| Message ID | 20191030073111.140493-2-ruscur@russell.cc (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Implement STRICT_MODULE_RWX for powerpc | expand |
Le 30/10/2019 à 08:31, Russell Currey a écrit : > 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 completely generic across powerpc's many MMUs. > > It's possible that this could be optimised to be faster for specific > MMUs, but the focus is on having a generic and safe implementation for > now. > > 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, so that is left as a TODO for now. > > Signed-off-by: Russell Currey <ruscur@russell.cc> > --- > arch/powerpc/Kconfig | 1 + > arch/powerpc/include/asm/set_memory.h | 32 +++++++++++ > arch/powerpc/mm/Makefile | 1 + > arch/powerpc/mm/pageattr.c | 77 +++++++++++++++++++++++++++ > 4 files changed, 111 insertions(+) > 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 3e56c9c2f16e..8f7005f0d097 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -133,6 +133,7 @@ config PPC > select ARCH_HAS_PTE_SPECIAL > select ARCH_HAS_MEMBARRIER_CALLBACKS > 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) && !RELOCATABLE && !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..5230ddb2fefd > --- /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 1 > +#define SET_MEMORY_RW 2 > +#define SET_MEMORY_NX 3 > +#define SET_MEMORY_X 4 > + > +int change_memory_attr(unsigned long addr, int numpages, int 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 5e147986400d..d0a0bcbc9289 100644 > --- a/arch/powerpc/mm/Makefile > +++ b/arch/powerpc/mm/Makefile > @@ -20,3 +20,4 @@ obj-$(CONFIG_HIGHMEM) += highmem.o > obj-$(CONFIG_PPC_COPRO_BASE) += copro_fault.o > obj-$(CONFIG_PPC_PTDUMP) += ptdump/ > obj-$(CONFIG_KASAN) += kasan/ > +obj-$(CONFIG_ARCH_HAS_SET_MEMORY) += pageattr.o > diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c > new file mode 100644 > index 000000000000..aedd79173a44 > --- /dev/null > +++ b/arch/powerpc/mm/pageattr.c > @@ -0,0 +1,77 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +/* > + * MMU-generic set_memory implementation for powerpc > + * > + * Copyright 2019, IBM Corporation. > + */ > + > +#include <linux/mm.h> > +#include <linux/set_memory.h> > + > +#include <asm/mmu.h> > +#include <asm/page.h> > +#include <asm/pgtable.h> > + > + > +/* > + * 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 > + * > + * This is unsafe if 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. > + * > + * TODO make the implementation resistant to this. > + */ > +static int change_page_attr(pte_t *ptep, unsigned long addr, void *data) I don't like too much the way you are making this function more complex and less readable with local var, goto, etc ... You could just keep the v4 version of change_page_attr(), rename it __change_page_attr(), then add: static int change_page_attr(pte_t *ptep, unsigned long addr, void *data) { int ret; spin_lock(&init_mm.page_table_lock); ret = __change_page_attr(ptep, addr, data); spin_unlock(&init_mm.page_table_lock); return ret; } Christophe > +{ > + int action = *((int *)data); > + pte_t pte_val; > + int ret = 0; > + > + spin_lock(&init_mm.page_table_lock); > + > + // invalidate the PTE so it's safe to modify > + pte_val = 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_val = pte_wrprotect(pte_val); > + break; > + case SET_MEMORY_RW: > + pte_val = pte_mkwrite(pte_val); > + break; > + case SET_MEMORY_NX: > + pte_val = pte_exprotect(pte_val); > + break; > + case SET_MEMORY_X: > + pte_val = pte_mkexec(pte_val); > + break; > + default: > + WARN_ON(true); > + ret = -EINVAL; > + goto out; > + } > + > + set_pte_at(&init_mm, addr, ptep, pte_val); > +out: > + spin_unlock(&init_mm.page_table_lock); > + return ret; > +} > + > +int change_memory_attr(unsigned long addr, int numpages, int action) > +{ > + unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE); > + unsigned long size = numpages * PAGE_SIZE; > + > + if (!numpages) > + return 0; > + > + return apply_to_page_range(&init_mm, start, size, change_page_attr, &action); > +} >
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 3e56c9c2f16e..8f7005f0d097 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -133,6 +133,7 @@ config PPC select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_MEMBARRIER_CALLBACKS 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) && !RELOCATABLE && !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..5230ddb2fefd --- /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 1 +#define SET_MEMORY_RW 2 +#define SET_MEMORY_NX 3 +#define SET_MEMORY_X 4 + +int change_memory_attr(unsigned long addr, int numpages, int 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 5e147986400d..d0a0bcbc9289 100644 --- a/arch/powerpc/mm/Makefile +++ b/arch/powerpc/mm/Makefile @@ -20,3 +20,4 @@ obj-$(CONFIG_HIGHMEM) += highmem.o obj-$(CONFIG_PPC_COPRO_BASE) += copro_fault.o obj-$(CONFIG_PPC_PTDUMP) += ptdump/ obj-$(CONFIG_KASAN) += kasan/ +obj-$(CONFIG_ARCH_HAS_SET_MEMORY) += pageattr.o diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c new file mode 100644 index 000000000000..aedd79173a44 --- /dev/null +++ b/arch/powerpc/mm/pageattr.c @@ -0,0 +1,77 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * MMU-generic set_memory implementation for powerpc + * + * Copyright 2019, IBM Corporation. + */ + +#include <linux/mm.h> +#include <linux/set_memory.h> + +#include <asm/mmu.h> +#include <asm/page.h> +#include <asm/pgtable.h> + + +/* + * 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 + * + * This is unsafe if 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. + * + * TODO make the implementation resistant to this. + */ +static int change_page_attr(pte_t *ptep, unsigned long addr, void *data) +{ + int action = *((int *)data); + pte_t pte_val; + int ret = 0; + + spin_lock(&init_mm.page_table_lock); + + // invalidate the PTE so it's safe to modify + pte_val = 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_val = pte_wrprotect(pte_val); + break; + case SET_MEMORY_RW: + pte_val = pte_mkwrite(pte_val); + break; + case SET_MEMORY_NX: + pte_val = pte_exprotect(pte_val); + break; + case SET_MEMORY_X: + pte_val = pte_mkexec(pte_val); + break; + default: + WARN_ON(true); + ret = -EINVAL; + goto out; + } + + set_pte_at(&init_mm, addr, ptep, pte_val); +out: + spin_unlock(&init_mm.page_table_lock); + return ret; +} + +int change_memory_attr(unsigned long addr, int numpages, int action) +{ + unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE); + unsigned long size = numpages * PAGE_SIZE; + + if (!numpages) + return 0; + + return apply_to_page_range(&init_mm, start, size, change_page_attr, &action); +}
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 completely generic across powerpc's many MMUs. It's possible that this could be optimised to be faster for specific MMUs, but the focus is on having a generic and safe implementation for now. 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, so that is left as a TODO for now. Signed-off-by: Russell Currey <ruscur@russell.cc> --- arch/powerpc/Kconfig | 1 + arch/powerpc/include/asm/set_memory.h | 32 +++++++++++ arch/powerpc/mm/Makefile | 1 + arch/powerpc/mm/pageattr.c | 77 +++++++++++++++++++++++++++ 4 files changed, 111 insertions(+) create mode 100644 arch/powerpc/include/asm/set_memory.h create mode 100644 arch/powerpc/mm/pageattr.c