Search
- Filter Results
- Location
- Classification
- Include attachments
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/08%3A_Behind_the_processWe also know, however, an executable does not live its life in memory, but spends most of its life as a file on a disk waiting to be loaded an run. Since a file is, in essence, simply a contiguous arr...We also know, however, an executable does not live its life in memory, but spends most of its life as a file on a disk waiting to be loaded an run. Since a file is, in essence, simply a contiguous array of bits, all systems come up with methods of organising code and data within files for on-demand execution. The bits and bytes of the file are generally in a format ready to be placed in memory and interpreted directly by processor hardware.
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/06%3A_Virtual_Memory/6.06%3A_Virtual_AddressesWhen a program accesses memory, it does not know or care where the physical memory backing the address is stored. It knows it is up to the operating system and hardware to work together to map locate ...When a program accesses memory, it does not know or care where the physical memory backing the address is stored. It knows it is up to the operating system and hardware to work together to map locate the right physical address and thus provide access to the data it wants. Thus we term the address a program is using to access memory a virtual address. A virtual address consists of two parts; the page and an offset into that page.
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/07%3A_The_Toolchain/7.04%3A_AssemblerThe assembly code outputted by the compiler is still in a human readable form, should you know the specifics of the assembly code for the processor. Developers will often take a peek at the assembly o...The assembly code outputted by the compiler is still in a human readable form, should you know the specifics of the assembly code for the processor. Developers will often take a peek at the assembly output to manually check that the code is the most optimised or to discover any bugs in the compiler (this is more common than one might think, especially when the compiler is being very aggressive with optimisations).
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/04%3A_The_Operating_System/4.03%3A_System_CallsSystem calls are how userspace programs interact with the kernel.
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/01%3A_General_Unix_and_Advanced_C/1.03%3A_File_DescriptorsThe abstraction here is the mount point; mounting a file system has the dual purpose of setting up a mapping so the file system knows the underlying device that provides the storage and the kernel kno...The abstraction here is the mount point; mounting a file system has the dual purpose of setting up a mapping so the file system knows the underlying device that provides the storage and the kernel knows that files opened under that mount-point should be directed to the file system driver.
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/09%3A_Dynamic_Linking/9.02%3A_Global_Offset_TablesOn IA64 (the architecture which the library was compiled for) the register r1 is known as the global pointer and always points to where the .got section is loaded into memory. So before the program be...On IA64 (the architecture which the library was compiled for) the register r1 is known as the global pointer and always points to where the .got section is loaded into memory. So before the program begins, the dynamic linker will have fixed up the relocation to ensure that the value of the memory at offset 0x10588 is the address of the global variable i!
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/01%3A_General_Unix_and_Advanced_C
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/06%3A_Virtual_Memory
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/04%3A_The_Operating_System/4.01%3A_The_role_of_the_operating_systemThe operating system underpins the entire operation of the modern computer.
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/09%3A_Dynamic_Linking/9.03%3A_LibrariesWe know from before that r1 will be pointing to the GOT, so this is saying "store in r15 80 bytes into the GOT". The next thing we do is load into r16 the value stored in this location in the GOT, and...We know from before that r1 will be pointing to the GOT, so this is saying "store in r15 80 bytes into the GOT". The next thing we do is load into r16 the value stored in this location in the GOT, and post increment the value in r15 by 8 bytes. The second value is the global pointer value for the dynamic linker, and the third value is the address of the function that finds and fixes up the symbol.
- https://eng.libretexts.org/Bookshelves/Computer_Science/Programming_and_Computation_Fundamentals/Computer_Science_from_the_Bottom_Up_(Wienand)/05%3A_The_Process/5.02%3A_Elements_of_a_processGenerally this leads to a crash, but some people realised that if they overwrote just enough memory to place a specific value in the return address part of the stack frame, when the function completed...Generally this leads to a crash, but some people realised that if they overwrote just enough memory to place a specific value in the return address part of the stack frame, when the function completed rather than returning to the correct place (where it was called from) they could make it return into the data they just sent.
