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Add frame pointer unwinding fallback

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PiperOrigin-RevId: 513193320
Change-Id: I0ade55e0d1fae6d33794ccd064766a18f0c86cd6
This commit is contained in:
Wiktor Garbacz 2023-03-01 03:54:29 -08:00 committed by Copybara-Service
parent e11109c9ee
commit fbfbd13adf
3 changed files with 63 additions and 2 deletions
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1
sandboxed_api/sandbox2/unwind/BUILD.bazel
View File

@ -54,6 +54,7 @@ cc_library(
"//sandboxed_api/util:raw_logging",
"//sandboxed_api/util:status",
"@com_google_absl//absl/cleanup",
"@com_google_absl//absl/status",
"@com_google_absl//absl/status:statusor",
"@com_google_absl//absl/strings",
"@org_gnu_libunwind//:unwind-ptrace",

1
sandboxed_api/sandbox2/unwind/CMakeLists.txt
View File

@ -32,6 +32,7 @@ add_library(sandbox2_unwind STATIC
add_library(sandbox2::unwind ALIAS sandbox2_unwind)
target_link_libraries(sandbox2_unwind PRIVATE
absl::cleanup
absl::status
absl::statusor
absl::strings
sandbox2::comms

63
sandboxed_api/sandbox2/unwind/unwind.cc
View File

@ -15,7 +15,9 @@
#include "sandboxed_api/sandbox2/unwind/unwind.h"
#include <cxxabi.h>
#include <sys/ptrace.h>
#include <cerrno>
#include <cstddef>
#include <cstdint>
#include <cstdio>
@ -26,6 +28,7 @@
#include <vector>
#include "absl/cleanup/cleanup.h"
#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/match.h"
#include "absl/strings/str_cat.h"
@ -56,6 +59,33 @@ std::string DemangleSymbol(const std::string& maybe_mangled) {
return maybe_mangled;
}
absl::StatusOr<uintptr_t> ReadMemory(pid_t pid, uintptr_t addr) {
errno = 0;
uintptr_t val = ptrace(PTRACE_PEEKDATA, pid, addr, 0);
if (errno != 0) {
return absl::ErrnoToStatus(errno, "ptrace() failed");
}
return val;
}
absl::StatusOr<std::vector<uintptr_t>> UnwindUsingFramePointer(pid_t pid,
int max_frames,
uintptr_t fp) {
#if defined(SAPI_PPC64_LE)
constexpr int kIPOffset = 2;
#else
constexpr int kIPOffset = 1;
#endif
std::vector<uintptr_t> ips;
for (int i = 0; fp != 0 && i < max_frames; ++i) {
SAPI_ASSIGN_OR_RETURN(uintptr_t ip,
ReadMemory(pid, fp + kIPOffset * sizeof(void*)));
ips.push_back(ip);
SAPI_ASSIGN_OR_RETURN(fp, ReadMemory(pid, fp));
}
return ips;
}
absl::StatusOr<std::vector<uintptr_t>> RunLibUnwind(pid_t pid, int max_frames) {
static unw_addr_space_t as =
unw_create_addr_space(&_UPT_accessors, 0 /* byte order */);
@ -75,18 +105,47 @@ absl::StatusOr<std::vector<uintptr_t>> RunLibUnwind(pid_t pid, int max_frames) {
return absl::InternalError(
absl::StrCat("unw_init_remote() failed with error ", rc));
}
std::vector<uintptr_t> ips;
for (int i = 0; i < max_frames; ++i) {
unw_word_t ip;
unw_word_t fp = 0;
int rc = unw_get_reg(&cursor, UNW_REG_IP, &ip);
if (rc < 0) {
// Could be UNW_EUNSPEC or UNW_EBADREG.
SAPI_RAW_LOG(WARNING, "unw_get_reg() failed with error %d", rc);
break;
}
#if defined(SAPI_ARM64)
constexpr int kFpReg = UNW_AARCH64_X29;
#elif defined(SAPI_ARM)
constexpr int kFpReg = UNW_ARM_R11;
#elif defined(SAPI_X86_64)
constexpr int kFpReg = UNW_X86_64_RBP;
#elif defined(SAPI_PPC64_LE)
constexpr int kFpReg = UNW_PPC64_R1;
#endif
rc = unw_get_reg(&cursor, kFpReg, &fp);
if (rc < 0) {
SAPI_RAW_LOG(WARNING, "unw_get_reg() failed with error %d", rc);
}
ips.push_back(ip);
if (unw_step(&cursor) <= 0) {
rc = unw_step(&cursor);
if (rc <= 0) {
if (rc < 0) {
SAPI_RAW_LOG(WARNING, "unw_step() failed with error %d", rc);
}
if (fp != 0) {
SAPI_RAW_LOG(INFO, "Falling back to frame based unwinding at FP: %lx",
fp);
absl::StatusOr<std::vector<uintptr_t>> fp_ips =
UnwindUsingFramePointer(pid, max_frames - ips.size(), fp);
if (!fp_ips.ok()) {
SAPI_RAW_LOG(WARNING, "FP based unwinding failed: %s",
std::string(fp_ips.status().message()).c_str());
break;
}
ips.insert(ips.end(), fp_ips->begin(), fp_ips->end());
}
break;
}
}