poから始めるlldb

Transcript

1. po͔Β࢝ΊΔlldb
   ະདྷେ×اۀΤϯδχΞ ՆͷLTେձ
   

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2. • ࠤ౻ ರ໵ (@natmark)
   • ະདྷେ ஌ೳγεςϜίʔε 4೥
   • γεςϜιϑτ΢ΣΞݚ (127Lab)
   

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3. ProcessingίʔυΛiOS্Ͱ
   ར༻Մೳʹ͢ΔϥΠϒϥϦ
   Xcode File TemplateΛ؅ཧ
   ͢ΔCLIπʔϧ
   natmark/ProcessingKit natmark/Donut
   

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4. ʲએ఻ʳiOSDC Japan 2018ʹొஃ͠·͢ʂ
   

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5. Έͳ͞ΜLLDB࢖ͬͯ·͔͢
   

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6. ࠓ೔͸LLDBʹ͍ͭͯ࿩͠·͢ɻ
   ͱݴͬͯ΋ɺ5෼͔͠ͳ͍ͷͰ
   

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7. • LLDBʹ͍ͭͯ
   • ͳͥະདྷେੜʹLLDBͳͷ͔
   • LLDBͷ؆୯ͳ࢖͍ํ
   • (͕࣌ؒ༨Ε͹) LLDBΛ࢖ͬͨগ࣮͠ફతͳσ
   όοά๏ʹ͍ͭͯ
   ΛૣޱͰ঺հ͠·͢ʂ
   

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8. LLDBͱ͸ʁ
   

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9. Low Level Debugger
   

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10. ࣍ੈ୅ߴੑೳσόοΨ
    

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11. LLDB
    • ιϑτ΢ΣΞσόοΨ
    • LLVMϓϩδΣΫτͷҰ෦ͱͯ͠։ൃ
    • Clang[Ϋϥϯ] දࣜղੳػ΍LLVMٯΞηϯϒϥͳͲ
    Λ׆༻ͨ͠࠶ར༻Մೳͳίϯϙʔωϯτͷू·Γ
    • XcodeͷσϑΥϧτσόοΨ
    • Swift/C/C++ /Objective-C,/Objective-C++ͳͲͷ
    ίʔυΛ࣮ߦՄೳ
    

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12. ͳͥະདྷେੜʹLLDBͳͷ͔
    

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13. • ະདྷେͷCݴޠͷߨٛ͸MacࣨͰߦ͏
    • Macʹ͸ඪ४ͰLLDBೖͬͯΔʂ(※1)
    • ະདྷେͷߨٛͰσόοΨʔͷ࢖͍ํΛڭΘΒͳ͍…
    ※1 ΋͔ͨ͠͠ΒXcodeೖΕͨλΠϛϯά͔΋
    

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14. σόοάʹprintfΛͨ͘͞Μॻ͍ͯ
    ͍·ͤΜ͔…?
    

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15. σόοά༻ʹॻ͍ͨprintfͰɺ
    ppchkall(※1)͕௨Βͳ͔ͬͨܦݧ͋
    Γ·ͤΜ͔…ʁ
    ※1 ppchkall: ະདྷେͷϓϩάϥϛϯάجૅͷ՝୊νΣοΫίϚϯυ
    ςετέʔεͷग़ྗͱඪ४ग़ྗΛൺ΂ͯdiffग़͢΍ͭ
    

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16. ๻͸͋Γ·͢ʂʂʂʂʂʂʂ
    

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17. σόοΨΛ࢖͑ΔΑ͏ʹͳΖ͏ʂ
    ͱ͍͏࿩
    

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18. LLDBΛ࢖ͬͯΈΔ
    

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19. address.c
    #include
    void addrcat(char *a, char *d) {
    while(*a) { // ຤ඌ·ͰϙΠϯλΛਐΊΔ
    a++;
    }
    *a++ = '@'; // @Λ௥Ճ͢Δ
    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;
    }
    

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20. address.cͷίϯύΠϧ
    $ gcc -o address -g address.c
    -g Generate source-level debug information
    

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21. $ ls
    address address.c address.dSYM
    address.dSYM : Ϗϧυ࣌ʹग़ྗ͞ΕΔσόοάγϯϘϧϑΝΠϧ
    

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22. $ 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
    1015006@fun.ac.jp
    Process 21476 exited with status = 0 (0x00000000)
    

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23. LLDBΛىಈ͢Δ͜ͱ͕Ͱ͖ͨ
    

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24. ϒϨʔΫϙΠϯτΛஔ͍ͯɺ్தͰ
    ॲཧΛࢭΊͯΈΔ
    

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25. 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
    

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26. (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);
    

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27. ม਺ͷ஋Λͷ͍ͧͯΈΔ
    

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28. (lldb) po account //po(expression -O --) ࣜΛධՁɺ໭Γ
    ஋ͷܕʹ͋ΘͤͨϑΥʔϚοτͰදࣔ
    “1015006”
    

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29. ࣮ߦதͷϓϩάϥϜͷม਺Λ೷͘͜
    ͱ͕Ͱ͖ͨ
    

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30. Ͱ΋ɺϝʔϧΞυϨεؒҧ͑ͯೖྗ
    ͯ͠͠·ͬͨ…
    (ະདྷେͷϝʔϧΞυϨε͸ֶ੶൪߸ͷલʹb͕ඞཁ)
    

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31. ࣮ߦதͷม਺ͷத਎Λมߋͯ͠ΈΔ
    

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32. (lldb) po strcpy(account, "b1015006");
    0x00007ffeefbfeca0
    (lldb) po account
    “b1015006
    

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33. ࣮ߦதͷม਺Λߋ৽Ͱ͖ͨ
    

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34. ؔ਺ΛεςοϓɾΦʔόʔͯ͠ɺ
    1ߦ෼ॲཧΛਐΊͯΈΔ
    

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35. (lldb) next //1ߦ෼ॲཧΛਐΊΔɻؔ਺͸εςοϓΦʔόʔ
    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.
    

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36. (lldb) po account
    “b1015006@fun.ac.jp"
    

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37. addrcatؔ਺͕ͪΌΜͱಈ͍ͯΔ͜
    ͱ΋֬ೝͰ͖ͨ
    

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38. ͜ΕͰCݴޠͷߨٛͰɺ
    LLDBΛ࢖ͬͨ؆୯ͳσόοά͕Ͱ
    ͖ΔΑ͏ʹͳͬͨ
    

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39. ΊͰͨ͠ΊͰͨ͠
    

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40. ͕࣌ؒ༨ͬͨͷͰɺͪΐͬͱ
    ࣮ફతͳσόοά๏Λ঺հ͠·͢
    

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41. Symbolic Breakpoint
    

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42. • Symbolic Breakpoint
    • ϒϨʔΫ͍ͤͨ͞Ϋϥεͱϝιου໊Λॻ
    ͘ͱɺͦͷϝιου͕࣮ߦ͞ΕͨλΠϛϯ
    άͰϒϨʔΫͰ͖Δ
    • ϓϥΠϕʔτϥΠϒϥϦͳͲɺϝιου໊
    ͸෼͔͍ͬͯΔ΋ͷͷBreakpointΛுΕͳ
    ͍৔߹ʹศར
    

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43. (lldb) breakpoint set --name “addrcat" //addrcatͱ͍͏ؔ਺ʹϒϨʔΫϙΠϯτΛுΔ
    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
    2
    3 void addrcat(char *a, char *d) {
    -> 4 while(*a) { // ຤ඌ·ͰϙΠϯλΛਐΊΔ
    5 a++;
    6 }
    7 *a++ = '@'; // @Λ௥Ճ͢Δ
    Target 0: (address) stopped.
    

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44. Breakpoint Commands
    &
    Thread jump
    

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45. • commands
    • ϒϨʔΫϙΠϯτʹΑͬͯϓϩάϥϜ͕ఀ
    ࢭͨ࣌͠ɺϒϨʔΫϙΠϯτʹରͯ͠Ұ࿈
    ͷίϚϯυͷىಈΛࢦఆ͢Δ͜ͱ͕Ͱ͖Δ
    • jump
    • ϓϩάϥϜΧ΢ϯλͷ஋Λ৽͍͠ΞυϨε
    ʹมߋͰ͖Δ
    

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46. (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);
    

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47. (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
    ͨΊɺग़ྗ͞Εͨaccount͸domain͕݁߹͞Ε͍ͯͳ͍
    Process 23852 exited with status = 0 (0x00000000)
    

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48. ָ͍͠LLDBϥΠϑΛʂʂ
    

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