s390/mm: add page table dumper

This is more or less the same as the x86 page table dumper which was merged four years ago: 926e5392 "x86: add code to dump the (kernel) page tables for visual inspection by kernel developers". We add a file at /sys/kernel/debug/kernel_page_tables for debugging purposes so it's quite easy to see the kernel page table layout and possible odd mappings: ---[ Identity Mapping ]--- 0x0000000000000000-0x0000000000100000 1M PTE RW ---[ Kernel Image Start ]--- 0x0000000000100000-0x0000000000800000 7M PMD RO 0x0000000000800000-0x00000000008a9000 676K PTE RO 0x00000000008a9000-0x0000000000900000 348K PTE RW 0x0000000000900000-0x0000000001500000 12M PMD RW ---[ Kernel Image End ]--- 0x0000000001500000-0x0000000280000000 10219M PMD RW 0x0000000280000000-0x000003d280000000 3904G PUD I ---[ vmemmap Area ]--- 0x000003d280000000-0x000003d288c00000 140M PTE RW 0x000003d288c00000-0x000003d300000000 1908M PMD I 0x000003d300000000-0x000003e000000000 52G PUD I ---[ vmalloc Area ]--- 0x000003e000000000-0x000003e000009000 36K PTE RW 0x000003e000009000-0x000003e0000ee000 916K PTE I 0x000003e0000ee000-0x000003e000146000 352K PTE RW 0x000003e000146000-0x000003e000200000 744K PTE I 0x000003e000200000-0x000003e080000000 2046M PMD I 0x000003e080000000-0x0000040000000000 126G PUD I This usually makes only sense for kernel developers. The output with CONFIG_DEBUG_PAGEALLOC is not very helpful, because of the huge number of mapped out pages, however I decided for the time being to not add a !DEBUG_PAGEALLOC dependency. Maybe it's helpful for somebody even with that option. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

s390/mm: add page table dumper
This is more or less the same as the x86 page table dumper which was merged four years ago: 926e5392 "x86: add code to dump the (kernel) page tables for visual inspection by kernel developers". We add a file at /sys/kernel/debug/kernel_page_tables for debugging purposes so it's quite easy to see the kernel page table layout and possible odd mappings: ---[ Identity Mapping ]--- 0x0000000000000000-0x0000000000100000 1M PTE RW ---[ Kernel Image Start ]--- 0x0000000000100000-0x0000000000800000 7M PMD RO 0x0000000000800000-0x00000000008a9000 676K PTE RO 0x00000000008a9000-0x0000000000900000 348K PTE RW 0x0000000000900000-0x0000000001500000 12M PMD RW ---[ Kernel Image End ]--- 0x0000000001500000-0x0000000280000000 10219M PMD RW 0x0000000280000000-0x000003d280000000 3904G PUD I ---[ vmemmap Area ]--- 0x000003d280000000-0x000003d288c00000 140M PTE RW 0x000003d288c00000-0x000003d300000000 1908M PMD I 0x000003d300000000-0x000003e000000000 52G PUD I ---[ vmalloc Area ]--- 0x000003e000000000-0x000003e000009000 36K PTE RW 0x000003e000009000-0x000003e0000ee000 916K PTE I 0x000003e0000ee000-0x000003e000146000 352K PTE RW 0x000003e000146000-0x000003e000200000 744K PTE I 0x000003e000200000-0x000003e080000000 2046M PMD I 0x000003e080000000-0x0000040000000000 126G PUD I This usually makes only sense for kernel developers. The output with CONFIG_DEBUG_PAGEALLOC is not very helpful, because of the huge number of mapped out pages, however I decided for the time being to not add a !DEBUG_PAGEALLOC dependency. Maybe it's helpful for somebody even with that option. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Heiko Carstens · Martin Schwidefsky
1 parent 51eee033dc
Showing 3 changed files with 232 additions and 0 deletions Side-by-side Diff
arch/s390/Kconfig.debug
arch/s390/mm/Makefile
arch/s390/mm/dump_pagetables.c
@@ -31,6 +31,18 @@
  
 	  If unsure, or if you run an older (pre 4.4) gcc, say N.
  
+config S390_PTDUMP
+	bool "Export kernel pagetable layout to userspace via debugfs"
+	depends on DEBUG_KERNEL
+	select DEBUG_FS
+	---help---
+	  Say Y here if you want to show the kernel pagetable layout in a
+	  debugfs file. This information is only useful for kernel developers
+	  who are working in architecture specific areas of the kernel.
+	  It is probably not a good idea to enable this feature in a production
+	  kernel.
+	  If in doubt, say "N"
+
 config DEBUG_SET_MODULE_RONX
 	def_bool y
 	depends on MODULES
@@ -7,4 +7,5 @@
 obj-$(CONFIG_CMM) += cmm.o
 obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
 obj-$(CONFIG_DEBUG_SET_MODULE_RONX) += pageattr.o
+obj-$(CONFIG_S390_PTDUMP) += dump_pagetables.o
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/module.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,
+};
+
+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"},
+	{ -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");
+	else
+		seq_printf(m, "%s\n", pr & _PAGE_RO ? "RO" : "RW");
+}
+
+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_RO
+ * 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_RO | _PAGE_INVALID);
+		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_RO;
+				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,
+			   pgd_t *pgd, unsigned long addr)
+{
+	pud_t *pud;
+	int i;
+
+	for (i = 0; i < PTRS_PER_PUD && addr < max_addr; i++) {
+		st->current_address = addr;
+		pud = pud_offset(pgd, addr);
+		if (!pud_none(*pud))
+			walk_pmd_level(m, st, pud, addr);
+		else
+			note_page(m, st, _PAGE_INVALID, 2);
+		addr += PUD_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_pud_level(m, &st, pgd, addr);
+		else
+			note_page(m, &st, _PAGE_INVALID, 1);
+		addr += PGDIR_SIZE;
+	}
+	/* 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.
+	 */
+#ifdef CONFIG_64BIT
+	max_addr = (S390_lowcore.kernel_asce & _REGION_ENTRY_TYPE_MASK) >> 2;
+	max_addr = 1UL << (max_addr * 11 + 31);
+#else
+	max_addr = 1UL << 31;
+#endif
+	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);
...	...	@@ -31,6 +31,18 @@
31	31
32	32	If unsure, or if you run an older (pre 4.4) gcc, say N.
33	33
	34	+config S390_PTDUMP
	35	+ bool "Export kernel pagetable layout to userspace via debugfs"
	36	+ depends on DEBUG_KERNEL
	37	+ select DEBUG_FS
	38	+ ---help---
	39	+ Say Y here if you want to show the kernel pagetable layout in a
	40	+ debugfs file. This information is only useful for kernel developers
	41	+ who are working in architecture specific areas of the kernel.
	42	+ It is probably not a good idea to enable this feature in a production
	43	+ kernel.
	44	+ If in doubt, say "N"
	45	+
34	46	config DEBUG_SET_MODULE_RONX
35	47	def_bool y
36	48	depends on MODULES
...	...	@@ -7,4 +7,5 @@
7	7	obj-$(CONFIG_CMM) += cmm.o
8	8	obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
9	9	obj-$(CONFIG_DEBUG_SET_MODULE_RONX) += pageattr.o
	10	+obj-$(CONFIG_S390_PTDUMP) += dump_pagetables.o
	1	+#include <linux/seq_file.h>
	2	+#include <linux/debugfs.h>
	3	+#include <linux/module.h>
	4	+#include <linux/mm.h>
	5	+#include <asm/sections.h>
	6	+#include <asm/pgtable.h>
	7	+
	8	+static unsigned long max_addr;
	9	+
	10	+struct addr_marker {
	11	+ unsigned long start_address;
	12	+ const char *name;
	13	+};
	14	+
	15	+enum address_markers_idx {
	16	+ IDENTITY_NR = 0,
	17	+ KERNEL_START_NR,
	18	+ KERNEL_END_NR,
	19	+ VMEMMAP_NR,
	20	+ VMALLOC_NR,
	21	+};
	22	+
	23	+static struct addr_marker address_markers[] = {
	24	+ [IDENTITY_NR] = {0, "Identity Mapping"},
	25	+ [KERNEL_START_NR] = {(unsigned long)&_stext, "Kernel Image Start"},
	26	+ [KERNEL_END_NR] = {(unsigned long)&_end, "Kernel Image End"},
	27	+ [VMEMMAP_NR] = {0, "vmemmap Area"},
	28	+ [VMALLOC_NR] = {0, "vmalloc Area"},
	29	+ { -1, NULL }
	30	+};
	31	+
	32	+struct pg_state {
	33	+ int level;
	34	+ unsigned int current_prot;
	35	+ unsigned long start_address;
	36	+ unsigned long current_address;
	37	+ const struct addr_marker *marker;
	38	+};
	39	+
	40	+static void print_prot(struct seq_file *m, unsigned int pr, int level)
	41	+{
	42	+ static const char * const level_name[] =
	43	+ { "ASCE", "PGD", "PUD", "PMD", "PTE" };
	44	+
	45	+ seq_printf(m, "%s ", level_name[level]);
	46	+ if (pr & _PAGE_INVALID)
	47	+ seq_printf(m, "I\n");
	48	+ else
	49	+ seq_printf(m, "%s\n", pr & _PAGE_RO ? "RO" : "RW");
	50	+}
	51	+
	52	+static void note_page(struct seq_file m, struct pg_state st,
	53	+ unsigned int new_prot, int level)
	54	+{
	55	+ static const char units[] = "KMGTPE";
	56	+ int width = sizeof(unsigned long) * 2;
	57	+ const char *unit = units;
	58	+ unsigned int prot, cur;
	59	+ unsigned long delta;
	60	+
	61	+ /*
	62	+ * If we have a "break" in the series, we need to flush the state
	63	+ * that we have now. "break" is either changing perms, levels or
	64	+ * address space marker.
	65	+ */
	66	+ prot = new_prot;
	67	+ cur = st->current_prot;
	68	+
	69	+ if (!st->level) {
	70	+ /* First entry */
	71	+ st->current_prot = new_prot;
	72	+ st->level = level;
	73	+ st->marker = address_markers;
	74	+ seq_printf(m, "---[ %s ]---\n", st->marker->name);
	75	+ } else if (prot != cur \|\| level != st->level \|\|
	76	+ st->current_address >= st->marker[1].start_address) {
	77	+ /* Print the actual finished series */
	78	+ seq_printf(m, "0x%0lx-0x%0lx",
	79	+ width, st->start_address,
	80	+ width, st->current_address);
	81	+ delta = (st->current_address - st->start_address) >> 10;
	82	+ while (!(delta & 0x3ff) && unit[1]) {
	83	+ delta >>= 10;
	84	+ unit++;
	85	+ }
	86	+ seq_printf(m, "%9lu%c ", delta, *unit);
	87	+ print_prot(m, st->current_prot, st->level);
	88	+ if (st->current_address >= st->marker[1].start_address) {
	89	+ st->marker++;
	90	+ seq_printf(m, "---[ %s ]---\n", st->marker->name);
	91	+ }
	92	+ st->start_address = st->current_address;
	93	+ st->current_prot = new_prot;
	94	+ st->level = level;
	95	+ }
	96	+}
	97	+
	98	+/*
	99	+ * The actual page table walker functions. In order to keep the implementation
	100	+ * of print_prot() short, we only check and pass _PAGE_INVALID and _PAGE_RO
	101	+ * flags to note_page() if a region, segment or page table entry is invalid or
	102	+ * read-only.
	103	+ * After all it's just a hint that the current level being walked contains an
	104	+ * invalid or read-only entry.
	105	+ */
	106	+static void walk_pte_level(struct seq_file m, struct pg_state st,
	107	+ pmd_t *pmd, unsigned long addr)
	108	+{
	109	+ unsigned int prot;
	110	+ pte_t *pte;
	111	+ int i;
	112	+
	113	+ for (i = 0; i < PTRS_PER_PTE && addr < max_addr; i++) {
	114	+ st->current_address = addr;
	115	+ pte = pte_offset_kernel(pmd, addr);
	116	+ prot = pte_val(*pte) & (_PAGE_RO \| _PAGE_INVALID);
	117	+ note_page(m, st, prot, 4);
	118	+ addr += PAGE_SIZE;
	119	+ }
	120	+}
	121	+
	122	+static void walk_pmd_level(struct seq_file m, struct pg_state st,
	123	+ pud_t *pud, unsigned long addr)
	124	+{
	125	+ unsigned int prot;
	126	+ pmd_t *pmd;
	127	+ int i;
	128	+
	129	+ for (i = 0; i < PTRS_PER_PMD && addr < max_addr; i++) {
	130	+ st->current_address = addr;
	131	+ pmd = pmd_offset(pud, addr);
	132	+ if (!pmd_none(*pmd)) {
	133	+ if (pmd_large(*pmd)) {
	134	+ prot = pmd_val(*pmd) & _SEGMENT_ENTRY_RO;
	135	+ note_page(m, st, prot, 3);
	136	+ } else
	137	+ walk_pte_level(m, st, pmd, addr);
	138	+ } else
	139	+ note_page(m, st, _PAGE_INVALID, 3);
	140	+ addr += PMD_SIZE;
	141	+ }
	142	+}
	143	+
	144	+static void walk_pud_level(struct seq_file m, struct pg_state st,
	145	+ pgd_t *pgd, unsigned long addr)
	146	+{
	147	+ pud_t *pud;
	148	+ int i;
	149	+
	150	+ for (i = 0; i < PTRS_PER_PUD && addr < max_addr; i++) {
	151	+ st->current_address = addr;
	152	+ pud = pud_offset(pgd, addr);
	153	+ if (!pud_none(*pud))
	154	+ walk_pmd_level(m, st, pud, addr);
	155	+ else
	156	+ note_page(m, st, _PAGE_INVALID, 2);
	157	+ addr += PUD_SIZE;
	158	+ }
	159	+}
	160	+
	161	+static void walk_pgd_level(struct seq_file *m)
	162	+{
	163	+ unsigned long addr = 0;
	164	+ struct pg_state st;
	165	+ pgd_t *pgd;
	166	+ int i;
	167	+
	168	+ memset(&st, 0, sizeof(st));
	169	+ for (i = 0; i < PTRS_PER_PGD && addr < max_addr; i++) {
	170	+ st.current_address = addr;
	171	+ pgd = pgd_offset_k(addr);
	172	+ if (!pgd_none(*pgd))
	173	+ walk_pud_level(m, &st, pgd, addr);
	174	+ else
	175	+ note_page(m, &st, _PAGE_INVALID, 1);
	176	+ addr += PGDIR_SIZE;
	177	+ }
	178	+ /* Flush out the last page */
	179	+ st.current_address = max_addr;
	180	+ note_page(m, &st, 0, 0);
	181	+}
	182	+
	183	+static int ptdump_show(struct seq_file m, void v)
	184	+{
	185	+ walk_pgd_level(m);
	186	+ return 0;
	187	+}
	188	+
	189	+static int ptdump_open(struct inode inode, struct file filp)
	190	+{
	191	+ return single_open(filp, ptdump_show, NULL);
	192	+}
	193	+
	194	+static const struct file_operations ptdump_fops = {
	195	+ .open = ptdump_open,
	196	+ .read = seq_read,
	197	+ .llseek = seq_lseek,
	198	+ .release = single_release,
	199	+};
	200	+
	201	+static int pt_dump_init(void)
	202	+{
	203	+ /*
	204	+ * Figure out the maximum virtual address being accessible with the
	205	+ * kernel ASCE. We need this to keep the page table walker functions
	206	+ * from accessing non-existent entries.
	207	+ */
	208	+#ifdef CONFIG_64BIT
	209	+ max_addr = (S390_lowcore.kernel_asce & _REGION_ENTRY_TYPE_MASK) >> 2;
	210	+ max_addr = 1UL << (max_addr * 11 + 31);
	211	+#else
	212	+ max_addr = 1UL << 31;
	213	+#endif
	214	+ address_markers[VMEMMAP_NR].start_address = (unsigned long) vmemmap;
	215	+ address_markers[VMALLOC_NR].start_address = VMALLOC_START;
	216	+ debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
	217	+ return 0;
	218	+}
	219	+device_initcall(pt_dump_init);