linux-kernel - [PATCH 05/14] objtool: Rename the skylake hack to --direct-call

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Message-Id: <20240927194924.839606244@infradead.org>
Date: Fri, 27 Sep 2024 21:49:01 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
 peterz@...radead.org,
 alyssa.milburn@...el.com,
 scott.d.constable@...el.com,
 joao@...rdrivepizza.com,
 andrew.cooper3@...rix.com,
 jpoimboe@...nel.org,
 jose.marchesi@...cle.com,
 hjl.tools@...il.com,
 ndesaulniers@...gle.com,
 samitolvanen@...gle.com,
 nathan@...nel.org,
 ojeda@...nel.org,
 kees@...nel.org,
 alexei.starovoitov@...il.com
Subject: [PATCH 05/14] objtool: Rename the skylake hack to --direct-call

In order to use the .call_sites and .tail_call_sites sections beyond the
call-depth-tracking skylake thing, give it a more generic name.

Specifically it will be used to 'relink' all direct calls to avoid ENDBR.

A compiler could only hope to do this using an LTO pass, and even then the
dynamic linker would need to get involved.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 scripts/Makefile.lib                    |    2 +-
 tools/objtool/builtin-check.c           |    8 ++------
 tools/objtool/check.c                   |   18 +++++++++---------
 tools/objtool/include/objtool/builtin.h |    2 +-
 4 files changed, 13 insertions(+), 17 deletions(-)

--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -267,7 +267,7 @@ objtool := $(objtree)/tools/objtool/objt
 
 objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK)		+= --hacks=jump_label
 objtool-args-$(CONFIG_HAVE_NOINSTR_HACK)		+= --hacks=noinstr
-objtool-args-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --hacks=skylake
+objtool-args-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --direct-call
 objtool-args-$(CONFIG_X86_KERNEL_IBT)			+= --ibt
 objtool-args-$(CONFIG_FINEIBT)				+= --cfi
 objtool-args-$(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL)	+= --mcount
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -57,17 +57,13 @@ static int parse_hacks(const struct opti
 		found = true;
 	}
 
-	if (!str || strstr(str, "skylake")) {
-		opts.hack_skylake = true;
-		found = true;
-	}
-
 	return found ? 0 : -1;
 }
 
 static const struct option check_options[] = {
 	OPT_GROUP("Actions:"),
-	OPT_CALLBACK_OPTARG('h', "hacks", NULL, NULL, "jump_label,noinstr,skylake", "patch toolchain bugs/limitations", parse_hacks),
+	OPT_CALLBACK_OPTARG('h', "hacks", NULL, NULL, "jump_label,noinstr", "patch toolchain bugs/limitations", parse_hacks),
+	OPT_BOOLEAN(0,   "direct-call", &opts.direct_call, "annotate direct calls"),
 	OPT_BOOLEAN('i', "ibt", &opts.ibt, "validate and annotate IBT"),
 	OPT_BOOLEAN('m', "mcount", &opts.mcount, "annotate mcount/fentry calls for ftrace"),
 	OPT_BOOLEAN('n', "noinstr", &opts.noinstr, "validate noinstr rules"),
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4838,16 +4838,16 @@ int check(struct objtool_file *file)
 		if (ret < 0)
 			goto out;
 		warnings += ret;
+	}
 
-		if (opts.hack_skylake) {
-			ret = create_direct_call_sections(file);
-			if (ret < 0)
-				goto out;
-			ret = create_direct_tail_call_sections(file);
-			if (ret < 0)
-				goto out;
-			warnings += ret;
-		}
+	if (opts.direct_call) {
+		ret = create_direct_call_sections(file);
+		if (ret < 0)
+			goto out;
+		ret = create_direct_tail_call_sections(file);
+		if (ret < 0)
+			goto out;
+		warnings += ret;
 	}
 
 	if (opts.mcount) {
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -12,7 +12,7 @@ struct opts {
 	bool dump_orc;
 	bool hack_jump_label;
 	bool hack_noinstr;
-	bool hack_skylake;
+	bool direct_call;
 	bool ibt;
 	bool mcount;
 	bool noinstr;