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libctf: warn about information loss because of unreleased format changes

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In the last cycle there have been various changes that have replaced
parts of the CTF format with other parts without format
compatibility.  This was not a compat break, because the old format was
never accepted by any version of libctf (the not-in-official-release CTF
compiler patch was emitting an invalid func info section), but
nonetheless it can confuse users using that patch if they link together
object files and find the func info sections in the inputs silently
disappearing.

Scan the linker inputs for this problem and emit a warning if any are
found.

libctf/ChangeLog
2021-01-05  Nick Alcock  <nick.alcock@oracle.com>

	* ctf-link.c (ctf_link_warn_outdated_inputs): New.
	(ctf_link_write): Call it.
This commit is contained in:
Nick Alcock 2021-01-05 13:25:56 +00:00
parent 9bc769718d
commit abed0b0718
2 changed files with 35 additions and 0 deletions
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5
libctf/ChangeLog
View File

@ -1,3 +1,8 @@
2021-01-05 Nick Alcock <nick.alcock@oracle.com>
* ctf-link.c (ctf_link_warn_outdated_inputs): New.
(ctf_link_write): Call it.
2021-01-05 Nick Alcock <nick.alcock@oracle.com>
* testsuite/libctf-lookup/enum-symbol.lk: New symbol-lookup test.

30
libctf/ctf-link.c
View File

@ -2004,6 +2004,34 @@ ctf_change_parent_name (void *key _libctf_unused_, void *value, void *arg)
ctf_parent_name_set (fp, name);
}
/* Warn if we may suffer information loss because the CTF input files are too
old. Usually we provide complete backward compatibility, but compiler
changes etc which never hit a release may have a flag in the header that
simply prevents those changes from being used. */
static void
ctf_link_warn_outdated_inputs (ctf_dict_t *fp)
{
ctf_next_t *i = NULL;
void *name_;
void *ifp_;
int err;
while ((err = ctf_dynhash_next (fp->ctf_link_inputs, &i, &name_, &ifp_)) == 0)
{
const char *name = (const char *) name_;
ctf_dict_t *ifp = (ctf_dict_t *) ifp_;
if (!(ifp->ctf_header->cth_flags & CTF_F_NEWFUNCINFO)
&& (ifp->ctf_header->cth_varoff - ifp->ctf_header->cth_funcoff) > 0)
ctf_err_warn (ifp, 1, 0, _("linker input %s has CTF func info but uses "
"an old, unreleased func info format: "
"this func info section will be dropped."),
name);
}
if (err != ECTF_NEXT_END)
ctf_err_warn (fp, 0, err, _("error checking for outdated inputs"));
}
/* Write out a CTF archive (if there are per-CU CTF files) or a CTF file
(otherwise) into a new dynamically-allocated string, and return it.
Members with sizes above THRESHOLD are compressed. */
@ -2023,6 +2051,8 @@ ctf_link_write (ctf_dict_t *fp, size_t *size, size_t threshold)
memset (&arg, 0, sizeof (ctf_name_list_accum_cb_arg_t));
arg.fp = fp;
ctf_link_warn_outdated_inputs (fp);
if (fp->ctf_link_outputs)
{
ctf_dynhash_iter (fp->ctf_link_outputs, ctf_accumulate_archive_names, &arg);