2020-06-16 13:38:43 +00:00
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/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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2020-06-15 14:18:57 +00:00
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│vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/macros.h"
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#include "libc/dce.h"
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#include "libc/notice.inc"
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#define INITIAL_CAPACITY 4
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/ Invokes deferred function calls.
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/
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/ This offers behavior similar to std::unique_ptr. Functions
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/ overwrite their return addresses jumping here, and pushing
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/ exactly one entry on the shadow stack below. Functions may
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/ repeat that process multiple times, in which case the body
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/ of this gadget loops and unwinds as a natural consequence.
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/
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/ @param rax,rdx,xmm0,xmm1,st0,st1 is return value
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/ @see test/libc/runtime/gc_test.c
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/ <LIMBO>
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__gc: decq __garbage(%rip)
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mov __garbage(%rip),%r8
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mov __garbage+16(%rip),%r9
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js 9f
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shl $5,%r8
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lea (%r9,%r8),%r8
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mov 8(%r8),%r9
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mov 16(%r8),%rdi
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push 24(%r8)
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/ </LIMBO>
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push %rbp
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mov %rsp,%rbp
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sub $0x40,%rsp
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push %rax
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push %rdx
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fstpl -0x40(%rbp)
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fstpl -0x30(%rbp)
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movaps %xmm0,-0x20(%rbp)
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movaps %xmm1,-0x10(%rbp)
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call *%r9
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movaps -0x10(%rbp),%xmm1
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movaps -0x20(%rbp),%xmm0
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fldl -0x30(%rbp)
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fldl -0x40(%rbp)
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pop %rdx
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pop %rax
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leave
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ret
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9: call abort
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.endfn __gc,globl,hidden
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.bss
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.align 8
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__garbage:
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.quad 0 # garbage.i
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.quad 0 # garbage.n
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.quad 0 # garbage.p
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.rept INITIAL_CAPACITY
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.quad 0 # garbage.p[𝑖].frame
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.quad 0 # garbage.p[𝑖].fn
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.quad 0 # garbage.p[𝑖].arg
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.quad 0 # garbage.p[𝑖].ret
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.endr
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.endobj __garbage,globl,hidden
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.previous
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.init.start 100,_init_garbage
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push %rdi
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ezlea __garbage+8,di
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pushpop INITIAL_CAPACITY,%rax
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stosq
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lea 8(%rdi),%rax
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stosq
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pop %rdi
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.init.end 100,_init_garbage
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2020-06-16 02:01:28 +00:00
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.source __FILE__
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