Helpers that expect ARG_PTR_TO_MAP_KEY and ARG_PTR_TO_MAP_VALUE can only
access stack and packet memory. Allow these helpers to directly access map
values by passing registers of type PTR_TO_MAP_VALUE.
This change removes the need for an extra copy to the stack when using a
map value to perform a second map lookup, as in the following:
struct bpf_map_def SEC("maps") infobyreq = {
.type = BPF_MAP_TYPE_HASHMAP,
.key_size = sizeof(struct request *),
.value_size = sizeof(struct info_t),
.max_entries = 1024,
};
struct bpf_map_def SEC("maps") counts = {
.type = BPF_MAP_TYPE_HASHMAP,
.key_size = sizeof(struct info_t),
.value_size = sizeof(u64),
.max_entries = 1024,
};
SEC("kprobe/blk_account_io_start")
int bpf_blk_account_io_start(struct pt_regs *ctx)
{
struct info_t *info = bpf_map_lookup_elem(&infobyreq, &ctx->di);
u64 *count = bpf_map_lookup_elem(&counts, info);
(*count)++;
}
Signed-off-by: Paul Chaignon <paul.chaig...@orange.com>
---
Changes in v2:
- Additional test cases for adjusted maps.
kernel/bpf/verifier.c | 9 +++-
tools/testing/selftests/bpf/test_verifier.c | 84 +++++++++++++++++++++++++++++
2 files changed, 92 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d690c7d..50e057d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1351,7 +1351,8 @@ static int check_func_arg(struct bpf_verifier_env *env,
u32 regno,
if (arg_type == ARG_PTR_TO_MAP_KEY ||
arg_type == ARG_PTR_TO_MAP_VALUE) {
expected_type = PTR_TO_STACK;
- if (type != PTR_TO_PACKET && type != expected_type)
+ if (type != PTR_TO_PACKET && type != PTR_TO_MAP_VALUE &&
+ type != expected_type)
goto err_type;
} else if (arg_type == ARG_CONST_SIZE ||
arg_type == ARG_CONST_SIZE_OR_ZERO) {
@@ -1404,6 +1405,9 @@ static int check_func_arg(struct bpf_verifier_env *env,
u32 regno,
if (type == PTR_TO_PACKET)
err = check_packet_access(env, regno, reg->off,
meta->map_ptr->key_size);
+ else if (type == PTR_TO_MAP_VALUE)
+ err = check_map_access(env, regno, 0,
+ meta->map_ptr->key_size);
else
err = check_stack_boundary(env, regno,
meta->map_ptr->key_size,
@@ -1420,6 +1424,9 @@ static int check_func_arg(struct bpf_verifier_env *env,
u32 regno,
if (type == PTR_TO_PACKET)
err = check_packet_access(env, regno, reg->off,
meta->map_ptr->value_size);
+ else if (type == PTR_TO_MAP_VALUE)
+ err = check_map_access(env, regno, 0,
+ meta->map_ptr->key_size);
else
err = check_stack_boundary(env, regno,
meta->map_ptr->value_size,
diff --git a/tools/testing/selftests/bpf/test_verifier.c
b/tools/testing/selftests/bpf/test_verifier.c
index 8eb0995..4532066 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -5052,6 +5052,90 @@ static struct bpf_test tests[] = {
.prog_type = BPF_PROG_TYPE_TRACEPOINT,
},
{
+ "map helper access to map",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 4),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_0),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map1 = { 3, 8 },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+ },
+ {
+ "map helper access to adjusted map (via const imm)",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 5),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_0),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2,
+ offsetof(struct test_val, foo)),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map1 = { 9 },
+ .fixup_map2 = { 3 },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+ },
+ {
+ "map helper access to adjusted map (via const reg)",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 6),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_0),
+ BPF_MOV64_IMM(BPF_REG_3,
+ offsetof(struct test_val, foo)),
+ BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_3),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map1 = { 10 },
+ .fixup_map2 = { 3 },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+ },
+ {
+ "map helper access to adjusted map (via variable)",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 7),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_0),
+ BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_0, 0),
+ BPF_JMP_IMM(BPF_JGT, BPF_REG_3,
+ offsetof(struct test_val, foo), 4),
+ BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_3),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map1 = { 11 },
+ .fixup_map2 = { 3 },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+ },
+ {
"map element value is preserved across register spilling",
.insns = {
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
--
2.7.4
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