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[159.196.117.139]) by smtp.gmail.com with ESMTPSA id k12sm454490pgh.16.2021.05.05.19.38.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 May 2021 19:38:37 -0700 (PDT) From: Jordan Niethe To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH v12 1/8] powerpc/mm: Implement set_memory() routines Date: Thu, 6 May 2021 12:34:42 +1000 Message-Id: <20210506023449.3568630-2-jniethe5@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210506023449.3568630-1-jniethe5@gmail.com> References: <20210506023449.3568630-1-jniethe5@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ajd@linux.ibm.com, cmr@codefail.de, npiggin@gmail.com, aneesh.kumar@linux.ibm.com, naveen.n.rao@linux.ibm.com, Jordan Niethe , dja@axtens.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: Russell Currey The set_memory_{ro/rw/nx/x}() functions are required for STRICT_MODULE_RWX, and are generally useful primitives to have. This implementation is designed to be generic across powerpc's many MMUs. It's possible that this could be optimised to be faster for specific MMUs. This implementation does not handle cases where the caller is attempting to change the mapping of the page it is executing from, or if another CPU is concurrently using the page being altered. These cases likely shouldn't happen, but a more complex implementation with MMU-specific code could safely handle them. On hash, the linear mapping is not kept in the linux pagetable, so this will not change the protection if used on that range. Currently these functions are not used on the linear map so just WARN for now. apply_to_existing_page_range() does not work on huge pages so for now disallow changing the protection of huge pages. Reviewed-by: Daniel Axtens Signed-off-by: Russell Currey Signed-off-by: Christophe Leroy [jpn: - Allow set memory functions to be used without Strict RWX - Hash: Disallow certain regions - Have change_page_attr() take function pointers to manipulate ptes - Radix: Add ptesync after set_pte_at()] Signed-off-by: Jordan Niethe --- v10: WARN if trying to change the hash linear map v11: - Update copywrite dates - Allow set memory functions to be used without Strict RWX - Hash: Disallow certain regions and add comment explaining why - Have change_page_attr() take function pointers to manipulate ptes - Clarify change_page_attr()'s comment - Radix: Add ptesync after set_pte_at() v12: - change_page_attr() back to taking an action value - disallow operating on huge pages --- arch/powerpc/Kconfig | 1 + arch/powerpc/include/asm/set_memory.h | 32 +++++++++ arch/powerpc/mm/Makefile | 2 +- arch/powerpc/mm/pageattr.c | 100 ++++++++++++++++++++++++++ 4 files changed, 134 insertions(+), 1 deletion(-) create mode 100644 arch/powerpc/include/asm/set_memory.h create mode 100644 arch/powerpc/mm/pageattr.c diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 3f863dd21374..cce0a137b046 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -138,6 +138,7 @@ config PPC select ARCH_HAS_MEMBARRIER_CALLBACKS select ARCH_HAS_MEMBARRIER_SYNC_CORE select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64 + select ARCH_HAS_SET_MEMORY select ARCH_HAS_STRICT_KERNEL_RWX if ((PPC_BOOK3S_64 || PPC32) && !HIBERNATION) select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST select ARCH_HAS_UACCESS_FLUSHCACHE diff --git a/arch/powerpc/include/asm/set_memory.h b/arch/powerpc/include/asm/set_memory.h new file mode 100644 index 000000000000..64011ea444b4 --- /dev/null +++ b/arch/powerpc/include/asm/set_memory.h @@ -0,0 +1,32 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_POWERPC_SET_MEMORY_H +#define _ASM_POWERPC_SET_MEMORY_H + +#define SET_MEMORY_RO 0 +#define SET_MEMORY_RW 1 +#define SET_MEMORY_NX 2 +#define SET_MEMORY_X 3 + +int change_memory_attr(unsigned long addr, int numpages, long action); + +static inline int set_memory_ro(unsigned long addr, int numpages) +{ + return change_memory_attr(addr, numpages, SET_MEMORY_RO); +} + +static inline int set_memory_rw(unsigned long addr, int numpages) +{ + return change_memory_attr(addr, numpages, SET_MEMORY_RW); +} + +static inline int set_memory_nx(unsigned long addr, int numpages) +{ + return change_memory_attr(addr, numpages, SET_MEMORY_NX); +} + +static inline int set_memory_x(unsigned long addr, int numpages) +{ + return change_memory_attr(addr, numpages, SET_MEMORY_X); +} + +#endif diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile index c3df3a8501d4..9142cf1fb0d5 100644 --- a/arch/powerpc/mm/Makefile +++ b/arch/powerpc/mm/Makefile @@ -5,7 +5,7 @@ ccflags-$(CONFIG_PPC64) := $(NO_MINIMAL_TOC) -obj-y := fault.o mem.o pgtable.o mmap.o maccess.o \ +obj-y := fault.o mem.o pgtable.o mmap.o maccess.o pageattr.o \ init_$(BITS).o pgtable_$(BITS).o \ pgtable-frag.o ioremap.o ioremap_$(BITS).o \ init-common.o mmu_context.o drmem.o \ diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c new file mode 100644 index 000000000000..acfdde78e0fb --- /dev/null +++ b/arch/powerpc/mm/pageattr.c @@ -0,0 +1,100 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * MMU-generic set_memory implementation for powerpc + * + * Copyright 2019-2021, IBM Corporation. + */ + +#include +#include +#include + +#include +#include +#include + + +/* + * Updates the attributes of a page in three steps: + * + * 1. invalidate the page table entry + * 2. flush the TLB + * 3. install the new entry with the updated attributes + * + * Invalidating the pte means there are situations where this will not work + * when in theory it should. + * For example: + * - removing write from page whilst it is being executed + * - setting a page read-only whilst it is being read by another CPU + * + */ +static int change_page_attr(pte_t *ptep, unsigned long addr, void *data) +{ + long action = (long)data; + pte_t pte; + + spin_lock(&init_mm.page_table_lock); + + /* invalidate the PTE so it's safe to modify */ + pte = ptep_get_and_clear(&init_mm, addr, ptep); + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); + + /* modify the PTE bits as desired, then apply */ + switch (action) { + case SET_MEMORY_RO: + pte = pte_wrprotect(pte); + break; + case SET_MEMORY_RW: + pte = pte_mkwrite(pte_mkdirty(pte)); + break; + case SET_MEMORY_NX: + pte = pte_exprotect(pte); + break; + case SET_MEMORY_X: + pte = pte_mkexec(pte); + break; + default: + WARN_ON_ONCE(1); + break; + } + + set_pte_at(&init_mm, addr, ptep, pte); + + /* See ptesync comment in radix__set_pte_at() */ + if (radix_enabled()) + asm volatile("ptesync": : :"memory"); + spin_unlock(&init_mm.page_table_lock); + + return 0; +} + +int change_memory_attr(unsigned long addr, int numpages, long action) +{ + unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE); + unsigned long size = numpages * PAGE_SIZE; + + if (!numpages) + return 0; + + if (WARN_ON_ONCE(is_vm_area_hugepages((void *)addr))) + return -EINVAL; + +#ifdef CONFIG_PPC_BOOK3S_64 + /* + * On hash, the linear mapping is not in the Linux page table so + * apply_to_existing_page_range() will have no effect. If in the future + * the set_memory_* functions are used on the linear map this will need + * to be updated. + */ + if (!radix_enabled()) { + int region = get_region_id(addr); + + if (WARN_ON_ONCE(region != VMALLOC_REGION_ID && region != IO_REGION_ID)) + return -EINVAL; + } +#endif + + return apply_to_existing_page_range(&init_mm, start, size, + change_page_attr, (void *)action); +} -- 2.25.1