linux-kernel - [RFC][PATCH 1/6] objtool: Correctly handle retpoline thunk calls

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Date:   Fri, 19 Feb 2021 21:43:01 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     jpoimboe@...hat.com, x86@...nel.org, pjt@...gle.com,
        mbenes@...e.cz, jgross@...e.com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: [RFC][PATCH 1/6] objtool: Correctly handle retpoline thunk calls

Just like JMP handling, convert a direct CALL to a retpoline thunk
into a retpoline safe indirect CALL.

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

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -953,6 +953,18 @@ static int add_call_destinations(struct
 					  dest_off);
 				return -1;
 			}
+
+		} else if (!strncmp(reloc->sym->name, "__x86_indirect_thunk_", 21)) {
+			/*
+			 * Retpoline calls are really dynamic calls in
+			 * disguise, so convert them accodingly.
+			 */
+			insn->type = INSN_CALL_DYNAMIC;
+			insn->retpoline_safe = true;
+
+			remove_insn_ops(insn);
+			continue;
+
 		} else
 			insn->call_dest = reloc->sym;