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/*
* mini-exceptions-native-unwinder.c: libcorkscrew-based native unwinder
*
* Authors:
* Alex Rønne Petersen (alexrp@xamarin.com)
*
* Copyright 2015 Xamarin, Inc (http://www.xamarin.com)
* Licensed under the MIT license. See LICENSE file in the project root for full license information.
*/
#include <config.h>
#include <mono/utils/mono-logger-internals.h>
/*
* Attempt to handle native SIGSEGVs with libunwind or libcorkscrew.
*/
#ifdef HAVE_SIGNAL_H
#include <signal.h>
#endif
#include <mono/utils/mono-signal-handler.h>
#include "mini.h"
#if defined (PLATFORM_ANDROID)
#include <signal.h>
#include <sys/types.h>
#include <mono/utils/mono-dl.h>
#define UNW_LOCAL_ONLY
#undef _U /* ctype.h apparently defines this and it screws up the libunwind headers. */
#include "../../external/android-libunwind/include/libunwind.h"
#define _U 0x01
#define FUNC_NAME_LENGTH 512
#define FRAMES_TO_UNWIND 256
/* Expand the SYM argument. */
#define LOAD_SYM(DL, ERR, SYM, VAR) _LOAD_SYM(DL, ERR, SYM, VAR)
#define _LOAD_SYM(DL, ERR, SYM, VAR) \
do { \
if ((ERR = mono_dl_symbol (DL, #SYM, (void **) &VAR))) { \
mono_dl_close (DL); \
return ERR; \
} \
} while (0)
typedef int (*unw_init_local_t) (unw_cursor_t *, unw_context_t *);
typedef int (*unw_get_reg_t) (unw_cursor_t *, int, unw_word_t *);
typedef int (*unw_get_proc_name_t) (unw_cursor_t *, char *, size_t, unw_word_t *);
typedef int (*unw_step_t) (unw_cursor_t *);
static char *
mono_extension_handle_native_sigsegv_libunwind (void *ctx, MONO_SIG_HANDLER_INFO_TYPE *info)
{
char *dl_err;
int unw_err;
unw_init_local_t unw_init_local_fn;
unw_get_reg_t unw_get_reg_fn;
unw_get_proc_name_t unw_get_proc_name_fn;
unw_step_t unw_step_fn;
unw_cursor_t cursor;
size_t frames = 0;
MonoDl *dl = mono_dl_open ("libunwind.so", MONO_DL_LAZY, &dl_err);
if (!dl)
return dl_err;
LOAD_SYM (dl, dl_err, UNW_OBJ (init_local), unw_init_local_fn);
LOAD_SYM (dl, dl_err, UNW_OBJ (get_reg), unw_get_reg_fn);
LOAD_SYM (dl, dl_err, UNW_OBJ (get_proc_name), unw_get_proc_name_fn);
LOAD_SYM (dl, dl_err, UNW_OBJ (step), unw_step_fn);
if ((unw_err = unw_init_local_fn (&cursor, ctx))) {
mono_dl_close (dl);
return g_strdup_printf ("unw_init_local () returned %d", unw_err);
}
do {
int reg_err;
unw_word_t ip, off;
char name [FUNC_NAME_LENGTH];
if ((reg_err = unw_get_reg_fn (&cursor, UNW_REG_IP, &ip))) {
mono_runtime_printf_err ("unw_get_reg (UNW_REG_IP) returned %d", reg_err);
break;
}
reg_err = unw_get_proc_name_fn (&cursor, name, FUNC_NAME_LENGTH, &off);
if (reg_err == -UNW_ENOINFO)
strcpy (name, "???");
mono_runtime_printf_err (" at %s+%zu [0x%zx]", name, off, ip);
unw_err = unw_step_fn (&cursor);
frames++;
} while (unw_err > 0 && frames < FRAMES_TO_UNWIND);
if (unw_err < 0)
mono_runtime_printf_err ("unw_step () returned %d", unw_err);
mono_dl_close (dl);
return NULL;
}
/*
* This code is based on the AOSP header system/core/include/corkscrew/backtrace.h.
*
* This is copied here because libcorkscrew is not a stable library and the header (and
* other headers that it depends on) will eventually go away.
*
* We can probably remove this one day when libunwind becomes the norm.
*/
typedef struct {
uintptr_t absolute_pc;
uintptr_t stack_top;
size_t stack_size;
} backtrace_frame_t;
typedef struct {
uintptr_t relative_pc;
uintptr_t relative_symbol_addr;
char *map_name;
char *symbol_name;
char *demangled_name;
} backtrace_symbol_t;
typedef void (*get_backtrace_symbols_t) (const backtrace_frame_t *backtrace, size_t frames, backtrace_symbol_t *backtrace_symbols);
typedef void (*free_backtrace_symbols_t) (backtrace_symbol_t *backtrace_symbols, size_t frames);
enum {
MAX_BACKTRACE_LINE_LENGTH = 800,
};
/* Internals that we're exploiting to work in a signal handler. Only works on ARM/x86. */
typedef struct map_info_t map_info_t;
typedef ssize_t (*unwind_backtrace_signal_arch_t) (siginfo_t *si, void *sc, const map_info_t *lst, backtrace_frame_t *bt, size_t ignore_depth, size_t max_depth);
typedef map_info_t *(*acquire_my_map_info_list_t) (void);
typedef void (*release_my_map_info_list_t) (map_info_t *milist);
static char *
mono_extension_handle_native_sigsegv_libcorkscrew (void *ctx, MONO_SIG_HANDLER_INFO_TYPE *info)
{
#if defined (__arm__) || defined (__i386__)
char *dl_err;
get_backtrace_symbols_t get_backtrace_symbols;
free_backtrace_symbols_t free_backtrace_symbols;
unwind_backtrace_signal_arch_t unwind_backtrace_signal_arch;
acquire_my_map_info_list_t acquire_my_map_info_list;
release_my_map_info_list_t release_my_map_info_list;
backtrace_frame_t frames [FRAMES_TO_UNWIND];
backtrace_symbol_t symbols [FRAMES_TO_UNWIND];
map_info_t *map_info;
ssize_t frames_unwound;
size_t i;
MonoDl *dl = mono_dl_open ("libcorkscrew.so", MONO_DL_LAZY, &dl_err);
if (!dl)
return dl_err;
LOAD_SYM (dl, dl_err, get_backtrace_symbols, get_backtrace_symbols);
LOAD_SYM (dl, dl_err, free_backtrace_symbols, free_backtrace_symbols);
LOAD_SYM (dl, dl_err, unwind_backtrace_signal_arch, unwind_backtrace_signal_arch);
LOAD_SYM (dl, dl_err, acquire_my_map_info_list, acquire_my_map_info_list);
LOAD_SYM (dl, dl_err, release_my_map_info_list, release_my_map_info_list);
map_info = acquire_my_map_info_list ();
frames_unwound = unwind_backtrace_signal_arch (info, ctx, map_info, frames, 0, FRAMES_TO_UNWIND);
release_my_map_info_list (map_info);
if (frames_unwound == -1) {
mono_dl_close (dl);
return g_strdup ("unwind_backtrace_signal_arch () returned -1");
}
get_backtrace_symbols (frames, frames_unwound, symbols);
for (i = 0; i < frames_unwound; i++) {
backtrace_frame_t *frame = frames + i;
backtrace_symbol_t *symbol = symbols + i;
const char *name = symbol->demangled_name ? symbol->demangled_name : (symbol->symbol_name ? symbol->symbol_name : "???");
uintptr_t off = symbol->relative_pc - symbol->relative_symbol_addr;
uintptr_t ip = frame->absolute_pc;
mono_runtime_printf_err (" at %s+%zu [0x%zx]", name, off, ip);
}
free_backtrace_symbols (symbols, frames_unwound);
mono_dl_close (dl);
return NULL;
#else
return g_strdup ("libcorkscrew is only supported on 32-bit ARM/x86");
#endif
}
void
mono_exception_native_unwind (void *ctx, MONO_SIG_HANDLER_INFO_TYPE *info)
{
char *unwind_err, *corkscrew_err;
mono_runtime_printf_err ("\nAttempting native Android stacktrace:\n");
unwind_err = mono_extension_handle_native_sigsegv_libunwind (ctx, info);
if (unwind_err) {
corkscrew_err = mono_extension_handle_native_sigsegv_libcorkscrew (ctx, info);
if (corkscrew_err) {
mono_runtime_printf_err ("\tCould not unwind with `libunwind.so`: %s", unwind_err);
mono_runtime_printf_err ("\tCould not unwind with `libcorkscrew.so`: %s", corkscrew_err);
mono_runtime_printf_err ("\n\tNo options left to get a native stacktrace :-(");
g_free (corkscrew_err);
}
g_free (unwind_err);
}
}
#else
void
mono_exception_native_unwind (void *ctx, MONO_SIG_HANDLER_INFO_TYPE *info)
{
}
#endif
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