Kuzinhlelo zokusebenza ezifana ne-Unix, ukuxhumana kohlelo nomhlaba wangaphandle kanye nesistimu yokusebenza kwenzeka ngesethi encane yemisebenzi - izingcingo zesistimu. Lokhu kusho ukuthi ngezinjongo zokulungisa iphutha kungaba usizo ukuhlola izingcingo zesistimu ezenziwa yizinqubo.
Isisetshenziswa sikusiza ukuthi ugade "impilo eseduze" yezinhlelo ku-Linux strace, okuyisihloko salesi sihloko. Izibonelo zokusetshenziswa kwemishini yezinhloli zihambisana nomlando omfushane strace kanye nencazelo yokwakheka kwezinhlelo ezinjalo.
Okuqukethwe
Umsuka wezinhlobo
Ukuxhumana okuyinhloko phakathi kwezinhlelo kanye ne-OS kernel ku-Unix izingcingo zesistimu. izingcingo zesistimu, ama-syscalls), ukusebenzelana kwezinhlelo nomhlaba wangaphandle kwenzeka ngazo kuphela.
Kepha kunguqulo yokuqala yomphakathi ye-Unix (, 1975) zazingekho izindlela ezilula zokulandelela ukuziphatha kwezinqubo zabasebenzisi. Ukuze kuxazululwe le nkinga, ama-Bell Labs azothuthukela enguqulweni elandelayo (, 1979) uphakamise ucingo lwesistimu entsha - ptrace.
i-ptrace yenzelwe ikakhulukazi abalungisa iphutha abasebenzisanayo, kodwa ekupheleni kweminyaka yama-80s (ngenkathi yokuhweba ) ngenxa yalesi sisekelo, kwavela ama-debugger agxile kancaneβama-call call tracersβfuthi asetshenziswa kabanzi.
inguqulo efanayo ye-strace yanyatheliswa ngu-Paul Cronenburg ohlwini lwamakheli we-com.sources.sun ngo-1992 njengenye indlela yensiza evaliwe trace kusuka eLangeni. Kokubili i-clone kanye neyokuqala bekuhloselwe i-SunOS, kodwa ngo-1994 strace yathuthelwa ku-System V, uSolaris kanye neLinux eyanda ukuduma.
Namuhla i-strace isekela kuphela i-Linux futhi incike okufanayo ptrace, egcwele izandiso eziningi.
Umnakekeli wesimanje (futhi osebenza kakhulu). strace - . Ngenxa yakhe, insiza ithole izici ezithuthukile njengokujova amaphutha kumakholi wesistimu, ukusekelwa kwezinhlobonhlobo zezakhiwo futhi, okubaluleke kakhulu, . Imithombo engekho emthethweni ithi ukukhetha kwawela intshe ngenxa yokuvumelana phakathi kwegama lesiRashiya elithi βostrichβ nelesiNgisi elithi βstraceβ.
Kubalulekile futhi ukuthi ucingo lwesistimu ye-ptrace nama-tracer akukaze kufakwe ku-POSIX, naphezu komlando omude nokusebenza ku-Linux, FreeBSD, OpenBSD kanye ne-Unix yendabuko.
Strace idivayisi ngamafuphi: Piglet Trace
"Akulindelekile ukuthi ukuqonde lokhu" (Dennis Ritchie, phawula ku-Version 6 ikhodi yomthombo ye-Unix)
Kusukela ngisemncane, angikwazi ukuma amabhokisi amnyama: Angizange ngidlale ngamathoyizi, kodwa ngazama ukuqonda isakhiwo sabo (abadala basebenzisa igama elithi "ukuphuka," kodwa ungakholelwa izilimi ezimbi). Mhlawumbe yingakho isiko elingakahleleki le-Unix yokuqala kanye nenhlangano yesimanje yomthombo ovulekile iseduze kakhulu nami.
Ngezinjongo zalesi sihloko, akunangqondo ukuqaqa ikhodi yomthombo ye-strace, ekhule emashumini eminyaka. Kodwa akumele kube nezimfihlo ezishiyelwa abafundi. Ngakho-ke, ukukhombisa isimiso sokusebenza kwezinhlelo ezinjalo ze-strace, ngizohlinzeka ngekhodi ye-tracer miniature - (ptr). Akwazi ukwenza noma yini ekhethekile, kodwa into eyinhloko izingcingo zesistimu zohlelo - oluphumayo:
$ gcc examples/piglet-trace.c -o ptr
$ ptr echo test > /dev/null
BRK(12) -> 94744690540544
ACCESS(21) -> 18446744073709551614
ACCESS(21) -> 18446744073709551614
unknown(257) -> 3
FSTAT(5) -> 0
MMAP(9) -> 140694657216512
CLOSE(3) -> 0
ACCESS(21) -> 18446744073709551614
unknown(257) -> 3
READ(0) -> 832
FSTAT(5) -> 0
MMAP(9) -> 140694657208320
MMAP(9) -> 140694650953728
MPROTECT(10) -> 0
MMAP(9) -> 140694655045632
MMAP(9) -> 140694655070208
CLOSE(3) -> 0
unknown(158) -> 0
MPROTECT(10) -> 0
MPROTECT(10) -> 0
MPROTECT(10) -> 0
MUNMAP(11) -> 0
BRK(12) -> 94744690540544
BRK(12) -> 94744690675712
unknown(257) -> 3
FSTAT(5) -> 0
MMAP(9) -> 140694646390784
CLOSE(3) -> 0
FSTAT(5) -> 0
IOCTL(16) -> 18446744073709551591
WRITE(1) -> 5
CLOSE(3) -> 0
CLOSE(3) -> 0
unknown(231)
Tracee terminatedI-Piglet Trace ibona amakhulukhulu ezingcingo zesistimu ye-Linux (bona. ) futhi isebenza kuphela ku-architecture ye-x86-64. Lokhu kwanele ngezinjongo zemfundo.
Ake sibheke umsebenzi we-clone yethu. Endabeni ye-Linux, abalungisa iphutha nabalandeleli basebenzisa, njengoba kushiwo ngenhla, ucingo lwesistimu ye-ptrace. Isebenza ngokudlulisela empikiswaneni yokuqala izihlonzi zomyalo, esizidingayo kuphela PTRACE_TRACEME, PTRACE_SYSCALL ΠΈ PTRACE_GETREGS.
I-tracer iqala ngesitayela esijwayelekile se-Unix: fork(2) iqala inqubo yengane, yona esebenzisa exec(3) wethula uhlelo olusafundwayo. Okuwubuqili kuphela lapha inselele ptrace(PTRACE_TRACEME) ΠΏΠ΅ΡΠ΅Π΄ exec: Inqubo yengane ilindele inqubo yomzali ukuyiqapha:
pid_t child_pid = fork();
switch (child_pid) {
case -1:
err(EXIT_FAILURE, "fork");
case 0:
/* Child here */
/* A traced mode has to be enabled. A parent will have to wait(2) for it
* to happen. */
ptrace(PTRACE_TRACEME, 0, NULL, NULL);
/* Replace itself with a program to be run. */
execvp(argv[1], argv + 1);
err(EXIT_FAILURE, "exec");
}Inqubo yomzali kufanele manje ishaye ucingo wait(2) enqubweni yengane, okungukuthi, qiniseka ukuthi ukushintshela kumodi yokulandelela kwenzeke:
/* Parent */
/* First we wait for the child to set the traced mode (see
* ptrace(PTRACE_TRACEME) above) */
if (waitpid(child_pid, NULL, 0) == -1)
err(EXIT_FAILURE, "traceme -> waitpid");Kuleli qophelo, amalungiselelo aseqedile futhi ungaqhubekela ngqo ekulandeleleni izingcingo zesistimu ngeluphu engapheli.
Shayela ptrace(PTRACE_SYSCALL) iqinisekisa lokho okulandelayo wait umzali uzoqedela ngaphambi kokwenziwa kwekholi yesistimu noma ngokushesha ngemva kokuqeda. Phakathi kwezingcingo ezimbili ungenza noma yiziphi izenzo: shintsha ucingo ufake olunye, shintsha izimpikiswano noma inani lokubuyisela.
Sidinga nje ukubiza umyalo kabili ptrace(PTRACE_GETREGS)ukuze uthole isimo sokubhalisa rax ngaphambi kocingo (inombolo yocingo lwesistimu) futhi ngokushesha ngemva (inani lokubuyisela).
Eqinisweni, umjikelezo:
/* A system call tracing loop, one interation per call. */
for (;;) {
/* A non-portable structure defined for ptrace/GDB/strace usage mostly.
* It allows to conveniently dump and access register state using
* ptrace. */
struct user_regs_struct registers;
/* Enter syscall: continue execution until the next system call
* beginning. Stop right before syscall.
*
* It's possible to change the system call number, system call
* arguments, return value or even avoid executing the system call
* completely. */
if (ptrace(PTRACE_SYSCALL, child_pid, NULL, NULL) == -1)
err(EXIT_FAILURE, "enter_syscall");
if (waitpid(child_pid, NULL, 0) == -1)
err(EXIT_FAILURE, "enter_syscall -> waitpid");
/* According to the x86-64 system call convention on Linux (see man 2
* syscall) the number identifying a syscall should be put into the rax
* general purpose register, with the rest of the arguments residing in
* other general purpose registers (rdi,rsi, rdx, r10, r8, r9). */
if (ptrace(PTRACE_GETREGS, child_pid, NULL, ®isters) == -1)
err(EXIT_FAILURE, "enter_syscall -> getregs");
/* Note how orig_rax is used here. That's because on x86-64 rax is used
* both for executing a syscall, and returning a value from it. To
* differentiate between the cases both rax and orig_rax are updated on
* syscall entry/exit, and only rax is updated on exit. */
print_syscall_enter(registers.orig_rax);
/* Exit syscall: execute of the syscall, and stop on system
* call exit.
*
* More system call tinkering possible: change the return value, record
* time it took to finish the system call, etc. */
if (ptrace(PTRACE_SYSCALL, child_pid, NULL, NULL) == -1)
err(EXIT_FAILURE, "exit_syscall");
if (waitpid(child_pid, NULL, 0) == -1)
err(EXIT_FAILURE, "exit_syscall -> waitpid");
/* Retrieve register state again as we want to inspect system call
* return value. */
if (ptrace(PTRACE_GETREGS, child_pid, NULL, ®isters) == -1) {
/* ESRCH is returned when a child terminates using a syscall and no
* return value is possible, e.g. as a result of exit(2). */
if (errno == ESRCH) {
fprintf(stderr, "nTracee terminatedn");
break;
}
err(EXIT_FAILURE, "exit_syscall -> getregs");
}
/* Done with this system call, let the next iteration handle the next
* one */
print_syscall_exit(registers.rax);
}Yilokho umkhondo wonke. Manje uyazi ukuthi ungaqala kuphi ukuthuthwa okulandelayo ku-Linux.
Okuyisisekelo: ukusebenzisa uhlelo olusebenzisa i-strace
Njengecala lokuqala lokusetshenziswa strace, mhlawumbe kufanelekile ukusho indlela elula - ukwethula uhlelo lokusebenza olusebenzayo strace.
Ukuze singangeni ohlwini lwezingcingo ezingapheli zohlelo olujwayelekile, siyabhala nxazonke write:
int main(int argc, char *argv[])
{
char str[] = "write me to stdoutn";
/* write(2) is a simple wrapper around a syscall so it should be easy to
* find in the syscall trace. */
if (sizeof(str) != write(STDOUT_FILENO, str, sizeof(str))){
perror("write");
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
Asakhe uhlelo futhi siqinisekise ukuthi luyasebenza:
$ gcc examples/write-simple.c -o write-simple
$ ./write-simple
write me to stdoutFuthi ekugcineni, masiyiqhube ngaphansi kokulawulwa kwe-strace:
$ strace ./write-simple
pexecve("./write", ["./write"], 0x7ffebd6145b0 /* 71 vars */) = 0
brk(NULL) = 0x55ff5489e000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=197410, ...}) = 0
mmap(NULL, 197410, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f7a2a633000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "177ELF21133>1260342"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=2030544, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f7a2a631000
mmap(NULL, 4131552, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f7a2a04c000
mprotect(0x7f7a2a233000, 2097152, PROT_NONE) = 0
mmap(0x7f7a2a433000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7f7a2a433000
mmap(0x7f7a2a439000, 15072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f7a2a439000
close(3) = 0
arch_prctl(ARCH_SET_FS, 0x7f7a2a6324c0) = 0
mprotect(0x7f7a2a433000, 16384, PROT_READ) = 0
mprotect(0x55ff52b52000, 4096, PROT_READ) = 0
mprotect(0x7f7a2a664000, 4096, PROT_READ) = 0
munmap(0x7f7a2a633000, 197410) = 0
write(1, "write me to stdoutn", 20write me to stdout
) = 20
exit_group(0) = ?"Amagama" kakhulu futhi awafundisi kakhulu. Kunezinkinga ezimbili lapha: okuphumayo kohlelo kuxutshwa nokuphumayo strace kanye nenqwaba yezingcingo zesistimu ezingasithandi.
Ungahlukanisa ukusakaza okujwayelekile okukhiphayo kohlelo kanye nokukhiphayo kwephutha usebenzisa i- -o switch, eqondisa kabusha uhlu lwamakholi wesistimu kufayela lokungqubuzana.
Kusele ukubhekana nenkinga yezingcingo "ezengeziwe". Ake sicabange ukuthi sinentshisekelo ezicingweni kuphela write. Ukhiye -e ikuvumela ukuthi ucacise izinkulumo izingcingo zesistimu zizohlungwa ngazo. Inketho yesimo edume kakhulu, ngokwemvelo, trace=*, ongashiya ngazo kuphela izingcingo esizithandayo.
Lapho isetshenziswa kanyekanye -o ΠΈ -e sizothola:
$ strace -e trace=write -owrite-simple.log ./write-simple
write me to stdout
$ cat write-simple.log
write(1, "write me to stdoutn", 20
) = 20
+++ exited with 0 +++Ngakho, uyabona, kulula kakhulu ukufunda.
Ungaphinda ususe amakholi wesistimu, isibonelo lawo ahlobene nokwabiwa kwememori nokukhulula:
$ strace -e trace=!brk,mmap,mprotect,munmap -owrite-simple.log ./write-simple
write me to stdout
$ cat write-simple.log
execve("./write-simple", ["./write-simple"], 0x7ffe9972a498 /* 69 vars */) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=124066, ...}) = 0
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "177ELF21133>1260342"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=2030544, ...}) = 0
close(3) = 0
arch_prctl(ARCH_SET_FS, 0x7f00f0be74c0) = 0
write(1, "write me to stdoutn", 20) = 20
exit_group(0) = ?
+++ exited with 0 +++Qaphela uphawu lokubabaza oluphunyukile ohlwini lwamakholi angabaliwe: lokhu kudingwa igobolondo lomyalo. igobolondo).
Enguqulweni yami ye-glibc, ucingo lwesistimu lunqamula inqubo exit_group, hhayi ngokwesiko _exit. Lobu ubunzima bokusebenza ngezingcingo zesistimu: isixhumi esibonakalayo lapho umenzi wohlelo asebenza khona asihlobene ngokuqondile nezingcingo zesistimu. Ngaphezu kwalokho, ishintsha njalo ngokuya ngokuqaliswa kanye nesikhulumi.
Okuyisisekelo: ukujoyina inqubo ngokuhamba
Ekuqaleni, isistimu ye-ptrace ibiza lapho yakhiwe khona strace, ingasetshenziswa kuphela uma usebenzisa uhlelo ngemodi ekhethekile. Lo mkhawulo kungenzeka ukuthi wawuzwakala unengqondo ezinsukwini ze-Version 6 Unix. Namuhla, lokhu akusanele: ngezinye izikhathi udinga ukuphenya izinkinga zohlelo lokusebenza. Isibonelo esijwayelekile inqubo evinjwe esibambeni noma ekuleleni. Ngakho-ke yesimanje strace angajoyina izinqubo ngokundiza.
Isibonelo sokuqandisa :
int main(int argc, char *argv[])
{
(void) argc; (void) argv;
char str[] = "write men";
write(STDOUT_FILENO, str, sizeof(str));
/* Sleep indefinitely or until a signal arrives */
pause();
write(STDOUT_FILENO, str, sizeof(str));
return EXIT_SUCCESS;
}Asakhe uhlelo futhi siqinisekise ukuthi luqandisiwe:
$ gcc examples/write-sleep.c -o write-sleep
$ ./write-sleep
./write-sleep
write me
^C
$Manje ake sizame ukuyijoyina:
$ ./write-sleep &
[1] 15329
write me
$ strace -p 15329
strace: Process 15329 attached
pause(
^Cstrace: Process 15329 detached
<detached ...>Uhlelo luvinjwe ngekholi pause. Ake sibone ukuthi usabela kanjani kumasignali:
$ strace -o write-sleep.log -p 15329 &
strace: Process 15329 attached
$
$ kill -CONT 15329
$ cat write-sleep.log
pause() = ? ERESTARTNOHAND (To be restarted if no handler)
--- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, si_pid=14989, si_uid=1001} ---
pause(
$
$ kill -TERM 15329
$ cat write-sleep.log
pause() = ? ERESTARTNOHAND (To be restarted if no handler)
--- SIGCONT {si_signo=SIGCONT, si_code=SI_USER, si_pid=14989, si_uid=1001} ---
pause() = ? ERESTARTNOHAND (To be restarted if no handler)
--- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=14989, si_uid=1001} ---
+++ killed by SIGTERM +++Sethule uhlelo oluqandisiwe futhi salujoyina sisebenzisa strace. Izinto ezimbili zacaca: ucingo lwesistimu yokumisa isikhashana alinaki amasignali ngaphandle kwezibambi futhi, okuthakazelisayo nakakhulu, abaqaphi be-strace abagcini nje ngokubiza uhlelo, kodwa futhi namasignali angenayo.
Isibonelo: Ukulandelela Izinqubo Zengane
Ukusebenza ngezinqubo ngocingo fork - isisekelo sawo wonke ama-Unixes. Ake sibone ukuthi i-strace isebenza kanjani nesihlahla senqubo sisebenzisa isibonelo "sokuzalela" okulula. :
int main(int argc, char *argv[])
{
pid_t parent_pid = getpid();
pid_t child_pid = fork();
if (child_pid == 0) {
/* A child is born! */
child_pid = getpid();
/* In the end of the day printf is just a call to write(2). */
printf("child (self=%d)n", child_pid);
exit(EXIT_SUCCESS);
}
printf("parent (self=%d, child=%d)n", parent_pid, child_pid);
wait(NULL);
exit(EXIT_SUCCESS);
}Lapha inqubo yasekuqaleni idala inqubo yengane, zombili zibhalela kokuphumayo okujwayelekile:
$ gcc examples/fork-write.c -o fork-write
$ ./fork-write
parent (self=11274, child=11275)
child (self=11275)Ngokuzenzakalela, sizobona kuphela amakholi esistimu asuka enqubweni yomzali:
$ strace -e trace=write -ofork-write.log ./fork-write
child (self=22049)
parent (self=22048, child=22049)
$ cat fork-write.log
write(1, "parent (self=22048, child=22049)"..., 33) = 33
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=22049, si_uid=1001, si_status=0, si_utime=0, si_stime=0} ---
+++ exited with 0 +++Ifulegi likusiza ukuthi ulandelele sonke isihlahla senqubo -f, okuthi strace uqapha izingcingo zesistimu kuzinqubo zengane. Lokhu kwengeza emugqeni ngamunye wokukhiphayo pid inqubo eyenza ukuphuma kwesistimu:
$ strace -f -e trace=write -ofork-write.log ./fork-write
parent (self=22710, child=22711)
child (self=22711)
$ cat fork-write.log
22710 write(1, "parent (self=22710, child=22711)"..., 33) = 33
22711 write(1, "child (self=22711)n", 19) = 19
22711 +++ exited with 0 +++
22710 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=22711, si_uid=1001, si_status=0, si_utime=0, si_stime=0} ---
22710 +++ exited with 0 +++Kulo mongo, ukuhlunga ngeqembu lezingcingo zesistimu kungaba usizo:
$ strace -f -e trace=%process -ofork-write.log ./fork-write
parent (self=23610, child=23611)
child (self=23611)
$ cat fork-write.log
23610 execve("./fork-write", ["./fork-write"], 0x7fff696ff720 /* 63 vars */) = 0
23610 arch_prctl(ARCH_SET_FS, 0x7f3d03ba44c0) = 0
23610 clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f3d03ba4790) = 23611
23610 wait4(-1, <unfinished ...>
23611 exit_group(0) = ?
23611 +++ exited with 0 +++
23610 <... wait4 resumed> NULL, 0, NULL) = 23611
23610 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=23611, si_uid=1001, si_status=0, si_utime=0, si_stime=0} ---
23610 exit_group(0) = ?
23610 +++ exited with 0 +++Ngendlela, yiluphi ucingo lwesistimu olusetshenziselwa ukudala inqubo entsha?
Isibonelo: izindlela zefayela esikhundleni sezibambo
Ukwazi izichazi zefayela kuyasiza impela, kodwa amagama amafayela athile afinyelelwa wuhlelo nawo angaba usizo.
Okulandelayo ubhala umugqa wefayela lesikhashana:
void do_write(int out_fd)
{
char str[] = "write me to a filen";
if (sizeof(str) != write(out_fd, str, sizeof(str))){
perror("write");
exit(EXIT_FAILURE);
}
}
int main(int argc, char *argv[])
{
char tmp_filename_template[] = "/tmp/output_fileXXXXXX";
int out_fd = mkstemp(tmp_filename_template);
if (out_fd == -1) {
perror("mkstemp");
exit(EXIT_FAILURE);
}
do_write(out_fd);
return EXIT_SUCCESS;
}Ngesikhathi socingo olujwayelekile strace izobonisa inani lenombolo yesichazi edluliselwe ocingweni lwesistimu:
$ strace -e trace=write -o write-tmp-file.log ./write-tmp-file
$ cat write-tmp-file.log
write(3, "write me to a filen", 20) = 20
+++ exited with 0 +++Ngefulegi -y Uhlelo lokusebenza lubonisa indlela eya efayeleni lapho isichazi sihambisana khona:
$ strace -y -e trace=write -o write-tmp-file.log ./write-tmp-file
$ cat write-tmp-file.log
write(3</tmp/output_fileCf5MyW>, "write me to a filen", 20) = 20
+++ exited with 0 +++Isibonelo: Ukulandelela Ukufinyelela Kwefayela
Esinye isici esiwusizo: bonisa kuphela amakholi esistimu ahlotshaniswa nefayela elithile. Olandelayo yengeza umugqa efayeleni elingenamthetho eliphasiswe njengengxabano:
void do_write(int out_fd)
{
char str[] = "write me to a filen";
if (sizeof(str) != write(out_fd, str, sizeof(str))){
perror("write");
exit(EXIT_FAILURE);
}
}
int main(int argc, char *argv[])
{
/*
* Path will be provided by the first program argument.
* */
const char *path = argv[1];
/*
* Open an existing file for writing in append mode.
* */
int out_fd = open(path, O_APPEND | O_WRONLY);
if (out_fd == -1) {
perror("open");
exit(EXIT_FAILURE);
}
do_write(out_fd);
return EXIT_SUCCESS;
}
Ngokuzenzakalelayo strace ibonisa ulwazi oluningi olungadingekile. Hlaba umkhosi -P nge-agumenti ibangela uchungechunge lokuphrinta kuphela izingcingo eziya efayeleni elishiwo:
$ strace -y -P/tmp/test_file.log -o write-file.log ./write-file /tmp/test_file.log
$ cat write-file.log
openat(AT_FDCWD, "/tmp/test_file.log", O_WRONLY|O_APPEND) = 3</tmp/test_file.log>
write(3</tmp/test_file.log>, "write me to a filen", 20) = 20
+++ exited with 0 +++Isibonelo: Izinhlelo ezinemicu eminingi
Okusetshenziswayo strace ingasiza futhi uma isebenza nge-multi-threaded . Uhlelo olulandelayo lubhalela okukhiphayo okujwayelekile okuvela ekusakazweni okubili:
void *thread(void *arg)
{
(void) arg;
printf("Secondary thread: workingn");
sleep(1);
printf("Secondary thread: donen");
return NULL;
}
int main(int argc, char *argv[])
{
printf("Initial thread: launching a threadn");
pthread_t thr;
if (0 != pthread_create(&thr, NULL, thread, NULL)) {
fprintf(stderr, "Initial thread: failed to create a thread");
exit(EXIT_FAILURE);
}
printf("Initial thread: joining a threadn");
if (0 != pthread_join(thr, NULL)) {
fprintf(stderr, "Initial thread: failed to join a thread");
exit(EXIT_FAILURE);
};
printf("Initial thread: done");
exit(EXIT_SUCCESS);
}Ngokwemvelo, kufanele ihlanganiswe ngokubingelela okukhethekile kusixhumanisi - ifulege le-pthread:
$ gcc examples/thread-write.c -pthread -o thread-write
$ ./thread-write
/thread-write
Initial thread: launching a thread
Initial thread: joining a thread
Secondary thread: working
Secondary thread: done
Initial thread: done
$Maka umkhosi -f, njengasesimweni sezinqubo ezijwayelekile, izongeza i-pid yenqubo ekuqaleni komugqa ngamunye.
Ngokwemvelo, asikhulumi ngesihlonzi sentambo ngomqondo wokusetshenziswa kwezinga le-POSIX Threads, kodwa mayelana nenombolo esetshenziswa umhleli wemisebenzi ku-Linux. Ngokombono wakamuva, azikho izinqubo noma imicu - kunemisebenzi edinga ukusabalalisa phakathi kwama-cores atholakalayo omshini.
Uma usebenza ngochungechunge oluningi, amakholi esistimu aba maningi kakhulu:
$ strace -f -othread-write.log ./thread-write
$ wc -l thread-write.log
60 thread-write.logKunengqondo ukuzikhawulela ekucubunguleni ukuphathwa nezingcingo zesistimu kuphela write:
$ strace -f -e trace="%process,write" -othread-write.log ./thread-write
$ cat thread-write.log
18211 execve("./thread-write", ["./thread-write"], 0x7ffc6b8d58f0 /* 64 vars */) = 0
18211 arch_prctl(ARCH_SET_FS, 0x7f38ea3b7740) = 0
18211 write(1, "Initial thread: launching a thre"..., 35) = 35
18211 clone(child_stack=0x7f38e9ba2fb0, flags=CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD|CLONE_SYSVSEM|CLONE_SETTLS|CLONE_PARENT_SETTID|CLONE_CHILD_CLEARTID, parent_tidptr=0x7f38e9ba39d0, tls=0x7f38e9ba3700, child_tidptr=0x7f38e9ba39d0) = 18212
18211 write(1, "Initial thread: joining a thread"..., 33) = 33
18212 write(1, "Secondary thread: workingn", 26) = 26
18212 write(1, "Secondary thread: donen", 23) = 23
18212 exit(0) = ?
18212 +++ exited with 0 +++
18211 write(1, "Initial thread: done", 20) = 20
18211 exit_group(0) = ?
18211 +++ exited with 0 +++Ngokwesibonelo, imibuzo. Iyiphi ikholi yesistimu esetshenziselwa ukudala uchungechunge olusha? Le kholi yochungechunge ihluke kanjani ekubizeni izinqubo?
I-Master class: cubungula isitaki ngesikhathi socingo lwesistimu
Eyodwa esanda kuvela strace amakhono - ukubonisa inqwaba yezingcingo zokusebenza ngesikhathi socingo lwesistimu. Kulula :
void do_write(void)
{
char str[] = "write me to stdoutn";
if (sizeof(str) != write(STDOUT_FILENO, str, sizeof(str))){
perror("write");
exit(EXIT_FAILURE);
}
}
int main(int argc, char *argv[])
{
do_write();
return EXIT_SUCCESS;
}Ngokwemvelo, okuphumayo kohlelo kuba kakhulu, futhi, ngaphezu kwefulegi -k (i-call stack display), kunengqondo ukuhlunga izingcingo zesistimu ngegama:
$ gcc examples/write-simple.c -o write-simple
$ strace -k -e trace=write -o write-simple.log ./write-simple
write me to stdout
$ cat write-simple.log
write(1, "write me to stdoutn", 20) = 20
> /lib/x86_64-linux-gnu/libc-2.27.so(__write+0x14) [0x110154]
> /home/vkazanov/projects-my/strace-post/write-simple(do_write+0x50) [0x78a]
> /home/vkazanov/projects-my/strace-post/write-simple(main+0x14) [0x7d1]
> /lib/x86_64-linux-gnu/libc-2.27.so(__libc_start_main+0xe7) [0x21b97]
> /home/vkazanov/projects-my/strace-post/write-simple(_start+0x2a) [0x65a]
+++ exited with 0 +++Isigaba esikhulu: umjovo wephutha
Futhi esinye isici esisha futhi esiwusizo kakhulu: umjovo wephutha. Lapha , ukubhala imigqa emibili emfudlaneni ophumayo:
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
void do_write(const char *str, ssize_t len)
{
if (len != write(STDOUT_FILENO, str, (size_t)len)){
perror("write");
exit(EXIT_FAILURE);
}
}
int main(int argc, char *argv[])
{
(void) argc; (void) argv;
char str1[] = "write me 1n";
do_write(str1, sizeof(str1));
char str2[] = "write me 2n";
do_write(str2, sizeof(str2));
return EXIT_SUCCESS;
}Masilandele zombili izingcingo ezibhalayo:
$ gcc examples/write-twice.c -o write-twice
$ ./write-twice
write me 1
write me 2
$ strace -e trace=write -owrite-twice.log ./write-twice
write me 1
write me 2
$ cat write-twice.log
write(1, "write me 1n", 12) = 12
write(1, "write me 2n", 12) = 12
+++ exited with 0 +++Manje sisebenzisa isisho injectukufaka iphutha EBADF kuzo zonke bhala izingcingo:
$ strace -e trace=write -e inject=write:error=EBADF -owrite-twice.log ./write-twice
$ cat write-twice.log
write(1, "write me 1n", 12) = -1 EBADF (Bad file descriptor) (INJECTED)
write(3, "write: Bad file descriptorn", 27) = -1 EBADF (Bad file descriptor) (INJECTED)
+++ exited with 1 +++Kuyathakazelisa ukuthi yimaphi amaphutha abuyiswayo konke izinselele write, okufaka phakathi ucingo olufihlwe ngenxa yokwesaba. Kunengqondo ukubuyisela iphutha okokuqala ngqa:
$ strace -e trace=write -e inject=write:error=EBADF:when=1 -owrite-twice.log ./write-twice
write: Bad file descriptor
$ cat write-twice.log
write(1, "write me 1n", 12) = -1 EBADF (Bad file descriptor) (INJECTED)
write(3, "write: Bad file descriptorn", 27) = 27
+++ exited with 1 +++Noma owesibili:
$ strace -e trace=write -e inject=write:error=EBADF:when=2 -owrite-twice.log ./write-twice
write me 1
write: Bad file descriptor
$ cat write-twice.log
write(1, "write me 1n", 12) = 12
write(1, "write me 2n", 12) = -1 EBADF (Bad file descriptor) (INJECTED)
write(3, "write: Bad file descriptorn", 27) = 27
+++ exited with 1 +++Akudingekile ukucacisa uhlobo lwephutha:
$ strace -e trace=write -e fault=write:when=1 -owrite-twice.log ./write-twice
$ cat write-twice.log
write(1, "write me 1n", 12) = -1 ENOSYS (Function not implemented) (INJECTED)
write(3, "write: Function not implementedn", 32) = 32
+++ exited with 1 +++Ngokuhlanganiswa namanye amafulegi, ungakwazi "ukuphula" ukufinyelela kufayela elithile. Isibonelo:
$ strace -y -P/tmp/test_file.log -e inject=file:error=ENOENT -o write-file.log ./write-file /tmp/test_file.log
open: No such file or directory
$ cat write-file.log
openat(AT_FDCWD, "/tmp/test_file.log", O_WRONLY|O_APPEND) = -1 ENOENT (No such file or directory) (INJECTED)
+++ exited with 1 +++Ngaphandle komjovo wephutha, yethula ukubambezeleka lapho ushaya izingcingo noma wamukela amasignali.
I-Afterword
Okusetshenziswayo strace - ithuluzi elilula nelithembekile. Kodwa ngaphezu kwezingcingo zesistimu, ezinye izici zokusebenza kwezinhlelo kanye nesistimu yokusebenza zingalungiswa. Isibonelo, ingakwazi ukulandelela amakholi kumalabhulali axhumeke ngamandla. , bangabheka ukusebenza kwesistimu yokusebenza ΠΈ , futhi ikuvumela ukuthi uphenye ngokujulile ukusebenza kohlelo . Noma kunjalo, kunjalo strace - umugqa wokuqala wokuzivikela uma kunezinkinga ngezinhlelo zami kanye nezabanye abantu, futhi ngiyisebenzisa okungenani izikhathi ezimbalwa ngesonto.
Ngamafuphi, uma uthanda i-Unix, funda man 1 strace futhi uzizwe ukhululekile ukulunguza ezinhlelweni zakho!
Source: www.habr.com