Validate specific atomic operation opcodes

custom_tests/data/ubpf_test_atomic_validate.input

@@ -0,0 +1 @@
+b4  00  00  00  00  00  00  00 db  01  00  00  42  00  00  00 95  00  00  00  00  00  00  00 

custom_tests/descrs/ubpf_test_atomic_validate.md

@@ -0,0 +1,3 @@
+## Test Description
+
+This test verifies that the check for to validate an instruction properly handles the case where an atomic operation's immediate field does not contain a valid operation (according to Table 11 in the [spec](https://www.ietf.org/archive/id/draft-thaler-bpf-isa-00.html).

custom_tests/srcs/ubpf_test_atomic_validate.cc

@@ -0,0 +1,51 @@
+// Copyright (c) Will Hawkins
+// SPDX-License-Identifier: Apache-2.0
+
+#include <cstdint>
+#include <iostream>
+#include <memory>
+#include <stdint.h>
+#include <string>
+
+extern "C"
+{
+#include "ubpf.h"
+}
+
+#include "ubpf_custom_test_support.h"
+
+int
+main(int argc, char** argv)
+{
+    std::string program_string{};
+    std::string error{};
+    ubpf_jit_fn jit_fn;
+
+    if (!get_program_string(argc, argv, program_string, error)) {
+        std::cerr << error << std::endl;
+        return 1;
+    }
+
+    uint64_t memory_expected{0x123456789};
+    uint64_t memory{0x123456789};
+
+    std::unique_ptr<ubpf_vm, decltype(&ubpf_destroy)> vm(ubpf_create(), ubpf_destroy);
+    if (!ubpf_setup_custom_test(
+            vm, program_string, [](ubpf_vm_up&, std::string&) { return true; }, jit_fn, error)) {
+        if (error == "Failed to load program: Invalid immediate value 66 for opcode DB.") {
+            return 0;
+        }
+
+        return 1;
+    }
+
+    return 1;
+
+    uint64_t bpf_return_value;
+    if (ubpf_exec(vm.get(), &memory, sizeof(memory), &bpf_return_value)) {
+        std::cerr << "Problem executing program" << std::endl;
+        return 1;
+    }
+
+    return !(memory == memory_expected);
+}

vm/ubpf_instruction_valid.c

@@ -9,18 +9,32 @@
  * @brief Structure to filter valid fields for each eBPF instruction.
  * Default values are all zeros, which means the field is reserved and must be zero.
  */
-typedef struct _ubpf_inst_filter {
-    uint8_t opcode; ///< The opcode of the instruction.
-    uint8_t source_lower_bound; ///< The lower bound of the source register.
-    uint8_t source_upper_bound; ///< The upper bound of the source register.
-    uint8_t destination_lower_bound; ///< The lower bound of the destination register.
-    uint8_t destination_upper_bound; ///< The upper bound of the destination register.
-    int16_t offset_lower_bound; ///< The lower bound of the offset.
-    int16_t offset_upper_bound; ///< The upper bound of the offset.
-    int32_t immediate_lower_bound; ///< The lower bound of the immediate value.
-    int32_t immediate_upper_bound; ///< The upper bound of the immediate value.
+typedef struct _ubpf_inst_filter
+{
+    uint8_t opcode;                       ///< The opcode of the instruction.
+    uint8_t source_lower_bound;           ///< The lower bound of the source register.
+    uint8_t source_upper_bound;           ///< The upper bound of the source register.
+    uint8_t destination_lower_bound;      ///< The lower bound of the destination register.
+    uint8_t destination_upper_bound;      ///< The upper bound of the destination register.
+    int16_t offset_lower_bound;           ///< The lower bound of the offset.
+    int16_t offset_upper_bound;           ///< The upper bound of the offset.
+    int32_t immediate_lower_bound;        ///< The lower bound of the immediate value.
+    int32_t immediate_upper_bound;        ///< The upper bound of the immediate value.
+    int32_t* immediate_enumerated;        ///< A specific enumeration of the valid immediate values.
+    uint32_t immediate_enumerated_length; ///< The number of valid enumerated immediate values.
 } ubpf_inst_filter_t;
 
+static int32_t ebpf_atomic_store_immediate_enumerated[] = {
+    EBPF_ALU_OP_ADD,
+    EBPF_ALU_OP_ADD | EBPF_ATOMIC_OP_FETCH,
+    EBPF_ALU_OP_OR,
+    EBPF_ALU_OP_OR | EBPF_ATOMIC_OP_FETCH,
+    EBPF_ALU_OP_AND,
+    EBPF_ALU_OP_AND | EBPF_ATOMIC_OP_FETCH,
+    EBPF_ALU_OP_XOR,
+    EBPF_ALU_OP_XOR | EBPF_ATOMIC_OP_FETCH,
+    EBPF_ATOMIC_OP_XCHG | EBPF_ATOMIC_OP_FETCH,
+    EBPF_ATOMIC_OP_CMPXCHG | EBPF_ATOMIC_OP_FETCH};
 
 /**
  * @brief Array of valid eBPF instructions and their fields.
@@ -208,13 +222,15 @@ static ubpf_inst_filter_t _ubpf_instruction_filter[] = {
         .opcode = EBPF_OP_LE,
         .destination_lower_bound = BPF_REG_0,
         .destination_upper_bound = BPF_REG_9,
+        // specific valid values for the immediate field are checked in validate.
         .immediate_lower_bound = 0,
         .immediate_upper_bound = 64,
     },
     {
         .opcode = EBPF_OP_BE,
         .destination_lower_bound = BPF_REG_0,
         .destination_upper_bound = BPF_REG_9,
+        // specific valid values for the immediate field are checked in validate.
         .immediate_lower_bound = 0,
         .immediate_upper_bound = 64,
     },
@@ -503,6 +519,9 @@ static ubpf_inst_filter_t _ubpf_instruction_filter[] = {
         .opcode = EBPF_OP_LDDW,
         .destination_lower_bound = BPF_REG_0,
         .destination_upper_bound = BPF_REG_10,
+        // specific valid source values are checked in validate.
+        .source_lower_bound = 0,
+        .source_upper_bound = 6,
         .immediate_lower_bound = INT32_MIN,
         .immediate_upper_bound = INT32_MAX,
     },
@@ -934,8 +953,8 @@ static ubpf_inst_filter_t _ubpf_instruction_filter[] = {
         .destination_upper_bound = BPF_REG_10,
         .source_lower_bound = BPF_REG_0,
         .source_upper_bound = BPF_REG_10,
-        .immediate_lower_bound = 0x0,
-        .immediate_upper_bound = 0xff,
+        .immediate_enumerated = ebpf_atomic_store_immediate_enumerated,
+        .immediate_enumerated_length = 10,
         .offset_lower_bound = INT16_MIN,
         .offset_upper_bound = INT16_MAX,
     },
@@ -994,10 +1013,25 @@ ubpf_is_valid_instruction(const struct ebpf_inst insts, char ** errmsg)
         return false;
     }
 
-    // Validate immediate value.
-    if (!_in_range(insts.imm, filter->immediate_lower_bound, filter->immediate_upper_bound)) {
-        *errmsg = ubpf_error("Invalid immediate value %d for opcode %2X.", insts.imm, insts.opcode);
-        return false;
+    // Validate immediate values in the presence of enumerated values.
+    if (filter->immediate_enumerated != NULL) {
+        bool valid = false;
+        for (int i = 0; i < filter->immediate_enumerated_length; i++) {
+            if (filter->immediate_enumerated[i] == insts.imm) {
+                valid = true;
+                break;
+            }
+        }
+        if (!valid) {
+            *errmsg = ubpf_error("Invalid immediate value %d for opcode %2X.", insts.imm, insts.opcode);
+            return false;
+        }
+    } else {
+        // Validate immediate value.
+        if (!_in_range(insts.imm, filter->immediate_lower_bound, filter->immediate_upper_bound)) {
+            *errmsg = ubpf_error("Invalid immediate value %d for opcode %2X.", insts.imm, insts.opcode);
+            return false;
+        }
     }
 
     // Validate offset value.