linux-kernel - [PATCH -v5 13/17] arm/ftrace: Use __patch_text

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Date:   Mon, 11 Nov 2019 14:13:05 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        rostedt@...dmis.org, mhiramat@...nel.org, bristot@...hat.com,
        jbaron@...mai.com, torvalds@...ux-foundation.org,
        tglx@...utronix.de, mingo@...nel.org, namit@...are.com,
        hpa@...or.com, luto@...nel.org, ard.biesheuvel@...aro.org,
        jpoimboe@...hat.com, jeyu@...nel.org, alexei.starovoitov@...il.com,
        rabin@....in, Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>, james.morse@....com
Subject: [PATCH -v5 13/17] arm/ftrace: Use __patch_text_real()

Instead of flipping text protection, use the patch_text infrastructure
that uses a fixmap alias where required.

This removes the last user of set_all_modules_text_*().

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: ard.biesheuvel@...aro.org
Cc: rabin@....in
Cc: Mark Rutland <mark.rutland@....com>
Cc: Will Deacon <will@...nel.org>
Cc: james.morse@....com
---
 arch/arm/kernel/ftrace.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -22,6 +22,7 @@
 #include <asm/ftrace.h>
 #include <asm/insn.h>
 #include <asm/set_memory.h>
+#include <asm/patch.h>
 
 #ifdef CONFIG_THUMB2_KERNEL
 #define	NOP		0xf85deb04	/* pop.w {lr} */
@@ -31,13 +32,15 @@
 
 #ifdef CONFIG_DYNAMIC_FTRACE
 
+static int patch_text_remap = 0;
+
 static int __ftrace_modify_code(void *data)
 {
 	int *command = data;
 
-	set_kernel_text_rw();
+	patch_text_remap++;
 	ftrace_modify_all_code(*command);
-	set_kernel_text_ro();
+	patch_text_remap--;
 
 	return 0;
 }
@@ -59,13 +62,13 @@ static unsigned long adjust_address(stru
 
 int ftrace_arch_code_modify_prepare(void)
 {
-	set_all_modules_text_rw();
+	patch_text_remap++;
 	return 0;
 }
 
 int ftrace_arch_code_modify_post_process(void)
 {
-	set_all_modules_text_ro();
+	patch_text_remap--;
 	/* Make sure any TLB misses during machine stop are cleared. */
 	flush_tlb_all();
 	return 0;
@@ -97,10 +100,7 @@ static int ftrace_modify_code(unsigned l
 			return -EINVAL;
 	}
 
-	if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
-		return -EPERM;
-
-	flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
+	__patch_text_real((void *)pc, new, patch_text_remap);
 
 	return 0;
 }