Improve SIGILL support.

Include the illegal instruction in the header if we get a
SIGILL. Otherwise (since these tend to be one-off bit flips), we don't
usually have any information to try to confirm our suspicion that any
given instance is actually a one-off bit flip.

Also add `SIGILL` as a crasher option to easily generate such crashes.

Before:
  signal 4 (SIGILL), code 1 (ILL_ILLOPC), fault addr 0xab1456da

After:
  signal 4 (SIGILL), code 1 (ILL_ILLOPC), fault addr 0xab1456da (*pc=0xe7f0def0)

Bug: http://b/77274448
Test: ran crasher
Change-Id: I5f8dedca5eea2b117b1b1e48430214b38e1366ed

2 files changed, 22 insertions, 4 deletions

diff --git a/debuggerd/crasher/crasher.cpp b/debuggerd/crasher/crasher.cpp
index 4b32b9d36..f31337d70 100644
--- a/debuggerd/crasher/crasher.cpp
+++ b/debuggerd/crasher/crasher.cpp
@@ -197,6 +197,7 @@ static int usage() {
     fprintf(stderr, "  LOG-FATAL             call libbase LOG(FATAL)\n");
     fprintf(stderr, "\n");
     fprintf(stderr, "  SIGFPE                cause a SIGFPE\n");
+    fprintf(stderr, "  SIGILL                cause a SIGILL\n");
     fprintf(stderr, "  SIGSEGV               cause a SIGSEGV at address 0x0 (synonym: crash)\n");
     fprintf(stderr, "  SIGSEGV-non-null      cause a SIGSEGV at a non-zero address\n");
     fprintf(stderr, "  SIGSEGV-unmapped      mmap/munmap a region of memory and then attempt to access it\n");
@@ -268,6 +269,16 @@ noinline int do_action(const char* arg) {
     } else if (!strcasecmp(arg, "SIGFPE")) {
         raise(SIGFPE);
         return EXIT_SUCCESS;
+    } else if (!strcasecmp(arg, "SIGILL")) {
+#if defined(__aarch64__)
+      __asm__ volatile(".word 0\n");
+#elif defined(__arm__)
+      __asm__ volatile(".word 0xe7f0def0\n");
+#elif defined(__i386__) || defined(__x86_64__)
+      __asm__ volatile("ud2\n");
+#else
+#error
+#endif
     } else if (!strcasecmp(arg, "SIGTRAP")) {
         raise(SIGTRAP);
         return EXIT_SUCCESS;
diff --git a/debuggerd/libdebuggerd/tombstone.cpp b/debuggerd/libdebuggerd/tombstone.cpp
index e11be1ea7..433bb4657 100644
--- a/debuggerd/libdebuggerd/tombstone.cpp
+++ b/debuggerd/libdebuggerd/tombstone.cpp
@@ -102,10 +102,17 @@ static void dump_probable_cause(log_t* log, const siginfo_t* si) {
   if (!cause.empty()) _LOG(log, logtype::HEADER, "Cause: %s\n", cause.c_str());
 }
 
-static void dump_signal_info(log_t* log, const ThreadInfo& thread_info) {
-  char addr_desc[32]; // ", fault addr 0x1234"
+static void dump_signal_info(log_t* log, const ThreadInfo& thread_info, Memory* process_memory) {
+  char addr_desc[64];  // ", fault addr 0x1234"
   if (signal_has_si_addr(thread_info.siginfo)) {
-    snprintf(addr_desc, sizeof(addr_desc), "%p", thread_info.siginfo->si_addr);
+    void* addr = thread_info.siginfo->si_addr;
+    if (thread_info.siginfo->si_signo == SIGILL) {
+      uint32_t instruction = {};
+      process_memory->Read(reinterpret_cast<uint64_t>(addr), &instruction, sizeof(instruction));
+      snprintf(addr_desc, sizeof(addr_desc), "%p (*pc=%#08x)", addr, instruction);
+    } else {
+      snprintf(addr_desc, sizeof(addr_desc), "%p", addr);
+    }
   } else {
     snprintf(addr_desc, sizeof(addr_desc), "--------");
   }
@@ -418,7 +425,7 @@ static bool dump_thread(log_t* log, BacktraceMap* map, Memory* process_memory,
   dump_thread_info(log, thread_info);
 
   if (thread_info.siginfo) {
-    dump_signal_info(log, thread_info);
+    dump_signal_info(log, thread_info, process_memory);
   }
 
   if (primary_thread) {