/* Subroutines needed for unwinding stack frames for exception handling. */ /* Copyright (C) 1997-2024 Free Software Foundation, Inc. Contributed by Jason Merrill . This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. Under Section 7 of GPL version 3, you are granted additional permissions described in the GCC Runtime Library Exception, version 3.1, as published by the Free Software Foundation. You should have received a copy of the GNU General Public License and a copy of the GCC Runtime Library Exception along with this program; see the files COPYING3 and COPYING.RUNTIME respectively. If not, see . */ #ifndef _Unwind_Find_FDE #include "tconfig.h" #include "tsystem.h" #include "coretypes.h" #include "tm.h" #include "libgcc_tm.h" #include "dwarf2.h" #include "unwind.h" #define NO_BASE_OF_ENCODED_VALUE #include "unwind-pe.h" #include "unwind-dw2-fde.h" #include "gthr.h" #else #if (defined(__GTHREAD_MUTEX_INIT) || defined(__GTHREAD_MUTEX_INIT_FUNCTION)) \ && defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4) #define ATOMIC_FDE_FAST_PATH 1 #endif #endif typedef __UINTPTR_TYPE__ uintptr_type; #ifdef ATOMIC_FDE_FAST_PATH #include "unwind-dw2-btree.h" static struct btree registered_frames; static struct btree registered_objects; static bool in_shutdown; static void release_registered_frames (void) __attribute__ ((destructor)); static void release_registered_frames (void) { /* Release the b-tree and all frames. Frame releases that happen later are * silently ignored */ btree_destroy (®istered_frames); btree_destroy (®istered_objects); in_shutdown = true; } static void get_pc_range (const struct object *ob, uintptr_type *range); #else /* Without fast path frame deregistration must always succeed. */ static const int in_shutdown = 0; /* The unseen_objects list contains objects that have been registered but not yet categorized in any way. The seen_objects list has had its pc_begin and count fields initialized at minimum, and is sorted by decreasing value of pc_begin. */ static struct object *unseen_objects; static struct object *seen_objects; #endif #ifdef __GTHREAD_MUTEX_INIT static __gthread_mutex_t object_mutex = __GTHREAD_MUTEX_INIT; #define init_object_mutex_once() #else #ifdef __GTHREAD_MUTEX_INIT_FUNCTION static __gthread_mutex_t object_mutex; static void init_object_mutex (void) { __GTHREAD_MUTEX_INIT_FUNCTION (&object_mutex); } static void init_object_mutex_once (void) { static __gthread_once_t once = __GTHREAD_ONCE_INIT; __gthread_once (&once, init_object_mutex); } #else /* ??? Several targets include this file with stubbing parts of gthr.h and expect no locking to be done. */ #define init_object_mutex_once() static __gthread_mutex_t object_mutex; #endif #endif #ifdef ATOMIC_FDE_FAST_PATH // Register the pc range for a given object in the lookup structure. static void register_pc_range_for_object (uintptr_type begin, struct object *ob) { // Register the object itself to know the base pointer on deregistration. btree_insert (®istered_objects, begin, 1, ob); // Register the frame in the b-tree uintptr_type range[2]; get_pc_range (ob, range); btree_insert (®istered_frames, range[0], range[1] - range[0], ob); } #endif /* Called from crtbegin.o to register the unwind info for an object. */ void __register_frame_info_bases (const void *begin, struct object *ob, void *tbase, void *dbase) { /* If .eh_frame is empty, don't register at all. */ if ((const uword *) begin == 0 || *(const uword *) begin == 0) return; ob->pc_begin = (void *)-1; ob->tbase = tbase; ob->dbase = dbase; ob->u.single = begin; ob->s.i = 0; ob->s.b.encoding = DW_EH_PE_omit; #ifdef DWARF2_OBJECT_END_PTR_EXTENSION ob->fde_end = NULL; #endif #ifdef ATOMIC_FDE_FAST_PATH register_pc_range_for_object ((uintptr_type) begin, ob); #else init_object_mutex_once (); __gthread_mutex_lock (&object_mutex); ob->next = unseen_objects; unseen_objects = ob; __gthread_mutex_unlock (&object_mutex); #endif } void __register_frame_info (const void *begin, struct object *ob) { __register_frame_info_bases (begin, ob, 0, 0); } void __register_frame (void *begin) { struct object *ob; /* If .eh_frame is empty, don't register at all. */ if (*(uword *) begin == 0) return; ob = malloc (sizeof (struct object)); __register_frame_info (begin, ob); } /* Similar, but BEGIN is actually a pointer to a table of unwind entries for different translation units. Called from the file generated by collect2. */ void __register_frame_info_table_bases (void *begin, struct object *ob, void *tbase, void *dbase) { ob->pc_begin = (void *)-1; ob->tbase = tbase; ob->dbase = dbase; ob->u.array = begin; ob->s.i = 0; ob->s.b.from_array = 1; ob->s.b.encoding = DW_EH_PE_omit; #ifdef ATOMIC_FDE_FAST_PATH register_pc_range_for_object ((uintptr_type) begin, ob); #else init_object_mutex_once (); __gthread_mutex_lock (&object_mutex); ob->next = unseen_objects; unseen_objects = ob; __gthread_mutex_unlock (&object_mutex); #endif } void __register_frame_info_table (void *begin, struct object *ob) { __register_frame_info_table_bases (begin, ob, 0, 0); } void __register_frame_table (void *begin) { struct object *ob = malloc (sizeof (struct object)); __register_frame_info_table (begin, ob); } /* Called from crtbegin.o to deregister the unwind info for an object. */ /* ??? Glibc has for a while now exported __register_frame_info and __deregister_frame_info. If we call __register_frame_info_bases from crtbegin (wherein it is declared weak), and this object does not get pulled from libgcc.a for other reasons, then the invocation of __deregister_frame_info will be resolved from glibc. Since the registration did not happen there, we'll die. Therefore, declare a new deregistration entry point that does the exact same thing, but will resolve to the same library as implements __register_frame_info_bases. */ void * __deregister_frame_info_bases (const void *begin) { struct object *ob = 0; /* If .eh_frame is empty, we haven't registered. */ if ((const uword *) begin == 0 || *(const uword *) begin == 0) return ob; #ifdef ATOMIC_FDE_FAST_PATH // Find the originally registered object to get the base pointer. ob = btree_remove (®istered_objects, (uintptr_type) begin); // Remove the corresponding PC range. if (ob) { uintptr_type range[2]; get_pc_range (ob, range); if (range[0] != range[1]) btree_remove (®istered_frames, range[0]); } // Deallocate the sort array if any. if (ob && ob->s.b.sorted) { free (ob->u.sort); } #else init_object_mutex_once (); __gthread_mutex_lock (&object_mutex); struct object **p; for (p = &unseen_objects; *p ; p = &(*p)->next) if ((*p)->u.single == begin) { ob = *p; *p = ob->next; goto out; } for (p = &seen_objects; *p ; p = &(*p)->next) if ((*p)->s.b.sorted) { if ((*p)->u.sort->orig_data == begin) { ob = *p; *p = ob->next; free (ob->u.sort); goto out; } } else { if ((*p)->u.single == begin) { ob = *p; *p = ob->next; goto out; } } out: __gthread_mutex_unlock (&object_mutex); #endif // If we didn't find anything in the lookup data structures then they // were either already destroyed or we tried to remove an empty range. gcc_assert (in_shutdown || ob); return (void *) ob; } void * __deregister_frame_info (const void *begin) { return __deregister_frame_info_bases (begin); } void __deregister_frame (void *begin) { /* If .eh_frame is empty, we haven't registered. */ if (*(uword *) begin != 0) free (__deregister_frame_info (begin)); } /* Like base_of_encoded_value, but take the base from a struct object instead of an _Unwind_Context. */ static _Unwind_Ptr base_from_object (unsigned char encoding, const struct object *ob) { if (encoding == DW_EH_PE_omit) return 0; switch (encoding & 0x70) { case DW_EH_PE_absptr: case DW_EH_PE_pcrel: case DW_EH_PE_aligned: return 0; case DW_EH_PE_textrel: return (_Unwind_Ptr) ob->tbase; case DW_EH_PE_datarel: return (_Unwind_Ptr) ob->dbase; default: gcc_unreachable (); } } /* Return the FDE pointer encoding from the CIE. */ /* ??? This is a subset of extract_cie_info from unwind-dw2.c. */ static int get_cie_encoding (const struct dwarf_cie *cie) { const unsigned char *aug, *p; _Unwind_Ptr dummy; _uleb128_t utmp; _sleb128_t stmp; aug = cie->augmentation; p = aug + strlen ((const char *)aug) + 1; /* Skip the augmentation string. */ if (__builtin_expect (cie->version >= 4, 0)) { if (p[0] != sizeof (void *) || p[1] != 0) return DW_EH_PE_omit; /* We are not prepared to handle unexpected address sizes or segment selectors. */ p += 2; /* Skip address size and segment size. */ } if (aug[0] != 'z') return DW_EH_PE_absptr; p = read_uleb128 (p, &utmp); /* Skip code alignment. */ p = read_sleb128 (p, &stmp); /* Skip data alignment. */ if (cie->version == 1) /* Skip return address column. */ p++; else p = read_uleb128 (p, &utmp); aug++; /* Skip 'z' */ p = read_uleb128 (p, &utmp); /* Skip augmentation length. */ while (1) { /* This is what we're looking for. */ if (*aug == 'R') return *p; /* Personality encoding and pointer. */ else if (*aug == 'P') { /* ??? Avoid dereferencing indirect pointers, since we're faking the base address. Gotta keep DW_EH_PE_aligned intact, however. */ p = read_encoded_value_with_base (*p & 0x7F, 0, p + 1, &dummy); } /* LSDA encoding. */ else if (*aug == 'L') p++; /* aarch64 b-key pointer authentication. */ else if (*aug == 'B') p++; /* Otherwise end of string, or unknown augmentation. */ else return DW_EH_PE_absptr; aug++; } } static inline int get_fde_encoding (const struct dwarf_fde *f) { return get_cie_encoding (get_cie (f)); } /* Sorting an array of FDEs by address. (Ideally we would have the linker sort the FDEs so we don't have to do it at run time. But the linkers are not yet prepared for this.) */ /* Comparison routines. Three variants of increasing complexity. */ static int fde_unencoded_compare (struct object *ob __attribute__((unused)), const fde *x, const fde *y) { _Unwind_Ptr x_ptr, y_ptr; memcpy (&x_ptr, x->pc_begin, sizeof (_Unwind_Ptr)); memcpy (&y_ptr, y->pc_begin, sizeof (_Unwind_Ptr)); if (x_ptr > y_ptr) return 1; if (x_ptr < y_ptr) return -1; return 0; } static int fde_single_encoding_compare (struct object *ob, const fde *x, const fde *y) { _Unwind_Ptr base, x_ptr, y_ptr; base = base_from_object (ob->s.b.encoding, ob); read_encoded_value_with_base (ob->s.b.encoding, base, x->pc_begin, &x_ptr); read_encoded_value_with_base (ob->s.b.encoding, base, y->pc_begin, &y_ptr); if (x_ptr > y_ptr) return 1; if (x_ptr < y_ptr) return -1; return 0; } static int fde_mixed_encoding_compare (struct object *ob, const fde *x, const fde *y) { int x_encoding, y_encoding; _Unwind_Ptr x_ptr, y_ptr; x_encoding = get_fde_encoding (x); read_encoded_value_with_base (x_encoding, base_from_object (x_encoding, ob), x->pc_begin, &x_ptr); y_encoding = get_fde_encoding (y); read_encoded_value_with_base (y_encoding, base_from_object (y_encoding, ob), y->pc_begin, &y_ptr); if (x_ptr > y_ptr) return 1; if (x_ptr < y_ptr) return -1; return 0; } typedef int (*fde_compare_t) (struct object *, const fde *, const fde *); // The extractor functions compute the pointer values for a block of // fdes. The block processing hides the call overhead. static void fde_unencoded_extract (struct object *ob __attribute__ ((unused)), _Unwind_Ptr *target, const fde **x, int count) { for (int index = 0; index < count; ++index) memcpy (target + index, x[index]->pc_begin, sizeof (_Unwind_Ptr)); } static void fde_single_encoding_extract (struct object *ob, _Unwind_Ptr *target, const fde **x, int count) { _Unwind_Ptr base; base = base_from_object (ob->s.b.encoding, ob); for (int index = 0; index < count; ++index) read_encoded_value_with_base (ob->s.b.encoding, base, x[index]->pc_begin, target + index); } static void fde_mixed_encoding_extract (struct object *ob, _Unwind_Ptr *target, const fde **x, int count) { for (int index = 0; index < count; ++index) { int encoding = get_fde_encoding (x[index]); read_encoded_value_with_base (encoding, base_from_object (encoding, ob), x[index]->pc_begin, target + index); } } typedef void (*fde_extractor_t) (struct object *, _Unwind_Ptr *, const fde **, int); // Data is sorted using radix sort if possible, using an temporary // auxiliary data structure of the same size as the input. When running // out of memory do in-place heap sort. struct fde_accumulator { struct fde_vector *linear; struct fde_vector *aux; }; static inline int start_fde_sort (struct fde_accumulator *accu, size_t count) { size_t size; if (! count) return 0; size = sizeof (struct fde_vector) + sizeof (const fde *) * count; if ((accu->linear = malloc (size))) { accu->linear->count = 0; if ((accu->aux = malloc (size))) accu->aux->count = 0; return 1; } else return 0; } static inline void fde_insert (struct fde_accumulator *accu, const fde *this_fde) { if (accu->linear) accu->linear->array[accu->linear->count++] = this_fde; } #define SWAP(x,y) do { const fde * tmp = x; x = y; y = tmp; } while (0) /* Convert a semi-heap to a heap. A semi-heap is a heap except possibly for the first (root) node; push it down to its rightful place. */ static void frame_downheap (struct object *ob, fde_compare_t fde_compare, const fde **a, int lo, int hi) { int i, j; for (i = lo, j = 2*i+1; j < hi; j = 2*i+1) { if (j+1 < hi && fde_compare (ob, a[j], a[j+1]) < 0) ++j; if (fde_compare (ob, a[i], a[j]) < 0) { SWAP (a[i], a[j]); i = j; } else break; } } /* This is O(n log(n)). BSD/OS defines heapsort in stdlib.h, so we must use a name that does not conflict. */ static void frame_heapsort (struct object *ob, fde_compare_t fde_compare, struct fde_vector *erratic) { /* For a description of this algorithm, see: Samuel P. Harbison, Guy L. Steele Jr.: C, a reference manual, 2nd ed., p. 60-61. */ const fde ** a = erratic->array; /* A portion of the array is called a "heap" if for all i>=0: If i and 2i+1 are valid indices, then a[i] >= a[2i+1]. If i and 2i+2 are valid indices, then a[i] >= a[2i+2]. */ size_t n = erratic->count; int m; /* Expand our heap incrementally from the end of the array, heapifying each resulting semi-heap as we go. After each step, a[m] is the top of a heap. */ for (m = n/2-1; m >= 0; --m) frame_downheap (ob, fde_compare, a, m, n); /* Shrink our heap incrementally from the end of the array, first swapping out the largest element a[0] and then re-heapifying the resulting semi-heap. After each step, a[0..m) is a heap. */ for (m = n-1; m >= 1; --m) { SWAP (a[0], a[m]); frame_downheap (ob, fde_compare, a, 0, m); } #undef SWAP } // Radix sort data in V1 using V2 as aux memory. Runtime O(n). static inline void fde_radixsort (struct object *ob, fde_extractor_t fde_extractor, struct fde_vector *v1, struct fde_vector *v2) { #define FANOUTBITS 8 #define FANOUT (1 << FANOUTBITS) #define BLOCKSIZE 128 const unsigned rounds = (__CHAR_BIT__ * sizeof (_Unwind_Ptr) + FANOUTBITS - 1) / FANOUTBITS; const fde **a1 = v1->array, **a2 = v2->array; _Unwind_Ptr ptrs[BLOCKSIZE + 1]; unsigned n = v1->count; for (unsigned round = 0; round != rounds; ++round) { unsigned counts[FANOUT] = {0}; unsigned violations = 0; // Count the number of elements per bucket and check if we are already // sorted. _Unwind_Ptr last = 0; for (unsigned i = 0; i < n;) { unsigned chunk = ((n - i) <= BLOCKSIZE) ? (n - i) : BLOCKSIZE; fde_extractor (ob, ptrs + 1, a1 + i, chunk); ptrs[0] = last; for (unsigned j = 0; j < chunk; ++j) { unsigned b = (ptrs[j + 1] >> (round * FANOUTBITS)) & (FANOUT - 1); counts[b]++; // Use summation instead of an if to eliminate branches. violations += ptrs[j + 1] < ptrs[j]; } i += chunk; last = ptrs[chunk]; } // Stop if we are already sorted. if (!violations) { break; } // Compute the prefix sum. unsigned sum = 0; for (unsigned i = 0; i != FANOUT; ++i) { unsigned s = sum; sum += counts[i]; counts[i] = s; } // Place all elements. for (unsigned i = 0; i < n;) { unsigned chunk = ((n - i) <= BLOCKSIZE) ? (n - i) : BLOCKSIZE; fde_extractor (ob, ptrs, a1 + i, chunk); for (unsigned j = 0; j < chunk; ++j) { unsigned b = (ptrs[j] >> (round * FANOUTBITS)) & (FANOUT - 1); a2[counts[b]++] = a1[i + j]; } i += chunk; } // Swap a1 and a2. const fde **tmp = a1; a1 = a2; a2 = tmp; } #undef BLOCKSIZE #undef FANOUT #undef FANOUTBITS // The data is in a1 now, move in place if needed. if (a1 != v1->array) memcpy (v1->array, a1, sizeof (const fde *) * n); } static inline void end_fde_sort (struct object *ob, struct fde_accumulator *accu, size_t count) { gcc_assert (!accu->linear || accu->linear->count == count); if (accu->aux) { fde_extractor_t fde_extractor; if (ob->s.b.mixed_encoding) fde_extractor = fde_mixed_encoding_extract; else if (ob->s.b.encoding == DW_EH_PE_absptr) fde_extractor = fde_unencoded_extract; else fde_extractor = fde_single_encoding_extract; fde_radixsort (ob, fde_extractor, accu->linear, accu->aux); free (accu->aux); } else { fde_compare_t fde_compare; if (ob->s.b.mixed_encoding) fde_compare = fde_mixed_encoding_compare; else if (ob->s.b.encoding == DW_EH_PE_absptr) fde_compare = fde_unencoded_compare; else fde_compare = fde_single_encoding_compare; /* We've not managed to malloc an aux array, so heap sort in the linear one. */ frame_heapsort (ob, fde_compare, accu->linear); } } /* Inspect the fde array beginning at this_fde. This function can be used either in query mode (RANGE is not null, OB is const), or in update mode (RANGE is null, OB is modified). In query mode the function computes the range of PC values and stores it in RANGE. In update mode it updates encoding, mixed_encoding, and pc_begin for OB. Return the number of fdes encountered along the way. */ static size_t classify_object_over_fdes (struct object *ob, const fde *this_fde, uintptr_type *range) { const struct dwarf_cie *last_cie = 0; size_t count = 0; int encoding = DW_EH_PE_absptr; _Unwind_Ptr base = 0; for (; ! last_fde (ob, this_fde); this_fde = next_fde (this_fde)) { const struct dwarf_cie *this_cie; _Unwind_Ptr mask, pc_begin; /* Skip CIEs. */ if (this_fde->CIE_delta == 0) continue; /* Determine the encoding for this FDE. Note mixed encoded objects for later. */ this_cie = get_cie (this_fde); if (this_cie != last_cie) { last_cie = this_cie; encoding = get_cie_encoding (this_cie); if (encoding == DW_EH_PE_omit) return -1; base = base_from_object (encoding, ob); if (!range) { if (ob->s.b.encoding == DW_EH_PE_omit) ob->s.b.encoding = encoding; else if (ob->s.b.encoding != encoding) ob->s.b.mixed_encoding = 1; } } const unsigned char *p; p = read_encoded_value_with_base (encoding, base, this_fde->pc_begin, &pc_begin); /* Take care to ignore link-once functions that were removed. In these cases, the function address will be NULL, but if the encoding is smaller than a pointer a true NULL may not be representable. Assume 0 in the representable bits is NULL. */ mask = size_of_encoded_value (encoding); if (mask < sizeof (void *)) mask = (((_Unwind_Ptr) 1) << (mask << 3)) - 1; else mask = -1; if ((pc_begin & mask) == 0) continue; count += 1; if (range) { _Unwind_Ptr pc_range, pc_end; read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range); pc_end = pc_begin + pc_range; if ((!range[0]) && (!range[1])) { range[0] = pc_begin; range[1] = pc_end; } else { if (pc_begin < range[0]) range[0] = pc_begin; if (pc_end > range[1]) range[1] = pc_end; } } else { if ((void *) pc_begin < ob->pc_begin) ob->pc_begin = (void *) pc_begin; } } return count; } static void add_fdes (struct object *ob, struct fde_accumulator *accu, const fde *this_fde) { const struct dwarf_cie *last_cie = 0; int encoding = ob->s.b.encoding; _Unwind_Ptr base = base_from_object (ob->s.b.encoding, ob); for (; ! last_fde (ob, this_fde); this_fde = next_fde (this_fde)) { const struct dwarf_cie *this_cie; /* Skip CIEs. */ if (this_fde->CIE_delta == 0) continue; if (ob->s.b.mixed_encoding) { /* Determine the encoding for this FDE. Note mixed encoded objects for later. */ this_cie = get_cie (this_fde); if (this_cie != last_cie) { last_cie = this_cie; encoding = get_cie_encoding (this_cie); base = base_from_object (encoding, ob); } } if (encoding == DW_EH_PE_absptr) { _Unwind_Ptr ptr; memcpy (&ptr, this_fde->pc_begin, sizeof (_Unwind_Ptr)); if (ptr == 0) continue; } else { _Unwind_Ptr pc_begin, mask; read_encoded_value_with_base (encoding, base, this_fde->pc_begin, &pc_begin); /* Take care to ignore link-once functions that were removed. In these cases, the function address will be NULL, but if the encoding is smaller than a pointer a true NULL may not be representable. Assume 0 in the representable bits is NULL. */ mask = size_of_encoded_value (encoding); if (mask < sizeof (void *)) mask = (((_Unwind_Ptr) 1) << (mask << 3)) - 1; else mask = -1; if ((pc_begin & mask) == 0) continue; } fde_insert (accu, this_fde); } } /* Set up a sorted array of pointers to FDEs for a loaded object. We count up the entries before allocating the array because it's likely to be faster. We can be called multiple times, should we have failed to allocate a sorted fde array on a previous occasion. */ static inline void init_object (struct object* ob) { struct fde_accumulator accu; size_t count; count = ob->s.b.count; if (count == 0) { if (ob->s.b.from_array) { fde **p = ob->u.array; for (count = 0; *p; ++p) { size_t cur_count = classify_object_over_fdes (ob, *p, NULL); if (cur_count == (size_t) -1) goto unhandled_fdes; count += cur_count; } } else { count = classify_object_over_fdes (ob, ob->u.single, NULL); if (count == (size_t) -1) { static const fde terminator; unhandled_fdes: ob->s.i = 0; ob->s.b.encoding = DW_EH_PE_omit; ob->u.single = &terminator; return; } } /* The count field we have in the main struct object is somewhat limited, but should suffice for virtually all cases. If the counted value doesn't fit, re-write a zero. The worst that happens is that we re-count next time -- admittedly non-trivial in that this implies some 2M fdes, but at least we function. */ ob->s.b.count = count; if (ob->s.b.count != count) ob->s.b.count = 0; } if (!start_fde_sort (&accu, count)) return; if (ob->s.b.from_array) { fde **p; for (p = ob->u.array; *p; ++p) add_fdes (ob, &accu, *p); } else add_fdes (ob, &accu, ob->u.single); end_fde_sort (ob, &accu, count); /* Save the original fde pointer, since this is the key by which the DSO will deregister the object. */ accu.linear->orig_data = ob->u.single; ob->u.sort = accu.linear; #ifdef ATOMIC_FDE_FAST_PATH // We must update the sorted bit with an atomic operation struct object tmp; tmp.s.b = ob->s.b; tmp.s.b.sorted = 1; __atomic_store (&(ob->s.b), &(tmp.s.b), __ATOMIC_RELEASE); #else ob->s.b.sorted = 1; #endif } #ifdef ATOMIC_FDE_FAST_PATH /* Get the PC range for lookup */ static void get_pc_range (const struct object *ob, uintptr_type *range) { // It is safe to cast to non-const object* here as // classify_object_over_fdes does not modify ob in query mode. struct object *ncob = (struct object *) (uintptr_type) ob; range[0] = range[1] = 0; if (ob->s.b.sorted) { classify_object_over_fdes (ncob, ob->u.sort->orig_data, range); } else if (ob->s.b.from_array) { fde **p = ob->u.array; for (; *p; ++p) classify_object_over_fdes (ncob, *p, range); } else { classify_object_over_fdes (ncob, ob->u.single, range); } } #endif /* A linear search through a set of FDEs for the given PC. This is used when there was insufficient memory to allocate and sort an array. */ static const fde * linear_search_fdes (struct object *ob, const fde *this_fde, void *pc) { const struct dwarf_cie *last_cie = 0; int encoding = ob->s.b.encoding; _Unwind_Ptr base = base_from_object (ob->s.b.encoding, ob); for (; ! last_fde (ob, this_fde); this_fde = next_fde (this_fde)) { const struct dwarf_cie *this_cie; _Unwind_Ptr pc_begin, pc_range; /* Skip CIEs. */ if (this_fde->CIE_delta == 0) continue; if (ob->s.b.mixed_encoding) { /* Determine the encoding for this FDE. Note mixed encoded objects for later. */ this_cie = get_cie (this_fde); if (this_cie != last_cie) { last_cie = this_cie; encoding = get_cie_encoding (this_cie); base = base_from_object (encoding, ob); } } if (encoding == DW_EH_PE_absptr) { const _Unwind_Ptr *pc_array = (const _Unwind_Ptr *) this_fde->pc_begin; pc_begin = pc_array[0]; pc_range = pc_array[1]; if (pc_begin == 0) continue; } else { _Unwind_Ptr mask; const unsigned char *p; p = read_encoded_value_with_base (encoding, base, this_fde->pc_begin, &pc_begin); read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range); /* Take care to ignore link-once functions that were removed. In these cases, the function address will be NULL, but if the encoding is smaller than a pointer a true NULL may not be representable. Assume 0 in the representable bits is NULL. */ mask = size_of_encoded_value (encoding); if (mask < sizeof (void *)) mask = (((_Unwind_Ptr) 1) << (mask << 3)) - 1; else mask = -1; if ((pc_begin & mask) == 0) continue; } if ((_Unwind_Ptr) pc - pc_begin < pc_range) return this_fde; } return NULL; } /* Binary search for an FDE containing the given PC. Here are three implementations of increasing complexity. */ static inline const fde * binary_search_unencoded_fdes (struct object *ob, void *pc) { struct fde_vector *vec = ob->u.sort; size_t lo, hi; for (lo = 0, hi = vec->count; lo < hi; ) { size_t i = (lo + hi) / 2; const fde *const f = vec->array[i]; void *pc_begin; uaddr pc_range; memcpy (&pc_begin, (const void * const *) f->pc_begin, sizeof (void *)); memcpy (&pc_range, (const uaddr *) f->pc_begin + 1, sizeof (uaddr)); if (pc < pc_begin) hi = i; else if (pc >= pc_begin + pc_range) lo = i + 1; else return f; } return NULL; } static inline const fde * binary_search_single_encoding_fdes (struct object *ob, void *pc) { struct fde_vector *vec = ob->u.sort; int encoding = ob->s.b.encoding; _Unwind_Ptr base = base_from_object (encoding, ob); size_t lo, hi; for (lo = 0, hi = vec->count; lo < hi; ) { size_t i = (lo + hi) / 2; const fde *f = vec->array[i]; _Unwind_Ptr pc_begin, pc_range; const unsigned char *p; p = read_encoded_value_with_base (encoding, base, f->pc_begin, &pc_begin); read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range); if ((_Unwind_Ptr) pc < pc_begin) hi = i; else if ((_Unwind_Ptr) pc >= pc_begin + pc_range) lo = i + 1; else return f; } return NULL; } static inline const fde * binary_search_mixed_encoding_fdes (struct object *ob, void *pc) { struct fde_vector *vec = ob->u.sort; size_t lo, hi; for (lo = 0, hi = vec->count; lo < hi; ) { size_t i = (lo + hi) / 2; const fde *f = vec->array[i]; _Unwind_Ptr pc_begin, pc_range; const unsigned char *p; int encoding; encoding = get_fde_encoding (f); p = read_encoded_value_with_base (encoding, base_from_object (encoding, ob), f->pc_begin, &pc_begin); read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range); if ((_Unwind_Ptr) pc < pc_begin) hi = i; else if ((_Unwind_Ptr) pc >= pc_begin + pc_range) lo = i + 1; else return f; } return NULL; } static const fde * search_object (struct object* ob, void *pc) { /* The fast path initializes objects eagerly to avoid locking. * On the slow path we initialize them now */ #ifndef ATOMIC_FDE_FAST_PATH /* If the data hasn't been sorted, try to do this now. We may have more memory available than last time we tried. */ if (! ob->s.b.sorted) { init_object (ob); /* Despite the above comment, the normal reason to get here is that we've not processed this object before. A quick range check is in order. */ if (pc < ob->pc_begin) return NULL; } #endif if (ob->s.b.sorted) { if (ob->s.b.mixed_encoding) return binary_search_mixed_encoding_fdes (ob, pc); else if (ob->s.b.encoding == DW_EH_PE_absptr) return binary_search_unencoded_fdes (ob, pc); else return binary_search_single_encoding_fdes (ob, pc); } else { /* Long slow laborious linear search, cos we've no memory. */ if (ob->s.b.from_array) { fde **p; for (p = ob->u.array; *p ; p++) { const fde *f = linear_search_fdes (ob, *p, pc); if (f) return f; } return NULL; } else return linear_search_fdes (ob, ob->u.single, pc); } } #ifdef ATOMIC_FDE_FAST_PATH // Check if the object was already initialized static inline bool is_object_initialized (struct object *ob) { // We have to use acquire atomics for the read, which // is a bit involved as we read from a bitfield struct object tmp; __atomic_load (&(ob->s.b), &(tmp.s.b), __ATOMIC_ACQUIRE); return tmp.s.b.sorted; } #endif const fde * _Unwind_Find_FDE (void *pc, struct dwarf_eh_bases *bases) { struct object *ob; const fde *f = NULL; #ifdef ATOMIC_FDE_FAST_PATH ob = btree_lookup (®istered_frames, (uintptr_type) pc); if (!ob) return NULL; // Initialize the object lazily if (!is_object_initialized (ob)) { // Check again under mutex init_object_mutex_once (); __gthread_mutex_lock (&object_mutex); if (!ob->s.b.sorted) { init_object (ob); } __gthread_mutex_unlock (&object_mutex); } f = search_object (ob, pc); #else init_object_mutex_once (); __gthread_mutex_lock (&object_mutex); /* Linear search through the classified objects, to find the one containing the pc. Note that pc_begin is sorted descending, and we expect objects to be non-overlapping. */ for (ob = seen_objects; ob; ob = ob->next) if (pc >= ob->pc_begin) { f = search_object (ob, pc); if (f) goto fini; break; } /* Classify and search the objects we've not yet processed. */ while ((ob = unseen_objects)) { struct object **p; unseen_objects = ob->next; f = search_object (ob, pc); /* Insert the object into the classified list. */ for (p = &seen_objects; *p ; p = &(*p)->next) if ((*p)->pc_begin < ob->pc_begin) break; ob->next = *p; *p = ob; if (f) goto fini; } fini: __gthread_mutex_unlock (&object_mutex); #endif if (f) { int encoding; _Unwind_Ptr func; bases->tbase = ob->tbase; bases->dbase = ob->dbase; encoding = ob->s.b.encoding; if (ob->s.b.mixed_encoding) encoding = get_fde_encoding (f); read_encoded_value_with_base (encoding, base_from_object (encoding, ob), f->pc_begin, &func); bases->func = (void *) func; } return f; }