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Date: Mon, 9 Dec 2019 17:14:30 -0800
From: Andrii Nakryiko <andriin@...com>
To: <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
<daniel@...earbox.net>
CC: <andrii.nakryiko@...il.com>, <kernel-team@...com>,
Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf-next 07/15] libbpf: refactor global data map initialization
Refactor global data map initialization to use anonymous mmap()-ed memory
instead of malloc()-ed one. This allows to do a transparent re-mmap()-ing of
already existing memory address to point to BPF map's memory after
bpf_object__load() step (done in follow up patch). This choreographed setup
allows to have a nice and unsurprising way to pre-initialize read-only (and
r/w as well) maps by user and after BPF map creation keep working with
mmap()-ed contents of this map. All in a way that doesn't require user code to
update any pointers: the illusion of working with memory contents is preserved
before and after actual BPF map instantiation.
Selftests and runqslower example demonstrate this feature in follow up patches.
Signed-off-by: Andrii Nakryiko <andriin@...com>
---
tools/lib/bpf/libbpf.c | 92 +++++++++++++++++++++++++-----------------
1 file changed, 55 insertions(+), 37 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index f13752c4d271..ff00a767adfb 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -221,16 +221,12 @@ struct bpf_map {
void *priv;
bpf_map_clear_priv_t clear_priv;
enum libbpf_map_type libbpf_type;
+ void *mmaped;
char *pin_path;
bool pinned;
bool reused;
};
-struct bpf_secdata {
- void *rodata;
- void *data;
-};
-
static LIST_HEAD(bpf_objects_list);
struct bpf_object {
@@ -243,7 +239,6 @@ struct bpf_object {
struct bpf_map *maps;
size_t nr_maps;
size_t maps_cap;
- struct bpf_secdata sections;
bool loaded;
bool has_pseudo_calls;
@@ -828,13 +823,24 @@ static struct bpf_map *bpf_object__add_map(struct bpf_object *obj)
return &obj->maps[obj->nr_maps++];
}
+static size_t bpf_map_mmap_sz(const struct bpf_map *map)
+{
+ long page_sz = sysconf(_SC_PAGE_SIZE);
+ size_t map_sz;
+
+ map_sz = roundup(map->def.value_size, 8) * map->def.max_entries;
+ map_sz = roundup(map_sz, page_sz);
+ return map_sz;
+}
+
static int
bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,
- int sec_idx, Elf_Data *data, void **data_buff)
+ int sec_idx, Elf_Data *data)
{
char map_name[BPF_OBJ_NAME_LEN];
struct bpf_map_def *def;
struct bpf_map *map;
+ int err;
map = bpf_object__add_map(obj);
if (IS_ERR(map))
@@ -862,16 +868,20 @@ bpf_object__init_internal_map(struct bpf_object *obj, enum libbpf_map_type type,
pr_debug("map '%s' (global data): at sec_idx %d, offset %zu, flags %x.\n",
map_name, map->sec_idx, map->sec_offset, def->map_flags);
- if (data_buff) {
- *data_buff = malloc(data->d_size);
- if (!*data_buff) {
- zfree(&map->name);
- pr_warn("failed to alloc map content buffer\n");
- return -ENOMEM;
- }
- memcpy(*data_buff, data->d_buf, data->d_size);
+ map->mmaped = mmap(NULL, bpf_map_mmap_sz(map), PROT_READ | PROT_WRITE,
+ MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+ if (map->mmaped == MAP_FAILED) {
+ err = -errno;
+ map->mmaped = NULL;
+ pr_warn("failed to alloc map '%s' content buffer: %d\n",
+ map->name, err);
+ zfree(&map->name);
+ return err;
}
+ if (type != LIBBPF_MAP_BSS)
+ memcpy(map->mmaped, data->d_buf, data->d_size);
+
pr_debug("map %td is \"%s\"\n", map - obj->maps, map->name);
return 0;
}
@@ -886,23 +896,21 @@ static int bpf_object__init_global_data_maps(struct bpf_object *obj)
if (obj->efile.data_shndx >= 0) {
err = bpf_object__init_internal_map(obj, LIBBPF_MAP_DATA,
obj->efile.data_shndx,
- obj->efile.data,
- &obj->sections.data);
+ obj->efile.data);
if (err)
return err;
}
if (obj->efile.rodata_shndx >= 0) {
err = bpf_object__init_internal_map(obj, LIBBPF_MAP_RODATA,
obj->efile.rodata_shndx,
- obj->efile.rodata,
- &obj->sections.rodata);
+ obj->efile.rodata);
if (err)
return err;
}
if (obj->efile.bss_shndx >= 0) {
err = bpf_object__init_internal_map(obj, LIBBPF_MAP_BSS,
obj->efile.bss_shndx,
- obj->efile.bss, NULL);
+ obj->efile.bss);
if (err)
return err;
}
@@ -2291,27 +2299,32 @@ bpf_object__populate_internal_map(struct bpf_object *obj, struct bpf_map *map)
{
char *cp, errmsg[STRERR_BUFSIZE];
int err, zero = 0;
- __u8 *data;
/* Nothing to do here since kernel already zero-initializes .bss map. */
if (map->libbpf_type == LIBBPF_MAP_BSS)
return 0;
- data = map->libbpf_type == LIBBPF_MAP_DATA ?
- obj->sections.data : obj->sections.rodata;
+ err = bpf_map_update_elem(map->fd, &zero, map->mmaped, 0);
+ if (err) {
+ err = -errno;
+ cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
+ pr_warn("Error setting initial map(%s) contents: %s\n",
+ map->name, cp);
+ return err;
+ }
- err = bpf_map_update_elem(map->fd, &zero, data, 0);
/* Freeze .rodata map as read-only from syscall side. */
- if (!err && map->libbpf_type == LIBBPF_MAP_RODATA) {
+ if (map->libbpf_type == LIBBPF_MAP_RODATA) {
err = bpf_map_freeze(map->fd);
if (err) {
- cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
+ err = -errno;
+ cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
pr_warn("Error freezing map(%s) as read-only: %s\n",
map->name, cp);
- err = 0;
+ return err;
}
}
- return err;
+ return 0;
}
static int
@@ -4682,17 +4695,22 @@ void bpf_object__close(struct bpf_object *obj)
btf_ext__free(obj->btf_ext);
for (i = 0; i < obj->nr_maps; i++) {
- zfree(&obj->maps[i].name);
- zfree(&obj->maps[i].pin_path);
- if (obj->maps[i].clear_priv)
- obj->maps[i].clear_priv(&obj->maps[i],
- obj->maps[i].priv);
- obj->maps[i].priv = NULL;
- obj->maps[i].clear_priv = NULL;
+ struct bpf_map *map = &obj->maps[i];
+
+ if (map->clear_priv)
+ map->clear_priv(map, map->priv);
+ map->priv = NULL;
+ map->clear_priv = NULL;
+
+ if (map->mmaped) {
+ munmap(map->mmaped, bpf_map_mmap_sz(map));
+ map->mmaped = NULL;
+ }
+
+ zfree(&map->name);
+ zfree(&map->pin_path);
}
- zfree(&obj->sections.rodata);
- zfree(&obj->sections.data);
zfree(&obj->maps);
obj->nr_maps = 0;
--
2.17.1
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