Hello,
I have understood a fair amount of working, how -e trace=option works.
Through the init() --> qualify()
for (p = strtok(copy, ","); p; p = strtok(NULL, ",")) {
int n;
if (opt->bitflag == QUAL_TRACE && (n = lookup_class(p)) > 0) {
unsigned pers;
for (pers = 0; pers < SUPPORTED_PERSONALITIES; pers++) {
for (i = 0; i < nsyscall_vec[pers]; i++)
if (sysent_vec[pers][i].sys_flags & n)
qualify_one(i, opt->bitflag, not, pers);
}
continue;
}
This piece of code is doing the magic. Now the lookupclass() uses the
bit set by the macros which is used to set the bits in qual_vec.
through qualify_one().
Although I am not understanding how the macros
TRACE_FILE, TRACE_IPC, TRACE_NETWORK, etc which corresponds to the
bits 001, 002, 004, work and set the particular system call bit in
qual_vec. I mean what will be the bit if I want to add TRACE_OPEN_LIKE
or something like that.
Btw, I am still trying to understand how qual_vec is used to trace
only particular system calls. May be the knowledge will help me
contribute more.
A Note. I saw at many critical places you are using wait4() system
call to wait for the process. I read it is obsolete. Should we worry
about it and think of changing it to waitpid() and getrusage() at
places.
--
With regards,
Md Haris Iqbal,
Placement Coordinator, MTech IT
NITK Surathkal,
Contact: +91 8861996962
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