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- /* -*- mode:c; c-basic-offset:4; tab-width:4; indent-tabs-mode:t; mode:auto-fill; fill-column:78; -*- */
- /* vim: set ts=4 sw=4 et tw=78 fo=cqt wm=0: */
- /* This is the canonical entry point, usually the first thing in the text
- segment. The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry
- point runs, most registers' values are unspecified, except for:
- %rdx Contains a function pointer to be registered with `atexit'.
- This is how the dynamic linker arranges to have DT_FINI
- functions called for shared libraries that have been loaded
- before this code runs.
- %rsp The stack contains the arguments and environment:
- 0(%rsp) argc
- 8(%rsp) argv[0]
- ...
- (8*argc)(%rsp) NULL
- (8*(argc+1))(%rsp) envp[0]
- ...
- NULL
- */
- .text
- .globl shim_start
- .type shim_start,@function
- shim_start:
- .cfi_startproc
- # Clear the frame pointer. The ABI suggests this be done, to mark
- # the outermost frame obviously.
- xorq %rbp, %rbp
- # Arguments for shim_init:
- movq 0(%rsp), %rdi # argc
- leaq 8(%rsp), %rsi # args
- # Required by System V AMD64 ABI.
- andq $~0xF, %rsp
- callq *shim_init@GOTPCREL(%rip)
- # TODO: Call initial %rdi to execute atexit callbacks.
- .cfi_endproc
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