Text file src/pkg/runtime/cgo/gcc_android.c

     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
    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/master/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
    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;

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