From: Ilie Halip <ilie.halip@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: Ilie Halip <ilie.halip@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Rong Chen <rong.a.chen@intel.com>, Marco Elver <elver@google.com>,
Philip Li <philip.li@intel.com>, Borislav Petkov <bp@alien8.de>,
kasan-dev@googlegroups.com, x86@kernel.org,
clang-built-linux@googlegroups.com,
kbuild test robot <lkp@intel.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Nathan Chancellor <natechancellor@gmail.com>
Subject: [PATCH v2] objtool: ignore unreachable trap after call to noreturn functions
Date: Sat, 19 Sep 2020 09:41:18 +0300 [thread overview]
Message-ID: <20200919064118.1899325-1-ilie.halip@gmail.com> (raw)
In-Reply-To: <20200918154840.h3xbspb5jq7zw755@treble>
With CONFIG_UBSAN_TRAP enabled, the compiler may insert a trap instruction
after a call to a noreturn function. In this case, objtool warns that the
ud2 instruction is unreachable.
This is a behavior seen with clang, from the oldest version capable of
building the mainline x64_64 kernel (9.0), to the latest experimental
version (12.0).
objtool silences similar warnings (trap after dead end instructions), so
so expand that check to include dead end functions.
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Rong Chen <rong.a.chen@intel.com>
Cc: Marco Elver <elver@google.com>
Cc: Philip Li <philip.li@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: kasan-dev@googlegroups.com
Cc: x86@kernel.org
Cc: clang-built-linux@googlegroups.com
BugLink: https://github.com/ClangBuiltLinux/linux/issues/1148
Link: https://lore.kernel.org/lkml/CAKwvOdmptEpi8fiOyWUo=AiZJiX+Z+VHJOM2buLPrWsMTwLnyw@mail.gmail.com
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Ilie Halip <ilie.halip@gmail.com>
---
Changed in v2:
- added a mention that this is a clang issue across all versions
- added Nick's Reviewed-by, Tested-by
- added Reported-by
tools/objtool/check.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index e034a8f24f46..eddf8bf16b05 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2612,9 +2612,10 @@ static bool is_ubsan_insn(struct instruction *insn)
"__ubsan_handle_builtin_unreachable"));
}
-static bool ignore_unreachable_insn(struct instruction *insn)
+static bool ignore_unreachable_insn(struct objtool_file *file, struct instruction *insn)
{
int i;
+ struct instruction *prev_insn;
if (insn->ignore || insn->type == INSN_NOP)
return true;
@@ -2639,8 +2640,11 @@ static bool ignore_unreachable_insn(struct instruction *insn)
* __builtin_unreachable(). The BUG() macro has an unreachable() after
* the UD2, which causes GCC's undefined trap logic to emit another UD2
* (or occasionally a JMP to UD2).
+ * CONFIG_UBSAN_TRAP may also insert a UD2 after calling a __noreturn
+ * function.
*/
- if (list_prev_entry(insn, list)->dead_end &&
+ prev_insn = list_prev_entry(insn, list);
+ if ((prev_insn->dead_end || dead_end_function(file, prev_insn->call_dest)) &&
(insn->type == INSN_BUG ||
(insn->type == INSN_JUMP_UNCONDITIONAL &&
insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
@@ -2767,7 +2771,7 @@ static int validate_reachable_instructions(struct objtool_file *file)
return 0;
for_each_insn(file, insn) {
- if (insn->visited || ignore_unreachable_insn(insn))
+ if (insn->visited || ignore_unreachable_insn(file, insn))
continue;
WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
--
2.25.1
next prev parent reply other threads:[~2020-09-19 6:41 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-17 8:49 [PATCH] objtool: ignore unreachable trap after call to noreturn functions Ilie Halip
2020-09-17 18:15 ` Nick Desaulniers
2020-09-17 22:16 ` Josh Poimboeuf
2020-09-18 5:35 ` Ilie Halip
2020-09-18 15:51 ` Josh Poimboeuf
2020-09-19 6:41 ` Ilie Halip [this message]
2020-09-19 11:02 ` [PATCH v2] " Sedat Dilek
2020-09-21 15:19 ` Josh Poimboeuf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200919064118.1899325-1-ilie.halip@gmail.com \
--to=ilie.halip@gmail.com \
--cc=bp@alien8.de \
--cc=clang-built-linux@googlegroups.com \
--cc=elver@google.com \
--cc=jpoimboe@redhat.com \
--cc=kasan-dev@googlegroups.com \
--cc=linux-kernel@vger.kernel.org \
--cc=lkp@intel.com \
--cc=natechancellor@gmail.com \
--cc=ndesaulniers@google.com \
--cc=peterz@infradead.org \
--cc=philip.li@intel.com \
--cc=rong.a.chen@intel.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.