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Avoid ubsan bug complaining about &p->field

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I reckon it's quite OK to write &p->field in C when p might be NULL,
and lots of old C programmers probably agree with me.  However, ubsan
disagrees and so do some people I respect.  I suspect C++ influence is
to blame for the ubsan behaviour.  See
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92634.  So far no one has
educated me as to why I'm wrong to claim that there isn't anything in
the C standard to say that p->field is always (*p).field.  Note 79
doesn't quite do that because it doesn't cover null pointers.  If
there was such an equivalence then you could claim &p->field has a
null pointer reference when p is NULL, even though no C compiler would
ever dereference p.

Anyway, to silence ubsan I'm going to apply the following though I
prefer to avoid casts when possible.  And I'm using (void *)
deliberately because this is C, not C++!

	* ldlang.c (lang_output_section_find_by_flags): Don't use &p->field
	when p might be NULL.
	* ldelf.c (output_rel_find, ldelf_place_orphan): Likewise.
	(insert_os_after, lang_insert_orphan, lookup_name): Likewise.
	(strip_excluded_output_sections, lang_clear_os_map): Likewise.
	(lang_check, lang_for_each_input_file): Likewise.
	(lang_reset_memory_regions, find_replacements_insert_point): Likewise.
	(find_rescan_insertion, lang_propagate_lma_regions): Likewise.
	(lang_record_phdrs): Likewise.
	* emultempl/alphaelf.em (alpha_after_open): Likewise.
	* emultempl/mmo.em (mmo_place_orphan): Likewise.
	* emultempl/pe.em (gld_${EMULATION_NAME}_place_orphan): Likewise.
	* emultempl/pep.em (gld_${EMULATION_NAME}_place_orphan): Likewise.
	* emultempl/ppc32elf.em (ppc_after_check_relocs): Likewise.
	* emultempl/spuelf.em (spu_before_allocation): Likewise.
	(embedded_spu_file): Likewise.
This commit is contained in:
Alan Modra 2019-11-26 16:49:44 +10:30
parent 100b122fc1
commit 8ce18f9cdf
9 changed files with 44 additions and 25 deletions
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19
ld/ChangeLog
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@ -1,3 +1,22 @@
2019-12-26 Alan Modra <amodra@gmail.com>
* ldlang.c (lang_output_section_find_by_flags): Don't use &p->field
when p might be NULL.
* ldelf.c (output_rel_find, ldelf_place_orphan): Likewise.
(insert_os_after, lang_insert_orphan, lookup_name): Likewise.
(strip_excluded_output_sections, lang_clear_os_map): Likewise.
(lang_check, lang_for_each_input_file): Likewise.
(lang_reset_memory_regions, find_replacements_insert_point): Likewise.
(find_rescan_insertion, lang_propagate_lma_regions): Likewise.
(lang_record_phdrs): Likewise.
* emultempl/alphaelf.em (alpha_after_open): Likewise.
* emultempl/mmo.em (mmo_place_orphan): Likewise.
* emultempl/pe.em (gld_${EMULATION_NAME}_place_orphan): Likewise.
* emultempl/pep.em (gld_${EMULATION_NAME}_place_orphan): Likewise.
* emultempl/ppc32elf.em (ppc_after_check_relocs): Likewise.
* emultempl/spuelf.em (spu_before_allocation): Likewise.
(embedded_spu_file): Likewise.
2019-12-19 Alan Modra <amodra@gmail.com>
* testsuite/lib/ld-lib.exp (uses_genelf): Remove moxie.

2
ld/emultempl/alphaelf.em
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@ -47,7 +47,7 @@ alpha_after_open (void)
lang_output_section_statement_type *plt_os[2];
num_plt = 0;
for (os = &lang_os_list.head->output_section_statement;
for (os = (void *) lang_os_list.head;
os != NULL;
os = os->next)
{

2
ld/emultempl/mmo.em
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@ -163,7 +163,7 @@ mmo_place_orphan (asection *s,
/* We have to find the oss before this one, so we can use that as
"after". */
for (lookup = &lang_os_list.head->output_section_statement;
for (lookup = (void *) lang_os_list.head;
lookup != NULL && lookup->next != before;
lookup = lookup->next)
;

2
ld/emultempl/pe.em
View File

@ -2151,7 +2151,7 @@ gld_${EMULATION_NAME}_place_orphan (asection *s,
NULL);
if (after == NULL)
/* *ABS* is always the first output section statement. */
after = &lang_os_list.head->output_section_statement;
after = (void *) lang_os_list.head;
}
/* All sections in an executable must be aligned to a page boundary.

2
ld/emultempl/pep.em
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@ -1950,7 +1950,7 @@ gld_${EMULATION_NAME}_place_orphan (asection *s,
NULL);
if (after == NULL)
/* *ABS* is always the first output section statement. */
after = &lang_os_list.head->output_section_statement;
after = (void *) lang_os_list.head;
}
/* All sections in an executable must be aligned to a page boundary.

2
ld/emultempl/ppc32elf.em
View File

@ -79,7 +79,7 @@ ppc_after_check_relocs (void)
num_got = 0;
num_plt = 0;
for (os = &lang_os_list.head->output_section_statement;
for (os = (void *) lang_os_list.head;
os != NULL;
os = os->next)
{

4
ld/emultempl/spuelf.em
View File

@ -290,7 +290,7 @@ spu_before_allocation (void)
}
/* Ensure alignment of overlay sections is sufficient. */
for (os = &lang_os_list.head->output_section_statement;
for (os = (void *) lang_os_list.head;
os != NULL;
os = os->next)
if (os->bfd_section != NULL
@ -512,7 +512,7 @@ embedded_spu_file (lang_input_statement_type *entry, const char *flags)
return FALSE;
close (fd);
for (search = &input_file_chain.head->input_statement;
for (search = (void *) input_file_chain.head;
search != NULL;
search = search->next_real_file)
if (search->filename != NULL)

6
ld/ldelf.c
View File

@ -1780,7 +1780,7 @@ output_rel_find (int isdyn, int rela)
lang_output_section_statement_type *last_rel = NULL;
lang_output_section_statement_type *last_rel_alloc = NULL;
for (lookup = &lang_os_list.head->output_section_statement;
for (lookup = (void *) lang_os_list.head;
lookup != NULL;
lookup = lookup->next)
{
@ -1952,7 +1952,7 @@ ldelf_place_orphan (asection *s, const char *secname, int constraint)
{
/* Find the output mbind section with the same type, attributes
and sh_info field. */
for (os = &lang_os_list.head->output_section_statement;
for (os = (void *) lang_os_list.head;
os != NULL;
os = os->next)
if (os->bfd_section != NULL
@ -2129,7 +2129,7 @@ ldelf_place_orphan (asection *s, const char *secname, int constraint)
_bfd_elf_match_sections_by_type);
if (after == NULL)
/* *ABS* is always the first output section statement. */
after = &lang_os_list.head->output_section_statement;
after = (void *) lang_os_list.head;
}
return lang_insert_orphan (s, secname, constraint, after, place, NULL, NULL);

30
ld/ldlang.c
View File

@ -1552,7 +1552,7 @@ lang_output_section_find_by_flags (const asection *sec,
/* We know the first statement on this list is *ABS*. May as well
skip it. */
first = &lang_os_list.head->output_section_statement;
first = (void *) lang_os_list.head;
first = first->next;
/* First try for an exact match. */
@ -1780,7 +1780,7 @@ insert_os_after (lang_output_section_statement_type *after)
lang_statement_union_type **assign = NULL;
bfd_boolean ignore_first;
ignore_first = after == &lang_os_list.head->output_section_statement;
ignore_first = after == (void *) lang_os_list.head;
for (where = &after->header.next;
*where != NULL;
@ -1904,7 +1904,7 @@ lang_insert_orphan (asection *s,
/* Shuffle the bfd section list to make the output file look
neater. This is really only cosmetic. */
if (place->section == NULL
&& after != &lang_os_list.head->output_section_statement)
&& after != (void *) lang_os_list.head)
{
asection *bfd_section = after->bfd_section;
@ -2846,7 +2846,7 @@ lookup_name (const char *name)
{
lang_input_statement_type *search;
for (search = &input_file_chain.head->input_statement;
for (search = (void *) input_file_chain.head;
search != NULL;
search = search->next_real_file)
{
@ -4329,7 +4329,7 @@ strip_excluded_output_sections (void)
lang_reset_memory_regions ();
}
for (os = &lang_os_list.head->output_section_statement;
for (os = (void *) lang_os_list.head;
os != NULL;
os = os->next)
{
@ -4390,7 +4390,7 @@ lang_clear_os_map (void)
if (map_head_is_link_order)
return;
for (os = &lang_os_list.head->output_section_statement;
for (os = (void *) lang_os_list.head;
os != NULL;
os = os->next)
{
@ -6728,7 +6728,7 @@ lang_check (void)
bfd *input_bfd;
const bfd_arch_info_type *compatible;
for (file = &file_chain.head->input_statement;
for (file = (void *) file_chain.head;
file != NULL;
file = file->next)
{
@ -7070,7 +7070,7 @@ lang_for_each_input_file (void (*func) (lang_input_statement_type *))
{
lang_input_statement_type *f;
for (f = &input_file_chain.head->input_statement;
for (f = (void *) input_file_chain.head;
f != NULL;
f = f->next_real_file)
if (f->flags.real)
@ -7196,7 +7196,7 @@ lang_reset_memory_regions (void)
p->last_os = NULL;
}
for (os = &lang_os_list.head->output_section_statement;
for (os = (void *) lang_os_list.head;
os != NULL;
os = os->next)
{
@ -7433,8 +7433,8 @@ static lang_input_statement_type *
find_replacements_insert_point (bfd_boolean *before)
{
lang_input_statement_type *claim1, *lastobject;
lastobject = &input_file_chain.head->input_statement;
for (claim1 = &file_chain.head->input_statement;
lastobject = (void *) input_file_chain.head;
for (claim1 = (void *) file_chain.head;
claim1 != NULL;
claim1 = claim1->next)
{
@ -7476,7 +7476,7 @@ find_rescan_insertion (lang_input_statement_type *add)
file chain if it is full of archive elements. Archives don't
appear on the file chain, but if an element has been extracted
then their input_statement->next points at it. */
for (f = &input_file_chain.head->input_statement;
for (f = (void *) input_file_chain.head;
f != NULL;
f = f->next_real_file)
{
@ -7609,7 +7609,7 @@ lang_propagate_lma_regions (void)
{
lang_output_section_statement_type *os;
for (os = &lang_os_list.head->output_section_statement;
for (os = (void *) lang_os_list.head;
os != NULL;
os = os->next)
{
@ -8286,7 +8286,7 @@ lang_record_phdrs (void)
bfd_vma at;
c = 0;
for (os = &lang_os_list.head->output_section_statement;
for (os = (void *) lang_os_list.head;
os != NULL;
os = os->next)
{
@ -8372,7 +8372,7 @@ lang_record_phdrs (void)
free (secs);
/* Make sure all the phdr assignments succeeded. */
for (os = &lang_os_list.head->output_section_statement;
for (os = (void *) lang_os_list.head;
os != NULL;
os = os->next)
{