powerpc: Enable KFENCE for PPC32

Add architecture specific implementation details for KFENCE and enable
KFENCE for the ppc32 architecture. In particular, this implements the
required interface in <asm/kfence.h>.

KFENCE requires that attributes for pages from its memory pool can
individually be set. Therefore, force the Read/Write linear map to be
mapped at page granularity.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/8dfe1bd2abde26337c1d8c1ad0acfcc82185e0d5.1614868445.git.christophe.leroy@csgroup.eu

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 386ae12d8523b4af1aa20dd7237d6e7c57d202ab..d46db0bfb99878f26599f9c712251867bdb75d9b 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -185,6 +185,7 @@ config PPC
        select HAVE_ARCH_KASAN                  if PPC32 && PPC_PAGE_SHIFT <= 14
        select HAVE_ARCH_KASAN_VMALLOC          if PPC32 && PPC_PAGE_SHIFT <= 14
        select HAVE_ARCH_KGDB
+       select HAVE_ARCH_KFENCE                 if PPC32
        select HAVE_ARCH_MMAP_RND_BITS
        select HAVE_ARCH_MMAP_RND_COMPAT_BITS   if COMPAT
        select HAVE_ARCH_NVRAM_OPS
@@ -786,7 +787,7 @@ config THREAD_SHIFT
 config DATA_SHIFT_BOOL
        bool "Set custom data alignment"
        depends on ADVANCED_OPTIONS
-       depends on STRICT_KERNEL_RWX || DEBUG_PAGEALLOC
+       depends on STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE
        depends on PPC_BOOK3S_32 || (PPC_8xx && !PIN_TLB_DATA && !STRICT_KERNEL_RWX)
        help
          This option allows you to set the kernel data alignment. When
@@ -798,13 +799,13 @@ config DATA_SHIFT_BOOL
 config DATA_SHIFT
        int "Data shift" if DATA_SHIFT_BOOL
        default 24 if STRICT_KERNEL_RWX && PPC64
-       range 17 28 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC) && PPC_BOOK3S_32
-       range 19 23 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC) && PPC_8xx
+       range 17 28 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) && PPC_BOOK3S_32
+       range 19 23 if (STRICT_KERNEL_RWX || DEBUG_PAGEALLOC || KFENCE) && PPC_8xx
        default 22 if STRICT_KERNEL_RWX && PPC_BOOK3S_32
-       default 18 if DEBUG_PAGEALLOC && PPC_BOOK3S_32
+       default 18 if (DEBUG_PAGEALLOC || KFENCE) && PPC_BOOK3S_32
        default 23 if STRICT_KERNEL_RWX && PPC_8xx
-       default 23 if DEBUG_PAGEALLOC && PPC_8xx && PIN_TLB_DATA
-       default 19 if DEBUG_PAGEALLOC && PPC_8xx
+       default 23 if (DEBUG_PAGEALLOC || KFENCE) && PPC_8xx && PIN_TLB_DATA
+       default 19 if (DEBUG_PAGEALLOC || KFENCE) && PPC_8xx
        default PPC_PAGE_SHIFT
        help
          On Book3S 32 (603+), DBATs are used to map kernel text and rodata RO.

diff --git a/arch/powerpc/include/asm/kfence.h b/arch/powerpc/include/asm/kfence.h
new file mode 100644 (file)
index 0000000..a9846b6
--- /dev/null
+++ b/arch/powerpc/include/asm/kfence.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * powerpc KFENCE support.
+ *
+ * Copyright (C) 2020 CS GROUP France
+ */
+
+#ifndef __ASM_POWERPC_KFENCE_H
+#define __ASM_POWERPC_KFENCE_H
+
+#include <linux/mm.h>
+#include <asm/pgtable.h>
+
+static inline bool arch_kfence_init_pool(void)
+{
+       return true;
+}
+
+static inline bool kfence_protect_page(unsigned long addr, bool protect)
+{
+       pte_t *kpte = virt_to_kpte(addr);
+
+       if (protect) {
+               pte_update(&init_mm, addr, kpte, _PAGE_PRESENT, 0, 0);
+               flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
+       } else {
+               pte_update(&init_mm, addr, kpte, 0, _PAGE_PRESENT, 0);
+       }
+
+       return true;
+}
+
+#endif /* __ASM_POWERPC_KFENCE_H */

diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
index d7eb266a3f7ad83840229cc4bfd95810ec1d4550..a0db398b5c265879a019178b8b63c458ff5fb02c 100644 (file)
--- a/arch/powerpc/mm/book3s32/mmu.c
+++ b/arch/powerpc/mm/book3s32/mmu.c
@@ -162,7 +162,7 @@ unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)
        unsigned long border = (unsigned long)__init_begin - PAGE_OFFSET;
 
 
-       if (debug_pagealloc_enabled() || __map_without_bats) {
+       if (debug_pagealloc_enabled_or_kfence() || __map_without_bats) {
                pr_debug_once("Read-Write memory mapped without BATs\n");
                if (base >= border)
                        return base;

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index bb368257b55cb432eedc1486c2ab0b60f2fc1e90..bea13682c9092aecb4c7b2ae6490d1ed8ad60f1d 100644 (file)
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -32,6 +32,7 @@
 #include <linux/context_tracking.h>
 #include <linux/hugetlb.h>
 #include <linux/uaccess.h>
+#include <linux/kfence.h>
 
 #include <asm/firmware.h>
 #include <asm/interrupt.h>
@@ -418,8 +419,12 @@ static int ___do_page_fault(struct pt_regs *regs, unsigned long address,
         * take a page fault to a kernel address or a page fault to a user
         * address outside of dedicated places
         */
-       if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write)))
+       if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write))) {
+               if (kfence_handle_page_fault(address, is_write, regs))
+                       return 0;
+
                return SIGSEGV;
+       }
 
        /*
         * If we're in an interrupt, have no user context or are running

diff --git a/arch/powerpc/mm/init_32.c b/arch/powerpc/mm/init_32.c
index 02c7db4087cbc764086f3453f113b908a035c362..3d690be48e845e303f448e4da8d03ecb7d251321 100644 (file)
--- a/arch/powerpc/mm/init_32.c
+++ b/arch/powerpc/mm/init_32.c
@@ -97,6 +97,9 @@ static void __init MMU_setup(void)
        if (IS_ENABLED(CONFIG_PPC_8xx))
                return;
 
+       if (IS_ENABLED(CONFIG_KFENCE))
+               __map_without_ltlbs = 1;
+
        if (debug_pagealloc_enabled())
                __map_without_ltlbs = 1;
 

diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index 998810e685620dbeffe84b6ca2dc2c49a5fe3019..7dac910c0b217fcfc8b4f3f091d0006adab02778 100644 (file)
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -185,3 +185,8 @@ void ptdump_check_wx(void);
 #else
 static inline void ptdump_check_wx(void) { }
 #endif
+
+static inline bool debug_pagealloc_enabled_or_kfence(void)
+{
+       return IS_ENABLED(CONFIG_KFENCE) || debug_pagealloc_enabled();
+}

diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
index 19a3eec1d8c52b026ee79ce0a47e1b5cb70f5d6f..71bfdbedacee81af869887f8d5329f7a35e2b099 100644 (file)
--- a/arch/powerpc/mm/nohash/8xx.c
+++ b/arch/powerpc/mm/nohash/8xx.c
@@ -149,7 +149,7 @@ unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)
 {
        unsigned long etext8 = ALIGN(__pa(_etext), SZ_8M);
        unsigned long sinittext = __pa(_sinittext);
-       bool strict_boundary = strict_kernel_rwx_enabled() || debug_pagealloc_enabled();
+       bool strict_boundary = strict_kernel_rwx_enabled() || debug_pagealloc_enabled_or_kfence();
        unsigned long boundary = strict_boundary ? sinittext : etext8;
        unsigned long einittext8 = ALIGN(__pa(_einittext), SZ_8M);
 
@@ -161,7 +161,7 @@ unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)
                return 0;
 
        mmu_mapin_ram_chunk(0, boundary, PAGE_KERNEL_TEXT, true);
-       if (debug_pagealloc_enabled()) {
+       if (debug_pagealloc_enabled_or_kfence()) {
                top = boundary;
        } else {
                mmu_mapin_ram_chunk(boundary, einittext8, PAGE_KERNEL_TEXT, true);