linux-kernel - [PATCH v4 13/13] objtool: Also consider .entry.text as noinstr

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Date:   Wed, 25 Mar 2020 18:45:38 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     tglx@...utronix.de, jpoimboe@...hat.com
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, peterz@...radead.org,
        mhiramat@...nel.org, mbenes@...e.cz
Subject: [PATCH v4 13/13] objtool: Also consider .entry.text as noinstr

From: Thomas Gleixner <tglx@...utronix.de>

Consider all of .entry.text as noinstr. This gets us coverage across
the PTI boundary. While we could add everything .noinstr.text into
.entry.text that would bloat the amount of code in the user mapping.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 tools/objtool/check.c |   18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -285,7 +285,8 @@ static int decode_instructions(struct ob
 		    strncmp(sec->name, ".discard.", 9))
 			sec->text = true;
 
-		if (!strcmp(sec->name, ".noinstr.text"))
+		if (!strcmp(sec->name, ".noinstr.text") ||
+		    !strcmp(sec->name, ".entry.text"))
 			sec->noinstr = true;
 
 		for (offset = 0; offset < sec->len; offset += insn->len) {
@@ -2065,7 +2066,7 @@ static inline const char *call_dest_name
 static int validate_call(struct instruction *insn, struct insn_state *state)
 {
 	if (state->noinstr && state->instr <= 0 &&
-	    (!insn->call_dest || insn->call_dest->sec != insn->sec)) {
+	    (!insn->call_dest || !insn->call_dest->sec->noinstr)) {
 		WARN_FUNC("call to %s() leaves .noinstr.text section",
 				insn->sec, insn->offset, call_dest_name(insn));
 		return 1;
@@ -2636,11 +2637,16 @@ static int validate_vmlinux_functions(st
 	int warnings = 0;
 
 	sec = find_section_by_name(file->elf, ".noinstr.text");
-	if (!sec)
-		return 0;
+	if (sec) {
+		warnings += validate_section(file, sec);
+		warnings += validate_unwind_hints(file, sec);
+	}
 
-	warnings += validate_section(file, sec);
-	warnings += validate_unwind_hints(file, sec);
+	sec = find_section_by_name(file->elf, ".entry.text");
+	if (sec) {
+		warnings += validate_section(file, sec);
+		warnings += validate_unwind_hints(file, sec);
+	}
 
 	return warnings;
 }