Debugging With GNU Debugger GDB

Debugging With GNU Debugger GDB

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  Debugging With GNU DebuggerGDB By Kyaw Thiha ICEH, ICWAPT, CWSE, Debugging with debug symbol file
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  Contents • What isDebugging • What is Debugger? • What are Debugger Symbols? • Debugging Symbols • Ripping Symbols off a Binary • Adding Debug Symbols to a Binary • What in Symbols Files • Stripping Symbols off a Binary • Setting a Breakpoint • Disable / Enable / Delete Breakpoint
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  Contents • Examine Memory •Modify CPU and Memory • Working with variables, functions in GDB
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  What is Debugging? • “De” + “Bug” = Debug • finding and reducing the number of bugs, in a computer program or a piece of electronic hardware, • software and electronic systems have various common debugging techniques have expanded with more methods to detect anomalies, assess impact,
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  What is Debugger? • A special program used to find errors (bugs) in other programs. A debugger allows a programmer to stop a program at any point and examine and change the values of variables. • Examples – -GNU Debugger -Intel Debugger -softIce -WinDBG
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  What are DebuggerSymbols ? • information that expresses which programming-language constructs generated a specific piece of machine code in a given executable module. • embedded in the binary itself or separate file
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  What are DebuggerSymbols ? • Kyaw Thiha (handsome) • Young (25) • Skinny (120 lb) • IT ( Information Security) • Myanmar (Yangon) • Kyaw Thiha • Young • skinny • IT • Myanmar
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  Debugging Symbols • GCCuse –g option • GCC -ggdb for GDB specific symbols • Need to be explicitly mentioned at Compile time • Type -DWARF 2 -COFF -XCOFF -Stabs
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  Ripping Symbols Offa Binary • Objcopy • objcopy –only-keep-debug rip_from_binary_debug_file
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  Stripping Symbols offa Binary • Strip • --strip-debug –strip-unneeded binary_file
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  Adding Debug Symbolsto a Binary • Add it in the Binary itself objcopy –add-gnu-debuglink= debug_file • Load the symbol file within GDB symbol-file file_name
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  What in SymbolsFile ? • Info file • Info sources • Info variable • Info scope function_name • Info function • maint print symbols file_name
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  Setting a Breakpoint •What is a Breakpoint? • intentional stopping or pausing place in a program, sometimes simply referred to as a pause. • Criteia can be “about to execute an instruction” • Debugger allows to inspect / modify CPU , Register , Memory , Data etc. • Setting a Breakpoint • break Line_number/Function/address • View Breakpoint • Info breakpoints
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  Disable / Enable/ Delete Breakpoint • Enable xxxxxxxxxx • Disable xxxxxxxxx • Delete xxxxxxxxx
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  Examine Memory • usagex • x/FMT address or print • Address – Memory address • FMT – is repeated count followed by format letter and count letter. • Format letter: o(octal) , x(hex), d(decimal), u(unsigned letter), t(binary) , f(float) , etc • Size letter: b(byte),h(halfword) , w(word) , g(giant, 8bytes)
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  Modify CPU andMemory • Modify Memory • Set {int} address = value • Modify CPU • set register = address
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  Working with variables, functionsin GDB • Variables • Set new_variable = value • Set exiting_variable = net_variable • Functions • call function_name