powerpc/mm: Dump hash table

Useful to be able to dump the kernel hash page table to check
which pages are hashed along with their sizes and other details.

Add a debugfs file to check the hash page table. If radix is enabled
(and so there is no hash page table) then this file doesn't exist. To
use this the PPC_PTDUMP config option must be selected.
Signed-off-by: Rashmica Gupta <rashmicy@gmail.com>
[mpe: Fix build with SPARSEMEM_VMEMMAP=n & PSERIES=n]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/Makefile

@@ -42,4 +42,5 @@ obj-$(CONFIG_NOT_COHERENT_CACHE) += dma-noncoherent.o
 obj-$(CONFIG_HIGHMEM)		+= highmem.o
 obj-$(CONFIG_PPC_COPRO_BASE)	+= copro_fault.o
 obj-$(CONFIG_SPAPR_TCE_IOMMU)	+= mmu_context_iommu.o
-obj-$(CONFIG_PPC_PTDUMP)	+= dump_linuxpagetables.o
+obj-$(CONFIG_PPC_PTDUMP)	+= dump_linuxpagetables.o \
+				   dump_hashpagetable.o

arch/powerpc/mm/dump_hashpagetable.c

+/*
+ * Copyright 2016, Rashmica Gupta, IBM Corp.
+ *
+ * This traverses the kernel virtual memory and dumps the pages that are in
+ * the hash pagetable, along with their flags to
+ * /sys/kernel/debug/kernel_hash_pagetable.
+ *
+ * If radix is enabled then there is no hash page table and so no debugfs file
+ * is generated.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+#include <linux/debugfs.h>
+#include <linux/fs.h>
+#include <linux/io.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <asm/fixmap.h>
+#include <asm/pgtable.h>
+#include <linux/const.h>
+#include <asm/page.h>
+#include <asm/pgalloc.h>
+#include <asm/plpar_wrappers.h>
+#include <linux/memblock.h>
+#include <asm/firmware.h>
+
+struct pg_state {
+	struct seq_file *seq;
+	const struct addr_marker *marker;
+	unsigned long start_address;
+	unsigned int level;
+	u64 current_flags;
+};
+
+struct addr_marker {
+	unsigned long start_address;
+	const char *name;
+};
+
+static struct addr_marker address_markers[] = {
+	{ 0,	"Start of kernel VM" },
+	{ 0,	"vmalloc() Area" },
+	{ 0,	"vmalloc() End" },
+	{ 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" },
+	{ -1,	NULL },
+};
+
+struct flag_info {
+	u64		mask;
+	u64		val;
+	const char	*set;
+	const char	*clear;
+	bool		is_val;
+	int		shift;
+};
+
+static const struct flag_info v_flag_array[] = {
+	{
+		.mask   = SLB_VSID_B,
+		.val    = SLB_VSID_B_256M,
+		.set    = "ssize: 256M",
+		.clear  = "ssize: 1T  ",
+	}, {
+		.mask	= HPTE_V_SECONDARY,
+		.val	= HPTE_V_SECONDARY,
+		.set	= "secondary",
+		.clear	= "primary  ",
+	}, {
+		.mask	= HPTE_V_VALID,
+		.val	= HPTE_V_VALID,
+		.set	= "valid  ",
+		.clear	= "invalid",
+	}, {
+		.mask	= HPTE_V_BOLTED,
+		.val	= HPTE_V_BOLTED,
+		.set	= "bolted",
+		.clear	= "",
+	}
+};
+
+static const struct flag_info r_flag_array[] = {
+	{
+		.mask	= HPTE_R_PP0 | HPTE_R_PP,
+		.val	= PP_RWXX,
+		.set	= "prot:RW--",
+	}, {
+		.mask	= HPTE_R_PP0 | HPTE_R_PP,
+		.val	= PP_RWRX,
+		.set	= "prot:RWR-",
+	}, {
+		.mask	= HPTE_R_PP0 | HPTE_R_PP,
+		.val	= PP_RWRW,
+		.set	= "prot:RWRW",
+	}, {
+		.mask	= HPTE_R_PP0 | HPTE_R_PP,
+		.val	= PP_RXRX,
+		.set	= "prot:R-R-",
+	}, {
+		.mask	= HPTE_R_PP0 | HPTE_R_PP,
+		.val	= PP_RXXX,
+		.set	= "prot:R---",
+	}, {
+		.mask	= HPTE_R_KEY_HI | HPTE_R_KEY_LO,
+		.val	= HPTE_R_KEY_HI | HPTE_R_KEY_LO,
+		.set	= "key",
+		.clear	= "",
+		.is_val = true,
+	}, {
+		.mask	= HPTE_R_R,
+		.val	= HPTE_R_R,
+		.set	= "ref",
+		.clear	= "   ",
+	}, {
+		.mask	= HPTE_R_C,
+		.val	= HPTE_R_C,
+		.set	= "changed",
+		.clear	= "       ",
+	}, {
+		.mask	= HPTE_R_N,
+		.val	= HPTE_R_N,
+		.set	= "no execute",
+	}, {
+		.mask	= HPTE_R_WIMG,
+		.val	= HPTE_R_W,
+		.set	= "writethru",
+	}, {
+		.mask	= HPTE_R_WIMG,
+		.val	= HPTE_R_I,
+		.set	= "no cache",
+	}, {
+		.mask	= HPTE_R_WIMG,
+		.val	= HPTE_R_G,
+		.set	= "guarded",
+	}
+};
+
+static int calculate_pagesize(struct pg_state *st, int ps, char s[])
+{
+	static const char units[] = "BKMGTPE";
+	const char *unit = units;
+
+	while (ps > 9 && unit[1]) {
+		ps -= 10;
+		unit++;
+	}
+	seq_printf(st->seq, "  %s_ps: %i%c\t", s, 1<<ps, *unit);
+	return ps;
+}
+
+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;
+			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)
+				seq_printf(st->seq, "  %s", s);
+		}
+	}
+}
+
+static void dump_hpte_info(struct pg_state *st, unsigned long ea, u64 v, u64 r,
+		unsigned long rpn, int bps, int aps, unsigned long lp)
+{
+	int aps_index;
+
+	while (ea >= st->marker[1].start_address) {
+		st->marker++;
+		seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
+	}
+	seq_printf(st->seq, "0x%lx:\t", ea);
+	seq_printf(st->seq, "AVPN:%llx\t", HPTE_V_AVPN_VAL(v));
+	dump_flag_info(st, v_flag_array, v, ARRAY_SIZE(v_flag_array));
+	seq_printf(st->seq, "  rpn: %lx\t", rpn);
+	dump_flag_info(st, r_flag_array, r, ARRAY_SIZE(r_flag_array));
+
+	calculate_pagesize(st, bps, "base");
+	aps_index = calculate_pagesize(st, aps, "actual");
+	if (aps_index != 2)
+		seq_printf(st->seq, "LP enc: %lx", lp);
+	seq_puts(st->seq, "\n");
+}
+
+
+static int native_find(unsigned long ea, int psize, bool primary, u64 *v, u64
+		*r)
+{
+	struct hash_pte *hptep;
+	unsigned long hash, vsid, vpn, hpte_group, want_v, hpte_v;
+	int i, ssize = mmu_kernel_ssize;
+	unsigned long shift = mmu_psize_defs[psize].shift;
+
+	/* calculate hash */
+	vsid = get_kernel_vsid(ea, ssize);
+	vpn  = hpt_vpn(ea, vsid, ssize);
+	hash = hpt_hash(vpn, shift, ssize);
+	want_v = hpte_encode_avpn(vpn, psize, ssize);
+
+	/* to check in the secondary hash table, we invert the hash */
+	if (!primary)
+		hash = ~hash;
+	hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP;
+	for (i = 0; i < HPTES_PER_GROUP; i++) {
+		hptep = htab_address + hpte_group;
+		hpte_v = be64_to_cpu(hptep->v);
+
+		if (HPTE_V_COMPARE(hpte_v, want_v) && (hpte_v & HPTE_V_VALID)) {
+			/* HPTE matches */
+			*v = be64_to_cpu(hptep->v);
+			*r = be64_to_cpu(hptep->r);
+			return 0;
+		}
+		++hpte_group;
+	}
+	return -1;
+}
+
+#ifdef CONFIG_PPC_PSERIES
+static int pseries_find(unsigned long ea, int psize, bool primary, u64 *v, u64 *r)
+{
+	struct hash_pte ptes[4];
+	unsigned long vsid, vpn, hash, hpte_group, want_v;
+	int i, j, ssize = mmu_kernel_ssize;
+	long lpar_rc = 0;
+	unsigned long shift = mmu_psize_defs[psize].shift;
+
+	/* calculate hash */
+	vsid = get_kernel_vsid(ea, ssize);
+	vpn  = hpt_vpn(ea, vsid, ssize);
+	hash = hpt_hash(vpn, shift, ssize);
+	want_v = hpte_encode_avpn(vpn, psize, ssize);
+
+	/* to check in the secondary hash table, we invert the hash */
+	if (!primary)
+		hash = ~hash;
+	hpte_group = ((hash & htab_hash_mask) * HPTES_PER_GROUP) & ~0x7UL;
+	/* see if we can find an entry in the hpte with this hash */
+	for (i = 0; i < HPTES_PER_GROUP; i += 4, hpte_group += 4) {
+		lpar_rc = plpar_pte_read_4(0, hpte_group, (void *)ptes);
+
+		if (lpar_rc != H_SUCCESS)
+			continue;
+		for (j = 0; j < 4; j++) {
+			if (HPTE_V_COMPARE(ptes[j].v, want_v) &&
+					(ptes[j].v & HPTE_V_VALID)) {
+				/* HPTE matches */
+				*v = ptes[j].v;
+				*r = ptes[j].r;
+				return 0;
+			}
+		}
+	}
+	return -1;
+}
+#endif
+
+static void decode_r(int bps, unsigned long r, unsigned long *rpn, int *aps,
+		unsigned long *lp_bits)
+{
+	struct mmu_psize_def entry;
+	unsigned long arpn, mask, lp;
+	int penc = -2, idx = 0, shift;
+
+	/*.
+	 * The LP field has 8 bits. Depending on the actual page size, some of
+	 * these bits are concatenated with the APRN to get the RPN. The rest
+	 * of the bits in the LP field is the LP value and is an encoding for
+	 * the base page size and the actual page size.
+	 *
+	 *  -	find the mmu entry for our base page size
+	 *  -	go through all page encodings and use the associated mask to
+	 *	find an encoding that matches our encoding in the LP field.
+	 */
+	arpn = (r & HPTE_R_RPN) >> HPTE_R_RPN_SHIFT;
+	lp = arpn & 0xff;
+
+	entry = mmu_psize_defs[bps];
+	while (idx < MMU_PAGE_COUNT) {
+		penc = entry.penc[idx];
+		if ((penc != -1) && (mmu_psize_defs[idx].shift)) {
+			shift = mmu_psize_defs[idx].shift -  HPTE_R_RPN_SHIFT;
+			mask = (0x1 << (shift)) - 1;
+			if ((lp & mask) == penc) {
+				*aps = mmu_psize_to_shift(idx);
+				*lp_bits = lp & mask;
+				*rpn = arpn >> shift;
+				return;
+			}
+		}
+		idx++;
+	}
+}
+
+static int base_hpte_find(unsigned long ea, int psize, bool primary, u64 *v,
+			  u64 *r)
+{
+#ifdef CONFIG_PPC_PSERIES
+	if (firmware_has_feature(FW_FEATURE_LPAR))
+		return pseries_find(ea, psize, primary, v, r);
+#endif
+	return native_find(ea, psize, primary, v, r);
+}
+
+static unsigned long hpte_find(struct pg_state *st, unsigned long ea, int psize)
+{
+	unsigned long slot;
+	u64 v  = 0, r = 0;
+	unsigned long rpn, lp_bits;
+	int base_psize = 0, actual_psize = 0;
+
+	if (ea <= PAGE_OFFSET)
+		return -1;
+
+	/* Look in primary table */
+	slot = base_hpte_find(ea, psize, true, &v, &r);
+
+	/* Look in secondary table */
+	if (slot == -1)
+		slot = base_hpte_find(ea, psize, true, &v, &r);
+
+	/* No entry found */
+	if (slot == -1)
+		return -1;
+
+	/*
+	 * We found an entry in the hash page table:
+	 *  - check that this has the same base page
+	 *  - find the actual page size
+	 *  - find the RPN
+	 */
+	base_psize = mmu_psize_to_shift(psize);
+
+	if ((v & HPTE_V_LARGE) == HPTE_V_LARGE) {
+		decode_r(psize, r, &rpn, &actual_psize, &lp_bits);
+	} else {
+		/* 4K actual page size */
+		actual_psize = 12;
+		rpn = (r & HPTE_R_RPN) >> HPTE_R_RPN_SHIFT;
+		/* In this case there are no LP bits */
+		lp_bits = -1;
+	}
+	/*
+	 * We didn't find a matching encoding, so the PTE we found isn't for
+	 * this address.
+	 */
+	if (actual_psize == -1)
+		return -1;
+
+	dump_hpte_info(st, ea, v, r, rpn, base_psize, actual_psize, lp_bits);
+	return 0;
+}
+
+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, pteval, psize;
+	int i, status;
+
+	for (i = 0; i < PTRS_PER_PTE; i++, pte++) {
+		addr = start + i * PAGE_SIZE;
+		pteval = pte_val(*pte);
+
+		if (addr < VMALLOC_END)
+			psize = mmu_vmalloc_psize;
+		else
+			psize = mmu_io_psize;
+#ifdef CONFIG_PPC_64K_PAGES
+		/* check for secret 4K mappings */
+		if (((pteval & H_PAGE_COMBO) == H_PAGE_COMBO) ||
+			((pteval & H_PAGE_4K_PFN) == H_PAGE_4K_PFN))
+			psize = mmu_io_psize;
+#endif
+		/* check for hashpte */
+		status = hpte_find(st, addr, psize);
+
+		if (((pteval & H_PAGE_HASHPTE) != H_PAGE_HASHPTE)
+				&& (status != -1)) {
+		/* found a hpte that is not in the linux page tables */
+			seq_printf(st->seq, "page probably bolted before linux"
+				" pagetables were set: addr:%lx, pteval:%lx\n",
+				addr, pteval);
+		}
+	}
+}
+
+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 exists */
+			walk_pte(st, pmd, addr);
+	}
+}
+
+static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
+{
+	pud_t *pud = pud_offset(pgd, 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 exists */
+			walk_pmd(st, pud, addr);
+	}
+}
+
+static void walk_pagetables(struct pg_state *st)
+{
+	pgd_t *pgd = pgd_offset_k(0UL);
+	unsigned int i;
+	unsigned long addr;
+
+	/*
+	 * Traverse the linux pagetable structure and dump pages that are in
+	 * the hash pagetable.
+	 */
+	for (i = 0; i < PTRS_PER_PGD; i++, pgd++) {
+		addr = KERN_VIRT_START + i * PGDIR_SIZE;
+		if (!pgd_none(*pgd))
+			/* pgd exists */
+			walk_pud(st, pgd, addr);
+	}
+}
+
+
+static void walk_linearmapping(struct pg_state *st)
+{
+	unsigned long addr;
+
+	/*
+	 * Traverse the linear mapping section of virtual memory and dump pages
+	 * that are in the hash pagetable.
+	 */
+	unsigned long psize = 1 << mmu_psize_defs[mmu_linear_psize].shift;
+
+	for (addr = PAGE_OFFSET; addr < PAGE_OFFSET +
+			memblock_phys_mem_size(); addr += psize)
+		hpte_find(st, addr, mmu_linear_psize);
+}
+
+static void walk_vmemmap(struct pg_state *st)
+{
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+	struct vmemmap_backing *ptr = vmemmap_list;
+
+	/*
+	 * Traverse the vmemmaped memory and dump pages that are in the hash
+	 * pagetable.
+	 */
+	while (ptr->list) {
+		hpte_find(st, ptr->virt_addr, mmu_vmemmap_psize);
+		ptr = ptr->list;
+	}
+	seq_puts(st->seq, "---[ vmemmap end ]---\n");
+#endif
+}
+
+static void populate_markers(void)
+{
+	address_markers[0].start_address = PAGE_OFFSET;
+	address_markers[1].start_address = VMALLOC_START;
+	address_markers[2].start_address = VMALLOC_END;
+	address_markers[3].start_address = ISA_IO_BASE;
+	address_markers[4].start_address = ISA_IO_END;
+	address_markers[5].start_address = PHB_IO_BASE;
+	address_markers[6].start_address = PHB_IO_END;
+	address_markers[7].start_address = IOREMAP_BASE;
+	address_markers[8].start_address = IOREMAP_END;
+#ifdef CONFIG_PPC_STD_MMU_64
+	address_markers[9].start_address =  H_VMEMMAP_BASE;
+#else
+	address_markers[9].start_address =  VMEMMAP_BASE;
+#endif
+}
+
+static int ptdump_show(struct seq_file *m, void *v)
+{
+	struct pg_state st = {
+		.seq = m,
+		.start_address = PAGE_OFFSET,
+		.marker = address_markers,
+	};
+	/*
+	 * Traverse the 0xc, 0xd and 0xf areas of the kernel virtual memory and
+	 * dump pages that are in the hash pagetable.
+	 */
+	walk_linearmapping(&st);
+	walk_pagetables(&st);
+	walk_vmemmap(&st);
+	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 int ptdump_init(void)
+{
+	struct dentry *debugfs_file;
+
+	if (!radix_enabled()) {
+		populate_markers();
+		debugfs_file = debugfs_create_file("kernel_hash_pagetable",
+				0400, NULL, NULL, &ptdump_fops);
+		return debugfs_file ? 0 : -ENOMEM;
+	}
+	return 0;
+}
+device_initcall(ptdump_init);