From abed0b0718a6a9cd24cc68fb1f73baf6b31d8ff4 Mon Sep 17 00:00:00 2001 From: Nick Alcock Date: Tue, 5 Jan 2021 13:25:56 +0000 Subject: [PATCH] libctf: warn about information loss because of unreleased format changes 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 * ctf-link.c (ctf_link_warn_outdated_inputs): New. (ctf_link_write): Call it. --- libctf/ChangeLog | 5 +++++ libctf/ctf-link.c | 30 ++++++++++++++++++++++++++++++ 2 files changed, 35 insertions(+) diff --git a/libctf/ChangeLog b/libctf/ChangeLog index f11b511922e..db75fd5a836 100644 --- a/libctf/ChangeLog +++ b/libctf/ChangeLog @@ -1,3 +1,8 @@ +2021-01-05 Nick Alcock + + * ctf-link.c (ctf_link_warn_outdated_inputs): New. + (ctf_link_write): Call it. + 2021-01-05 Nick Alcock * testsuite/libctf-lookup/enum-symbol.lk: New symbol-lookup test. diff --git a/libctf/ctf-link.c b/libctf/ctf-link.c index 14ed322c0b9..5384b20543a 100644 --- a/libctf/ctf-link.c +++ b/libctf/ctf-link.c @@ -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); -- 2.30.2