Merge branch 'master' of github.com:iovisor/bpftrace

* 'master' of github.com:iovisor/bpftrace:
  Prevent crash with /proc path canonicalization (bpftrace#1637)

CHANGELOG.md

@@ -116,6 +116,8 @@ and this project adheres to
   - [#1622](https://github.com/iovisor/bpftrace/pull/1622)
 - Check exponent value can be expressed in uint64_t
   - [#1623](https://github.com/iovisor/bpftrace/pull/1623)
+- Fix tracing of usdt probes across namespaces
+  - [#1637](https://github.com/iovisor/bpftrace/pull/1637)
 
 #### Tools
 - Hook up execsnoop.bt script onto `execveat` call

src/utils.cpp

@@ -928,8 +928,19 @@ uint32_t kernel_version(int attempt)
 
 std::string abs_path(const std::string &rel_path)
 {
-  auto p = std_filesystem::path(rel_path);
-  return std_filesystem::canonical(std_filesystem::absolute(p)).string();
+  // filesystem::canonical does not work very well with /proc/<pid>/root paths
+  // of processes in a different mount namespace (than the one bpftrace is
+  // running in), failing during canonicalization. See iovisor:bpftrace#1595
+  static auto re = std::regex("^/proc/\\d+/root/.*");
+  if (!std::regex_match(rel_path, re))
+  {
+    auto p = std_filesystem::path(rel_path);
+    return std_filesystem::canonical(std_filesystem::absolute(p)).string();
+  }
+  else
+  {
+    return rel_path;
+  }
 }
 
 } // namespace bpftrace

tests/utils.cpp

@@ -87,6 +87,17 @@ static void symlink_test_binary(const std::string& destination)
   }
 }
 
+static std::string get_working_path()
+{
+  char cwd_path[PATH_MAX];
+  if (::getcwd(cwd_path, PATH_MAX) == nullptr)
+  {
+    throw std::runtime_error(
+        "getting current working directory for tests failed");
+  }
+  return std::string(cwd_path);
+}
+
 TEST(utils, resolve_binary_path)
 {
   std::string path = "/tmp/bpftrace-test-utils-XXXXXX";
@@ -131,6 +142,35 @@ TEST(utils, parse_exponent)
   EXPECT_EQ(parse_exponent((const char*)"2a9"), 2ULL);
 }
 
+TEST(utils, abs_path)
+{
+  std::string path = "/tmp/bpftrace-test-utils-XXXXXX";
+  std::string rel_file = "bpftrace-test-utils-abs-path";
+  if (::mkdtemp(&path[0]) == nullptr)
+  {
+    throw std::runtime_error("creating temporary path for tests failed");
+  }
+
+  int fd;
+  fd = open((path + "/somefile").c_str(), O_CREAT, S_IRUSR);
+  close(fd);
+  fd = open(rel_file.c_str(), O_CREAT, S_IRUSR);
+  close(fd);
+
+  // Translates absolute path with '../..'
+  EXPECT_EQ(abs_path(path + "/../.." + path + "/somefile"), path + "/somefile");
+  // Translates relative path with './'
+  EXPECT_EQ(abs_path("./" + rel_file), get_working_path() + "/" + rel_file);
+
+  // /proc/<pid>/root path returned as is (and doesn't throw)
+  EXPECT_NO_THROW(
+      abs_path(std::string("/proc/1/root/usr/local/bin/usdt_test.so")));
+  EXPECT_EQ(abs_path(std::string("/proc/1/root/usr/local/bin/usdt_test.so")),
+            std::string("/proc/1/root/usr/local/bin/usdt_test.so"));
+
+  remove(rel_file.c_str());
+}
+
 } // namespace utils
 } // namespace test
 } // namespace bpftrace