1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
; $Id: ASMBitFirstSet.asm $
;; @file
; IPRT - ASMBitFirstSet().
;
;
; Copyright (C) 2006-2022 Oracle and/or its affiliates.
;
; This file is part of VirtualBox base platform packages, as
; available from https://www.virtualbox.org.
;
; This program is free software; you can redistribute it and/or
; modify it under the terms of the GNU General Public License
; as published by the Free Software Foundation, in version 3 of the
; License.
;
; This program is distributed in the hope that it will be useful, but
; WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
; General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, see <https://www.gnu.org/licenses>.
;
; The contents of this file may alternatively be used under the terms
; of the Common Development and Distribution License Version 1.0
; (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
; in the VirtualBox distribution, in which case the provisions of the
; CDDL are applicable instead of those of the GPL.
;
; You may elect to license modified versions of this file under the
; terms and conditions of either the GPL or the CDDL or both.
;
; SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
;
;*******************************************************************************
;* Header Files *
;*******************************************************************************
%include "iprt/asmdefs.mac"
BEGINCODE
;;
; Finds the first set bit in a bitmap.
;
; @returns (32/64:eax, 16:ax+dx) Index of the first zero bit.
; @returns (32/64:eax, 16:ax+dx) -1 if no set bit was found.
; @param msc:rcx gcc:rdi pvBitmap Pointer to the bitmap.
; @param msc:edx gcc:rsi cBits The number of bits in the bitmap. Multiple of 32.
;
RT_BEGINPROC ASMBitFirstSet
;
; if (cBits)
; Put cBits in ecx first.
;
%if ARCH_BITS == 64
%ifdef ASM_CALL64_GCC
mov ecx, esi
%else
xchg rcx, rdx ; rdx=pvDst, ecx=cBits
%endif
%elif ARCH_BITS == 32
mov ecx, [esp + 4 + 4]
%elif ARCH_BITS == 16
push bp
mov bp, sp
mov ecx, [bp + 4 + 4]
%endif
or ecx, ecx
jz short .failed
;{
push xDI
; asm {...}
%if ARCH_BITS == 64
%ifdef ASM_CALL64_GCC
; rdi = start of scasd - already done
%else
mov rdi, rdx ; rdi = start of scasd (Note! xchg rdx,rcx above)
%endif
%elif ARCH_BITS == 32
mov edi, [esp + 4]
%elif ARCH_BITS == 16
mov ax, [bp + 4 + 2]
mov di, [bp + 4]
mov es, ax ; es is volatile, no need to save.
%endif
add ecx, 31 ; 32 bit aligned
shr ecx, 5 ; number of dwords to scan.
mov xDX, xDI ; xDX = saved pvBitmap
xor eax, eax
repe scasd ; Scan for the first dword with any bit set.
je .failed_restore
; find the bit in question
sub xDI, 4 ; one step back.
%if ARCH_BITS == 16
movzx edi, di
mov eax, [es:xDI]
%else
mov eax, [xDI]
%endif
sub xDI, xDX
shl edi, 3 ; calc bit offset.
bsf ecx, eax
jz .failed_restore ; race paranoia
add ecx, edi
mov eax, ecx
; return success
pop xDI
%if ARCH_BITS == 16
mov edx, eax
shr edx, 16
leave
%endif
ret
; failure
;}
;return -1;
.failed_restore:
pop xDI
.failed:
%if ARCH_BITS != 16
mov eax, 0ffffffffh
%else
mov ax, 0ffffh
mov dx, ax
leave
%endif
ret
ENDPROC ASMBitFirstSet
|
