Merge "Show maps near native fault address"

4 files changed, 112 insertions, 7 deletions

diff --git a/debuggerd/arm/machine.c b/debuggerd/arm/machine.c
index 88bf054..58a7839 100644
--- a/debuggerd/arm/machine.c
+++ b/debuggerd/arm/machine.c
@@ -50,6 +50,74 @@ extern int unwind_backtrace_with_ptrace(int tfd, pid_t pid, mapinfo *map,
                                         int *frame0_pc_sane,
                                         bool at_fault);
 
+/*
+ * If this isn't clearly a null pointer dereference, dump the
+ * /proc/maps entries near the fault address.
+ */
+static void show_nearby_maps(int tfd, int pid, mapinfo *map)
+{
+    siginfo_t si;
+
+    memset(&si, 0, sizeof(si));
+    if (ptrace(PTRACE_GETSIGINFO, pid, 0, &si)) {
+        _LOG(tfd, false, "cannot get siginfo: %s\n", strerror(errno));
+        return;
+    }
+    if (!signal_has_address(si.si_signo))
+        return;
+
+    uintptr_t addr = (uintptr_t) si.si_addr;
+    addr &= ~0xfff;     /* round to 4K page boundary */
+    if (addr == 0)      /* null-pointer deref */
+        return;
+
+    _LOG(tfd, false, "\nmemory map around addr %08x:\n", si.si_addr);
+
+    /*
+     * Search for a match, or for a hole where the match would be.  The list
+     * is backward from the file content, so it starts at high addresses.
+     */
+    bool found = false;
+    mapinfo *next = NULL;
+    mapinfo *prev = NULL;
+    while (map != NULL) {
+        if (addr >= map->start && addr < map->end) {
+            found = true;
+            next = map->next;
+            break;
+        } else if (addr >= map->end) {
+            /* map would be between "prev" and this entry */
+            next = map;
+            map = NULL;
+            break;
+        }
+
+        prev = map;
+        map = map->next;
+    }
+
+    /*
+     * Show "next" then "match" then "prev" so that the addresses appear in
+     * ascending order (like /proc/pid/maps).
+     */
+    if (next != NULL) {
+        _LOG(tfd, false, "%08x-%08x %s\n", next->start, next->end, next->name);
+    } else {
+        _LOG(tfd, false, "(no map below)\n");
+    }
+    if (map != NULL) {
+        _LOG(tfd, false, "%08x-%08x %s\n", map->start, map->end, map->name);
+    } else {
+        _LOG(tfd, false, "(no map for address)\n");
+    }
+    if (prev != NULL) {
+        _LOG(tfd, false, "%08x-%08x %s\n", prev->start, prev->end, prev->name);
+    } else {
+        _LOG(tfd, false, "(no map above)\n");
+    }
+}
+
+
 void dump_stack_and_code(int tfd, int pid, mapinfo *map,
                          int unwind_depth, unsigned int sp_list[],
                          bool at_fault)
@@ -123,6 +191,8 @@ void dump_stack_and_code(int tfd, int pid, mapinfo *map,
         }
     }
 
+    show_nearby_maps(tfd, pid, map);
+
     p = sp - 64;
     if (p > sp)
         p = 0;
diff --git a/debuggerd/debuggerd.c b/debuggerd/debuggerd.c
index d03c214..97a6b9e 100644
--- a/debuggerd/debuggerd.c
+++ b/debuggerd/debuggerd.c
@@ -70,14 +70,17 @@ mapinfo *parse_maps_line(char *line)
     mapinfo *mi;
     int len = strlen(line);
 
-    if(len < 1) return 0;
+    if (len < 1) return 0;      /* not expected */
     line[--len] = 0;
 
-    if(len < 50) return 0;
-    if(line[20] != 'x') return 0;
+    if (len < 50) {
+        mi = malloc(sizeof(mapinfo) + 1);
+    } else {
+        mi = malloc(sizeof(mapinfo) + (len - 47));
+    }
+    if (mi == 0) return 0;
 
-    mi = malloc(sizeof(mapinfo) + (len - 47));
-    if(mi == 0) return 0;
+    mi->isExecutable = (line[20] == 'x');
 
     mi->start = strtoul(line, 0, 16);
     mi->end = strtoul(line + 9, 0, 16);
@@ -87,7 +90,11 @@ mapinfo *parse_maps_line(char *line)
     mi->exidx_start = mi->exidx_end = 0;
     mi->symbols = 0;
     mi->next = 0;
-    strcpy(mi->name, line + 49);
+    if (len < 50) {
+        mi->name[0] = '\0';
+    } else {
+        strcpy(mi->name, line + 49);
+    }
 
     return mi;
 }
@@ -165,11 +172,14 @@ void dump_fault_addr(int tfd, int pid, int sig)
     memset(&si, 0, sizeof(si));
     if(ptrace(PTRACE_GETSIGINFO, pid, 0, &si)){
         _LOG(tfd, false, "cannot get siginfo: %s\n", strerror(errno));
-    } else {
+    } else if (signal_has_address(sig)) {
         _LOG(tfd, false, "signal %d (%s), code %d (%s), fault addr %08x\n",
              sig, get_signame(sig),
              si.si_code, get_sigcode(sig, si.si_code),
              si.si_addr);
+    } else {
+        _LOG(tfd, false, "signal %d (%s), code %d (%s), fault addr --------\n",
+             sig, get_signame(sig), si.si_code, get_sigcode(sig, si.si_code));
     }
 }
 
@@ -199,6 +209,9 @@ static void parse_elf_info(mapinfo *milist, pid_t pid)
 {
     mapinfo *mi;
     for (mi = milist; mi != NULL; mi = mi->next) {
+        if (!mi->isExecutable)
+            continue;
+
         Elf32_Ehdr ehdr;
 
         memset(&ehdr, 0, sizeof(Elf32_Ehdr));
diff --git a/debuggerd/utility.c b/debuggerd/utility.c
index 2afdb46..409209c 100644
--- a/debuggerd/utility.c
+++ b/debuggerd/utility.c
@@ -17,6 +17,7 @@
 
 #include <sys/ptrace.h>
 #include <sys/exec_elf.h>
+#include <signal.h>
 #include <assert.h>
 #include <string.h>
 #include <errno.h>
@@ -82,3 +83,20 @@ const mapinfo *pc_to_mapinfo(mapinfo *mi, unsigned pc, unsigned *rel_pc)
     }
     return NULL;
 }
+
+/*
+ * Returns true if the specified signal has an associated address (i.e. it
+ * sets siginfo_t.si_addr).
+ */
+bool signal_has_address(int sig)
+{
+    switch (sig) {
+        case SIGILL:
+        case SIGFPE:
+        case SIGSEGV:
+        case SIGBUS:
+            return true;
+        default:
+            return false;
+    }
+}
diff --git a/debuggerd/utility.h b/debuggerd/utility.h
index 45e2067..4a935d2 100644
--- a/debuggerd/utility.h
+++ b/debuggerd/utility.h
@@ -36,6 +36,7 @@ typedef struct mapinfo {
     unsigned exidx_start;
     unsigned exidx_end;
     struct symbol_table *symbols;
+    bool isExecutable;
     char name[];
 } mapinfo;
 
@@ -56,6 +57,9 @@ const char *map_to_name(mapinfo *mi, unsigned pc, const char* def);
 /* Log information onto the tombstone */
 extern void _LOG(int tfd, bool in_tombstone_only, const char *fmt, ...);
 
+/* Determine whether si_addr is valid for this signal */
+bool signal_has_address(int sig);
+
 #define LOG(fmt...) _LOG(-1, 0, fmt)
 
 /* Set to 1 for normal debug traces */