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@@ -4,10 +4,145 @@
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*/
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+/* This is the canonical entry point, usually the first thing in the text
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+ segment. The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry
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+ point runs, most registers' values are unspecified, except for:
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+
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+ %rdx Contains a function pointer to be registered with `atexit'.
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+ This is how the dynamic linker arranges to have DT_FINI
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+ functions called for shared libraries that have been loaded
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+ before this code runs.
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+
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+ %rsp The stack contains the arguments and environment:
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+ 0(%rsp) argc
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+ 8(%rsp) argv[0]
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+ ...
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+ (8*argc)(%rsp) NULL
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+ (8*(argc+1))(%rsp) envp[0]
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+ ...
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+ NULL
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+*/
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+
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+ .text
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+ .globl _start
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+ .type _start,@function
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+_start:
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+ /* Clear the frame pointer. The ABI suggests this be done, to mark
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+ the outermost frame obviously. */
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+ xorq %rbp, %rbp
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+
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+ /* Extract the arguments as encoded on the stack and set up
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+ the arguments for __libc_start_main (int (*main) (int, char **, char **),
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+ int argc, char *argv,
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+ void (*init) (void), void (*fini) (void),
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+ void (*rtld_fini) (void), void *stack_end).
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+ The arguments are passed via registers and on the stack:
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+ main: %rdi
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+ argc: %rsi
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+ argv: %rdx
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+ init: %rcx
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+ fini: %r8
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+ rtld_fini: %r9
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+ stack_end: stack. */
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+
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+ movq %rdx, %r9 /* Address of the shared library termination
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+ function. */
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+ popq %rsi /* Pop the argument count. */
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+ movq %rsp, %rdx /* argv starts just at the current stack top. */
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+
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+ movq %rsi,U_SYSTEM_ARGC
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+ movq %rsp,U_SYSTEM_ARGV /* argv starts just at the current stack top. */
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+ leaq 8(,%rsi,8),%rax
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+ addq %rsp,%rax
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+ movq %rax,U_SYSTEM_ENVP
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+
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+ /* Align the stack to a 16 byte boundary to follow the ABI. */
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+ andq $~15, %rsp
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+
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+ pushq %rax /* Push garbage because we push 8 more bytes. */
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+
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+ /* Provide the highest stack address to the user code (for stacks
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+ which grow downwards). */
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+ pushq %rsp
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+
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+ /* Pass address of our own entry points to .fini and .init. */
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+ movq $_init_dummy, %r8
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+ movq $_fini_dummy, %rcx
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+
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+ movq $main_stub, %rdi
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+
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+ /* Call the user's main function, and exit with its value.
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+ But let the libc call main. */
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+ call __libc_start_main
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+
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+ hlt /* Crash if somehow `exit' does return. */
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+
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+/* fake main routine which will be run from libc */
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+main_stub:
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+ /* save return address */
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+ popq %rax
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+ movq %rax,___fpc_ret
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+ movq %rbp,___fpc_ret_rbp
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+ pushq %rax
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+
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+ /* start the program */
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+ xorq %rbp,%rbp
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+ call PASCALMAIN
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+ hlt
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+
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+ .globl _haltproc
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+ .type _haltproc,@function
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+_haltproc:
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+ movzwq U_SYSTEM_EXITCODE,%rax /* load and save exitcode */
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+
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+ movq ___fpc_ret,%rdx /* return to libc */
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+ movq ___fpc_ret_rbp,%rbp
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+ pushq %rdx
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+_init_dummy:
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+_fini_dummy:
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+ ret
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+
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+/* Define a symbol for the first piece of initialized data. */
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+ .data
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+ .globl __data_start
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+__data_start:
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+ .long 0
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+ .weak data_start
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+ data_start = __data_start
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+
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+ .globl ___fpc_brk_addr /* heap management */
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+ .type ___fpc_brk_addr,@object
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+ .size ___fpc_brk_addr,8
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+___fpc_brk_addr:
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+ .quad 0
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+
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+___fpc_ret: /* return address to libc */
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+ .quad 0
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+___fpc_ret_rbp:
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+ .quad 0
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+
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+/* We need this stuff to make gdb behave itself, otherwise
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+ gdb will chokes with SIGILL when trying to debug apps.
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+*/
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+ .section ".note.ABI-tag", "a"
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+ .align 4
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+ .long 1f - 0f
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+ .long 3f - 2f
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+ .long 1
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+0: .asciz "GNU"
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+1: .align 4
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+2: .long 0
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+ .long 2,4,0
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+3: .align 4
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+
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+ .section .note.GNU-stack,"",@progbits
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/*
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$Log$
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- Revision 1.1 2003-01-06 19:39:17 florian
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+ Revision 1.2 2004-02-20 23:48:27 peter
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+ * c stub implemented
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+
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+ Revision 1.1 2003/01/06 19:39:17 florian
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+ dummy implementations
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*/
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peter