linux-kernel - [PATCH v3 12/13] retpoline/objtool: Disable some objtool warnings

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Date:   Thu,  4 Jan 2018 14:37:09 +0000
From:   David Woodhouse <dwmw@...zon.co.uk>
To:     ak@...ux.intel.com
Cc:     Paul Turner <pjt@...gle.com>, LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>, tglx@...utronix.de,
        Kees Cook <keescook@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        Jiri Kosina <jikos@...nel.org>, gnomes@...rguk.ukuu.org.uk,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: [PATCH v3 12/13] retpoline/objtool: Disable some objtool warnings

From: Andi Kleen <ak@...ux.intel.com>

With the indirect call thunk enabled compiler two objtool
warnings are triggered very frequently and make the build
very noisy.

I don't see a good way to avoid them, so just disable them
for now.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
---
 tools/objtool/check.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 9b341584eb1b..435c71f944dc 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -503,8 +503,13 @@ static int add_call_destinations(struct objtool_file *file)
 			insn->call_dest = find_symbol_by_offset(insn->sec,
 								dest_off);
 			if (!insn->call_dest) {
+#if 0
+				/* Compilers with -mindirect-branch=thunk-extern trigger
+				 * this everywhere on x86. Disable for now.
+				 */
 				WARN_FUNC("can't find call dest symbol at offset 0x%lx",
 					  insn->sec, insn->offset, dest_off);
+#endif
 				return -1;
 			}
 		} else if (rela->sym->type == STT_SECTION) {
@@ -1716,8 +1721,14 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
 					return 1;
 
 			} else if (func && has_modified_stack_frame(&state)) {
+#if 0
+				/* Compilers with -mindirect-branch=thunk-extern trigger
+				 * this everywhere on x86. Disable for now.
+				 */
+
 				WARN_FUNC("sibling call from callable instruction with modified stack frame",
 					  sec, insn->offset);
+#endif
 				return 1;
 			}
 
-- 
2.14.3