1 files changed, 315 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..b51666967
--- /dev/null
+++ b/arch/s390/mm/dump_pagetables.c
@@ -0,0 +1,315 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/set_memory.h>
+#include <linux/ptdump.h>
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/mm.h>
+#include <linux/kfence.h>
+#include <linux/kasan.h>
+#include <asm/ptdump.h>
+#include <asm/kasan.h>
+#include <asm/abs_lowcore.h>
+#include <asm/nospec-branch.h>
+#include <asm/sections.h>
+#include <asm/maccess.h>
+
+static unsigned long max_addr;
+
+struct addr_marker {
+	unsigned long start_address;
+	const char *name;
+};
+
+enum address_markers_idx {
+	IDENTITY_BEFORE_NR = 0,
+	IDENTITY_BEFORE_END_NR,
+	AMODE31_START_NR,
+	AMODE31_END_NR,
+	KERNEL_START_NR,
+	KERNEL_END_NR,
+#ifdef CONFIG_KFENCE
+	KFENCE_START_NR,
+	KFENCE_END_NR,
+#endif
+	IDENTITY_AFTER_NR,
+	IDENTITY_AFTER_END_NR,
+	VMEMMAP_NR,
+	VMEMMAP_END_NR,
+	VMALLOC_NR,
+	VMALLOC_END_NR,
+	MODULES_NR,
+	MODULES_END_NR,
+	ABS_LOWCORE_NR,
+	ABS_LOWCORE_END_NR,
+	MEMCPY_REAL_NR,
+	MEMCPY_REAL_END_NR,
+#ifdef CONFIG_KASAN
+	KASAN_SHADOW_START_NR,
+	KASAN_SHADOW_END_NR,
+#endif
+};
+
+static struct addr_marker address_markers[] = {
+	[IDENTITY_BEFORE_NR]	= {0, "Identity Mapping Start"},
+	[IDENTITY_BEFORE_END_NR] = {(unsigned long)_stext, "Identity Mapping End"},
+	[AMODE31_START_NR]	= {0, "Amode31 Area Start"},
+	[AMODE31_END_NR]	= {0, "Amode31 Area End"},
+	[KERNEL_START_NR]	= {(unsigned long)_stext, "Kernel Image Start"},
+	[KERNEL_END_NR]		= {(unsigned long)_end, "Kernel Image End"},
+#ifdef CONFIG_KFENCE
+	[KFENCE_START_NR]	= {0, "KFence Pool Start"},
+	[KFENCE_END_NR]		= {0, "KFence Pool End"},
+#endif
+	[IDENTITY_AFTER_NR]	= {(unsigned long)_end, "Identity Mapping Start"},
+	[IDENTITY_AFTER_END_NR]	= {0, "Identity Mapping End"},
+	[VMEMMAP_NR]		= {0, "vmemmap Area Start"},
+	[VMEMMAP_END_NR]	= {0, "vmemmap Area End"},
+	[VMALLOC_NR]		= {0, "vmalloc Area Start"},
+	[VMALLOC_END_NR]	= {0, "vmalloc Area End"},
+	[MODULES_NR]		= {0, "Modules Area Start"},
+	[MODULES_END_NR]	= {0, "Modules Area End"},
+	[ABS_LOWCORE_NR]	= {0, "Lowcore Area Start"},
+	[ABS_LOWCORE_END_NR]	= {0, "Lowcore Area End"},
+	[MEMCPY_REAL_NR]	= {0, "Real Memory Copy Area Start"},
+	[MEMCPY_REAL_END_NR]	= {0, "Real Memory Copy Area End"},
+#ifdef CONFIG_KASAN
+	[KASAN_SHADOW_START_NR]	= {KASAN_SHADOW_START, "Kasan Shadow Start"},
+	[KASAN_SHADOW_END_NR]	= {KASAN_SHADOW_END, "Kasan Shadow End"},
+#endif
+	{ -1, NULL }
+};
+
+struct pg_state {
+	struct ptdump_state ptdump;
+	struct seq_file *seq;
+	int level;
+	unsigned int current_prot;
+	bool check_wx;
+	unsigned long wx_pages;
+	unsigned long start_address;
+	const struct addr_marker *marker;
+};
+
+#define pt_dump_seq_printf(m, fmt, args...)	\
+({						\
+	struct seq_file *__m = (m);		\
+						\
+	if (__m)				\
+		seq_printf(__m, fmt, ##args);	\
+})
+
+#define pt_dump_seq_puts(m, fmt)		\
+({						\
+	struct seq_file *__m = (m);		\
+						\
+	if (__m)				\
+		seq_printf(__m, fmt);		\
+})
+
+static void print_prot(struct seq_file *m, unsigned int pr, int level)
+{
+	static const char * const level_name[] =
+		{ "ASCE", "PGD", "PUD", "PMD", "PTE" };
+
+	pt_dump_seq_printf(m, "%s ", level_name[level]);
+	if (pr & _PAGE_INVALID) {
+		pt_dump_seq_printf(m, "I\n");
+		return;
+	}
+	pt_dump_seq_puts(m, (pr & _PAGE_PROTECT) ? "RO " : "RW ");
+	pt_dump_seq_puts(m, (pr & _PAGE_NOEXEC) ? "NX\n" : "X\n");
+}
+
+static void note_prot_wx(struct pg_state *st, unsigned long addr)
+{
+#ifdef CONFIG_DEBUG_WX
+	if (!st->check_wx)
+		return;
+	if (st->current_prot & _PAGE_INVALID)
+		return;
+	if (st->current_prot & _PAGE_PROTECT)
+		return;
+	if (st->current_prot & _PAGE_NOEXEC)
+		return;
+	/*
+	 * The first lowcore page is W+X if spectre mitigations are using
+	 * trampolines or the BEAR enhancements facility is not installed,
+	 * in which case we have two lpswe instructions in lowcore that need
+	 * to be executable.
+	 */
+	if (addr == PAGE_SIZE && (nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)))
+		return;
+	WARN_ONCE(1, "s390/mm: Found insecure W+X mapping at address %pS\n",
+		  (void *)st->start_address);
+	st->wx_pages += (addr - st->start_address) / PAGE_SIZE;
+#endif /* CONFIG_DEBUG_WX */
+}
+
+static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level, u64 val)
+{
+	int width = sizeof(unsigned long) * 2;
+	static const char units[] = "KMGTPE";
+	const char *unit = units;
+	unsigned long delta;
+	struct pg_state *st;
+	struct seq_file *m;
+	unsigned int prot;
+
+	st = container_of(pt_st, struct pg_state, ptdump);
+	m = st->seq;
+	prot = val & (_PAGE_PROTECT | _PAGE_NOEXEC);
+	if (level == 4 && (val & _PAGE_INVALID))
+		prot = _PAGE_INVALID;
+	/* For pmd_none() & friends val gets passed as zero. */
+	if (level != 4 && !val)
+		prot = _PAGE_INVALID;
+	/* Final flush from generic code. */
+	if (level == -1)
+		addr = max_addr;
+	if (st->level == -1) {
+		pt_dump_seq_printf(m, "---[ %s ]---\n", st->marker->name);
+		st->start_address = addr;
+		st->current_prot = prot;
+		st->level = level;
+	} else if (prot != st->current_prot || level != st->level ||
+		   addr >= st->marker[1].start_address) {
+		note_prot_wx(st, addr);
+		pt_dump_seq_printf(m, "0x%0*lx-0x%0*lx ",
+				   width, st->start_address,
+				   width, addr);
+		delta = (addr - st->start_address) >> 10;
+		while (!(delta & 0x3ff) && unit[1]) {
+			delta >>= 10;
+			unit++;
+		}
+		pt_dump_seq_printf(m, "%9lu%c ", delta, *unit);
+		print_prot(m, st->current_prot, st->level);
+		while (addr >= st->marker[1].start_address) {
+			st->marker++;
+			pt_dump_seq_printf(m, "---[ %s ]---\n", st->marker->name);
+		}
+		st->start_address = addr;
+		st->current_prot = prot;
+		st->level = level;
+	}
+}
+
+#ifdef CONFIG_DEBUG_WX
+void ptdump_check_wx(void)
+{
+	struct pg_state st = {
+		.ptdump = {
+			.note_page = note_page,
+			.range = (struct ptdump_range[]) {
+				{.start = 0, .end = max_addr},
+				{.start = 0, .end = 0},
+			}
+		},
+		.seq = NULL,
+		.level = -1,
+		.current_prot = 0,
+		.check_wx = true,
+		.wx_pages = 0,
+		.start_address = 0,
+		.marker = (struct addr_marker[]) {
+			{ .start_address =  0, .name = NULL},
+			{ .start_address = -1, .name = NULL},
+		},
+	};
+
+	if (!MACHINE_HAS_NX)
+		return;
+	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 %sW+X pages found\n",
+			(nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)) ?
+			"unexpected " : "");
+}
+#endif /* CONFIG_DEBUG_WX */
+
+#ifdef CONFIG_PTDUMP_DEBUGFS
+static int ptdump_show(struct seq_file *m, void *v)
+{
+	struct pg_state st = {
+		.ptdump = {
+			.note_page = note_page,
+			.range = (struct ptdump_range[]) {
+				{.start = 0, .end = max_addr},
+				{.start = 0, .end = 0},
+			}
+		},
+		.seq = m,
+		.level = -1,
+		.current_prot = 0,
+		.check_wx = false,
+		.wx_pages = 0,
+		.start_address = 0,
+		.marker = address_markers,
+	};
+
+	get_online_mems();
+	mutex_lock(&cpa_mutex);
+	ptdump_walk_pgd(&st.ptdump, &init_mm, NULL);
+	mutex_unlock(&cpa_mutex);
+	put_online_mems();
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(ptdump);
+#endif /* CONFIG_PTDUMP_DEBUGFS */
+
+/*
+ * Heapsort from lib/sort.c is not a stable sorting algorithm, do a simple
+ * insertion sort to preserve the original order of markers with the same
+ * start address.
+ */
+static void sort_address_markers(void)
+{
+	struct addr_marker tmp;
+	int i, j;
+
+	for (i = 1; i < ARRAY_SIZE(address_markers) - 1; i++) {
+		tmp = address_markers[i];
+		for (j = i - 1; j >= 0 && address_markers[j].start_address > tmp.start_address; j--)
+			address_markers[j + 1] = address_markers[j];
+		address_markers[j + 1] = tmp;
+	}
+}
+
+static int pt_dump_init(void)
+{
+#ifdef CONFIG_KFENCE
+	unsigned long kfence_start = (unsigned long)__kfence_pool;
+#endif
+	/*
+	 * 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[IDENTITY_AFTER_END_NR].start_address = ident_map_size;
+	address_markers[AMODE31_START_NR].start_address = (unsigned long)__samode31;
+	address_markers[AMODE31_END_NR].start_address = (unsigned long)__eamode31;
+	address_markers[MODULES_NR].start_address = MODULES_VADDR;
+	address_markers[MODULES_END_NR].start_address = MODULES_END;
+	address_markers[ABS_LOWCORE_NR].start_address = __abs_lowcore;
+	address_markers[ABS_LOWCORE_END_NR].start_address = __abs_lowcore + ABS_LOWCORE_MAP_SIZE;
+	address_markers[MEMCPY_REAL_NR].start_address = __memcpy_real_area;
+	address_markers[MEMCPY_REAL_END_NR].start_address = __memcpy_real_area + MEMCPY_REAL_SIZE;
+	address_markers[VMEMMAP_NR].start_address = (unsigned long) vmemmap;
+	address_markers[VMEMMAP_END_NR].start_address = (unsigned long)vmemmap + vmemmap_size;
+	address_markers[VMALLOC_NR].start_address = VMALLOC_START;
+	address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
+#ifdef CONFIG_KFENCE
+	address_markers[KFENCE_START_NR].start_address = kfence_start;
+	address_markers[KFENCE_END_NR].start_address = kfence_start + KFENCE_POOL_SIZE;
+#endif
+	sort_address_markers();
+#ifdef CONFIG_PTDUMP_DEBUGFS
+	debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
+#endif /* CONFIG_PTDUMP_DEBUGFS */
+	return 0;
+}
+device_initcall(pt_dump_init);