1 files changed, 375 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..2313053fe
--- /dev/null
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -0,0 +1,375 @@
+// 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/ptdump.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <asm/fixmap.h>
+#include <linux/const.h>
+#include <linux/kasan.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 ptdump_state ptdump;
+	struct seq_file *seq;
+	const struct addr_marker *marker;
+	unsigned long start_address;
+	unsigned long start_pa;
+	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 },
+};
+
+static struct ptdump_range ptdump_range[] __ro_after_init = {
+	{TASK_SIZE_MAX, ~0UL},
+	{0, 0}
+};
+
+#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)
+{
+#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);
+	pt_dump_seq_printf(st->seq, " " REG " ", st->start_pa);
+	pt_dump_size(st->seq, addr - st->start_address);
+}
+
+static void note_prot_wx(struct pg_state *st, unsigned long addr)
+{
+	pte_t pte = __pte(st->current_flags);
+
+	if (!IS_ENABLED(CONFIG_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, int level, u64 val)
+{
+	u64 flag = level >= 0 ? val & pg_level[level].mask : 0;
+	u64 pa = val & PTE_RPN_MASK;
+
+	st->level = level;
+	st->current_flags = flag;
+	st->start_address = addr;
+	st->start_pa = pa;
+
+	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 ptdump_state *pt_st, unsigned long addr, int level, u64 val)
+{
+	u64 flag = level >= 0 ? val & pg_level[level].mask : 0;
+	struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
+
+	/* At first no level is set */
+	if (st->level == -1) {
+		pt_dump_seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
+		note_page_update_state(st, addr, level, val);
+	/*
+	 * 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.
+	 */
+	} else if (flag != st->current_flags || level != st->level ||
+		   addr >= st->marker[1].start_address) {
+
+		/* 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);
+	}
+}
+
+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;
+#endif /* CONFIG_PPC64 */
+#ifdef CONFIG_KASAN
+	address_markers[i++].start_address = KASAN_SHADOW_START;
+	address_markers[i++].start_address = KASAN_SHADOW_END;
+#endif
+}
+
+static int ptdump_show(struct seq_file *m, void *v)
+{
+	struct pg_state st = {
+		.seq = m,
+		.marker = address_markers,
+		.level = -1,
+		.ptdump = {
+			.note_page = note_page,
+			.range = ptdump_range,
+		}
+	};
+
+	/* Traverse kernel page tables */
+	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
+	return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(ptdump);
+
+static void __init 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_DEBUG_WX
+void 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 = note_page,
+			.range = ptdump_range,
+		}
+	};
+
+	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);
+	else
+		pr_info("Checked W+X mappings: passed, no W+X pages found\n");
+}
+#endif
+
+static int __init ptdump_init(void)
+{
+#ifdef CONFIG_PPC64
+	if (!radix_enabled())
+		ptdump_range[0].start = KERN_VIRT_START;
+	else
+		ptdump_range[0].start = PAGE_OFFSET;
+
+	ptdump_range[0].end = PAGE_OFFSET + (PGDIR_SIZE * PTRS_PER_PGD);
+#endif
+
+	populate_markers();
+	build_pgtable_complete_mask();
+
+	if (IS_ENABLED(CONFIG_PTDUMP_DEBUGFS))
+		debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
+
+	return 0;
+}
+device_initcall(ptdump_init);