binutils-gdb/ld/ldemul.h
Nick Alcock 1ff6de0312 bfd, ld: add CTF section linking
This is quite complicated because the CTF section's contents depend on
the final contents of the symtab and strtab, because it has two sections
whose contents are shuffled to be in 1:1 correspondence with the symtab,
and an internal strtab that gets deduplicated against the ELF strtab
(with offsets adjusted to point into the ELF strtab instead).  It is
also compressed if large enough, so its size depends on its contents!

So we cannot construct it as early as most sections: we cannot even
*begin* construction until after the symtab and strtab are finalized.
Thankfully there is already one section treated similarly: compressed
debugging sections: the only differences are that compressed debugging
sections have extra handling to deal with their changing name if
compressed (CTF sections are always called ".ctf" for now, though we
have reserved ".ctf.*" against future use), and that compressed
debugging sections have previously-uncompressed content which has to be
stashed away for later compression, while CTF sections have no content
at all until we generate it (very late).

BFD also cannot do the link itself: libctf knows how to do it, and BFD
cannot call libctf directly because libctf already depends on bfd for
file I/O.  So we have to use a pair of callbacks, one, examine_strtab,
which allows a caller to examine the symtab and strtab after
finalization (called from elf_link_swap_symbols_out(), right before the
symtabs are written, and after the strtab has been finalized), and one
which actually does the emission (called emit_ctf simply because it is
grouped with a bunch of section-specific late-emission function calls at
the bottom of bfd_elf_final_link, and a section-specific name seems best
for that).  emit_ctf is actually called *twice*: once from lang_process
if the emulation suggests that this bfd target does not examine the
symtab or strtab, and once via a bfd callback if it does.  (This means
that non-ELF targets still get CTF emitted, even though the late CTF
emission stage is never called for them).

v2: merged with non-ELF support patch: slight commit message
    adjustments.
v3: do not spend time merging CTF, or crash, if the CTF section is
    explicitly discarded.  Do not try to merge or compress CTF unless
    linking.
v4: add CTF_COMPRESSION_THRESHOLD.  Annul the freed input ctf_file_t's
    after writeout: set SEC_IN_MEMORY on the output contents so a future
    bfd enhancement knows it could free it.  Add SEC_LINKER_CREATED |
    SEC_KEEP to avoid having to add .ctf to the linker script.  Drop
    now-unnecessary ldlang.h-level elf-bfd.h include and hackery around
    it.  Adapt to elf32.em->elf.em and elf-generic.em->ldelf*.c
    changes.
v5: fix tabdamage.  Drop #inclusions in .h files: include in .c files,
    .em files, and use struct forwards instead.  Use bfd_section_is_ctf
    inline function rather than SECTION_IS_CTF macro.  Move a few
    comments.

	* Makefile.def (dependencies): all-ld depends on all-libctf.
	* Makefile.in: Regenerated.

include/
	* bfdlink.h (elf_strtab_hash): New forward.
	(elf_sym_strtab): Likewise.
	(struct bfd_link_callbacks <examine_strtab>): New.
	(struct bfd_link_callbacks <emit_ctf>): Likewise.

bfd/
	* elf-bfd.h (bfd_section_is_ctf): New inline function.
	* elf.c (special_sections_c): Add ".ctf".
	(assign_file_positions_for_non_load_sections): Note that
	compressed debugging sections etc are not assigned here.  Treat
	CTF sections like SEC_ELF_COMPRESS sections when is_linker_output:
	sh_offset -1.
	(assign_file_positions_except_relocs): Likewise.
	(find_section_in_list): Note that debugging and CTF sections, as
	well as reloc sections, are assigned later.
	(_bfd_elf_assign_file_positions_for_non_load): CTF sections get
	their size and contents updated.
	(_bfd_elf_set_section_contents): Skip CTF sections: unlike
	compressed sections, they have no uncompressed content to copy at
	this stage.
	* elflink.c (elf_link_swap_symbols_out): Call the examine_strtab
	callback right before the strtab is written out.
	(bfd_elf_final_link): Don't cache the section contents of CTF
	sections: they are not populated yet.  Call the emit_ctf callback
	right at the end, after all the symbols and strings are flushed
	out.

ld/
	* ldlang.h: (struct lang_input_statement_struct): Add the_ctf.
	(struct elf_sym_strtab): Add forward.
	(struct elf_strtab_hash): Likewise.
	(ldlang_ctf_apply_strsym): Declare.
	(ldlang_write_ctf_late): Likewise.
	* ldemul.h (ldemul_emit_ctf_early): New.
	(ldemul_examine_strtab_for_ctf): Likewise.
	(ld_emulation_xfer_type) <emit_ctf_early>: Likewise.
	(ld_emulation_xfer_type) <examine_strtab_for_ctf>: Likewise.
	* ldemul.c (ldemul_emit_ctf_early): New.
	(ldemul_examine_strtab_for_ctf): Likewise.
	* ldlang.c: Include ctf-api.h.
	(CTF_COMPRESSION_THRESHOLD): New.
	(ctf_output): New. Initialized in...
	(ldlang_open_ctf): ... this new function.  Open all the CTF
	sections in the input files: mark them non-loaded and empty
	so as not to copy their contents to the output, but linker-created
	so the section gets created in the target.
	(ldlang_merge_ctf): New, merge types via ctf_link_add_ctf and
	ctf_link.
	(ldlang_ctf_apply_strsym): New, an examine_strtab callback: wrap
	ldemul_examine_strtab_for_ctf.
	(lang_write_ctf): New, write out the CTF section.
	(ldlang_write_ctf_late): New, late call via bfd's emit_ctf hook.
	(lang_process): Call ldlang_open_ctf, ldlang_merge_ctf, and
	lang_write_ctf.
	* ldmain.c (link_callbacks): Add ldlang_ctf_apply_strsym,
	ldlang_write_ctf_late.
	* emultempl/aix.em: Add ctf-api.h.
	* emultempl/armcoff.em: Likewise.
	* emultempl/beos.em: Likewise.
	* emultempl/elf.em: Likewise.
	* emultempl/generic.em: Likewise.
	* emultempl/linux.em: Likewise.
	* emultempl/msp430.em: Likewise.
	* emultempl/pe.em: Likewise.
	* emultempl/pep.em: Likewise.
	* emultempl/ticoff.em: Likewise.
	* emultempl/vanilla.em: Likewise.
	* ldcref.c: Likewise.
	* ldctor.c: Likewise.
	* ldelf.c: Likewise.
	* ldelfgen.c: Likewise.
	* ldemul.c: Likewise.
	* ldexp.c: Likewise.
	* ldfile.c: Likewise.
	* ldgram.c: Likewise.
	* ldlex.l: Likewise.
	* ldmain.c: Likewise.
	* ldmisc.c: Likewise.
	* ldver.c: Likewise.
	* ldwrite.c: Likewise.
	* lexsup.c: Likewise.
	* mri.c: Likewise.
	* pe-dll.c: Likewise.
	* plugin.c: Likewise.

	* ldelfgen.c (ldelf_emit_ctf_early): New.
	(ldelf_examine_strtab_for_ctf): tell libctf about the symtab and
	strtab.
	(struct ctf_strsym_iter_cb_arg): New, state to do so.
	(ldelf_ctf_strtab_iter_cb): New: tell libctf about
	each string in the strtab in turn.
	(ldelf_ctf_symbols_iter_cb): New, tell libctf
	about each symbol in the symtab in turn.
	* ldelfgen.h (struct elf_sym_strtab): Add forward.
	(struct elf_strtab_hash): Likewise.
	(struct ctf_file): Likewise.
	(ldelf_emit_ctf_early): Declare.
	(ldelf_examine_strtab_for_ctf): Likewise.
	* emultempl/elf-generic.em (LDEMUL_EMIT_CTF_EARLY): Set it.
	(LDEMUL_EXAMINE_STRTAB_FOR_CTF): Likewise.
	* emultempl/aix.em (ld_${EMULATION_NAME}_emulation): Add
	emit_ctf_early and examine_strtab_for_ctf, NULL by default.
	* emultempl/armcoff.em (ld_${EMULATION_NAME}_emulation): Likewise.
	* emultempl/beos.em (ld_${EMULATION_NAME}_emulation): Likewise.
	* emultempl/elf.em (ld_${EMULATION_NAME}_emulation): Likewise.
	* emultempl/generic.em (ld_${EMULATION_NAME}_emulation): Likewise.
	* emultempl/linux.em (ld_${EMULATION_NAME}_emulation): Likewise.
	* emultempl/msp430.em (ld_${EMULATION_NAME}_emulation): Likewise.
	* emultempl/pe.em (ld_${EMULATION_NAME}_emulation): Likewise.
	* emultempl/pep.em (ld_${EMULATION_NAME}_emulation): Likewise.
	* emultempl/ticoff.em (ld_${EMULATION_NAME}_emulation): Likewise.
	* emultempl/vanilla.em (ld_vanilla_emulation): Likewise.

	* Makefile.am: Pull in libctf (and zlib, a transitive requirement
	for compressed CTF section emission).  Pass it on to DejaGNU.
	* configure.ac: Add AM_ZLIB.
	* aclocal.m4: Added zlib.m4.
	* Makefile.in: Regenerated.
	* testsuite/ld-bootstrap/bootstrap.exp: Use it when relinking ld.
2019-10-03 17:04:56 +01:00

243 lines
8.2 KiB
C

/* ld-emul.h - Linker emulation header file
Copyright (C) 1991-2019 Free Software Foundation, Inc.
This file is part of the GNU Binutils.
This program 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 of the License, or
(at your option) any later version.
This program 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.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
MA 02110-1301, USA. */
#ifndef LDEMUL_H
#define LDEMUL_H
/* Forward declaration for ldemul_add_options() and others. */
struct option;
extern void ldemul_hll
(char *);
extern void ldemul_syslib
(char *);
extern void ldemul_after_parse
(void);
extern void ldemul_before_parse
(void);
extern void ldemul_after_open
(void);
extern void ldemul_after_check_relocs
(void);
extern void ldemul_after_allocation
(void);
extern void ldemul_before_allocation
(void);
extern void ldemul_set_output_arch
(void);
extern char *ldemul_choose_target
(int, char**);
extern void ldemul_choose_mode
(char *);
extern void ldemul_list_emulations
(FILE *);
extern void ldemul_list_emulation_options
(FILE *);
extern char *ldemul_get_script
(int *isfile);
extern void ldemul_finish
(void);
extern void ldemul_set_symbols
(void);
extern void ldemul_create_output_section_statements
(void);
extern lang_output_section_statement_type *ldemul_place_orphan
(asection *, const char *, int);
extern bfd_boolean ldemul_parse_args
(int, char **);
extern void ldemul_add_options
(int, char **, int, struct option **, int, struct option **);
extern bfd_boolean ldemul_handle_option
(int);
extern bfd_boolean ldemul_unrecognized_file
(struct lang_input_statement_struct *);
extern bfd_boolean ldemul_recognized_file
(struct lang_input_statement_struct *);
extern bfd_boolean ldemul_open_dynamic_archive
(const char *, struct search_dirs *, struct lang_input_statement_struct *);
extern char *ldemul_default_target
(int, char**);
extern void after_parse_default
(void);
extern void after_open_default
(void);
extern void after_check_relocs_default
(void);
extern void after_allocation_default
(void);
extern void before_allocation_default
(void);
extern void finish_default
(void);
extern void finish_default
(void);
extern void set_output_arch_default
(void);
extern void syslib_default
(char*);
extern void hll_default
(char*);
extern int ldemul_find_potential_libraries
(char *, struct lang_input_statement_struct *);
extern struct bfd_elf_version_expr *ldemul_new_vers_pattern
(struct bfd_elf_version_expr *);
extern void ldemul_extra_map_file_text
(bfd *, struct bfd_link_info *, FILE *);
/* Return 1 if we are emitting CTF early, and 0 if ldemul_examine_strtab_for_ctf
will be called by the target. */
extern int ldemul_emit_ctf_early
(void);
/* Called from per-target code to examine the strtab and symtab. */
extern void ldemul_examine_strtab_for_ctf
(struct ctf_file *, struct elf_sym_strtab *, bfd_size_type,
struct elf_strtab_hash *);
typedef struct ld_emulation_xfer_struct {
/* Run before parsing the command line and script file.
Set the architecture, maybe other things. */
void (*before_parse) (void);
/* Handle the SYSLIB (low level library) script command. */
void (*syslib) (char *);
/* Handle the HLL (high level library) script command. */
void (*hll) (char *);
/* Run after parsing the command line and script file. */
void (*after_parse) (void);
/* Run after opening all input files, and loading the symbols. */
void (*after_open) (void);
/* Run after checking relocations. */
void (*after_check_relocs) (void);
/* Run after allocating output sections. */
void (*after_allocation) (void);
/* Set the output architecture and machine if possible. */
void (*set_output_arch) (void);
/* Decide which target name to use. */
char * (*choose_target) (int, char**);
/* Run before allocating output sections. */
void (*before_allocation) (void);
/* Return the appropriate linker script. */
char * (*get_script) (int *isfile);
/* The name of this emulation. */
char *emulation_name;
/* The output format. */
char *target_name;
/* Run after assigning values from the script. */
void (*finish) (void);
/* Create any output sections needed by the target. */
void (*create_output_section_statements) (void);
/* Try to open a dynamic library. ARCH is an architecture name, and
is normally the empty string. ENTRY is the lang_input_statement
that should be opened. */
bfd_boolean (*open_dynamic_archive)
(const char *arch, struct search_dirs *,
struct lang_input_statement_struct *entry);
/* Place an orphan section. Return TRUE if it was placed, FALSE if
the default action should be taken. This field may be NULL, in
which case the default action will always be taken. */
lang_output_section_statement_type *(*place_orphan)
(asection *, const char *, int);
/* Run after assigning parsing with the args, but before
reading the script. Used to initialize symbols used in the script. */
void (*set_symbols) (void);
/* Parse args which the base linker doesn't understand.
Return TRUE if the arg needs no further processing. */
bfd_boolean (*parse_args) (int, char **);
/* Hook to add options to parameters passed by the base linker to
getopt_long and getopt_long_only calls. */
void (*add_options)
(int, char **, int, struct option **, int, struct option **);
/* Companion to the above to handle an option. Returns TRUE if it is
one of our options. */
bfd_boolean (*handle_option) (int);
/* Run to handle files which are not recognized as object files or
archives. Return TRUE if the file was handled. */
bfd_boolean (*unrecognized_file)
(struct lang_input_statement_struct *);
/* Run to list the command line options which parse_args handles. */
void (* list_options) (FILE *);
/* Run to specially handle files which *are* recognized as object
files or archives. Return TRUE if the file was handled. */
bfd_boolean (*recognized_file)
(struct lang_input_statement_struct *);
/* Called when looking for libraries in a directory specified
via a linker command line option or linker script option.
Files that match the pattern "lib*.a" have already been scanned.
(For VMS files matching ":lib*.a" have also been scanned). */
int (* find_potential_libraries)
(char *, struct lang_input_statement_struct *);
/* Called when adding a new version pattern. PowerPC64-ELF uses
this hook to add a pattern matching ".foo" for every "foo". */
struct bfd_elf_version_expr * (*new_vers_pattern)
(struct bfd_elf_version_expr *);
/* Called when printing the map file, in case there are
emulation-specific sections for it. */
void (*extra_map_file_text)
(bfd *, struct bfd_link_info *, FILE *);
/* If this returns true, we emit CTF as early as possible: if false, we emit
CTF once the strtab and symtab are laid out. */
int (*emit_ctf_early)
(void);
/* Called to examine the string and symbol table late enough in linking that
they are finally laid out. If emit_ctf_early returns true, this is not
called and ldemul_maybe_emit_ctf() emits CTF in 'early' mode: otherwise, it
waits until 'late'. (Late mode needs explicit support at per-target link
time to get called at all). If set, called by ld when the examine_strtab
bfd_link_callback is invoked by per-target code. */
void (*examine_strtab_for_ctf) (struct ctf_file *, struct elf_sym_strtab *,
bfd_size_type, struct elf_strtab_hash *);
} ld_emulation_xfer_type;
typedef enum {
intel_ic960_ld_mode_enum,
default_mode_enum,
intel_gld960_ld_mode_enum
} lang_emulation_mode_enum_type;
extern ld_emulation_xfer_type *ld_emulations[];
#endif