/*
 * page-types: Tool for querying page flags
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should find a copy of v2 of the GNU General Public License somewhere on
 * your Linux system; if not, write to the Free Software Foundation, Inc., 59
 * Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * Copyright (C) 2009 Intel corporation
 *
 * Authors: Wu Fengguang <fengguang.wu@intel.com>
 */

#define _FILE_OFFSET_BITS 64
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdint.h>
#include <stdarg.h>
#include <string.h>
#include <getopt.h>
#include <limits.h>
#include <assert.h>
#include <ftw.h>
#include <time.h>
#include <setjmp.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/errno.h>
#include <sys/fcntl.h>
#include <sys/mount.h>
#include <sys/statfs.h>
#include <sys/mman.h>
#include "../../include/uapi/linux/magic.h"
#include "../../include/uapi/linux/kernel-page-flags.h"
#include <api/fs/debugfs.h>

#ifndef MAX_PATH
# define MAX_PATH 256
#endif

#ifndef STR
# define _STR(x) #x
# define STR(x) _STR(x)
#endif

/*
 * pagemap kernel ABI bits
 */

#define PM_ENTRY_BYTES		8
#define PM_PFRAME_BITS		55
#define PM_PFRAME_MASK		((1LL << PM_PFRAME_BITS) - 1)
#define PM_PFRAME(x)		((x) & PM_PFRAME_MASK)
#define PM_SOFT_DIRTY		(1ULL << 55)
#define PM_MMAP_EXCLUSIVE	(1ULL << 56)
#define PM_FILE			(1ULL << 61)
#define PM_SWAP			(1ULL << 62)
#define PM_PRESENT		(1ULL << 63)

/*
 * kernel page flags
 */

#define KPF_BYTES		8
#define PROC_KPAGEFLAGS		"/proc/kpageflags"

/* [32-] kernel hacking assistances */
#define KPF_RESERVED		32
#define KPF_MLOCKED		33
#define KPF_MAPPEDTODISK	34
#define KPF_PRIVATE		35
#define KPF_PRIVATE_2		36
#define KPF_OWNER_PRIVATE	37
#define KPF_ARCH		38
#define KPF_UNCACHED		39
#define KPF_SOFTDIRTY		40

/* [48-] take some arbitrary free slots for expanding overloaded flags
 * not part of kernel API
 */
#define KPF_READAHEAD		48
#define KPF_SLOB_FREE		49
#define KPF_SLUB_FROZEN		50
#define KPF_SLUB_DEBUG		51
#define KPF_FILE		62
#define KPF_MMAP_EXCLUSIVE	63

#define KPF_ALL_BITS		((uint64_t)~0ULL)
#define KPF_HACKERS_BITS	(0xffffULL << 32)
#define KPF_OVERLOADED_BITS	(0xffffULL << 48)
#define BIT(name)		(1ULL << KPF_##name)
#define BITS_COMPOUND		(BIT(COMPOUND_HEAD) | BIT(COMPOUND_TAIL))

static const char * const page_flag_names[] = {
	[KPF_LOCKED]		= "L:locked",
	[KPF_ERROR]		= "E:error",
	[KPF_REFERENCED]	= "R:referenced",
	[KPF_UPTODATE]		= "U:uptodate",
	[KPF_DIRTY]		= "D:dirty",
	[KPF_LRU]		= "l:lru",
	[KPF_ACTIVE]		= "A:active",
	[KPF_SLAB]		= "S:slab",
	[KPF_WRITEBACK]		= "W:writeback",
	[KPF_RECLAIM]		= "I:reclaim",
	[KPF_BUDDY]		= "B:buddy",

	[KPF_MMAP]		= "M:mmap",
	[KPF_ANON]		= "a:anonymous",
	[KPF_SWAPCACHE]		= "s:swapcache",
	[KPF_SWAPBACKED]	= "b:swapbacked",
	[KPF_COMPOUND_HEAD]	= "H:compound_head",
	[KPF_COMPOUND_TAIL]	= "T:compound_tail",
	[KPF_HUGE]		= "G:huge",
	[KPF_UNEVICTABLE]	= "u:unevictable",
	[KPF_HWPOISON]		= "X:hwpoison",
	[KPF_NOPAGE]		= "n:nopage",
	[KPF_KSM]		= "x:ksm",
	[KPF_THP]		= "t:thp",
	[KPF_BALLOON]		= "o:balloon",
	[KPF_ZERO_PAGE]		= "z:zero_page",

	[KPF_RESERVED]		= "r:reserved",
	[KPF_MLOCKED]		= "m:mlocked",
	[KPF_MAPPEDTODISK]	= "d:mappedtodisk",
	[KPF_PRIVATE]		= "P:private",
	[KPF_PRIVATE_2]		= "p:private_2",
	[KPF_OWNER_PRIVATE]	= "O:owner_private",
	[KPF_ARCH]		= "h:arch",
	[KPF_UNCACHED]		= "c:uncached",
	[KPF_SOFTDIRTY]		= "f:softdirty",

	[KPF_READAHEAD]		= "I:readahead",
	[KPF_SLOB_FREE]		= "P:slob_free",
	[KPF_SLUB_FROZEN]	= "A:slub_frozen",
	[KPF_SLUB_DEBUG]	= "E:slub_debug",

	[KPF_FILE]		= "F:file",
	[KPF_MMAP_EXCLUSIVE]	= "1:mmap_exclusive",
};


static const char * const debugfs_known_mountpoints[] = {
	"/sys/kernel/debug",
	"/debug",
	0,
};

/*
 * data structures
 */

static int		opt_raw;	/* for kernel developers */
static int		opt_list;	/* list pages (in ranges) */
static int		opt_no_summary;	/* don't show summary */
static pid_t		opt_pid;	/* process to walk */
const char *		opt_file;

#define MAX_ADDR_RANGES	1024
static int		nr_addr_ranges;
static unsigned long	opt_offset[MAX_ADDR_RANGES];
static unsigned long	opt_size[MAX_ADDR_RANGES];

#define MAX_VMAS	10240
static int		nr_vmas;
static unsigned long	pg_start[MAX_VMAS];
static unsigned long	pg_end[MAX_VMAS];

#define MAX_BIT_FILTERS	64
static int		nr_bit_filters;
static uint64_t		opt_mask[MAX_BIT_FILTERS];
static uint64_t		opt_bits[MAX_BIT_FILTERS];

static int		page_size;

static int		pagemap_fd;
static int		kpageflags_fd;

static int		opt_hwpoison;
static int		opt_unpoison;

static char		*hwpoison_debug_fs;
static int		hwpoison_inject_fd;
static int		hwpoison_forget_fd;

#define HASH_SHIFT	13
#define HASH_SIZE	(1 << HASH_SHIFT)
#define HASH_MASK	(HASH_SIZE - 1)
#define HASH_KEY(flags)	(flags & HASH_MASK)

static unsigned long	total_pages;
static unsigned long	nr_pages[HASH_SIZE];
static uint64_t		page_flags[HASH_SIZE];


/*
 * helper functions
 */

#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))

#define min_t(type, x, y) ({			\
	type __min1 = (x);			\
	type __min2 = (y);			\
	__min1 < __min2 ? __min1 : __min2; })

#define max_t(type, x, y) ({			\
	type __max1 = (x);			\
	type __max2 = (y);			\
	__max1 > __max2 ? __max1 : __max2; })

static unsigned long pages2mb(unsigned long pages)
{
	return (pages * page_size) >> 20;
}

static void fatal(const char *x, ...)
{
	va_list ap;

	va_start(ap, x);
	vfprintf(stderr, x, ap);
	va_end(ap);
	exit(EXIT_FAILURE);
}

static int checked_open(const char *pathname, int flags)
{
	int fd = open(pathname, flags);

	if (fd < 0) {
		perror(pathname);
		exit(EXIT_FAILURE);
	}

	return fd;
}

/*
 * pagemap/kpageflags routines
 */

static unsigned long do_u64_read(int fd, char *name,
				 uint64_t *buf,
				 unsigned long index,
				 unsigned long count)
{
	long bytes;

	if (index > ULONG_MAX / 8)
		fatal("index overflow: %lu\n", index);

	bytes = pread(fd, buf, count * 8, (off_t)index * 8);
	if (bytes < 0) {
		perror(name);
		exit(EXIT_FAILURE);
	}
	if (bytes % 8)
		fatal("partial read: %lu bytes\n", bytes);

	return bytes / 8;
}

static unsigned long kpageflags_read(uint64_t *buf,
				     unsigned long index,
				     unsigned long pages)
{
	return do_u64_read(kpageflags_fd, PROC_KPAGEFLAGS, buf, index, pages);
}

static unsigned long pagemap_read(uint64_t *buf,
				  unsigned long index,
				  unsigned long pages)
{
	return do_u64_read(pagemap_fd, "/proc/pid/pagemap", buf, index, pages);
}

static unsigned long pagemap_pfn(uint64_t val)
{
	unsigned long pfn;

	if (val & PM_PRESENT)
		pfn = PM_PFRAME(val);
	else
		pfn = 0;

	return pfn;
}


/*
 * page flag names
 */

static char *page_flag_name(uint64_t flags)
{
	static char buf[65];
	int present;
	size_t i, j;

	for (i = 0, j = 0; i < ARRAY_SIZE(page_flag_names); i++) {
		present = (flags >> i) & 1;
		if (!page_flag_names[i]) {
			if (present)
				fatal("unknown flag bit %d\n", i);
			continue;
		}
		buf[j++] = present ? page_flag_names[i][0] : '_';
	}

	return buf;
}

static char *page_flag_longname(uint64_t flags)
{
	static char buf[1024];
	size_t i, n;

	for (i = 0, n = 0; i < ARRAY_SIZE(page_flag_names); i++) {
		if (!page_flag_names[i])
			continue;
		if ((flags >> i) & 1)
			n += snprintf(buf + n, sizeof(buf) - n, "%s,",
					page_flag_names[i] + 2);
	}
	if (n)
		n--;
	buf[n] = '\0';

	return buf;
}


/*
 * page list and summary
 */

static void show_page_range(unsigned long voffset, unsigned long offset,
			    unsigned long size, uint64_t flags)
{
	static uint64_t      flags0;
	static unsigned long voff;
	static unsigned long index;
	static unsigned long count;

	if (flags == flags0 && offset == index + count &&
	    size && voffset == voff + count) {
		count += size;
		return;
	}

	if (count) {
		if (opt_pid)
			printf("%lx\t", voff);
		if (opt_file)
			printf("%lu\t", voff);
		printf("%lx\t%lx\t%s\n",
				index, count, page_flag_name(flags0));
	}

	flags0 = flags;
	index  = offset;
	voff   = voffset;
	count  = size;
}

static void flush_page_range(void)
{
	show_page_range(0, 0, 0, 0);
}

static void show_page(unsigned long voffset,
		      unsigned long offset, uint64_t flags)
{
	if (opt_pid)
		printf("%lx\t", voffset);
	if (opt_file)
		printf("%lu\t", voffset);
	printf("%lx\t%s\n", offset, page_flag_name(flags));
}

static void show_summary(void)
{
	size_t i;

	printf("             flags\tpage-count       MB"
		"  symbolic-flags\t\t\tlong-symbolic-flags\n");

	for (i = 0; i < ARRAY_SIZE(nr_pages); i++) {
		if (nr_pages[i])
			printf("0x%016llx\t%10lu %8lu  %s\t%s\n",
				(unsigned long long)page_flags[i],
				nr_pages[i],
				pages2mb(nr_pages[i]),
				page_flag_name(page_flags[i]),
				page_flag_longname(page_flags[i]));
	}

	printf("             total\t%10lu %8lu\n",
			total_pages, pages2mb(total_pages));
}


/*
 * page flag filters
 */

static int bit_mask_ok(uint64_t flags)
{
	int i;

	for (i = 0; i < nr_bit_filters; i++) {
		if (opt_bits[i] == KPF_ALL_BITS) {
			if ((flags & opt_mask[i]) == 0)
				return 0;
		} else {
			if ((flags & opt_mask[i]) != opt_bits[i])
				return 0;
		}
	}

	return 1;
}

static uint64_t expand_overloaded_flags(uint64_t flags, uint64_t pme)
{
	/* SLOB/SLUB overload several page flags */
	if (flags & BIT(SLAB)) {
		if (flags & BIT(PRIVATE))
			flags ^= BIT(PRIVATE) | BIT(SLOB_FREE);
		if (flags & BIT(ACTIVE))
			flags ^= BIT(ACTIVE) | BIT(SLUB_FROZEN);
		if (flags & BIT(ERROR))
			flags ^= BIT(ERROR) | BIT(SLUB_DEBUG);
	}

	/* PG_reclaim is overloaded as PG_readahead in the read path */
	if ((flags & (BIT(RECLAIM) | BIT(WRITEBACK))) == BIT(RECLAIM))
		flags ^= BIT(RECLAIM) | BIT(READAHEAD);

	if (pme & PM_SOFT_DIRTY)
		flags |= BIT(SOFTDIRTY);
	if (pme & PM_FILE)
		flags |= BIT(FILE);
	if (pme & PM_MMAP_EXCLUSIVE)
		flags |= BIT(MMAP_EXCLUSIVE);

	return flags;
}

static uint64_t well_known_flags(uint64_t flags)
{
	/* hide flags intended only for kernel hacker */
	flags &= ~KPF_HACKERS_BITS;

	/* hide non-hugeTLB compound pages */
	if ((flags & BITS_COMPOUND) && !(flags & BIT(HUGE)))
		flags &= ~BITS_COMPOUND;

	return flags;
}

static uint64_t kpageflags_flags(uint64_t flags, uint64_t pme)
{
	if (opt_raw)
		flags = expand_overloaded_flags(flags, pme);
	else
		flags = well_known_flags(flags);

	return flags;
}

/*
 * page actions
 */

static void prepare_hwpoison_fd(void)
{
	char buf[MAX_PATH + 1];

	hwpoison_debug_fs = debugfs_mount(NULL);
	if (!hwpoison_debug_fs) {
		perror("mount debugfs");
		exit(EXIT_FAILURE);
	}

	if (opt_hwpoison && !hwpoison_inject_fd) {
		snprintf(buf, MAX_PATH, "%s/hwpoison/corrupt-pfn",
			hwpoison_debug_fs);
		hwpoison_inject_fd = checked_open(buf, O_WRONLY);
	}

	if (opt_unpoison && !hwpoison_forget_fd) {
		snprintf(buf, MAX_PATH, "%s/hwpoison/unpoison-pfn",
			hwpoison_debug_fs);
		hwpoison_forget_fd = checked_open(buf, O_WRONLY);
	}
}

static int hwpoison_page(unsigned long offset)
{
	char buf[100];
	int len;

	len = sprintf(buf, "0x%lx\n", offset);
	len = write(hwpoison_inject_fd, buf, len);
	if (len < 0) {
		perror("hwpoison inject");
		return len;
	}
	return 0;
}

static int unpoison_page(unsigned long offset)
{
	char buf[100];
	int len;

	len = sprintf(buf, "0x%lx\n", offset);
	len = write(hwpoison_forget_fd, buf, len);
	if (len < 0) {
		perror("hwpoison forget");
		return len;
	}
	return 0;
}

/*
 * page frame walker
 */

static size_t hash_slot(uint64_t flags)
{
	size_t k = HASH_KEY(flags);
	size_t i;

	/* Explicitly reserve slot 0 for flags 0: the following logic
	 * cannot distinguish an unoccupied slot from slot (flags==0).
	 */
	if (flags == 0)
		return 0;

	/* search through the remaining (HASH_SIZE-1) slots */
	for (i = 1; i < ARRAY_SIZE(page_flags); i++, k++) {
		if (!k || k >= ARRAY_SIZE(page_flags))
			k = 1;
		if (page_flags[k] == 0) {
			page_flags[k] = flags;
			return k;
		}
		if (page_flags[k] == flags)
			return k;
	}

	fatal("hash table full: bump up HASH_SHIFT?\n");
	exit(EXIT_FAILURE);
}

static void add_page(unsigned long voffset,
		     unsigned long offset, uint64_t flags, uint64_t pme)
{
	flags = kpageflags_flags(flags, pme);

	if (!bit_mask_ok(flags))
		return;

	if (opt_hwpoison)
		hwpoison_page(offset);
	if (opt_unpoison)
		unpoison_page(offset);

	if (opt_list == 1)
		show_page_range(voffset, offset, 1, flags);
	else if (opt_list == 2)
		show_page(voffset, offset, flags);

	nr_pages[hash_slot(flags)]++;
	total_pages++;
}

#define KPAGEFLAGS_BATCH	(64 << 10)	/* 64k pages */
static void walk_pfn(unsigned long voffset,
		     unsigned long index,
		     unsigned long count,
		     uint64_t pme)
{
	uint64_t buf[KPAGEFLAGS_BATCH];
	unsigned long batch;
	unsigned long pages;
	unsigned long i;

	while (count) {
		batch = min_t(unsigned long, count, KPAGEFLAGS_BATCH);
		pages = kpageflags_read(buf, index, batch);
		if (pages == 0)
			break;

		for (i = 0; i < pages; i++)
			add_page(voffset + i, index + i, buf[i], pme);

		index += pages;
		count -= pages;
	}
}

#define PAGEMAP_BATCH	(64 << 10)
static void walk_vma(unsigned long index, unsigned long count)
{
	uint64_t buf[PAGEMAP_BATCH];
	unsigned long batch;
	unsigned long pages;
	unsigned long pfn;
	unsigned long i;

	while (count) {
		batch = min_t(unsigned long, count, PAGEMAP_BATCH);
		pages = pagemap_read(buf, index, batch);
		if (pages == 0)
			break;

		for (i = 0; i < pages; i++) {
			pfn = pagemap_pfn(buf[i]);
			if (pfn)
				walk_pfn(index + i, pfn, 1, buf[i]);
		}

		index += pages;
		count -= pages;
	}
}

static void walk_task(unsigned long index, unsigned long count)
{
	const unsigned long end = index + count;
	unsigned long start;
	int i = 0;

	while (index < end) {

		while (pg_end[i] <= index)
			if (++i >= nr_vmas)
				return;
		if (pg_start[i] >= end)
			return;

		start = max_t(unsigned long, pg_start[i], index);
		index = min_t(unsigned long, pg_end[i], end);

		assert(start < index);
		walk_vma(start, index - start);
	}
}

static void add_addr_range(unsigned long offset, unsigned long size)
{
	if (nr_addr_ranges >= MAX_ADDR_RANGES)
		fatal("too many addr ranges\n");

	opt_offset[nr_addr_ranges] = offset;
	opt_size[nr_addr_ranges] = min_t(unsigned long, size, ULONG_MAX-offset);
	nr_addr_ranges++;
}

static void walk_addr_ranges(void)
{
	int i;

	kpageflags_fd = checked_open(PROC_KPAGEFLAGS, O_RDONLY);

	if (!nr_addr_ranges)
		add_addr_range(0, ULONG_MAX);

	for (i = 0; i < nr_addr_ranges; i++)
		if (!opt_pid)
			walk_pfn(opt_offset[i], opt_offset[i], opt_size[i], 0);
		else
			walk_task(opt_offset[i], opt_size[i]);

	close(kpageflags_fd);
}


/*
 * user interface
 */

static const char *page_flag_type(uint64_t flag)
{
	if (flag & KPF_HACKERS_BITS)
		return "(r)";
	if (flag & KPF_OVERLOADED_BITS)
		return "(o)";
	return "   ";
}

static void usage(void)
{
	size_t i, j;

	printf(
"page-types [options]\n"
"            -r|--raw                   Raw mode, for kernel developers\n"
"            -d|--describe flags        Describe flags\n"
"            -a|--addr    addr-spec     Walk a range of pages\n"
"            -b|--bits    bits-spec     Walk pages with specified bits\n"
"            -p|--pid     pid           Walk process address space\n"
"            -f|--file    filename      Walk file address space\n"
"            -l|--list                  Show page details in ranges\n"
"            -L|--list-each             Show page details one by one\n"
"            -N|--no-summary            Don't show summary info\n"
"            -X|--hwpoison              hwpoison pages\n"
"            -x|--unpoison              unpoison pages\n"
"            -h|--help                  Show this usage message\n"
"flags:\n"
"            0x10                       bitfield format, e.g.\n"
"            anon                       bit-name, e.g.\n"
"            0x10,anon                  comma-separated list, e.g.\n"
"addr-spec:\n"
"            N                          one page at offset N (unit: pages)\n"
"            N+M                        pages range from N to N+M-1\n"
"            N,M                        pages range from N to M-1\n"
"            N,                         pages range from N to end\n"
"            ,M                         pages range from 0 to M-1\n"
"bits-spec:\n"
"            bit1,bit2                  (flags & (bit1|bit2)) != 0\n"
"            bit1,bit2=bit1             (flags & (bit1|bit2)) == bit1\n"
"            bit1,~bit2                 (flags & (bit1|bit2)) == bit1\n"
"            =bit1,bit2                 flags == (bit1|bit2)\n"
"bit-names:\n"
	);

	for (i = 0, j = 0; i < ARRAY_SIZE(page_flag_names); i++) {
		if (!page_flag_names[i])
			continue;
		printf("%16s%s", page_flag_names[i] + 2,
				 page_flag_type(1ULL << i));
		if (++j > 3) {
			j = 0;
			putchar('\n');
		}
	}
	printf("\n                                   "
		"(r) raw mode bits  (o) overloaded bits\n");
}

static unsigned long long parse_number(const char *str)
{
	unsigned long long n;

	n = strtoll(str, NULL, 0);

	if (n == 0 && str[0] != '0')
		fatal("invalid name or number: %s\n", str);

	return n;
}

static void parse_pid(const char *str)
{
	FILE *file;
	char buf[5000];

	opt_pid = parse_number(str);

	sprintf(buf, "/proc/%d/pagemap", opt_pid);
	pagemap_fd = checked_open(buf, O_RDONLY);

	sprintf(buf, "/proc/%d/maps", opt_pid);
	file = fopen(buf, "r");
	if (!file) {
		perror(buf);
		exit(EXIT_FAILURE);
	}

	while (fgets(buf, sizeof(buf), file) != NULL) {
		unsigned long vm_start;
		unsigned long vm_end;
		unsigned long long pgoff;
		int major, minor;
		char r, w, x, s;
		unsigned long ino;
		int n;

		n = sscanf(buf, "%lx-%lx %c%c%c%c %llx %x:%x %lu",
			   &vm_start,
			   &vm_end,
			   &r, &w, &x, &s,
			   &pgoff,
			   &major, &minor,
			   &ino);
		if (n < 10) {
			fprintf(stderr, "unexpected line: %s\n", buf);
			continue;
		}
		pg_start[nr_vmas] = vm_start / page_size;
		pg_end[nr_vmas] = vm_end / page_size;
		if (++nr_vmas >= MAX_VMAS) {
			fprintf(stderr, "too many VMAs\n");
			break;
		}
	}
	fclose(file);
}

static void show_file(const char *name, const struct stat *st)
{
	unsigned long long size = st->st_size;
	char atime[64], mtime[64];
	long now = time(NULL);

	printf("%s\tInode: %u\tSize: %llu (%llu pages)\n",
			name, (unsigned)st->st_ino,
			size, (size + page_size - 1) / page_size);

	strftime(atime, sizeof(atime), "%c", localtime(&st->st_atime));
	strftime(mtime, sizeof(mtime), "%c", localtime(&st->st_mtime));

	printf("Modify: %s (%ld seconds ago)\nAccess: %s (%ld seconds ago)\n",
			mtime, now - st->st_mtime,
			atime, now - st->st_atime);
}

static sigjmp_buf sigbus_jmp;

static void * volatile sigbus_addr;

static void sigbus_handler(int sig, siginfo_t *info, void *ucontex)
{
	(void)sig;
	(void)ucontex;
	sigbus_addr = info ? info->si_addr : NULL;
	siglongjmp(sigbus_jmp, 1);
}

static struct sigaction sigbus_action = {
	.sa_sigaction = sigbus_handler,
	.sa_flags = SA_SIGINFO,
};

static void walk_file(const char *name, const struct stat *st)
{
	uint8_t vec[PAGEMAP_BATCH];
	uint64_t buf[PAGEMAP_BATCH], flags;
	unsigned long nr_pages, pfn, i;
	off_t off, end = st->st_size;
	int fd;
	ssize_t len;
	void *ptr;
	int first = 1;

	fd = checked_open(name, O_RDONLY|O_NOATIME|O_NOFOLLOW);

	for (off = 0; off < end; off += len) {
		nr_pages = (end - off + page_size - 1) / page_size;
		if (nr_pages > PAGEMAP_BATCH)
			nr_pages = PAGEMAP_BATCH;
		len = nr_pages * page_size;

		ptr = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, off);
		if (ptr == MAP_FAILED)
			fatal("mmap failed: %s", name);

		/* determine cached pages */
		if (mincore(ptr, len, vec))
			fatal("mincore failed: %s", name);

		/* turn off readahead */
		if (madvise(ptr, len, MADV_RANDOM))
			fatal("madvice failed: %s", name);

		if (sigsetjmp(sigbus_jmp, 1)) {
			end = off + sigbus_addr ? sigbus_addr - ptr : 0;
			fprintf(stderr, "got sigbus at offset %lld: %s\n",
					(long long)end, name);
			goto got_sigbus;
		}

		/* populate ptes */
		for (i = 0; i < nr_pages ; i++) {
			if (vec[i] & 1)
				(void)*(volatile int *)(ptr + i * page_size);
		}
got_sigbus:

		/* turn off harvesting reference bits */
		if (madvise(ptr, len, MADV_SEQUENTIAL))
			fatal("madvice failed: %s", name);

		if (pagemap_read(buf, (unsigned long)ptr / page_size,
					nr_pages) != nr_pages)
			fatal("cannot read pagemap");

		munmap(ptr, len);

		for (i = 0; i < nr_pages; i++) {
			pfn = pagemap_pfn(buf[i]);
			if (!pfn)
				continue;
			if (!kpageflags_read(&flags, pfn, 1))
				continue;
			if (first && opt_list) {
				first = 0;
				flush_page_range();
				show_file(name, st);
			}
			add_page(off / page_size + i, pfn, flags, buf[i]);
		}
	}

	close(fd);
}

int walk_tree(const char *name, const struct stat *st, int type, struct FTW *f)
{
	(void)f;
	switch (type) {
	case FTW_F:
		if (S_ISREG(st->st_mode))
			walk_file(name, st);
		break;
	case FTW_DNR:
		fprintf(stderr, "cannot read dir: %s\n", name);
		break;
	}
	return 0;
}

static void walk_page_cache(void)
{
	struct stat st;

	kpageflags_fd = checked_open(PROC_KPAGEFLAGS, O_RDONLY);
	pagemap_fd = checked_open("/proc/self/pagemap", O_RDONLY);
	sigaction(SIGBUS, &sigbus_action, NULL);

	if (stat(opt_file, &st))
		fatal("stat failed: %s\n", opt_file);

	if (S_ISREG(st.st_mode)) {
		walk_file(opt_file, &st);
	} else if (S_ISDIR(st.st_mode)) {
		/* do not follow symlinks and mountpoints */
		if (nftw(opt_file, walk_tree, 64, FTW_MOUNT | FTW_PHYS) < 0)
			fatal("nftw failed: %s\n", opt_file);
	} else
		fatal("unhandled file type: %s\n", opt_file);

	close(kpageflags_fd);
	close(pagemap_fd);
	signal(SIGBUS, SIG_DFL);
}

static void parse_file(const char *name)
{
	opt_file = name;
}

static void parse_addr_range(const char *optarg)
{
	unsigned long offset;
	unsigned long size;
	char *p;

	p = strchr(optarg, ',');
	if (!p)
		p = strchr(optarg, '+');

	if (p == optarg) {
		offset = 0;
		size   = parse_number(p + 1);
	} else if (p) {
		offset = parse_number(optarg);
		if (p[1] == '\0')
			size = ULONG_MAX;
		else {
			size = parse_number(p + 1);
			if (*p == ',') {
				if (size < offset)
					fatal("invalid range: %lu,%lu\n",
							offset, size);
				size -= offset;
			}
		}
	} else {
		offset = parse_number(optarg);
		size   = 1;
	}

	add_addr_range(offset, size);
}

static void add_bits_filter(uint64_t mask, uint64_t bits)
{
	if (nr_bit_filters >= MAX_BIT_FILTERS)
		fatal("too much bit filters\n");

	opt_mask[nr_bit_filters] = mask;
	opt_bits[nr_bit_filters] = bits;
	nr_bit_filters++;
}

static uint64_t parse_flag_name(const char *str, int len)
{
	size_t i;

	if (!*str || !len)
		return 0;

	if (len <= 8 && !strncmp(str, "compound", len))
		return BITS_COMPOUND;

	for (i = 0; i < ARRAY_SIZE(page_flag_names); i++) {
		if (!page_flag_names[i])
			continue;
		if (!strncmp(str, page_flag_names[i] + 2, len))
			return 1ULL << i;
	}

	return parse_number(str);
}

static uint64_t parse_flag_names(const char *str, int all)
{
	const char *p    = str;
	uint64_t   flags = 0;

	while (1) {
		if (*p == ',' || *p == '=' || *p == '\0') {
			if ((*str != '~') || (*str == '~' && all && *++str))
				flags |= parse_flag_name(str, p - str);
			if (*p != ',')
				break;
			str = p + 1;
		}
		p++;
	}

	return flags;
}

static void parse_bits_mask(const char *optarg)
{
	uint64_t mask;
	uint64_t bits;
	const char *p;

	p = strchr(optarg, '=');
	if (p == optarg) {
		mask = KPF_ALL_BITS;
		bits = parse_flag_names(p + 1, 0);
	} else if (p) {
		mask = parse_flag_names(optarg, 0);
		bits = parse_flag_names(p + 1, 0);
	} else if (strchr(optarg, '~')) {
		mask = parse_flag_names(optarg, 1);
		bits = parse_flag_names(optarg, 0);
	} else {
		mask = parse_flag_names(optarg, 0);
		bits = KPF_ALL_BITS;
	}

	add_bits_filter(mask, bits);
}

static void describe_flags(const char *optarg)
{
	uint64_t flags = parse_flag_names(optarg, 0);

	printf("0x%016llx\t%s\t%s\n",
		(unsigned long long)flags,
		page_flag_name(flags),
		page_flag_longname(flags));
}

static const struct option opts[] = {
	{ "raw"       , 0, NULL, 'r' },
	{ "pid"       , 1, NULL, 'p' },
	{ "file"      , 1, NULL, 'f' },
	{ "addr"      , 1, NULL, 'a' },
	{ "bits"      , 1, NULL, 'b' },
	{ "describe"  , 1, NULL, 'd' },
	{ "list"      , 0, NULL, 'l' },
	{ "list-each" , 0, NULL, 'L' },
	{ "no-summary", 0, NULL, 'N' },
	{ "hwpoison"  , 0, NULL, 'X' },
	{ "unpoison"  , 0, NULL, 'x' },
	{ "help"      , 0, NULL, 'h' },
	{ NULL        , 0, NULL, 0 }
};

int main(int argc, char *argv[])
{
	int c;

	page_size = getpagesize();

	while ((c = getopt_long(argc, argv,
				"rp:f:a:b:d:lLNXxh", opts, NULL)) != -1) {
		switch (c) {
		case 'r':
			opt_raw = 1;
			break;
		case 'p':
			parse_pid(optarg);
			break;
		case 'f':
			parse_file(optarg);
			break;
		case 'a':
			parse_addr_range(optarg);
			break;
		case 'b':
			parse_bits_mask(optarg);
			break;
		case 'd':
			describe_flags(optarg);
			exit(0);
		case 'l':
			opt_list = 1;
			break;
		case 'L':
			opt_list = 2;
			break;
		case 'N':
			opt_no_summary = 1;
			break;
		case 'X':
			opt_hwpoison = 1;
			prepare_hwpoison_fd();
			break;
		case 'x':
			opt_unpoison = 1;
			prepare_hwpoison_fd();
			break;
		case 'h':
			usage();
			exit(0);
		default:
			usage();
			exit(1);
		}
	}

	if (opt_list && opt_pid)
		printf("voffset\t");
	if (opt_list && opt_file)
		printf("foffset\t");
	if (opt_list == 1)
		printf("offset\tlen\tflags\n");
	if (opt_list == 2)
		printf("offset\tflags\n");

	if (opt_file)
		walk_page_cache();
	else
		walk_addr_ranges();

	if (opt_list == 1)
		flush_page_range();

	if (opt_no_summary)
		return 0;

	if (opt_list)
		printf("\n\n");

	show_summary();

	return 0;
}