[libunwind] Support for leaf function unwinding.
Unwinding leaf function is useful in cases when the backtrace finds a
leaf function for example when it caused a signal.
This patch also add the support for the DW_CFA_undefined because it marks
the end of the frames.
Ryan Prichard provided code for the tests.
Reviewed By: #libunwind, mstorsjo
Differential Revision: https://reviews.llvm.org/D83573
Reland with limit the test to the x86_64-linux target.
GitOrigin-RevId: 22b615a96593f13109a27cabfd1764ec4f558c7a
diff --git a/src/DwarfInstructions.hpp b/src/DwarfInstructions.hpp
index ee98f53..c39cabe 100644
--- a/src/DwarfInstructions.hpp
+++ b/src/DwarfInstructions.hpp
@@ -93,7 +93,8 @@
case CFI_Parser<A>::kRegisterInRegister:
return registers.getRegister((int)savedReg.value);
-
+ case CFI_Parser<A>::kRegisterUndefined:
+ return 0;
case CFI_Parser<A>::kRegisterUnused:
case CFI_Parser<A>::kRegisterOffsetFromCFA:
// FIX ME
@@ -117,6 +118,7 @@
case CFI_Parser<A>::kRegisterIsExpression:
case CFI_Parser<A>::kRegisterUnused:
+ case CFI_Parser<A>::kRegisterUndefined:
case CFI_Parser<A>::kRegisterOffsetFromCFA:
case CFI_Parser<A>::kRegisterInRegister:
// FIX ME
@@ -140,6 +142,7 @@
case CFI_Parser<A>::kRegisterIsExpression:
case CFI_Parser<A>::kRegisterUnused:
+ case CFI_Parser<A>::kRegisterUndefined:
case CFI_Parser<A>::kRegisterOffsetFromCFA:
case CFI_Parser<A>::kRegisterInRegister:
// FIX ME
@@ -190,6 +193,10 @@
prolog.savedRegisters[i]));
else
return UNW_EBADREG;
+ } else if (i == (int)cieInfo.returnAddressRegister) {
+ // Leaf function keeps the return address in register and there is no
+ // explicit intructions how to restore it.
+ returnAddress = registers.getRegister(cieInfo.returnAddressRegister);
}
}
diff --git a/src/DwarfParser.hpp b/src/DwarfParser.hpp
index fb943ed..86c0522 100644
--- a/src/DwarfParser.hpp
+++ b/src/DwarfParser.hpp
@@ -69,6 +69,7 @@
};
enum RegisterSavedWhere {
kRegisterUnused,
+ kRegisterUndefined,
kRegisterInCFA,
kRegisterOffsetFromCFA,
kRegisterInRegister,
@@ -505,7 +506,7 @@
"malformed DW_CFA_undefined DWARF unwind, reg too big");
return false;
}
- results->setRegisterLocation(reg, kRegisterUnused, initialState);
+ results->setRegisterLocation(reg, kRegisterUndefined, initialState);
_LIBUNWIND_TRACE_DWARF("DW_CFA_undefined(reg=%" PRIu64 ")\n", reg);
break;
case DW_CFA_same_value:
diff --git a/test/lit.site.cfg.in b/test/lit.site.cfg.in
index 8ff770f..84dae3c 100644
--- a/test/lit.site.cfg.in
+++ b/test/lit.site.cfg.in
@@ -44,6 +44,10 @@
# Allow expanding substitutions that are based on other substitutions
config.recursiveExpansionLimit = 10
+# Make symbols available in the tests.
+config.test_compiler_flags += " -funwind-tables "
+config.test_linker_flags += " -Wl,--export-dynamic "
+
# Infer the test_exec_root from the build directory.
config.test_exec_root = os.path.join(config.libunwind_obj_root, 'test')
diff --git a/test/signal_unwind.pass.cpp b/test/signal_unwind.pass.cpp
new file mode 100644
index 0000000..5955c1b
--- /dev/null
+++ b/test/signal_unwind.pass.cpp
@@ -0,0 +1,45 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Ensure that the unwinder can cope with the signal handler.
+// REQUIRES: x86_64-linux
+
+#include <assert.h>
+#include <dlfcn.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <unwind.h>
+
+_Unwind_Reason_Code frame_handler(struct _Unwind_Context* ctx, void* arg) {
+ (void)arg;
+ Dl_info info = { 0, 0, 0, 0 };
+ assert(dladdr((void*)_Unwind_GetIP(ctx), &info));
+
+ // Unwind util the main is reached, above frames deeped on the platfrom and architecture.
+ if(info.dli_sname && !strcmp("main", info.dli_sname)) {
+ _Exit(0);
+ }
+ return _URC_NO_REASON;
+}
+
+void signal_handler(int signum) {
+ (void)signum;
+ _Unwind_Backtrace(frame_handler, NULL);
+ _Exit(-1);
+}
+
+int main() {
+ signal(SIGUSR1, signal_handler);
+ kill(getpid(), SIGUSR1);
+ return -2;
+}
diff --git a/test/unwind_leaffunction.pass.cpp b/test/unwind_leaffunction.pass.cpp
new file mode 100644
index 0000000..8e4fcbe
--- /dev/null
+++ b/test/unwind_leaffunction.pass.cpp
@@ -0,0 +1,51 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Ensure that leaf function can be unwund.
+// REQUIRES: x86_64-linux
+
+#include <assert.h>
+#include <dlfcn.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <unwind.h>
+
+_Unwind_Reason_Code frame_handler(struct _Unwind_Context* ctx, void* arg) {
+ (void)arg;
+ Dl_info info = { 0, 0, 0, 0 };
+ assert(dladdr((void*)_Unwind_GetIP(ctx), &info));
+
+ // Unwind util the main is reached, above frames deeped on the platfrom and architecture.
+ if(info.dli_sname && !strcmp("main", info.dli_sname)) {
+ _Exit(0);
+ }
+ return _URC_NO_REASON;
+}
+
+void signal_handler(int signum) {
+ (void)signum;
+ _Unwind_Backtrace(frame_handler, NULL);
+ _Exit(-1);
+}
+
+int* faultyPointer = NULL;
+
+__attribute__((noinline)) void crashing_leaf_func(void) {
+ *faultyPointer = 0;
+}
+
+int main() {
+ signal(SIGSEGV, signal_handler);
+ crashing_leaf_func();
+ return -2;
+}
\ No newline at end of file
