1 // Copyright 2014 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4
5 #include <stdarg.h>
6 #include <android/log.h>
7 #include <pthread.h>
8 #include <dlfcn.h>
9 #include "libcgo.h"
10
11 void
fatalf(const char * format,...)12 fatalf(const char* format, ...)
13 {
14 va_list ap;
15
16 // Write to both stderr and logcat.
17 //
18 // When running from an .apk, /dev/stderr and /dev/stdout
19 // redirect to /dev/null. And when running a test binary
20 // via adb shell, it's easy to miss logcat.
21
22 fprintf(stderr, "runtime/cgo: ");
23 va_start(ap, format);
24 vfprintf(stderr, format, ap);
25 va_end(ap);
26 fprintf(stderr, "\n");
27
28 va_start(ap, format);
29 __android_log_vprint(ANDROID_LOG_FATAL, "runtime/cgo", format, ap);
30 va_end(ap);
31
32 abort();
33 }
34
35 // Truncated to a different magic value on 32-bit; that's ok.
36 #define magic1 (0x23581321345589ULL)
37
38 // From https://android.googlesource.com/platform/bionic/+/refs/heads/android10-tests-release/libc/private/bionic_asm_tls.h#69.
39 #define TLS_SLOT_APP 2
40
41 // inittls allocates a thread-local storage slot for g.
42 //
43 // It finds the first available slot using pthread_key_create and uses
44 // it as the offset value for runtime.tls_g.
45 static void
inittls(void ** tlsg,void ** tlsbase)46 inittls(void **tlsg, void **tlsbase)
47 {
48 pthread_key_t k;
49 int i, err;
50 void *handle, *get_ver, *off;
51
52 // Check for Android Q where we can use the free TLS_SLOT_APP slot.
53 handle = dlopen("libc.so", RTLD_LAZY);
54 if (handle == NULL) {
55 fatalf("inittls: failed to dlopen main program");
56 return;
57 }
58 // android_get_device_api_level is introduced in Android Q, so its mere presence
59 // is enough.
60 get_ver = dlsym(handle, "android_get_device_api_level");
61 dlclose(handle);
62 if (get_ver != NULL) {
63 off = (void *)(TLS_SLOT_APP*sizeof(void *));
64 // tlsg is initialized to Q's free TLS slot. Verify it while we're here.
65 if (*tlsg != off) {
66 fatalf("tlsg offset wrong, got %ld want %ld\n", *tlsg, off);
67 }
68 return;
69 }
70
71 err = pthread_key_create(&k, nil);
72 if(err != 0) {
73 fatalf("pthread_key_create failed: %d", err);
74 }
75 pthread_setspecific(k, (void*)magic1);
76 // If thread local slots are laid out as we expect, our magic word will
77 // be located at some low offset from tlsbase. However, just in case something went
78 // wrong, the search is limited to sensible offsets. PTHREAD_KEYS_MAX was the
79 // original limit, but issue 19472 made a higher limit necessary.
80 for (i=0; i<384; i++) {
81 if (*(tlsbase+i) == (void*)magic1) {
82 *tlsg = (void*)(i*sizeof(void *));
83 pthread_setspecific(k, 0);
84 return;
85 }
86 }
87 fatalf("inittls: could not find pthread key");
88 }
89
90 void (*x_cgo_inittls)(void **tlsg, void **tlsbase) = inittls;
91