Enhance native stack dumps.

Provides a new mechanism for dumpstate (while running as root)
to request that debuggerd dump the stacks of native processes that
we care about in bug reports.  In this mode, the backtrace
is formatted to look similar to a Dalvik backtrace.

Moved the tombstone generating code into a separate file to
make it easier to maintain.

Fixed a bug where sometimes the stack traces would be incomplete
because we were not waiting for each thread to stop after issuing
PTRACE_ATTACH, only the main thread.  So sometimes we were missing
traces for some threads.

Refactored the logging code to prevent accidentally writing data
to logcat when explicitly dumping a tombstone or backtrace from the
console.

Only root or system server can request to dump backtraces but
only root can dump tombstones.

Bug: 6615693
Change-Id: Ib3edcc16f9f3a687e414e3f2d250d9500566123b

1 files changed, 82 insertions, 38 deletions

diff --git a/debuggerd/arm/machine.c b/debuggerd/arm/machine.c
index ca45c9b..1c2e13f 100644
--- a/debuggerd/arm/machine.c
+++ b/debuggerd/arm/machine.c
@@ -15,23 +15,17 @@
 ** limitations under the License.
 */
 
+#include <stddef.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
 #include <stdio.h>
 #include <errno.h>
-#include <signal.h>
-#include <pthread.h>
-#include <fcntl.h>
 #include <sys/types.h>
-#include <dirent.h>
-
 #include <sys/ptrace.h>
-#include <sys/wait.h>
-#include <sys/exec_elf.h>
-#include <sys/stat.h>
 
-#include <cutils/sockets.h>
-#include <cutils/properties.h>
+#include <corkscrew/ptrace.h>
 
-#include <linux/input.h>
 #include <linux/user.h>
 
 #include "../utility.h"
@@ -48,11 +42,72 @@
 #endif
 #endif
 
+static void dump_memory(log_t* log, pid_t tid, uintptr_t addr, bool at_fault) {
+    char code_buffer[64];       /* actual 8+1+((8+1)*4) + 1 == 45 */
+    char ascii_buffer[32];      /* actual 16 + 1 == 17 */
+    uintptr_t p, end;
+
+    p = addr & ~3;
+    p -= 32;
+    if (p > addr) {
+        /* catch underflow */
+        p = 0;
+    }
+    end = p + 80;
+    /* catch overflow; 'end - p' has to be multiples of 16 */
+    while (end < p)
+        end -= 16;
+
+    /* Dump the code around PC as:
+     *  addr     contents                             ascii
+     *  00008d34 ef000000 e8bd0090 e1b00000 512fff1e  ............../Q
+     *  00008d44 ea00b1f9 e92d0090 e3a070fc ef000000  ......-..p......
+     */
+    while (p < end) {
+        char* asc_out = ascii_buffer;
+
+        sprintf(code_buffer, "%08x ", p);
+
+        int i;
+        for (i = 0; i < 4; i++) {
+            /*
+             * If we see (data == -1 && errno != 0), we know that the ptrace
+             * call failed, probably because we're dumping memory in an
+             * unmapped or inaccessible page.  I don't know if there's
+             * value in making that explicit in the output -- it likely
+             * just complicates parsing and clarifies nothing for the
+             * enlightened reader.
+             */
+            long data = ptrace(PTRACE_PEEKTEXT, tid, (void*)p, NULL);
+            sprintf(code_buffer + strlen(code_buffer), "%08lx ", data);
+
+            int j;
+            for (j = 0; j < 4; j++) {
+                /*
+                 * Our isprint() allows high-ASCII characters that display
+                 * differently (often badly) in different viewers, so we
+                 * just use a simpler test.
+                 */
+                char val = (data >> (j*8)) & 0xff;
+                if (val >= 0x20 && val < 0x7f) {
+                    *asc_out++ = val;
+                } else {
+                    *asc_out++ = '.';
+                }
+            }
+            p += 4;
+        }
+        *asc_out = '\0';
+        _LOG(log, !at_fault, "    %s %s\n", code_buffer, ascii_buffer);
+    }
+}
+
 /*
  * If configured to do so, dump memory around *all* registers
  * for the crashing thread.
  */
-static void dump_memory_and_code(int tfd, pid_t tid, bool at_fault) {
+void dump_memory_and_code(const ptrace_context_t* context __attribute((unused)),
+        log_t* log, pid_t tid, bool at_fault) {
     struct pt_regs regs;
     if(ptrace(PTRACE_GETREGS, tid, 0, &regs)) {
         return;
@@ -73,38 +128,38 @@ static void dump_memory_and_code(int tfd, pid_t tid, bool at_fault) {
                 continue;
             }
 
-            _LOG(tfd, false, "\nmemory near %.2s:\n", &REG_NAMES[reg * 2]);
-            dump_memory(tfd, tid, addr, at_fault);
+            _LOG(log, false, "\nmemory near %.2s:\n", &REG_NAMES[reg * 2]);
+            dump_memory(log, tid, addr, at_fault);
         }
     }
 
-    _LOG(tfd, !at_fault, "\ncode around pc:\n");
-    dump_memory(tfd, tid, (uintptr_t)regs.ARM_pc, at_fault);
+    _LOG(log, !at_fault, "\ncode around pc:\n");
+    dump_memory(log, tid, (uintptr_t)regs.ARM_pc, at_fault);
 
     if (regs.ARM_pc != regs.ARM_lr) {
-        _LOG(tfd, !at_fault, "\ncode around lr:\n");
-        dump_memory(tfd, tid, (uintptr_t)regs.ARM_lr, at_fault);
+        _LOG(log, !at_fault, "\ncode around lr:\n");
+        dump_memory(log, tid, (uintptr_t)regs.ARM_lr, at_fault);
     }
 }
 
 void dump_registers(const ptrace_context_t* context __attribute((unused)),
-        int tfd, pid_t tid, bool at_fault)
+        log_t* log, pid_t tid, bool at_fault)
 {
     struct pt_regs r;
     bool only_in_tombstone = !at_fault;
 
     if(ptrace(PTRACE_GETREGS, tid, 0, &r)) {
-        _LOG(tfd, only_in_tombstone, "cannot get registers: %s\n", strerror(errno));
+        _LOG(log, only_in_tombstone, "cannot get registers: %s\n", strerror(errno));
         return;
     }
 
-    _LOG(tfd, only_in_tombstone, "    r0 %08x  r1 %08x  r2 %08x  r3 %08x\n",
+    _LOG(log, only_in_tombstone, "    r0 %08x  r1 %08x  r2 %08x  r3 %08x\n",
             (uint32_t)r.ARM_r0, (uint32_t)r.ARM_r1, (uint32_t)r.ARM_r2, (uint32_t)r.ARM_r3);
-    _LOG(tfd, only_in_tombstone, "    r4 %08x  r5 %08x  r6 %08x  r7 %08x\n",
+    _LOG(log, only_in_tombstone, "    r4 %08x  r5 %08x  r6 %08x  r7 %08x\n",
             (uint32_t)r.ARM_r4, (uint32_t)r.ARM_r5, (uint32_t)r.ARM_r6, (uint32_t)r.ARM_r7);
-    _LOG(tfd, only_in_tombstone, "    r8 %08x  r9 %08x  sl %08x  fp %08x\n",
+    _LOG(log, only_in_tombstone, "    r8 %08x  r9 %08x  sl %08x  fp %08x\n",
             (uint32_t)r.ARM_r8, (uint32_t)r.ARM_r9, (uint32_t)r.ARM_r10, (uint32_t)r.ARM_fp);
-    _LOG(tfd, only_in_tombstone, "    ip %08x  sp %08x  lr %08x  pc %08x  cpsr %08x\n",
+    _LOG(log, only_in_tombstone, "    ip %08x  sp %08x  lr %08x  pc %08x  cpsr %08x\n",
             (uint32_t)r.ARM_ip, (uint32_t)r.ARM_sp, (uint32_t)r.ARM_lr,
             (uint32_t)r.ARM_pc, (uint32_t)r.ARM_cpsr);
 
@@ -113,25 +168,14 @@ void dump_registers(const ptrace_context_t* context __attribute((unused)),
     int i;
 
     if(ptrace(PTRACE_GETVFPREGS, tid, 0, &vfp_regs)) {
-        _LOG(tfd, only_in_tombstone, "cannot get registers: %s\n", strerror(errno));
+        _LOG(log, only_in_tombstone, "cannot get registers: %s\n", strerror(errno));
         return;
     }
 
     for (i = 0; i < NUM_VFP_REGS; i += 2) {
-        _LOG(tfd, only_in_tombstone, "    d%-2d %016llx  d%-2d %016llx\n",
+        _LOG(log, only_in_tombstone, "    d%-2d %016llx  d%-2d %016llx\n",
                 i, vfp_regs.fpregs[i], i+1, vfp_regs.fpregs[i+1]);
     }
-    _LOG(tfd, only_in_tombstone, "    scr %08lx\n", vfp_regs.fpscr);
+    _LOG(log, only_in_tombstone, "    scr %08lx\n", vfp_regs.fpscr);
 #endif
 }
-
-void dump_thread(const ptrace_context_t* context, int tfd, pid_t tid, bool at_fault) {
-    dump_registers(context, tfd, tid, at_fault);
-
-    dump_backtrace_and_stack(context, tfd, tid, at_fault);
-
-    if (at_fault) {
-        dump_memory_and_code(tfd, tid, at_fault);
-        dump_nearby_maps(context, tfd, tid);
-    }
-}