linux-kernel - [tip: x86/core] objtool: Correctly handle retpoline thunk calls

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Date:   Sat, 03 Apr 2021 11:10:59 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/core] objtool: Correctly handle retpoline thunk calls

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     bcb1b6ff39da7e8a6a986eb08126fba2b5e13c32
Gitweb:        https://git.kernel.org/tip/bcb1b6ff39da7e8a6a986eb08126fba2b5e13c32
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Fri, 26 Mar 2021 16:12:03 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Fri, 02 Apr 2021 12:42:54 +02:00

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>
Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Miroslav Benes <mbenes@...e.cz>
Link: https://lkml.kernel.org/r/20210326151259.567568238@infradead.org
---
 tools/objtool/check.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index d45f018..519af4b 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1025,6 +1025,18 @@ static int add_call_destinations(struct objtool_file *file)
 					  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 accordingly.
+			 */
+			insn->type = INSN_CALL_DYNAMIC;
+			insn->retpoline_safe = true;
+
+			remove_insn_ops(insn);
+			continue;
+
 		} else
 			insn->call_dest = reloc->sym;