From: Kees Cook <keescook@chromium.org>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Kristen Carlson Accardi <kristen@linux.intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] objtool: optimize add_dead_ends for split sections
Date: Tue, 21 Apr 2020 16:43:45 -0700 [thread overview]
Message-ID: <202004211643.CACC511DD@keescook> (raw)
In-Reply-To: <20200421220843.188260-3-samitolvanen@google.com>
On Tue, Apr 21, 2020 at 03:08:43PM -0700, Sami Tolvanen wrote:
> Instead of iterating through all instructions to find the last
> instruction each time .rela.discard.(un)reachable points beyond the
> section, use find_insn to locate the last instruction by looking at
> the last bytes of the section instead.
>
> Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
-Kees
> ---
> tools/objtool/check.c | 36 +++++++++++++++++-------------------
> 1 file changed, 17 insertions(+), 19 deletions(-)
>
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 4b170fd08a28..4f1d405420a4 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -303,6 +303,19 @@ static int decode_instructions(struct objtool_file *file)
> return ret;
> }
>
> +static struct instruction *find_last_insn(struct objtool_file *file,
> + struct section *sec)
> +{
> + struct instruction *insn = NULL;
> + unsigned int offset;
> + unsigned int end = (sec->len > 10) ? sec->len - 10 : 0;
> +
> + for (offset = sec->len - 1; offset >= end && !insn; offset--)
> + insn = find_insn(file, sec, offset);
> +
> + return insn;
> +}
> +
> /*
> * Mark "ud2" instructions and manually annotated dead ends.
> */
> @@ -311,7 +324,6 @@ static int add_dead_ends(struct objtool_file *file)
> struct section *sec;
> struct rela *rela;
> struct instruction *insn;
> - bool found;
>
> /*
> * By default, "ud2" is a dead end unless otherwise annotated, because
> @@ -337,15 +349,8 @@ static int add_dead_ends(struct objtool_file *file)
> if (insn)
> insn = list_prev_entry(insn, list);
> else if (rela->addend == rela->sym->sec->len) {
> - found = false;
> - list_for_each_entry_reverse(insn, &file->insn_list, list) {
> - if (insn->sec == rela->sym->sec) {
> - found = true;
> - break;
> - }
> - }
> -
> - if (!found) {
> + insn = find_last_insn(file, rela->sym->sec);
> + if (!insn) {
> WARN("can't find unreachable insn at %s+0x%x",
> rela->sym->sec->name, rela->addend);
> return -1;
> @@ -379,15 +384,8 @@ static int add_dead_ends(struct objtool_file *file)
> if (insn)
> insn = list_prev_entry(insn, list);
> else if (rela->addend == rela->sym->sec->len) {
> - found = false;
> - list_for_each_entry_reverse(insn, &file->insn_list, list) {
> - if (insn->sec == rela->sym->sec) {
> - found = true;
> - break;
> - }
> - }
> -
> - if (!found) {
> + insn = find_last_insn(file, rela->sym->sec);
> + if (!insn) {
> WARN("can't find reachable insn at %s+0x%x",
> rela->sym->sec->name, rela->addend);
> return -1;
> --
> 2.26.1.301.g55bc3eb7cb9-goog
>
--
Kees Cook
next prev parent reply other threads:[~2020-04-21 23:43 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 18:07 [PATCH 0/3] objtool: add support for >64k sections Sami Tolvanen
2020-04-21 18:07 ` [PATCH 1/3] objtool: use gelf_getsymshndx to handle " Sami Tolvanen
2020-04-21 20:11 ` Kees Cook
2020-04-21 18:07 ` [PATCH 2/3] objtool: optimize insn_hash for split sections Sami Tolvanen
2020-04-21 19:47 ` Peter Zijlstra
2020-04-21 20:13 ` Kees Cook
2020-04-21 20:20 ` Sami Tolvanen
2020-04-21 18:07 ` [PATCH 3/3] objtool: optimize add_dead_ends " Sami Tolvanen
2020-04-21 20:13 ` Josh Poimboeuf
2020-04-21 20:17 ` Kees Cook
2020-04-21 22:02 ` Sami Tolvanen
2020-04-21 20:14 ` Kees Cook
2020-04-21 20:11 ` [PATCH 0/3] objtool: add support for >64k sections Kees Cook
2020-04-21 22:08 ` [PATCH v2 0/2] " Sami Tolvanen
2020-04-21 22:08 ` [PATCH v2 1/2] objtool: use gelf_getsymshndx to handle " Sami Tolvanen
2020-05-15 17:22 ` [tip: objtool/core] " tip-bot2 for Sami Tolvanen
2020-04-21 22:08 ` [PATCH v2 2/2] objtool: optimize add_dead_ends for split sections Sami Tolvanen
2020-04-21 23:43 ` Kees Cook [this message]
2020-05-15 17:22 ` [tip: objtool/core] " tip-bot2 for Sami Tolvanen
2020-04-21 23:52 ` [PATCH v2 0/2] objtool: add support for >64k sections Josh Poimboeuf
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