/**************************************************************************/ /* */ /* OCaml */ /* */ /* Xavier Leroy, projet Gallium, INRIA Rocquencourt */ /* */ /* Copyright 2006 Institut National de Recherche en Informatique et */ /* en Automatique. */ /* */ /* All rights reserved. This file is distributed under the terms of */ /* the GNU Lesser General Public License version 2.1, with the */ /* special exception on linking described in the file LICENSE. */ /* */ /**************************************************************************/ #define CAML_INTERNALS /* Stack backtrace for uncaught exceptions */ #include #include #include #include "caml/alloc.h" #include "caml/backtrace.h" #include "caml/backtrace_prim.h" #include "caml/memory.h" #include "caml/misc.h" #include "caml/mlvalues.h" #include "caml/stack.h" /* Returns the next frame descriptor (or NULL if none is available), and updates *pc and *sp to point to the following one. */ frame_descr * caml_next_frame_descriptor(uintnat * pc, char ** sp) { frame_descr * d; uintnat h; while (1) { h = Hash_retaddr(*pc); while (1) { d = caml_frame_descriptors[h]; if (d == NULL) return NULL; /* happens if some code compiled without -g */ if (d->retaddr == *pc) break; h = (h+1) & caml_frame_descriptors_mask; } /* Skip to next frame */ if (d->frame_size != 0xFFFF) { /* Regular frame, update sp/pc and return the frame descriptor */ *sp += (d->frame_size & 0xFFFC); *pc = Saved_return_address(*sp); #ifdef Mask_already_scanned *pc = Mask_already_scanned(*pc); #endif return d; } else { /* Special frame marking the top of a stack chunk for an ML callback. Skip C portion of stack and continue with next ML stack chunk. */ struct caml_context * next_context = Callback_link(*sp); *sp = next_context->bottom_of_stack; *pc = next_context->last_retaddr; /* A null sp means no more ML stack chunks; stop here. */ if (*sp == NULL) return NULL; } } } int caml_alloc_backtrace_buffer(void){ CAMLassert(caml_backtrace_pos == 0); caml_backtrace_buffer = caml_stat_alloc_noexc(BACKTRACE_BUFFER_SIZE * sizeof(backtrace_slot)); if (caml_backtrace_buffer == NULL) return -1; return 0; } /* Stores the return addresses contained in the given stack fragment into the backtrace array ; this version is performance-sensitive as it is called at each [raise] in a program compiled with [-g], so we preserved the global, statically bounded buffer of the old implementation -- before the more flexible [caml_get_current_callstack] was implemented. */ void caml_stash_backtrace(value exn, uintnat pc, char * sp, char * trapsp) { if (exn != caml_backtrace_last_exn) { caml_backtrace_pos = 0; caml_backtrace_last_exn = exn; } if (caml_backtrace_buffer == NULL && caml_alloc_backtrace_buffer() == -1) return; /* iterate on each frame */ while (1) { frame_descr * descr = caml_next_frame_descriptor(&pc, &sp); if (descr == NULL) return; /* store its descriptor in the backtrace buffer */ if (caml_backtrace_pos >= BACKTRACE_BUFFER_SIZE) return; caml_backtrace_buffer[caml_backtrace_pos++] = (backtrace_slot) descr; /* Stop when we reach the current exception handler */ if (sp > trapsp) return; } } /* Stores upto [max_frames_value] frames of the current call stack to return to the user. This is used not in an exception-raising context, but only when the user requests to save the trace (hopefully less often). Instead of using a bounded buffer as [caml_stash_backtrace], we first traverse the stack to compute the right size, then allocate space for the trace. */ CAMLprim value caml_get_current_callstack(value max_frames_value) { CAMLparam1(max_frames_value); CAMLlocal1(trace); /* we use `intnat` here because, were it only `int`, passing `max_int` from the OCaml side would overflow on 64bits machines. */ intnat max_frames = Long_val(max_frames_value); intnat trace_size; /* first compute the size of the trace */ { uintnat pc = caml_last_return_address; char * sp = caml_bottom_of_stack; char * limitsp = caml_top_of_stack; trace_size = 0; while (1) { frame_descr * descr = caml_next_frame_descriptor(&pc, &sp); if (descr == NULL) break; if (trace_size >= max_frames) break; ++trace_size; if (sp > limitsp) break; } } trace = caml_alloc((mlsize_t) trace_size, 0); /* then collect the trace */ { uintnat pc = caml_last_return_address; char * sp = caml_bottom_of_stack; intnat trace_pos; for (trace_pos = 0; trace_pos < trace_size; trace_pos++) { frame_descr * descr = caml_next_frame_descriptor(&pc, &sp); CAMLassert(descr != NULL); Field(trace, trace_pos) = Val_backtrace_slot((backtrace_slot) descr); } } CAMLreturn(trace); } debuginfo caml_debuginfo_extract(backtrace_slot slot) { uintnat infoptr; frame_descr * d = (frame_descr *)slot; if ((d->frame_size & 1) == 0) { return NULL; } /* Recover debugging info */ infoptr = ((uintnat) d + sizeof(char *) + sizeof(short) + sizeof(short) + sizeof(short) * d->num_live + sizeof(frame_descr *) - 1) & -sizeof(frame_descr *); return *((debuginfo*)infoptr); } debuginfo caml_debuginfo_next(debuginfo dbg) { uint32_t * infoptr; if (dbg == NULL) return NULL; infoptr = dbg; infoptr += 2; /* Two packed info fields */ return *((debuginfo*)infoptr); } /* Extract location information for the given frame descriptor */ void caml_debuginfo_location(debuginfo dbg, /*out*/ struct caml_loc_info * li) { uint32_t info1, info2; /* If no debugging information available, print nothing. When everything is compiled with -g, this corresponds to compiler-inserted re-raise operations. */ if (dbg == NULL) { li->loc_valid = 0; li->loc_is_raise = 1; li->loc_is_inlined = 0; return; } /* Recover debugging info */ info1 = ((uint32_t *)dbg)[0]; info2 = ((uint32_t *)dbg)[1]; /* Format of the two info words: llllllllllllllllllll aaaaaaaa bbbbbbbbbb nnnnnnnnnnnnnnnnnnnnnnnn kk 44 36 26 2 0 (32+12) (32+4) k ( 2 bits): 0 if it's a call 1 if it's a raise n (24 bits): offset (in 4-byte words) of file name relative to dbg l (20 bits): line number a ( 8 bits): beginning of character range b (10 bits): end of character range */ li->loc_valid = 1; li->loc_is_raise = (info1 & 3) == 1; li->loc_is_inlined = caml_debuginfo_next(dbg) != NULL; li->loc_filename = (char *) dbg + (info1 & 0x3FFFFFC); li->loc_lnum = info2 >> 12; li->loc_startchr = (info2 >> 4) & 0xFF; li->loc_endchr = ((info2 & 0xF) << 6) | (info1 >> 26); } CAMLprim value caml_add_debug_info(backtrace_slot start, value size, value events) { return Val_unit; } CAMLprim value caml_remove_debug_info(backtrace_slot start) { return Val_unit; } int caml_debug_info_available(void) { return 1; }