From 91d92b8e241835013cefaca0c5121b9d6df9d500 Mon Sep 17 00:00:00 2001
From: Rabin Vincent <rabin@rab.in>
Date: Wed, 2 Apr 2014 00:57:09 +0200
Subject: [PATCH] ftrace

---
 arch/arm/kernel/ftrace.c | 21 +++++++++++++
 arch/arm/mm/init.c       | 77 ++++++++++++++++++++++++++++++++++--------------
 2 files changed, 76 insertions(+), 22 deletions(-)

diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 34e5664..61cb8ef 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -14,6 +14,7 @@
 
 #include <linux/ftrace.h>
 #include <linux/uaccess.h>
+#include <linux/stop_machine.h>
 
 #include <asm/cacheflush.h>
 #include <asm/opcodes.h>
@@ -34,6 +35,26 @@
 
 #define	OLD_NOP		0xe1a00000	/* mov r0, r0 */
 
+static int __ftrace_modify_code(void *data)
+{
+	extern void set_kernel_text_rw(struct mm_struct *mm);
+	extern void set_kernel_text_ro(struct mm_struct *mm);
+
+	struct mm_struct *mm = current->active_mm;
+	int *command = data;
+
+	set_kernel_text_rw(mm);
+	ftrace_modify_all_code(*command);
+	set_kernel_text_ro(mm);
+
+	return 0;
+}
+
+void arch_ftrace_update_code(int command)
+{
+	stop_machine(__ftrace_modify_code, &command, NULL);
+}
+
 static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
 {
 	return rec->arch.old_mcount ? OLD_NOP : NOP;
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 5b1b049..c4da92d 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -630,22 +630,24 @@ void __init mem_init(void)
 struct section_perm {
 	unsigned long start;
 	unsigned long end;
+	pmdval_t mask;
 	pmdval_t prot;
+	pmdval_t clear;
 };
 
-struct section_perm __initdata section_perms[] = {
+struct section_perm section_perms[] = {
 	/* Make pages tables, etc before _stext RW (set NX). */
-	{
-		.start	= PAGE_OFFSET,
-		.end	= (unsigned long)_stext,
-		.prot	= PMD_SECT_XN,
-	},
-	/* Make init RW (set NX). */
-	{
-		.start	= (unsigned long)__init_begin,
-		.end	= (unsigned long)_sdata,
-		.prot	= PMD_SECT_XN,
-	},
+	// {
+	// 	.start	= PAGE_OFFSET,
+	// 	.end	= (unsigned long)_stext,
+	// 	.prot	= PMD_SECT_XN,
+	// },
+	// /* Make init RW (set NX). */
+	// {
+	// 	.start	= (unsigned long)__init_begin,
+	// 	.end	= (unsigned long)_sdata,
+	// 	.prot	= PMD_SECT_XN,
+	// },
 	/* Make kernel code and rodata RX (set RO). */
 	{
 		.start	= (unsigned long)_stext,
@@ -653,30 +655,37 @@ struct section_perm __initdata section_perms[] = {
 #ifdef CONFIG_ARM_LPAE
 		.prot	= PMD_SECT_RDONLY,
 #else
+		.mask       = ~(PMD_SECT_APX | PMD_SECT_AP_WRITE),
 		.prot	= PMD_SECT_APX | PMD_SECT_AP_WRITE,
+		.clear       = PMD_SECT_AP_WRITE,
 #endif
 	},
 #ifdef CONFIG_DEBUG_RODATA
 	/* Make rodata RO (set NX). */
-	{
-		.start	= (unsigned long)__start_rodata,
-		.end	= (unsigned long)__init_begin,
-		.prot	= PMD_SECT_XN,
-	}
+	// {
+	// 	.start	= (unsigned long)__start_rodata,
+	// 	.end	= (unsigned long)__init_begin,
+	// 	.prot	= PMD_SECT_XN,
+	// }
 #endif
 };
 
-static inline void section_update(unsigned long addr, pmdval_t prot)
+static inline pmd_t *pmd_off(struct mm_struct *mm, unsigned long virt)
+{
+	return pmd_offset(pud_offset(pgd_offset(mm, virt), virt), virt);
+}
+
+static inline void section_update(struct mm_struct *mm, unsigned long addr, pmdval_t mask, pmdval_t prot)
 {
-	pmd_t *pmd = pmd_off_k(addr);
+	pmd_t *pmd = pmd_off(mm, addr);
 
 #ifdef CONFIG_ARM_LPAE
 	pmd[0] = __pmd(pmd_val(pmd[0]) | prot);
 #else
 	if (addr & SECTION_SIZE)
-		pmd[1] = __pmd(pmd_val(pmd[1]) | prot);
+		pmd[1] = __pmd((pmd_val(pmd[1]) & mask) | prot);
 	else
-		pmd[0] = __pmd(pmd_val(pmd[0]) | prot);
+		pmd[0] = __pmd((pmd_val(pmd[0]) & mask) | prot);
 #endif
 	flush_pmd_entry(pmd);
 }
@@ -702,13 +711,37 @@ static inline void fix_kernmem_perms(void)
 		for (addr = section_perms[i].start;
 		     addr < section_perms[i].end;
 		     addr += SECTION_SIZE)
-			section_update(addr, section_perms[i].prot);
+			section_update(&init_mm, addr, section_perms[i].mask, section_perms[i].prot);
 	}
 }
 #else
 static inline void fix_kernmem_perms(void) { }
 #endif /* CONFIG_ARM_KERNMEM_PERMS */
 
+void set_kernel_text_rw(struct mm_struct *mm)
+{
+       unsigned long addr;
+
+       for (addr = section_perms[0].start;
+            addr < section_perms[0].end;
+            addr += SECTION_SIZE)
+              section_update(mm, addr, section_perms[0].mask,
+                            section_perms[0].clear);
+
+       flush_tlb_all();
+}
+
+void set_kernel_text_ro(struct mm_struct *mm)
+{
+       unsigned long addr;
+
+       for (addr = section_perms[0].start;
+            addr < section_perms[0].end;
+            addr += SECTION_SIZE)
+              section_update(mm, addr, section_perms[0].mask,
+                            section_perms[0].prot);
+}
+
 void free_initmem(void)
 {
 #ifdef CONFIG_HAVE_TCM
-- 
1.9.0