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binutils-gdb/libctf/ctf-util.c
Nick Alcock 149ce5c263 libctf: replace 'pending refs' abstraction
A few years ago we introduced a 'pending refs' abstraction to fix one
problem: serializing a dict, then changing it would tend to corrupt the dict
because the strtab sort we do on strtab writeout (to improve compression
efficiency) would modify the offset of any strings that sorted
lexicographically earlier in the strtab: so we added a new restriction that
all strings are added only at serialization time, and maintained a set of
'pending' refs that were added earlier, whose offsets we could update (like
other refs) at writeout time.

This was in hindsight seriously problematic for maintenance (because
serialization has to traverse all strings in all datatypes in the entire
dict), and has become impossible to sustain now that we can read in existing
dicts, modify them, and reserialize them again.  We really don't want to
have to dig through the entire dict we jut read in just in order to dig out
all its strtab offsets, then *change* it, just for the sake of a sort that
adds a frankly trivial amount of compression efficiency.

Sorting *is* still worthwhile -- but it sacrifices very little to only sort
newly-added portions of the strtab, reusing older portions as necessary.
As a first stage in this, discard the whole "pending refs" abstraction and
replace it with "movable" refs, which are exactly like all other refs
(addresses containing the strtab offset of some string, which are updated
wiht the final strtab offset on serialization) except that we track them in
a reverse dict so that we can move the refs around (which we do whenever we
realloc() a buffer containing a bunch of structure members or something when
we add members to the structure).

libctf/

	* ctf-create.c (ctf_add_enumerator): Call ctf_str_move_refs; add
        a movable ref.
	(ctf_add_member_offset): Likewise.
	* ctf-util.c (ctf_realloc): Delete.
	* ctf-serialize.c (ctf_serialize): No longer use it.  Adjust to
	new fields.
	* ctf-string.c (ctf_str_purge_atom_refs): Purge movable refs.
	(ctf_str_free_atom): Free freeable atoms' strings.
	(ctf_str_create_atoms): Create the movable refs dynhash if needed.
	(ctf_str_free_atoms): Destroy it.
	(CTF_STR_MOVABLE): Switch (back) from ints to flags (see previous
	reversion).  Add new flag.
	(aref_create):  New, populate movable refs if need be.
	(ctf_str_add_ref_internal): Switch back to flags, update refs
	directly for nonprovisional strings (with already-known fixed offsets);
	create refs via aref_create.  Allocate strings only if not within an
	mmapped strtab.
	(ctf_str_add_movable_ref): New.
	(ctf_str_add): Adjust to CTF_STR_* reintroduction.
	(ctf_str_add_external): LIkewise.
	(ctf_str_move_refs): New, move refs via ctf_str_movable_refs
	backpointer.
	(ctf_str_purge_refs): Drop ctf_str_num_refs.
	(ctf_str_update_refs): Fix indentation.
	* ctf-impl.h (struct ctf_str_atom_movable): New.
	(struct ctf_dict.ctf_str_num_refs): Drop.
	(struct ctf_dict.ctf_str_movable_refs): New.
	(ctf_str_add_movable_ref): Declare.
	(ctf_str_move_refs): Likewise.
	(ctf_realloc): Drop.
2024-04-19 16:14:46 +01:00

292 lines
6.9 KiB
C

/* Miscellaneous utilities.
Copyright (C) 2019-2024 Free Software Foundation, Inc.
This file is part of libctf.
libctf 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.
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; see the file COPYING. If not see
<http://www.gnu.org/licenses/>. */
#include <ctf-impl.h>
#include <string.h>
#include "ctf-endian.h"
/* Simple doubly-linked list append routine. This implementation assumes that
each list element contains an embedded ctf_list_t as the first member.
An additional ctf_list_t is used to store the head (l_next) and tail
(l_prev) pointers. The current head and tail list elements have their
previous and next pointers set to NULL, respectively. */
void
ctf_list_append (ctf_list_t *lp, void *newp)
{
ctf_list_t *p = lp->l_prev; /* p = tail list element. */
ctf_list_t *q = newp; /* q = new list element. */
lp->l_prev = q;
q->l_prev = p;
q->l_next = NULL;
if (p != NULL)
p->l_next = q;
else
lp->l_next = q;
}
/* Prepend the specified existing element to the given ctf_list_t. The
existing pointer should be pointing at a struct with embedded ctf_list_t. */
void
ctf_list_prepend (ctf_list_t * lp, void *newp)
{
ctf_list_t *p = newp; /* p = new list element. */
ctf_list_t *q = lp->l_next; /* q = head list element. */
lp->l_next = p;
p->l_prev = NULL;
p->l_next = q;
if (q != NULL)
q->l_prev = p;
else
lp->l_prev = p;
}
/* Delete the specified existing element from the given ctf_list_t. The
existing pointer should be pointing at a struct with embedded ctf_list_t. */
void
ctf_list_delete (ctf_list_t *lp, void *existing)
{
ctf_list_t *p = existing;
if (p->l_prev != NULL)
p->l_prev->l_next = p->l_next;
else
lp->l_next = p->l_next;
if (p->l_next != NULL)
p->l_next->l_prev = p->l_prev;
else
lp->l_prev = p->l_prev;
}
/* Return 1 if the list is empty. */
int
ctf_list_empty_p (ctf_list_t *lp)
{
return (lp->l_next == NULL && lp->l_prev == NULL);
}
/* Splice one entire list onto the end of another one. The existing list is
emptied. */
void
ctf_list_splice (ctf_list_t *lp, ctf_list_t *append)
{
if (ctf_list_empty_p (append))
return;
if (lp->l_prev != NULL)
lp->l_prev->l_next = append->l_next;
else
lp->l_next = append->l_next;
append->l_next->l_prev = lp->l_prev;
lp->l_prev = append->l_prev;
append->l_next = NULL;
append->l_prev = NULL;
}
/* Convert a 32-bit ELF symbol to a ctf_link_sym_t. */
ctf_link_sym_t *
ctf_elf32_to_link_sym (ctf_dict_t *fp, ctf_link_sym_t *dst, const Elf32_Sym *src,
uint32_t symidx)
{
Elf32_Sym tmp;
int needs_flipping = 0;
#ifdef WORDS_BIGENDIAN
if (fp->ctf_symsect_little_endian)
needs_flipping = 1;
#else
if (!fp->ctf_symsect_little_endian)
needs_flipping = 1;
#endif
memcpy (&tmp, src, sizeof (Elf32_Sym));
if (needs_flipping)
{
swap_thing (tmp.st_name);
swap_thing (tmp.st_size);
swap_thing (tmp.st_shndx);
swap_thing (tmp.st_value);
}
/* The name must be in the external string table. */
if (tmp.st_name < fp->ctf_str[CTF_STRTAB_1].cts_len)
dst->st_name = (const char *) fp->ctf_str[CTF_STRTAB_1].cts_strs + tmp.st_name;
else
dst->st_name = _CTF_NULLSTR;
dst->st_nameidx_set = 0;
dst->st_symidx = symidx;
dst->st_shndx = tmp.st_shndx;
dst->st_type = ELF32_ST_TYPE (tmp.st_info);
dst->st_value = tmp.st_value;
return dst;
}
/* Convert a 64-bit ELF symbol to a ctf_link_sym_t. */
ctf_link_sym_t *
ctf_elf64_to_link_sym (ctf_dict_t *fp, ctf_link_sym_t *dst, const Elf64_Sym *src,
uint32_t symidx)
{
Elf64_Sym tmp;
int needs_flipping = 0;
#ifdef WORDS_BIGENDIAN
if (fp->ctf_symsect_little_endian)
needs_flipping = 1;
#else
if (!fp->ctf_symsect_little_endian)
needs_flipping = 1;
#endif
memcpy (&tmp, src, sizeof (Elf64_Sym));
if (needs_flipping)
{
swap_thing (tmp.st_name);
swap_thing (tmp.st_size);
swap_thing (tmp.st_shndx);
swap_thing (tmp.st_value);
}
/* The name must be in the external string table. */
if (tmp.st_name < fp->ctf_str[CTF_STRTAB_1].cts_len)
dst->st_name = (const char *) fp->ctf_str[CTF_STRTAB_1].cts_strs + tmp.st_name;
else
dst->st_name = _CTF_NULLSTR;
dst->st_nameidx_set = 0;
dst->st_symidx = symidx;
dst->st_shndx = tmp.st_shndx;
dst->st_type = ELF32_ST_TYPE (tmp.st_info);
/* We only care if the value is zero, so avoid nonzeroes turning into
zeroes. */
if (_libctf_unlikely_ (tmp.st_value != 0 && ((uint32_t) tmp.st_value == 0)))
dst->st_value = 1;
else
dst->st_value = (uint32_t) tmp.st_value;
return dst;
}
/* A string appender working on dynamic strings. Returns NULL on OOM. */
char *
ctf_str_append (char *s, const char *append)
{
size_t s_len = 0;
if (append == NULL)
return s;
if (s != NULL)
s_len = strlen (s);
size_t append_len = strlen (append);
if ((s = realloc (s, s_len + append_len + 1)) == NULL)
return NULL;
memcpy (s + s_len, append, append_len);
s[s_len + append_len] = '\0';
return s;
}
/* A version of ctf_str_append that returns the old string on OOM. */
char *
ctf_str_append_noerr (char *s, const char *append)
{
char *new_s;
new_s = ctf_str_append (s, append);
if (!new_s)
return s;
return new_s;
}
/* Store the specified error code into errp if it is non-NULL, and then
return NULL for the benefit of the caller. */
void *
ctf_set_open_errno (int *errp, int error)
{
if (errp != NULL)
*errp = error;
return NULL;
}
/* Create a ctf_next_t. */
ctf_next_t *
ctf_next_create (void)
{
return calloc (1, sizeof (struct ctf_next));
}
/* Destroy a ctf_next_t, for early exit from iterators. */
void
ctf_next_destroy (ctf_next_t *i)
{
if (i == NULL)
return;
if (i->ctn_iter_fun == (void (*) (void)) ctf_dynhash_next_sorted)
free (i->u.ctn_sorted_hkv);
if (i->ctn_next)
ctf_next_destroy (i->ctn_next);
free (i);
}
/* Copy a ctf_next_t. */
ctf_next_t *
ctf_next_copy (ctf_next_t *i)
{
ctf_next_t *i2;
if ((i2 = ctf_next_create()) == NULL)
return NULL;
memcpy (i2, i, sizeof (struct ctf_next));
if (i2->ctn_iter_fun == (void (*) (void)) ctf_dynhash_next_sorted)
{
size_t els = ctf_dynhash_elements ((ctf_dynhash_t *) i->cu.ctn_h);
if ((i2->u.ctn_sorted_hkv = calloc (els, sizeof (ctf_next_hkv_t))) == NULL)
{
free (i2);
return NULL;
}
memcpy (i2->u.ctn_sorted_hkv, i->u.ctn_sorted_hkv,
els * sizeof (ctf_next_hkv_t));
}
return i2;
}