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From: Nadav Amit <namit@vmware.com>
To: Ingo Molnar <mingo@redhat.com>
Cc: <linux-kernel@vger.kernel.org>, <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>, <linux_dti@icloud.com>,
	<linux-integrity@vger.kernel.org>,
	<linux-security-module@vger.kernel.org>,
	Nadav Amit <namit@vmware.com>, Andy Lutomirski <luto@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Masami Hiramatsu <mhiramat@kernel.org>
Subject: [PATCH v5 09/10] x86/jump-label: remove support for custom poker
Date: Tue, 13 Nov 2018 05:07:29 -0800	[thread overview]
Message-ID: <20181113130730.44844-10-namit@vmware.com> (raw)
In-Reply-To: <20181113130730.44844-1-namit@vmware.com>

There are only two types of poking: early and breakpoint based. The use
of a function pointer to perform poking complicates the code and is
probably inefficient due to the use of indirect branches.

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
---
 arch/x86/kernel/jump_label.c | 24 ++++++++----------------
 1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
index ed5fe274a7d8..994c13e2867d 100644
--- a/arch/x86/kernel/jump_label.c
+++ b/arch/x86/kernel/jump_label.c
@@ -39,7 +39,6 @@ static void bug_at(unsigned char *ip, int line)
 
 static void __ref __jump_label_transform(struct jump_entry *entry,
 					 enum jump_label_type type,
-					 void *(*poker)(void *, const void *, size_t),
 					 int init)
 {
 	union jump_code_union jmp;
@@ -52,14 +51,6 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
 	jmp.offset = jump_entry_target(entry) -
 		     (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
 
-	/*
-	 * As long as we're UP and not yet marked RO, we can use
-	 * text_poke_early; SYSTEM_BOOTING guarantees both, as we switch to
-	 * SYSTEM_SCHEDULING before going either.
-	 */
-	if (system_state == SYSTEM_BOOTING)
-		poker = text_poke_early;
-
 	if (type == JUMP_LABEL_JMP) {
 		if (init) {
 			expect = default_nop; line = __LINE__;
@@ -82,16 +73,17 @@ static void __ref __jump_label_transform(struct jump_entry *entry,
 		bug_at((void *)jump_entry_code(entry), line);
 
 	/*
-	 * Make text_poke_bp() a default fallback poker.
+	 * As long as we're UP and not yet marked RO, we can use
+	 * text_poke_early; SYSTEM_BOOTING guarantees both, as we switch to
+	 * SYSTEM_SCHEDULING before going either.
 	 *
 	 * At the time the change is being done, just ignore whether we
 	 * are doing nop -> jump or jump -> nop transition, and assume
 	 * always nop being the 'currently valid' instruction
-	 *
 	 */
-	if (poker) {
-		(*poker)((void *)jump_entry_code(entry), code,
-			 JUMP_LABEL_NOP_SIZE);
+	if (init || system_state == SYSTEM_BOOTING) {
+		text_poke_early((void *)jump_entry_code(entry), code,
+				JUMP_LABEL_NOP_SIZE);
 		return;
 	}
 
@@ -103,7 +95,7 @@ void arch_jump_label_transform(struct jump_entry *entry,
 			       enum jump_label_type type)
 {
 	mutex_lock(&text_mutex);
-	__jump_label_transform(entry, type, NULL, 0);
+	__jump_label_transform(entry, type, 0);
 	mutex_unlock(&text_mutex);
 }
 
@@ -133,7 +125,7 @@ __init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
 			jlstate = JL_STATE_NO_UPDATE;
 	}
 	if (jlstate == JL_STATE_UPDATE)
-		__jump_label_transform(entry, type, text_poke_early, 1);
+		__jump_label_transform(entry, type, 1);
 }
 
 #endif
-- 
2.17.1


  parent reply	other threads:[~2018-11-13 20:25 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-13 13:07 [PATCH v5 00/10] x86/alternative: text_poke() fixes Nadav Amit
2018-11-13 13:07 ` [PATCH v5 01/10] Fix "x86/alternatives: Lockdep-enforce text_mutex in text_poke*()" Nadav Amit
2018-11-13 13:07 ` [PATCH v5 02/10] x86/jump_label: Use text_poke_early() during early init Nadav Amit
2018-11-20 18:10   ` H. Peter Anvin
2018-11-20 18:18     ` Peter Zijlstra
2018-11-20 18:23       ` H. Peter Anvin
2018-11-20 18:47         ` Nadav Amit
2018-11-13 13:07 ` [PATCH v5 03/10] x86/mm: temporary mm struct Nadav Amit
2018-11-13 13:07 ` [PATCH v5 04/10] fork: provide a function for copying init_mm Nadav Amit
2018-11-13 13:07 ` [PATCH v5 05/10] x86/alternative: initializing temporary mm for patching Nadav Amit
2018-11-13 13:07 ` [PATCH v5 06/10] x86/alternative: use temporary mm for text poking Nadav Amit
2018-11-13 13:07 ` [PATCH v5 07/10] x86/kgdb: avoid redundant comparison of patched code Nadav Amit
2018-11-13 13:07 ` [PATCH v5 08/10] x86: avoid W^X being broken during modules loading Nadav Amit
2018-11-13 13:07 ` Nadav Amit [this message]
2018-11-13 13:07 ` [PATCH v5 10/10] x86/alternative: remove the return value of text_poke_*() Nadav Amit
2018-11-20 12:42 ` [PATCH v5 00/10] x86/alternative: text_poke() fixes Peter Zijlstra
2018-11-20 18:52   ` Nadav Amit

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