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WIP: Support external stacks and local function calls using local memory
1. Add support for invoking the interpreter and JIT'd code with an external stack. This feature is generally useful and will also make it easier to fuzz the runtime and check for correctness. 2. Add support for local functions that use local memory. Prior to this commit, a local function could be called but could not use any local memory (without overwriting memory from another function). Signed-off-by: Will Hawkins <hawkinsw@obs.cr>
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## Test Description | ||
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This custom test program tests whether it is possible to update the external helper | ||
functions for an eBPF program that has already been JIT'd. |
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// Copyright (c) Will Hawkins | ||
// SPDX-License-Identifier: Apache-2.0 | ||
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#include <cstdint> | ||
#include <iostream> | ||
#include <memory> | ||
#include <stdint.h> | ||
#include <vector> | ||
#include <string> | ||
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extern "C" | ||
{ | ||
#include "ubpf.h" | ||
} | ||
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#include "ubpf_custom_test_support.h" | ||
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int | ||
stack_usage_calculator(const struct ubpf_vm *vm, uint16_t pc, void *cookie) | ||
{ | ||
UNREFERENCED_PARAMETER(vm); | ||
UNREFERENCED_PARAMETER(pc); | ||
UNREFERENCED_PARAMETER(cookie); | ||
return 16; | ||
} | ||
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int | ||
overwrite_stack_usage_calculator(const struct ubpf_vm *vm, uint16_t pc, void *cookie) | ||
{ | ||
UNREFERENCED_PARAMETER(vm); | ||
UNREFERENCED_PARAMETER(pc); | ||
UNREFERENCED_PARAMETER(cookie); | ||
return 0; | ||
} | ||
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int main(int argc, char **argv) | ||
{ | ||
std::vector<std::string> args(argv, argv + argc); | ||
std::string program_string{}; | ||
ubpf_jit_fn jit_fn; | ||
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std::getline(std::cin, program_string); | ||
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uint64_t no_overwrite_interp_result = 0; | ||
uint64_t no_overwrite_jit_result = 0; | ||
uint64_t overwrite_interp_result = 0; | ||
uint64_t overwrite_jit_result = 0; | ||
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{ | ||
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std::unique_ptr<ubpf_vm, decltype(&ubpf_destroy)> vm(ubpf_create(), ubpf_destroy); | ||
std::string error{}; | ||
if (!ubpf_setup_custom_test( | ||
vm, | ||
program_string, | ||
[](ubpf_vm_up& vm, std::string& error) { | ||
if (ubpf_register_stack_usage_calculator(vm.get(), stack_usage_calculator, nullptr) < 0) { | ||
error = "Failed to register stack usage calculator."; | ||
return false; | ||
} | ||
return true; | ||
}, | ||
jit_fn, | ||
error)) { | ||
std::cerr << "Problem setting up custom test: " << error << std::endl; | ||
return 1; | ||
} | ||
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no_overwrite_jit_result = jit_fn(nullptr, 0); | ||
[[maybe_unused]] auto exec_result = ubpf_exec(vm.get(), NULL, 0, &no_overwrite_interp_result); | ||
} | ||
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{ | ||
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std::unique_ptr<ubpf_vm, decltype(&ubpf_destroy)> vm(ubpf_create(), ubpf_destroy); | ||
std::string error{}; | ||
if (!ubpf_setup_custom_test( | ||
vm, | ||
program_string, | ||
[](ubpf_vm_up& vm, std::string& error) { | ||
if (ubpf_register_stack_usage_calculator(vm.get(), overwrite_stack_usage_calculator, nullptr) < 0) { | ||
error = "Failed to register stack usage calculator."; | ||
return false; | ||
} | ||
return true; | ||
}, | ||
jit_fn, | ||
error)) { | ||
std::cerr << "Problem setting up custom test: " << error << std::endl; | ||
return 1; | ||
} | ||
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overwrite_jit_result = jit_fn(nullptr, 0); | ||
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[[maybe_unused]] auto exec_result = ubpf_exec(vm.get(), NULL, 0, &overwrite_interp_result); | ||
} | ||
// ... because of the semantics of external_dispatcher, the result of the eBPF | ||
// program execution should point to the same place to which &memory points. | ||
return !(no_overwrite_interp_result == no_overwrite_jit_result && | ||
no_overwrite_interp_result == 0x5 && | ||
overwrite_interp_result == overwrite_jit_result && | ||
overwrite_interp_result == 0x37); | ||
} |
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