1/* stuff needed for libgcc on win32. 2 * 3 * Copyright (C) 1996-2022 Free Software Foundation, Inc. 4 * Written By Steve Chamberlain 5 * 6 * This file is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License as published by the 8 * Free Software Foundation; either version 3, or (at your option) any 9 * later version. 10 * 11 * This file is distributed in the hope that it will be useful, but 12 * WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 * General Public License for more details. 15 * 16 * Under Section 7 of GPL version 3, you are granted additional 17 * permissions described in the GCC Runtime Library Exception, version 18 * 3.1, as published by the Free Software Foundation. 19 * 20 * You should have received a copy of the GNU General Public License and 21 * a copy of the GCC Runtime Library Exception along with this program; 22 * see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 * <http://www.gnu.org/licenses/>. 24 */ 25 26#include "i386-asm.h" 27 28#ifdef HAVE_AS_CFI_SECTIONS 29 .cfi_sections .debug_frame 30#endif 31 32#ifdef L_chkstk 33/* Function prologue calls __chkstk to probe the stack when allocating more 34 than CHECK_STACK_LIMIT bytes in one go. Touching the stack at 4K 35 increments is necessary to ensure that the guard pages used 36 by the OS virtual memory manger are allocated in correct sequence. */ 37 38 .global ___chkstk 39 .global __alloca 40#ifdef __x86_64__ 41/* __alloca is a normal function call, which uses %rcx as the argument. */ 42 cfi_startproc() 43__alloca: 44 movq %rcx, %rax 45 /* FALLTHRU */ 46 47/* ___chkstk is a *special* function call, which uses %rax as the argument. 48 We avoid clobbering the 4 integer argument registers, %rcx, %rdx, 49 %r8 and %r9, which leaves us with %rax, %r10, and %r11 to use. */ 50 .align 4 51___chkstk: 52 popq %r11 /* pop return address */ 53 cfi_adjust_cfa_offset(-8) /* indicate return address in r11 */ 54 cfi_register(%rip, %r11) 55 movq %rsp, %r10 56 cmpq $0x1000, %rax /* > 4k ?*/ 57 jb 2f 58 591: subq $0x1000, %r10 /* yes, move pointer down 4k*/ 60 orl $0x0, (%r10) /* probe there */ 61 subq $0x1000, %rax /* decrement count */ 62 cmpq $0x1000, %rax 63 ja 1b /* and do it again */ 64 652: subq %rax, %r10 66 movq %rsp, %rax /* hold CFA until return */ 67 cfi_def_cfa_register(%rax) 68 orl $0x0, (%r10) /* less than 4k, just peek here */ 69 movq %r10, %rsp /* decrement stack */ 70 71 /* Push the return value back. Doing this instead of just 72 jumping to %r11 preserves the cached call-return stack 73 used by most modern processors. */ 74 pushq %r11 75 ret 76 cfi_endproc() 77#else 78 cfi_startproc() 79___chkstk: 80__alloca: 81 pushl %ecx /* save temp */ 82 cfi_push(%eax) 83 leal 8(%esp), %ecx /* point past return addr */ 84 cmpl $0x1000, %eax /* > 4k ?*/ 85 jb 2f 86 871: subl $0x1000, %ecx /* yes, move pointer down 4k*/ 88 orl $0x0, (%ecx) /* probe there */ 89 subl $0x1000, %eax /* decrement count */ 90 cmpl $0x1000, %eax 91 ja 1b /* and do it again */ 92 932: subl %eax, %ecx 94 orl $0x0, (%ecx) /* less than 4k, just peek here */ 95 movl %esp, %eax /* save current stack pointer */ 96 cfi_def_cfa_register(%eax) 97 movl %ecx, %esp /* decrement stack */ 98 movl (%eax), %ecx /* recover saved temp */ 99 100 /* Copy the return register. Doing this instead of just jumping to 101 the address preserves the cached call-return stack used by most 102 modern processors. */ 103 pushl 4(%eax) 104 ret 105 cfi_endproc() 106#endif /* __x86_64__ */ 107#endif /* L_chkstk */ 108 109#ifdef L_chkstk_ms 110/* ___chkstk_ms is a *special* function call, which uses %rax as the argument. 111 We avoid clobbering any registers. Unlike ___chkstk, it just probes the 112 stack and does no stack allocation. */ 113 .global ___chkstk_ms 114#ifdef __x86_64__ 115 cfi_startproc() 116___chkstk_ms: 117 pushq %rcx /* save temps */ 118 cfi_push(%rcx) 119 pushq %rax 120 cfi_push(%rax) 121 cmpq $0x1000, %rax /* > 4k ?*/ 122 leaq 24(%rsp), %rcx /* point past return addr */ 123 jb 2f 124 1251: subq $0x1000, %rcx /* yes, move pointer down 4k */ 126 orq $0x0, (%rcx) /* probe there */ 127 subq $0x1000, %rax /* decrement count */ 128 cmpq $0x1000, %rax 129 ja 1b /* and do it again */ 130 1312: subq %rax, %rcx 132 orq $0x0, (%rcx) /* less than 4k, just peek here */ 133 134 popq %rax 135 cfi_pop(%rax) 136 popq %rcx 137 cfi_pop(%rcx) 138 ret 139 cfi_endproc() 140#else 141 cfi_startproc() 142___chkstk_ms: 143 pushl %ecx /* save temp */ 144 cfi_push(%ecx) 145 pushl %eax 146 cfi_push(%eax) 147 cmpl $0x1000, %eax /* > 4k ?*/ 148 leal 12(%esp), %ecx /* point past return addr */ 149 jb 2f 150 1511: subl $0x1000, %ecx /* yes, move pointer down 4k*/ 152 orl $0x0, (%ecx) /* probe there */ 153 subl $0x1000, %eax /* decrement count */ 154 cmpl $0x1000, %eax 155 ja 1b /* and do it again */ 156 1572: subl %eax, %ecx 158 orl $0x0, (%ecx) /* less than 4k, just peek here */ 159 160 popl %eax 161 cfi_pop(%eax) 162 popl %ecx 163 cfi_pop(%ecx) 164 ret 165 cfi_endproc() 166#endif /* __x86_64__ */ 167#endif /* L_chkstk_ms */ 168