wiki:Dev/KernelHack/COINS/worklog/201110

10/05

trace getpid() syscall with GDB

  • windell57:x86_64 s0711489$ gdb
    (gdb) set logging file gdb.getpid.log
    (gdb) set logging on
    Copying output to gdb.getpid.log.
    (gdb) file vmlinux
    Reading symbols from /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/vmlinux...(no debugging symbols found)...done.
    (gdb) b sys_getpid
    Breakpoint 1 at 0xffffffff81048ce4: file kernel/timer.c, line 1344.
    (gdb) target remote localhost:8864
    Remote debugging using localhost:8864
    0xffffffff810097a9 in native_safe_halt ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/irqflags.h:49
    49              asm volatile("sti; hlt": : :"memory");
    (gdb) c
    Continuing.
    
    Breakpoint 1, sys_getpid () at kernel/timer.c:1344
    
  • => attachment:gdb.getpid.log
  • on VM guest
    • s0711489@ubuntu-lucid64:~/coursework/KernelHack/02$ ./getpid
      getpid() -> 2143
      

trace log with source list and print data

  • windell57:x86_64 s0711489$ gdb
    (gdb) file vmlinux
    Reading symbols from /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/vmlinux...(no debugging symbols found)...done.
    (gdb) b sys_getpid
    Breakpoint 1 at 0xffffffff81048ce4: file kernel/timer.c, line 1344.
    (gdb) target remote localhost:8864
    Remote debugging using localhost:8864
    0xffffffff810097a9 in native_safe_halt ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/irqflags.h:49
    49              asm volatile("sti; hlt": : :"memory");
    (gdb) c
    Continuing.
    
    Breakpoint 1, sys_getpid () at kernel/timer.c:1344
    1344    {
    (gdb) bt
    #0  sys_getpid () at kernel/timer.c:1344
    #1  0xffffffff810029eb in ?? ()
    #2  0x0000000000000246 in ?? ()
    #3  0x00007fff70d418e0 in ?? ()
    #4  0x00007f6c11b19210 in ?? ()
    #5  0x00007f6c11b05300 in ?? ()
    #6  0x0000000000000027 in ?? ()
    #7  0x0000000000000000 in ?? ()
    (gdb) l
    1339     * which case the tgid is the same in all threads of the same group.
    1340     *
    1341     * This is SMP safe as current->tgid does not change.
    1342     */
    1343    SYSCALL_DEFINE0(getpid)
    1344    {
    1345            return task_tgid_vnr(current);
    1346    }
    1347
    1348    /*
    (gdb) s
    1345            return task_tgid_vnr(current);
    (gdb)
    get_current ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/current.h:14
    14              return percpu_read_stable(current_task);
    (gdb) l
    9
    10      DECLARE_PER_CPU(struct task_struct *, current_task);
    11
    12      static __always_inline struct task_struct *get_current(void)
    13      {
    14              return percpu_read_stable(current_task);
    15      }
    16
    17      #define current get_current()
    18
    (gdb) bt
    #0  get_current ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/current.h:14
    #1  sys_getpid () at kernel/timer.c:1345
    #2  0xffffffff810029eb in ?? ()
    #3  0x0000000000000246 in ?? ()
    #4  0x00007fff63204890 in ?? ()
    #5  0x00007fc615a98210 in ?? ()
    #6  0x00007fc615a84300 in ?? ()
    #7  0x0000000000000027 in ?? ()
    #8  0x0000000000000000 in ?? ()
    (gdb) p current_task
    Cannot access memory at address 0xb540
    (gdb) ptype current_task
    type = struct task_struct {
    
    (snip)
    
    (gdb) s
    sys_getpid () at kernel/timer.c:1344
    1344    {
    (gdb) l
    1339     * which case the tgid is the same in all threads of the same group.
    1340     *
    1341     * This is SMP safe as current->tgid does not change.
    1342     */
    1343    SYSCALL_DEFINE0(getpid)
    1344    {
    1345            return task_tgid_vnr(current);
    1346    }
    1347
    1348    /*
    (gdb) bt
    #0  sys_getpid () at kernel/timer.c:1344
    #1  0xffffffff810029eb in ?? ()
    #2  0x0000000000000246 in ?? ()
    #3  0x00007fff63204890 in ?? ()
    #4  0x00007fc615a98210 in ?? ()
    #5  0x00007fc615a84300 in ?? ()
    #6  0x0000000000000027 in ?? ()
    #7  0x0000000000000000 in ?? ()
    (gdb) s
    1345            return task_tgid_vnr(current);
    (gdb) s
    task_tgid_vnr (tsk=0xffff88001bbe5880) at include/linux/sched.h:1606
    1606    {
    (gdb) l
    1601    }
    1602
    1603    pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns);
    1604
    1605    static inline pid_t task_tgid_vnr(struct task_struct *tsk)
    1606    {
    1607            return pid_vnr(task_tgid(tsk));
    1608    }
    1609
    1610
    (gdb) bt
    #0  task_tgid_vnr (tsk=0xffff88001bbe5880) at include/linux/sched.h:1606
    #1  0xffffffff81048cf6 in sys_getpid () at kernel/timer.c:1345
    #2  0xffffffff810029eb in ?? ()
    #3  0x0000000000000246 in ?? ()
    #4  0x00007fff63204890 in ?? ()
    #5  0x00007fc615a98210 in ?? ()
    #6  0x00007fc615a84300 in ?? ()
    #7  0x0000000000000027 in ?? ()
    #8  0x0000000000000000 in ?? ()
    (gdb) p tsk
    $2 = (struct task_struct *) 0xffff88001bbe5880
    (gdb) ptype tsk
    type = struct task_struct {
    
    (snip)
    
        pid_t pid;
        pid_t tgid;
    
    (snip)
    
        struct task_struct *group_leader;
        struct list_head ptraced;
        struct list_head ptrace_entry;
        struct pid_link pids[3];
    
    (snip)
    
    (gdb) ptype tsk->group_leader->pids
    type = struct pid_link {
        struct hlist_node node;
        struct pid *pid;
    } [3]
    
    (snip)
    
    (gdb) s
    1607            return pid_vnr(task_tgid(tsk));
    (gdb)
    1606    {
    (gdb)
    1607            return pid_vnr(task_tgid(tsk));
    (gdb)
    pid_vnr (pid=0xffff88001fb55400) at kernel/pid.c:444
    444     {
    (gdb) bt
    #0  pid_vnr (pid=0xffff88001fb55400) at kernel/pid.c:444
    #1  0xffffffff81048783 in task_tgid_vnr (tsk=<value optimized out>)
        at include/linux/sched.h:1607
    #2  0xffffffff81048cf6 in sys_getpid () at kernel/timer.c:1345
    #3  0xffffffff810029eb in ?? ()
    #4  0x0000000000000246 in ?? ()
    #5  0x00007fff63204890 in ?? ()
    #6  0x00007fc615a98210 in ?? ()
    #7  0x00007fc615a84300 in ?? ()
    #8  0x0000000000000027 in ?? ()
    #9  0x0000000000000000 in ?? ()
    (gdb) l
    439             }
    440             return nr;
    441     }
    442
    443     pid_t pid_vnr(struct pid *pid)
    444     {
    445             return pid_nr_ns(pid, current->nsproxy->pid_ns);
    446     }
    447     EXPORT_SYMBOL_GPL(pid_vnr);
    448
    (gdb) ptype pid
    type = struct pid {
        atomic_t count;
        unsigned int level;
        struct hlist_head tasks[3];
        struct rcu_head rcu;
        struct upid numbers[1];
    } *
    (gdb) up
    #1  0xffffffff81048783 in task_tgid_vnr (tsk=<value optimized out>)
        at include/linux/sched.h:1607
    1607            return pid_vnr(task_tgid(tsk));
    (gdb) ptype tsk->nsproxy->pid_ns
    type = struct pid_namespace {
        struct kref kref;
        struct pidmap pidmap[128];
        int last_pid;
        struct task_struct *child_reaper;
        struct kmem_cache *pid_cachep;
        unsigned int level;
        struct pid_namespace *parent;
        struct vfsmount *proc_mnt;
        struct bsd_acct_struct *bacct;
    } *
    (gdb) down
    #0  pid_vnr (pid=0xffff88001fb55400) at kernel/pid.c:444
    444     {
    (gdb) s
    445             return pid_nr_ns(pid, current->nsproxy->pid_ns);
    (gdb)
    get_current (pid=0xffff88001fb55400)
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/current.h:14
    14              return percpu_read_stable(current_task);
    (gdb) p current_task
    Cannot access memory at address 0xb540
    (gdb) s
    pid_vnr (pid=0xffff88001fb55400) at kernel/pid.c:445
    445             return pid_nr_ns(pid, current->nsproxy->pid_ns);
    (gdb) s
    444     {
    (gdb)
    445             return pid_nr_ns(pid, current->nsproxy->pid_ns);
    (gdb)
    pid_nr_ns (pid=0xffff88001fb55400, ns=0xffffffff8181bfe0) at kernel/pid.c:431
    431     {
    (gdb) bt
    #0  pid_nr_ns (pid=0xffff88001fb55400, ns=0xffffffff8181bfe0)
        at kernel/pid.c:431
    #1  0xffffffff81052db6 in pid_vnr (pid=0xffff88001fb55400) at kernel/pid.c:445
    #2  0xffffffff81048783 in task_tgid_vnr (tsk=<value optimized out>)
        at include/linux/sched.h:1607
    #3  0xffffffff81048cf6 in sys_getpid () at kernel/timer.c:1345
    #4  0xffffffff810029eb in ?? ()
    #5  0x0000000000000246 in ?? ()
    #6  0x00007fff63204890 in ?? ()
    #7  0x00007fc615a98210 in ?? ()
    #8  0x00007fc615a84300 in ?? ()
    #9  0x0000000000000027 in ?? ()
    #10 0x0000000000000000 in ?? ()
    (gdb) l
    426             return pid;
    427     }
    428     EXPORT_SYMBOL_GPL(find_get_pid);
    429
    430     pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
    431     {
    432             struct upid *upid;
    433             pid_t nr = 0;
    434
    435             if (pid && ns->level <= pid->level) {
    (gdb) l
    436                     upid = &pid->numbers[ns->level];
    437                     if (upid->ns == ns)
    438                             nr = upid->nr;
    439             }
    440             return nr;
    441     }
    442
    443     pid_t pid_vnr(struct pid *pid)
    444     {
    445             return pid_nr_ns(pid, current->nsproxy->pid_ns);
    (gdb) ptype pid
    type = struct pid {
        atomic_t count;
        unsigned int level;
        struct hlist_head tasks[3];
        struct rcu_head rcu;
        struct upid numbers[1];
    } *
    (gdb) ptype ns
    type = struct pid_namespace {
        struct kref kref;
        struct pidmap pidmap[128];
        int last_pid;
        struct task_struct *child_reaper;
        struct kmem_cache *pid_cachep;
        unsigned int level;
        struct pid_namespace *parent;
        struct vfsmount *proc_mnt;
        struct bsd_acct_struct *bacct;
    } *
    type = struct upid {
        int nr;
        struct pid_namespace *ns;
        struct hlist_node pid_chain;
    } *
    (gdb) ptype pid_t
    type = int
    (gdb) p ns->level
    $5 = 0
    (gdb) p pid->level
    $6 = 0
    (gdb) p ns->level <= pid->level
    $7 = 1
    (gdb) p ns
    $8 = (struct pid_namespace *) 0xffffffff8181bfe0
    (gdb) p &pid->numbers[ns->level]
    $9 = (struct upid *) 0xffff88001fb55430
    (gdb) p (&pid->numbers[ns->level])->ns
    $10 = (struct pid_namespace *) 0xffffffff8181bfe0
    (gdb) info locals
    upid = <value optimized out>
    nr = <value optimized out>
    (gdb) p nr
    $11 = <value optimized out>
    (gdb) p (&pid->numbers[ns->level])->nr
    $12 = 2225
    (gdb) s
    435             if (pid && ns->level <= pid->level) {
    (gdb)
    431     {
    (gdb)
    435             if (pid && ns->level <= pid->level) {
    (gdb)
    436                     upid = &pid->numbers[ns->level];
    (gdb)
    437                     if (upid->ns == ns)
    (gdb) p upid
    $13 = (struct upid *) 0xffff88001fb55430
    (gdb) s
    438                             nr = upid->nr;
    (gdb) p upid->ns == ns
    $14 = 1
    (gdb) p nr
    $15 = <value optimized out>
    (gdb) p upid->nr
    $16 = 2225
    (gdb) s
    441     }
    (gdb)
    pid_vnr (pid=<value optimized out>) at kernel/pid.c:446
    446     }
    (gdb) s
    task_tgid_vnr (tsk=<value optimized out>) at include/linux/sched.h:1608
    1608    }
    (gdb)
    sys_getpid () at kernel/timer.c:1346
    1346    }
    (gdb)
    sys_getpid () at kernel/timer.c:1345
    1345            return task_tgid_vnr(current);
    (gdb)
    sys_getpid () at kernel/timer.c:1346
    1346    }
    (gdb)
    
  • on VM guest
    • s0711489@ubuntu-lucid64:~/coursework/KernelHack/02$ ./getpid
      getpid() -> 2225
      

location of functions on source file

  • windell57:x86_64 s0711489$ grep percpu_read_stable -r .
    (snip)
    
    ./arch/x86/include/asm/percpu.h:#define percpu_read_stable(var)         percpu_from_op("mov", var, "p" (&(var)))
    
    (snip)
    
  • windell57:x86_64 s0711489$ grep task_tgid -r .
    (snip)
    
    ./include/linux/sched.h:static inline struct pid *task_tgid(struct task_struct *task)
    
    (snip)
    
  • include/linux/sched.h
    static inline struct pid *task_tgid(struct task_struct *task)
    {
    	return task->group_leader->pids[PIDTYPE_PID].pid;
    }
    

get_current function

  • windell57:02 s0711489$ gcc -E ../linux-2.6.35.14/x86_64/arch/x86/include/asm/current.h -I ~/coursework/KernelHack/linux-2.6.35.14/x86_64/include -I ~/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/ > current.h
    In file included from /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/percpu.h:44,
                     from ../linux-2.6.35.14/x86_64/arch/x86/include/asm/current.h:5:
    /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/include/linux/kernel.h:733:2: warning: #warning Attempt to use kernel headers from user space, see http:
    
  • pre-processed arch/x86/include/asm/current.h
    static __always_inline struct task_struct *get_current(void)
    {
     return ({ typeof(current_task) pfo_ret__; switch (sizeof(current_task)) { case 1: asm("mov" "b ""%P" "1"",%0" : "=q" (pfo_ret__) : "p" (&(current_task))); break; case 2: asm("mov" "w ""%P" "1"",%0" : "=r" (pfo_ret__) : "p" (&(current_task))); break; case 4: asm("mov" "l ""%P" "1"",%0" : "=r" (pfo_ret__) : "p" (&(current_task))); break; case 8: asm("mov" "q ""%P" "1"",%0" : "=r" (pfo_ret__) : "p" (&(current_task))); break; default: __bad_percpu_size(); } pfo_ret__; });
    }
    

10/12

tee system call

  • http://linuxjm.sourceforge.jp/html/LDP_man-pages/man2/tee.2.html
    #define _GNU_SOURCE
    #include <fcntl.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <errno.h>
    #include <limits.h>
    
    int
    main(int argc, char *argv[])
    {
        int fd;
        int len, slen;
    
        if (argc != 2) {
            fprintf(stderr, "Usage: %s <file>\n", argv[0]);
            exit(EXIT_FAILURE);
        }
    
        fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0644);
        if (fd == -1) {
            perror("open");
            exit(EXIT_FAILURE);
        }
    
        do {
            /*
             * tee stdin to stdout.
             */
            len = tee(STDIN_FILENO, STDOUT_FILENO,
                      INT_MAX, SPLICE_F_NONBLOCK);
    
            if (len < 0) {
                if (errno == EAGAIN)
                    continue;
                perror("tee");
                exit(EXIT_FAILURE);
            } else
                if (len == 0)
                    break;
    
            /*
             * Consume stdin by splicing it to a file.
             */
            while (len > 0) {
                slen = splice(STDIN_FILENO, NULL, fd, NULL,
                              len, SPLICE_F_MOVE);
                if (slen < 0) {
                    perror("splice");
                    break;
                }
                len -= slen;
            }
        } while (1);
    
        close(fd);
        exit(EXIT_SUCCESS);
    }
    
  • Ubuntu lucid(2.6.32-33-generic)やvanilla 2.6.35.14ではサンプルコードのまま正常に使える
    • mitty@ubuntu64:~/coursework/KernelHack/02$ cat tee.c | ./tee hoge | wc
           58     130    1217
      
  • CentOS 5.7(2.6.18-238.19.1.el5.centos.plusPAE or 2.6.18-274.3.1.el5)ではspliceがエラーになる
    • viola01:02 s0711489$ cat tee.c | ./tee hoge | wc
      viola01:02 s0711489$ cat tee.c | ./tee hoge | wc
      splice: Invalid argument
      splice: Invalid argument
      splice: Invalid argument
      splice: Invalid argument
      splice: Invalid argument
      splice: Invalid argument
      splice: Invalid argument
      splice: Invalid argument
      splice: Invalid argument
      
      ....
      
  • Ubuntu上でも、strace出来ない
    • mitty@ubuntu64:~/coursework/KernelHack/02$ strace -f -o sh.log sh -c 'cat tee.c | ./tee hoge | wc'
    • mitty@ubuntu64:~/coursework/KernelHack/02$ less sh.log
      (snip)
      
      1611  <... tee resumed> )               = -1 EAGAIN (Resource temporarily unavailable)
      1611  tee(0, 0x1, 0x7fffffff, 0x2)      = -1 EAGAIN (Resource temporarily unavailable)
      1611  tee(0, 0x1, 0x7fffffff, 0x2)      = -1 EAGAIN (Resource temporarily unavailable)
      1611  tee(0, 0x1, 0x7fffffff, 0x2)      = -1 EAGAIN (Resource temporarily unavailable)
      1611  tee(0, 0x1, 0x7fffffff, 0x2)      = -1 EAGAIN (Resource temporarily unavailable)
      1611  tee(0, 0x1, 0x7fffffff, 0x2)      = -1 EAGAIN (Resource temporarily unavailable)
      1611  tee(0, 0x1, 0x7fffffff, 0x2)      = -1 EAGAIN (Resource temporarily unavailable)
      
      (snip)
      
  • GDBによるステップ実行は、3000行ほど実行してみたがguest側で結果が出力されないので、断念

10/14

getcpu system call

  • getcpu system callはには存在しない
    • arch/x86/include/asm/unistd_64.h
      #define __IGNORE_getcpu     /* implemented as a vsyscall */
      
  • s0711489@ubuntu-lucid64:~/coursework/KernelHack/02$ cat > getcpu.c
    #define _GNU_SOURCE         /* See feature_test_macros(7) */
    #include <linux/getcpu.h>
    #include <stdio.h>
    
    int main (void) {
            int c, s;
            s = getcpu(&c, NULL, NULL);
            printf ("getcpu() -> %d\n", (s == -1) ? s : c);
    }
    
  • s0711489@ubuntu-lucid64:~/coursework/KernelHack/02$ gcc getcpu.c -o getcpu
    getcpu.c:1:26: error: linux/getcpu.h: No such file or directory
    

i386

  • s0711489@ubuntu-lucid:~$ sudo /mnt/hgfs/tools/install.sh
    + cat /mnt/hgfs/linux-2.6.35.14/include/config/kernel.release
    + VERSION=2.6.35.14
    + echo Install Linux Kernel version 2.6.35.14
    Install Linux Kernel version 2.6.35.14
    + cd /mnt/hgfs/linux-2.6.35.14/
    + make install
    sh /mnt/hgfs/linux-2.6.35.14/arch/x86/boot/install.sh 2.6.35.14 arch/x86/boot/bzImage \
                    System.map "/boot"
    + make modules_install
      INSTALL arch/x86/kernel/test_nx.ko
      INSTALL drivers/scsi/scsi_wait_scan.ko
      INSTALL net/netfilter/xt_mark.ko
      DEPMOD  2.6.35.14
    + mkinitramfs -o /boot/initrd.img-2.6.35.14 2.6.35.14
    + update-grub
    Generating grub.cfg ...
    Found linux image: /boot/vmlinuz-2.6.35.14
    Found initrd image: /boot/initrd.img-2.6.35.14
    Found linux image: /boot/vmlinuz-2.6.32-33-generic
    Found initrd image: /boot/initrd.img-2.6.32-33-generic
    Found memtest86+ image: /boot/memtest86+.bin
    done
    + echo Install Kernel Headers to /lib/modules/2.6.35.14/build
    Install Kernel Headers to /lib/modules/2.6.35.14/build
    + date +%Y%m%d
    + mv /lib/modules/2.6.35.14/build /lib/modules/2.6.35.14/build-20111014
    + cd /mnt/hgfs/
    + tar c --files-from -
    + tar x -C /lib/modules/2.6.35.14/
    + egrep -v vmlinu
    + egrep -v .o$
    + find linux-2.6.35.14 -type f
    + mv /lib/modules/2.6.35.14/linux-2.6.35.14 /lib/modules/2.6.35.14/build
    + uname -a
    Linux ubuntu-lucid 2.6.32-33-generic #72-Ubuntu SMP Fri Jul 29 21:08:37 UTC 2011 i686 GNU/Linux
    
  • s0711489@ubuntu-lucid:~$ sudo vmware-config-tools.pl --default
  • s0711489@ubuntu-lucid:~$ cat > getcpu.c
    #define _GNU_SOURCE
    
    #include <stdio.h>
    #include <sys/syscall.h>
    #include <unistd.h>
    #include <errno.h>
    #include <string.h>
    
    int main( void )
    {
            int cpu = syscall(SYS_getcpu);
            if (cpu < 0)
            {
                    printf( "Error: errno = %d\n", errno ); fflush(stdout);
                    printf( "Error: errno: %s\n", strerror(errno) ); fflush(stdout);
                    return -1;
            }
            printf( "cpu = %d\n", cpu );
    
            return 0;
    }
    
  • s0711489@ubuntu-lucid:~$ gcc getcpu.c -o getcpu
  • s0711489@ubuntu-lucid:~$ ./getcpu
    Error: errno = 14
    Error: errno: Bad address
    
  • うまく動かない

getuid system call

  • windell57:x86_64 s0711489$ gdb
    (gdb) set logging file gdb.getuid.log
    (gdb) set logging on
    Copying output to gdb.getuid.log.
    (gdb) file vmlinux
    Reading symbols from /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/vmlinux...(no debugging symbols found)...done.
    (gdb) b sys_getuid
    Breakpoint 1 at 0xffffffff81048d17: file kernel/timer.c, line 1366.
    (gdb) target remote localhost:8864
    Remote debugging using localhost:8864
    0xffffffff810097a9 in native_safe_halt ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/irqflags.h:49
    49              asm volatile("sti; hlt": : :"memory");
    (gdb) c
    Continuing.
    
    Breakpoint 1, sys_getuid () at kernel/timer.c:1366
    1366    {
    (gdb) s
    1368            return current_uid();
    (gdb)
    get_current ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/current.h:14
    14              return percpu_read_stable(current_task);
    (gdb)
    1368            return current_uid();
    (gdb)
    sys_getuid () at kernel/timer.c:1366
    1366    {
    (gdb)
    1368            return current_uid();
    (gdb)
    get_current () at kernel/timer.c:1368
    1368            return current_uid();
    (gdb)
    sys_getuid () at kernel/timer.c:1369
    1369    }
    (gdb)
    
    Program received signal SIGINT, Interrupt.
    0xffffffff810097a9 in native_safe_halt ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/irqflags.h:49
    49              asm volatile("sti; hlt": : :"memory");
    (gdb) detach
    Ending remote debugging.
    (gdb) quit
    
  • s0711489@ubuntu-lucid64:~/coursework/KernelHack/02$ ./getuid
    getuid() -> 1000
    

trace log with source list and print data

  • windell57:x86_64 s0711489$ gdb
    (gdb) file vmlinux
    Reading symbols from /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/vmlinux...(no debugging symbols found)...done.
    (gdb) b sys_getuid
    Breakpoint 1 at 0xffffffff81048d17: file kernel/timer.c, line 1366.
    (gdb) target remote localhost:8864
    Remote debugging using localhost:8864
    0xffffffff810097a9 in native_safe_halt ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/irqflags.h:49
    49              asm volatile("sti; hlt": : :"memory");
    (gdb) c
    Continuing.
    
    Breakpoint 1, sys_getuid () at kernel/timer.c:1366
    1366    {
    (gdb) bt
    #0  sys_getuid () at kernel/timer.c:1366
    #1  0xffffffff810029eb in ?? ()
    #2  0x0000000000000206 in ?? ()
    #3  0x00007ffff56d6ad0 in ?? ()
    #4  0x00007f8671347210 in ?? ()
    #5  0x00007f8671333300 in ?? ()
    #6  0x0000000000000066 in ?? ()
    #7  0x0000000000000000 in ?? ()
    (gdb) l
    1361
    1362            return pid;
    1363    }
    1364
    1365    SYSCALL_DEFINE0(getuid)
    1366    {
    1367            /* Only we change this so SMP safe */
    1368            return current_uid();
    1369    }
    1370
    (gdb) s
    1368            return current_uid();
    (gdb)
    get_current ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/current.h:14
    14              return percpu_read_stable(current_task);
    (gdb) bt
    #0  get_current ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/x86_64/arch/x86/include/asm/current.h:14
    #1  sys_getuid () at kernel/timer.c:1368
    #2  0xffffffff810029eb in ?? ()
    #3  0x0000000000000206 in ?? ()
    #4  0x00007ffff56d6ad0 in ?? ()
    #5  0x00007f8671347210 in ?? ()
    #6  0x00007f8671333300 in ?? ()
    #7  0x0000000000000066 in ?? ()
    #8  0x0000000000000000 in ?? ()
    (gdb) l
    9
    10      DECLARE_PER_CPU(struct task_struct *, current_task);
    11
    12      static __always_inline struct task_struct *get_current(void)
    13      {
    14              return percpu_read_stable(current_task);
    15      }
    16
    17      #define current get_current()
    18
    (gdb) p current_task
    Cannot access memory at address 0xb540
    (gdb) ptype current_task
    type = struct task_struct {
    
    (snip
    
    ---Type <return> to continue, or q <return> to quit---q
    Quit
    (gdb) s
    1368            return current_uid();
    (gdb)
    sys_getuid () at kernel/timer.c:1366
    1366    {
    (gdb) bt
    #0  sys_getuid () at kernel/timer.c:1366
    #1  0xffffffff810029eb in ?? ()
    #2  0x0000000000000206 in ?? ()
    #3  0x00007ffff56d6ad0 in ?? ()
    #4  0x00007f8671347210 in ?? ()
    #5  0x00007f8671333300 in ?? ()
    #6  0x0000000000000066 in ?? ()
    #7  0x0000000000000000 in ?? ()
    (gdb) s
    1368            return current_uid();
    (gdb)
    get_current () at kernel/timer.c:1368
    1368            return current_uid();
    (gdb) bt
    #0  get_current () at kernel/timer.c:1368
    #1  sys_getuid () at kernel/timer.c:1368
    #2  0xffffffff810029eb in ?? ()
    #3  0x0000000000000206 in ?? ()
    #4  0x00007ffff56d6ad0 in ?? ()
    #5  0x00007f8671347210 in ?? ()
    #6  0x00007f8671333300 in ?? ()
    #7  0x0000000000000066 in ?? ()
    #8  0x0000000000000000 in ?? ()
    (gdb) l
    1363    }
    1364
    1365    SYSCALL_DEFINE0(getuid)
    1366    {
    1367            /* Only we change this so SMP safe */
    1368            return current_uid();
    1369    }
    1370
    1371    SYSCALL_DEFINE0(geteuid)
    1372    {
    (gdb) s
    sys_getuid () at kernel/timer.c:1369
    1369    }
    (gdb) bt
    #0  sys_getuid () at kernel/timer.c:1369
    #1  0xffffffff810029eb in ?? ()
    #2  0x0000000000000206 in ?? ()
    #3  0x00007ffff56d6ad0 in ?? ()
    #4  0x00007f8671347210 in ?? ()
    #5  0x00007f8671333300 in ?? ()
    #6  0x0000000000000066 in ?? ()
    #7  0x0000000000000000 in ?? ()
    (gdb) l
    1364
    1365    SYSCALL_DEFINE0(getuid)
    1366    {
    1367            /* Only we change this so SMP safe */
    1368            return current_uid();
    1369    }
    1370
    1371    SYSCALL_DEFINE0(geteuid)
    1372    {
    1373            /* Only we change this so SMP safe */
    (gdb) p current_uid
    No symbol "current_uid" in current context.
    (gdb) ptype current_uid
    No symbol "current_uid" in current context.
    (gdb) s
    
    Breakpoint 1, sys_getuid () at kernel/timer.c:1366
    1366    {
    (gdb) detach
    Ending remote debugging.
    
  • include/linux/cred.h
    #define current_cred_xxx(xxx)           \
    ({                      \
        current->cred->xxx;         \
    })
    
    #define current_uid()       (current_cred_xxx(uid))
    #define current_gid()       (current_cred_xxx(gid))
    
    (snip)
    
  • ptype of current_task->cred
    (gdb) ptype current_task->cred
    type = const struct cred {
        atomic_t usage;
        uid_t uid;
        gid_t gid;
        uid_t suid;
        gid_t sgid;
        uid_t euid;
        gid_t egid;
        uid_t fsuid;
        gid_t fsgid;
        unsigned int securebits;
        kernel_cap_t cap_inheritable;
        kernel_cap_t cap_permitted;
        kernel_cap_t cap_effective;
        kernel_cap_t cap_bset;
        unsigned char jit_keyring;
        struct key *thread_keyring;
        struct key *request_key_auth;
        struct thread_group_cred *tgcred;
        void *security;
        struct user_struct *user;
        struct group_info *group_info;
        struct rcu_head rcu;
    } *
    (gdb) ptype current_task->cred->uid
    type = unsigned int
    

10/19

add new system call (i386)

  • windell57:i386 s0711489$ vim arch/x86/include/asm/unistd_32.h
  • windell57:i386 s0711489$ vim arch/x86/kernel/syscall_table_32.S
  • windell57:i386 s0711489$ vim arch/x86/include/asm/new_hello.h
  • windell57:i386 s0711489$ vim arch/x86/kernel/new_hello.c

10/21

add new system call (i386) (cont)

  • windell57:i386 s0711489$ vim arch/x86/kernel/new_hello.c
  • windell57:i386 s0711489$ vim arch/x86/kernel/Makefile
    • arch/x86/kernel/syscall_table_32.S

       
      337337    .long sys_rt_tgsigqueueinfo /* 335 */ 
      338338    .long sys_perf_event_open 
      339339    .long sys_recvmmsg 
       340    .long sys_new_hello 
    • arch/x86/kernel/Makefile

       
      131131    obj-$(CONFIG_PCI_MMCONFIG)  += mmconf-fam10h_64.o 
      132132    obj-y               += vsmp_64.o 
      133133endif 
       134 
       135obj-y               += new_hello.o 
    • arch/x86/kernel/new_hello.c

       
       1#include <linux/kernel.h> 
       2#include <linux/syscalls.h> 
       3 
       4SYSCALL_DEFINE1(new_hello, int, i) { 
       5        printk(KERN_DEBUG "new_hello() syscall with %d", i); 
       6        return i; 
       7} 
    • arch/x86/include/asm/unistd_32.h

       
      343343#define __NR_rt_tgsigqueueinfo  335 
      344344#define __NR_perf_event_open    336 
      345345#define __NR_recvmmsg       337 
       346#define __NR_new_hello      338 
      346347 
      347348#ifdef __KERNEL__ 
      348349 
      349 #define NR_syscalls 338 
       350#define NR_syscalls 339 
      350351 
      351352#define __ARCH_WANT_IPC_PARSE_VERSION 
      352353#define __ARCH_WANT_OLD_READDIR 
    • arch/x86/include/asm/new_hello.h

       
       1#ifndef _ASM_X86_NEW_HELLO_H 
       2#define _ASM_X86_NEW_HELLO_H 
       3 
       4#include <asm/unistd.h> 
       5#define new_hello(x) syscall(__NR_new_hello, x) 
       6 
       7#endif /* _ASM_X86_NEW_HELLO_H */ 
  • windell57:i386 s0711489$ make
    Kernel: arch/x86/boot/bzImage is ready  (#2)
    
  • windell57:i386 s0711489$ make modules
  • s0711489@ubuntu-lucid:~$ sudo /mnt/hgfs/tools/install.sh
  • s0711489@ubuntu-lucid:~$ sudo reboot
    Linux ubuntu-lucid 2.6.35.14 #2 SMP Fri Oct 21 14:25:51 JST 2011 i686 GNU/Linux
    Ubuntu 10.04.3 LTS
    
  • s0711489@ubuntu-lucid:~$ cat > new_hello.c
    #include <unistd.h>
    #include <syscall.h>
    #include <stdio.h>
    
    int main (void) {
            printf ("new_helloc(1) -> %d\n",
                    syscall(__NR_new_hello, 1)
            );
    }
    
  • s0711489@ubuntu-lucid:~$ gcc -I /lib/modules/2.6.35.14/build/arch/x86/include/ new_hello.c
    new_hello.c: In function ‘main’:
    new_hello.c:8: warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘long int’
    
  • dmesgにしか出なかったので、KERN_DEBUGを消す
  • windell57:i386 s0711489$ make
    Kernel: arch/x86/boot/bzImage is ready  (#3)
    
  • windell57:i386 s0711489$ make modules
  • s0711489@ubuntu-lucid:~$ sudo /mnt/hgfs/tools/install.sh
  • s0711489@ubuntu-lucid:~$ sudo reboot
  • s0711489@ubuntu-lucid:~$ cat > new_hello.c
  • s0711489@ubuntu-lucid:~$ gcc -I /lib/modules/2.6.35.14/build/arch/x86/include/ new_hello.c
  • s0711489@ubuntu-lucid:~$ ./a.out
    new_helloc(1) -> 1
    
  • s0711489@ubuntu-lucid:~$ dmesg | tail -n 1
    [  116.986628] new_hello() syscall with 1
    
  • KERN_DEBUGを消したが、結局dmesgにしか出ない
    • \nの追加
      • arch/x86/kernel/new_hello.c

         
        22#include <linux/syscalls.h> 
        33 
        44SYSCALL_DEFINE1(new_hello, int, i) { 
        5         printk(KERN_DEBUG "new_hello() syscall with %d", i); 
         5        printk("new_hello() syscall with %d\n", i); 
        66        return i; 
        77} 
  • windell57:i386 s0711489$ make
    Kernel: arch/x86/boot/bzImage is ready  (#4)
    
  • windell57:i386 s0711489$ make modules
  • s0711489@ubuntu-lucid:~$ sudo /mnt/hgfs/tools/install.sh
  • s0711489@ubuntu-lucid:~$ cat > new_hello.c
  • s0711489@ubuntu-lucid:~$ gcc -I /lib/modules/2.6.35.14/build/arch/x86/include/ new_hello.c
  • s0711489@ubuntu-lucid:~$ ./a.out
    new_helloc(1) -> 1
    
  • s0711489@ubuntu-lucid:~$ ./a.out 1
    new_helloc(2) -> 2
    
  • s0711489@ubuntu-lucid:~$ ./a.out 2
    new_helloc(2) -> 2
    
  • s0711489@ubuntu-lucid:~$ ./a.out 3
    new_helloc(2) -> 2
    
  • s0711489@ubuntu-lucid:~$ ./a.out 1 2 3 4 5
    new_helloc(6) -> 6
    
  • s0711489@ubuntu-lucid:~$ dmesg | tail
    [   62.656820] new_hello() syscall with 1
    [   66.271703] new_hello() syscall with 2
    [   68.411791] new_hello() syscall with 2
    [   70.395934] new_hello() syscall with 2
    [   77.010426] new_hello() syscall with 6
    
  • /var/log/messages /var/log/kern.log /var/log/syslog にも出るようになった
    Oct 21 15:29:00 ubuntu-lucid kernel: [   62.656820] new_hello() syscall with 1
    Oct 21 15:29:04 ubuntu-lucid kernel: [   66.271703] new_hello() syscall with 2
    Oct 21 15:29:06 ubuntu-lucid kernel: [   68.411791] new_hello() syscall with 2
    Oct 21 15:29:08 ubuntu-lucid kernel: [   70.395934] new_hello() syscall with 2
    Oct 21 15:29:14 ubuntu-lucid kernel: [   77.010426] new_hello() syscall with 6
    
  • KERN_DEBUGを戻す
    • arch/x86/kernel/new_hello.c

       
      22#include <linux/syscalls.h> 
      33 
      44SYSCALL_DEFINE1(new_hello, int, i) { 
      5         printk("new_hello() syscall with %d\n", i); 
       5        printk(KERN_DEBUG "new_hello() syscall with %d\n", i); 
      66        return i; 
      77} 
  • windell57:i386 s0711489$ make
    Kernel: arch/x86/boot/bzImage is ready  (#5)
    
  • windell57:i386 s0711489$ make modules
  • s0711489@ubuntu-lucid:~$ sudo /mnt/hgfs/tools/install.sh
  • s0711489@ubuntu-lucid:~$ ./a.out
    new_helloc(1) -> 1
    
  • s0711489@ubuntu-lucid:~$ ./a.out 2
    new_helloc(2) -> 2
    
  • s0711489@ubuntu-lucid:~$ ./a.out 2 4
    new_helloc(3) -> 3
    
  • s0711489@ubuntu-lucid:~$ ./a.out 2 3 4
    new_helloc(4) -> 4
    
  • s0711489@ubuntu-lucid:~$ tailf /var/log/syslog
    Oct 21 15:39:29 ubuntu-lucid kernel: [   55.626892] new_hello() syscall with 1
    Oct 21 15:40:18 ubuntu-lucid kernel: [  104.990720] new_hello() syscall with 2
    Oct 21 15:40:20 ubuntu-lucid kernel: [  106.772709] new_hello() syscall with 3
    Oct 21 15:40:23 ubuntu-lucid kernel: [  109.867051] new_hello() syscall with 4
    
  • /var/log/messages には出なくなる

trace sys_new_hello with GDB

  • windell57:i386 s0711489$ gdb
    (gdb) file vmlinux
    Reading symbols from /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/i386/vmlinux...(no debugging symbols found)...done.
    (gdb) b sys_new_hello
    Breakpoint 1 at 0xc101d87c: file arch/x86/kernel/new_hello.c, line 4.
    (gdb) target remote localhost:8832
    Remote debugging using localhost:8832
    0xc1007cdf in native_safe_halt ()
        at /home/ugrad/07/s0711489/coursework/KernelHack/linux-2.6.35.14/i386/arch/x86/include/asm/irqflags.h:49
    49              asm volatile("sti; hlt": : :"memory");
    (gdb) c
    Continuing.
    
    Breakpoint 1, sys_new_hello (i=1) at arch/x86/kernel/new_hello.c:4
    4       SYSCALL_DEFINE1(new_hello, int, i) {
    (gdb) n
    5               printk(KERN_DEBUG "new_hello() syscall with %d\n", i);
    (gdb) l
    1       #include <linux/kernel.h>
    2       #include <linux/syscalls.h>
    3
    4       SYSCALL_DEFINE1(new_hello, int, i) {
    5               printk(KERN_DEBUG "new_hello() syscall with %d\n", i);
    6               return i;
    7       }
    (gdb) s
    printk (fmt=0xc1449502 "<7>new_hello() syscall with %d\n")
        at kernel/printk.c:614
    614             va_start(args, fmt);
    (gdb) l
    609                     r = vkdb_printf(fmt, args);
    610                     va_end(args);
    611                     return r;
    612             }
    613     #endif
    614             va_start(args, fmt);
    615             r = vprintk(fmt, args);
    616             va_end(args);
    617
    618             return r;
    (gdb) n
    615             r = vprintk(fmt, args);
    (gdb)
    614             va_start(args, fmt);
    (gdb)
    615             r = vprintk(fmt, args);
    (gdb)
    619     }
    (gdb)
    sys_new_hello (i=1) at arch/x86/kernel/new_hello.c:7
    7       }
    (gdb) l
    2       #include <linux/syscalls.h>
    3
    4       SYSCALL_DEFINE1(new_hello, int, i) {
    5               printk(KERN_DEBUG "new_hello() syscall with %d\n", i);
    6               return i;
    7       }
    (gdb) s
    
  • s0711489@ubuntu-lucid:~$ ./a.out
    new_helloc(1) -> 1
    

add sys_new_hello entry

  • windell57:i386 s0711489$ vim include/linux/syscalls.h
    • include/linux/syscalls.h

       
      826826            unsigned long fd, unsigned long pgoff); 
      827827asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg); 
      828828 
       829asmlinkage long sys_new_hello(int i); 
       830 
      829831#endif 
  • windell57:i386 s0711489$ make
    Kernel: arch/x86/boot/bzImage is ready  (#6)
    
  • windell57:i386 s0711489$ make modules
  • s0711489@ubuntu-lucid:~$ sudo /mnt/hgfs/tools/install.sh
  • s0711489@ubuntu-lucid:~$ ./a.out
    new_helloc(1) -> 1
    
  • s0711489@ubuntu-lucid:~$ ./a.out 2
    new_helloc(2) -> 2
    
  • s0711489@ubuntu-lucid:~$ ./a.out 2 3
    new_helloc(3) -> 3
    
  • s0711489@ubuntu-lucid:~$ tailf /var/log/kern.log
    Oct 21 16:16:20 ubuntu-lucid kernel: [   59.045533] new_hello() syscall with 1
    Oct 21 16:16:22 ubuntu-lucid kernel: [   61.043321] new_hello() syscall with 2
    Oct 21 16:16:24 ubuntu-lucid kernel: [   63.470397] new_hello() syscall with 3
    

add new system call (x86_64)

  • viola04:linux-2.6.35.14 s0711489$ svn cp i386/arch/x86/include/asm/new_hello.h x86_64/arch/x86/include/asm/new_hello.h
  • viola04:linux-2.6.35.14 s0711489$ svn cp i386/arch/x86/kernel/new_hello.c x86_64/arch/x86/kernel/
  • viola04:linux-2.6.35.14 s0711489$ svn merge i386/include/linux/syscalls.h x86_64/include/linux/syscalls.h -r 1358:1359

10/26

add new system call (x86_64) (cont)

  • viola06:x86_64 s0711489$ svn revert include/linux/syscalls.h arch/x86/kernel/new_hello.c arch/x86/include/asm/new_hello.h
  • viola06:x86_64 s0711489$ rm arch/x86/kernel/new_hello.c arch/x86/include/asm/new_hello.h
  • viola06:linux-2.6.35.14 s0711489$ svn merge i386/arch/ x86_64/arch/ -r1352:1359
  • viola06:linux-2.6.35.14 s0711489$ svn merge i386/include/ x86_64/include/ -r1358:1359
  • viola04:x86_64 s0711489$ vim arch/x86/include/asm/unistd_64.h
    Index: include/linux/syscalls.h
    ===================================================================
    --- include/linux/syscalls.h	(revision 1367)
    +++ include/linux/syscalls.h	(revision 1368)
    @@ -826,4 +826,6 @@
     			unsigned long fd, unsigned long pgoff);
     asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg);
     
    +asmlinkage long sys_new_hello(int i);
    +
     #endif
    Index: include
    ===================================================================
    --- include	(revision 1367)
    +++ include	(revision 1368)
    
    Property changes on: include
    ___________________________________________________________________
    Added: svn:mergeinfo
       Merged /trunk/coursework/KernelHack/linux-2.6.35.14/i386/include:r1359
    Index: arch/x86/kernel/syscall_table_32.S
    ===================================================================
    --- arch/x86/kernel/syscall_table_32.S	(revision 1367)
    +++ arch/x86/kernel/syscall_table_32.S	(revision 1368)
    @@ -337,3 +337,4 @@
     	.long sys_rt_tgsigqueueinfo	/* 335 */
     	.long sys_perf_event_open
     	.long sys_recvmmsg
    +	.long sys_new_hello
    Index: arch/x86/kernel/Makefile
    ===================================================================
    --- arch/x86/kernel/Makefile	(revision 1367)
    +++ arch/x86/kernel/Makefile	(revision 1368)
    @@ -131,3 +131,5 @@
     	obj-$(CONFIG_PCI_MMCONFIG)	+= mmconf-fam10h_64.o
     	obj-y				+= vsmp_64.o
     endif
    +
    +obj-y				+= new_hello.o
    Index: arch/x86/kernel/new_hello.c
    ===================================================================
    --- arch/x86/kernel/new_hello.c	(revision 0)
    +++ arch/x86/kernel/new_hello.c	(revision 1368)
    @@ -0,0 +1,7 @@
    +#include <linux/kernel.h>
    +#include <linux/syscalls.h>
    +
    +SYSCALL_DEFINE1(new_hello, int, i) {
    +        printk(KERN_DEBUG "new_hello() syscall with %d\n", i);
    +        return i;
    +}
    Index: arch/x86/include/asm/unistd_32.h
    ===================================================================
    --- arch/x86/include/asm/unistd_32.h	(revision 1367)
    +++ arch/x86/include/asm/unistd_32.h	(revision 1368)
    @@ -343,10 +343,11 @@
     #define __NR_rt_tgsigqueueinfo	335
     #define __NR_perf_event_open	336
     #define __NR_recvmmsg		337
    +#define __NR_new_hello		338
     
     #ifdef __KERNEL__
     
    -#define NR_syscalls 338
    +#define NR_syscalls 339
     
     #define __ARCH_WANT_IPC_PARSE_VERSION
     #define __ARCH_WANT_OLD_READDIR
    Index: arch/x86/include/asm/new_hello.h
    ===================================================================
    --- arch/x86/include/asm/new_hello.h	(revision 0)
    +++ arch/x86/include/asm/new_hello.h	(revision 1368)
    @@ -0,0 +1,7 @@
    +#ifndef _ASM_X86_NEW_HELLO_H
    +#define _ASM_X86_NEW_HELLO_H
    +
    +#include <asm/unistd.h>
    +#define new_hello(x) syscall(__NR_new_hello, x)
    +
    +#endif /* _ASM_X86_NEW_HELLO_H */
    Index: arch/x86/include/asm/unistd_64.h
    ===================================================================
    --- arch/x86/include/asm/unistd_64.h	(revision 1367)
    +++ arch/x86/include/asm/unistd_64.h	(revision 1368)
    @@ -663,6 +663,8 @@
     __SYSCALL(__NR_perf_event_open, sys_perf_event_open)
     #define __NR_recvmmsg				299
     __SYSCALL(__NR_recvmmsg, sys_recvmmsg)
    +#define __NR_new_hello				300
    +__SYSCALL(__NR_new_hello, sys_new_hello)
     
     #ifndef __NO_STUBS
     #define __ARCH_WANT_OLD_READDIR
    Index: arch
    ===================================================================
    --- arch	(revision 1367)
    +++ arch	(revision 1368)
    
    Property changes on: arch
    ___________________________________________________________________
    Added: svn:mergeinfo
       Merged /trunk/coursework/KernelHack/linux-2.6.35.14/i386/arch:r1353-1359
    
  • viola06:x86_64 s0711489$ make -j 16
    Kernel: arch/x86/boot/bzImage is ready  (#2)
    
  • viola06:x86_64 s0711489$ make modules
  • s0711489@ubuntu-lucid64:~$ sudo /mnt/hgfs/tools/install.sh
  • s0711489@ubuntu-lucid64:~/KernelHack/03$ uname -a
    Linux ubuntu-lucid64 2.6.32-33-generic #72-Ubuntu SMP Fri Jul 29 21:07:13 UTC 2011 x86_64 GNU/Linux
    
  • s0711489@ubuntu-lucid64:~/KernelHack/03$ gcc -I /lib/modules/2.6.35.14/build/arch/x86/include/ new_hello.c
    new_hello.c: In function ‘main’:
    new_hello.c:9: warning: format ‘%d’ expects type ‘int’, but argument 3 has type ‘long int’
    
  • s0711489@ubuntu-lucid64:~/KernelHack/03$ ./a.out
    new_hello(1) -> -1
    
    • reboot 前はsyscallが存在しない
  • s0711489@ubuntu-lucid64:~$ sudo reboot
  • s0711489@ubuntu-lucid64:~$ uname -a
    Linux ubuntu-lucid64 2.6.35.14 #2 SMP Wed Oct 26 13:06:41 JST 2011 x86_64 GNU/Linux
    
  • s0711489@ubuntu-lucid64:~/KernelHack/03$ ./a.out
    new_hello(1) -> 1
    
  • s0711489@ubuntu-lucid64:~/KernelHack/03$ ./a.out 2
    new_hello(2) -> 2
    
  • s0711489@ubuntu-lucid64:~/KernelHack/03$ ./a.out 2 3
    new_hello(3) -> 3
    
  • s0711489@ubuntu-lucid64:~/KernelHack/03$ ./a.out 2 3 4
    new_hello(4) -> 4
    
  • s0711489@ubuntu-lucid64:~/KernelHack/03$ tail /var/log/kern.log
    Oct 26 13:12:40 ubuntu-lucid64 kernel: [   40.542158] new_hello() syscall with 1
    Oct 26 13:12:42 ubuntu-lucid64 kernel: [   42.668465] new_hello() syscall with 2
    Oct 26 13:12:43 ubuntu-lucid64 kernel: [   43.908292] new_hello() syscall with 3
    Oct 26 13:12:45 ubuntu-lucid64 kernel: [   45.645548] new_hello() syscall with 4
    

10/28

  • intro(2): Introduction to system calls - Linux man page

    System calls are not required to return only positive or negative error codes. You need to read the source to be sure how it will return errors. Usually, it is the negative of a standard error code, e.g., -EPERM. The _syscall() macros will return the result r of the system call when r is non-negative, but will return -1 and set the variable errno to -r when r is negative.

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