Improving maps output.

Maps output now displays fault address location more intelligently.  If
the fault is not in a mapped region, it now shows where that address is
with respect to the other maps.

In addition, the size of the map is now printed as part of the output.

Also, crasher now supports an "mmap" option which mmaps/munmaps a region
of memory and then attempts to access it, causing a fault address in
between mapped regions that can be used to test that new part of the
maps output.

Change-Id: Ia5e1926802bdfcbbdb7857e3631ddf395ae0c5b8

2 files changed, 25 insertions, 15 deletions

diff --git a/debuggerd/crasher.c b/debuggerd/crasher.c
index e11d9af..9df3c64 100644
--- a/debuggerd/crasher.c
+++ b/debuggerd/crasher.c
@@ -7,6 +7,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/cdefs.h>
+#include <sys/mman.h>
 #include <sys/ptrace.h>
 #include <sys/socket.h>
 #include <sys/wait.h>
@@ -156,6 +157,10 @@ static int do_action(const char* arg)
         return EXIT_SUCCESS;
     } else if (!strcmp(arg, "heap-usage")) {
         abuse_heap();
+    } else if (!strcmp(arg, "SIGSEGV-unmapped")) {
+        char* map = mmap(NULL, sizeof(int), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+        munmap(map, sizeof(int));
+        map[0] = '8';
     }
 
     fprintf(stderr, "%s OP\n", __progname);
@@ -175,6 +180,7 @@ static int do_action(const char* arg)
     fprintf(stderr, "  SIGPIPE               cause a SIGPIPE\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");
     fprintf(stderr, "  SIGTRAP               cause a SIGTRAP\n");
     fprintf(stderr, "prefix any of the above with 'thread-' to not run\n");
     fprintf(stderr, "on the process' main thread.\n");
diff --git a/debuggerd/tombstone.cpp b/debuggerd/tombstone.cpp
index dea016d..2bb9efd 100755
--- a/debuggerd/tombstone.cpp
+++ b/debuggerd/tombstone.cpp
@@ -329,10 +329,11 @@ static void dump_backtrace_and_stack(Backtrace* backtrace, log_t* log) {
 }
 
 static void dump_map(log_t* log, const backtrace_map_t* map, bool fault_addr) {
-  _LOG(log, logtype::MAPS, "%s%" PRIPTR "-%" PRIPTR " %c%c%c %s\n",
-         (fault_addr? "--->" : "    "), map->start, map->end,
+  _LOG(log, logtype::MAPS, "%s%" PRIPTR "-%" PRIPTR " %c%c%c  %7d  %s\n",
+         (fault_addr? "--->" : "    "), map->start, map->end - 1,
          (map->flags & PROT_READ) ? 'r' : '-', (map->flags & PROT_WRITE) ? 'w' : '-',
-         (map->flags & PROT_EXEC) ? 'x' : '-', map->name.c_str());
+         (map->flags & PROT_EXEC) ? 'x' : '-',
+         (map->end - map->start), map->name.c_str());
 }
 
 static void dump_nearby_maps(BacktraceMap* map, log_t* log, pid_t tid) {
@@ -342,28 +343,31 @@ static void dump_nearby_maps(BacktraceMap* map, log_t* log, pid_t tid) {
     _LOG(log, logtype::MAPS, "cannot get siginfo for %d: %s\n", tid, strerror(errno));
     return;
   }
-  if (!signal_has_si_addr(si.si_signo)) {
-    return;
-  }
 
+  bool is_running = (si.si_code == SI_USER);
   uintptr_t addr = reinterpret_cast<uintptr_t>(si.si_addr);
   addr &= ~0xfff;     // round to 4K page boundary
-  if (addr == 0) {    // null-pointer deref
+  if (!is_running && addr == 0) {    // null-pointer deref
     return;
   }
 
-  _LOG(log, logtype::MAPS, "\nmemory map: (fault address prefixed with --->)\n");
+  _LOG(log, logtype::MAPS, "\nmemory map: %s\n", is_running? "" : "(fault address prefixed with --->)");
+
+  if(!is_running && (addr < map->begin()->start)) {
+    _LOG(log, logtype::MAPS, "--->Fault address falls at %" PRIPTR " before any mapped regions\n", addr);
+  }
 
-  bool found_map = false;
+  BacktraceMap::const_iterator prev = map->begin();
   for (BacktraceMap::const_iterator it = map->begin(); it != map->end(); ++it) {
-    bool in_map = addr >= (*it).start && addr < (*it).end;
-    dump_map(log, &*it, in_map);
-    if(in_map) {
-      found_map = true;
+    if (addr >= (*prev).end && addr < (*it).start) {
+      _LOG(log, logtype::MAPS, "--->Fault address falls at %" PRIPTR " between mapped regions\n", addr);
     }
+    prev = it;
+    bool in_map = !is_running && (addr >= (*it).start) && (addr < (*it).end);
+    dump_map(log, &*it, in_map);
   }
-  if(!found_map) {
-    _LOG(log, logtype::ERROR, "\nFault address was not in any map!");
+  if (!is_running && (addr >= (*prev).end)) {
+    _LOG(log, logtype::MAPS, "--->Fault address falls at %" PRIPTR " after any mapped regions\n", addr);
   }
 }