Re: deref fault from alias, not from probe handler

Re: deref fault from alias, not from probe handler

[Kevin Stafford]

>> [...]
>>> the two pointers being dereferenced are in user space, thus ineligible to use 
>>> the $ptr->field shortcut.
>> [...]
>> So here is how I am getting around this:
>> /*________________CUT HERE________________*/> 
>> %{
>> #include <sys/times.h>
>> %}
>> probe times =
>>    kernel.function("sys_times") {
>>       name = "times"
>>       buf_tms_utime =  __uget_tms_m($tbuf,0)
>>       buf_tms_stime =  __uget_tms_m($tbuf,1)
>>       buf_tms_cutime = __uget_tms_m($tbuf,2)
>>       buf_tms_cstime = __uget_tms_m($tbuf,3)
>>    }
>> probe times {
>>    log(string(buf_tms_utime))
>>    log(string(buf_tms_stime))
>>    log(string(buf_tms_cutime))
>>    log(string(buf_tms_cstime))
>> }
>> function __uget_tms_m:long(u_addr:long,member:long)
>> %{
>>    struct tms t;
>>    char *ptr = (char *)(unsigned long)THIS->u_addr;
>>    size_t sz = sizeof(struct tms);
>>
>>    if(copy_from_user(&t,ptr,sz))
>>       THIS->__retvalue = -EFAULT;
>>    switch(THIS->member) {
>>       case 0: THIS->__retvalue =  t.tms_utime;
>>          break;
>>       case 1: THIS->__retvalue =  t.tms_stime;
>>          break;
>>       case 2: THIS->__retvalue =  t.tms_cutime;
>>          break;
>>       case 3: THIS->__retvalue =  t.tms_cstime;
>>          break;
>>       default: THIS->__retvalue = -1;
>>    }
>> %}
>> /*________________CUT HERE________________*/
>> This script produces the following compiler
>> error:
>>
>> In function ‘function___uget_tms_m’:
>> /tmp/stapmFByii/stap_9586.c:194: error: storage size of ‘t’ isn’t known
>> /tmp/stapmFByii/stap_9586.c:196: error: invalid application of ‘sizeof’ to
>> incomplete type ‘struct tms’
>>
>> This is the error one would receive if they had forgotten to include the header
>> sys/times.h file. Although a quick verification proves otherwise:
>>
>> [root@localhost]# stap -vgp3 foo.stp > tmp.c
>> [root@localhost]# grep sys/times.h tmp.c
>> #include <sys/times.h>
>
> <sys/times.h> is a user-level header file.  You probably need simply <times.h>
> or <linux/times.h>, whichever is the linux kernel standard way.
> Any ideas on this one??? Thanks in advance.

Thanks Frank. Your suggestion worked.

-- 
Kevin Stafford
DES 2 | MS 2M3
Beaverton - OR
Linux Technology Center
IBM Systems & Technology
Phone: 1-503-578-3039
Email: kevinrs@us.ibm.com