/* SPDX-License-Identifier: GPL-2.0-only Copyright (C) 2006 Mandriva Conectiva S.A. Copyright (C) 2006 Arnaldo Carvalho de Melo Copyright (C) 2007 Red Hat Inc. Copyright (C) 2007 Arnaldo Carvalho de Melo */ #include "list.h" #include "dwarves_reorganize.h" #include "dwarves.h" static void class__recalc_holes(struct class *class) { class->holes_searched = 0; class__find_holes(class); } void class__subtract_offsets_from(struct class *class, struct class_member *from, const uint16_t size) { struct class_member *member = list_prepare_entry(from, class__tags(class), tag.node); list_for_each_entry_continue(member, class__tags(class), tag.node) if (member->tag.tag == DW_TAG_member) { member->byte_offset -= size; member->bit_offset -= size * 8; } if (class->padding != 0) { struct class_member *last_member = type__last_member(&class->type); const ssize_t new_padding = (class__size(class) - (last_member->byte_offset + last_member->byte_size)); if (new_padding > 0) class->padding = new_padding; else class->padding = 0; } } void class__add_offsets_from(struct class *class, struct class_member *from, const uint16_t size) { struct class_member *member = list_prepare_entry(from, class__tags(class), tag.node); list_for_each_entry_continue(member, class__tags(class), tag.node) if (member->tag.tag == DW_TAG_member) { member->byte_offset += size; member->bit_offset += size * 8; } } /* * XXX: Check this more thoroughly. Right now it is used because I was * to lazy to do class__remove_member properly, adjusting alignments and * holes as we go removing fields. Ditto for class__add_offsets_from. */ void class__fixup_alignment(struct class *class, const struct cu *cu) { struct class_member *pos, *last_member = NULL; size_t power2; type__for_each_data_member(&class->type, pos) { if (last_member == NULL && pos->byte_offset != 0) { /* paranoid! */ class__subtract_offsets_from(class, pos, (pos->byte_offset - pos->byte_size)); pos->byte_offset = 0; pos->bit_offset = 0; } else if (last_member != NULL && last_member->hole >= cu->addr_size) { size_t dec = (last_member->hole / cu->addr_size) * cu->addr_size; last_member->hole -= dec; if (last_member->hole == 0) --class->nr_holes; pos->byte_offset -= dec; pos->bit_offset -= dec * 8; class->type.size -= dec; class__subtract_offsets_from(class, pos, dec); } else for (power2 = cu->addr_size; power2 >= 2; power2 /= 2) { const size_t remainder = pos->byte_offset % power2; if (pos->byte_size == power2) { if (remainder == 0) /* perfectly aligned */ break; if (last_member->hole >= remainder) { last_member->hole -= remainder; if (last_member->hole == 0) --class->nr_holes; pos->byte_offset -= remainder; pos->bit_offset -= remainder * 8; class__subtract_offsets_from(class, pos, remainder); } else { const size_t inc = power2 - remainder; if (last_member->hole == 0) ++class->nr_holes; last_member->hole += inc; pos->byte_offset += inc; pos->bit_offset += inc * 8; class->type.size += inc; class__add_offsets_from(class, pos, inc); } } } last_member = pos; } if (last_member != NULL) { struct class_member *m = type__find_first_biggest_size_base_type_member(&class->type, cu); size_t unpadded_size = last_member->byte_offset + last_member->byte_size; size_t m_size = m->byte_size, remainder; /* google for struct zone_padding in the linux kernel for an example */ if (m_size == 0) return; remainder = unpadded_size % m_size; if (remainder != 0) { class->padding = m_size - remainder; class->type.size = unpadded_size + class->padding; } } } static struct class_member * class__find_next_hole_of_size(struct class *class, struct class_member *from, size_t size) { struct class_member *member = list_prepare_entry(from, class__tags(class), tag.node); struct class_member *bitfield_head = NULL; list_for_each_entry_continue(member, class__tags(class), tag.node) { if (member->tag.tag != DW_TAG_member) continue; if (member->bitfield_size != 0) { if (bitfield_head == NULL) bitfield_head = member; } else bitfield_head = NULL; if (member->hole != 0) { if (member->byte_size != 0 && member->byte_size <= size) return bitfield_head ? : member; } } return NULL; } static struct class_member * class__find_last_member_of_size(struct class *class, struct class_member *to, size_t size) { struct class_member *member; list_for_each_entry_reverse(member, class__tags(class), tag.node) { if (member->tag.tag != DW_TAG_member) continue; if (member == to) break; /* * Check if this is the first member of a bitfield. It either * has another member before it that is not part of the current * bitfield or it is the first member of the struct. */ if (member->bitfield_size != 0 && member->byte_offset != 0) { struct class_member *prev = list_entry(member->tag.node.prev, struct class_member, tag.node); if (prev->bitfield_size != 0) continue; } if (member->byte_size != 0 && member->byte_size <= size) return member; } return NULL; } static struct class_member * class__find_next_bit_hole_of_size(struct class *class, struct class_member *from, size_t size) { struct class_member *member = list_prepare_entry(from, class__tags(class), tag.node); list_for_each_entry_continue(member, class__tags(class), tag.node) { if (member->tag.tag != DW_TAG_member) continue; if (member->bit_hole != 0 && member->bitfield_size <= size) return member; } #if 0 /* * FIXME: Handle the case where the bit padding is on the same bitfield * that we're looking, i.e. we can't combine a bitfield with itclass, * perhaps we should tag bitfields with a sequential, clearly marking * each of the bitfields in advance, so that all the algoriths that * have to deal with bitfields, moving them around, demoting, etc, can * be simplified. */ /* * Now look if the last member is a one member bitfield, * i.e. if we have bit_padding */ if (class->bit_padding != 0) return type__last_member(&class->type); #endif return NULL; } static bool class__move_member(struct class *class, struct class_member *dest, struct class_member *from, const struct cu *cu, int from_padding, const int verbose, FILE *fp) { const size_t from_size = from->byte_size; const size_t dest_size = dest->byte_size; #ifndef BITFIELD_REORG_ALGORITHMS_ENABLED /* * For now refuse to move a bitfield, we need to first fixup some BRAIN FARTs */ if (from->bitfield_size != 0) return false; #endif const bool from_was_last = from->tag.node.next == class__tags(class); struct class_member *tail_from = from; struct class_member *from_prev = list_entry(from->tag.node.prev, struct class_member, tag.node); uint16_t orig_tail_from_hole = tail_from->hole; const uint16_t orig_from_offset = from->byte_offset; /* * Align 'from' after 'dest': */ const uint16_t offset = dest->hole % (from_size > cu->addr_size ? cu->addr_size : from_size); /* * Set new 'from' offset, after 'dest->byte_offset', aligned */ const uint16_t new_from_offset = dest->byte_offset + dest_size + offset; if (verbose) fputs("/* Moving", fp); if (from->bitfield_size != 0) { struct class_member *pos = list_prepare_entry(from, class__tags(class), tag.node); struct class_member *tmp; LIST_HEAD(from_list); if (verbose) fprintf(fp, " bitfield('%s' ... ", class_member__name(from, cu)); list_for_each_entry_safe_from(pos, tmp, class__tags(class), tag.node) { if (pos->tag.tag != DW_TAG_member) continue; /* * Have we reached the end of the bitfield? */ if (pos->byte_offset != orig_from_offset) break; tail_from = pos; orig_tail_from_hole = tail_from->hole; pos->byte_offset = new_from_offset; pos->bit_offset = new_from_offset * 8 + pos->bitfield_offset; list_move_tail(&pos->tag.node, &from_list); } list_splice(&from_list, &dest->tag.node); if (verbose) fprintf(fp, "'%s')", class_member__name(tail_from, cu)); } else { if (verbose) fprintf(fp, " '%s'", class_member__name(from, cu)); /* * Remove 'from' from the list */ list_del(&from->tag.node); /* * Add 'from' after 'dest': */ __list_add(&from->tag.node, &dest->tag.node, dest->tag.node.next); from->byte_offset = new_from_offset; from->bit_offset = new_from_offset * 8 + from->bitfield_offset; } if (verbose) fprintf(fp, " from after '%s' to after '%s' */\n", class_member__name(from_prev, cu), class_member__name(dest, cu)); if (from_padding) { /* * Check if we're eliminating the need for padding: */ if (orig_from_offset % cu->addr_size == 0) { /* * Good, no need for padding anymore: */ class->type.size -= from_size + class->padding; } else { /* * No, so just add from_size to the padding: */ if (verbose) fprintf(fp, "/* adding %zd bytes from %s to " "the padding */\n", from_size, class_member__name(from, cu)); } } else if (from_was_last) { class->type.size -= from_size + class->padding; } else { /* * See if we are adding a new hole that is bigger than * sizeof(long), this may have problems with explicit alignment * made by the programmer, perhaps we need A switch that allows * us to avoid realignment, just using existing holes but * keeping the existing alignment, anyway the programmer has to * check the resulting rerganization before using it, and for * automatic stuff such as the one that will be used for struct * "views" in tools such as ctracer we are more interested in * packing the subset as tightly as possible. */ if (orig_tail_from_hole + from_size >= cu->addr_size) { class->type.size -= cu->addr_size; class__subtract_offsets_from(class, from_prev, cu->addr_size); } } class__recalc_holes(class); if (verbose > 1) { class__fprintf(class, cu, fp); fputc('\n', fp); } return true; } static void class__move_bit_member(struct class *class, const struct cu *cu, struct class_member *dest, struct class_member *from, const int verbose, FILE *fp) { struct class_member *from_prev = list_entry(from->tag.node.prev, struct class_member, tag.node); const uint8_t is_last_member = (from->tag.node.next == class__tags(class)); if (verbose) fprintf(fp, "/* Moving '%s:%u' from after '%s' to " "after '%s:%u' */\n", class_member__name(from, cu), from->bitfield_size, class_member__name(from_prev, cu), class_member__name(dest, cu), dest->bitfield_size); /* * Remove 'from' from the list */ list_del(&from->tag.node); /* * Add from after dest: */ __list_add(&from->tag.node, &dest->tag.node, dest->tag.node.next); /* Check if this was the last entry in the bitfield */ if (from_prev->bitfield_size == 0) { size_t from_size = from->byte_size; /* * Are we shrinking the struct? */ if (from_size + from->hole >= cu->addr_size) { class->type.size -= from_size + from->hole; class__subtract_offsets_from(class, from_prev, from_size + from->hole); } } /* * Tricky, what are the rules for bitfield layouts on this arch? * Assume its IA32 */ from->bitfield_offset = dest->bitfield_offset + dest->bitfield_size; /* * Now both have the same offset: */ from->byte_offset = dest->byte_offset; from->bit_offset = dest->byte_offset * 8 + from->bitfield_offset; class__recalc_holes(class); if (verbose > 1) { class__fprintf(class, cu, fp); fputc('\n', fp); } } static void class__demote_bitfield_members(struct class *class, struct class_member *from, struct class_member *to, const struct base_type *old_type, const struct base_type *new_type, type_id_t new_type_id) { struct class_member *member = list_prepare_entry(from, class__tags(class), tag.node); list_for_each_entry_from(member, class__tags(class), tag.node) { if (member->tag.tag != DW_TAG_member) continue; member->byte_size = new_type->bit_size / 8; member->tag.type = new_type_id; if (member == to) break; } } static struct tag *cu__find_base_type_of_size(const struct cu *cu, const size_t size, type_id_t *id) { const char *type_name, *type_name_alt = NULL; switch (size) { case sizeof(unsigned char): type_name = "unsigned char"; break; case sizeof(unsigned short int): type_name = "short unsigned int"; type_name_alt = "unsigned short"; break; case sizeof(unsigned int): type_name = "unsigned int"; type_name_alt = "unsigned"; break; case sizeof(unsigned long long): if (cu->addr_size == 8) { type_name = "long unsigned int"; type_name_alt = "unsigned long"; } else { type_name = "long long unsigned int"; type_name_alt = "unsigned long long"; } break; default: return NULL; } struct tag *ret = cu__find_base_type_by_name(cu, type_name, id); return ret ?: cu__find_base_type_by_name(cu, type_name_alt, id); } static int class__demote_bitfields(struct class *class, const struct cu *cu, const int verbose, FILE *fp) { struct class_member *member; struct class_member *bitfield_head = NULL; const struct tag *old_type_tag, *new_type_tag; size_t current_bitfield_size = 0, size, bytes_needed; int some_was_demoted = 0; type__for_each_data_member(&class->type, member) { /* * Check if we are moving away from a bitfield */ if (member->bitfield_size == 0) { current_bitfield_size = 0; bitfield_head = NULL; } else { if (bitfield_head == NULL) { bitfield_head = member; current_bitfield_size = member->bitfield_size; } else if (bitfield_head->byte_offset != member->byte_offset) { /* * We moved from one bitfield to another, for * now don't handle this case, just move on to * the next bitfield, we may well move it to * another place and then the first bitfield will * be isolated and will be handled in the next * pass. */ bitfield_head = member; current_bitfield_size = member->bitfield_size; } else current_bitfield_size += member->bitfield_size; } /* * Have we got to the end of a bitfield with holes? */ if (member->bit_hole == 0) continue; size = member->byte_size; bytes_needed = (current_bitfield_size + 7) / 8; bytes_needed = roundup_pow_of_two(bytes_needed); if (bytes_needed == size) continue; type_id_t new_type_id; old_type_tag = cu__type(cu, member->tag.type); new_type_tag = cu__find_base_type_of_size(cu, bytes_needed, &new_type_id); if (new_type_tag == NULL) { fprintf(fp, "/* BRAIN FART ALERT! couldn't find a " "%zd bytes base type */\n\n", bytes_needed); continue; } if (verbose) { char old_bf[64], new_bf[64]; fprintf(fp, "/* Demoting bitfield ('%s' ... '%s') " "from '%s' to '%s' */\n", class_member__name(bitfield_head, cu), class_member__name(member, cu), base_type__name(tag__base_type(old_type_tag), cu, old_bf, sizeof(old_bf)), base_type__name(tag__base_type(new_type_tag), cu, new_bf, sizeof(new_bf))); } class__demote_bitfield_members(class, bitfield_head, member, tag__base_type(old_type_tag), tag__base_type(new_type_tag), new_type_id); class__recalc_holes(class); some_was_demoted = 1; if (verbose > 1) { class__fprintf(class, cu, fp); fputc('\n', fp); } } /* * Now look if we have bit padding, i.e. if the the last member * is a bitfield and its the sole member in this bitfield, i.e. * if it wasn't already demoted as part of a bitfield of more than * one member: */ member = type__last_member(&class->type); if (class->bit_padding != 0 && bitfield_head == member) { size = member->byte_size; bytes_needed = (member->bitfield_size + 7) / 8; if (bytes_needed < size) { old_type_tag = cu__type(cu, member->tag.type); type_id_t new_type_id; new_type_tag = cu__find_base_type_of_size(cu, bytes_needed, &new_type_id); tag__assert_search_result(old_type_tag); tag__assert_search_result(new_type_tag); if (verbose) { char old_bf[64], new_bf[64]; fprintf(fp, "/* Demoting bitfield ('%s') " "from '%s' to '%s' */\n", class_member__name(member, cu), base_type__name(tag__base_type(old_type_tag), cu, old_bf, sizeof(old_bf)), base_type__name(tag__base_type(new_type_tag), cu, new_bf, sizeof(new_bf))); } class__demote_bitfield_members(class, member, member, tag__base_type(old_type_tag), tag__base_type(new_type_tag), new_type_id); class__recalc_holes(class); some_was_demoted = 1; if (verbose > 1) { class__fprintf(class, cu, fp); fputc('\n', fp); } } } return some_was_demoted; } static void class__reorganize_bitfields(struct class *class, const struct cu *cu, const int verbose, FILE *fp) { struct class_member *member, *brother; restart: type__for_each_data_member(&class->type, member) { /* See if we have a hole after this member */ if (member->bit_hole != 0) { /* * OK, try to find a member that has a bit hole after * it and that has a size that fits the current hole: */ brother = class__find_next_bit_hole_of_size(class, member, member->bit_hole); if (brother != NULL) { class__move_bit_member(class, cu, member, brother, verbose, fp); goto restart; } } } } static void class__fixup_bitfield_types(struct class *class, struct class_member *from, struct class_member *to_before, type_id_t type) { struct class_member *member = list_prepare_entry(from, class__tags(class), tag.node); list_for_each_entry_from(member, class__tags(class), tag.node) { if (member->tag.tag != DW_TAG_member) continue; if (member == to_before) break; member->tag.type = type; } } /* * Think about this pahole output a bit: * * [filo examples]$ pahole swiss_cheese cheese * / * <11b> /home/acme/git/pahole/examples/swiss_cheese.c:3 * / * struct cheese { * * int bitfield1:1; / * 64 4 * / * int bitfield2:1; / * 64 4 * / * * / * XXX 14 bits hole, try to pack * / * / * Bitfield WARNING: DWARF size=4, real size=2 * / * * short int d; / * 66 2 * / * * * The compiler (gcc 4.1.1 20070105 (Red Hat 4.1.1-51) in the above example), * Decided to combine what was declared as an int (4 bytes) bitfield but doesn't * uses even one byte with the next field, that is a short int (2 bytes), * without demoting the type of the bitfield to short int (2 bytes), so in terms * of alignment the real size is 2, not 4, to make things easier for the rest of * the reorganizing routines we just do the demotion ourselves, fixing up the * sizes. */ static void class__fixup_member_types(struct class *class, const struct cu *cu, const uint8_t verbose, FILE *fp) { struct class_member *pos, *bitfield_head = NULL; uint8_t fixup_was_done = 0; type__for_each_data_member(&class->type, pos) { /* * Is this bitfield member? */ if (pos->bitfield_size != 0) { /* * The first entry in a bitfield? */ if (bitfield_head == NULL) bitfield_head = pos; continue; } /* * OK, not a bitfield member, but have we just passed * by a bitfield? */ if (bitfield_head != NULL) { const uint16_t real_size = (pos->byte_offset - bitfield_head->byte_offset); const size_t size = bitfield_head->byte_size; /* * Another case: struct irq_cfg { struct irq_pin_list * irq_2_pin; / * 0 8 * / cpumask_var_t domain; / * 8 16 * / cpumask_var_t old_domain; / * 24 16 * / u8 vector; / * 40 1 * / u8 move_in_progress:1; / * 41: 7 1 * / u8 remapped:1; / * 41: 6 1 * / / * XXX 6 bits hole, try to pack * / / * XXX 6 bytes hole, try to pack * / union { struct irq_2_iommu irq_2_iommu; / * 16 * / struct irq_2_irte irq_2_irte; / * 4 * / }; / * 48 16 * / / * --- cacheline 1 boundary (64 bytes) --- * / * So just fix it up if the byte_size of the bitfield is * greater than what it really uses. */ if (real_size < size) { type_id_t new_type_id; struct tag *new_type_tag = cu__find_base_type_of_size(cu, real_size, &new_type_id); if (new_type_tag == NULL) { fprintf(stderr, "%s: couldn't find" " a base_type of %d bytes!\n", __func__, real_size); continue; } class__fixup_bitfield_types(class, bitfield_head, pos, new_type_id); fixup_was_done = 1; } } bitfield_head = NULL; } if (fixup_was_done) { class__recalc_holes(class); } if (verbose && fixup_was_done) { fprintf(fp, "/* bitfield types were fixed */\n"); if (verbose > 1) { class__fprintf(class, cu, fp); fputc('\n', fp); } } } void class__reorganize(struct class *class, const struct cu *cu, const int verbose, FILE *fp) { struct class_member *member, *brother, *last_member; size_t alignment_size; class__find_holes(class); #ifdef BITFIELD_REORG_ALGORITHMS_ENABLED class__fixup_member_types(class, cu, verbose, fp); while (class__demote_bitfields(class, cu, verbose, fp)) class__reorganize_bitfields(class, cu, verbose, fp); #endif /* Now try to combine holes */ restart: alignment_size = 0; /* * It can be NULL if this class doesn't have any data members, * just inheritance entries */ last_member = type__last_member(&class->type); if (last_member == NULL) return; type__for_each_data_member(&class->type, member) { const size_t aligned_size = member->byte_size + member->hole; if (aligned_size <= cu->addr_size && aligned_size > alignment_size) alignment_size = aligned_size; } if (alignment_size != 0) { size_t modulo; uint16_t new_padding; if (alignment_size > 1) alignment_size = roundup(alignment_size, 2); modulo = (last_member->byte_offset + last_member->byte_size) % alignment_size; if (modulo != 0) new_padding = cu->addr_size - modulo; else new_padding = 0; if (new_padding != class->padding) { class->padding = new_padding; class->type.size = (last_member->byte_offset + last_member->byte_size + new_padding); } } type__for_each_data_member(&class->type, member) { /* See if we have a hole after this member */ if (member->hole != 0) { /* * OK, try to find a member that has a hole after it * and that has a size that fits the current hole: */ brother = class__find_next_hole_of_size(class, member, member->hole); if (brother != NULL) { struct class_member *brother_prev = list_entry(brother->tag.node.prev, struct class_member, tag.node); /* * If it the next member, avoid moving it closer, * it could be a explicit alignment rule, like * ____cacheline_aligned_in_smp in the Linux * kernel. */ if (brother_prev != member) { if (class__move_member(class, member, brother, cu, 0, verbose, fp)) goto restart; } } /* * OK, but is there padding? If so the last member * has a hole, if we are not at the last member and * it has a size that is smaller than the current hole * we can move it after the current member, reducing * the padding or eliminating it altogether. */ if (class->padding > 0 && member != last_member && last_member->byte_size != 0 && last_member->byte_size <= member->hole) { if (class__move_member(class, member, last_member, cu, 1, verbose, fp)) goto restart; } } } /* Now try to move members at the tail to after holes */ if (class->nr_holes == 0) return; type__for_each_data_member(&class->type, member) { /* See if we have a hole after this member */ if (member->hole != 0) { brother = class__find_last_member_of_size(class, member, member->hole); if (brother != NULL) { struct class_member *brother_prev = list_entry(brother->tag.node.prev, struct class_member, tag.node); /* * If it the next member, avoid moving it closer, * it could be a explicit alignment rule, like * ____cacheline_aligned_in_smp in the Linux * kernel. */ if (brother_prev != member) { if (class__move_member(class, member, brother, cu, 0, verbose, fp)) goto restart; } } } } }