff *skb, struct crypto_alg *alg)
{
return -ENOSYS;
}
#endif
static void crypto_blkcipher_show(struct seq_file *m, struct crypto_alg *alg)
__attribute__ ((unused));
static void crypto_blkcipher_show(struct seq_file *m, struct crypto_alg *alg)
{
seq_printf(m, "type : blkcipher\n");
seq_printf(m, "blocksize : %u\n", alg->cra_blocksize);
seq_printf(m, "min keysize : %u\n", alg->cra_blkcipher.min_keysize);
seq_printf(m, "max keysize : %u\n", alg->cra_blkcipher.max_keysize);
seq_printf(m, "ivsize : %u\n", alg->cra_blkcipher.ivsize);
seq_printf(m, "geniv : %s\n", alg->cra_blkcipher.geniv ?:
"<default>");
}
const struct crypto_type crypto_blkcipher_type = {
.ctxsize = crypto_blkcipher_ctxsize,
.init = crypto_init_blkcipher_ops,
#ifdef CONFIG_PROC_FS
.show = crypto_blkcipher_show,
#endif
.report = crypto_blkcipher_report,
};
EXPORT_SYMBOL_GPL(crypto_blkcipher_type);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Generic block chaining cipher type");
Computing file changes ...
