From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-189.mta0.migadu.com (out-189.mta0.migadu.com [91.218.175.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 783303ABD95 for ; Tue, 7 Jul 2026 06:47:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783406872; cv=none; b=ZZkzi7JfURVBN8PkYBI3ULyTI13BI1VyBYrHDl72kj0Fkjj5+Q1wjeFSB5gYBmaHfkmwPKAaTsFF7Fo+2J9AnbcZkYE10NeA68FeWqRi6/ZpG5ROp5IT6wdvhvx+3PTookYliVssQJubcAgek2EyI9Sh7nA8KUS4TaNpGWr02fg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783406872; c=relaxed/simple; bh=SsZpmwGPyG/d5MkuvyqBSVwYAx4Vkr8Q3+3h+a5P+rY=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=LwatlLSCOFXvveUo6c80Y09Rwfk1d/2fRQtETsgC3aeHxfQ1AVeJVd1jiS86j+vuoE5DmiwJR8WzAkFmK/wHKyQS/2oaPilwu1JDYhYJnFyAQvGLsMa5qyhWWpd91q/mFhZ+Jkwo4DO7Cxxg1zq+3VseCIrl98AaW4XPL3SDY24= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=XDp4osp2; arc=none smtp.client-ip=91.218.175.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="XDp4osp2" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1783406868; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=H+ZbaHB8r4c4OtxkmyaRaJ+GF9AV1trwxBbCUaJXsoI=; b=XDp4osp2qthRNLpT4rK7vqUjlRYnLRKOU+jN6Rcv4dUa+h4bTZdzG01zUEHpf0E3pcWmIg cR2RGjTp9aZ/nRmWCaenAhtwLl1Hn+919dDO6IXTMJQ9ooAUy/3oiIfoGulGV63KVroDQ+ 2ASttmAgNICXUsWXug5rswDNqwWG4mc= From: haoran.jiang@linux.dev To: loongarch@lists.linux.dev Cc: linux-kernel@vger.kernel.org, chenhuacai@kernel.org, kernel@xen0n.name, yangtiezhu@loongson.cn, Haoran Jiang , Xiujie Jiang Subject: [PATCH 2/2] LoongArch: Add support to dump the kernel page tables Date: Tue, 7 Jul 2026 14:45:56 +0800 Message-Id: <20260707064556.371881-3-haoran.jiang@linux.dev> In-Reply-To: <20260707064556.371881-1-haoran.jiang@linux.dev> References: <20260707064556.371881-1-haoran.jiang@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Haoran Jiang In a similar manner to riscv,arm64,x86 etc.,this patch allows dumping the page tables of the LoongArch page-mapped virtual memory region via a debugfs file, which is useful for kernel developers to inspect page table layouts and verify permissions and type settings. Co-developed-by: Xiujie Jiang Signed-off-by: Xiujie Jiang Signed-off-by: Haoran Jiang --- arch/loongarch/Kconfig | 1 + arch/loongarch/mm/Makefile | 1 + arch/loongarch/mm/ptdump.c | 474 +++++++++++++++++++++++++++++++++++++ 3 files changed, 476 insertions(+) create mode 100644 arch/loongarch/mm/ptdump.c diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig index 2c5de66bf047..632998c64a74 100644 --- a/arch/loongarch/Kconfig +++ b/arch/loongarch/Kconfig @@ -25,6 +25,7 @@ config LOONGARCH select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE select ARCH_HAS_PREEMPT_LAZY select ARCH_HAS_PTE_SPECIAL if 64BIT + select ARCH_HAS_PTDUMP select ARCH_HAS_SET_MEMORY select ARCH_HAS_SET_DIRECT_MAP select ARCH_HAS_STRICT_MODULE_RWX diff --git a/arch/loongarch/mm/Makefile b/arch/loongarch/mm/Makefile index 2aae3773de77..0be8ee87fc5b 100644 --- a/arch/loongarch/mm/Makefile +++ b/arch/loongarch/mm/Makefile @@ -10,5 +10,6 @@ obj-y += init.o cache.o tlb.o tlbex.o extable.o \ obj-$(CONFIG_HIGHMEM) += highmem.o obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o obj-$(CONFIG_KASAN) += kasan_init.o +obj-$(CONFIG_PTDUMP_DEBUGFS) += ptdump.o KASAN_SANITIZE_kasan_init.o := n diff --git a/arch/loongarch/mm/ptdump.c b/arch/loongarch/mm/ptdump.c new file mode 100644 index 000000000000..003ed1d55615 --- /dev/null +++ b/arch/loongarch/mm/ptdump.c @@ -0,0 +1,474 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Derived from riscv implementation + */ + +#include +#include +#include +#include +#include +#include + +#define _PAGE_PLV_VAL 0x0 + +#define pt_dump_seq_printf(m, fmt, args...) \ +({ \ + if (m) \ + seq_printf(m, fmt, ##args); \ +}) + +#define pt_dump_seq_puts(m, fmt) \ +({ \ + if (m) \ + seq_puts(m, fmt); \ +}) + +/* + * The page dumper groups page table entries of the same type into a single + * description. It uses pg_state to track the range information while + * iterating over the pte entries. When the continuity is broken it then + * 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 long start_pa; + unsigned long last_pa; + int level; + u64 current_prot; + bool check_wx; + unsigned long wx_pages; +}; + +/* Address marker */ +struct addr_marker { + unsigned long start_address; + const char *name; +}; + +/* Private information for debugfs */ +struct ptd_mm_info { + struct mm_struct *mm; + const struct addr_marker *markers; + unsigned long base_addr; + unsigned long end; +}; + +/* Page Table Entry */ +struct prot_bits { + u64 mask; + u64 val; + const char *set; + const char *clear; +}; + +/* Page Level */ +struct pg_level { + const char *name; + u64 mask; +}; + +enum address_markers_idx { + PCI_IO_START_NR, + PCI_IO_END_NR, + MODULES_START_NR, + MODULES_END_NR, + VMALLOC_START_NR, + VMALLOC_END_NR, +#ifdef CONFIG_SPARSEMEM_VMEMMAP + VMEMMAP_START_NR, + VMEMMAP_END_NR, +#endif +#ifdef CONFIG_KFENCE + KFENCE_AREA_START_NR, + KFENCE_AREA_END_NR, +#endif +#ifdef CONFIG_KASAN + KASAN_SHADOW_START_NR, + KASAN_SHADOW_END_NR, +#endif + FIXMAP_START_NR, + FIXMAP_END_NR, + END_OF_SPACE_NR +}; + + + +static struct addr_marker address_markers[] = { + {0, "PCI I/O start"}, + {0, "PCI I/O end"}, + {0, "modules start"}, + {0, "modules end"}, + {0, "vmalloc() area"}, + {0, "vmalloc() end"}, +#ifdef CONFIG_SPARSEMEM_VMEMMAP + {0, "vmemmap start"}, + {0, "vmemmap end"}, +#endif +#ifdef CONFIG_KFENCE + {0, "kfence area start"}, + {0, "kfence area end"}, +#endif +#ifdef CONFIG_KASAN + {0, "Kasan shadow start"}, + {0, "Kasan shadow end"}, +#endif + {0, "Fixmap start"}, + {0, "Fixmap end"}, + {-1, NULL}, +}; + + +static struct ptd_mm_info kernel_ptd_info = { + .mm = &init_mm, + .markers = address_markers, + .base_addr = 0, + .end = ULONG_MAX, +}; + +static const struct prot_bits pte_bits[] = { + { + .mask = _PAGE_VALID, + .val = _PAGE_VALID, + .set = "V", + .clear = " ", + }, { + .mask = _PAGE_DIRTY, + .val = _PAGE_DIRTY, + .set = "D", + .clear = " ", + }, { + .mask = _PAGE_PLV, + .val = _PAGE_PLV_VAL, + .set = "KERN", + .clear = "USR ", + }, { + .mask = _CACHE_MASK, + .val = _CACHE_MASK, + .set = " ", + .clear = "SUC", + }, { + .mask = _PAGE_GLOBAL, + .val = _PAGE_GLOBAL, + .set = "G", + .clear = " ", + }, { + .mask = _PAGE_PRESENT, + .val = _PAGE_PRESENT, + .set = "P", + .clear = " ", + }, { + .mask = _PAGE_WRITE, + .val = _PAGE_WRITE, + .set = "W", + .clear = " ", + }, { + .mask = _PAGE_HGLOBAL, + .val = _PAGE_HGLOBAL, + .set = "G", + .clear = " ", + }, { + .mask = _PAGE_NO_READ, + .val = _PAGE_NO_READ, + .set = "NR", + .clear = " ", + }, { + .mask = _PAGE_NO_EXEC, + .val = _PAGE_NO_EXEC, + .set = "NX", + .clear = " ", + }, { + .mask = _PAGE_RPLV, + .val = _PAGE_RPLV, + .set = "RPLV", + .clear = " ", + } +}; + +static struct pg_level pg_level[] = { + { /* pgd */ + .name = "PGD", + }, { /* p4d */ + .name = (CONFIG_PGTABLE_LEVELS > 4) ? "P4D" : "PGD", + }, { /* pud */ + .name = (CONFIG_PGTABLE_LEVELS > 3) ? "PUD" : "PGD", + }, { /* pmd */ + .name = (CONFIG_PGTABLE_LEVELS > 2) ? "PMD" : "PGD", + }, { /* pte */ + .name = "PTE", + }, +}; + +static void dump_prot(struct pg_state *st) +{ + + unsigned int i; + + for (i = 0; i < ARRAY_SIZE(pte_bits); i++) { + const char *s; + + if (pte_bits[i].mask == _CACHE_MASK) { + if ((st->current_prot & pte_bits[i].mask) == _CACHE_CC) + s = "CC "; + else if ((st->current_prot & pte_bits[i].mask) == _CACHE_WUC) + s = "WUC"; + else + s = pte_bits[i].clear; + } else if (pte_bits[i].mask == _PAGE_GLOBAL) { + if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val) { + if (st->level != 4) + s = "PSE"; + else + s = pte_bits[i].set; + } else { + s = pte_bits[i].clear; + } + + } else { + if ((st->current_prot & pte_bits[i].mask) == pte_bits[i].val) + s = pte_bits[i].set; + else + s = pte_bits[i].clear; + } + + + if (s) + pt_dump_seq_printf(st->seq, " %s", s); + } + +} + + +#ifdef CONFIG_64BIT +#define ADDR_FORMAT "0x%016lx" +#else +#define ADDR_FORMAT "0x%08lx" +#endif +static void dump_addr(struct pg_state *st, unsigned long addr) +{ + static const char units[] = "KMGTPE"; + const char *unit = units; + unsigned long delta; + + pt_dump_seq_printf(st->seq, ADDR_FORMAT "-" ADDR_FORMAT " ", + st->start_address, addr); + + pt_dump_seq_printf(st->seq, " " ADDR_FORMAT " ", st->start_pa); + delta = (addr - st->start_address) >> 10; + + while (!(delta & 1023) && unit[1]) { + delta >>= 10; + unit++; + } + + pt_dump_seq_printf(st->seq, "%9lu%c %s", delta, *unit, + pg_level[st->level].name); +} + +static void note_prot_wx(struct pg_state *st, unsigned long addr) +{ + if (!st->check_wx) + return; + if ((st->current_prot & _PAGE_WRITE) == 0) + return; + if ((st->current_prot & _PAGE_NO_EXEC) == _PAGE_NO_EXEC) + return; + + WARN_ONCE(1, "loongarch/mm: Found insecure W+X mapping at address %p/%pS\n", + (void *)st->start_address, (void *)st->start_address); + + st->wx_pages += (addr - st->start_address) / PAGE_SIZE; + +} + +static void note_page(struct ptdump_state *pt_st, unsigned long addr, + int level, u64 val) +{ + struct pg_state *st = container_of(pt_st, struct pg_state, ptdump); + u64 pa = PFN_PHYS(pte_pfn(__pte(val))); + u64 prot = 0; + + if (level >= 0) + prot = val & pg_level[level].mask; + + if (st->level == -1) { + st->level = level; + st->current_prot = prot; + st->start_address = addr; + st->start_pa = pa; + st->last_pa = pa; + pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name); + } else if (prot != st->current_prot || + level != st->level || addr >= st->marker[1].start_address) { + if (st->current_prot) { + note_prot_wx(st, addr); + dump_addr(st, addr); + dump_prot(st); + pt_dump_seq_puts(st->seq, "\n"); + } + + while (addr >= st->marker[1].start_address) { + st->marker++; + pt_dump_seq_printf(st->seq, "---[ %s ]---\n", + st->marker->name); + } + + st->start_address = addr; + st->start_pa = pa; + st->last_pa = pa; + st->current_prot = prot; + st->level = level; + } else { + st->last_pa = pa; + } +} + +static void note_page_pte(struct ptdump_state *pt_st, unsigned long addr, pte_t pte) +{ + note_page(pt_st, addr, 4, pte_val(pte)); +} + +static void note_page_pmd(struct ptdump_state *pt_st, unsigned long addr, pmd_t pmd) +{ + note_page(pt_st, addr, 3, pmd_val(pmd)); +} + +static void note_page_pud(struct ptdump_state *pt_st, unsigned long addr, pud_t pud) +{ + note_page(pt_st, addr, 2, pud_val(pud)); +} + +static void note_page_p4d(struct ptdump_state *pt_st, unsigned long addr, p4d_t p4d) +{ + note_page(pt_st, addr, 1, p4d_val(p4d)); +} + +static void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd) +{ + note_page(pt_st, addr, 0, pgd_val(pgd)); +} + +static void note_page_flush(struct ptdump_state *pt_st) +{ + pte_t pte_zero = {0}; + + note_page(pt_st, 0, -1, pte_val(pte_zero)); +} + +static void ptdump_walk(struct seq_file *s, struct ptd_mm_info *pinfo) +{ + struct pg_state st = { + .seq = s, + .marker = pinfo->markers, + .level = -1, + .ptdump = { + .note_page_pte = note_page_pte, + .note_page_pmd = note_page_pmd, + .note_page_pud = note_page_pud, + .note_page_p4d = note_page_p4d, + .note_page_pgd = note_page_pgd, + .note_page_flush = note_page_flush, + .range = (struct ptdump_range[]) { + {pinfo->base_addr, pinfo->end}, + {0, 0} + } + } + }; + + ptdump_walk_pgd(&st.ptdump, pinfo->mm, NULL); +} + +bool ptdump_check_wx(void) +{ + struct pg_state st = { + .seq = NULL, + .marker = (struct addr_marker[]) { + {0, NULL}, + {-1, NULL}, + }, + .level = -1, + .check_wx = true, + .ptdump = { + .note_page_pte = note_page_pte, + .note_page_pmd = note_page_pmd, + .note_page_pud = note_page_pud, + .note_page_p4d = note_page_p4d, + .note_page_pgd = note_page_pgd, + .note_page_flush = note_page_flush, + .range = (struct ptdump_range[]) { + {vm_map_base, ULONG_MAX}, + {0, 0} + } + } + }; + + ptdump_walk_pgd(&st.ptdump, &init_mm, NULL); + + if (st.wx_pages) { + pr_warn("Checked W+X mappings: failed, %lu W+X pages found\n", + st.wx_pages); + + return false; + } + + pr_info("Checked W+X mappings: passed, no W+X pages found\n"); + + return true; +} + +static int ptdump_show(struct seq_file *m, void *v) +{ + struct ptd_mm_info *info = m->private; + + ptdump_walk(m, info); + return 0; +} +DEFINE_SHOW_ATTRIBUTE(ptdump); + +static int __init ptdump_init(void) +{ + unsigned int i, j; + + address_markers[PCI_IO_START_NR].start_address = (unsigned long)PCI_IOBASE; + address_markers[PCI_IO_END_NR].start_address = (unsigned long)PCI_IOBASE + IO_SPACE_LIMIT; + + address_markers[MODULES_START_NR].start_address = MODULES_VADDR; + address_markers[MODULES_END_NR].start_address = MODULES_END; + + address_markers[VMALLOC_START_NR].start_address = VMALLOC_START; + address_markers[VMALLOC_END_NR].start_address = VMALLOC_END; + +#ifdef CONFIG_SPARSEMEM_VMEMMAP + address_markers[VMEMMAP_START_NR].start_address = (unsigned long)vmemmap; + address_markers[VMEMMAP_END_NR].start_address = VMEMMAP_END; +#endif + +#ifdef CONFIG_KFENCE + address_markers[KFENCE_AREA_START_NR].start_address = KFENCE_AREA_START; + address_markers[KFENCE_AREA_END_NR].start_address = KFENCE_AREA_END; +#endif + +#ifdef CONFIG_KASAN + address_markers[KASAN_SHADOW_START_NR].start_address = KASAN_SHADOW_START; + address_markers[KASAN_SHADOW_END_NR].start_address = KASAN_SHADOW_END; +#endif + + address_markers[FIXMAP_START_NR].start_address = FIXADDR_START; + address_markers[FIXMAP_END_NR].start_address = FIXADDR_TOP; + + kernel_ptd_info.base_addr = vm_map_base; + + for (i = 0; i < ARRAY_SIZE(pg_level); i++) { + for (j = 0; j < ARRAY_SIZE(pte_bits); j++) + pg_level[i].mask |= pte_bits[j].mask; + } + + debugfs_create_file("kernel_page_tables", 0400, NULL, &kernel_ptd_info, &ptdump_fops); + + return 0; +} + +device_initcall(ptdump_init); -- 2.43.0