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selftests/bpf: track string payload offset as scalar in strobemeta 

This change prepares strobemeta for update in callbacks verification
logic. To allow bpf_loop() verification converge when multiple
callback iterations are considered:
- track offset inside strobemeta_payload->payload directly as scalar
  value;
- at each iteration make sure that remaining
  strobemeta_payload->payload capacity is sufficient for execution of
  read_{map,str}_var functions;
- make sure that offset is tracked as unbound scalar between
  iterations, otherwise verifier won't be able infer that bpf_loop
  callback reaches identical states.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20231121020701.26440-3-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman 2023-11-21 04:06:52 +02:00 committed by Alexei Starovoitov
parent 977bc146d4
commit 87eb0152bc
1 changed files with 48 additions and 30 deletions
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78
tools/testing/selftests/bpf/progs/strobemeta.h
View File

@ -24,9 +24,11 @@ struct task_struct {};
#define STACK_TABLE_EPOCH_SHIFT 20
#define STROBE_MAX_STR_LEN 1
#define STROBE_MAX_CFGS 32
#define READ_MAP_VAR_PAYLOAD_CAP \
((1 + STROBE_MAX_MAP_ENTRIES * 2) * STROBE_MAX_STR_LEN)
#define STROBE_MAX_PAYLOAD \
(STROBE_MAX_STRS * STROBE_MAX_STR_LEN + \
STROBE_MAX_MAPS * (1 + STROBE_MAX_MAP_ENTRIES * 2) * STROBE_MAX_STR_LEN)
STROBE_MAX_MAPS * READ_MAP_VAR_PAYLOAD_CAP)
struct strobe_value_header {
/*
@ -355,7 +357,7 @@ static __always_inline uint64_t read_str_var(struct strobemeta_cfg *cfg,
size_t idx, void *tls_base,
struct strobe_value_generic *value,
struct strobemeta_payload *data,
void *payload)
size_t off)
{
void *location;
uint64_t len;
@ -366,7 +368,7 @@ static __always_inline uint64_t read_str_var(struct strobemeta_cfg *cfg,
return 0;
bpf_probe_read_user(value, sizeof(struct strobe_value_generic), location);
len = bpf_probe_read_user_str(payload, STROBE_MAX_STR_LEN, value->ptr);
len = bpf_probe_read_user_str(&data->payload[off], STROBE_MAX_STR_LEN, value->ptr);
/*
* if bpf_probe_read_user_str returns error (<0), due to casting to
* unsinged int, it will become big number, so next check is
@ -378,14 +380,14 @@ static __always_inline uint64_t read_str_var(struct strobemeta_cfg *cfg,
return 0;
data->str_lens[idx] = len;
return len;
return off + len;
}
static __always_inline void *read_map_var(struct strobemeta_cfg *cfg,
size_t idx, void *tls_base,
struct strobe_value_generic *value,
struct strobemeta_payload *data,
void *payload)
static __always_inline uint64_t read_map_var(struct strobemeta_cfg *cfg,
size_t idx, void *tls_base,
struct strobe_value_generic *value,
struct strobemeta_payload *data,
size_t off)
{
struct strobe_map_descr* descr = &data->map_descrs[idx];
struct strobe_map_raw map;
@ -397,11 +399,11 @@ static __always_inline void *read_map_var(struct strobemeta_cfg *cfg,
location = calc_location(&cfg->map_locs[idx], tls_base);
if (!location)
return payload;
return off;
bpf_probe_read_user(value, sizeof(struct strobe_value_generic), location);
if (bpf_probe_read_user(&map, sizeof(struct strobe_map_raw), value->ptr))
return payload;
return off;
descr->id = map.id;
descr->cnt = map.cnt;
@ -410,10 +412,10 @@ static __always_inline void *read_map_var(struct strobemeta_cfg *cfg,
data->req_meta_valid = 1;
}
len = bpf_probe_read_user_str(payload, STROBE_MAX_STR_LEN, map.tag);
len = bpf_probe_read_user_str(&data->payload[off], STROBE_MAX_STR_LEN, map.tag);
if (len <= STROBE_MAX_STR_LEN) {
descr->tag_len = len;
payload += len;
off += len;
}
#ifdef NO_UNROLL
@ -426,22 +428,22 @@ static __always_inline void *read_map_var(struct strobemeta_cfg *cfg,
break;
descr->key_lens[i] = 0;
len = bpf_probe_read_user_str(payload, STROBE_MAX_STR_LEN,
len = bpf_probe_read_user_str(&data->payload[off], STROBE_MAX_STR_LEN,
map.entries[i].key);
if (len <= STROBE_MAX_STR_LEN) {
descr->key_lens[i] = len;
payload += len;
off += len;
}
descr->val_lens[i] = 0;
len = bpf_probe_read_user_str(payload, STROBE_MAX_STR_LEN,
len = bpf_probe_read_user_str(&data->payload[off], STROBE_MAX_STR_LEN,
map.entries[i].val);
if (len <= STROBE_MAX_STR_LEN) {
descr->val_lens[i] = len;
payload += len;
off += len;
}
}
return payload;
return off;
}
#ifdef USE_BPF_LOOP
@ -455,14 +457,20 @@ struct read_var_ctx {
struct strobemeta_payload *data;
void *tls_base;
struct strobemeta_cfg *cfg;
void *payload;
size_t payload_off;
/* value gets mutated */
struct strobe_value_generic *value;
enum read_type type;
};
static int read_var_callback(__u32 index, struct read_var_ctx *ctx)
static int read_var_callback(__u64 index, struct read_var_ctx *ctx)
{
/* lose precision info for ctx->payload_off, verifier won't track
* double xor, barrier_var() is needed to force clang keep both xors.
*/
ctx->payload_off ^= index;
barrier_var(ctx->payload_off);
ctx->payload_off ^= index;
switch (ctx->type) {
case READ_INT_VAR:
if (index >= STROBE_MAX_INTS)
@ -472,14 +480,18 @@ static int read_var_callback(__u32 index, struct read_var_ctx *ctx)
case READ_MAP_VAR:
if (index >= STROBE_MAX_MAPS)
return 1;
ctx->payload = read_map_var(ctx->cfg, index, ctx->tls_base,
ctx->value, ctx->data, ctx->payload);
if (ctx->payload_off > sizeof(ctx->data->payload) - READ_MAP_VAR_PAYLOAD_CAP)
return 1;
ctx->payload_off = read_map_var(ctx->cfg, index, ctx->tls_base,
ctx->value, ctx->data, ctx->payload_off);
break;
case READ_STR_VAR:
if (index >= STROBE_MAX_STRS)
return 1;
ctx->payload += read_str_var(ctx->cfg, index, ctx->tls_base,
ctx->value, ctx->data, ctx->payload);
if (ctx->payload_off > sizeof(ctx->data->payload) - STROBE_MAX_STR_LEN)
return 1;
ctx->payload_off = read_str_var(ctx->cfg, index, ctx->tls_base,
ctx->value, ctx->data, ctx->payload_off);
break;
}
return 0;
@ -501,7 +513,8 @@ static void *read_strobe_meta(struct task_struct *task,
pid_t pid = bpf_get_current_pid_tgid() >> 32;
struct strobe_value_generic value = {0};
struct strobemeta_cfg *cfg;
void *tls_base, *payload;
size_t payload_off;
void *tls_base;
cfg = bpf_map_lookup_elem(&strobemeta_cfgs, &pid);
if (!cfg)
@ -509,7 +522,7 @@ static void *read_strobe_meta(struct task_struct *task,
data->int_vals_set_mask = 0;
data->req_meta_valid = 0;
payload = data->payload;
payload_off = 0;
/*
* we don't have struct task_struct definition, it should be:
* tls_base = (void *)task->thread.fsbase;
@ -522,7 +535,7 @@ static void *read_strobe_meta(struct task_struct *task,
.tls_base = tls_base,
.value = &value,
.data = data,
.payload = payload,
.payload_off = 0,
};
int err;
@ -540,6 +553,11 @@ static void *read_strobe_meta(struct task_struct *task,
err = bpf_loop(STROBE_MAX_MAPS, read_var_callback, &ctx, 0);
if (err != STROBE_MAX_MAPS)
return NULL;
payload_off = ctx.payload_off;
/* this should not really happen, here only to satisfy verifer */
if (payload_off > sizeof(data->payload))
payload_off = sizeof(data->payload);
#else
#ifdef NO_UNROLL
#pragma clang loop unroll(disable)
@ -555,7 +573,7 @@ static void *read_strobe_meta(struct task_struct *task,
#pragma unroll
#endif /* NO_UNROLL */
for (int i = 0; i < STROBE_MAX_STRS; ++i) {
payload += read_str_var(cfg, i, tls_base, &value, data, payload);
payload_off = read_str_var(cfg, i, tls_base, &value, data, payload_off);
}
#ifdef NO_UNROLL
#pragma clang loop unroll(disable)
@ -563,7 +581,7 @@ static void *read_strobe_meta(struct task_struct *task,
#pragma unroll
#endif /* NO_UNROLL */
for (int i = 0; i < STROBE_MAX_MAPS; ++i) {
payload = read_map_var(cfg, i, tls_base, &value, data, payload);
payload_off = read_map_var(cfg, i, tls_base, &value, data, payload_off);
}
#endif /* USE_BPF_LOOP */
@ -571,7 +589,7 @@ static void *read_strobe_meta(struct task_struct *task,
* return pointer right after end of payload, so it's possible to
* calculate exact amount of useful data that needs to be sent
*/
return payload;
return &data->payload[payload_off];
}
SEC("raw_tracepoint/kfree_skb")