leandrof/linux
1
0
Fork 0
forked from Minki/linux
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Merge branch 'bpf-get-stackid'

Browse Source 
Alexei Starovoitov says:

====================
bpf_get_stackid() and stack_trace map

This patch set introduces new map type to store stack traces and
corresponding bpf_get_stackid() helper.
BPF programs already can walk the stack via unrolled loop
of bpf_probe_read()s which is ok for simple analysis, but it's
not efficient and limited to <30 frames after that the programs
don't fit into MAX_BPF_STACK. With bpf_get_stackid() helper
the programs can collect up to PERF_MAX_STACK_DEPTH both
user and kernel frames.
Using stack traces as a key in a map turned out to be very useful
for generating flame graphs, off-cpu graphs, waker and chain graphs.
Patch 3 is a simplified version of 'offwaketime' tool which is
described in detail here:
http://brendangregg.com/blog/2016-02-01/linux-wakeup-offwake-profiling.html

Earlier version of this patch were using save_stack_trace() helper,
but 'unreliable' frames add to much noise and two equiavlent
stack traces produce different 'stackid's.
Using lockdep style of storing frames with MAX_STACK_TRACE_ENTRIES is
great for lockdep, but not acceptable for bpf, since the stack_trace
map needs to be freed when user Ctrl-C the tool.
The ftrace style with per_cpu(struct ftrace_stack) is great, but it's
tightly coupled with ftrace ring buffer and has the same 'unreliable'
noise. perf_event's perf_callchain() mechanism is also very efficient
and it only needed minor generalization which is done in patch 1
to be used by bpf stack_trace maps.
Peter, please take a look at patch 1.
If you're ok with it, I'd like to take the whole set via net-next.

Patch 1 - generalization of perf_callchain()
Patch 2 - stack_trace map done as lock-less hashtable without link list
  to avoid spinlock on insertion which is critical path when
  bpf_get_stackid() helper is called for every task switch event
Patch 3 - offwaketime example

After the patch the 'perf report' for artificial 'sched_bench'
benchmark that doing pthread_cond_wait/signal and 'offwaketime'
example is running in the background:
 16.35%  swapper      [kernel.vmlinux]    [k] intel_idle
  2.18%  sched_bench  [kernel.vmlinux]    [k] __switch_to
  2.18%  sched_bench  libpthread-2.12.so  [.] pthread_cond_signal@@GLIBC_2.3.2
  1.72%  sched_bench  libpthread-2.12.so  [.] pthread_mutex_unlock
  1.53%  sched_bench  [kernel.vmlinux]    [k] bpf_get_stackid
  1.44%  sched_bench  [kernel.vmlinux]    [k] entry_SYSCALL_64
  1.39%  sched_bench  [kernel.vmlinux]    [k] __call_rcu.constprop.73
  1.13%  sched_bench  libpthread-2.12.so  [.] pthread_mutex_lock
  1.07%  sched_bench  libpthread-2.12.so  [.] pthread_cond_wait@@GLIBC_2.3.2
  1.07%  sched_bench  [kernel.vmlinux]    [k] hash_futex
  1.05%  sched_bench  [kernel.vmlinux]    [k] do_futex
  1.05%  sched_bench  [kernel.vmlinux]    [k] get_futex_key_refs.isra.13

The hotest part of bpf_get_stackid() is inlined jhash2, so we may consider
using some faster hash in the future, but it's good enough for now.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2016-02-20 00:21:44 -05:00
commit 80c804bfc4
18 changed files with 642 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/include/asm/stacktrace.h
View File

@ -37,7 +37,7 @@ print_context_stack_bp(struct thread_info *tinfo,
/* Generic stack tracer with callbacks */
struct stacktrace_ops {
void (*address)(void *data, unsigned long address, int reliable);
int (*address)(void *data, unsigned long address, int reliable);
/* On negative return stop dumping */
int (*stack)(void *data, char *name);
walk_stack_t walk_stack;

4
arch/x86/kernel/cpu/perf_event.c
View File

@ -2180,11 +2180,11 @@ static int backtrace_stack(void *data, char *name)
return 0;
}
static void backtrace_address(void *data, unsigned long addr, int reliable)
static int backtrace_address(void *data, unsigned long addr, int reliable)
{
struct perf_callchain_entry *entry = data;
perf_callchain_store(entry, addr);
return perf_callchain_store(entry, addr);
}
static const struct stacktrace_ops backtrace_ops = {

6
arch/x86/kernel/dumpstack.c
View File

@ -135,7 +135,8 @@ print_context_stack_bp(struct thread_info *tinfo,
if (!__kernel_text_address(addr))
break;
ops->address(data, addr, 1);
if (ops->address(data, addr, 1))
break;
frame = frame->next_frame;
ret_addr = &frame->return_address;
print_ftrace_graph_addr(addr, data, ops, tinfo, graph);
@ -154,10 +155,11 @@ static int print_trace_stack(void *data, char *name)
/*
* Print one address/symbol entries per line.
*/
static void print_trace_address(void *data, unsigned long addr, int reliable)
static int print_trace_address(void *data, unsigned long addr, int reliable)
{
touch_nmi_watchdog();
printk_stack_address(addr, reliable, data);
return 0;
}
static const struct stacktrace_ops print_trace_ops = {

18
arch/x86/kernel/stacktrace.c
View File

@ -14,30 +14,34 @@ static int save_stack_stack(void *data, char *name)
return 0;
}
static void
static int
__save_stack_address(void *data, unsigned long addr, bool reliable, bool nosched)
{
struct stack_trace *trace = data;
#ifdef CONFIG_FRAME_POINTER
if (!reliable)
return;
return 0;
#endif
if (nosched && in_sched_functions(addr))
return;
return 0;
if (trace->skip > 0) {
trace->skip--;
return;
return 0;
}
if (trace->nr_entries < trace->max_entries)
if (trace->nr_entries < trace->max_entries) {
trace->entries[trace->nr_entries++] = addr;
return 0;
} else {
return -1; /* no more room, stop walking the stack */
}
}
static void save_stack_address(void *data, unsigned long addr, int reliable)
static int save_stack_address(void *data, unsigned long addr, int reliable)
{
return __save_stack_address(data, addr, reliable, false);
}
static void
static int
save_stack_address_nosched(void *data, unsigned long addr, int reliable)
{
return __save_stack_address(data, addr, reliable, true);

3
arch/x86/oprofile/backtrace.c
View File

@ -23,12 +23,13 @@ static int backtrace_stack(void *data, char *name)
return 0;
}
static void backtrace_address(void *data, unsigned long addr, int reliable)
static int backtrace_address(void *data, unsigned long addr, int reliable)
{
unsigned int *depth = data;
if ((*depth)--)
oprofile_add_trace(addr);
return 0;
}
static struct stacktrace_ops backtrace_ops = {

1
include/linux/bpf.h
View File

@ -237,6 +237,7 @@ extern const struct bpf_func_proto bpf_get_current_uid_gid_proto;
extern const struct bpf_func_proto bpf_get_current_comm_proto;
extern const struct bpf_func_proto bpf_skb_vlan_push_proto;
extern const struct bpf_func_proto bpf_skb_vlan_pop_proto;
extern const struct bpf_func_proto bpf_get_stackid_proto;
/* Shared helpers among cBPF and eBPF. */
void bpf_user_rnd_init_once(void);

13
include/linux/perf_event.h
View File

@ -964,11 +964,20 @@ DECLARE_PER_CPU(struct perf_callchain_entry, perf_callchain_entry);
extern void perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs);
extern void perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs);
extern struct perf_callchain_entry *
get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
bool crosstask, bool add_mark);
extern int get_callchain_buffers(void);
extern void put_callchain_buffers(void);
static inline void perf_callchain_store(struct perf_callchain_entry *entry, u64 ip)
static inline int perf_callchain_store(struct perf_callchain_entry *entry, u64 ip)
{
if (entry->nr < PERF_MAX_STACK_DEPTH)
if (entry->nr < PERF_MAX_STACK_DEPTH) {
entry->ip[entry->nr++] = ip;
return 0;
} else {
return -1; /* no more room, stop walking the stack */
}
}
extern int sysctl_perf_event_paranoid;

21
include/uapi/linux/bpf.h
View File

@ -83,6 +83,7 @@ enum bpf_map_type {
BPF_MAP_TYPE_PERF_EVENT_ARRAY,
BPF_MAP_TYPE_PERCPU_HASH,
BPF_MAP_TYPE_PERCPU_ARRAY,
BPF_MAP_TYPE_STACK_TRACE,
};
enum bpf_prog_type {
@ -272,6 +273,20 @@ enum bpf_func_id {
*/
BPF_FUNC_perf_event_output,
BPF_FUNC_skb_load_bytes,
/**
* bpf_get_stackid(ctx, map, flags) - walk user or kernel stack and return id
* @ctx: struct pt_regs*
* @map: pointer to stack_trace map
* @flags: bits 0-7 - numer of stack frames to skip
* bit 8 - collect user stack instead of kernel
* bit 9 - compare stacks by hash only
* bit 10 - if two different stacks hash into the same stackid
* discard old
* other bits - reserved
* Return: >= 0 stackid on success or negative error
*/
BPF_FUNC_get_stackid,
__BPF_FUNC_MAX_ID,
};
@ -294,6 +309,12 @@ enum bpf_func_id {
/* BPF_FUNC_skb_set_tunnel_key and BPF_FUNC_skb_get_tunnel_key flags. */
#define BPF_F_TUNINFO_IPV6 (1ULL << 0)
/* BPF_FUNC_get_stackid flags. */
#define BPF_F_SKIP_FIELD_MASK 0xffULL
#define BPF_F_USER_STACK (1ULL << 8)
#define BPF_F_FAST_STACK_CMP (1ULL << 9)
#define BPF_F_REUSE_STACKID (1ULL << 10)
/* user accessible mirror of in-kernel sk_buff.
* new fields can only be added to the end of this structure
*/

3
kernel/bpf/Makefile
View File

@ -2,3 +2,6 @@ obj-y := core.o
obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o
obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o
ifeq ($(CONFIG_PERF_EVENTS),y)
obj-$(CONFIG_BPF_SYSCALL) += stackmap.o
endif

237
kernel/bpf/stackmap.c Normal file
View File

@ -0,0 +1,237 @@
/* Copyright (c) 2016 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*/
#include <linux/bpf.h>
#include <linux/jhash.h>
#include <linux/filter.h>
#include <linux/vmalloc.h>
#include <linux/stacktrace.h>
#include <linux/perf_event.h>
struct stack_map_bucket {
struct rcu_head rcu;
u32 hash;
u32 nr;
u64 ip[];
};
struct bpf_stack_map {
struct bpf_map map;
u32 n_buckets;
struct stack_map_bucket __rcu *buckets[];
};
/* Called from syscall */
static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
{
u32 value_size = attr->value_size;
struct bpf_stack_map *smap;
u64 cost, n_buckets;
int err;
if (!capable(CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
/* check sanity of attributes */
if (attr->max_entries == 0 || attr->key_size != 4 ||
value_size < 8 || value_size % 8 ||
value_size / 8 > PERF_MAX_STACK_DEPTH)
return ERR_PTR(-EINVAL);
/* hash table size must be power of 2 */
n_buckets = roundup_pow_of_two(attr->max_entries);
cost = n_buckets * sizeof(struct stack_map_bucket *) + sizeof(*smap);
if (cost >= U32_MAX - PAGE_SIZE)
return ERR_PTR(-E2BIG);
smap = kzalloc(cost, GFP_USER | __GFP_NOWARN);
if (!smap) {
smap = vzalloc(cost);
if (!smap)
return ERR_PTR(-ENOMEM);
}
err = -E2BIG;
cost += n_buckets * (value_size + sizeof(struct stack_map_bucket));
if (cost >= U32_MAX - PAGE_SIZE)
goto free_smap;
smap->map.map_type = attr->map_type;
smap->map.key_size = attr->key_size;
smap->map.value_size = value_size;
smap->map.max_entries = attr->max_entries;
smap->n_buckets = n_buckets;
smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
err = get_callchain_buffers();
if (err)
goto free_smap;
return &smap->map;
free_smap:
kvfree(smap);
return ERR_PTR(err);
}
static u64 bpf_get_stackid(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5)
{
struct pt_regs *regs = (struct pt_regs *) (long) r1;
struct bpf_map *map = (struct bpf_map *) (long) r2;
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct perf_callchain_entry *trace;
struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
u32 max_depth = map->value_size / 8;
/* stack_map_alloc() checks that max_depth <= PERF_MAX_STACK_DEPTH */
u32 init_nr = PERF_MAX_STACK_DEPTH - max_depth;
u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
u32 hash, id, trace_nr, trace_len;
bool user = flags & BPF_F_USER_STACK;
bool kernel = !user;
u64 *ips;
if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
return -EINVAL;
trace = get_perf_callchain(regs, init_nr, kernel, user, false, false);
if (unlikely(!trace))
/* couldn't fetch the stack trace */
return -EFAULT;
/* get_perf_callchain() guarantees that trace->nr >= init_nr
* and trace-nr <= PERF_MAX_STACK_DEPTH, so trace_nr <= max_depth
*/
trace_nr = trace->nr - init_nr;
if (trace_nr <= skip)
/* skipping more than usable stack trace */
return -EFAULT;
trace_nr -= skip;
trace_len = trace_nr * sizeof(u64);
ips = trace->ip + skip + init_nr;
hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
id = hash & (smap->n_buckets - 1);
bucket = rcu_dereference(smap->buckets[id]);
if (bucket && bucket->hash == hash) {
if (flags & BPF_F_FAST_STACK_CMP)
return id;
if (bucket->nr == trace_nr &&
memcmp(bucket->ip, ips, trace_len) == 0)
return id;
}
/* this call stack is not in the map, try to add it */
if (bucket && !(flags & BPF_F_REUSE_STACKID))
return -EEXIST;
new_bucket = kmalloc(sizeof(struct stack_map_bucket) + map->value_size,
GFP_ATOMIC | __GFP_NOWARN);
if (unlikely(!new_bucket))
return -ENOMEM;
memcpy(new_bucket->ip, ips, trace_len);
memset(new_bucket->ip + trace_len / 8, 0, map->value_size - trace_len);
new_bucket->hash = hash;
new_bucket->nr = trace_nr;
old_bucket = xchg(&smap->buckets[id], new_bucket);
if (old_bucket)
kfree_rcu(old_bucket, rcu);
return id;
}
const struct bpf_func_proto bpf_get_stackid_proto = {
.func = bpf_get_stackid,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_CONST_MAP_PTR,
.arg3_type = ARG_ANYTHING,
};
/* Called from syscall or from eBPF program */
static void *stack_map_lookup_elem(struct bpf_map *map, void *key)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct stack_map_bucket *bucket;
u32 id = *(u32 *)key;
if (unlikely(id >= smap->n_buckets))
return NULL;
bucket = rcu_dereference(smap->buckets[id]);
return bucket ? bucket->ip : NULL;
}
static int stack_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
{
return -EINVAL;
}
static int stack_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 map_flags)
{
return -EINVAL;
}
/* Called from syscall or from eBPF program */
static int stack_map_delete_elem(struct bpf_map *map, void *key)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
struct stack_map_bucket *old_bucket;
u32 id = *(u32 *)key;
if (unlikely(id >= smap->n_buckets))
return -E2BIG;
old_bucket = xchg(&smap->buckets[id], NULL);
if (old_bucket) {
kfree_rcu(old_bucket, rcu);
return 0;
} else {
return -ENOENT;
}
}
/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
static void stack_map_free(struct bpf_map *map)
{
struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
int i;
synchronize_rcu();
for (i = 0; i < smap->n_buckets; i++)
if (smap->buckets[i])
kfree_rcu(smap->buckets[i], rcu);
kvfree(smap);
put_callchain_buffers();
}
static const struct bpf_map_ops stack_map_ops = {
.map_alloc = stack_map_alloc,
.map_free = stack_map_free,
.map_get_next_key = stack_map_get_next_key,
.map_lookup_elem = stack_map_lookup_elem,
.map_update_elem = stack_map_update_elem,
.map_delete_elem = stack_map_delete_elem,
};
static struct bpf_map_type_list stack_map_type __read_mostly = {
.ops = &stack_map_ops,
.type = BPF_MAP_TYPE_STACK_TRACE,
};
static int __init register_stack_map(void)
{
bpf_register_map_type(&stack_map_type);
return 0;
}
late_initcall(register_stack_map);

6
kernel/bpf/verifier.c
View File

@ -246,6 +246,7 @@ static const struct {
{BPF_MAP_TYPE_PROG_ARRAY, BPF_FUNC_tail_call},
{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_read},
{BPF_MAP_TYPE_PERF_EVENT_ARRAY, BPF_FUNC_perf_event_output},
{BPF_MAP_TYPE_STACK_TRACE, BPF_FUNC_get_stackid},
};
static void print_verifier_state(struct verifier_env *env)
@ -911,8 +912,11 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
* don't allow any other map type to be passed into
* the special func;
*/
if (bool_func && bool_map != bool_func)
if (bool_func && bool_map != bool_func) {
verbose("cannot pass map_type %d into func %d\n",
map->map_type, func_id);
return -EINVAL;
}
}
return 0;

32
kernel/events/callchain.c
View File

@ -159,15 +159,24 @@ put_callchain_entry(int rctx)
struct perf_callchain_entry *
perf_callchain(struct perf_event *event, struct pt_regs *regs)
{
int rctx;
struct perf_callchain_entry *entry;
int kernel = !event->attr.exclude_callchain_kernel;
int user = !event->attr.exclude_callchain_user;
bool kernel = !event->attr.exclude_callchain_kernel;
bool user = !event->attr.exclude_callchain_user;
/* Disallow cross-task user callchains. */
bool crosstask = event->ctx->task && event->ctx->task != current;
if (!kernel && !user)
return NULL;
return get_perf_callchain(regs, 0, kernel, user, crosstask, true);
}
struct perf_callchain_entry *
get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
bool crosstask, bool add_mark)
{
struct perf_callchain_entry *entry;
int rctx;
entry = get_callchain_entry(&rctx);
if (rctx == -1)
return NULL;
@ -175,10 +184,11 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs)
if (!entry)
goto exit_put;
entry->nr = 0;
entry->nr = init_nr;
if (kernel && !user_mode(regs)) {
perf_callchain_store(entry, PERF_CONTEXT_KERNEL);
if (add_mark)
perf_callchain_store(entry, PERF_CONTEXT_KERNEL);
perf_callchain_kernel(entry, regs);
}
@ -191,13 +201,11 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs)
}
if (regs) {
/*
* Disallow cross-task user callchains.
*/
if (event->ctx->task && event->ctx->task != current)
if (crosstask)
goto exit_put;
perf_callchain_store(entry, PERF_CONTEXT_USER);
if (add_mark)
perf_callchain_store(entry, PERF_CONTEXT_USER);
perf_callchain_user(entry, regs);
}
}

2
kernel/events/internal.h
View File

@ -182,8 +182,6 @@ DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user)
/* Callchain handling */
extern struct perf_callchain_entry *
perf_callchain(struct perf_event *event, struct pt_regs *regs);
extern int get_callchain_buffers(void);
extern void put_callchain_buffers(void);
static inline int get_recursion_context(int *recursion)
{

2
kernel/trace/bpf_trace.c
View File

@ -299,6 +299,8 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
return &bpf_perf_event_read_proto;
case BPF_FUNC_perf_event_output:
return &bpf_perf_event_output_proto;
case BPF_FUNC_get_stackid:
return &bpf_get_stackid_proto;
default:
return NULL;
}

4
samples/bpf/Makefile
View File

@ -16,6 +16,7 @@ hostprogs-y += tracex5
hostprogs-y += tracex6
hostprogs-y += trace_output
hostprogs-y += lathist
hostprogs-y += offwaketime
test_verifier-objs := test_verifier.o libbpf.o
test_maps-objs := test_maps.o libbpf.o
@ -32,6 +33,7 @@ tracex5-objs := bpf_load.o libbpf.o tracex5_user.o
tracex6-objs := bpf_load.o libbpf.o tracex6_user.o
trace_output-objs := bpf_load.o libbpf.o trace_output_user.o
lathist-objs := bpf_load.o libbpf.o lathist_user.o
offwaketime-objs := bpf_load.o libbpf.o offwaketime_user.o
# Tell kbuild to always build the programs
always := $(hostprogs-y)
@ -47,6 +49,7 @@ always += tracex6_kern.o
always += trace_output_kern.o
always += tcbpf1_kern.o
always += lathist_kern.o
always += offwaketime_kern.o
HOSTCFLAGS += -I$(objtree)/usr/include
@ -63,6 +66,7 @@ HOSTLOADLIBES_tracex5 += -lelf
HOSTLOADLIBES_tracex6 += -lelf
HOSTLOADLIBES_trace_output += -lelf -lrt
HOSTLOADLIBES_lathist += -lelf
HOSTLOADLIBES_offwaketime += -lelf
# point this to your LLVM backend with bpf support
LLC=$(srctree)/tools/bpf/llvm/bld/Debug+Asserts/bin/llc

2
samples/bpf/bpf_helpers.h
View File

@ -39,6 +39,8 @@ static int (*bpf_redirect)(int ifindex, int flags) =
(void *) BPF_FUNC_redirect;
static int (*bpf_perf_event_output)(void *ctx, void *map, int index, void *data, int size) =
(void *) BPF_FUNC_perf_event_output;
static int (*bpf_get_stackid)(void *ctx, void *map, int flags) =
(void *) BPF_FUNC_get_stackid;
/* llvm builtin functions that eBPF C program may use to
* emit BPF_LD_ABS and BPF_LD_IND instructions

131
samples/bpf/offwaketime_kern.c Normal file
View File

@ -0,0 +1,131 @@
/* Copyright (c) 2016 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*/
#include <uapi/linux/bpf.h>
#include "bpf_helpers.h"
#include <uapi/linux/ptrace.h>
#include <uapi/linux/perf_event.h>
#include <linux/version.h>
#include <linux/sched.h>
#define _(P) ({typeof(P) val = 0; bpf_probe_read(&val, sizeof(val), &P); val;})
#define MINBLOCK_US 1
struct key_t {
char waker[TASK_COMM_LEN];
char target[TASK_COMM_LEN];
u32 wret;
u32 tret;
};
struct bpf_map_def SEC("maps") counts = {
.type = BPF_MAP_TYPE_HASH,
.key_size = sizeof(struct key_t),
.value_size = sizeof(u64),
.max_entries = 10000,
};
struct bpf_map_def SEC("maps") start = {
.type = BPF_MAP_TYPE_HASH,
.key_size = sizeof(u32),
.value_size = sizeof(u64),
.max_entries = 10000,
};
struct wokeby_t {
char name[TASK_COMM_LEN];
u32 ret;
};
struct bpf_map_def SEC("maps") wokeby = {
.type = BPF_MAP_TYPE_HASH,
.key_size = sizeof(u32),
.value_size = sizeof(struct wokeby_t),
.max_entries = 10000,
};
struct bpf_map_def SEC("maps") stackmap = {
.type = BPF_MAP_TYPE_STACK_TRACE,
.key_size = sizeof(u32),
.value_size = PERF_MAX_STACK_DEPTH * sizeof(u64),
.max_entries = 10000,
};
#define STACKID_FLAGS (0 | BPF_F_FAST_STACK_CMP)
SEC("kprobe/try_to_wake_up")
int waker(struct pt_regs *ctx)
{
struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
struct wokeby_t woke = {};
u32 pid;
pid = _(p->pid);
bpf_get_current_comm(&woke.name, sizeof(woke.name));
woke.ret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
bpf_map_update_elem(&wokeby, &pid, &woke, BPF_ANY);
return 0;
}
static inline int update_counts(struct pt_regs *ctx, u32 pid, u64 delta)
{
struct key_t key = {};
struct wokeby_t *woke;
u64 zero = 0, *val;
bpf_get_current_comm(&key.target, sizeof(key.target));
key.tret = bpf_get_stackid(ctx, &stackmap, STACKID_FLAGS);
woke = bpf_map_lookup_elem(&wokeby, &pid);
if (woke) {
key.wret = woke->ret;
__builtin_memcpy(&key.waker, woke->name, TASK_COMM_LEN);
bpf_map_delete_elem(&wokeby, &pid);
}
val = bpf_map_lookup_elem(&counts, &key);
if (!val) {
bpf_map_update_elem(&counts, &key, &zero, BPF_NOEXIST);
val = bpf_map_lookup_elem(&counts, &key);
if (!val)
return 0;
}
(*val) += delta;
return 0;
}
SEC("kprobe/finish_task_switch")
int oncpu(struct pt_regs *ctx)
{
struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
u64 delta, ts, *tsp;
u32 pid;
/* record previous thread sleep time */
pid = _(p->pid);
ts = bpf_ktime_get_ns();
bpf_map_update_elem(&start, &pid, &ts, BPF_ANY);
/* calculate current thread's delta time */
pid = bpf_get_current_pid_tgid();
tsp = bpf_map_lookup_elem(&start, &pid);
if (!tsp)
/* missed start or filtered */
return 0;
delta = bpf_ktime_get_ns() - *tsp;
bpf_map_delete_elem(&start, &pid);
delta = delta / 1000;
if (delta < MINBLOCK_US)
return 0;
return update_counts(ctx, pid, delta);
}
char _license[] SEC("license") = "GPL";
u32 _version SEC("version") = LINUX_VERSION_CODE;

185
samples/bpf/offwaketime_user.c Normal file
View File

@ -0,0 +1,185 @@
/* Copyright (c) 2016 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <linux/bpf.h>
#include <string.h>
#include <linux/perf_event.h>
#include <errno.h>
#include <assert.h>
#include <stdbool.h>
#include <sys/resource.h>
#include "libbpf.h"
#include "bpf_load.h"
#define MAX_SYMS 300000
#define PRINT_RAW_ADDR 0
static struct ksym {
long addr;
char *name;
} syms[MAX_SYMS];
static int sym_cnt;
static int ksym_cmp(const void *p1, const void *p2)
{
return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
}
static int load_kallsyms(void)
{
FILE *f = fopen("/proc/kallsyms", "r");
char func[256], buf[256];
char symbol;
void *addr;
int i = 0;
if (!f)
return -ENOENT;
while (!feof(f)) {
if (!fgets(buf, sizeof(buf), f))
break;
if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
break;
if (!addr)
continue;
syms[i].addr = (long) addr;
syms[i].name = strdup(func);
i++;
}
sym_cnt = i;
qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
return 0;
}
static void *search(long key)
{
int start = 0, end = sym_cnt;
int result;
while (start < end) {
size_t mid = start + (end - start) / 2;
result = key - syms[mid].addr;
if (result < 0)
end = mid;
else if (result > 0)
start = mid + 1;
else
return &syms[mid];
}
if (start >= 1 && syms[start - 1].addr < key &&
key < syms[start].addr)
/* valid ksym */
return &syms[start - 1];
/* out of range. return _stext */
return &syms[0];
}
static void print_ksym(__u64 addr)
{
struct ksym *sym;
if (!addr)
return;
sym = search(addr);
if (PRINT_RAW_ADDR)
printf("%s/%llx;", sym->name, addr);
else
printf("%s;", sym->name);
}
#define TASK_COMM_LEN 16
struct key_t {
char waker[TASK_COMM_LEN];
char target[TASK_COMM_LEN];
__u32 wret;
__u32 tret;
};
static void print_stack(struct key_t *key, __u64 count)
{
__u64 ip[PERF_MAX_STACK_DEPTH] = {};
static bool warned;
int i;
printf("%s;", key->target);
if (bpf_lookup_elem(map_fd[3], &key->tret, ip) != 0) {
printf("---;");
} else {
for (i = PERF_MAX_STACK_DEPTH - 1; i >= 0; i--)
print_ksym(ip[i]);
}
printf("-;");
if (bpf_lookup_elem(map_fd[3], &key->wret, ip) != 0) {
printf("---;");
} else {
for (i = 0; i < PERF_MAX_STACK_DEPTH; i++)
print_ksym(ip[i]);
}
printf(";%s %lld\n", key->waker, count);
if ((key->tret == -EEXIST || key->wret == -EEXIST) && !warned) {
printf("stackmap collisions seen. Consider increasing size\n");
warned = true;
} else if (((int)(key->tret) < 0 || (int)(key->wret) < 0)) {
printf("err stackid %d %d\n", key->tret, key->wret);
}
}
static void print_stacks(int fd)
{
struct key_t key = {}, next_key;
__u64 value;
while (bpf_get_next_key(fd, &key, &next_key) == 0) {
bpf_lookup_elem(fd, &next_key, &value);
print_stack(&next_key, value);
key = next_key;
}
}
static void int_exit(int sig)
{
print_stacks(map_fd[0]);
exit(0);
}
int main(int argc, char **argv)
{
struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
char filename[256];
int delay = 1;
snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
setrlimit(RLIMIT_MEMLOCK, &r);
signal(SIGINT, int_exit);
if (load_kallsyms()) {
printf("failed to process /proc/kallsyms\n");
return 2;
}
if (load_bpf_file(filename)) {
printf("%s", bpf_log_buf);
return 1;
}
if (argc > 1)
delay = atoi(argv[1]);
sleep(delay);
print_stacks(map_fd[0]);
return 0;
}