From mboxrd@z Thu Jan 1 00:00:00 1970 From: steve.capper@linaro.org (Steve Capper) Date: Mon, 24 Nov 2014 16:05:51 +0000 Subject: [PATCHv2] arm64: add support to dump the kernel page tables In-Reply-To: <1416262710-7798-1-git-send-email-lauraa@codeaurora.org> References: <1416262710-7798-1-git-send-email-lauraa@codeaurora.org> Message-ID: <20141124160550.GA10172@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Nov 17, 2014 at 02:18:30PM -0800, Laura Abbott wrote: > In a similar manner to arm, it's useful to be able to dump the page > tables to verify permissions and memory types. Add a debugfs file > to check the page tables. Hi Laura, Some comments below: The output looked sensible otherwise and worked well on a Juno running 4/64KB pages and 2,3,4-levels of page table. > > Signed-off-by: Laura Abbott > --- > v2: Addressed comments from Mark Rutland. Made the logic a bit more > consistent between functions. Now tested on 4K and 64K pages. > --- > arch/arm64/Kconfig.debug | 12 ++ > arch/arm64/mm/Makefile | 1 + > arch/arm64/mm/dump.c | 358 +++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 371 insertions(+) > create mode 100644 arch/arm64/mm/dump.c > > diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug > index 0a12933..5fdd6dc 100644 > --- a/arch/arm64/Kconfig.debug > +++ b/arch/arm64/Kconfig.debug > @@ -6,6 +6,18 @@ config FRAME_POINTER > bool > default y > > +config ARM64_PTDUMP > + bool "Export kernel pagetable layout to userspace via debugfs" > + depends on DEBUG_KERNEL > + select DEBUG_FS > + help > + Say Y here if you want to show the kernel pagetable layout in a > + debugfs file. This information is only useful for kernel developers > + who are working in architecture specific areas of the kernel. > + It is probably not a good idea to enable this feature in a production > + kernel. > + If in doubt, say "N" > + > config STRICT_DEVMEM > bool "Filter access to /dev/mem" > depends on MMU > diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile > index c56179e..773d37a 100644 > --- a/arch/arm64/mm/Makefile > +++ b/arch/arm64/mm/Makefile > @@ -3,3 +3,4 @@ obj-y := dma-mapping.o extable.o fault.o init.o \ > ioremap.o mmap.o pgd.o mmu.o \ > context.o proc.o pageattr.o > obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o > +obj-$(CONFIG_ARM64_PTDUMP) += dump.o > diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c > new file mode 100644 > index 0000000..57dcee4 > --- /dev/null > +++ b/arch/arm64/mm/dump.c > @@ -0,0 +1,358 @@ > +/* > + * Copyright (c) 2014, The Linux Foundation. All rights reserved. > + * Debug helper to dump the current kernel pagetables of the system > + * so that we can see what the various memory ranges are set to. > + * > + * Derived from x86 and arm implementation: > + * (C) Copyright 2008 Intel Corporation > + * > + * Author: Arjan van de Ven > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public License > + * as published by the Free Software Foundation; version 2 > + * of the License. > + */ > +#include > +#include > +#include > +#include > + > +#include > + > +#define LOWEST_ADDR (UL(0xffffffffffffffff) << VA_BITS) > + > +struct addr_marker { > + unsigned long start_address; > + const char *name; > +}; > + > +static struct addr_marker address_markers[] = { > + { 0, "vmalloc() Area" }, I don't think we need a 0 placeholder as VMALLOC_START is a compile time constant? > + { VMALLOC_END, "vmalloc() End" }, The vmemmap region could be represented here, otherwise on my Juno I get stragglers appearing. (I had SPARSEMEM_VMEMMAP=y). > + { MODULES_VADDR, "Modules" }, It would be nice to have an "End Modules" here. (That's a matter of taste though!) > + { PAGE_OFFSET, "Kernel Mapping" }, > + { -1, NULL }, > +}; > + > +struct pg_state { > + struct seq_file *seq; > + const struct addr_marker *marker; > + unsigned long start_address; > + unsigned level; > + u64 current_prot; > +}; > + > +struct prot_bits { > + u64 mask; > + u64 val; > + const char *set; > + const char *clear; > +}; > + > +static const struct prot_bits pte_bits[] = { > + { > + .mask = PTE_USER, > + .val = PTE_USER, > + .set = "USR", > + .clear = " ", > + }, { > + .mask = PTE_RDONLY, > + .val = PTE_RDONLY, > + .set = "ro", > + .clear = "RW", > + }, { > + .mask = PTE_PXN, > + .val = PTE_PXN, > + .set = "NX", > + .clear = "x ", > + }, { > + .mask = PTE_SHARED, > + .val = PTE_SHARED, > + .set = "SHD", > + .clear = " ", > + }, { > + .mask = PTE_AF, > + .val = PTE_AF, > + .set = "AF", > + .clear = " ", > + }, { > + .mask = PTE_NG, > + .val = PTE_NG, > + .set = "NG", > + .clear = " ", > + }, { > + .mask = PTE_UXN, > + .val = PTE_UXN, > + .set = "UXN", > + }, { > + .mask = PTE_ATTRINDX_MASK, > + .val = PTE_ATTRINDX(MT_DEVICE_nGnRnE), > + .set = "DEVICE/nGnRnE", > + }, { > + .mask = PTE_ATTRINDX_MASK, > + .val = PTE_ATTRINDX(MT_DEVICE_nGnRE), > + .set = "DEVICE/nGnRE", > + }, { > + .mask = PTE_ATTRINDX_MASK, > + .val = PTE_ATTRINDX(MT_DEVICE_GRE), > + .set = "DEVICE/GRE", > + }, { > + .mask = PTE_ATTRINDX_MASK, > + .val = PTE_ATTRINDX(MT_NORMAL_NC), > + .set = "MEM/BUFFERABLE", > + }, { > + .mask = PTE_ATTRINDX_MASK, > + .val = PTE_ATTRINDX(MT_NORMAL), > + .set = "MEM/NORMAL", > + } > +}; > + > +static const struct prot_bits section_bits[] = { > + { > + .mask = PMD_SECT_USER, > + .val = PMD_SECT_USER, > + .set = "USR", > + .clear = " ", > + }, { > + .mask = PMD_SECT_RDONLY, > + .val = PMD_SECT_RDONLY, > + .set = "ro", > + .clear = "RW", > + }, { > + .mask = PMD_SECT_PXN, > + .val = PMD_SECT_PXN, > + .set = "NX", > + .clear = "x ", > + }, { > + .mask = PMD_SECT_S, > + .val = PMD_SECT_S, > + .set = "SHD", > + .clear = " ", > + }, { > + .mask = PMD_SECT_AF, > + .val = PMD_SECT_AF, > + .set = "AF", > + .clear = " ", > + }, { > + .mask = PMD_SECT_NG, > + .val = PMD_SECT_NG, > + .set = "NG", > + .clear = " ", > + }, { > + .mask = PMD_SECT_UXN, > + .val = PMD_SECT_UXN, > + .set = "UXN", > + }, { > + .mask = PTE_ATTRINDX_MASK, > + .val = PTE_ATTRINDX(MT_DEVICE_nGnRnE), > + .set = "DEVICE/nGnRnE", > + }, { > + .mask = PTE_ATTRINDX_MASK, > + .val = PTE_ATTRINDX(MT_DEVICE_nGnRE), > + .set = "DEVICE/nGnRE", > + }, { > + .mask = PTE_ATTRINDX_MASK, > + .val = PTE_ATTRINDX(MT_DEVICE_GRE), > + .set = "DEVICE/GRE", > + }, { > + .mask = PTE_ATTRINDX_MASK, > + .val = PTE_ATTRINDX(MT_NORMAL_NC), > + .set = "MEM/BUFFERABLE", > + }, { > + .mask = PTE_ATTRINDX_MASK, > + .val = PTE_ATTRINDX(MT_NORMAL), > + .set = "MEM/NORMAL", > + } > +}; > + > +struct pg_level { > + const struct prot_bits *bits; > + size_t num; > + u64 mask; > +}; > + > +static struct pg_level pg_level[] = { > + { > + }, { /* pgd */ > + .bits = pte_bits, > + .num = ARRAY_SIZE(pte_bits), > + }, { /* pud */ > + .bits = pte_bits, > + .num = ARRAY_SIZE(pte_bits), > + }, { /* pmd */ > + .bits = section_bits, > + .num = ARRAY_SIZE(section_bits), > + }, { /* pte */ > + .bits = pte_bits, > + .num = ARRAY_SIZE(pte_bits), > + }, > +}; When I had a look, pte_bits matched section_bits perfectly. Could we drop section_bits entirely and switch over to pte_bits? > + > +static void dump_prot(struct pg_state *st, const struct prot_bits *bits, > + size_t num) > +{ > + unsigned i; > + > + for (i = 0; i < num; i++, bits++) { > + const char *s; > + > + if ((st->current_prot & bits->mask) == bits->val) > + s = bits->set; > + else > + s = bits->clear; > + > + if (s) > + seq_printf(st->seq, " %s", s); > + } > +} > + > +static void note_page(struct pg_state *st, unsigned long addr, unsigned level, > + u64 val) > +{ > + static const char units[] = "KMGTPE"; > + u64 prot = val & pg_level[level].mask; > + > + if (addr < LOWEST_ADDR) > + return; > + > + if (!st->level) { > + st->level = level; > + st->current_prot = prot; > + st->start_address = addr; > + seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); > + } else if (prot != st->current_prot || level != st->level || > + addr >= st->marker[1].start_address) { > + const char *unit = units; > + unsigned long delta; > + > + if (st->current_prot) { > + seq_printf(st->seq, "0x%16lx-0x%16lx ", > + st->start_address, addr); > + > + delta = (addr - st->start_address) >> 10; > + while (!(delta & 1023) && unit[1]) { > + delta >>= 10; > + unit++; > + } > + seq_printf(st->seq, "%9lu%c", delta, *unit); > + if (pg_level[st->level].bits) > + dump_prot(st, pg_level[st->level].bits, > + pg_level[st->level].num); > + seq_puts(st->seq, "\n"); > + } > + > + if (addr >= st->marker[1].start_address) { > + st->marker++; > + seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); > + } > + st->start_address = addr; > + st->current_prot = prot; > + st->level = level; > + } When I added "End Modules", I needed to add this here: if (addr >= st->marker[1].start_address) { st->marker++; seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); } (because it shared the same VA as "kernel mapping"). > +} > + > +static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start) > +{ > + pte_t *pte = pte_offset_kernel(pmd, 0); > + unsigned long addr; > + unsigned i; > + > + for (i = 0; i < PTRS_PER_PTE; i++, pte++) { > + addr = start + i * PAGE_SIZE; > + note_page(st, addr, 4, pte_val(*pte)); > + } > +} > + > +static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start) > +{ > + pmd_t *pmd = pmd_offset(pud, 0); > + unsigned long addr; > + unsigned i; > + > + for (i = 0; i < PTRS_PER_PMD; i++, pmd++) { > + addr = start + i * PMD_SIZE; > + if (pmd_none(*pmd) || pmd_sect(*pmd) || pmd_bad(*pmd)) > + note_page(st, addr, 3, pmd_val(*pmd)); > + else > + walk_pte(st, pmd, addr); > + } > +} > + > +static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start) > +{ > + pud_t *pud = pud_offset(pgd, 0); > + unsigned long addr; > + unsigned i; > + > + for (i = 0; i < PTRS_PER_PUD; i++, pud++) { > + addr = start + i * PUD_SIZE; > + if (pud_none(*pud) || pud_sect(*pud) || pud_bad(*pud)) > + note_page(st, addr, 2, pud_val(*pud)); > + else > + walk_pmd(st, pud, addr); > + } > +} > + > +static unsigned long normalize_addr(unsigned long u) > +{ > + return u | LOWEST_ADDR; > +} > + > +static void walk_pgd(struct pg_state *st, pgd_t *pgd, unsigned long start) > +{ > + unsigned i; > + unsigned long addr; > + > + for (i = 0; i < PTRS_PER_PGD; i++, pgd++) { > + addr = normalize_addr(start + i * PGDIR_SIZE); > + if (pgd_none(*pgd) || pgd_bad(*pgd)) > + note_page(st, addr, 1, pgd_val(*pgd)); > + else > + walk_pud(st, pgd, addr); > + } > +} > + > +static int ptdump_show(struct seq_file *m, void *v) > +{ > + struct pg_state st; > + > + memset(&st, 0, sizeof(st)); > + st.seq = m; > + st.marker = address_markers; > + > + walk_pgd(&st, swapper_pg_dir, 0); > + > + note_page(&st, 0, 0, 0); > + return 0; > +} > + > +static int ptdump_open(struct inode *inode, struct file *file) > +{ > + return single_open(file, ptdump_show, NULL); > +} > + > +static const struct file_operations ptdump_fops = { > + .open = ptdump_open, > + .read = seq_read, > + .llseek = seq_lseek, > + .release = single_release, > +}; > + > +static int ptdump_init(void) > +{ > + struct dentry *pe; > + unsigned i, j; > + > + for (i = 0; i < ARRAY_SIZE(pg_level); i++) > + if (pg_level[i].bits) > + for (j = 0; j < pg_level[i].num; j++) > + pg_level[i].mask |= pg_level[i].bits[j].mask; > + > + address_markers[0].start_address = VMALLOC_START; I don't think we need this. > + > + pe = debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, > + &ptdump_fops); > + return pe ? 0 : -ENOMEM; > +} > +device_initcall(ptdump_init); > -- Cheers, -- Steve