crash handler snapshot, unverified

ndk/jni/crash_hook.c

@@ -0,0 +1,122 @@
+#include <jni.h>
+#include <android/log.h>
+#include <dlfcn.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+#include <unwind.h>
+
+#define LOG_TAG "androidcast_crash"
+#define REPORT_DIR_MAX 512
+#define MAX_FRAMES 64
+
+static char g_report_dir[REPORT_DIR_MAX];
+static volatile sig_atomic_t g_handling;
+
+typedef struct {
+    void **frames;
+    int max;
+    int count;
+} backtrace_state_t;
+
+static _Unwind_Reason_Code unwind_callback(struct _Unwind_Context *context, void *arg) {
+    backtrace_state_t *state = (backtrace_state_t *) arg;
+    uintptr_t pc = _Unwind_GetIP(context);
+    if (pc == 0) {
+        return _URC_NO_REASON;
+    }
+    if (state->count < state->max) {
+        state->frames[state->count++] = (void *) pc;
+    }
+    return _URC_NO_REASON;
+}
+
+static int capture_backtrace(void **frames, int max) {
+    backtrace_state_t state = {frames, max, 0};
+    _Unwind_Backtrace(unwind_callback, &state);
+    return state.count;
+}
+
+static void write_native_report(const char *signal_name) {
+    if (g_report_dir[0] == '\0') {
+        return;
+    }
+    char path[REPORT_DIR_MAX + 64];
+    snprintf(path, sizeof(path), "%s/native_%d_%ld.txt",
+            g_report_dir, (int) getpid(), (long) time(NULL));
+    FILE *f = fopen(path, "w");
+    if (!f) {
+        return;
+    }
+    fprintf(f, "signal=%s\n", signal_name);
+    fprintf(f, "pid=%d\n", (int) getpid());
+    void *frames[MAX_FRAMES];
+    int n = capture_backtrace(frames, MAX_FRAMES);
+    for (int i = 0; i < n; i++) {
+        Dl_info info;
+        memset(&info, 0, sizeof(info));
+        if (dladdr(frames[i], &info) && info.dli_fname) {
+            uintptr_t offset = (uintptr_t) frames[i] - (uintptr_t) info.dli_fbase;
+            fprintf(f, "#%02d %p %s", i, frames[i], info.dli_fname);
+            if (info.dli_sname) {
+                fprintf(f, " %s+0x%lx", info.dli_sname,
+                        (unsigned long) ((uintptr_t) frames[i] - (uintptr_t) info.dli_saddr));
+            } else {
+                fprintf(f, "+0x%lx", (unsigned long) offset);
+            }
+            fprintf(f, "\n");
+        } else {
+            fprintf(f, "#%02d %p\n", i, frames[i]);
+        }
+    }
+    fclose(f);
+}
+
+static void crash_signal_handler(int sig) {
+    if (g_handling) {
+        _exit(128 + sig);
+    }
+    g_handling = 1;
+    const char *name = "UNKNOWN";
+    switch (sig) {
+        case SIGSEGV: name = "SIGSEGV"; break;
+        case SIGABRT: name = "SIGABRT"; break;
+        case SIGBUS:  name = "SIGBUS";  break;
+        case SIGFPE:  name = "SIGFPE";  break;
+        case SIGILL:  name = "SIGILL";  break;
+    }
+    write_native_report(name);
+    signal(sig, SIG_DFL);
+    raise(sig);
+}
+
+static void install_handlers(void) {
+    struct sigaction sa;
+    memset(&sa, 0, sizeof(sa));
+    sa.sa_handler = crash_signal_handler;
+    sigemptyset(&sa.sa_mask);
+    sa.sa_flags = SA_RESETHAND;
+    sigaction(SIGSEGV, &sa, NULL);
+    sigaction(SIGABRT, &sa, NULL);
+    sigaction(SIGBUS, &sa, NULL);
+    sigaction(SIGFPE, &sa, NULL);
+    sigaction(SIGILL, &sa, NULL);
+}
+
+JNIEXPORT void JNICALL
+Java_com_foxx_androidcast_crash_CrashNativeBridge_nativeInstallCrashHook(
+        JNIEnv *env, jclass clazz, jstring reportDir) {
+    (void) clazz;
+    const char *dir = (*env)->GetStringUTFChars(env, reportDir, NULL);
+    if (!dir) {
+        return;
+    }
+    strncpy(g_report_dir, dir, REPORT_DIR_MAX - 1);
+    g_report_dir[REPORT_DIR_MAX - 1] = '\0';
+    (*env)->ReleaseStringUTFChars(env, reportDir, dir);
+    install_handlers();
+    __android_log_print(ANDROID_LOG_INFO, LOG_TAG, "native crash hook installed: %s", g_report_dir);
+}