1 files changed, 249 insertions, 0 deletions
diff --git a/arch/s390/mm/dump_pagetables.c b/arch/s390/mm/dump_pagetables.c
new file mode 100644
index 000000000..7cdea2ec5
--- /dev/null
+++ b/arch/s390/mm/dump_pagetables.c
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <asm/sections.h>
+#include <asm/pgtable.h>
+
+static unsigned long max_addr;
+
+struct addr_marker {
+	unsigned long start_address;
+	const char *name;
+};
+
+enum address_markers_idx {
+	IDENTITY_NR = 0,
+	KERNEL_START_NR,
+	KERNEL_END_NR,
+	VMEMMAP_NR,
+	VMALLOC_NR,
+	MODULES_NR,
+};
+
+static struct addr_marker address_markers[] = {
+	[IDENTITY_NR]	  = {0, "Identity Mapping"},
+	[KERNEL_START_NR] = {(unsigned long)_stext, "Kernel Image Start"},
+	[KERNEL_END_NR]	  = {(unsigned long)_end, "Kernel Image End"},
+	[VMEMMAP_NR]	  = {0, "vmemmap Area"},
+	[VMALLOC_NR]	  = {0, "vmalloc Area"},
+	[MODULES_NR]	  = {0, "Modules Area"},
+	{ -1, NULL }
+};
+
+struct pg_state {
+	int level;
+	unsigned int current_prot;
+	unsigned long start_address;
+	unsigned long current_address;
+	const struct addr_marker *marker;
+};
+
+static void print_prot(struct seq_file *m, unsigned int pr, int level)
+{
+	static const char * const level_name[] =
+		{ "ASCE", "PGD", "PUD", "PMD", "PTE" };
+
+	seq_printf(m, "%s ", level_name[level]);
+	if (pr & _PAGE_INVALID) {
+		seq_printf(m, "I\n");
+		return;
+	}
+	seq_puts(m, (pr & _PAGE_PROTECT) ? "RO " : "RW ");
+	seq_puts(m, (pr & _PAGE_NOEXEC) ? "NX\n" : "X\n");
+}
+
+static void note_page(struct seq_file *m, struct pg_state *st,
+		     unsigned int new_prot, int level)
+{
+	static const char units[] = "KMGTPE";
+	int width = sizeof(unsigned long) * 2;
+	const char *unit = units;
+	unsigned int prot, cur;
+	unsigned long delta;
+
+	/*
+	 * If we have a "break" in the series, we need to flush the state
+	 * that we have now. "break" is either changing perms, levels or
+	 * address space marker.
+	 */
+	prot = new_prot;
+	cur = st->current_prot;
+
+	if (!st->level) {
+		/* First entry */
+		st->current_prot = new_prot;
+		st->level = level;
+		st->marker = address_markers;
+		seq_printf(m, "---[ %s ]---\n", st->marker->name);
+	} else if (prot != cur || level != st->level ||
+		   st->current_address >= st->marker[1].start_address) {
+		/* Print the actual finished series */
+		seq_printf(m, "0x%0*lx-0x%0*lx",
+			   width, st->start_address,
+			   width, st->current_address);
+		delta = (st->current_address - st->start_address) >> 10;
+		while (!(delta & 0x3ff) && unit[1]) {
+			delta >>= 10;
+			unit++;
+		}
+		seq_printf(m, "%9lu%c ", delta, *unit);
+		print_prot(m, st->current_prot, st->level);
+		if (st->current_address >= st->marker[1].start_address) {
+			st->marker++;
+			seq_printf(m, "---[ %s ]---\n", st->marker->name);
+		}
+		st->start_address = st->current_address;
+		st->current_prot = new_prot;
+		st->level = level;
+	}
+}
+
+/*
+ * The actual page table walker functions. In order to keep the
+ * implementation of print_prot() short, we only check and pass
+ * _PAGE_INVALID and _PAGE_PROTECT flags to note_page() if a region,
+ * segment or page table entry is invalid or read-only.
+ * After all it's just a hint that the current level being walked
+ * contains an invalid or read-only entry.
+ */
+static void walk_pte_level(struct seq_file *m, struct pg_state *st,
+			   pmd_t *pmd, unsigned long addr)
+{
+	unsigned int prot;
+	pte_t *pte;
+	int i;
+
+	for (i = 0; i < PTRS_PER_PTE && addr < max_addr; i++) {
+		st->current_address = addr;
+		pte = pte_offset_kernel(pmd, addr);
+		prot = pte_val(*pte) &
+			(_PAGE_PROTECT | _PAGE_INVALID | _PAGE_NOEXEC);
+		note_page(m, st, prot, 4);
+		addr += PAGE_SIZE;
+	}
+}
+
+static void walk_pmd_level(struct seq_file *m, struct pg_state *st,
+			   pud_t *pud, unsigned long addr)
+{
+	unsigned int prot;
+	pmd_t *pmd;
+	int i;
+
+	for (i = 0; i < PTRS_PER_PMD && addr < max_addr; i++) {
+		st->current_address = addr;
+		pmd = pmd_offset(pud, addr);
+		if (!pmd_none(*pmd)) {
+			if (pmd_large(*pmd)) {
+				prot = pmd_val(*pmd) &
+					(_SEGMENT_ENTRY_PROTECT |
+					 _SEGMENT_ENTRY_NOEXEC);
+				note_page(m, st, prot, 3);
+			} else
+				walk_pte_level(m, st, pmd, addr);
+		} else
+			note_page(m, st, _PAGE_INVALID, 3);
+		addr += PMD_SIZE;
+	}
+}
+
+static void walk_pud_level(struct seq_file *m, struct pg_state *st,
+			   p4d_t *p4d, unsigned long addr)
+{
+	unsigned int prot;
+	pud_t *pud;
+	int i;
+
+	for (i = 0; i < PTRS_PER_PUD && addr < max_addr; i++) {
+		st->current_address = addr;
+		pud = pud_offset(p4d, addr);
+		if (!pud_none(*pud))
+			if (pud_large(*pud)) {
+				prot = pud_val(*pud) &
+					(_REGION_ENTRY_PROTECT |
+					 _REGION_ENTRY_NOEXEC);
+				note_page(m, st, prot, 2);
+			} else
+				walk_pmd_level(m, st, pud, addr);
+		else
+			note_page(m, st, _PAGE_INVALID, 2);
+		addr += PUD_SIZE;
+	}
+}
+
+static void walk_p4d_level(struct seq_file *m, struct pg_state *st,
+			   pgd_t *pgd, unsigned long addr)
+{
+	p4d_t *p4d;
+	int i;
+
+	for (i = 0; i < PTRS_PER_P4D && addr < max_addr; i++) {
+		st->current_address = addr;
+		p4d = p4d_offset(pgd, addr);
+		if (!p4d_none(*p4d))
+			walk_pud_level(m, st, p4d, addr);
+		else
+			note_page(m, st, _PAGE_INVALID, 2);
+		addr += P4D_SIZE;
+	}
+}
+
+static void walk_pgd_level(struct seq_file *m)
+{
+	unsigned long addr = 0;
+	struct pg_state st;
+	pgd_t *pgd;
+	int i;
+
+	memset(&st, 0, sizeof(st));
+	for (i = 0; i < PTRS_PER_PGD && addr < max_addr; i++) {
+		st.current_address = addr;
+		pgd = pgd_offset_k(addr);
+		if (!pgd_none(*pgd))
+			walk_p4d_level(m, &st, pgd, addr);
+		else
+			note_page(m, &st, _PAGE_INVALID, 1);
+		addr += PGDIR_SIZE;
+		cond_resched();
+	}
+	/* Flush out the last page */
+	st.current_address = max_addr;
+	note_page(m, &st, 0, 0);
+}
+
+static int ptdump_show(struct seq_file *m, void *v)
+{
+	walk_pgd_level(m);
+	return 0;
+}
+
+static int ptdump_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, ptdump_show, NULL);
+}
+
+static const struct file_operations ptdump_fops = {
+	.open		= ptdump_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+static int pt_dump_init(void)
+{
+	/*
+	 * Figure out the maximum virtual address being accessible with the
+	 * kernel ASCE. We need this to keep the page table walker functions
+	 * from accessing non-existent entries.
+	 */
+	max_addr = (S390_lowcore.kernel_asce & _REGION_ENTRY_TYPE_MASK) >> 2;
+	max_addr = 1UL << (max_addr * 11 + 31);
+	address_markers[MODULES_NR].start_address = MODULES_VADDR;
+	address_markers[VMEMMAP_NR].start_address = (unsigned long) vmemmap;
+	address_markers[VMALLOC_NR].start_address = VMALLOC_START;
+	debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
+	return 0;
+}
+device_initcall(pt_dump_init);