1 files changed, 472 insertions, 0 deletions
diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
new file mode 100644
index 000000000..aca354fb6
--- /dev/null
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -0,0 +1,472 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2016, Rashmica Gupta, IBM Corp.
+ *
+ * This traverses the kernel pagetables and dumps the
+ * information about the used sections of memory to
+ * /sys/kernel/debug/kernel_pagetables.
+ *
+ * Derived from the arm64 implementation:
+ * Copyright (c) 2014, The Linux Foundation, Laura Abbott.
+ * (C) Copyright 2008 Intel Corporation, Arjan van de Ven.
+ */
+#include <linux/debugfs.h>
+#include <linux/fs.h>
+#include <linux/hugetlb.h>
+#include <linux/io.h>
+#include <linux/mm.h>
+#include <linux/highmem.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <asm/fixmap.h>
+#include <linux/const.h>
+#include <asm/page.h>
+#include <asm/hugetlb.h>
+
+#include <mm/mmu_decl.h>
+
+#include "ptdump.h"
+
+/*
+ * To visualise what is happening,
+ *
+ *  - PTRS_PER_P** = how many entries there are in the corresponding P**
+ *  - P**_SHIFT = how many bits of the address we use to index into the
+ * corresponding P**
+ *  - P**_SIZE is how much memory we can access through the table - not the
+ * size of the table itself.
+ * P**={PGD, PUD, PMD, PTE}
+ *
+ *
+ * Each entry of the PGD points to a PUD. Each entry of a PUD points to a
+ * PMD. Each entry of a PMD points to a PTE. And every PTE entry points to
+ * a page.
+ *
+ * In the case where there are only 3 levels, the PUD is folded into the
+ * PGD: every PUD has only one entry which points to the PMD.
+ *
+ * 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 - ie PTEs that are virtually contiguous
+ * with the same PTE flags are chunked together. This is to make it clear how
+ * different areas of the kernel virtual memory are used.
+ *
+ */
+struct pg_state {
+	struct seq_file *seq;
+	const struct addr_marker *marker;
+	unsigned long start_address;
+	unsigned long start_pa;
+	unsigned long last_pa;
+	unsigned long page_size;
+	unsigned int level;
+	u64 current_flags;
+	bool check_wx;
+	unsigned long wx_pages;
+};
+
+struct addr_marker {
+	unsigned long start_address;
+	const char *name;
+};
+
+static struct addr_marker address_markers[] = {
+	{ 0,	"Start of kernel VM" },
+#ifdef MODULES_VADDR
+	{ 0,	"modules start" },
+	{ 0,	"modules end" },
+#endif
+	{ 0,	"vmalloc() Area" },
+	{ 0,	"vmalloc() End" },
+#ifdef CONFIG_PPC64
+	{ 0,	"isa I/O start" },
+	{ 0,	"isa I/O end" },
+	{ 0,	"phb I/O start" },
+	{ 0,	"phb I/O end" },
+	{ 0,	"I/O remap start" },
+	{ 0,	"I/O remap end" },
+	{ 0,	"vmemmap start" },
+#else
+	{ 0,	"Early I/O remap start" },
+	{ 0,	"Early I/O remap end" },
+#ifdef CONFIG_HIGHMEM
+	{ 0,	"Highmem PTEs start" },
+	{ 0,	"Highmem PTEs end" },
+#endif
+	{ 0,	"Fixmap start" },
+	{ 0,	"Fixmap end" },
+#endif
+#ifdef CONFIG_KASAN
+	{ 0,	"kasan shadow mem start" },
+	{ 0,	"kasan shadow mem end" },
+#endif
+	{ -1,	NULL },
+};
+
+#define pt_dump_seq_printf(m, fmt, args...)	\
+({						\
+	if (m)					\
+		seq_printf(m, fmt, ##args);	\
+})
+
+#define pt_dump_seq_putc(m, c)		\
+({					\
+	if (m)				\
+		seq_putc(m, c);		\
+})
+
+void pt_dump_size(struct seq_file *m, unsigned long size)
+{
+	static const char units[] = "KMGTPE";
+	const char *unit = units;
+
+	/* Work out what appropriate unit to use */
+	while (!(size & 1023) && unit[1]) {
+		size >>= 10;
+		unit++;
+	}
+	pt_dump_seq_printf(m, "%9lu%c ", size, *unit);
+}
+
+static void dump_flag_info(struct pg_state *st, const struct flag_info
+		*flag, u64 pte, int num)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++, flag++) {
+		const char *s = NULL;
+		u64 val;
+
+		/* flag not defined so don't check it */
+		if (flag->mask == 0)
+			continue;
+		/* Some 'flags' are actually values */
+		if (flag->is_val) {
+			val = pte & flag->val;
+			if (flag->shift)
+				val = val >> flag->shift;
+			pt_dump_seq_printf(st->seq, "  %s:%llx", flag->set, val);
+		} else {
+			if ((pte & flag->mask) == flag->val)
+				s = flag->set;
+			else
+				s = flag->clear;
+			if (s)
+				pt_dump_seq_printf(st->seq, "  %s", s);
+		}
+		st->current_flags &= ~flag->mask;
+	}
+	if (st->current_flags != 0)
+		pt_dump_seq_printf(st->seq, "  unknown flags:%llx", st->current_flags);
+}
+
+static void dump_addr(struct pg_state *st, unsigned long addr)
+{
+	unsigned long delta;
+
+#ifdef CONFIG_PPC64
+#define REG		"0x%016lx"
+#else
+#define REG		"0x%08lx"
+#endif
+
+	pt_dump_seq_printf(st->seq, REG "-" REG " ", st->start_address, addr - 1);
+	if (st->start_pa == st->last_pa && st->start_address + st->page_size != addr) {
+		pt_dump_seq_printf(st->seq, "[" REG "]", st->start_pa);
+		delta = st->page_size >> 10;
+	} else {
+		pt_dump_seq_printf(st->seq, " " REG " ", st->start_pa);
+		delta = (addr - st->start_address) >> 10;
+	}
+	pt_dump_size(st->seq, delta);
+}
+
+static void note_prot_wx(struct pg_state *st, unsigned long addr)
+{
+	pte_t pte = __pte(st->current_flags);
+
+	if (!IS_ENABLED(CONFIG_PPC_DEBUG_WX) || !st->check_wx)
+		return;
+
+	if (!pte_write(pte) || !pte_exec(pte))
+		return;
+
+	WARN_ONCE(1, "powerpc/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_update_state(struct pg_state *st, unsigned long addr,
+				   unsigned int level, u64 val, unsigned long page_size)
+{
+	u64 flag = val & pg_level[level].mask;
+	u64 pa = val & PTE_RPN_MASK;
+
+	st->level = level;
+	st->current_flags = flag;
+	st->start_address = addr;
+	st->start_pa = pa;
+	st->page_size = page_size;
+
+	while (addr >= st->marker[1].start_address) {
+		st->marker++;
+		pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
+	}
+}
+
+static void note_page(struct pg_state *st, unsigned long addr,
+	       unsigned int level, u64 val, unsigned long page_size)
+{
+	u64 flag = val & pg_level[level].mask;
+	u64 pa = val & PTE_RPN_MASK;
+
+	/* At first no level is set */
+	if (!st->level) {
+		pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
+		note_page_update_state(st, addr, level, val, page_size);
+	/*
+	 * Dump the section of virtual memory when:
+	 *   - the PTE flags from one entry to the next differs.
+	 *   - we change levels in the tree.
+	 *   - the address is in a different section of memory and is thus
+	 *   used for a different purpose, regardless of the flags.
+	 *   - the pa of this page is not adjacent to the last inspected page
+	 */
+	} else if (flag != st->current_flags || level != st->level ||
+		   addr >= st->marker[1].start_address ||
+		   (pa != st->last_pa + st->page_size &&
+		    (pa != st->start_pa || st->start_pa != st->last_pa))) {
+
+		/* Check the PTE flags */
+		if (st->current_flags) {
+			note_prot_wx(st, addr);
+			dump_addr(st, addr);
+
+			/* Dump all the flags */
+			if (pg_level[st->level].flag)
+				dump_flag_info(st, pg_level[st->level].flag,
+					  st->current_flags,
+					  pg_level[st->level].num);
+
+			pt_dump_seq_putc(st->seq, '\n');
+		}
+
+		/*
+		 * Address indicates we have passed the end of the
+		 * current section of virtual memory
+		 */
+		note_page_update_state(st, addr, level, val, page_size);
+	}
+	st->last_pa = pa;
+}
+
+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 int i;
+
+	for (i = 0; i < PTRS_PER_PTE; i++, pte++) {
+		addr = start + i * PAGE_SIZE;
+		note_page(st, addr, 4, pte_val(*pte), PAGE_SIZE);
+
+	}
+}
+
+static void walk_hugepd(struct pg_state *st, hugepd_t *phpd, unsigned long start,
+			int pdshift, int level)
+{
+#ifdef CONFIG_ARCH_HAS_HUGEPD
+	unsigned int i;
+	int shift = hugepd_shift(*phpd);
+	int ptrs_per_hpd = pdshift - shift > 0 ? 1 << (pdshift - shift) : 1;
+
+	if (start & ((1 << shift) - 1))
+		return;
+
+	for (i = 0; i < ptrs_per_hpd; i++) {
+		unsigned long addr = start + (i << shift);
+		pte_t *pte = hugepte_offset(*phpd, addr, pdshift);
+
+		note_page(st, addr, level + 1, pte_val(*pte), 1 << shift);
+	}
+#endif
+}
+
+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 int i;
+
+	for (i = 0; i < PTRS_PER_PMD; i++, pmd++) {
+		addr = start + i * PMD_SIZE;
+		if (!pmd_none(*pmd) && !pmd_is_leaf(*pmd))
+			/* pmd exists */
+			walk_pte(st, pmd, addr);
+		else
+			note_page(st, addr, 3, pmd_val(*pmd), PMD_SIZE);
+	}
+}
+
+static void walk_pud(struct pg_state *st, p4d_t *p4d, unsigned long start)
+{
+	pud_t *pud = pud_offset(p4d, 0);
+	unsigned long addr;
+	unsigned int i;
+
+	for (i = 0; i < PTRS_PER_PUD; i++, pud++) {
+		addr = start + i * PUD_SIZE;
+		if (!pud_none(*pud) && !pud_is_leaf(*pud))
+			/* pud exists */
+			walk_pmd(st, pud, addr);
+		else
+			note_page(st, addr, 2, pud_val(*pud), PUD_SIZE);
+	}
+}
+
+static void walk_pagetables(struct pg_state *st)
+{
+	unsigned int i;
+	unsigned long addr = st->start_address & PGDIR_MASK;
+	pgd_t *pgd = pgd_offset_k(addr);
+
+	/*
+	 * Traverse the linux pagetable structure and dump pages that are in
+	 * the hash pagetable.
+	 */
+	for (i = pgd_index(addr); i < PTRS_PER_PGD; i++, pgd++, addr += PGDIR_SIZE) {
+		p4d_t *p4d = p4d_offset(pgd, 0);
+
+		if (p4d_none(*p4d) || p4d_is_leaf(*p4d))
+			note_page(st, addr, 1, p4d_val(*p4d), PGDIR_SIZE);
+		else if (is_hugepd(__hugepd(p4d_val(*p4d))))
+			walk_hugepd(st, (hugepd_t *)p4d, addr, PGDIR_SHIFT, 1);
+		else
+			/* p4d exists */
+			walk_pud(st, p4d, addr);
+	}
+}
+
+static void populate_markers(void)
+{
+	int i = 0;
+
+#ifdef CONFIG_PPC64
+	address_markers[i++].start_address = PAGE_OFFSET;
+#else
+	address_markers[i++].start_address = TASK_SIZE;
+#endif
+#ifdef MODULES_VADDR
+	address_markers[i++].start_address = MODULES_VADDR;
+	address_markers[i++].start_address = MODULES_END;
+#endif
+	address_markers[i++].start_address = VMALLOC_START;
+	address_markers[i++].start_address = VMALLOC_END;
+#ifdef CONFIG_PPC64
+	address_markers[i++].start_address = ISA_IO_BASE;
+	address_markers[i++].start_address = ISA_IO_END;
+	address_markers[i++].start_address = PHB_IO_BASE;
+	address_markers[i++].start_address = PHB_IO_END;
+	address_markers[i++].start_address = IOREMAP_BASE;
+	address_markers[i++].start_address = IOREMAP_END;
+	/* What is the ifdef about? */
+#ifdef CONFIG_PPC_BOOK3S_64
+	address_markers[i++].start_address =  H_VMEMMAP_START;
+#else
+	address_markers[i++].start_address =  VMEMMAP_BASE;
+#endif
+#else /* !CONFIG_PPC64 */
+	address_markers[i++].start_address = ioremap_bot;
+	address_markers[i++].start_address = IOREMAP_TOP;
+#ifdef CONFIG_HIGHMEM
+	address_markers[i++].start_address = PKMAP_BASE;
+	address_markers[i++].start_address = PKMAP_ADDR(LAST_PKMAP);
+#endif
+	address_markers[i++].start_address = FIXADDR_START;
+	address_markers[i++].start_address = FIXADDR_TOP;
+#ifdef CONFIG_KASAN
+	address_markers[i++].start_address = KASAN_SHADOW_START;
+	address_markers[i++].start_address = KASAN_SHADOW_END;
+#endif
+#endif /* CONFIG_PPC64 */
+}
+
+static int ptdump_show(struct seq_file *m, void *v)
+{
+	struct pg_state st = {
+		.seq = m,
+		.marker = address_markers,
+		.start_address = IS_ENABLED(CONFIG_PPC64) ? PAGE_OFFSET : TASK_SIZE,
+	};
+
+#ifdef CONFIG_PPC64
+	if (!radix_enabled())
+		st.start_address = KERN_VIRT_START;
+#endif
+
+	/* Traverse kernel page tables */
+	walk_pagetables(&st);
+	note_page(&st, 0, 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 void build_pgtable_complete_mask(void)
+{
+	unsigned int i, j;
+
+	for (i = 0; i < ARRAY_SIZE(pg_level); i++)
+		if (pg_level[i].flag)
+			for (j = 0; j < pg_level[i].num; j++)
+				pg_level[i].mask |= pg_level[i].flag[j].mask;
+}
+
+#ifdef CONFIG_PPC_DEBUG_WX
+void ptdump_check_wx(void)
+{
+	struct pg_state st = {
+		.seq = NULL,
+		.marker = address_markers,
+		.check_wx = true,
+		.start_address = IS_ENABLED(CONFIG_PPC64) ? PAGE_OFFSET : TASK_SIZE,
+	};
+
+#ifdef CONFIG_PPC64
+	if (!radix_enabled())
+		st.start_address = KERN_VIRT_START;
+#endif
+
+	walk_pagetables(&st);
+
+	if (st.wx_pages)
+		pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n",
+			st.wx_pages);
+	else
+		pr_info("Checked W+X mappings: passed, no W+X pages found\n");
+}
+#endif
+
+static int ptdump_init(void)
+{
+	populate_markers();
+	build_pgtable_complete_mask();
+	debugfs_create_file("kernel_page_tables", 0400, NULL, NULL,
+			    &ptdump_fops);
+	return 0;
+}
+device_initcall(ptdump_init);