Parse SPDX License IDs from scripts

IDs representing a GPL v2 license are translated into "GPL" to be
recognised by the kernel.

Licenses defined in a BpfScript config block take precedence over SPDX
IDs.

man/adoc/bpftrace.adoc

@@ -53,7 +53,11 @@ x86_64, arm64, s390x, arm32, loongarch64, mips64, ppc64, riscv64
 
 The license of a bpftrace script affects how it can be run, as the Linux kernel limits the functionality available to non-GPL licensed programs.
 
-A license can be specified by setting the <<license>> config variable.
+A license can be specified by setting the <<license>> config variable or by including a single-line comment containing a SPDX License ID:
+
+----
+// SPDX-License-Identifier: GPL-2.0-or-later
+----
 
 If a license is not explicitly declared, bpftrace will assume that the script is GPL v2 compatible.
 

src/driver.cpp

@@ -12,6 +12,31 @@ extern bpftrace::location loc;
 
 namespace bpftrace {
 
+namespace {
+std::string_view parse_license()
+{
+  std::string_view program = Log::get().get_source();
+  constexpr std::string_view spdx_id_marker = "SPDX-License-Identifier: ";
+  auto spdx_id_pos = program.find(spdx_id_marker);
+  if (spdx_id_pos == program.npos)
+    return {};
+
+  auto license_pos = spdx_id_pos + spdx_id_marker.size();
+  auto eol_pos = program.find("\n", spdx_id_pos + 1);
+  if (eol_pos == program.npos)
+    return {};
+
+  auto license = program.substr(license_pos, eol_pos - license_pos);
+
+  // Try to translate some known GPL-v2-compatible licenses into a format
+  // understood by the Linux kernel
+  if (license.find("GPL-2.0") == 0)
+    return "GPL";
+
+  return license;
+}
+} // namespace
+
 Driver::Driver(BPFtrace &bpftrace, std::ostream &o)
     : bpftrace_(bpftrace), out_(o)
 {
@@ -31,6 +56,12 @@ int Driver::parse_str(std::string_view script)
 
 int Driver::parse()
 {
+  if (auto license = parse_license(); !license.empty()) {
+    LOG(V1) << "Found license from SPDX ID: " << license;
+    ConfigSetter config_setter(bpftrace_.config_, ConfigSource::default_);
+    config_setter.set(ConfigKeyString::license, std::string{ license });
+  }
+
   // Reset previous state if we parse more than once
   root.reset();
 

tests/CMakeLists.txt

@@ -31,6 +31,7 @@ add_executable(bpftrace_test
   mocks.cpp
   output.cpp
   parser.cpp
+  parser_licenses.cpp
   portability_analyser.cpp
   procmon.cpp
   probe.cpp

tests/parser_licenses.cpp

@@ -0,0 +1,65 @@
+#include <optional>
+#include <string>
+#include <string_view>
+
+#include "bpftrace.h"
+#include "driver.h"
+#include "gtest/gtest.h"
+
+namespace bpftrace::test::parser_licenses {
+
+void test(std::string_view input, std::optional<std::string> expected_license)
+{
+  BPFtrace bpftrace;
+  Driver driver{ bpftrace };
+  ASSERT_EQ(0, driver.parse_str(input));
+  EXPECT_EQ(expected_license,
+            bpftrace.config_.try_get(ConfigKeyString::license));
+}
+
+TEST(ParserLicenses, GPL_v2_only)
+{
+  test(R"(
+// SPDX-License-Identifier: GPL-2.0-only
+BEGIN {}
+)",
+       "GPL");
+}
+
+TEST(ParserLicenses, GPL_v2_or_later)
+{
+  test(R"(
+// SPDX-License-Identifier: GPL-2.0-or-later
+BEGIN {}
+)",
+       "GPL");
+}
+
+TEST(ParserLicenses, GPL_v1)
+{
+  test(R"(
+// SPDX-License-Identifier: GPL-1.0-only
+BEGIN {}
+)",
+       "GPL-1.0-only");
+}
+
+TEST(ParserLicenses, GPL_v3)
+{
+  test(R"(
+// SPDX-License-Identifier: GPL-3.0-only
+BEGIN {}
+)",
+       "GPL-3.0-only");
+}
+
+TEST(ParserLicenses, Apache_2)
+{
+  test(R"(
+// SPDX-License-Identifier: Apache-2.0
+BEGIN {}
+)",
+       "Apache-2.0");
+}
+
+} // namespace bpftrace::test::parser_licenses

tests/runtime/license

@@ -16,3 +16,24 @@ EXPECT stdin:1:51-57: ERROR: helper bpf_probe_read_str can only be used in GPL-c
 TIMEOUT 5
 WILL_FAIL
 
+NAME spdx_allowed
+PROG // SPDX-License-Identifier: GPL-2.0-or-later
+     BEGIN { printf("\"%s\"\n", str(0)); exit(); }
+EXPECT ""
+TIMEOUT 5
+
+NAME spdx_not_allowed
+PROG // SPDX-License-Identifier: Apache-2.0
+     BEGIN { printf("%s\n", str(0)); }
+EXPECT stdin:2:24-30: ERROR: helper bpf_probe_read_str can only be used in GPL-compatible programs
+       BEGIN { printf("%s\n", str(0)); }
+                              ~~~~~~
+TIMEOUT 5
+WILL_FAIL
+
+NAME config_override_spdx
+PROG // SPDX-License-Identifier: Some-unknown-GPL-compatible-license
+     config = { license = "GPL" }
+     BEGIN { printf("\"%s\"\n", str(0)); exit(); }
+EXPECT ""
+TIMEOUT 5