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� POSIX-�� (�� fork()) � �� (�� exec*()), �� .
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� Linux �� execve().
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- "All process attributes are preserved during an execve(), except the following:
  - The dispositions of any signals that are being caught are reset to the default (signal(7)).
  - Any alternate signal stack is not preserved (sigaltstack(2)).
  - Memory mappings are not preserved (mmap(2)).
  - Attached System V shared memory segments are detached (shmat(2)).
  - POSIX shared memory regions are unmapped (shm_open(3)).
  - Open POSIX message queue descriptors are closed (mq_overview(7)).
  - Any open POSIX named semaphores are closed (sem_overview(7)).
  - POSIX timers are not preserved (timer_create(2)).
  - Any open directory streams are closed (opendir(3)).
  - Memory locks are not preserved (mlock(2), mlockall(2)).
  - Exit handlers are not preserved (atexit(3), on_exit(3)).
  - The floating-point environment is reset to the default (see fenv(3)).
- The process attributes in the preceding list are all specified in POSIX.1-2001. The following Linux-specific process attributes are also not preserved during an execve():
  - The prctl(2) PR_SET_DUMPABLE flag is set, unless a set-user-ID or set-group ID program is being executed, in which case it is cleared.
  - The prctl(2) PR_SET_KEEPCAPS flag is cleared.
  - (Since Linux 2.4.36 / 2.6.23) If a set-user-ID or set-group-ID program is being executed, then the parent death signal set by prctl(2) PR_SET_PDEATHSIG flag is cleared.
  - The process name, as set by prctl(2) PR_SET_NAME (and displayed by ps -o comm), is reset to the name of the new executable file.
  - The SECBIT_KEEP_CAPS securebits flag is cleared. See capabilities(7).
  - The termination signal is reset to SIGCHLD (see clone(2)).
- Note the following further points:
  - All threads other than the calling thread are destroyed during an execve(). Mutexes, condition variables, and other pthreads objects are not preserved.
  - The equivalent of setlocale(LC_ALL, "C") is executed at program start-up.
  - POSIX.1-2001 specifies that the dispositions of any signals that are ignored or set to the default are left unchanged. POSIX.1-2001 specifies one exception: if SIGCHLD is being ignored, then an implementation may leave the disposition unchanged or reset it to the default; Linux does the former.
  - Any outstanding asynchronous I/O operations are canceled (aio_read(3), aio_write(3)).
  - For the handling of capabilities during execve(), see capabilities(7)."
- �� (�� , � �� FD_CLOEXEC), uid/gid (�� , �� setuid/setgid), capability, security context (�� LSM).
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- �� Linux ��, �� , �� (format module)
  - �� (a.out, ELF, BFLT), �� wrapper-� (�� binfmt_script � binfmt_misc)
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- �� dsohowto: "The main aspect is the binary format. This is the format which is used to describe the application code. Long gone are the days that it was sufficient to provide a memory dump. Multi-process systems need to identify different parts of the file containing the program such as the text, data, and debug information parts. For this, binary formats were introduced early on. Commonly used in the early Unix-days were formats such as a.out or COFF. These binary formats were not designed with shared libraries in mind and this clearly shows."
- �� . �� .
- Linkers and loaders, ch. 1: "loaders perform several related but conceptually separate actions.
  - Program loading: Copy a program from secondary storage (which since about 1968 invariably means a disk) into main memory so it's ready to run. In some cases loading just involves copying the data from disk to memory, in others it involves allocating storage, setting protection bits, or arranging for virtual memory to map virtual addresses to disk pages.
  - Relocation: Compilers and assemblers generally create each file of object code with the program addresses starting at zero, but few computers let you load your program at location zero. If a program is created from multiple subprograms, all the subprograms have to be loaded at non-overlapping addresses. Relocation is the process of assigning load addresses to the various parts of the program, adjusting the code and data in the program to reflect the assigned addresses. In many systems, relocation happens more than once. It's quite common for a linker to create a program from multiple subprograms, and create one linked output program that starts at zero, with the various subprograms relocated to locations within the big program. Then when the program is loaded, the system picks the actual load address and the linked program is relocated as a whole to the load address.
  - Symbol resolution: When a program is built from multiple subprograms, the references from one subprogram to another are made using symbols; a main program might use a square root routine called sqrt, and the math library defines sqrt. A linker resolves the symbol by noting the location assigned to sqrt in the library, and patching the caller's object code to so the call instruction refers to that location."

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