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bpf: provide a generic macro for percpu values for selftests

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To overcome bugs as described and fixed in 89087c456f ("bpf: Fix
values type used in test_maps"), provide a generic BPF_DECLARE_PERCPU()
and bpf_percpu() accessor macro for all percpu map values used in
tests.

Declaring variables works as follows (also works for structs):

  BPF_DECLARE_PERCPU(uint32_t, my_value);

They can then be accessed normally as uint32_t type through:

  bpf_percpu(my_value, <cpu_nr>)

For example:

  bpf_percpu(my_value, 0)++;

Implicitly, we make sure that the passed type is allocated and aligned
by gcc at least on a 8-byte boundary, so that it works together with
the map lookup/update syscall for percpu maps. We use it as a usage
example in test_maps, so that others are free to adapt this into their
code when necessary.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2017-04-27 01:39:35 +02:00 committed by David S. Miller
parent 43bcf707cc
commit f3515b5d0b
2 changed files with 27 additions and 17 deletions
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7
tools/testing/selftests/bpf/bpf_util.h
View File

@ -54,4 +54,11 @@ static inline unsigned int bpf_num_possible_cpus(void)
return possible_cpus;
}
#define __bpf_percpu_val_align __attribute__((__aligned__(8)))
#define BPF_DECLARE_PERCPU(type, name) \
struct { type v; /* padding */ } __bpf_percpu_val_align \
name[bpf_num_possible_cpus()]
#define bpf_percpu(name, cpu) name[(cpu)].v
#endif /* __BPF_UTIL__ */

37
tools/testing/selftests/bpf/test_maps.c
View File

@ -137,20 +137,20 @@ static void test_hashmap_sizes(int task, void *data)
static void test_hashmap_percpu(int task, void *data)
{
unsigned int nr_cpus = bpf_num_possible_cpus();
long long value[nr_cpus];
BPF_DECLARE_PERCPU(long, value);
long long key, next_key, first_key;
int expected_key_mask = 0;
int fd, i;
fd = bpf_create_map(BPF_MAP_TYPE_PERCPU_HASH, sizeof(key),
sizeof(value[0]), 2, map_flags);
sizeof(bpf_percpu(value, 0)), 2, map_flags);
if (fd < 0) {
printf("Failed to create hashmap '%s'!\n", strerror(errno));
exit(1);
}
for (i = 0; i < nr_cpus; i++)
value[i] = i + 100;
bpf_percpu(value, i) = i + 100;
key = 1;
/* Insert key=1 element. */
@ -170,8 +170,9 @@ static void test_hashmap_percpu(int task, void *data)
/* Check that key=1 can be found. Value could be 0 if the lookup
* was run from a different CPU.
*/
value[0] = 1;
assert(bpf_map_lookup_elem(fd, &key, value) == 0 && value[0] == 100);
bpf_percpu(value, 0) = 1;
assert(bpf_map_lookup_elem(fd, &key, value) == 0 &&
bpf_percpu(value, 0) == 100);
key = 2;
/* Check that key=2 is not found. */
@ -211,7 +212,7 @@ static void test_hashmap_percpu(int task, void *data)
assert(bpf_map_lookup_elem(fd, &next_key, value) == 0);
for (i = 0; i < nr_cpus; i++)
assert(value[i] == i + 100);
assert(bpf_percpu(value, i) == i + 100);
key = next_key;
}
@ -296,34 +297,36 @@ static void test_arraymap(int task, void *data)
static void test_arraymap_percpu(int task, void *data)
{
unsigned int nr_cpus = bpf_num_possible_cpus();
BPF_DECLARE_PERCPU(long, values);
int key, next_key, fd, i;
long long values[nr_cpus];
fd = bpf_create_map(BPF_MAP_TYPE_PERCPU_ARRAY, sizeof(key),
sizeof(values[0]), 2, 0);
sizeof(bpf_percpu(values, 0)), 2, 0);
if (fd < 0) {
printf("Failed to create arraymap '%s'!\n", strerror(errno));
exit(1);
}
for (i = 0; i < nr_cpus; i++)
values[i] = i + 100;
bpf_percpu(values, i) = i + 100;
key = 1;
/* Insert key=1 element. */
assert(bpf_map_update_elem(fd, &key, values, BPF_ANY) == 0);
values[0] = 0;
bpf_percpu(values, 0) = 0;
assert(bpf_map_update_elem(fd, &key, values, BPF_NOEXIST) == -1 &&
errno == EEXIST);
/* Check that key=1 can be found. */
assert(bpf_map_lookup_elem(fd, &key, values) == 0 && values[0] == 100);
assert(bpf_map_lookup_elem(fd, &key, values) == 0 &&
bpf_percpu(values, 0) == 100);
key = 0;
/* Check that key=0 is also found and zero initialized. */
assert(bpf_map_lookup_elem(fd, &key, values) == 0 &&
values[0] == 0 && values[nr_cpus - 1] == 0);
bpf_percpu(values, 0) == 0 &&
bpf_percpu(values, nr_cpus - 1) == 0);
/* Check that key=2 cannot be inserted due to max_entries limit. */
key = 2;
@ -353,15 +356,15 @@ static void test_arraymap_percpu(int task, void *data)
static void test_arraymap_percpu_many_keys(void)
{
unsigned int nr_cpus = bpf_num_possible_cpus();
BPF_DECLARE_PERCPU(long, values);
/* nr_keys is not too large otherwise the test stresses percpu
* allocator more than anything else
*/
unsigned int nr_keys = 2000;
long long values[nr_cpus];
int key, fd, i;
fd = bpf_create_map(BPF_MAP_TYPE_PERCPU_ARRAY, sizeof(key),
sizeof(values[0]), nr_keys, 0);
sizeof(bpf_percpu(values, 0)), nr_keys, 0);
if (fd < 0) {
printf("Failed to create per-cpu arraymap '%s'!\n",
strerror(errno));
@ -369,19 +372,19 @@ static void test_arraymap_percpu_many_keys(void)
}
for (i = 0; i < nr_cpus; i++)
values[i] = i + 10;
bpf_percpu(values, i) = i + 10;
for (key = 0; key < nr_keys; key++)
assert(bpf_map_update_elem(fd, &key, values, BPF_ANY) == 0);
for (key = 0; key < nr_keys; key++) {
for (i = 0; i < nr_cpus; i++)
values[i] = 0;
bpf_percpu(values, i) = 0;
assert(bpf_map_lookup_elem(fd, &key, values) == 0);
for (i = 0; i < nr_cpus; i++)
assert(values[i] == i + 10);
assert(bpf_percpu(values, i) == i + 10);
}
close(fd);