Linux debug Strace 사용 (추후 정리후 삭제)

Strace Debug

$ strace -h
usage: strace [-CdffhiqrtttTvVwxxy] [-I n] [-e expr]...
              [-a column] [-o file] [-s strsize] [-P path]...
              -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]
   or: strace -c[dfw] [-I n] [-e expr]... [-O overhead] [-S sortby]
              -p pid... / [-D] [-E var=val]... [-u username] PROG [ARGS]

Output format:
  -a column      alignment COLUMN for printing syscall results (default 40)
  -i             print instruction pointer at time of syscall
  -o file        send trace output to FILE instead of stderr
  -q             suppress messages about attaching, detaching, etc.
  -r             print relative timestamp
  -s strsize     limit length of print strings to STRSIZE chars (default 32)
  -t             print absolute timestamp
  -tt            print absolute timestamp with usecs
  -T             print time spent in each syscall
  -x             print non-ascii strings in hex
  -xx            print all strings in hex
  -y             print paths associated with file descriptor arguments
  -yy            print ip:port pairs associated with socket file descriptors

Statistics:
  -c             count time, calls, and errors for each syscall and report summary
  -C             like -c but also print regular output
  -O overhead    set overhead for tracing syscalls to OVERHEAD usecs
  -S sortby      sort syscall counts by: time, calls, name, nothing (default time)
  -w             summarise syscall latency (default is system time)

Filtering:
  -e expr        a qualifying expression: option=[!]all or option=[!]val1[,val2]...
     options:    trace, abbrev, verbose, raw, signal, read, write
  -P path        trace accesses to path

Tracing:
  -b execve      detach on execve syscall
  -D             run tracer process as a detached grandchild, not as parent
  -f             follow forks
  -ff            follow forks with output into separate files
  -I interruptible
     1:          no signals are blocked
     2:          fatal signals are blocked while decoding syscall (default)
     3:          fatal signals are always blocked (default if '-o FILE PROG')
     4:          fatal signals and SIGTSTP (^Z) are always blocked
                 (useful to make 'strace -o FILE PROG' not stop on ^Z)

Startup:
  -E var         remove var from the environment for command
  -E var=val     put var=val in the environment for command
  -p pid         trace process with process id PID, may be repeated
  -u username    run command as username handling setuid and/or setgid

Miscellaneous:
  -d             enable debug output to stderr
  -v             verbose mode: print unabbreviated argv, stat, termios, etc. args
  -h             print help message
  -V             print version

$ sudo cat /proc/550/maps  // 실행과 관련된 공유라이브러리 확인 
$ sudo cat /proc/550/status  // Process 상태확인 
$ readelf -h /proc/550/exe    // 실행파일 확인 
$ readelf -s /proc/550/exe    // symbol table 확인     


$ strace -p 550 -f -t
...........
[pid   994] 11:25:13 pselect6(0, NULL, NULL, NULL, {0, 10000000}, NULL) = 0 (Timeout)
[pid   994] 11:25:13 openat(AT_FDCWD, "/proc/irq/366/spurious", O_RDONLY) = 31
[pid   994] 11:25:13 fstat(31, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
[pid   994] 11:25:13 fstat(31, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
[pid   994] 11:25:13 read(31, "count 180\nunhandled 0\nlast_unhan"..., 1024) = 42
...............

$ strace -p 550 -f -tt
[pid   994] 11:30:52.563464 fstat(31, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
[pid   994] 11:30:52.563761 fstat(31, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
[pid   994] 11:30:52.564047 read(31, "count 180\nunhandled 0\nlast_unhan"..., 1024) = 42

$ strace -cp 550 -f
strace: Process 550 attached with 4 threads
^Cstrace: Process 550 detached
strace: Process 743 detached
strace: Process 994 detached
strace: Process 995 detached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 98.67    0.488000        1132       431           pselect6
  0.94    0.004653          12       382           sendto
  0.13    0.000666           2       382           openat
  0.10    0.000495           1       382           close
  0.09    0.000457           1       764           fstat
  0.06    0.000310           1       382           read
  0.00    0.000000           0         4         2 futex
------ ----------- ----------- --------- --------- ----------------
100.00    0.494581                  2727         2 total

http://www.brendangregg.com/perf.html
https://brunch.co.kr/@alden/12

http://linuxspot.tistory.com/253

http://man7.org/linux/man-pages/man1/strace.1.html