From: Mykyta Yatsenko <yatsenko@xxxxxxxx>
To better verify some complex BPF programs we'd like to preset global
variables.
This patch introduces CLI argument `--set-global-vars` to veristat, that
allows presetting values to global variables defined in BPF program. For
example:
prog.c:
```
enum Enum { ELEMENT1 = 0, ELEMENT2 = 5 };
const volatile __s64 a = 5;
const volatile __u8 b = 5;
const volatile enum Enum c = ELEMENT2;
const volatile bool d = false;
char arr[4] = {0};
SEC("tp_btf/sched_switch")
int BPF_PROG(...)
{
bpf_printk("%c\n", arr[a]);
bpf_printk("%c\n", arr[b]);
bpf_printk("%c\n", arr[c]);
bpf_printk("%c\n", arr[d]);
return 0;
}
```
By default verification of the program fails:
```
./veristat prog.bpf.o
```
By presetting global variables, we can make verification pass:
```
./veristat wq.bpf.o --set-global-vars "a = 0; b = 1; c = 2; d = 3;"
```
Signed-off-by: Mykyta Yatsenko <yatsenko@xxxxxxxx>
---
tools/testing/selftests/bpf/veristat.c | 189 +++++++++++++++++++++++++
1 file changed, 189 insertions(+)
diff --git a/tools/testing/selftests/bpf/veristat.c b/tools/testing/selftests/bpf/veristat.c
index 06af5029885b..65bb8a773d23 100644
--- a/tools/testing/selftests/bpf/veristat.c
+++ b/tools/testing/selftests/bpf/veristat.c
@@ -154,6 +154,11 @@ struct filter {
bool abs;
};
+struct var_preset {
+ char *name;
+ long long value;
+};
+
static struct env {
char **filenames;
int filename_cnt;
@@ -195,6 +200,8 @@ static struct env {
int progs_processed;
int progs_skipped;
int top_src_lines;
+ struct var_preset *presets;
+ int npresets;
} env;
static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
@@ -246,12 +253,14 @@ static const struct argp_option opts[] = {
{ "test-reg-invariants", 'r', NULL, 0,
"Force BPF verifier failure on register invariant violation (BPF_F_TEST_REG_INVARIANTS program flag)" },
{ "top-src-lines", 'S', "N", 0, "Emit N most frequent source code lines" },
+ { "set-global-vars", 'g', "GLOBALS", 0, "Set global variables provided in the expression, for example \"var1 = 1; var2 = 2\"" },
{},
};
static int parse_stats(const char *stats_str, struct stat_specs *specs);
static int append_filter(struct filter **filters, int *cnt, const char *str);
static int append_filter_file(const char *path);
+static int parse_var_presets(char *expr, struct var_preset *presets, int capacity, int *size);
static error_t parse_arg(int key, char *arg, struct argp_state *state)
{
@@ -363,6 +372,17 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
return -ENOMEM;
env.filename_cnt++;
break;
+ case 'g': {
+ char *expr = strdup(arg);
+
+ env.presets = calloc(64, sizeof(*env.presets));
+ if (parse_var_presets(expr, env.presets, 64, &env.npresets)) {
+ fprintf(stderr, "Could not parse global variables preset: %s\n", arg);
+ argp_usage(state);
+ }
+ free(expr);
+ break;
+ }
default:
return ARGP_ERR_UNKNOWN;
}
@@ -1292,6 +1312,169 @@ static int process_prog(const char *filename, struct bpf_object *obj, struct bpf
return 0;
};
+static int parse_var_presets(char *expr, struct var_preset *presets, int capacity, int *size)
+{
+ char *state;
+ char *next;
+ int i = 0;
+
+ while ((next = strtok_r(i ? NULL : expr, ";", &state))) {
+ char *eq_ptr = strchr(next, '=');
+ char *name_ptr = next;
+ char *name_end = eq_ptr - 1;
+ char *val_ptr = eq_ptr + 1;
+
+ if (!eq_ptr)
+ continue;
+
+ if (i >= capacity) {
+ fprintf(stderr, "Too many global variable presets\n");
+ return -EINVAL;
+ }
+ while (isspace(*name_ptr))
+ ++name_ptr;
+ while (isspace(*name_end))
+ --name_end;
+
+ *(name_end + 1) = '\0';
+ presets[i].name = strdup(name_ptr);
+ errno = 0;
+ presets[i].value = strtoll(val_ptr, NULL, 10);
+ if (errno == ERANGE) {
+ errno = 0;
+ presets[i].value = strtoull(val_ptr, NULL, 10);
+ }
+ if (errno) {
+ fprintf(stderr, "Could not parse integer value %s\n", val_ptr);
+ return -EINVAL;
+ }
+ ++i;
+ }
+ *size = i;
+ return 0;
+}
+
+static bool is_signed_type(const struct btf_type *type)
+{
+ if (btf_is_int(type))
+ return btf_int_encoding(type) & BTF_INT_SIGNED;
+ return true;
+}
+
+static const struct btf_type *var_base_type(const struct btf *btf, const struct btf_type *type)
+{
+ switch (btf_kind(type)) {
+ case BTF_KIND_VAR:
+ case BTF_KIND_TYPE_TAG:
+ case BTF_KIND_CONST:
+ case BTF_KIND_VOLATILE:
+ case BTF_KIND_RESTRICT:
+ case BTF_KIND_TYPEDEF:
+ case BTF_KIND_DECL_TAG:
+ return var_base_type(btf, btf__type_by_id(btf, type->type));
+ }
+ return type;
+}
+
+static bool is_preset_supported(const struct btf_type *t)
+{
+ return btf_is_int(t) || btf_is_enum(t) || btf_is_enum64(t);
+}
+
+static int set_global_var(struct bpf_object *obj, struct btf *btf, const struct btf_type *t,
+ struct bpf_map *map, struct btf_var_secinfo *sinfo, long long new_val)
+{
+ const struct btf_type *base_type;
+ void *ptr;
+ size_t size;
+
+ base_type = var_base_type(btf, t);
+ if (!is_preset_supported(base_type)) {
+ fprintf(stderr, "Setting global variable for btf kind %d is not supported\n",
+ btf_kind(base_type));
+ return -EINVAL;
+ }
+
+ /* Check if value fits into the target variable size */
+ if (sinfo->size < sizeof(new_val)) {
+ bool is_signed = is_signed_type(base_type);
+ __u32 unsigned_bits = sinfo->size * 8 - (is_signed ? 1 : 0);
+ long long max_val = 1ll << unsigned_bits;
+
+ if (new_val >= max_val || new_val < -max_val) {
+ fprintf(stderr,
+ "Variable %s value %lld is out of range [%lld; %lld]\n",
+ btf__name_by_offset(btf, t->name_off), new_val,
+ is_signed ? -max_val : 0, max_val - 1);
+ return -EINVAL;
+ }
+ }
+
+ ptr = (void *)bpf_map__initial_value(map, &size);
+ if (!ptr || (sinfo->offset + sinfo->size > size))
+ return -EINVAL;
+
+ memcpy(ptr + sinfo->offset, &new_val, sinfo->size);
+ return 0;
+}
+
+static int set_global_vars(struct bpf_object *obj, struct var_preset *presets, int npresets)
+{
+ struct btf_var_secinfo *sinfo;
+ const char *sec_name;
+ const struct btf_type *type;
+ struct bpf_map *map;
+ struct btf *btf;
+ int i, j, k, n, cnt, err, preset_cnt = 0;
+
+ if (npresets == 0)
+ return 0;
+
+ btf = bpf_object__btf(obj);
+ if (!btf)
+ return -EINVAL;
+
+ cnt = btf__type_cnt(btf);
+ for (i = 0; i != cnt; ++i) {
+ type = btf__type_by_id(btf, i);
+
+ if (!btf_is_datasec(type))
+ continue;
+
+ sinfo = btf_var_secinfos(type);
+ sec_name = btf__name_by_offset(btf, type->name_off);
+ map = bpf_object__find_map_by_name(obj, sec_name);
+ if (!map)
+ continue;
+
+ n = btf_vlen(type);
+ for (j = 0; j < n; ++j, ++sinfo) {
+ const struct btf_type *var_type = btf__type_by_id(btf, sinfo->type);
+ const char *var_name = btf__name_by_offset(btf, var_type->name_off);
+
+ if (!btf_is_var(var_type))
+ continue;
+
+ for (k = 0; k < npresets; ++k) {
+ if (strcmp(var_name, presets[k].name) != 0)
+ continue;
+
+ err = set_global_var(obj, btf, var_type, map, sinfo,
+ presets[k].value);
+ if (err)
+ return err;
+
+ preset_cnt++;
+ break;
+ }
+ }
+ }
+ if (preset_cnt != npresets)
+ fprintf(stderr, "Some global variable presets have not been applied\n");
+
+ return 0;
+}
+
static int process_obj(const char *filename)
{
const char *base_filename = basename(strdupa(filename));
@@ -1338,6 +1521,12 @@ static int process_obj(const char *filename)
prog_cnt++;
}
+ err = set_global_vars(obj, env.presets, env.npresets);
+ if (err) {
+ fprintf(stderr, "Failed to set global variables\n");
+ goto cleanup;
+ }
+
if (prog_cnt == 1) {
prog = bpf_object__next_program(obj, NULL);
bpf_program__set_autoload(prog, true);
--
2.48.1
