FatalSignalHandler: print some more information from siginfo_t

The siginfo_t parameter allows us to show what process sent a signal or
the crashing address. Additionally, it allows us to determine if the
crashing signal was indeed sent due to a crash.

The selftest tst_crashes produces now:

$ QTEST_DISABLE_STACK_DUMP=1 ./crashes
********* Start testing of tst_Crashes *********
Config: Using QtTest library 6.4.0, Qt 6.4.0 (x86_64-little_endian-lp64 shared (dynamic) debug build; by GCC 11.2.1 20220420 [revision 691af15031e00227ba6d5935c1d737026cda4129]), opensuse-tumbleweed 20220428
PASS   : tst_Crashes::initTestCase()
Received signal 11 (SIGSEGV), code 1, for address 0x0000000000000004
         Function time: 0ms, total time: 0ms
[1]    201995 segmentation fault (core dumped)  QTEST_DISABLE_STACK_DUMP=1 ./crashes

The last line comes from the shell. The code isn't decoded, but on Linux
it's a SEGV_MAPERR. macOS prints exactly the same thing.

I've updated one of the expected_crashes_*.txt output that doesn't seem
possible (the "Received a fatal error" message does not appear in Qt
anywhere).

Change-Id: I5ff8e16fcdcb4ffd9ab6fffd16ebc8391234f0e2
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 5e67e7efaa2669252fd8c55392b7bc35b72c6079)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 41 insertions, 11 deletions

diff --git a/src/testlib/qtestcase.cpp b/src/testlib/qtestcase.cpp
index 6b5584366d..f55d4ba38f 100644
--- a/src/testlib/qtestcase.cpp
+++ b/src/testlib/qtestcase.cpp
@@ -2074,12 +2074,48 @@ private:
 #  endif
     }
 
-    static void actionHandler(int signum, siginfo_t * /* info */, void * /* ucontext */)
+    template <typename T> static
+    std::enable_if_t<sizeof(std::declval<T>().si_pid) + sizeof(std::declval<T>().si_uid) >= 1>
+    printSentSignalInfo(T *info)
+    {
+        writeToStderr(" sent by PID ", asyncSafeToString(info->si_pid),
+                      " UID ", asyncSafeToString(info->si_uid));
+    }
+    static void printSentSignalInfo(...) {}
+
+    template <typename T> static
+    std::enable_if_t<sizeof(std::declval<T>().si_addr) >= 1> printCrashingSignalInfo(T *info)
+    {
+        using HexString = std::array<char, sizeof(quintptr) * 2>;
+        auto toHexString = [](quintptr u, HexString &&r = {}) {
+            int shift = sizeof(quintptr) * 8 - 4;
+            for (size_t i = 0; i < sizeof(quintptr) * 2; ++i, shift -= 4)
+                r[i] = QtMiscUtils::toHexLower(u >> shift);
+            struct iovec vec;
+            vec.iov_base = r.data();
+            vec.iov_len = r.size();
+            return vec;
+        };
+        writeToStderr(", code ", asyncSafeToString(info->si_code),
+                      ", for address 0x", toHexString(quintptr(info->si_addr)));
+    }
+    static void printCrashingSignalInfo(...) {}
+
+    static void actionHandler(int signum, siginfo_t *info, void * /* ucontext */)
     {
         writeToStderr("Received signal ", asyncSafeToString(signum),
-                      " (SIG", signalName(signum), ")\n");
-        printTestRunTime();
+                      " (SIG", signalName(signum), ")");
 
+        bool isCrashingSignal =
+                std::find(crashingSignals.begin(), crashingSignals.end(), signum) != crashingSignals.end();
+        if (isCrashingSignal && (!info || info->si_code <= 0))
+            isCrashingSignal = false;       // wasn't sent by the kernel, so it's not really a crash
+        if (isCrashingSignal)
+            printCrashingSignalInfo(info);
+        else if (info && (info->si_code == SI_USER || info->si_code == SI_QUEUE))
+            printSentSignalInfo(info);
+
+        printTestRunTime();
         if (signum != SIGINT) {
             generateStackTrace();
             if (pauseOnCrash) {
@@ -2089,9 +2125,6 @@ private:
             }
         }
 
-        bool isCrashingSignal =
-                std::find(crashingSignals.begin(), crashingSignals.end(), signum) != crashingSignals.end();
-
         // chain back to the previous handler, if any
         for (size_t i = 0; i < fatalSignals.size(); ++i) {
             struct sigaction &act = oldActions()[i];
diff --git a/tests/auto/testlib/selftests/expected_crashes_3.txt b/tests/auto/testlib/selftests/expected_crashes_3.txt
index c32ea53675..b0d69009d1 100644
--- a/tests/auto/testlib/selftests/expected_crashes_3.txt
+++ b/tests/auto/testlib/selftests/expected_crashes_3.txt
@@ -1,8 +1,5 @@
 ********* Start testing of tst_Crashes *********
 Config: Using QtTest library @INSERT_QT_VERSION_HERE@, Qt @INSERT_QT_VERSION_HERE@
 PASS   : tst_Crashes::initTestCase()
-QFATAL : tst_Crashes::crash() Received signal 11
-         Function time: ms Total time: ms
-FAIL!  : tst_Crashes::crash() Received a fatal error.
-Totals: 1 passed, 1 failed, 0 skipped, 0 blacklisted
-********* Finished testing of tst_Crashes *********
+Received signal 11 (SIGSEGV), code 1, for address 0x0000000000000004
+         Function time: ms, total time: ms