Re: [PATCH v17 21/23] arm64: mm: Convert mm/dump.c to use walk_page_range()

From: Ard Biesheuvel
Date: Sun Feb 16 2020 - 11:25:56 EST

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On Wed, 18 Dec 2019 at 17:25, Steven Price <steven.price@xxxxxxx> wrote:
>
> Now walk_page_range() can walk kernel page tables, we can switch the
> arm64 ptdump code over to using it, simplifying the code.
>
> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Signed-off-by: Steven Price <steven.price@xxxxxxx>

I did not realize this at the time, but this patch removes the ability
to dump the EFI page tables on 32-bit ARM. Was that intentional?

> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/Kconfig.debug | 19 +----
> arch/arm64/include/asm/ptdump.h | 8 +-
> arch/arm64/mm/Makefile | 4 +-
> arch/arm64/mm/dump.c | 117 ++++++++++-------------------
> arch/arm64/mm/mmu.c | 4 +-
> arch/arm64/mm/ptdump_debugfs.c | 2 +-
> drivers/firmware/efi/arm-runtime.c | 2 +-
> 8 files changed, 50 insertions(+), 107 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index b1b4476ddb83..43aa1de727f4 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -103,6 +103,7 @@ config ARM64
> select GENERIC_IRQ_SHOW
> select GENERIC_IRQ_SHOW_LEVEL
> select GENERIC_PCI_IOMAP
> + select GENERIC_PTDUMP
> select GENERIC_SCHED_CLOCK
> select GENERIC_SMP_IDLE_THREAD
> select GENERIC_STRNCPY_FROM_USER
> diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
> index cf09010d825f..1c906d932d6b 100644
> --- a/arch/arm64/Kconfig.debug
> +++ b/arch/arm64/Kconfig.debug
> @@ -1,22 +1,5 @@
> # SPDX-License-Identifier: GPL-2.0-only
>
> -config ARM64_PTDUMP_CORE
> - def_bool n
> -
> -config ARM64_PTDUMP_DEBUGFS
> - bool "Export kernel pagetable layout to userspace via debugfs"
> - depends on DEBUG_KERNEL
> - select ARM64_PTDUMP_CORE
> - 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 PID_IN_CONTEXTIDR
> bool "Write the current PID to the CONTEXTIDR register"
> help
> @@ -42,7 +25,7 @@ config ARM64_RANDOMIZE_TEXT_OFFSET
>
> config DEBUG_WX
> bool "Warn on W+X mappings at boot"
> - select ARM64_PTDUMP_CORE
> + select PTDUMP_CORE
> ---help---
> Generate a warning if any W+X mappings are found at boot.
>
> diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> index 0b8e7269ec82..38187f74e089 100644
> --- a/arch/arm64/include/asm/ptdump.h
> +++ b/arch/arm64/include/asm/ptdump.h
> @@ -5,7 +5,7 @@
> #ifndef __ASM_PTDUMP_H
> #define __ASM_PTDUMP_H
>
> -#ifdef CONFIG_ARM64_PTDUMP_CORE
> +#ifdef CONFIG_PTDUMP_CORE
>
> #include <linux/mm_types.h>
> #include <linux/seq_file.h>
> @@ -21,15 +21,15 @@ struct ptdump_info {
> unsigned long base_addr;
> };
>
> -void ptdump_walk_pgd(struct seq_file *s, struct ptdump_info *info);
> -#ifdef CONFIG_ARM64_PTDUMP_DEBUGFS
> +void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
> +#ifdef CONFIG_PTDUMP_DEBUGFS
> void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
> #else
> static inline void ptdump_debugfs_register(struct ptdump_info *info,
> const char *name) { }
> #endif
> void ptdump_check_wx(void);
> -#endif /* CONFIG_ARM64_PTDUMP_CORE */
> +#endif /* CONFIG_PTDUMP_CORE */
>
> #ifdef CONFIG_DEBUG_WX
> #define debug_checkwx() ptdump_check_wx()
> diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
> index 849c1df3d214..d91030f0ffee 100644
> --- a/arch/arm64/mm/Makefile
> +++ b/arch/arm64/mm/Makefile
> @@ -4,8 +4,8 @@ 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_CORE) += dump.o
> -obj-$(CONFIG_ARM64_PTDUMP_DEBUGFS) += ptdump_debugfs.o
> +obj-$(CONFIG_PTDUMP_CORE) += dump.o
> +obj-$(CONFIG_PTDUMP_DEBUGFS) += ptdump_debugfs.o
> obj-$(CONFIG_NUMA) += numa.o
> obj-$(CONFIG_DEBUG_VIRTUAL) += physaddr.o
> KASAN_SANITIZE_physaddr.o += n
> diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> index 0a920b538a89..f8c3ef7903ed 100644
> --- a/arch/arm64/mm/dump.c
> +++ b/arch/arm64/mm/dump.c
> @@ -15,6 +15,7 @@
> #include <linux/io.h>
> #include <linux/init.h>
> #include <linux/mm.h>
> +#include <linux/ptdump.h>
> #include <linux/sched.h>
> #include <linux/seq_file.h>
>
> @@ -75,10 +76,11 @@ static struct addr_marker address_markers[] = {
> * dumps out a description of the range.
> */
> struct pg_state {
> + struct ptdump_state ptdump;
> struct seq_file *seq;
> const struct addr_marker *marker;
> unsigned long start_address;
> - unsigned level;
> + int level;
> u64 current_prot;
> bool check_wx;
> unsigned long wx_pages;
> @@ -179,6 +181,10 @@ static struct pg_level pg_level[] = {
> .name = "PGD",
> .bits = pte_bits,
> .num = ARRAY_SIZE(pte_bits),
> + }, { /* p4d */
> + .name = "P4D",
> + .bits = pte_bits,
> + .num = ARRAY_SIZE(pte_bits),
> }, { /* pud */
> .name = (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD",
> .bits = pte_bits,
> @@ -241,11 +247,15 @@ static void note_prot_wx(struct pg_state *st, unsigned long addr)
> st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
> }
>
> -static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
> - u64 val)
> +static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
> + unsigned long val)
> {
> + struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
> static const char units[] = "KMGTPE";
> - u64 prot = val & pg_level[level].mask;
> + u64 prot = 0;
> +
> + if (level >= 0)
> + prot = val & pg_level[level].mask;
>
> if (!st->level) {
> st->level = level;
> @@ -293,85 +303,27 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
>
> }
>
> -static void walk_pte(struct pg_state *st, pmd_t *pmdp, unsigned long start,
> - unsigned long end)
> -{
> - unsigned long addr = start;
> - pte_t *ptep = pte_offset_kernel(pmdp, start);
> -
> - do {
> - note_page(st, addr, 4, READ_ONCE(pte_val(*ptep)));
> - } while (ptep++, addr += PAGE_SIZE, addr != end);
> -}
> -
> -static void walk_pmd(struct pg_state *st, pud_t *pudp, unsigned long start,
> - unsigned long end)
> -{
> - unsigned long next, addr = start;
> - pmd_t *pmdp = pmd_offset(pudp, start);
> -
> - do {
> - pmd_t pmd = READ_ONCE(*pmdp);
> - next = pmd_addr_end(addr, end);
> -
> - if (pmd_none(pmd) || pmd_sect(pmd)) {
> - note_page(st, addr, 3, pmd_val(pmd));
> - } else {
> - BUG_ON(pmd_bad(pmd));
> - walk_pte(st, pmdp, addr, next);
> - }
> - } while (pmdp++, addr = next, addr != end);
> -}
> -
> -static void walk_pud(struct pg_state *st, pgd_t *pgdp, unsigned long start,
> - unsigned long end)
> +void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
> {
> - unsigned long next, addr = start;
> - pud_t *pudp = pud_offset(pgdp, start);
> -
> - do {
> - pud_t pud = READ_ONCE(*pudp);
> - next = pud_addr_end(addr, end);
> -
> - if (pud_none(pud) || pud_sect(pud)) {
> - note_page(st, addr, 2, pud_val(pud));
> - } else {
> - BUG_ON(pud_bad(pud));
> - walk_pmd(st, pudp, addr, next);
> - }
> - } while (pudp++, addr = next, addr != end);
> -}
> + unsigned long end = ~0UL;
> + struct pg_state st;
>
> -static void walk_pgd(struct pg_state *st, struct mm_struct *mm,
> - unsigned long start)
> -{
> - unsigned long end = (start < TASK_SIZE_64) ? TASK_SIZE_64 : 0;
> - unsigned long next, addr = start;
> - pgd_t *pgdp = pgd_offset(mm, start);
> -
> - do {
> - pgd_t pgd = READ_ONCE(*pgdp);
> - next = pgd_addr_end(addr, end);
> -
> - if (pgd_none(pgd)) {
> - note_page(st, addr, 1, pgd_val(pgd));
> - } else {
> - BUG_ON(pgd_bad(pgd));
> - walk_pud(st, pgdp, addr, next);
> - }
> - } while (pgdp++, addr = next, addr != end);
> -}
> + if (info->base_addr < TASK_SIZE_64)
> + end = TASK_SIZE_64;
>
> -void ptdump_walk_pgd(struct seq_file *m, struct ptdump_info *info)
> -{
> - struct pg_state st = {
> - .seq = m,
> + st = (struct pg_state){
> + .seq = s,
> .marker = info->markers,
> + .ptdump = {
> + .note_page = note_page,
> + .range = (struct ptdump_range[]){
> + {info->base_addr, end},
> + {0, 0}
> + }
> + }
> };
>
> - walk_pgd(&st, info->mm, info->base_addr);
> -
> - note_page(&st, 0, 0, 0);
> + ptdump_walk_pgd(&st.ptdump, info->mm);
> }
>
> static void ptdump_initialize(void)
> @@ -399,10 +351,17 @@ void ptdump_check_wx(void)
> { -1, NULL},
> },
> .check_wx = true,
> + .ptdump = {
> + .note_page = note_page,
> + .range = (struct ptdump_range[]) {
> + {PAGE_OFFSET, ~0UL},
> + {0, 0}
> + }
> + }
> };
>
> - walk_pgd(&st, &init_mm, PAGE_OFFSET);
> - note_page(&st, 0, 0, 0);
> + ptdump_walk_pgd(&st.ptdump, &init_mm);
> +
> if (st.wx_pages || st.uxn_pages)
> pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found, %lu non-UXN pages found\n",
> st.wx_pages, st.uxn_pages);
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 5a3b15a14a7f..36e8f4f74433 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -943,13 +943,13 @@ int __init arch_ioremap_pud_supported(void)
> * SW table walks can't handle removal of intermediate entries.
> */
> return IS_ENABLED(CONFIG_ARM64_4K_PAGES) &&
> - !IS_ENABLED(CONFIG_ARM64_PTDUMP_DEBUGFS);
> + !IS_ENABLED(CONFIG_PTDUMP_DEBUGFS);
> }
>
> int __init arch_ioremap_pmd_supported(void)
> {
> /* See arch_ioremap_pud_supported() */
> - return !IS_ENABLED(CONFIG_ARM64_PTDUMP_DEBUGFS);
> + return !IS_ENABLED(CONFIG_PTDUMP_DEBUGFS);
> }
>
> int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
> diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
> index 064163f25592..1f2eae3e988b 100644
> --- a/arch/arm64/mm/ptdump_debugfs.c
> +++ b/arch/arm64/mm/ptdump_debugfs.c
> @@ -7,7 +7,7 @@
> static int ptdump_show(struct seq_file *m, void *v)
> {
> struct ptdump_info *info = m->private;
> - ptdump_walk_pgd(m, info);
> + ptdump_walk(m, info);
> return 0;
> }
> DEFINE_SHOW_ATTRIBUTE(ptdump);
> diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
> index 899b803842bb..9dda2602c862 100644
> --- a/drivers/firmware/efi/arm-runtime.c
> +++ b/drivers/firmware/efi/arm-runtime.c
> @@ -27,7 +27,7 @@
>
> extern u64 efi_system_table;
>
> -#ifdef CONFIG_ARM64_PTDUMP_DEBUGFS
> +#if defined(CONFIG_PTDUMP_DEBUGFS) && defined(CONFIG_ARM64)
> #include <asm/ptdump.h>
>
> static struct ptdump_info efi_ptdump_info = {
> --
> 2.20.1
>

Next message: Randy Dunlap: "Re: [PATCH] Documentation: DMA-API-HOWTO.txt: fixed grammer issues Fixed some of the grammer issues in DMA-API-HOWTO.txt using the software grammerly."
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