From: Christophe Leroy <christophe.leroy@c-s.fr>
Date: Wed, 2 Aug 2017 13:51:05 +0000 (+0200)
Subject: powerpc/mm: Implement STRICT_KERNEL_RWX on PPC32
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=95902e6c8864d39b09134dcaa3c99d8161d1deea;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

powerpc/mm: Implement STRICT_KERNEL_RWX on PPC32

This patch implements STRICT_KERNEL_RWX on PPC32.

As for CONFIG_DEBUG_PAGEALLOC, it deactivates BAT and LTLB mappings
in order to allow page protection setup at the level of each page.

As BAT/LTLB mappings are deactivated, there might be a performance
impact.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index a2b669729440..bf6abab46dcc 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -176,7 +176,7 @@ config PPC
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS	if COMPAT
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
-	select ARCH_HAS_STRICT_KERNEL_RWX	if (PPC_BOOK3S_64 && !RELOCATABLE && !HIBERNATION)
+	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
 	select ARCH_OPTIONAL_KERNEL_RWX		if ARCH_HAS_STRICT_KERNEL_RWX
 	select HAVE_CBPF_JIT			if !PPC64
 	select HAVE_CONTEXT_TRACKING		if PPC64
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index b1a250560198..882628fa6987 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -8,7 +8,7 @@
 #include <asm/cache.h>
 #include <asm/thread_info.h>
 
-#ifdef CONFIG_STRICT_KERNEL_RWX
+#if defined(CONFIG_STRICT_KERNEL_RWX) && !defined(CONFIG_PPC32)
 #define STRICT_ALIGN_SIZE	(1 << 24)
 #else
 #define STRICT_ALIGN_SIZE	PAGE_SIZE
diff --git a/arch/powerpc/mm/init_32.c b/arch/powerpc/mm/init_32.c
index 8a7c38b8d335..7d5fee1bb116 100644
--- a/arch/powerpc/mm/init_32.c
+++ b/arch/powerpc/mm/init_32.c
@@ -113,6 +113,12 @@ void __init MMU_setup(void)
 		__map_without_bats = 1;
 		__map_without_ltlbs = 1;
 	}
+#ifdef CONFIG_STRICT_KERNEL_RWX
+	if (rodata_enabled) {
+		__map_without_bats = 1;
+		__map_without_ltlbs = 1;
+	}
+#endif
 }
 
 /*
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 85e8f0e0efe6..4a3dd9fc6989 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -34,6 +34,7 @@
 #include <asm/fixmap.h>
 #include <asm/io.h>
 #include <asm/setup.h>
+#include <asm/sections.h>
 
 #include "mmu_decl.h"
 
@@ -375,6 +376,29 @@ void mark_initmem_nx(void)
 	change_page_attr(page, numpages, PAGE_KERNEL);
 }
 
+#ifdef CONFIG_STRICT_KERNEL_RWX
+void mark_rodata_ro(void)
+{
+	struct page *page;
+	unsigned long numpages;
+
+	page = virt_to_page(_stext);
+	numpages = PFN_UP((unsigned long)_etext) -
+		   PFN_DOWN((unsigned long)_stext);
+
+	change_page_attr(page, numpages, PAGE_KERNEL_ROX);
+	/*
+	 * mark .rodata as read only. Use __init_begin rather than __end_rodata
+	 * to cover NOTES and EXCEPTION_TABLE.
+	 */
+	page = virt_to_page(__start_rodata);
+	numpages = PFN_UP((unsigned long)__init_begin) -
+		   PFN_DOWN((unsigned long)__start_rodata);
+
+	change_page_attr(page, numpages, PAGE_KERNEL_RO);
+}
+#endif
+
 #ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {