1. 코드 분석

1. tlpi-dist/mmap/mmcat.c

1. 코드

/* mmcat.c

   Use mmap() plus write() to display the contents of a file (specified
   as a command-line argument) on standard output.
*/
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "tlpi_hdr.h"

int
main(int argc, char *argv[])
{
    char *addr;
    int fd;
    struct stat sb;

    if (argc != 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s file\n", argv[0]);

    fd = open(argv[1], O_RDONLY);
    if (fd == -1)
        errExit("open");

    /* Obtain the size of the file and use it to specify the size of
       the mapping and the size of the buffer to be written */

    if (fstat(fd, &sb) == -1)
        errExit("fstat");

    /* Handle zero-length file specially, since specifying a size of
       zero to mmap() will fail with the error EINVAL */

    if (sb.st_size == 0)
        exit(EXIT_SUCCESS);

    addr = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    if (addr == MAP_FAILED)
        errExit("mmap");

    if (write(STDOUT_FILENO, addr, sb.st_size) != sb.st_size)
        fatal("partial/failed write");
    exit(EXIT_SUCCESS);
}

2. 동작 모습

3. 디버깅 및 분석

2. tlpi-dist/mmap/t_mmap.c

1. 코드

/* t_mmap.c

   Demonstrate the use of mmap() to create a shared file mapping.
*/
#include <sys/mman.h>
#include <fcntl.h>
#include "tlpi_hdr.h"

#define MEM_SIZE 10

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

    if (argc < 2 || strcmp(argv[1], "--help") == 0)
        usageErr("%s file [new-value]\n", argv[0]);

    fd = open(argv[1], O_RDWR);
    if (fd == -1)
        errExit("open");

    addr = mmap(NULL, MEM_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (addr == MAP_FAILED)
        errExit("mmap");

    if (close(fd) == -1)                /* No longer need 'fd' */
        errExit("close");

    printf("Current string=%.*s\n", MEM_SIZE, addr);
                        /* Secure practice: output at most MEM_SIZE bytes */

    if (argc > 2) {                     /* Update contents of region */
        if (strlen(argv[2]) >= MEM_SIZE)
            cmdLineErr("'new-value' too large\n");

        memset(addr, 0, MEM_SIZE);      /* Zero out region */
        strncpy(addr, argv[2], MEM_SIZE - 1);
        if (msync(addr, MEM_SIZE, MS_SYNC) == -1)
            errExit("msync");

        printf("Copied \"%s\" to shared memory\n", argv[2]);
    }

    exit(EXIT_SUCCESS);
}

2. 동작 모습

3. 디버깅 및 분석

3. tlpi-dist/vmem/t_mprotect.c

1. 코드

/* t_mprotect.c

   Demonstrate the use of mprotect() to change the protection on
   a region of memory.

   This program is Linux-specific.
*/
#define _BSD_SOURCE         /* Get MAP_ANONYMOUS definition from <sys/mman.h> */
#include <sys/mman.h>
#include "tlpi_hdr.h"

#define LEN (1024 * 1024)

#define SHELL_FMT "cat /proc/%ld/maps | grep zero"
#define CMD_SIZE (sizeof(SHELL_FMT) + 20)
                            /* Allow extra space for integer string */

int
main(int argc, char *argv[])
{
    char cmd[CMD_SIZE];
    char *addr;

    /* Create an anonymous mapping with all access denied */

    addr = mmap(NULL, LEN, PROT_NONE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
    if (addr == MAP_FAILED)
        errExit("mmap");

    /* Display line from /proc/self/maps corresponding to mapping */

    printf("Before mprotect()\n");
    snprintf(cmd, CMD_SIZE, SHELL_FMT, (long) getpid());
    system(cmd);

    /* Change protection on memory to allow read and write access */

    if (mprotect(addr, LEN, PROT_READ | PROT_WRITE) == -1)
        errExit("mprotect");

    printf("After mprotect()\n");
    system(cmd);                /* Review protection via /proc/self/maps */

    exit(EXIT_SUCCESS);
}

2. 동작 모습

3. 디버깅 및 분석

4. tlpi-dist/vmem/memlock.c

1. 코드

/* memlock.c

   Demonstrate the use of mlock(), to place memory locks, and mincore(), to
   retrieve memory-residence information about the calling processes virtual
   memory pages.

   Note: some UNIX implementations do not provide mincore().

   The madvise() system call is supported on Linux since kernel 2.4.
*/
#define _BSD_SOURCE             /* Get mincore() declaration and MAP_ANONYMOUS
                                   definition from <sys/mman.h> */
#include <sys/mman.h>
#include "tlpi_hdr.h"

/* Display residency of pages in range [addr .. (addr + length - 1)] */

static void
displayMincore(char *addr, size_t length)
{
    unsigned char *vec;
    long pageSize, numPages, j;

#ifndef _SC_PAGESIZE
    pageSize = getpagesize();   /* Some systems don't have _SC_PAGESIZE */
#else
    pageSize = sysconf(_SC_PAGESIZE);
#endif

    numPages = (length + pageSize - 1) / pageSize;
    vec = malloc(numPages);
    if (vec == NULL)
        errExit("malloc");

    if (mincore(addr, length, vec) == -1)
        errExit("mincore");

    for (j = 0; j < numPages; j++) {
        if (j % 64 == 0)
            printf("%s%10p: ", (j == 0) ? "" : "\n", addr + (j * pageSize));
        printf("%c", (vec[j] & 1) ? '*' : '.');
    }
    printf("\n");

    free(vec);
}

int
main(int argc, char *argv[])
{
    char *addr;
    size_t len, lockLen;
    long pageSize, stepSize, j;

    if (argc != 4 || strcmp(argv[1], "--help") == 0)
        usageErr("%s num-pages lock-page-step lock-page-len\n", argv[0]);

#ifndef _SC_PAGESIZE
    pageSize = getpagesize();
    if (pageSize == -1)
        errExit("getpagesize");
#else
    pageSize = sysconf(_SC_PAGESIZE);
    if (pageSize == -1)
        errExit("sysconf(_SC_PAGESIZE)");
#endif

    len =      getInt(argv[1], GN_GT_0, "num-pages") * pageSize;
    stepSize = getInt(argv[2], GN_GT_0, "lock-page-step") * pageSize;
    lockLen =  getInt(argv[3], GN_GT_0, "lock-page-len") * pageSize;

    addr = mmap(NULL, len, PROT_READ, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
    if (addr == MAP_FAILED)
        errExit("mmap");

    printf("Allocated %ld (%#lx) bytes starting at %p\n",
            (long) len, (unsigned long) len, addr);

    printf("Before mlock:\n");
    displayMincore(addr, len);

    /* Lock pages specified by command-line arguments into memory */

    for (j = 0; j + lockLen <= len; j += stepSize)
        if (mlock(addr + j, lockLen) == -1)
            errExit("mlock");

    printf("After mlock:\n");
    displayMincore(addr, len);

    exit(EXIT_SUCCESS);
}

2. 동작 모습

3. 디버깅 및 분석