linux-kernel - [patch 20/38] x86/alternatives: Provide text_poke_[copy|set]

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Message-ID: <20220716230953.858048083@linutronix.de>
Date:   Sun, 17 Jul 2022 01:17:42 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Johannes Wikner <kwikner@...z.ch>,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>,
        Joao Moreira <joao.moreira@...el.com>,
        Joseph Nuzman <joseph.nuzman@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [patch 20/38] x86/alternatives: Provide text_poke_[copy|set]_locked()

The upcoming call thunk patching must hold text_mutex and needs access to
text_poke_copy() and text_poke_set(), which take text_mutex.

Provide _locked postfixed variants to expose the inner workings.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/include/asm/text-patching.h |    2 +
 arch/x86/kernel/alternative.c        |   48 +++++++++++++++++++++--------------
 2 files changed, 32 insertions(+), 18 deletions(-)

--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -45,6 +45,8 @@ extern void *text_poke(void *addr, const
 extern void text_poke_sync(void);
 extern void *text_poke_kgdb(void *addr, const void *opcode, size_t len);
 extern void *text_poke_copy(void *addr, const void *opcode, size_t len);
+extern void *text_poke_copy_locked(void *addr, const void *opcode, size_t len);
+extern void *text_poke_set_locked(void *addr, int c, size_t len);
 extern void *text_poke_set(void *addr, int c, size_t len);
 extern int poke_int3_handler(struct pt_regs *regs);
 extern void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate);
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1225,6 +1225,26 @@ void *text_poke_kgdb(void *addr, const v
 	return __text_poke(text_poke_memcpy, addr, opcode, len);
 }
 
+void *text_poke_copy_locked(void *addr, const void *opcode, size_t len)
+{
+	unsigned long start = (unsigned long)addr;
+	size_t patched = 0;
+
+	if (WARN_ON_ONCE(core_kernel_text(start)))
+		return NULL;
+
+	while (patched < len) {
+		unsigned long ptr = start + patched;
+		size_t s;
+
+		s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched);
+
+		__text_poke(text_poke_memcpy, (void *)ptr, opcode + patched, s);
+		patched += s;
+	}
+	return addr;
+}
+
 /**
  * text_poke_copy - Copy instructions into (an unused part of) RX memory
  * @addr: address to modify
@@ -1239,23 +1259,29 @@ void *text_poke_kgdb(void *addr, const v
  */
 void *text_poke_copy(void *addr, const void *opcode, size_t len)
 {
+	mutex_lock(&text_mutex);
+	addr = text_poke_copy_locked(addr, opcode, len);
+	mutex_unlock(&text_mutex);
+	return addr;
+}
+
+void *text_poke_set_locked(void *addr, int c, size_t len)
+{
 	unsigned long start = (unsigned long)addr;
 	size_t patched = 0;
 
 	if (WARN_ON_ONCE(core_kernel_text(start)))
 		return NULL;
 
-	mutex_lock(&text_mutex);
 	while (patched < len) {
 		unsigned long ptr = start + patched;
 		size_t s;
 
 		s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched);
 
-		__text_poke(text_poke_memcpy, (void *)ptr, opcode + patched, s);
+		__text_poke(text_poke_memset, (void *)ptr, (void *)&c, s);
 		patched += s;
 	}
-	mutex_unlock(&text_mutex);
 	return addr;
 }
 
@@ -1270,22 +1296,8 @@ void *text_poke_copy(void *addr, const v
  */
 void *text_poke_set(void *addr, int c, size_t len)
 {
-	unsigned long start = (unsigned long)addr;
-	size_t patched = 0;
-
-	if (WARN_ON_ONCE(core_kernel_text(start)))
-		return NULL;
-
 	mutex_lock(&text_mutex);
-	while (patched < len) {
-		unsigned long ptr = start + patched;
-		size_t s;
-
-		s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched);
-
-		__text_poke(text_poke_memset, (void *)ptr, (void *)&c, s);
-		patched += s;
-	}
+	addr = text_poke_set_locked(addr, c, len);
 	mutex_unlock(&text_mutex);
 	return addr;
 }