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` or `-G` 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 -G "a = 0" -G "b = 1" -G "c = 2" -G "d = 3"
```
Signed-off-by: Mykyta Yatsenko <yatsenko@xxxxxxxx>
---
tools/testing/selftests/bpf/veristat.c | 282 +++++++++++++++++++++++++
1 file changed, 282 insertions(+)
diff --git a/tools/testing/selftests/bpf/veristat.c b/tools/testing/selftests/bpf/veristat.c
index 06af5029885b..8a540c4b4bba 100644
--- a/tools/testing/selftests/bpf/veristat.c
+++ b/tools/testing/selftests/bpf/veristat.c
@@ -154,6 +154,16 @@ struct filter {
bool abs;
};
+struct var_preset {
+ char *name;
+ enum { INTEGRAL, NAME } type;
+ union {
+ long long ivalue;
+ char *svalue;
+ };
+ bool applied;
+};
+
static struct env {
char **filenames;
int filename_cnt;
@@ -195,6 +205,8 @@ 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 +258,15 @@ 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\"" },
{},
};
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 append_var_preset(struct var_preset **presets, int *cnt, const char *expr);
+static int append_var_preset_file(const char *filename);
static error_t parse_arg(int key, char *arg, struct argp_state *state)
{
@@ -363,6 +378,19 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
return -ENOMEM;
env.filename_cnt++;
break;
+ case 'G': {
+ if (arg[0] == '@') {
+ if (append_var_preset_file(arg + 1)) {
+ fprintf(stderr, "Could not parse global variables preset: %s\n",
+ arg);
+ argp_usage(state);
+ }
+ } else if (append_var_preset(&env.presets, &env.npresets, arg)) {
+ fprintf(stderr, "Could not parse global variables preset: %s\n", arg);
+ argp_usage(state);
+ }
+ break;
+ }
default:
return ARGP_ERR_UNKNOWN;
}
@@ -1292,6 +1320,249 @@ static int process_prog(const char *filename, struct bpf_object *obj, struct bpf
return 0;
};
+static int append_var_preset(struct var_preset **presets, int *cnt, const char *expr)
+{
+ void *tmp;
+ struct var_preset *cur;
+ char var[256], val[256];
+
+ tmp = realloc(*presets, (*cnt + 1) * sizeof(**presets));
+ if (!tmp)
+ return -ENOMEM;
+ *presets = tmp;
+ cur = &(*presets)[*cnt];
+ cur->applied = false;
+
+ if (sscanf(expr, "%s = %s\n", var, val) != 2) {
+ fprintf(stderr, "Could not parse expression %s\n", expr);
+ return -EINVAL;
+ }
+
+ if (isalpha(*val)) {
+ cur->svalue = strdup(val);
+ cur->type = NAME;
+ } else if (*val == '-' || isdigit(*val)) {
+ long long value;
+
+ errno = 0;
+ value = strtoll(val, NULL, 0);
+ if (errno == ERANGE) {
+ errno = 0;
+ value = strtoull(val, NULL, 0);
+ }
+ cur->ivalue = value;
+ cur->type = INTEGRAL;
+ if (errno) {
+ fprintf(stderr, "Could not parse integer value %s\n", val);
+ return -EINVAL;
+ }
+ } else {
+ fprintf(stderr, "Could not parse value %s\n", val);
+ return -EINVAL;
+ }
+ cur->name = strdup(var);
+ (*cnt)++;
+ return 0;
+}
+
+static int append_var_preset_file(const char *filename)
+{
+ char buf[1024];
+ FILE *f;
+ int err = 0;
+
+ f = fopen(filename, "rt");
+ if (!f) {
+ err = -errno;
+ fprintf(stderr, "Failed to open presets in '%s': %d\n", filename, err);
+ return -EINVAL;
+ }
+
+ while (fscanf(f, " %1023[^\n]\n", buf) == 1) {
+ if (buf[0] == '\0' || buf[0] == '#')
+ continue;
+
+ err = append_var_preset(&env.presets, &env.npresets, buf);
+ if (err)
+ goto cleanup;
+ }
+
+cleanup:
+ fclose(f);
+ return err;
+}
+
+static bool is_signed_type(const struct btf_type *t)
+{
+ if (btf_is_int(t))
+ return btf_int_encoding(t) & BTF_INT_SIGNED;
+ if (btf_is_any_enum(t))
+ return btf_kflag(t);
+ return true;
+}
+
+static int enum_value_from_name(const struct btf *btf, const struct btf_type *t,
+ const char *evalue, long long *retval)
+{
+ if (btf_is_enum(t)) {
+ struct btf_enum *e = btf_enum(t);
+ int i, n = btf_vlen(t);
+
+ for (i = 0; i < n; ++i, ++e) {
+ const char *cur_name = btf__name_by_offset(btf, e->name_off);
+
+ if (strcmp(cur_name, evalue) == 0) {
+ *retval = e->val;
+ return 0;
+ }
+ }
+ } else if (btf_is_enum64(t)) {
+ struct btf_enum64 *e = btf_enum64(t);
+ int i, n = btf_vlen(t);
+
+ for (i = 0; i < n; ++i, ++e) {
+ const char *cur_name = btf__name_by_offset(btf, e->name_off);
+ __u64 value = btf_enum64_value(e);
+
+ if (strcmp(cur_name, evalue) == 0) {
+ *retval = value;
+ return 0;
+ }
+ }
+ }
+ return -EINVAL;
+}
+
+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,
+ struct var_preset *preset)
+{
+ const struct btf_type *base_type;
+ void *ptr;
+ long long value = preset->ivalue;
+ size_t size;
+
+ base_type = btf__type_by_id(btf, btf__resolve_type(btf, t->type));
+ if (!base_type) {
+ fprintf(stderr, "Could not resolve type %d\n", t->type);
+ return -EINVAL;
+ }
+ 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;
+ }
+
+ if (preset->type == NAME && btf_is_any_enum(base_type)) {
+ if (enum_value_from_name(btf, base_type, preset->svalue, &value) != 0) {
+ fprintf(stderr, "Could not find integer value for enum element %s\n",
+ preset->svalue);
+ return -EINVAL;
+ }
+ }
+
+ /* Check if value fits into the target variable size */
+ if (sinfo->size < sizeof(preset->ivalue)) {
+ 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 (preset->ivalue >= max_val || preset->ivalue < -max_val) {
+ fprintf(stderr,
+ "Variable %s value %lld is out of range [%lld; %lld]\n",
+ btf__name_by_offset(btf, t->name_off), preset->ivalue,
+ 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;
+
+ if (__BYTE_ORDER == __LITTLE_ENDIAN) {
+ memcpy(ptr + sinfo->offset, &value, sinfo->size);
+ } else if (__BYTE_ORDER == __BIG_ENDIAN) {
+ __u8 src_offset = sizeof(value) - sinfo->size;
+
+ memcpy(ptr + sinfo->offset, (void *)&value + src_offset, 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 *t;
+ struct bpf_map *map;
+ struct btf *btf;
+ int i, j, k, n, cnt, err = 0;
+
+ if (npresets == 0)
+ return 0;
+
+ btf = bpf_object__btf(obj);
+ if (!btf)
+ return -EINVAL;
+
+ cnt = btf__type_cnt(btf);
+ for (i = 1; i != cnt; ++i) {
+ t = btf__type_by_id(btf, i);
+
+ if (!btf_is_datasec(t))
+ continue;
+
+ sinfo = btf_var_secinfos(t);
+ sec_name = btf__name_by_offset(btf, t->name_off);
+ map = bpf_object__find_map_by_name(obj, sec_name);
+ if (!map)
+ continue;
+
+ n = btf_vlen(t);
+ for (j = 0; j < n; ++j, ++sinfo) {
+ const struct btf_type *var_type = btf__type_by_id(btf, sinfo->type);
+ const char *var_name;
+
+ if (!btf_is_var(var_type))
+ continue;
+
+ var_name = btf__name_by_offset(btf, var_type->name_off);
+
+ for (k = 0; k < npresets; ++k) {
+ if (strcmp(var_name, presets[k].name) != 0)
+ continue;
+
+ if (presets[k].applied) {
+ fprintf(stderr, "Variable %s is set more than once",
+ var_name);
+ return -EINVAL;
+ }
+
+ err = set_global_var(obj, btf, var_type, map, sinfo, presets + k);
+ if (err)
+ return err;
+
+ presets[k].applied = true;
+ break;
+ }
+ }
+ }
+ for (i = 0; i < npresets; ++i) {
+ if (!presets[i].applied) {
+ fprintf(stderr, "Global variable preset %s has not been applied\n",
+ presets[i].name);
+ }
+ presets[i].applied = false;
+ }
+ return err;
+}
+
static int process_obj(const char *filename)
{
const char *base_filename = basename(strdupa(filename));
@@ -1341,6 +1612,11 @@ static int process_obj(const char *filename)
if (prog_cnt == 1) {
prog = bpf_object__next_program(obj, NULL);
bpf_program__set_autoload(prog, true);
+ err = set_global_vars(obj, env.presets, env.npresets);
+ if (err) {
+ fprintf(stderr, "Failed to set global variables\n");
+ goto cleanup;
+ }
process_prog(filename, obj, prog);
goto cleanup;
}
@@ -1355,6 +1631,12 @@ static int process_obj(const char *filename)
goto cleanup;
}
+ err = set_global_vars(tobj, env.presets, env.npresets);
+ if (err) {
+ fprintf(stderr, "Failed to set global variables\n");
+ goto cleanup;
+ }
+
lprog = NULL;
bpf_object__for_each_program(tprog, tobj) {
const char *tprog_name = bpf_program__name(tprog);
--
2.48.1
