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poから始めるlldb
Atsuya Sato
July 14, 2018
Technology
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poから始めるlldb
Atsuya Sato
July 14, 2018
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Transcript
po͔Β࢝ΊΔlldb ະདྷେ×اۀΤϯδχΞ ՆͷLTେձ
• ࠤ౻ ರ (@natmark) • ະདྷେ ೳγεςϜίʔε 4 • γεςϜιϑτΣΞݚ
(127Lab)
ProcessingίʔυΛiOS্Ͱ ར༻Մೳʹ͢ΔϥΠϒϥϦ Xcode File TemplateΛཧ ͢ΔCLIπʔϧ natmark/ProcessingKit natmark/Donut
ʲએʳiOSDC Japan 2018ʹొஃ͠·͢ʂ
Έͳ͞ΜLLDBͬͯ·͔͢
ࠓLLDBʹ͍ͭͯ͠·͢ɻ ͱݴͬͯɺ5͔͠ͳ͍ͷͰ
• LLDBʹ͍ͭͯ • ͳͥະདྷେੜʹLLDBͳͷ͔ • LLDBͷ؆୯ͳ͍ํ • (͕࣌ؒ༨Ε) LLDBΛͬͨগ࣮͠ફతͳσ όοά๏ʹ͍ͭͯ
ΛૣޱͰհ͠·͢ʂ
LLDBͱʁ
Low Level Debugger
࣍ੈߴੑೳσόοΨ
LLDB • ιϑτΣΞσόοΨ • LLVMϓϩδΣΫτͷҰ෦ͱͯ͠։ൃ • Clang[Ϋϥϯ] දࣜղੳػLLVMٯΞηϯϒϥͳͲ Λ׆༻ͨ͠࠶ར༻Մೳͳίϯϙʔωϯτͷू·Γ •
XcodeͷσϑΥϧτσόοΨ • Swift/C/C++ /Objective-C,/Objective-C++ͳͲͷ ίʔυΛ࣮ߦՄೳ
ͳͥະདྷେੜʹLLDBͳͷ͔
• ະདྷେͷCݴޠͷߨٛMacࣨͰߦ͏ • Macʹඪ४ͰLLDBೖͬͯΔʂ(※1) • ະདྷେͷߨٛͰσόοΨʔͷ͍ํΛڭΘΒͳ͍… ※1 ͔ͨ͠͠ΒXcodeೖΕͨλΠϛϯά͔
σόοάʹprintfΛͨ͘͞Μॻ͍ͯ ͍·ͤΜ͔…?
σόοά༻ʹॻ͍ͨprintfͰɺ ppchkall(※1)͕௨Βͳ͔ͬͨܦݧ͋ Γ·ͤΜ͔…ʁ ※1 ppchkall: ະདྷେͷϓϩάϥϛϯάجૅͷ՝νΣοΫίϚϯυ ςετέʔεͷग़ྗͱඪ४ग़ྗΛൺͯdiffग़ͭ͢
͋Γ·͢ʂʂʂʂʂʂʂ
σόοΨΛ͑ΔΑ͏ʹͳΖ͏ʂ ͱ͍͏
LLDBΛͬͯΈΔ
address.c #include <stdio.h> void addrcat(char *a, char *d) { while(*a)
{ // ඌ·ͰϙΠϯλΛਐΊΔ a++; } *a++ = '@'; // @ΛՃ͢Δ while(*d) { // dͷࢦ͢ΞυϨεʹจࣈ͕֨ೲ͞Ε͍ͯΔؒ *a++ = *d++; // aʹίϐʔ } } int main(void) { char account[100]; char domain[100]; scanf("%s", account); scanf("%s", domain); addrcat(account, domain); printf("%s\n", account); return 0; }
address.cͷίϯύΠϧ $ gcc -o address -g address.c -g Generate source-level
debug information
$ ls address address.c address.dSYM address.dSYM : Ϗϧυ࣌ʹग़ྗ͞ΕΔσόοάγϯϘϧϑΝΠϧ
$ lldb address (lldb) target create “address” Current executable set
to ‘address’ (x86_64). (lldb) run //ϓϩάϥϜΛ࣮ߦ͢Δ Process 21476 launched: '/Users/AtsuyaSato/Desktop/test-lldb/ address' (x86_64) 1015006 fun.ac.jp
[email protected]
Process 21476 exited with status = 0 (0x00000000)
LLDBΛىಈ͢Δ͜ͱ͕Ͱ͖ͨ
ϒϨʔΫϙΠϯτΛஔ͍ͯɺ్தͰ ॲཧΛࢭΊͯΈΔ
addrcat(account, domain); (lldb) breakpoint set --file address.c --line 20
//address.cͷ20ߦ ʹϒϨʔΫϙΠϯτΛுΔ Breakpoint 1: where = address`main + 91 at address.c:20, address = x0000000100000f1bb1015006
(lldb) run Process 22308 launched: '/Users/AtsuyaSato/Desktop/test-lldb/address' (x86_64) 1015006 fun.ac.jp Process
22308 stopped * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1 frame #0: 0x0000000100000f1b address`main at address.c:20 17 scanf("%s", account); 18 scanf("%s", domain); 19 -> 20 addrcat(account, domain); 21 printf("%s\n", account); 22 return 0; 23 } Target 0: (address) stopped. addrcat(account, domain);
มͷΛͷ͍ͧͯΈΔ
(lldb) po account //po(expression -O --) ࣜΛධՁɺΓ ͷܕʹ͋ΘͤͨϑΥʔϚοτͰදࣔ “1015006”
࣮ߦதͷϓϩάϥϜͷมΛ͘͜ ͱ͕Ͱ͖ͨ
ͰɺϝʔϧΞυϨεؒҧ͑ͯೖྗ ͯ͠͠·ͬͨ… (ະདྷେͷϝʔϧΞυϨεֶ੶൪߸ͷલʹb͕ඞཁ)
࣮ߦதͷมͷதΛมߋͯ͠ΈΔ
(lldb) po strcpy(account, "b1015006"); 0x00007ffeefbfeca0 (lldb) po account “b1015006
࣮ߦதͷมΛߋ৽Ͱ͖ͨ
ؔΛεςοϓɾΦʔόʔͯ͠ɺ 1ߦॲཧΛਐΊͯΈΔ
(lldb) next //1ߦॲཧΛਐΊΔɻؔεςοϓΦʔόʔ Process 22308 stopped * thread #1, queue
= 'com.apple.main-thread', stop reason = step over frame #0: 0x0000000100000f31 address`main at address.c:21 18 scanf("%s", domain); 19 20 addrcat(account, domain); -> 21 printf("%s\n", account); 22 return 0; 23 } Target 0: (address) stopped.
(lldb) po account “
[email protected]
"
addrcat͕ؔͪΌΜͱಈ͍ͯΔ͜ ͱ֬ೝͰ͖ͨ
͜ΕͰCݴޠͷߨٛͰɺ LLDBΛͬͨ؆୯ͳσόοά͕Ͱ ͖ΔΑ͏ʹͳͬͨ
ΊͰͨ͠ΊͰͨ͠
͕࣌ؒ༨ͬͨͷͰɺͪΐͬͱ ࣮ફతͳσόοά๏Λհ͠·͢
Symbolic Breakpoint
• Symbolic Breakpoint • ϒϨʔΫ͍ͤͨ͞Ϋϥεͱϝιου໊Λॻ ͘ͱɺͦͷϝιου͕࣮ߦ͞ΕͨλΠϛϯ άͰϒϨʔΫͰ͖Δ • ϓϥΠϕʔτϥΠϒϥϦͳͲɺϝιου໊ ͔͍ͬͯΔͷͷBreakpointΛுΕͳ
͍߹ʹศར
(lldb) breakpoint set --name “addrcat" //addrcatͱ͍͏ؔʹϒϨʔΫϙΠϯτΛுΔ Breakpoint 5: where =
address`addrcat + 12 at address.c:4, address = 0x0000000100000e4c (lldb) run Process 23416 launched: '/Users/AtsuyaSato/Desktop/test-lldb/address' (x86_64) b1015006 fun.ac.jp Process 23416 stopped * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 5.1 frame #0: 0x0000000100000e4c address`addrcat(a="b1015006", d="fun.ac.jp") at address.c:4 1 #include <stdio.h> 2 3 void addrcat(char *a, char *d) { -> 4 while(*a) { // ඌ·ͰϙΠϯλΛਐΊΔ 5 a++; 6 } 7 *a++ = '@'; // @ΛՃ͢Δ Target 0: (address) stopped.
Breakpoint Commands & Thread jump
• commands • ϒϨʔΫϙΠϯτʹΑͬͯϓϩάϥϜ͕ఀ ࢭͨ࣌͠ɺϒϨʔΫϙΠϯτʹରͯ͠Ұ࿈ ͷίϚϯυͷىಈΛࢦఆ͢Δ͜ͱ͕Ͱ͖Δ • jump • ϓϩάϥϜΧϯλͷΛ৽͍͠ΞυϨε
ʹมߋͰ͖Δ
(lldb) breakpoint set --line 20 Breakpoint 1: where = address`main
+ 91 at address.c:20, address = 0x0000000100000f1b (lldb) breakpoint command add 1 //1൪ͷBreakpointʹίϚ ϯυΛઃఆ Enter your debugger command(s). Type 'DONE' to end. > thread jump --by 1 // ݱࡏͷεϨουͰ1ߦεΩοϓ͢Δ (lldb) breakpoint modify --auto-continue 1 // 1൪ͷBreakpoint ͕ϒϨʔΫͨ͠ࡍʹࣗಈͰcontinue͢ΔΑ͏ʹมߋ addrcat(account, domain);
(lldb) run Process 23852 launched: '/Users/AtsuyaSato/Desktop/ test-lldb/address' (x86_64) b1015006 fun.ac.jp
(lldb) thread jump --by 1 //commandʹΑͬͯίʔυΠϯ δΣΫγϣϯ͞Εͨ b1015006 //addrcat(account, domain); ͕εΩοϓ͞Εͨ ͨΊɺग़ྗ͞Εͨaccountdomain͕݁߹͞Ε͍ͯͳ͍ Process 23852 exited with status = 0 (0x00000000)
ָ͍͠LLDBϥΠϑΛʂʂ