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98583463ab
Fuzzers stress the assembler in ways no sane programmer would ever do. One x86 oss-fuzz testcase (cleaned up a litte) was: .sect .debug_frame call x .long x,0 .space 1 .long 0,0 The call insn leaves the frag data corresponding to a CIE uninitialised until later in assembly, leading to reports of uninitialised data access in ehopt.c:check_eh_frame. Hack around this problem by noticing an insn has been assembled in dwarf2_emit_insn. The existing frag has_code can't be used as that leads to alignment complaints, so add a new segment_info flag. * subsegs.h (struct segment_info_struct): Move bss and hadone later. Rename hadone to stab_seen. Add insn_seen bitfield. * dwarf2dbg.c (dwarf2_emit_insn): Set insn_seen. * ehopt.c (check_eh_frame): Disable optimisation if insn_seen. * stabs.c (s_stab_generic): Adjust for hadone rename.
120 lines
4.0 KiB
C
120 lines
4.0 KiB
C
/* subsegs.h -> subsegs.c
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Copyright (C) 1987-2025 Free Software Foundation, Inc.
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This file is part of GAS, the GNU Assembler.
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GAS is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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GAS is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GAS; see the file COPYING. If not, write to the Free
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Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
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02110-1301, USA. */
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/*
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* For every sub-segment the user mentions in the ASsembler program,
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* we make one struct frchain. Each sub-segment has exactly one struct frchain
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* and vice versa.
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*
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* Struct frchain's are forward chained (in ascending order of sub-segment
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* code number). The chain runs through frch_next of each subsegment.
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* This makes it hard to find a subsegment's frags
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* if programmer uses a lot of them. Most programs only use text0 and
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* data0, so they don't suffer. At least this way:
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* (1) There are no "arbitrary" restrictions on how many subsegments
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* can be programmed;
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* (2) Subsegments' frchain-s are (later) chained together in the order in
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* which they are emitted for object file viz text then data.
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*
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* From each struct frchain dangles a chain of struct frags. The frags
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* represent code fragments, for that sub-segment, forward chained.
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*/
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#include "obstack.h"
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struct frch_cfi_data;
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struct frch_ginsn_data;
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struct frchain /* control building of a frag chain */
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{ /* FRCH = FRagment CHain control */
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struct frag *frch_root; /* 1st struct frag in chain, or NULL */
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struct frag *frch_last; /* last struct frag in chain, or NULL */
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struct frchain *frch_next; /* next in chain of struct frchain-s */
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subsegT frch_subseg; /* subsegment number of this chain */
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fixS *fix_root; /* Root of fixups for this subsegment. */
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fixS *fix_tail; /* Last fixup for this subsegment. */
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struct obstack frch_obstack; /* for objects in this frag chain */
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fragS *frch_frag_now; /* frag_now for this subsegment */
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struct frch_cfi_data *frch_cfi_data;
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struct frch_ginsn_data *frch_ginsn_data;
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};
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typedef struct frchain frchainS;
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/* Frchain we are assembling into now. That is, the current segment's
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frag chain, even if it contains no (complete) frags. */
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extern frchainS *frchain_now;
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typedef struct segment_info_struct
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{
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frchainS *frchainP;
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/* Fixups for this segment. This is only valid after the frchains
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are run together. */
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fixS *fix_root;
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fixS *fix_tail;
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/* NULL, or pointer to the gas symbol that is the section symbol for
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this section. */
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symbolS *sym;
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/* Used by dwarf2dbg.c for this section's line table entries. */
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void *dwarf2_line_seg;
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/* This field is set if this is a .bss section which does not really
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have any contents. Once upon a time a .bss section did not have
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any frags, but that is no longer true. This field prevent the
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SEC_HAS_CONTENTS flag from being set for the section even if
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there are frags. */
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unsigned int bss : 1;
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/* Set whenever dwarf2_emit_insn is called, and used to disable
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.eh_frame and .debug_frame optimisation. This is an anti-fuzzer
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measure. */
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unsigned int insn_seen : 1;
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/* Used by the stabs code. */
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unsigned int stab_seen : 1;
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union
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{
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/* Current size of section holding stabs strings. */
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unsigned long stab_string_size;
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/* Initial frag for ELF. */
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char *p;
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} stabu;
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#ifdef NEED_LITERAL_POOL
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unsigned long literal_pool_size;
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#endif
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#ifdef TC_SEGMENT_INFO_TYPE
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TC_SEGMENT_INFO_TYPE tc_segment_info_data;
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#endif
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} segment_info_type;
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#define seg_info(sec) \
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((segment_info_type *) bfd_section_userdata (sec))
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extern symbolS *section_symbol (segT);
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extern void subsegs_print_statistics (FILE *);
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