aboutsummaryrefslogtreecommitdiff
path: root/kernel/bpf/verifier.c
diff options
context:
space:
mode:
authorAlexei Starovoitov <ast@plumgrid.com>2014-09-26 00:17:03 -0700
committerDavid S. Miller <davem@davemloft.net>2014-09-26 15:05:15 -0400
commitcbd357008604925355ae7b54a09137dabb81b580 (patch)
tree85e57d37ffdb0e743ce71c7124e07c1c9e5c3317 /kernel/bpf/verifier.c
parent51580e798cb61b0fc63fa3aa6c5c975375aa0550 (diff)
downloadlinux-linaro-stable-cbd357008604925355ae7b54a09137dabb81b580.tar.gz
bpf: verifier (add ability to receive verification log)
add optional attributes for BPF_PROG_LOAD syscall: union bpf_attr { struct { ... __u32 log_level; /* verbosity level of eBPF verifier */ __u32 log_size; /* size of user buffer */ __aligned_u64 log_buf; /* user supplied 'char *buffer' */ }; }; when log_level > 0 the verifier will return its verification log in the user supplied buffer 'log_buf' which can be used by program author to analyze why verifier rejected given program. 'Understanding eBPF verifier messages' section of Documentation/networking/filter.txt provides several examples of these messages, like the program: BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), BPF_LD_MAP_FD(BPF_REG_1, 0), BPF_CALL_FUNC(BPF_FUNC_map_lookup_elem), BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1), BPF_ST_MEM(BPF_DW, BPF_REG_0, 4, 0), BPF_EXIT_INSN(), will be rejected with the following multi-line message in log_buf: 0: (7a) *(u64 *)(r10 -8) = 0 1: (bf) r2 = r10 2: (07) r2 += -8 3: (b7) r1 = 0 4: (85) call 1 5: (15) if r0 == 0x0 goto pc+1 R0=map_ptr R10=fp 6: (7a) *(u64 *)(r0 +4) = 0 misaligned access off 4 size 8 The format of the output can change at any time as verifier evolves. Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf/verifier.c')
-rw-r--r--kernel/bpf/verifier.c235
1 files changed, 235 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d6f9c3d6b4d7..871edc1f2e1f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -125,9 +125,244 @@
* are set to NOT_INIT to indicate that they are no longer readable.
*/
+/* single container for all structs
+ * one verifier_env per bpf_check() call
+ */
+struct verifier_env {
+};
+
+/* verbose verifier prints what it's seeing
+ * bpf_check() is called under lock, so no race to access these global vars
+ */
+static u32 log_level, log_size, log_len;
+static char *log_buf;
+
+static DEFINE_MUTEX(bpf_verifier_lock);
+
+/* log_level controls verbosity level of eBPF verifier.
+ * verbose() is used to dump the verification trace to the log, so the user
+ * can figure out what's wrong with the program
+ */
+static void verbose(const char *fmt, ...)
+{
+ va_list args;
+
+ if (log_level == 0 || log_len >= log_size - 1)
+ return;
+
+ va_start(args, fmt);
+ log_len += vscnprintf(log_buf + log_len, log_size - log_len, fmt, args);
+ va_end(args);
+}
+
+static const char *const bpf_class_string[] = {
+ [BPF_LD] = "ld",
+ [BPF_LDX] = "ldx",
+ [BPF_ST] = "st",
+ [BPF_STX] = "stx",
+ [BPF_ALU] = "alu",
+ [BPF_JMP] = "jmp",
+ [BPF_RET] = "BUG",
+ [BPF_ALU64] = "alu64",
+};
+
+static const char *const bpf_alu_string[] = {
+ [BPF_ADD >> 4] = "+=",
+ [BPF_SUB >> 4] = "-=",
+ [BPF_MUL >> 4] = "*=",
+ [BPF_DIV >> 4] = "/=",
+ [BPF_OR >> 4] = "|=",
+ [BPF_AND >> 4] = "&=",
+ [BPF_LSH >> 4] = "<<=",
+ [BPF_RSH >> 4] = ">>=",
+ [BPF_NEG >> 4] = "neg",
+ [BPF_MOD >> 4] = "%=",
+ [BPF_XOR >> 4] = "^=",
+ [BPF_MOV >> 4] = "=",
+ [BPF_ARSH >> 4] = "s>>=",
+ [BPF_END >> 4] = "endian",
+};
+
+static const char *const bpf_ldst_string[] = {
+ [BPF_W >> 3] = "u32",
+ [BPF_H >> 3] = "u16",
+ [BPF_B >> 3] = "u8",
+ [BPF_DW >> 3] = "u64",
+};
+
+static const char *const bpf_jmp_string[] = {
+ [BPF_JA >> 4] = "jmp",
+ [BPF_JEQ >> 4] = "==",
+ [BPF_JGT >> 4] = ">",
+ [BPF_JGE >> 4] = ">=",
+ [BPF_JSET >> 4] = "&",
+ [BPF_JNE >> 4] = "!=",
+ [BPF_JSGT >> 4] = "s>",
+ [BPF_JSGE >> 4] = "s>=",
+ [BPF_CALL >> 4] = "call",
+ [BPF_EXIT >> 4] = "exit",
+};
+
+static void print_bpf_insn(struct bpf_insn *insn)
+{
+ u8 class = BPF_CLASS(insn->code);
+
+ if (class == BPF_ALU || class == BPF_ALU64) {
+ if (BPF_SRC(insn->code) == BPF_X)
+ verbose("(%02x) %sr%d %s %sr%d\n",
+ insn->code, class == BPF_ALU ? "(u32) " : "",
+ insn->dst_reg,
+ bpf_alu_string[BPF_OP(insn->code) >> 4],
+ class == BPF_ALU ? "(u32) " : "",
+ insn->src_reg);
+ else
+ verbose("(%02x) %sr%d %s %s%d\n",
+ insn->code, class == BPF_ALU ? "(u32) " : "",
+ insn->dst_reg,
+ bpf_alu_string[BPF_OP(insn->code) >> 4],
+ class == BPF_ALU ? "(u32) " : "",
+ insn->imm);
+ } else if (class == BPF_STX) {
+ if (BPF_MODE(insn->code) == BPF_MEM)
+ verbose("(%02x) *(%s *)(r%d %+d) = r%d\n",
+ insn->code,
+ bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
+ insn->dst_reg,
+ insn->off, insn->src_reg);
+ else if (BPF_MODE(insn->code) == BPF_XADD)
+ verbose("(%02x) lock *(%s *)(r%d %+d) += r%d\n",
+ insn->code,
+ bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
+ insn->dst_reg, insn->off,
+ insn->src_reg);
+ else
+ verbose("BUG_%02x\n", insn->code);
+ } else if (class == BPF_ST) {
+ if (BPF_MODE(insn->code) != BPF_MEM) {
+ verbose("BUG_st_%02x\n", insn->code);
+ return;
+ }
+ verbose("(%02x) *(%s *)(r%d %+d) = %d\n",
+ insn->code,
+ bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
+ insn->dst_reg,
+ insn->off, insn->imm);
+ } else if (class == BPF_LDX) {
+ if (BPF_MODE(insn->code) != BPF_MEM) {
+ verbose("BUG_ldx_%02x\n", insn->code);
+ return;
+ }
+ verbose("(%02x) r%d = *(%s *)(r%d %+d)\n",
+ insn->code, insn->dst_reg,
+ bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
+ insn->src_reg, insn->off);
+ } else if (class == BPF_LD) {
+ if (BPF_MODE(insn->code) == BPF_ABS) {
+ verbose("(%02x) r0 = *(%s *)skb[%d]\n",
+ insn->code,
+ bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
+ insn->imm);
+ } else if (BPF_MODE(insn->code) == BPF_IND) {
+ verbose("(%02x) r0 = *(%s *)skb[r%d + %d]\n",
+ insn->code,
+ bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
+ insn->src_reg, insn->imm);
+ } else if (BPF_MODE(insn->code) == BPF_IMM) {
+ verbose("(%02x) r%d = 0x%x\n",
+ insn->code, insn->dst_reg, insn->imm);
+ } else {
+ verbose("BUG_ld_%02x\n", insn->code);
+ return;
+ }
+ } else if (class == BPF_JMP) {
+ u8 opcode = BPF_OP(insn->code);
+
+ if (opcode == BPF_CALL) {
+ verbose("(%02x) call %d\n", insn->code, insn->imm);
+ } else if (insn->code == (BPF_JMP | BPF_JA)) {
+ verbose("(%02x) goto pc%+d\n",
+ insn->code, insn->off);
+ } else if (insn->code == (BPF_JMP | BPF_EXIT)) {
+ verbose("(%02x) exit\n", insn->code);
+ } else if (BPF_SRC(insn->code) == BPF_X) {
+ verbose("(%02x) if r%d %s r%d goto pc%+d\n",
+ insn->code, insn->dst_reg,
+ bpf_jmp_string[BPF_OP(insn->code) >> 4],
+ insn->src_reg, insn->off);
+ } else {
+ verbose("(%02x) if r%d %s 0x%x goto pc%+d\n",
+ insn->code, insn->dst_reg,
+ bpf_jmp_string[BPF_OP(insn->code) >> 4],
+ insn->imm, insn->off);
+ }
+ } else {
+ verbose("(%02x) %s\n", insn->code, bpf_class_string[class]);
+ }
+}
+
int bpf_check(struct bpf_prog *prog, union bpf_attr *attr)
{
+ char __user *log_ubuf = NULL;
+ struct verifier_env *env;
int ret = -EINVAL;
+ if (prog->len <= 0 || prog->len > BPF_MAXINSNS)
+ return -E2BIG;
+
+ /* 'struct verifier_env' can be global, but since it's not small,
+ * allocate/free it every time bpf_check() is called
+ */
+ env = kzalloc(sizeof(struct verifier_env), GFP_KERNEL);
+ if (!env)
+ return -ENOMEM;
+
+ /* grab the mutex to protect few globals used by verifier */
+ mutex_lock(&bpf_verifier_lock);
+
+ if (attr->log_level || attr->log_buf || attr->log_size) {
+ /* user requested verbose verifier output
+ * and supplied buffer to store the verification trace
+ */
+ log_level = attr->log_level;
+ log_ubuf = (char __user *) (unsigned long) attr->log_buf;
+ log_size = attr->log_size;
+ log_len = 0;
+
+ ret = -EINVAL;
+ /* log_* values have to be sane */
+ if (log_size < 128 || log_size > UINT_MAX >> 8 ||
+ log_level == 0 || log_ubuf == NULL)
+ goto free_env;
+
+ ret = -ENOMEM;
+ log_buf = vmalloc(log_size);
+ if (!log_buf)
+ goto free_env;
+ } else {
+ log_level = 0;
+ }
+
+ /* ret = do_check(env); */
+
+ if (log_level && log_len >= log_size - 1) {
+ BUG_ON(log_len >= log_size);
+ /* verifier log exceeded user supplied buffer */
+ ret = -ENOSPC;
+ /* fall through to return what was recorded */
+ }
+
+ /* copy verifier log back to user space including trailing zero */
+ if (log_level && copy_to_user(log_ubuf, log_buf, log_len + 1) != 0) {
+ ret = -EFAULT;
+ goto free_log_buf;
+ }
+
+
+free_log_buf:
+ if (log_level)
+ vfree(log_buf);
+free_env:
+ kfree(env);
+ mutex_unlock(&bpf_verifier_lock);
return ret;
}