linux-kernel - [RFC v2 2/6] objtool: ignore instructions

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Message-ID: <20181231072112.21051-3-namit@vmware.com>
Date:   Sun, 30 Dec 2018 23:21:08 -0800
From:   Nadav Amit <namit@...are.com>
To:     Ingo Molnar <mingo@...hat.com>, Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Edward Cree <ecree@...arflare.com>
CC:     "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Nadav Amit <nadav.amit@...il.com>, X86 ML <x86@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Nadav Amit <namit@...are.com>
Subject: [RFC v2 2/6] objtool: ignore instructions

In certain cases there is a need to suppress objtool warnings on
specific instructions. Provide an interface to achieve this goal.

Signed-off-by: Nadav Amit <namit@...are.com>
---
 tools/objtool/check.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0414a0d52262..c890d714fb73 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -431,10 +431,11 @@ static int add_dead_ends(struct objtool_file *file)
 /*
  * Warnings shouldn't be reported for ignored functions.
  */
-static void add_ignores(struct objtool_file *file)
+static int add_ignores(struct objtool_file *file)
 {
 	struct instruction *insn;
 	struct section *sec;
+	struct rela *rela;
 	struct symbol *func;
 
 	for_each_sec(file, sec) {
@@ -449,6 +450,20 @@ static void add_ignores(struct objtool_file *file)
 				insn->ignore = true;
 		}
 	}
+
+	sec = find_section_by_name(file->elf, ".rela.discard.ignore");
+	if (!sec)
+		return 0;
+
+	list_for_each_entry(rela, &sec->rela_list, list) {
+		insn = find_insn(file, rela->sym->sec, rela->addend);
+		if (!insn) {
+			WARN("bad .discard.ignore entry");
+			return -1;
+		}
+		insn->ignore = true;
+	}
+	return 0;
 }
 
 /*
@@ -1237,7 +1252,9 @@ static int decode_sections(struct objtool_file *file)
 	if (ret)
 		return ret;
 
-	add_ignores(file);
+	ret = add_ignores(file);
+	if (ret)
+		return ret;
 
 	ret = add_nospec_ignores(file);
 	if (ret)
-- 
2.17.1