All of lore.kernel.org
 help / color / mirror / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org,
	keescook@chromium.org, hjl.tools@gmail.com,
	andrew.cooper3@citrix.com, mark.rutland@arm.com, will@kernel.org,
	ndesaulniers@google.com
Subject: [PATCH v2 4/6] objtool: Add straight-line-speculation validation
Date: Sat, 04 Dec 2021 14:43:42 +0100	[thread overview]
Message-ID: <20211204134908.023037659@infradead.org> (raw)
In-Reply-To: 20211204134338.760603010@infradead.org

Teach objtool to validate the straight-line-speculation constraints:

 - speculation trap after indirect calls
 - speculation trap after ret

Notable: when an instruction is annotated RETPOLINE_SAFE, indicating
  speculation isn't a problem, also don't care about sls for that
  instruction.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 tools/objtool/arch/x86/decode.c         |   13 +++++++++----
 tools/objtool/builtin-check.c           |    3 ++-
 tools/objtool/check.c                   |   14 ++++++++++++++
 tools/objtool/include/objtool/arch.h    |    1 +
 tools/objtool/include/objtool/builtin.h |    2 +-
 5 files changed, 27 insertions(+), 6 deletions(-)

--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -531,6 +531,11 @@ int arch_decode_instruction(struct objto
 		}
 		break;
 
+	case 0xcc:
+		/* int3 */
+		*type = INSN_TRAP;
+		break;
+
 	case 0xe3:
 		/* jecxz/jrcxz */
 		*type = INSN_JUMP_CONDITIONAL;
@@ -697,10 +702,10 @@ const char *arch_ret_insn(int len)
 {
 	static const char ret[5][5] = {
 		{ BYTE_RET },
-		{ BYTE_RET, BYTES_NOP1 },
-		{ BYTE_RET, BYTES_NOP2 },
-		{ BYTE_RET, BYTES_NOP3 },
-		{ BYTE_RET, BYTES_NOP4 },
+		{ BYTE_RET, 0xcc },
+		{ BYTE_RET, 0xcc, BYTES_NOP1 },
+		{ BYTE_RET, 0xcc, BYTES_NOP2 },
+		{ BYTE_RET, 0xcc, BYTES_NOP3 },
 	};
 
 	if (len < 1 || len > 5) {
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -20,7 +20,7 @@
 #include <objtool/objtool.h>
 
 bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats,
-     validate_dup, vmlinux, mcount, noinstr, backup;
+     validate_dup, vmlinux, mcount, noinstr, backup, sls;
 
 static const char * const check_usage[] = {
 	"objtool check [<options>] file.o",
@@ -45,6 +45,7 @@ const struct option check_options[] = {
 	OPT_BOOLEAN('l', "vmlinux", &vmlinux, "vmlinux.o validation"),
 	OPT_BOOLEAN('M', "mcount", &mcount, "generate __mcount_loc"),
 	OPT_BOOLEAN('B', "backup", &backup, "create .orig files before modification"),
+	OPT_BOOLEAN('S', "sls", &sls, "validate straight-line-speculation"),
 	OPT_END(),
 };
 
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3084,6 +3084,12 @@ static int validate_branch(struct objtoo
 		switch (insn->type) {
 
 		case INSN_RETURN:
+			if (next_insn && next_insn->type == INSN_TRAP) {
+				next_insn->ignore = true;
+			} else if (sls && !insn->retpoline_safe) {
+				WARN_FUNC("missing int3 after ret",
+					  insn->sec, insn->offset);
+			}
 			return validate_return(func, insn, &state);
 
 		case INSN_CALL:
@@ -3127,6 +3133,14 @@ static int validate_branch(struct objtoo
 			break;
 
 		case INSN_JUMP_DYNAMIC:
+			if (next_insn && next_insn->type == INSN_TRAP) {
+				next_insn->ignore = true;
+			} else if (sls && !insn->retpoline_safe) {
+				WARN_FUNC("missing int3 after indirect jump",
+					  insn->sec, insn->offset);
+			}
+
+			/* fallthrough */
 		case INSN_JUMP_DYNAMIC_CONDITIONAL:
 			if (is_sibling_call(insn)) {
 				ret = validate_sibling_call(file, insn, &state);
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -26,6 +26,7 @@ enum insn_type {
 	INSN_CLAC,
 	INSN_STD,
 	INSN_CLD,
+	INSN_TRAP,
 	INSN_OTHER,
 };
 
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -9,7 +9,7 @@
 
 extern const struct option check_options[];
 extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats,
-            validate_dup, vmlinux, mcount, noinstr, backup;
+            validate_dup, vmlinux, mcount, noinstr, backup, sls;
 
 extern int cmd_parse_options(int argc, const char **argv, const char * const usage[]);
 



  parent reply	other threads:[~2021-12-04 13:54 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-04 13:43 [PATCH v2 0/6] x86: Add stright-line-speculation mitigations Peter Zijlstra
2021-12-04 13:43 ` [PATCH v2 1/6] x86/atomic64_386_32: Rename things Peter Zijlstra
2021-12-10 11:05   ` [tip: x86/core] x86/lib/atomic64_386_32: " tip-bot2 for Peter Zijlstra
2021-12-04 13:43 ` [PATCH v2 2/6] x86: Prepare asm files for straight-line-speculation Peter Zijlstra
2021-12-10 11:05   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-12-04 13:43 ` [PATCH v2 3/6] x86: Prepare inline-asm " Peter Zijlstra
2021-12-10 11:05   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-12-04 13:43 ` Peter Zijlstra [this message]
2021-12-10 11:05   ` [tip: x86/core] objtool: Add straight-line-speculation validation tip-bot2 for Peter Zijlstra
2021-12-04 13:43 ` [PATCH v2 5/6] x86/alternative: Relax text_poke_bp() constraint Peter Zijlstra
2021-12-10 11:05   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-12-04 13:43 ` [PATCH v2 6/6] x86: Add straight-line-speculation mitigation Peter Zijlstra
2021-12-10 11:05   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2022-07-19 13:19   ` Missing SLS int3 in JMP_NOSPEC? (Was: [PATCH v2 6/6] x86: Add straight-line-speculation mitigation) Maciej S. Szmigiero
2022-07-19 21:23     ` [RFC][PATCH] x86,nospec: Simplify {JMP,CALL}_NOSPEC Peter Zijlstra
2022-07-19 21:33       ` Peter Zijlstra
2022-07-20  0:01         ` Maciej S. Szmigiero
2022-07-20  9:12           ` Peter Zijlstra

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20211204134908.023037659@infradead.org \
    --to=peterz@infradead.org \
    --cc=andrew.cooper3@citrix.com \
    --cc=hjl.tools@gmail.com \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=ndesaulniers@google.com \
    --cc=will@kernel.org \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.