Implement filter bytecode interpreter and linker
[lttng-ust.git] / liblttng-ust / lttng-filter.c
index b617bc9ad1e1aa47529c875b3ec4d05e3de0e7b5..37e1cf56fd40edb2546790ac8166553cdeaa312e 100644 (file)
 #include <stdio.h>
 #include <helper.h>
 #include <lttng/ust-events.h>
+#include <stdint.h>
+#include <errno.h>
+#include <string.h>
+#include <inttypes.h>
+#include <limits.h>
+#include "filter-bytecode.h"
+
+#define NR_REG         2
+
+#ifndef min_t
+#define min_t(type, a, b)      \
+               ((type) (a) < (type) (b) ? (type) (a) : (type) (b))
+#endif
+
+#ifndef likely
+#define likely(x)      __builtin_expect(!!(x), 1)
+#endif
+
+#ifndef unlikely
+#define unlikely(x)    __builtin_expect(!!(x), 0)
+#endif
+
+#ifdef DEBUG
+#define dbg_printf(fmt, args...)     printf("[debug bytecode] " fmt, ## args)
+#else
+#define dbg_printf(fmt, args...)                               \
+do {                                                           \
+       /* do nothing but check printf format */                \
+       if (0)                                                  \
+               printf("[debug bytecode] " fmt, ## args);       \
+} while (0)
+#endif
+
+/* Linked bytecode */
+struct bytecode_runtime {
+       uint16_t len;
+       char data[0];
+};
+
+struct reg {
+       enum {
+               REG_S64,
+               REG_STRING,     /* NULL-terminated string */
+               REG_SEQUENCE,   /* non-null terminated */
+       } type;
+       int64_t v;
+
+       const char *str;
+       size_t seq_len;
+       int literal;            /* is string literal ? */
+};
+
+static const char *opnames[] = {
+       [ FILTER_OP_UNKNOWN ] = "UNKNOWN",
+
+       [ FILTER_OP_RETURN ] = "RETURN",
+
+       /* binary */
+       [ FILTER_OP_MUL ] = "MUL",
+       [ FILTER_OP_DIV ] = "DIV",
+       [ FILTER_OP_MOD ] = "MOD",
+       [ FILTER_OP_PLUS ] = "PLUS",
+       [ FILTER_OP_MINUS ] = "MINUS",
+       [ FILTER_OP_RSHIFT ] = "RSHIFT",
+       [ FILTER_OP_LSHIFT ] = "LSHIFT",
+       [ FILTER_OP_BIN_AND ] = "BIN_AND",
+       [ FILTER_OP_BIN_OR ] = "BIN_OR",
+       [ FILTER_OP_BIN_XOR ] = "BIN_XOR",
+       [ FILTER_OP_EQ ] = "EQ",
+       [ FILTER_OP_NE ] = "NE",
+       [ FILTER_OP_GT ] = "GT",
+       [ FILTER_OP_LT ] = "LT",
+       [ FILTER_OP_GE ] = "GE",
+       [ FILTER_OP_LE ] = "LE",
+
+       /* unary */
+       [ FILTER_OP_UNARY_PLUS ] = "UNARY_PLUS",
+       [ FILTER_OP_UNARY_MINUS ] = "UNARY_MINUS",
+       [ FILTER_OP_UNARY_NOT ] = "UNARY_NOT",
+
+       /* logical */
+       [ FILTER_OP_AND ] = "AND",
+       [ FILTER_OP_OR ] = "OR",
+
+       /* load */
+       [ FILTER_OP_LOAD_FIELD_REF ] = "LOAD_FIELD_REF",
+       [ FILTER_OP_LOAD_STRING ] = "LOAD_STRING",
+       [ FILTER_OP_LOAD_S64 ] = "LOAD_S64",
+};
+
+static
+const char *print_op(enum filter_op op)
+{
+       if (op >= NR_FILTER_OPS)
+               return "UNKNOWN";
+       else
+               return opnames[op];
+}
+
+/*
+ * -1: wildcard found.
+ * -2: unknown escape char.
+ * 0: normal char.
+ */
+
+static
+int parse_char(const char **p)
+{
+       switch (**p) {
+       case '\\':
+               (*p)++;
+               switch (**p) {
+               case '\\':
+               case '*':
+                       return 0;
+               default:
+                       return -2;
+               }
+       case '*':
+               return -1;
+       default:
+               return 0;
+       }
+}
+
+static
+int reg_strcmp(struct reg reg[NR_REG], const char *cmp_type)
+{
+       const char *p = reg[REG_R0].str, *q = reg[REG_R1].str;
+       int ret;
+       int diff;
+
+       for (;;) {
+               int escaped_r0 = 0;
+
+               if (unlikely(p - reg[REG_R0].str > reg[REG_R0].seq_len || *p == '\0')) {
+                       if (q - reg[REG_R1].str > reg[REG_R1].seq_len || *q == '\0')
+                               diff = 0;
+                       else
+                               diff = -1;
+                       break;
+               }
+               if (unlikely(q - reg[REG_R1].str > reg[REG_R1].seq_len || *q == '\0')) {
+                       if (p - reg[REG_R0].str > reg[REG_R0].seq_len || *p == '\0')
+                               diff = 0;
+                       else
+                               diff = 1;
+                       break;
+               }
+               if (reg[REG_R0].literal) {
+                       ret = parse_char(&p);
+                       if (ret == -1) {
+                               return 0;
+                       } else if (ret == -2) {
+                               escaped_r0 = 1;
+                       }
+                       /* else compare both char */
+               }
+               if (reg[REG_R1].literal) {
+                       ret = parse_char(&q);
+                       if (ret == -1) {
+                               return 0;
+                       } else if (ret == -2) {
+                               if (!escaped_r0)
+                                       return -1;
+                       } else {
+                               if (escaped_r0)
+                                       return 1;
+                       }
+               } else {
+                       if (escaped_r0)
+                               return 1;
+               }
+               diff = *p - *q;
+               if (diff != 0)
+                       break;
+               p++;
+               q++;
+       }
+       return diff;
+}
+
+static
+int lttng_filter_false(void *filter_data,
+               const char *filter_stack_data)
+{
+       return 0;
+}
 
 static
 int lttng_filter_interpret_bytecode(void *filter_data,
                const char *filter_stack_data)
 {
-       /* TODO */
+       struct bytecode_runtime *bytecode = filter_data;
+       void *pc, *next_pc, *start_pc;
+       int ret = -EINVAL;
+       int retval = 0;
+       struct reg reg[NR_REG];
+       int i;
+
+       for (i = 0; i < NR_REG; i++) {
+               reg[i].type = REG_S64;
+               reg[i].v = 0;
+               reg[i].str = NULL;
+               reg[i].seq_len = 0;
+               reg[i].literal = 0;
+       }
+
+       start_pc = &bytecode->data[0];
+       for (pc = next_pc = start_pc; pc - start_pc < bytecode->len;
+                       pc = next_pc) {
+               if (unlikely(pc >= start_pc + bytecode->len)) {
+                       fprintf(stderr, "[error] filter bytecode overflow\n");
+                       ret = -EINVAL;
+                       goto end;
+               }
+               dbg_printf("Executing op %s (%u)\n",
+                       print_op((unsigned int) *(filter_opcode_t *) pc),
+                       (unsigned int) *(filter_opcode_t *) pc);
+               switch (*(filter_opcode_t *) pc) {
+               case FILTER_OP_UNKNOWN:
+               default:
+                       fprintf(stderr, "[error] unknown bytecode op %u\n",
+                               (unsigned int) *(filter_opcode_t *) pc);
+                       ret = -EINVAL;
+                       goto end;
+
+               case FILTER_OP_RETURN:
+                       retval = !!reg[0].v;
+                       ret = 0;
+                       goto end;
+
+               /* binary */
+               case FILTER_OP_MUL:
+               case FILTER_OP_DIV:
+               case FILTER_OP_MOD:
+               case FILTER_OP_PLUS:
+               case FILTER_OP_MINUS:
+               case FILTER_OP_RSHIFT:
+               case FILTER_OP_LSHIFT:
+               case FILTER_OP_BIN_AND:
+               case FILTER_OP_BIN_OR:
+               case FILTER_OP_BIN_XOR:
+                       fprintf(stderr, "[error] unsupported bytecode op %u\n",
+                               (unsigned int) *(filter_opcode_t *) pc);
+                       ret = -EINVAL;
+                       goto end;
+
+               case FILTER_OP_EQ:
+               {
+                       if (unlikely((reg[REG_R0].type == REG_S64 && reg[REG_R1].type != REG_S64)
+                                       || (reg[REG_R0].type != REG_S64 && reg[REG_R1].type == REG_S64))) {
+                               fprintf(stderr, "[error] type mismatch for '==' binary operator\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       switch (reg[REG_R0].type) {
+                       default:
+                               fprintf(stderr, "[error] unknown register type\n");
+                               ret = -EINVAL;
+                               goto end;
+
+                       case REG_STRING:
+                       case REG_SEQUENCE:
+                               reg[REG_R0].v = (reg_strcmp(reg, "==") == 0);
+                               break;
+                       case REG_S64:
+                               reg[REG_R0].v = (reg[REG_R0].v == reg[REG_R1].v);
+                               break;
+                       }
+                       reg[REG_R0].type = REG_S64;
+                       next_pc += sizeof(struct binary_op);
+                       break;
+               }
+               case FILTER_OP_NE:
+               {
+                       if (unlikely((reg[REG_R0].type == REG_S64 && reg[REG_R1].type != REG_S64)
+                                       || (reg[REG_R0].type != REG_S64 && reg[REG_R1].type == REG_S64))) {
+                               fprintf(stderr, "[error] type mismatch for '!=' binary operator\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       switch (reg[REG_R0].type) {
+                       default:
+                               fprintf(stderr, "[error] unknown register type\n");
+                               ret = -EINVAL;
+                               goto end;
+
+                       case REG_STRING:
+                       case REG_SEQUENCE:
+                               reg[REG_R0].v = (reg_strcmp(reg, "!=") != 0);
+                               break;
+                       case REG_S64:
+                               reg[REG_R0].v = (reg[REG_R0].v != reg[REG_R1].v);
+                               break;
+                       }
+                       reg[REG_R0].type = REG_S64;
+                       next_pc += sizeof(struct binary_op);
+                       break;
+               }
+               case FILTER_OP_GT:
+               {
+                       if (unlikely((reg[REG_R0].type == REG_S64 && reg[REG_R1].type != REG_S64)
+                                       || (reg[REG_R0].type != REG_S64 && reg[REG_R1].type == REG_S64))) {
+                               fprintf(stderr, "[error] type mismatch for '>' binary operator\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       switch (reg[REG_R0].type) {
+                       default:
+                               fprintf(stderr, "[error] unknown register type\n");
+                               ret = -EINVAL;
+                               goto end;
+
+                       case REG_STRING:
+                       case REG_SEQUENCE:
+                               reg[REG_R0].v = (reg_strcmp(reg, ">") > 0);
+                               break;
+                       case REG_S64:
+                               reg[REG_R0].v = (reg[REG_R0].v > reg[REG_R1].v);
+                               break;
+                       }
+                       reg[REG_R0].type = REG_S64;
+                       next_pc += sizeof(struct binary_op);
+                       break;
+               }
+               case FILTER_OP_LT:
+               {
+                       if (unlikely((reg[REG_R0].type == REG_S64 && reg[REG_R1].type != REG_S64)
+                                       || (reg[REG_R0].type != REG_S64 && reg[REG_R1].type == REG_S64))) {
+                               fprintf(stderr, "[error] type mismatch for '<' binary operator\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       switch (reg[REG_R0].type) {
+                       default:
+                               fprintf(stderr, "[error] unknown register type\n");
+                               ret = -EINVAL;
+                               goto end;
+
+                       case REG_STRING:
+                       case REG_SEQUENCE:
+                               reg[REG_R0].v = (reg_strcmp(reg, "<") < 0);
+                               break;
+                       case REG_S64:
+                               reg[REG_R0].v = (reg[REG_R0].v < reg[REG_R1].v);
+                               break;
+                       }
+                       reg[REG_R0].type = REG_S64;
+                       next_pc += sizeof(struct binary_op);
+                       break;
+               }
+               case FILTER_OP_GE:
+               {
+                       if (unlikely((reg[REG_R0].type == REG_S64 && reg[REG_R1].type != REG_S64)
+                                       || (reg[REG_R0].type != REG_S64 && reg[REG_R1].type == REG_S64))) {
+                               fprintf(stderr, "[error] type mismatch for '>=' binary operator\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       switch (reg[REG_R0].type) {
+                       default:
+                               fprintf(stderr, "[error] unknown register type\n");
+                               ret = -EINVAL;
+                               goto end;
+
+                       case REG_STRING:
+                       case REG_SEQUENCE:
+                               reg[REG_R0].v = (reg_strcmp(reg, ">=") >= 0);
+                               break;
+                       case REG_S64:
+                               reg[REG_R0].v = (reg[REG_R0].v >= reg[REG_R1].v);
+                               break;
+                       }
+                       reg[REG_R0].type = REG_S64;
+                       next_pc += sizeof(struct binary_op);
+                       break;
+               }
+               case FILTER_OP_LE:
+               {
+                       if (unlikely((reg[REG_R0].type == REG_S64 && reg[REG_R1].type != REG_S64)
+                                       || (reg[REG_R0].type != REG_S64 && reg[REG_R1].type == REG_S64))) {
+                               fprintf(stderr, "[error] type mismatch for '<=' binary operator\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       switch (reg[REG_R0].type) {
+                       default:
+                               fprintf(stderr, "[error] unknown register type\n");
+                               ret = -EINVAL;
+                               goto end;
+
+                       case REG_STRING:
+                       case REG_SEQUENCE:
+                               reg[REG_R0].v = (reg_strcmp(reg, "<=") <= 0);
+                               break;
+                       case REG_S64:
+                               reg[REG_R0].v = (reg[REG_R0].v <= reg[REG_R1].v);
+                               break;
+                       }
+                       reg[REG_R0].type = REG_S64;
+                       next_pc += sizeof(struct binary_op);
+                       break;
+               }
+
+               /* unary */
+               case FILTER_OP_UNARY_PLUS:
+               {
+                       struct unary_op *insn = (struct unary_op *) pc;
+
+                       if (unlikely(insn->reg >= REG_ERROR)) {
+                               fprintf(stderr, "[error] invalid register %u\n",
+                                       (unsigned int) insn->reg);
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       if (unlikely(reg[insn->reg].type != REG_S64)) {
+                               fprintf(stderr, "[error] Unary plus can only be applied to numeric register\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       next_pc += sizeof(struct unary_op);
+                       break;
+               }
+               case FILTER_OP_UNARY_MINUS:
+               {
+                       struct unary_op *insn = (struct unary_op *) pc;
+
+                       if (unlikely(insn->reg >= REG_ERROR)) {
+                               fprintf(stderr, "[error] invalid register %u\n",
+                                       (unsigned int) insn->reg);
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       if (unlikely(reg[insn->reg].type != REG_S64)) {
+                               fprintf(stderr, "[error] Unary minus can only be applied to numeric register\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       reg[insn->reg].v = -reg[insn->reg].v;
+                       next_pc += sizeof(struct unary_op);
+                       break;
+               }
+               case FILTER_OP_UNARY_NOT:
+               {
+                       struct unary_op *insn = (struct unary_op *) pc;
+
+                       if (unlikely(insn->reg >= REG_ERROR)) {
+                               fprintf(stderr, "[error] invalid register %u\n",
+                                       (unsigned int) insn->reg);
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       if (unlikely(reg[insn->reg].type != REG_S64)) {
+                               fprintf(stderr, "[error] Unary not can only be applied to numeric register\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       reg[insn->reg].v = !reg[insn->reg].v;
+                       next_pc += sizeof(struct unary_op);
+                       break;
+               }
+               /* logical */
+               case FILTER_OP_AND:
+               {
+                       struct logical_op *insn = (struct logical_op *) pc;
+
+                       if (unlikely(reg[REG_R0].type != REG_S64)) {
+                               fprintf(stderr, "[error] Logical operator 'and' can only be applied to numeric register\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+
+                       /* If REG_R0 is 0, skip and evaluate to 0 */
+                       if (reg[REG_R0].v == 0) {
+                               dbg_printf("Jumping to bytecode offset %u\n",
+                                       (unsigned int) insn->skip_offset);
+                               next_pc = start_pc + insn->skip_offset;
+                               if (unlikely(next_pc <= pc)) {
+                                       fprintf(stderr, "[error] Loops are not allowed in bytecode\n");
+                                       ret = -EINVAL;
+                                       goto end;
+                               }
+                       } else {
+                               next_pc += sizeof(struct logical_op);
+                       }
+                       break;
+               }
+               case FILTER_OP_OR:
+               {
+                       struct logical_op *insn = (struct logical_op *) pc;
+
+                       if (unlikely(reg[REG_R0].type != REG_S64)) {
+                               fprintf(stderr, "[error] Logical operator 'and' can only be applied to numeric register\n");
+                               ret = -EINVAL;
+                               goto end;
+                       }
+
+                       /* If REG_R0 is nonzero, skip and evaluate to 1 */
+                       if (reg[REG_R0].v != 0) {
+                               reg[REG_R0].v = 1;
+                               dbg_printf("Jumping to bytecode offset %u\n",
+                                       (unsigned int) insn->skip_offset);
+                               next_pc = start_pc + insn->skip_offset;
+                               if (unlikely(next_pc <= pc)) {
+                                       fprintf(stderr, "[error] Loops are not allowed in bytecode\n");
+                                       ret = -EINVAL;
+                                       goto end;
+                               }
+                       } else {
+                               next_pc += sizeof(struct logical_op);
+                       }
+                       break;
+               }
+
+               /* load */
+               case FILTER_OP_LOAD_FIELD_REF:
+               {
+                       struct load_op *insn = (struct load_op *) pc;
+                       struct field_ref *ref = (struct field_ref *) insn->data;
+
+                       if (unlikely(insn->reg >= REG_ERROR)) {
+                               fprintf(stderr, "[error] invalid register %u\n",
+                                       (unsigned int) insn->reg);
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       dbg_printf("load field ref offset %u type %u\n",
+                               ref->offset, ref->type);
+                       switch (ref->type) {
+                       case FIELD_REF_UNKNOWN:
+                       default:
+                               fprintf(stderr, "[error] unknown field ref type\n");
+                               ret = -EINVAL;
+                               goto end;
+
+                       case FIELD_REF_STRING:
+                               reg[insn->reg].str =
+                                       *(const char * const *) &filter_stack_data[ref->offset];
+                               reg[insn->reg].type = REG_STRING;
+                               reg[insn->reg].seq_len = UINT_MAX;
+                               reg[insn->reg].literal = 0;
+                               dbg_printf("ref load string %s\n", reg[insn->reg].str);
+                               break;
+                       case FIELD_REF_SEQUENCE:
+                               reg[insn->reg].seq_len =
+                                       *(unsigned long *) &filter_stack_data[ref->offset];
+                               reg[insn->reg].str =
+                                       *(const char **) (&filter_stack_data[ref->offset
+                                                                       + sizeof(unsigned long)]);
+                               reg[insn->reg].type = REG_SEQUENCE;
+                               reg[insn->reg].literal = 0;
+                               break;
+                       case FIELD_REF_S64:
+                               memcpy(&reg[insn->reg].v, &filter_stack_data[ref->offset],
+                                       sizeof(struct literal_numeric));
+                               reg[insn->reg].type = REG_S64;
+                               reg[insn->reg].literal = 0;
+                               dbg_printf("ref load s64 %" PRIi64 "\n", reg[insn->reg].v);
+                               break;
+                       }
+
+                       next_pc += sizeof(struct load_op) + sizeof(struct field_ref);
+                       break;
+               }
+
+               case FILTER_OP_LOAD_STRING:
+               {
+                       struct load_op *insn = (struct load_op *) pc;
+
+                       if (unlikely(insn->reg >= REG_ERROR)) {
+                               fprintf(stderr, "[error] invalid register %u\n",
+                                       (unsigned int) insn->reg);
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       dbg_printf("load string %s\n", insn->data);
+                       reg[insn->reg].str = insn->data;
+                       reg[insn->reg].type = REG_STRING;
+                       reg[insn->reg].seq_len = UINT_MAX;
+                       reg[insn->reg].literal = 1;
+                       next_pc += sizeof(struct load_op) + strlen(insn->data) + 1;
+                       break;
+               }
+
+               case FILTER_OP_LOAD_S64:
+               {
+                       struct load_op *insn = (struct load_op *) pc;
+
+                       if (unlikely(insn->reg >= REG_ERROR)) {
+                               fprintf(stderr, "[error] invalid register %u\n",
+                                       (unsigned int) insn->reg);
+                               ret = -EINVAL;
+                               goto end;
+                       }
+                       memcpy(&reg[insn->reg].v, insn->data,
+                               sizeof(struct literal_numeric));
+                       dbg_printf("load s64 %" PRIi64 "\n", reg[insn->reg].v);
+                       reg[insn->reg].type = REG_S64;
+                       next_pc += sizeof(struct load_op)
+                                       + sizeof(struct literal_numeric);
+                       break;
+               }
+               }
+       }
+end:
+       /* return 0 (discard) on error */
+       if (ret)
+               return 0;
+       return retval;
+}
+
+static
+int apply_field_reloc(struct ltt_event *event,
+               struct bytecode_runtime *runtime,
+               uint32_t runtime_len,
+               uint32_t reloc_offset,
+               const char *field_name)
+{
+       const struct lttng_event_desc *desc;
+       const struct lttng_event_field *fields, *field = NULL;
+       unsigned int nr_fields, i;
+       struct field_ref *field_ref;
+       uint32_t field_offset = 0;
+
+       fprintf(stderr, "Apply reloc: %u %s\n", reloc_offset, field_name);
+
+       /* Ensure that the reloc is within the code */
+       if (runtime_len - reloc_offset < sizeof(uint16_t))
+               return -EINVAL;
+
+       /* Lookup event by name */
+       desc = event->desc;
+       if (!desc)
+               return -EINVAL;
+       fields = desc->fields;
+       if (!fields)
+               return -EINVAL;
+       nr_fields = desc->nr_fields;
+       for (i = 0; i < nr_fields; i++) {
+               if (!strcmp(fields[i].name, field_name)) {
+                       field = &fields[i];
+                       break;
+               }
+               /* compute field offset */
+               switch (fields[i].type.atype) {
+               case atype_integer:
+               case atype_enum:
+                       field_offset += sizeof(int64_t);
+                       break;
+               case atype_array:
+               case atype_sequence:
+                       field_offset += sizeof(unsigned long);
+                       field_offset += sizeof(void *);
+                       break;
+               case atype_string:
+                       field_offset += sizeof(void *);
+                       break;
+               case atype_float:
+                       field_offset += sizeof(double);
+               default:
+                       return -EINVAL;
+               }
+       }
+       if (!field)
+               return -EINVAL;
+
+       /* Check if field offset is too large for 16-bit offset */
+       if (field_offset > FILTER_BYTECODE_MAX_LEN)
+               return -EINVAL;
+
+       /* set type */
+       field_ref = (struct field_ref *) &runtime->data[reloc_offset];
+       switch (field->type.atype) {
+       case atype_integer:
+       case atype_enum:
+               field_ref->type = FIELD_REF_S64;
+               field_ref->type = FIELD_REF_S64;
+               break;
+       case atype_array:
+       case atype_sequence:
+               field_ref->type = FIELD_REF_SEQUENCE;
+               break;
+       case atype_string:
+               field_ref->type = FIELD_REF_STRING;
+               break;
+       case atype_float:
+               return -EINVAL;
+       default:
+               return -EINVAL;
+       }
+       /* set offset */
+       field_ref->offset = (uint16_t) field_offset;
        return 0;
 }
 
+/*
+ * Take a bytecode with reloc table and link it to an event to create a
+ * bytecode runtime.
+ */
 static
 int _lttng_filter_event_link_bytecode(struct ltt_event *event,
                struct lttng_ust_filter_bytecode *filter_bytecode)
 {
+       int ret, offset, next_offset;
+       struct bytecode_runtime *runtime = NULL;
+       size_t runtime_alloc_len;
+
        if (!filter_bytecode)
                return 0;
+       /* Even is not connected to any description */
+       if (!event->desc)
+               return 0;
+       /* Bytecode already linked */
+       if (event->filter || event->filter_data)
+               return 0;
 
+       fprintf(stderr, "Linking\n");
+
+       /* We don't need the reloc table in the runtime */
+       runtime_alloc_len = sizeof(*runtime) + filter_bytecode->reloc_offset;
+       runtime = zmalloc(runtime_alloc_len);
+       if (!runtime) {
+               ret = -ENOMEM;
+               goto link_error;
+       }
+       runtime->len = filter_bytecode->reloc_offset;
+       /* copy original bytecode */
+       memcpy(runtime->data, filter_bytecode->data, runtime->len);
+       /*
+        * apply relocs. Those are a uint16_t (offset in bytecode)
+        * followed by a string (field name).
+        */
+       fprintf(stderr, "iter for %d %d\n", filter_bytecode->reloc_offset, filter_bytecode->len);
+       for (offset = filter_bytecode->reloc_offset;
+                       offset < filter_bytecode->len;
+                       offset = next_offset) {
+               uint16_t reloc_offset =
+                       *(uint16_t *) &filter_bytecode->data[offset];
+               const char *field_name =
+                       (const char *) &filter_bytecode->data[offset + sizeof(uint16_t)];
+
+               ret = apply_field_reloc(event, runtime, runtime->len, reloc_offset, field_name);
+               if (ret) {
+                       goto link_error;
+               }
+               next_offset = offset + sizeof(uint16_t) + strlen(field_name) + 1;
+       }
+       event->filter_data = runtime;
        event->filter = lttng_filter_interpret_bytecode;
-       /* TODO */
-       /* event->filter_data = ; */
        return 0;
+
+link_error:
+       event->filter = lttng_filter_false;
+       free(runtime);
+       return ret;
 }
 
 void lttng_filter_event_link_bytecode(struct ltt_event *event,
@@ -51,7 +787,7 @@ void lttng_filter_event_link_bytecode(struct ltt_event *event,
 {
        int ret;
 
-       ret = _lttng_filter_event_link_bytecode(event, event->filter_bytecode);
+       ret = _lttng_filter_event_link_bytecode(event, filter_bytecode);
        if (ret) {
                fprintf(stderr, "[lttng filter] error linking event bytecode\n");
        }
@@ -86,44 +822,30 @@ void lttng_filter_wildcard_link_bytecode(struct session_wildcard *wildcard)
 
 /*
  * Need to attach filter to an event before starting tracing for the
- * session.
+ * session. We own the filter_bytecode if we return success.
  */
 int lttng_filter_event_attach_bytecode(struct ltt_event *event,
                struct lttng_ust_filter_bytecode *filter_bytecode)
 {
-       struct lttng_ust_filter_bytecode *bc;
-
        if (event->chan->session->been_active)
                return -EPERM;
        if (event->filter_bytecode)
                return -EEXIST;
-
-       bc = zmalloc(sizeof(struct lttng_ust_filter_bytecode)
-                       + filter_bytecode->len);
-       if (!bc)
-               return -ENOMEM;
-       event->filter_bytecode = bc;
+       event->filter_bytecode = filter_bytecode;
        return 0;
 }
 
 /*
  * Need to attach filter to a wildcard before starting tracing for the
- * session.
+ * session. We own the filter_bytecode if we return success.
  */
 int lttng_filter_wildcard_attach_bytecode(struct session_wildcard *wildcard,
                struct lttng_ust_filter_bytecode *filter_bytecode)
 {
-       struct lttng_ust_filter_bytecode *bc;
-
        if (wildcard->chan->session->been_active)
                return -EPERM;
        if (wildcard->filter_bytecode)
                return -EEXIST;
-
-       bc = zmalloc(sizeof(struct lttng_ust_filter_bytecode)
-                       + filter_bytecode->len);
-       if (!bc)
-               return -ENOMEM;
-       wildcard->filter_bytecode = bc;
+       wildcard->filter_bytecode = filter_bytecode;
        return 0;
 }
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