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1 /* stuff needed for libgcc on win32.
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2 *
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3 * Copyright (C) 1996, 1998, 2001, 2003, 2008, 2009 Free Software Foundation, Inc.
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4 * Written By Steve Chamberlain
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5 *
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6 * This file is free software; you can redistribute it and/or modify it
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7 * under the terms of the GNU General Public License as published by the
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8 * Free Software Foundation; either version 3, or (at your option) any
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9 * later version.
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10 *
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11 * This file is distributed in the hope that it will be useful, but
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12 * WITHOUT ANY WARRANTY; without even the implied warranty of
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13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 * General Public License for more details.
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15 *
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16 * Under Section 7 of GPL version 3, you are granted additional
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17 * permissions described in the GCC Runtime Library Exception, version
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18 * 3.1, as published by the Free Software Foundation.
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19 *
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20 * You should have received a copy of the GNU General Public License and
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21 * a copy of the GCC Runtime Library Exception along with this program;
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22 * see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 * <http://www.gnu.org/licenses/>.
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24 */
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25
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26 #ifdef L_chkstk
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27
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28 /* Function prologue calls _alloca to probe the stack when allocating more
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29 than CHECK_STACK_LIMIT bytes in one go. Touching the stack at 4K
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30 increments is necessary to ensure that the guard pages used
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31 by the OS virtual memory manger are allocated in correct sequence. */
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32
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33 .global ___chkstk
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34 .global __alloca
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35 #ifndef _WIN64
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36 ___chkstk:
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37 __alloca:
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38 pushl %ecx /* save temp */
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39 leal 8(%esp), %ecx /* point past return addr */
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40 cmpl $0x1000, %eax /* > 4k ?*/
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41 jb Ldone
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42
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43 Lprobe:
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44 subl $0x1000, %ecx /* yes, move pointer down 4k*/
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45 orl $0x0, (%ecx) /* probe there */
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46 subl $0x1000, %eax /* decrement count */
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47 cmpl $0x1000, %eax
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48 ja Lprobe /* and do it again */
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49
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50 Ldone:
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51 subl %eax, %ecx
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52 orl $0x0, (%ecx) /* less than 4k, just peek here */
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53
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54 movl %esp, %eax /* save old stack pointer */
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55 movl %ecx, %esp /* decrement stack */
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56 movl (%eax), %ecx /* recover saved temp */
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57 movl 4(%eax), %eax /* recover return address */
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58
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59 /* Push the return value back. Doing this instead of just
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60 jumping to %eax preserves the cached call-return stack
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61 used by most modern processors. */
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62 pushl %eax
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63 ret
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64 #else
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65 /* __alloca is a normal function call, which uses %rcx as the argument. And stack space
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66 for the argument is saved. */
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67 __alloca:
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68 movq %rcx, %rax
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69 addq $0x7, %rax
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70 andq $0xfffffffffffffff8, %rax
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71 popq %rcx /* pop return address */
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72 popq %r10 /* Pop the reserved stack space. */
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73 movq %rsp, %r10 /* get sp */
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74 cmpq $0x1000, %rax /* > 4k ?*/
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75 jb Ldone_alloca
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76
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77 Lprobe_alloca:
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78 subq $0x1000, %r10 /* yes, move pointer down 4k*/
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79 orq $0x0, (%r10) /* probe there */
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80 subq $0x1000, %rax /* decrement count */
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81 cmpq $0x1000, %rax
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82 ja Lprobe_alloca /* and do it again */
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83
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84 Ldone_alloca:
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85 subq %rax, %r10
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86 orq $0x0, (%r10) /* less than 4k, just peek here */
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87 movq %r10, %rax
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88 subq $0x8, %r10 /* Reserve argument stack space. */
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89 movq %r10, %rsp /* decrement stack */
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90
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91 /* Push the return value back. Doing this instead of just
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92 jumping to %rcx preserves the cached call-return stack
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93 used by most modern processors. */
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94 pushq %rcx
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95 ret
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96
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97 /* ___chkstk is a *special* function call, which uses %rax as the argument.
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98 We avoid clobbering the 4 integer argument registers, %rcx, %rdx,
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99 %r8 and %r9, which leaves us with %rax, %r10, and %r11 to use. */
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100 ___chkstk:
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101 addq $0x7, %rax /* Make sure stack is on alignment of 8. */
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102 andq $0xfffffffffffffff8, %rax
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103 popq %r11 /* pop return address */
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104 movq %rsp, %r10 /* get sp */
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105 cmpq $0x1000, %rax /* > 4k ?*/
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106 jb Ldone
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107
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108 Lprobe:
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109 subq $0x1000, %r10 /* yes, move pointer down 4k*/
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110 orl $0x0, (%r10) /* probe there */
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111 subq $0x1000, %rax /* decrement count */
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112 cmpq $0x1000, %rax
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113 ja Lprobe /* and do it again */
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114
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115 Ldone:
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116 subq %rax, %r10
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117 orl $0x0, (%r10) /* less than 4k, just peek here */
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118 movq %r10, %rsp /* decrement stack */
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119
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120 /* Push the return value back. Doing this instead of just
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121 jumping to %r11 preserves the cached call-return stack
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122 used by most modern processors. */
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123 pushq %r11
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124 ret
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125 #endif
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126 #endif
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