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Date:   Wed, 04 Mar 2020 16:57:42 -0800 (PST)
Subject:     Re: [PATCH 1/8] riscv: add ARCH_HAS_SET_MEMORY support
In-Reply-To: <20200217083223.2011-2-zong.li@sifive.com>
CC:     Paul Walmsley <paul.walmsley@sifive.com>, aou@eecs.berkeley.edu,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        zong.li@sifive.com
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     zong.li@sifive.com
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On Mon, 17 Feb 2020 00:32:16 PST (-0800), zong.li@sifive.com wrote:
> Add set_memory_ro/rw/x/nx architecture hooks to change the page
> attribution.
>
> Use own set_memory.h rather than generic set_memory.h
> (i.e. include/asm-generic/set_memory.h), because we want to add other
> function prototypes here.
>
> Signed-off-by: Zong Li <zong.li@sifive.com>
> ---
>  arch/riscv/Kconfig                  |   1 +
>  arch/riscv/include/asm/set_memory.h |  17 ++++
>  arch/riscv/mm/Makefile              |   1 +
>  arch/riscv/mm/pageattr.c            | 150 ++++++++++++++++++++++++++++
>  4 files changed, 169 insertions(+)
>  create mode 100644 arch/riscv/include/asm/set_memory.h
>  create mode 100644 arch/riscv/mm/pageattr.c
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 6e81da55b5e4..76ed36543b3a 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -60,6 +60,7 @@ config RISCV
>  	select HAVE_EBPF_JIT if 64BIT
>  	select EDAC_SUPPORT
>  	select ARCH_HAS_GIGANTIC_PAGE
> +	select ARCH_HAS_SET_MEMORY
>  	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
>  	select SPARSEMEM_STATIC if 32BIT
>  	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
> diff --git a/arch/riscv/include/asm/set_memory.h b/arch/riscv/include/asm/set_memory.h
> new file mode 100644
> index 000000000000..936f08063566
> --- /dev/null
> +++ b/arch/riscv/include/asm/set_memory.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2019 SiFive
> + */
> +
> +#ifndef _ASM_RISCV_SET_MEMORY_H
> +#define _ASM_RISCV_SET_MEMORY_H
> +
> +/*
> + * Functions to change memory attributes.
> + */
> +int set_memory_ro(unsigned long addr, int numpages);
> +int set_memory_rw(unsigned long addr, int numpages);
> +int set_memory_x(unsigned long addr, int numpages);
> +int set_memory_nx(unsigned long addr, int numpages);
> +
> +#endif /* _ASM_RISCV_SET_MEMORY_H */
> diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
> index 814e16a8d68a..b94643aee84c 100644
> --- a/arch/riscv/mm/Makefile
> +++ b/arch/riscv/mm/Makefile
> @@ -10,6 +10,7 @@ obj-y += extable.o
>  obj-$(CONFIG_MMU) += fault.o
>  obj-y += cacheflush.o
>  obj-y += context.o
> +obj-y += pageattr.o
>
>  ifeq ($(CONFIG_MMU),y)
>  obj-$(CONFIG_SMP) += tlbflush.o
> diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
> new file mode 100644
> index 000000000000..fcd59ef2835b
> --- /dev/null
> +++ b/arch/riscv/mm/pageattr.c
> @@ -0,0 +1,150 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2019 SiFive
> + */
> +
> +#include <linux/pagewalk.h>
> +#include <asm/pgtable.h>
> +#include <asm/tlbflush.h>
> +#include <asm/bitops.h>
> +
> +struct pageattr_masks {
> +	pgprot_t set_mask;
> +	pgprot_t clear_mask;
> +};
> +
> +static unsigned long set_pageattr_masks(unsigned long val, struct mm_walk *walk)
> +{
> +	struct pageattr_masks *masks = walk->private;
> +	unsigned long new_val = val;
> +
> +	new_val &= ~(pgprot_val(masks->clear_mask));
> +	new_val |= (pgprot_val(masks->set_mask));
> +
> +	return new_val;
> +}
> +
> +static int pageattr_pgd_entry(pgd_t *pgd, unsigned long addr,
> +			      unsigned long next, struct mm_walk *walk)
> +{
> +	pgd_t val = READ_ONCE(*pgd);
> +
> +	if (pgd_leaf(val)) {
> +		val = __pgd(set_pageattr_masks(pgd_val(val), walk));
> +		set_pgd(pgd, val);
> +	}
> +
> +	return 0;
> +}
> +
> +static int pageattr_p4d_entry(p4d_t *p4d, unsigned long addr,
> +			      unsigned long next, struct mm_walk *walk)
> +{
> +	p4d_t val = READ_ONCE(*p4d);
> +
> +	if (p4d_leaf(val)) {
> +		val = __p4d(set_pageattr_masks(p4d_val(val), walk));
> +		set_p4d(p4d, val);
> +	}
> +
> +	return 0;
> +}
> +
> +static int pageattr_pud_entry(pud_t *pud, unsigned long addr,
> +			      unsigned long next, struct mm_walk *walk)
> +{
> +	pud_t val = READ_ONCE(*pud);
> +
> +	if (pud_leaf(val)) {
> +		val = __pud(set_pageattr_masks(pud_val(val), walk));
> +		set_pud(pud, val);
> +	}
> +
> +	return 0;
> +}
> +
> +static int pageattr_pmd_entry(pmd_t *pmd, unsigned long addr,
> +			      unsigned long next, struct mm_walk *walk)
> +{
> +	pmd_t val = READ_ONCE(*pmd);
> +
> +	if (pmd_leaf(val)) {
> +		val = __pmd(set_pageattr_masks(pmd_val(val), walk));
> +		set_pmd(pmd, val);
> +	}
> +
> +	return 0;
> +}
> +
> +static int pageattr_pte_entry(pte_t *pte, unsigned long addr,
> +			      unsigned long next, struct mm_walk *walk)
> +{
> +	pte_t val = READ_ONCE(*pte);
> +
> +	val = __pte(set_pageattr_masks(pte_val(val), walk));
> +	set_pte(pte, val);
> +
> +	return 0;
> +}
> +
> +static int pageattr_pte_hole(unsigned long addr, unsigned long next,
> +			     int depth, struct mm_walk *walk)
> +{
> +	/* Nothing to do here */
> +	return 0;
> +}
> +
> +const static struct mm_walk_ops pageattr_ops = {
> +	.pgd_entry = pageattr_pgd_entry,
> +	.p4d_entry = pageattr_p4d_entry,
> +	.pud_entry = pageattr_pud_entry,
> +	.pmd_entry = pageattr_pmd_entry,
> +	.pte_entry = pageattr_pte_entry,
> +	.pte_hole = pageattr_pte_hole,
> +};
> +
> +static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask,
> +			pgprot_t clear_mask)
> +{
> +	int ret;
> +	unsigned long start = addr;
> +	unsigned long end = start + PAGE_SIZE * numpages;
> +	struct pageattr_masks masks = {
> +		.set_mask = set_mask,
> +		.clear_mask = clear_mask
> +	};
> +
> +	if (!numpages)
> +		return 0;
> +
> +	down_read(&init_mm.mmap_sem);
> +	ret =  walk_page_range_novma(&init_mm, start, end, &pageattr_ops, NULL,
> +				     &masks);
> +	up_read(&init_mm.mmap_sem);

There are very few users of _novma, but I think it's correct here.

> +
> +	flush_tlb_kernel_range(start, end);
> +
> +	return ret;
> +}
> +
> +int set_memory_ro(unsigned long addr, int numpages)
> +{
> +	return __set_memory(addr, numpages, __pgprot(_PAGE_READ),
> +			    __pgprot(_PAGE_WRITE));
> +}
> +
> +int set_memory_rw(unsigned long addr, int numpages)
> +{
> +	return __set_memory(addr, numpages, __pgprot(_PAGE_READ | _PAGE_WRITE),
> +			    __pgprot(0));
> +}
> +
> +int set_memory_x(unsigned long addr, int numpages)
> +{
> +	return __set_memory(addr, numpages, __pgprot(_PAGE_EXEC), __pgprot(0));
> +}
> +
> +int set_memory_nx(unsigned long addr, int numpages)
> +{
> +	return __set_memory(addr, numpages, __pgprot(0), __pgprot(_PAGE_EXEC));
> +}

Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>

Thanks!