linux-kernel - [PATCH 8/9] objtool: Skip magical retpoline .altinstr

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Message-ID: <20210312171653.832063970@infradead.org>
Date:   Fri, 12 Mar 2021 18:16:21 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, jpoimboe@...hat.com, jgross@...e.com,
        mbenes@...e.cz
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: [PATCH 8/9] objtool: Skip magical retpoline .altinstr_replacement

When the .altinstr_replacement is a retpoline, skip the alternative.
We already special case retpolines anyway.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 tools/objtool/special.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -106,6 +106,14 @@ static int get_alt_entry(struct elf *elf
 			return -1;
 		}
 
+		/*
+		 * Skip retpoline .altinstr_replacement... we already rewrite the
+		 * instructions for retpolines anyway, see arch_is_retpoline()
+		 * usage in add_{call,jump}_destinations().
+		 */
+		if (arch_is_retpoline(new_reloc->sym))
+			return 1;
+
 		alt->new_sec = new_reloc->sym->sec;
 		alt->new_off = (unsigned int)new_reloc->addend;
 
@@ -154,7 +162,9 @@ int special_get_alts(struct elf *elf, st
 			memset(alt, 0, sizeof(*alt));
 
 			ret = get_alt_entry(elf, entry, sec, idx, alt);
-			if (ret)
+			if (ret > 0)
+				continue;
+			if (ret < 0)
 				return ret;
 
 			list_add_tail(&alt->list, alts);