Better error handling in stacktraces

PiperOrigin-RevId: 380789060
Change-Id: I655428fd45bf305f787b75cc925d31c6ab60c074

sandboxed_api/sandbox2/monitor.cc

@@ -68,6 +68,7 @@
 #include "sandboxed_api/sandbox2/util.h"
 #include "sandboxed_api/util/file_helpers.h"
 #include "sandboxed_api/util/raw_logging.h"
+#include "sandboxed_api/util/status_macros.h"
 #include "sandboxed_api/util/temp_file.h"
 
 using std::string;
@@ -373,8 +374,15 @@ void Monitor::SetAdditionalResultInfo(std::unique_ptr<Regs> regs) {
   }
   auto* ns = policy_->GetNamespace();
   const Mounts empty_mounts;
-  result_.set_stack_trace(
+  absl::StatusOr<std::vector<std::string>> stack_trace =
-      GetStackTrace(result_.GetRegs(), ns ? ns->mounts() : empty_mounts));
+      GetStackTrace(result_.GetRegs(), ns ? ns->mounts() : empty_mounts);
+
+  if (!stack_trace.ok()) {
+    LOG(ERROR) << "Could not obtain stack trace: " << stack_trace.status();
+    return;
+  }
+
+  result_.set_stack_trace(*stack_trace);
 
   LOG(INFO) << "Stack trace: [";
   for (const auto& frame : CompactStackTrace(result_.stack_trace())) {
@@ -936,13 +944,18 @@ void Monitor::StateProcessStopped(pid_t pid, int status) {
   if (ABSL_PREDICT_FALSE(pid == pid_ && should_dump_stack_ &&
                          executor_->libunwind_sbox_for_pid_ == 0 &&
                          policy_->GetNamespace())) {
+    auto stack_trace = [this,
+                        pid]() -> absl::StatusOr<std::vector<std::string>> {
       Regs regs(pid);
-    if (auto status = regs.Fetch(); !status.ok()) {
+      SAPI_RETURN_IF_ERROR(regs.Fetch());
-      LOG(WARNING) << "FAILED TO GET SANDBOX STACK : " << status;
+      return GetStackTrace(&regs, policy_->GetNamespace()->mounts());
+    }();
+
+    if (!stack_trace.ok()) {
+      LOG(WARNING) << "FAILED TO GET SANDBOX STACK : " << stack_trace.status();
     } else if (SAPI_VLOG_IS_ON(0)) {
       VLOG(0) << "SANDBOX STACK: PID: " << pid << ", [";
-      for (const auto& frame :
+      for (const auto& frame : *stack_trace) {
-           GetStackTrace(&regs, policy_->GetNamespace()->mounts())) {
         VLOG(0) << "  " << frame;
       }
       VLOG(0) << "]";

sandboxed_api/sandbox2/stack_trace.cc

@@ -24,8 +24,10 @@
 #include <vector>
 
 #include <glog/logging.h>
+#include "absl/cleanup/cleanup.h"
 #include "sandboxed_api/util/flag.h"
 #include "absl/memory/memory.h"
+#include "absl/status/status.h"
 #include "absl/strings/numbers.h"
 #include "absl/strings/str_cat.h"
 #include "absl/strings/strip.h"
@@ -45,6 +47,7 @@
 #include "sandboxed_api/sandbox2/util/bpf_helper.h"
 #include "sandboxed_api/util/fileops.h"
 #include "sandboxed_api/util/path.h"
+#include "sandboxed_api/util/status_macros.h"
 
 ABSL_FLAG(bool, sandbox_disable_all_stack_traces, false,
           "Completely disable stack trace collection for sandboxees");
@@ -53,27 +56,34 @@ ABSL_FLAG(bool, sandbox_libunwind_crash_handler, true,
           "Sandbox libunwind when handling violations (preferred)");
 
 namespace sandbox2 {
+namespace {
 
 namespace file = ::sapi::file;
 namespace file_util = ::sapi::file_util;
 
+// Similar to GetStackTrace() but without using the sandbox to isolate
+// libunwind.
+absl::StatusOr<std::vector<std::string>> UnsafeGetStackTrace(pid_t pid) {
+  LOG(WARNING) << "Using non-sandboxed libunwind";
+  return RunLibUnwindAndSymbolizer(pid, kDefaultMaxFrames);
+}
+
+}  // namespace
+
 class StackTracePeer {
  public:
-  static std::unique_ptr<Policy> GetPolicy(pid_t target_pid,
+  static absl::StatusOr<std::unique_ptr<Policy>> GetPolicy(
-                                           const std::string& maps_file,
+      pid_t target_pid, const std::string& maps_file,
-                                           const std::string& app_path,
+      const std::string& app_path, const std::string& exe_path,
-                                           const std::string& exe_path,
       const Mounts& mounts);
 
-  static bool LaunchLibunwindSandbox(const Regs* regs, const Mounts& mounts,
+  static absl::StatusOr<UnwindResult> LaunchLibunwindSandbox(
-                                     UnwindResult* result);
+      const Regs* regs, const Mounts& mounts);
 };
 
-std::unique_ptr<Policy> StackTracePeer::GetPolicy(pid_t target_pid,
+absl::StatusOr<std::unique_ptr<Policy>> StackTracePeer::GetPolicy(
-                                                  const std::string& maps_file,
+    pid_t target_pid, const std::string& maps_file, const std::string& app_path,
-                                                  const std::string& app_path,
+    const std::string& exe_path, const Mounts& mounts) {
-                                                  const std::string& exe_path,
-                                                  const Mounts& mounts) {
   PolicyBuilder builder;
   builder
       // Use the mounttree of the original executable as starting point.
@@ -147,23 +157,18 @@ std::unique_ptr<Policy> StackTracePeer::GetPolicy(pid_t target_pid,
     }
   }
 
-  auto policy = builder.TryBuild();
+  SAPI_ASSIGN_OR_RETURN(std::unique_ptr<Policy> policy, builder.TryBuild());
-  if (!policy.ok()) {
-    LOG(ERROR) << "Creating stack unwinder sandbox policy failed";
-    return nullptr;
-  }
   auto keep_capabilities = absl::make_unique<std::vector<int>>();
   keep_capabilities->push_back(CAP_SYS_PTRACE);
-  (*policy)->AllowUnsafeKeepCapabilities(std::move(keep_capabilities));
+  policy->AllowUnsafeKeepCapabilities(std::move(keep_capabilities));
   // Use no special namespace flags when cloning. We will join an existing
   // user namespace and will unshare() afterwards (See forkserver.cc).
-  (*policy)->GetNamespace()->clone_flags_ = 0;
+  policy->GetNamespace()->clone_flags_ = 0;
-  return std::move(*policy);
+  return std::move(policy);
 }
 
-bool StackTracePeer::LaunchLibunwindSandbox(const Regs* regs,
+absl::StatusOr<UnwindResult> StackTracePeer::LaunchLibunwindSandbox(
-                                            const Mounts& mounts,
+    const Regs* regs, const Mounts& mounts) {
-                                            sandbox2::UnwindResult* result) {
   const pid_t pid = regs->pid();
 
   // Tell executor to use this special internal mode.
@@ -183,8 +188,8 @@ bool StackTracePeer::LaunchLibunwindSandbox(const Regs* regs,
   char unwind_temp_directory_template[] = "/tmp/.sandbox2_unwind_XXXXXX";
   char* unwind_temp_directory = mkdtemp(unwind_temp_directory_template);
   if (!unwind_temp_directory) {
-    LOG(WARNING) << "Could not create temporary directory for unwinding";
+    return absl::InternalError(
-    return false;
+        "Could not create temporary directory for unwinding");
   }
   struct UnwindTempDirectoryCleanup {
     ~UnwindTempDirectoryCleanup() {
@@ -200,8 +205,7 @@ bool StackTracePeer::LaunchLibunwindSandbox(const Regs* regs,
   if (!file_util::fileops::CopyFile(
           file::JoinPath("/proc", absl::StrCat(pid), "maps"),
           unwind_temp_maps_path, 0400)) {
-    LOG(WARNING) << "Could not copy maps file";
+    return absl::InternalError("Could not copy maps file");
-    return false;
   }
 
   // Get path to the binary.
@@ -211,8 +215,7 @@ bool StackTracePeer::LaunchLibunwindSandbox(const Regs* regs,
   std::string app_path;
   std::string proc_pid_exe = file::JoinPath("/proc", absl::StrCat(pid), "exe");
   if (!file_util::fileops::ReadLinkAbsolute(proc_pid_exe, &app_path)) {
-    LOG(WARNING) << "Could not obtain absolute path to the binary";
+    return absl::InternalError("Could not obtain absolute path to the binary");
-    return false;
   }
 
   // The exe_path will have a mountable path of the application, even if it was
@@ -227,8 +230,7 @@ bool StackTracePeer::LaunchLibunwindSandbox(const Regs* regs,
     // Create a copy of /proc/pid/exe, mount that one.
     exe_path = file::JoinPath(unwind_temp_directory, "exe");
     if (!file_util::fileops::CopyFile(proc_pid_exe, exe_path, 0700)) {
-      LOG(WARNING) << "Could not copy /proc/pid/exe";
+      return absl::InternalError("Could not copy /proc/pid/exe");
-      return false;
     }
   }
 
@@ -236,11 +238,9 @@ bool StackTracePeer::LaunchLibunwindSandbox(const Regs* regs,
 
   // Add mappings for the binary (as they might not have been added due to the
   // forkserver).
-  auto policy = StackTracePeer::GetPolicy(pid, unwind_temp_maps_path, app_path,
+  SAPI_ASSIGN_OR_RETURN(std::unique_ptr<Policy> policy,
-                                          exe_path, mounts);
+                        StackTracePeer::GetPolicy(pid, unwind_temp_maps_path,
-  if (!policy) {
+                                                  app_path, exe_path, mounts));
-    return false;
-  }
   Sandbox2 sandbox(std::move(executor), std::move(policy));
 
   VLOG(1) << "Running libunwind sandbox";
@@ -253,37 +253,53 @@ bool StackTracePeer::LaunchLibunwindSandbox(const Regs* regs,
                sizeof(regs->user_regs_));
   msg.set_default_max_frames(kDefaultMaxFrames);
 
-  bool success = true;
+  absl::Cleanup kill_sandbox = [&sandbox]() {
-  if (!comms->SendProtoBuf(msg)) {
-    LOG(ERROR) << "Sending libunwind setup message failed";
-    success = false;
-  }
-
-  if (success && !comms->RecvProtoBuf(result)) {
-    LOG(ERROR) << "Receiving libunwind result failed";
-    success = false;
-  }
-
-  if (!success) {
     sandbox.Kill();
+    sandbox.AwaitResult().IgnoreResult();
+  };
+
+  if (!comms->SendProtoBuf(msg)) {
+    return absl::InternalError("Sending libunwind setup message failed");
   }
+  absl::Status status;
+  if (!comms->RecvStatus(&status)) {
+    return absl::InternalError(
+        "Receiving status from libunwind sandbox failed");
+  }
+  if (!status.ok()) {
+    return status;
+  }
+  UnwindResult result;
+  if (!comms->RecvProtoBuf(&result)) {
+    return absl::InternalError("Receiving libunwind result failed");
+  }
+
+  std::move(kill_sandbox).Cancel();
+
   auto sandbox_result = sandbox.AwaitResult();
 
   LOG(INFO) << "Libunwind execution status: " << sandbox_result.ToString();
 
-  return success && sandbox_result.final_status() == Result::OK;
+  if (sandbox_result.final_status() != Result::OK) {
+    return absl::InternalError(
+        absl::StrCat("libunwind sandbox did not finish properly: ",
+                     sandbox_result.ToString()));
   }
 
-std::vector<std::string> GetStackTrace(const Regs* regs, const Mounts& mounts) {
+  return result;
+}
+
+absl::StatusOr<std::vector<std::string>> GetStackTrace(const Regs* regs,
+                                                       const Mounts& mounts) {
   if constexpr (sapi::host_cpu::IsArm64()) {
-    return {"[Stack traces unavailable]"};
+    return absl::UnavailableError("Stack traces unavailable on Aarch64");
   }
   if (absl::GetFlag(FLAGS_sandbox_disable_all_stack_traces)) {
-    return {"[Stacktraces disabled]"};
+    return absl::UnavailableError("Stacktraces disabled");
   }
   if (!regs) {
-    LOG(WARNING) << "Could not obtain stacktrace, regs == nullptr";
+    return absl::InvalidArgumentError(
-    return {"[ERROR (noregs)]"};
+        "Could not obtain stacktrace, regs == nullptr");
   }
 
   // Show a warning if sandboxed libunwind is requested but we're running in
@@ -303,17 +319,10 @@ std::vector<std::string> GetStackTrace(const Regs* regs, const Mounts& mounts) {
     return UnsafeGetStackTrace(regs->pid());
   }
 
-  UnwindResult res;
+  SAPI_ASSIGN_OR_RETURN(UnwindResult res,
-  if (!StackTracePeer::LaunchLibunwindSandbox(regs, mounts, &res)) {
+                        StackTracePeer::LaunchLibunwindSandbox(regs, mounts));
-    return {};
+  return std::vector<std::string>(res.stacktrace().begin(),
-  }
+                                  res.stacktrace().end());
-  return {res.stacktrace().begin(), res.stacktrace().end()};
-}
-
-std::vector<std::string> UnsafeGetStackTrace(pid_t pid) {
-  LOG(WARNING) << "Using non-sandboxed libunwind";
-  std::vector<uintptr_t> ips;
-  return RunLibUnwindAndSymbolizer(pid, &ips, kDefaultMaxFrames);
 }
 
 std::vector<std::string> CompactStackTrace(

sandboxed_api/sandbox2/stack_trace.h

@@ -19,15 +19,11 @@
 #ifndef SANDBOXED_API_SANDBOX2_STACK_TRACE_H_
 #define SANDBOXED_API_SANDBOX2_STACK_TRACE_H_
 
-#include <sys/types.h>
-
-#include <cstddef>
-#include <memory>
 #include <string>
 #include <vector>
 
+#include "absl/status/statusor.h"
 #include "sandboxed_api/sandbox2/mounts.h"
-#include "sandboxed_api/sandbox2/policy.h"
 #include "sandboxed_api/sandbox2/regs.h"
 
 namespace sandbox2 {
@@ -36,11 +32,8 @@ namespace sandbox2 {
 constexpr size_t kDefaultMaxFrames = 200;
 
 // Returns the stack-trace of the PID=pid, one line per frame.
-std::vector<std::string> GetStackTrace(const Regs* regs, const Mounts& mounts);
+absl::StatusOr<std::vector<std::string>> GetStackTrace(const Regs* regs,
-
+                                                       const Mounts& mounts);
-// Similar to GetStackTrace() but without using the sandbox to isolate
-// libunwind.
-std::vector<std::string> UnsafeGetStackTrace(pid_t pid);
 
 // Returns a stack trace that collapses duplicate stack frames and annotates
 // them with a repetition count.

sandboxed_api/sandbox2/unwind/BUILD.bazel

@@ -59,7 +59,9 @@ cc_library(
         "//sandboxed_api/sandbox2/util:minielf",
         "//sandboxed_api/util:file_helpers",
         "//sandboxed_api/util:raw_logging",
+        "//sandboxed_api/util:status",
         "//sandboxed_api/util:strerror",
+        "@com_google_absl//absl/status:statusor",
         "@com_google_absl//absl/strings",
         "@org_gnu_libunwind//:unwind-ptrace-wrapped",
     ],

sandboxed_api/sandbox2/unwind/CMakeLists.txt

@@ -30,6 +30,7 @@ add_library(sandbox2_unwind STATIC
 )
 add_library(sandbox2::unwind ALIAS sandbox2_unwind)
 target_link_libraries(sandbox2_unwind PRIVATE
+  absl::statusor
   absl::strings
   sandbox2::comms
   sandbox2::maps_parser
@@ -40,6 +41,7 @@ target_link_libraries(sandbox2_unwind PRIVATE
   sapi::base
   sapi::file_helpers
   sapi::raw_logging
+  sapi::status
   unwind::unwind_ptrace_wrapped
 )
 

sandboxed_api/sandbox2/unwind/unwind.cc

@@ -24,6 +24,7 @@
 #include <string>
 #include <vector>
 
+#include "absl/status/statusor.h"
 #include "absl/strings/match.h"
 #include "absl/strings/str_cat.h"
 #include "libunwind-ptrace.h"
@@ -34,6 +35,7 @@
 #include "sandboxed_api/sandbox2/util/minielf.h"
 #include "sandboxed_api/util/file_helpers.h"
 #include "sandboxed_api/util/raw_logging.h"
+#include "sandboxed_api/util/status_macros.h"
 #include "sandboxed_api/util/strerror.h"
 
 namespace sandbox2 {
@@ -73,29 +75,77 @@ std::string GetSymbolAt(const std::map<uint64_t, std::string>& addr_to_symbol,
   return "";
 }
 
-}  // namespace
+absl::StatusOr<std::map<uint64_t, std::string>> LoadSymbolsMap(pid_t pid) {
+  const std::string maps_filename = absl::StrCat("/proc/", pid, "/maps");
+  std::string maps_content;
+  SAPI_RETURN_IF_ERROR(sapi::file::GetContents(maps_filename, &maps_content,
+                                               sapi::file::Defaults()));
 
-std::vector<uintptr_t> GetIPList(pid_t pid, int max_frames) {
+  SAPI_ASSIGN_OR_RETURN(std::vector<MapsEntry> maps,
+                        ParseProcMaps(maps_content));
+
+  // Get symbols for each file entry in the maps entry.
+  // This is not a very efficient way, so we might want to optimize it.
+  std::map<uint64_t, std::string> addr_to_symbol;
+  for (const MapsEntry& entry : maps) {
+    if (!entry.is_executable ||
+        entry.inode == 0 ||  // Only parse file-backed entries
+        entry.path.empty() ||
+        absl::EndsWith(entry.path, " (deleted)")  // Skip deleted files
+    ) {
+      continue;
+    }
+
+    // Store details about start + end of this map.
+    // The maps entries are ordered and thus sorted with increasing adresses.
+    // This means if there is a symbol @ entry.end, it will be overwritten in
+    // the next iteration.
+    addr_to_symbol[entry.start] = absl::StrCat("map:", entry.path);
+    addr_to_symbol[entry.end] = "";
+
+    absl::StatusOr<ElfFile> elf =
+        ElfFile::ParseFromFile(entry.path, ElfFile::kLoadSymbols);
+    if (!elf.ok()) {
+      SAPI_RAW_LOG(WARNING, "Could not load symbols for %s: %s",
+                   entry.path.c_str(),
+                   std::string(elf.status().message()).c_str());
+      continue;
+    }
+
+    for (const ElfFile::Symbol& symbol : elf->symbols()) {
+      if (elf->position_independent()) {
+        if (symbol.address < entry.end - entry.start) {
+          addr_to_symbol[symbol.address + entry.start] = symbol.name;
+        }
+      } else {
+        if (symbol.address >= entry.start && symbol.address < entry.end) {
+          addr_to_symbol[symbol.address] = symbol.name;
+        }
+      }
+    }
+  }
+  return addr_to_symbol;
+}
+
+absl::StatusOr<std::vector<uintptr_t>> RunLibUnwind(pid_t pid, int max_frames) {
   unw_cursor_t cursor;
   static unw_addr_space_t as =
       unw_create_addr_space(&_UPT_accessors, 0 /* byte order */);
   if (as == nullptr) {
-    SAPI_RAW_LOG(WARNING, "unw_create_addr_space() failed");
+    return absl::InternalError("unw_create_addr_space() failed");
-    return {};
   }
 
   std::unique_ptr<struct UPT_info, void (*)(void*)> ui(
       reinterpret_cast<struct UPT_info*>(_UPT_create(pid)), _UPT_destroy);
   if (ui == nullptr) {
-    SAPI_RAW_LOG(WARNING, "_UPT_create() failed");
+    return absl::InternalError("_UPT_create() failed");
-    return {};
   }
 
   int rc = unw_init_remote(&cursor, as, ui.get());
   if (rc < 0) {
     // Could be UNW_EINVAL (8), UNW_EUNSPEC (1) or UNW_EBADREG (3).
-    SAPI_RAW_LOG(WARNING, "unw_init_remote() failed with error %d", rc);
+    return absl::InternalError(
-    return {};
+        absl::StrCat("unw_init_remote() failed with error ", rc));
   }
 
   std::vector<uintptr_t> ips;
@@ -120,6 +170,22 @@ std::vector<uintptr_t> GetIPList(pid_t pid, int max_frames) {
   return ips;
 }
 
+absl::StatusOr<std::vector<std::string>> SymbolizeStacktrace(
+    pid_t pid, const std::vector<uintptr_t>& ips) {
+  SAPI_ASSIGN_OR_RETURN(auto addr_to_symbol, LoadSymbolsMap(pid));
+  std::vector<std::string> stack_trace;
+  stack_trace.reserve(ips.size());
+  // Symbolize stacktrace
+  for (uintptr_t ip : ips) {
+    const std::string symbol =
+        GetSymbolAt(addr_to_symbol, static_cast<uint64_t>(ip));
+    stack_trace.push_back(absl::StrCat(symbol, "(0x", absl::Hex(ip), ")"));
+  }
+  return stack_trace;
+}
+
+}  // namespace
+
 bool RunLibUnwindAndSymbolizer(Comms* comms) {
   UnwindSetup setup;
   if (!comms->RecvProtoBuf(&setup)) {
@@ -128,87 +194,34 @@ bool RunLibUnwindAndSymbolizer(Comms* comms) {
 
   EnablePtraceEmulationWithUserRegs(setup.regs());
 
-  std::vector<uintptr_t> ips;
+  absl::StatusOr<std::vector<uintptr_t>> ips =
-  std::vector<std::string> stack_trace =
+      RunLibUnwind(setup.pid(), setup.default_max_frames());
-      RunLibUnwindAndSymbolizer(setup.pid(), &ips, setup.default_max_frames());
+  absl::StatusOr<std::vector<std::string>> stack_trace;
+  if (ips.ok()) {
+    stack_trace = SymbolizeStacktrace(setup.pid(), *ips);
+  } else {
+    stack_trace = ips.status();
+  }
+
+  if (!comms->SendStatus(stack_trace.status())) {
+    return false;
+  }
+
+  if (!stack_trace.ok()) {
+    return true;
+  }
 
   UnwindResult msg;
-  *msg.mutable_stacktrace() = {stack_trace.begin(), stack_trace.end()};
+  *msg.mutable_stacktrace() = {stack_trace->begin(), stack_trace->end()};
-  *msg.mutable_ip() = {ips.begin(), ips.end()};
+  *msg.mutable_ip() = {ips->begin(), ips->end()};
   return comms->SendProtoBuf(msg);
 }
 
-std::vector<std::string> RunLibUnwindAndSymbolizer(pid_t pid,
+absl::StatusOr<std::vector<std::string>> RunLibUnwindAndSymbolizer(
-                                                   std::vector<uintptr_t>* ips,
+    pid_t pid, int max_frames) {
-                                                   int max_frames) {
+  SAPI_ASSIGN_OR_RETURN(std::vector<uintptr_t> ips,
-  *ips = GetIPList(pid, max_frames);  // Uses libunwind
+                        RunLibUnwind(pid, max_frames));
-
+  return SymbolizeStacktrace(pid, ips);
-  const std::string maps_filename = absl::StrCat("/proc/", pid, "/maps");
-  std::string maps_content;
-  if (auto status = sapi::file::GetContents(maps_filename, &maps_content,
-                                            sapi::file::Defaults());
-      !status.ok()) {
-    SAPI_RAW_LOG(ERROR, "%s", status.ToString().c_str());
-    return {};
-  }
-
-  auto maps = ParseProcMaps(maps_content);
-  if (!maps.ok()) {
-    SAPI_RAW_LOG(ERROR, "Could not parse file: %s", maps_filename.c_str());
-    return {};
-  }
-
-  // Get symbols for each file entry in the maps entry.
-  // This is not a very efficient way, so we might want to optimize it.
-  std::map<uint64_t, std::string> addr_to_symbol;
-  for (const auto& entry : *maps) {
-    if (!entry.path.empty()) {
-      // Store details about start + end of this map.
-      // The maps entries are ordered and thus sorted with increasing adresses.
-      // This means if there is a symbol @ entry.end, it will be overwritten in
-      // the next iteration.
-      addr_to_symbol[entry.start] = absl::StrCat("map:", entry.path);
-      addr_to_symbol[entry.end] = "";
-    }
-
-    if (!entry.is_executable ||
-        entry.inode == 0 ||  // Only parse file-backed entries
-        entry.path.empty() ||
-        absl::EndsWith(entry.path, " (deleted)")  // Skip deleted files
-    ) {
-      continue;
-    }
-
-    auto elf = ElfFile::ParseFromFile(entry.path, ElfFile::kLoadSymbols);
-    if (!elf.ok()) {
-      SAPI_RAW_LOG(WARNING, "Could not load symbols for %s: %s",
-                   entry.path.c_str(),
-                   std::string(elf.status().message()).c_str());
-      continue;
-    }
-
-    for (const auto& symbol : elf->symbols()) {
-      if (elf->position_independent()) {
-        if (symbol.address < entry.end - entry.start) {
-          addr_to_symbol[symbol.address + entry.start] = symbol.name;
-        }
-      } else {
-        if (symbol.address >= entry.start && symbol.address < entry.end) {
-          addr_to_symbol[symbol.address] = symbol.name;
-        }
-      }
-    }
-  }
-
-  std::vector<std::string> stack_trace;
-  stack_trace.reserve(ips->size());
-  // Symbolize stacktrace
-  for (const auto& ip : *ips) {
-    const std::string symbol =
-        GetSymbolAt(addr_to_symbol, static_cast<uint64_t>(ip));
-    stack_trace.push_back(absl::StrCat(symbol, "(0x", absl::Hex(ip), ")"));
-  }
-  return stack_trace;
 }
 
 }  // namespace sandbox2

sandboxed_api/sandbox2/unwind/unwind.h

@@ -21,6 +21,7 @@
 #include <string>
 #include <vector>
 
+#include "absl/status/statusor.h"
 #include "sandboxed_api/sandbox2/comms.h"
 
 namespace sandbox2 {
@@ -28,9 +29,8 @@ namespace sandbox2 {
 // Runs libunwind and the symbolizer and sends the results via comms.
 bool RunLibUnwindAndSymbolizer(Comms* comms);
 
-std::vector<std::string> RunLibUnwindAndSymbolizer(pid_t pid,
+absl::StatusOr<std::vector<std::string>> RunLibUnwindAndSymbolizer(
-                                                   std::vector<uintptr_t>* ips,
+    pid_t pid, int max_frames);
-                                                   int max_frames);
 
 }  // namespace sandbox2