Revert "ARM: allow the kernel text section to be made read-only"tracking-ll-misc-fixes-13.03-ll-20130327.1

This reverts commit 5e9c31627e22f20dc2b9ee14f3a9f0a58d2792aa.

7 files changed, 22 insertions, 289 deletions

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index d04aabae022c..ecfcdba2d17c 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -63,27 +63,6 @@ config DEBUG_USER
 	      8 - SIGSEGV faults
 	     16 - SIGBUS faults
 
-config DEBUG_RODATA
-	bool "Write protect kernel text section"
-	default n
-	depends on DEBUG_KERNEL && MMU
-	---help---
-	  Mark the kernel text section as write-protected in the pagetables,
-	  in order to catch accidental (and incorrect) writes to such const
-	  data. This will cause the size of the kernel, plus up to 4MB, to
-	  be mapped as pages instead of sections, which will increase TLB
-	  pressure.
-	  If in doubt, say "N".
-
-config DEBUG_RODATA_TEST
-	bool "Testcase for the DEBUG_RODATA feature"
-	depends on DEBUG_RODATA
-	default n
-	---help---
-	  This option enables a testcase for the DEBUG_RODATA
-	  feature.
-	  If in doubt, say "N"
-
 # These options are only for real kernel hackers who want to get their hands dirty.
 config DEBUG_LL
 	bool "Kernel low-level debugging functions (read help!)"
diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index 4e8217b204af..e1489c54cd12 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -16,7 +16,6 @@
 #include <asm/shmparam.h>
 #include <asm/cachetype.h>
 #include <asm/outercache.h>
-#include <asm/rodata.h>
 
 #define CACHE_COLOUR(vaddr)	((vaddr & (SHMLBA - 1)) >> PAGE_SHIFT)
 
diff --git a/arch/arm/include/asm/rodata.h b/arch/arm/include/asm/rodata.h
deleted file mode 100644
index 8c8add87bbc5..000000000000
--- a/arch/arm/include/asm/rodata.h
+++ /dev/null
@@ -1,32 +0,0 @@
-/*
- *  arch/arm/include/asm/rodata.h
- *
- *  Copyright (C) 2011 Google, Inc.
- *
- *  Author: Colin Cross <ccross@android.com>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-#ifndef _ASMARM_RODATA_H
-#define _ASMARM_RODATA_H
-
-#ifndef __ASSEMBLY__
-
-#ifdef CONFIG_DEBUG_RODATA
-
-int set_memory_rw(unsigned long virt, int numpages);
-int set_memory_ro(unsigned long virt, int numpages);
-
-void mark_rodata_ro(void);
-void set_kernel_text_rw(void);
-void set_kernel_text_ro(void);
-#else
-static inline void set_kernel_text_rw(void) { }
-static inline void set_kernel_text_ro(void) { }
-#endif
-
-#endif
-
-#endif
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 6a740a93f4bb..34e56647dcee 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -13,7 +13,6 @@
  */
 
 #include <linux/ftrace.h>
-#include <linux/module.h>
 #include <linux/uaccess.h>
 
 #include <asm/cacheflush.h>
@@ -64,20 +63,6 @@ static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
 }
 #endif
 
-int ftrace_arch_code_modify_prepare(void)
-{
-	set_kernel_text_rw();
-	set_all_modules_text_rw();
-	return 0;
-}
-
-int ftrace_arch_code_modify_post_process(void)
-{
-	set_all_modules_text_ro();
-	set_kernel_text_ro();
-	return 0;
-}
-
 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
 {
 	return arm_gen_branch_link(pc, addr);
diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile
index 1624c079e527..a30642ee93e5 100644
--- a/arch/arm/mm/Makefile
+++ b/arch/arm/mm/Makefile
@@ -7,7 +7,6 @@ obj-y				:= dma-mapping.o extable.o fault.o init.o \
 
 obj-$(CONFIG_MMU)		+= fault-armv.o flush.o idmap.o ioremap.o \
 				   mmap.o pgd.o mmu.o
-obj-$(CONFIG_DEBUG_RODATA)	+= rodata.o
 
 ifneq ($(CONFIG_MMU),y)
 obj-y				+= nommu.o
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index a7083bf19726..be7bc434561b 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -604,25 +604,11 @@ static void __init *early_alloc(unsigned long sz)
 	return early_alloc_aligned(sz, sz);
 }
 
-static pte_t * __init early_pte_alloc(pmd_t *pmd)
-{
-	if (pmd_none(*pmd) || pmd_bad(*pmd))
-		return early_alloc(PTE_HWTABLE_OFF + PTE_HWTABLE_SIZE);
-	return pmd_page_vaddr(*pmd);
-}
-
-static void __init early_pte_install(pmd_t *pmd, pte_t *pte, unsigned long prot)
-{
-	__pmd_populate(pmd, __pa(pte), prot);
-	BUG_ON(pmd_bad(*pmd));
-}
-
-static pte_t * __init early_pte_alloc_and_install(pmd_t *pmd,
-	unsigned long addr, unsigned long prot)
+static pte_t * __init early_pte_alloc(pmd_t *pmd, unsigned long addr, unsigned long prot)
 {
 	if (pmd_none(*pmd)) {
-		pte_t *pte = early_pte_alloc(pmd);
-		early_pte_install(pmd, pte, prot);
+		pte_t *pte = early_alloc(PTE_HWTABLE_OFF + PTE_HWTABLE_SIZE);
+		__pmd_populate(pmd, __pa(pte), prot);
 	}
 	BUG_ON(pmd_bad(*pmd));
 	return pte_offset_kernel(pmd, addr);
@@ -632,23 +618,16 @@ static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr,
 				  unsigned long end, unsigned long pfn,
 				  const struct mem_type *type)
 {
-	pte_t *start_pte = early_pte_alloc(pmd);
-	pte_t *pte = start_pte + pte_index(addr);
-
-	/* If replacing a section mapping, the whole section must be replaced */
-	BUG_ON(pmd_bad(*pmd) && ((addr | end) & ~PMD_MASK));
-
+	pte_t *pte = early_pte_alloc(pmd, addr, type->prot_l1);
 	do {
 		set_pte_ext(pte, pfn_pte(pfn, __pgprot(type->prot_pte)), 0);
 		pfn++;
 	} while (pte++, addr += PAGE_SIZE, addr != end);
-	early_pte_install(pmd, start_pte, type->prot_l1);
 }
 
 static void __init alloc_init_section(pud_t *pud, unsigned long addr,
 				      unsigned long end, phys_addr_t phys,
-				      const struct mem_type *type,
-				      bool force_pages)
+				      const struct mem_type *type)
 {
 	pmd_t *pmd = pmd_offset(pud, addr);
 
@@ -658,8 +637,7 @@ static void __init alloc_init_section(pud_t *pud, unsigned long addr,
 	 * L1 entries, whereas PGDs refer to a group of L1 entries making
 	 * up one logical pointer to an L2 table.
 	 */
-	if (type->prot_sect && ((addr | end | phys) & ~SECTION_MASK) == 0 &&
-	    !force_pages) {
+	if (type->prot_sect && ((addr | end | phys) & ~SECTION_MASK) == 0) {
 		pmd_t *p = pmd;
 
 #ifndef CONFIG_ARM_LPAE
@@ -683,15 +661,14 @@ static void __init alloc_init_section(pud_t *pud, unsigned long addr,
 }
 
 static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
-	unsigned long end, unsigned long phys, const struct mem_type *type,
-	bool force_pages)
+	unsigned long end, unsigned long phys, const struct mem_type *type)
 {
 	pud_t *pud = pud_offset(pgd, addr);
 	unsigned long next;
 
 	do {
 		next = pud_addr_end(addr, end);
-		alloc_init_section(pud, addr, next, phys, type, force_pages);
+		alloc_init_section(pud, addr, next, phys, type);
 		phys += next - addr;
 	} while (pud++, addr = next, addr != end);
 }
@@ -765,7 +742,7 @@ static void __init create_36bit_mapping(struct map_desc *md,
  * offsets, and we take full advantage of sections and
  * supersections.
  */
-static void __init create_mapping(struct map_desc *md, bool force_pages)
+static void __init create_mapping(struct map_desc *md)
 {
 	unsigned long addr, length, end;
 	phys_addr_t phys;
@@ -815,7 +792,7 @@ static void __init create_mapping(struct map_desc *md, bool force_pages)
 	do {
 		unsigned long next = pgd_addr_end(addr, end);
 
-		alloc_init_pud(pgd, addr, next, phys, type, force_pages);
+		alloc_init_pud(pgd, addr, next, phys, type);
 
 		phys += next - addr;
 		addr = next;
@@ -837,7 +814,7 @@ void __init iotable_init(struct map_desc *io_desc, int nr)
 	svm = early_alloc_aligned(sizeof(*svm) * nr, __alignof__(*svm));
 
 	for (md = io_desc; nr; md++, nr--) {
-		create_mapping(md, false);
+		create_mapping(md);
 
 		vm = &svm->vm;
 		vm->addr = (void *)(md->virtual & PAGE_MASK);
@@ -958,7 +935,7 @@ void __init debug_ll_io_init(void)
 	map.virtual &= PAGE_MASK;
 	map.length = PAGE_SIZE;
 	map.type = MT_DEVICE;
-	create_mapping(&map, false);
+	create_mapping(&map);
 }
 #endif
 
@@ -1222,7 +1199,7 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
 	map.virtual = MODULES_VADDR;
 	map.length = ((unsigned long)_etext - map.virtual + ~SECTION_MASK) & SECTION_MASK;
 	map.type = MT_ROM;
-	create_mapping(&map, false);
+	create_mapping(&map);
 #endif
 
 	/*
@@ -1233,14 +1210,14 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
 	map.virtual = FLUSH_BASE;
 	map.length = SZ_1M;
 	map.type = MT_CACHECLEAN;
-	create_mapping(&map, false);
+	create_mapping(&map);
 #endif
 #ifdef FLUSH_BASE_MINICACHE
 	map.pfn = __phys_to_pfn(FLUSH_BASE_PHYS + SZ_1M);
 	map.virtual = FLUSH_BASE_MINICACHE;
 	map.length = SZ_1M;
 	map.type = MT_MINICLEAN;
-	create_mapping(&map, false);
+	create_mapping(&map);
 #endif
 
 	/*
@@ -1252,12 +1229,12 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
 	map.virtual = 0xffff0000;
 	map.length = PAGE_SIZE;
 	map.type = MT_HIGH_VECTORS;
-	create_mapping(&map, false);
+	create_mapping(&map);
 
 	if (!vectors_high()) {
 		map.virtual = 0;
 		map.type = MT_LOW_VECTORS;
-		create_mapping(&map, false);
+		create_mapping(&map);
 	}
 
 	/*
@@ -1283,23 +1260,20 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
 static void __init kmap_init(void)
 {
 #ifdef CONFIG_HIGHMEM
-	pkmap_page_table = early_pte_alloc_and_install(pmd_off_k(PKMAP_BASE),
+	pkmap_page_table = early_pte_alloc(pmd_off_k(PKMAP_BASE),
 		PKMAP_BASE, _PAGE_KERNEL_TABLE);
 #endif
 }
 
-
 static void __init map_lowmem(void)
 {
 	struct memblock_region *reg;
-	phys_addr_t start;
-	phys_addr_t end;
-	struct map_desc map;
 
 	/* Map all the lowmem memory banks. */
 	for_each_memblock(memory, reg) {
-		start = reg->base;
-		end = start + reg->size;
+		phys_addr_t start = reg->base;
+		phys_addr_t end = start + reg->size;
+		struct map_desc map;
 
 		if (end > arm_lowmem_limit)
 			end = arm_lowmem_limit;
@@ -1311,20 +1285,8 @@ static void __init map_lowmem(void)
 		map.length = end - start;
 		map.type = MT_MEMORY;
 
-		create_mapping(&map, false);
+		create_mapping(&map);
 	}
-
-#ifdef CONFIG_DEBUG_RODATA
-	start = __pa(_stext) & PMD_MASK;
-	end = ALIGN(__pa(__end_rodata), PMD_SIZE);
-
-	map.pfn = __phys_to_pfn(start);
-	map.virtual = __phys_to_virt(start);
-	map.length = end - start;
-	map.type = MT_MEMORY;
-
-	create_mapping(&map, true);
-#endif
 }
 
 /*
diff --git a/arch/arm/mm/rodata.c b/arch/arm/mm/rodata.c
deleted file mode 100644
index 9a8eb841c428..000000000000
--- a/arch/arm/mm/rodata.c
+++ /dev/null
@@ -1,159 +0,0 @@
-/*
- *  linux/arch/arm/mm/rodata.c
- *
- *  Copyright (C) 2011 Google, Inc.
- *
- *  Author: Colin Cross <ccross@android.com>
- *
- *  Based on x86 implementation in arch/x86/mm/init_32.c
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- */
-
-#include <linux/kernel.h>
-#include <linux/mm.h>
-#include <linux/module.h>
-
-#include <asm/cache.h>
-#include <asm/pgtable.h>
-#include <asm/rodata.h>
-#include <asm/sections.h>
-#include <asm/tlbflush.h>
-
-#include "mm.h"
-
-static int kernel_set_to_readonly __read_mostly;
-
-#ifdef CONFIG_DEBUG_RODATA_TEST
-static const int rodata_test_data = 0xC3;
-
-static noinline void rodata_test(void)
-{
-	int result;
-
-	pr_info("%s: attempting to write to read-only section:\n", __func__);
-
-	if (*(volatile int *)&rodata_test_data != 0xC3) {
-		pr_err("read only data changed before test\n");
-		return;
-	}
-
-	/*
-	 * Attempt to to write to rodata_test_data, trapping the expected
-	 * data abort.  If the trap executed, result will be 1.  If it didn't,
-	 * result will be 0xFF.
-	 */
-	asm volatile(
-		"0:	str	%[zero], [%[rodata_test_data]]\n"
-		"	mov	%[result], #0xFF\n"
-		"	b	2f\n"
-		"1:	mov	%[result], #1\n"
-		"2:\n"
-
-		/* Exception fixup - if store at label 0 faults, jumps to 1 */
-		".pushsection __ex_table, \"a\"\n"
-		"	.long	0b, 1b\n"
-		".popsection\n"
-
-		: [result] "=r" (result)
-		: [rodata_test_data] "r" (&rodata_test_data), [zero] "r" (0)
-		: "memory"
-	);
-
-	if (result == 1)
-		pr_info("write to read-only section trapped, success\n");
-	else
-		pr_err("write to read-only section NOT trapped, test failed\n");
-
-	if (*(volatile int *)&rodata_test_data != 0xC3)
-		pr_err("read only data changed during write\n");
-}
-#else
-static inline void rodata_test(void) { }
-#endif
-
-static int set_page_attributes(unsigned long virt, int numpages,
-	pte_t (*f)(pte_t))
-{
-	pmd_t *pmd;
-	pte_t *pte;
-	unsigned long start = virt;
-	unsigned long end = virt + (numpages << PAGE_SHIFT);
-	unsigned long pmd_end;
-
-	while (virt < end) {
-		pmd = pmd_off_k(virt);
-		pmd_end = min(ALIGN(virt + 1, PMD_SIZE), end);
-
-		if ((pmd_val(*pmd) & PMD_TYPE_MASK) != PMD_TYPE_TABLE) {
-			pr_err("%s: pmd %p=%08lx for %08lx not page table\n",
-				__func__, pmd, pmd_val(*pmd), virt);
-			virt = pmd_end;
-			continue;
-		}
-
-		while (virt < pmd_end) {
-			pte = pte_offset_kernel(pmd, virt);
-			set_pte_ext(pte, f(*pte), 0);
-			virt += PAGE_SIZE;
-		}
-	}
-
-	flush_tlb_kernel_range(start, end);
-
-	return 0;
-}
-
-int set_memory_ro(unsigned long virt, int numpages)
-{
-	return set_page_attributes(virt, numpages, pte_wrprotect);
-}
-EXPORT_SYMBOL(set_memory_ro);
-
-int set_memory_rw(unsigned long virt, int numpages)
-{
-	return set_page_attributes(virt, numpages, pte_mkwrite);
-}
-EXPORT_SYMBOL(set_memory_rw);
-
-void set_kernel_text_rw(void)
-{
-	unsigned long start = PAGE_ALIGN((unsigned long)_text);
-	unsigned long size = PAGE_ALIGN((unsigned long)__end_rodata) - start;
-
-	if (!kernel_set_to_readonly)
-		return;
-
-	pr_debug("Set kernel text: %lx - %lx to read-write\n",
-		 start, start + size);
-
-	set_memory_rw(start, size >> PAGE_SHIFT);
-}
-
-void set_kernel_text_ro(void)
-{
-	unsigned long start = PAGE_ALIGN((unsigned long)_text);
-	unsigned long size = PAGE_ALIGN((unsigned long)__end_rodata) - start;
-
-	if (!kernel_set_to_readonly)
-		return;
-
-	pr_info_once("Write protecting the kernel text section %lx - %lx\n",
-		start, start + size);
-
-	pr_debug("Set kernel text: %lx - %lx to read only\n",
-		 start, start + size);
-
-	set_memory_ro(start, size >> PAGE_SHIFT);
-}
-
-void mark_rodata_ro(void)
-{
-	kernel_set_to_readonly = 1;
-
-	set_kernel_text_ro();
-
-	rodata_test();
-}