- 此问题在此处已有答案**：
Why does this MOVSS instruction use RIP-relative addressing? [duplicate]（1个答案）
Why are global variables in x86-64 accessed relative to the instruction pointer?（2个答案）
How to load address of function or label into register（1个答案）
昨天关门了。
编译器在switch语句的开头（下面的代码片段部分）做了什么来获得% rax中的地址，以便将notrack jmpq *%rax定位到正确的偏移量？
常量0xe07和0xdfb是否填充？
lea 0xe07(%rip),%rax
lea 0xdfb(%rip),%rdx片段
10 [1] switch (c) {
0x5555555551ec <+ 35> 0f be 45 fc movsbl -0x4(%rbp),%eax
0x5555555551f0 <+ 39> 83 e8 2d sub $0x2d,%eax
0x5555555551f3 <+ 42> 83 f8 32 cmp $0x32,%eax
0x5555555551f6 <+ 45> 0f 87 18 01 00 00 ja 0x555555555314 <aa2i(char)+331>
0x5555555551fc <+ 51> 89 c0 mov %eax,%eax
0x5555555551fe <+ 53> 48 8d 14 85 00 00 00 00 lea 0x0(,%rax,4),%rdx
0x555555555206 <+ 61> 48 8d 05 07 0e 00 00 lea 0xe07(%rip),%rax # 0x555555556014
0x55555555520d <+ 68> 8b 04 02 mov (%rdx,%rax,1),%eax
0x555555555210 <+ 71> 48 98 cltq
0x555555555212 <+ 73> 48 8d 15 fb 0d 00 00 lea 0xdfb(%rip),%rdx # 0x555555556014
0x555555555219 <+ 80> 48 01 d0 add %rdx,%rax
0x55555555521c <+ 83> 3e ff e0 notrack jmpq *%raxcpp代码
#include <QCoreApplication>
const int ANY=20; //number representing an X (any amino acid) internally
const int GAP=21; //number representing a gap internally
char aa2i(char c) {
//A R N D C Q E G H I L K M F P S T W Y V
if (c >= 'a' && c <= 'z') c += 'A' - 'a';
switch (c) {
case 'A':
return 0;
case 'R':
return 1;
case 'N':
return 2;
case 'D':
return 3;
case 'C':
return 4;
case 'Q':
return 5;
case 'E':
return 6;
case 'G':
return 7;
case 'H':
return 8;
case 'I':
return 9;
case 'L':
return 10;
case 'K':
return 11;
case 'M':
return 12;
case 'F':
return 13;
case 'P':
return 14;
case 'S':
return 15;
case 'T':
return 16;
case 'W':
return 17;
case 'Y':
return 18;
case 'V':
return 19;
case 'X':
return ANY;
case 'J':
return ANY;
case 'O':
return ANY;
case 'U':
return 4; //Selenocystein -> Cystein
case 'B':
return 3; //D (or N)
case 'Z':
return 6; //E (or Q)
case '-':
return GAP;
case '.':
return GAP;
case '_':
return GAP;
}
if (c >= 0 && c <= 32) return -1; // white space and control characters
return -2;
}
int main(int argc, char *argv[])
{
aa2i('R');
}拆卸：
6 [1] char aa2i(char c) {
0x5555555551c9 f3 0f 1e fa endbr64
0x5555555551cd <+ 4> 55 push %rbp
0x5555555551ce <+ 5> 48 89 e5 mov %rsp,%rbp
0x5555555551d1 <+ 8> 89 f8 mov %edi,%eax
0x5555555551d3 <+ 10> 88 45 fc mov %al,-0x4(%rbp)
9 [1] if (c >= 'a' && c <= 'z') c += 'A' - 'a';
0x5555555551d6 <+ 13> 80 7d fc 60 cmpb $0x60,-0x4(%rbp)
0x5555555551da <+ 17> 7e 10 jle 0x5555555551ec <aa2i(char)+35>
0x5555555551dc <+ 19> 80 7d fc 7a cmpb $0x7a,-0x4(%rbp)
0x5555555551e0 <+ 23> 7f 0a jg 0x5555555551ec <aa2i(char)+35>
0x5555555551e2 <+ 25> 0f b6 45 fc movzbl -0x4(%rbp),%eax
0x5555555551e6 <+ 29> 83 e8 20 sub $0x20,%eax
0x5555555551e9 <+ 32> 88 45 fc mov %al,-0x4(%rbp)
10 [1] switch (c) {
0x5555555551ec <+ 35> 0f be 45 fc movsbl -0x4(%rbp),%eax
0x5555555551f0 <+ 39> 83 e8 2d sub $0x2d,%eax
0x5555555551f3 <+ 42> 83 f8 32 cmp $0x32,%eax
0x5555555551f6 <+ 45> 0f 87 18 01 00 00 ja 0x555555555314 <aa2i(char)+331>
0x5555555551fc <+ 51> 89 c0 mov %eax,%eax
0x5555555551fe <+ 53> 48 8d 14 85 00 00 00 00 lea 0x0(,%rax,4),%rdx
0x555555555206 <+ 61> 48 8d 05 07 0e 00 00 lea 0xe07(%rip),%rax # 0x555555556014
0x55555555520d <+ 68> 8b 04 02 mov (%rdx,%rax,1),%eax
0x555555555210 <+ 71> 48 98 cltq
0x555555555212 <+ 73> 48 8d 15 fb 0d 00 00 lea 0xdfb(%rip),%rdx # 0x555555556014
0x555555555219 <+ 80> 48 01 d0 add %rdx,%rax
0x55555555521c <+ 83> 3e ff e0 notrack jmpq *%rax
12 [1] return 0;
0x55555555521f <+ 86> b8 00 00 00 00 mov $0x0,%eax
0x555555555224 <+ 91> e9 03 01 00 00 jmpq 0x55555555532c <aa2i(char)+355>
14 [1] return 1;
0x555555555229 <+ 96> b8 01 00 00 00 mov $0x1,%eax
0x55555555522e <+ 101> e9 f9 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
16 [1] return 2;
0x555555555233 <+ 106> b8 02 00 00 00 mov $0x2,%eax
0x555555555238 <+ 111> e9 ef 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
18 [1] return 3;
0x55555555523d <+ 116> b8 03 00 00 00 mov $0x3,%eax
0x555555555242 <+ 121> e9 e5 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
20 [1] return 4;
0x555555555247 <+ 126> b8 04 00 00 00 mov $0x4,%eax
0x55555555524c <+ 131> e9 db 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
22 [1] return 5;
0x555555555251 <+ 136> b8 05 00 00 00 mov $0x5,%eax
0x555555555256 <+ 141> e9 d1 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
24 [1] return 6;
0x55555555525b <+ 146> b8 06 00 00 00 mov $0x6,%eax
0x555555555260 <+ 151> e9 c7 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
26 [1] return 7;
0x555555555265 <+ 156> b8 07 00 00 00 mov $0x7,%eax
0x55555555526a <+ 161> e9 bd 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
28 [1] return 8;
0x55555555526f <+ 166> b8 08 00 00 00 mov $0x8,%eax
0x555555555274 <+ 171> e9 b3 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
30 [1] return 9;
0x555555555279 <+ 176> b8 09 00 00 00 mov $0x9,%eax
0x55555555527e <+ 181> e9 a9 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
32 [1] return 10;
0x555555555283 <+ 186> b8 0a 00 00 00 mov $0xa,%eax
0x555555555288 <+ 191> e9 9f 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
34 [1] return 11;
0x55555555528d <+ 196> b8 0b 00 00 00 mov $0xb,%eax
0x555555555292 <+ 201> e9 95 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
36 [1] return 12;
0x555555555297 <+ 206> b8 0c 00 00 00 mov $0xc,%eax
0x55555555529c <+ 211> e9 8b 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
38 [1] return 13;
0x5555555552a1 <+ 216> b8 0d 00 00 00 mov $0xd,%eax
0x5555555552a6 <+ 221> e9 81 00 00 00 jmpq 0x55555555532c <aa2i(char)+355>
40 [1] return 14;
0x5555555552ab <+ 226> b8 0e 00 00 00 mov $0xe,%eax
0x5555555552b0 <+ 231> eb 7a jmp 0x55555555532c <aa2i(char)+355>
42 [1] return 15;
0x5555555552b2 <+ 233> b8 0f 00 00 00 mov $0xf,%eax
0x5555555552b7 <+ 238> eb 73 jmp 0x55555555532c <aa2i(char)+355>
44 [1] return 16;
0x5555555552b9 <+ 240> b8 10 00 00 00 mov $0x10,%eax
0x5555555552be <+ 245> eb 6c jmp 0x55555555532c <aa2i(char)+355>
46 [1] return 17;
0x5555555552c0 <+ 247> b8 11 00 00 00 mov $0x11,%eax
0x5555555552c5 <+ 252> eb 65 jmp 0x55555555532c <aa2i(char)+355>
48 [1] return 18;
0x5555555552c7 <+ 254> b8 12 00 00 00 mov $0x12,%eax
0x5555555552cc <+ 259> eb 5e jmp 0x55555555532c <aa2i(char)+355>
50 [1] return 19;
0x5555555552ce <+ 261> b8 13 00 00 00 mov $0x13,%eax
0x5555555552d3 <+ 266> eb 57 jmp 0x55555555532c <aa2i(char)+355>
52 [1] return ANY;
0x5555555552d5 <+ 268> b8 14 00 00 00 mov $0x14,%eax
0x5555555552da <+ 273> eb 50 jmp 0x55555555532c <aa2i(char)+355>
54 [1] return ANY;
0x5555555552dc <+ 275> b8 14 00 00 00 mov $0x14,%eax
0x5555555552e1 <+ 280> eb 49 jmp 0x55555555532c <aa2i(char)+355>
56 [1] return ANY;
0x5555555552e3 <+ 282> b8 14 00 00 00 mov $0x14,%eax
0x5555555552e8 <+ 287> eb 42 jmp 0x55555555532c <aa2i(char)+355>
58 [1] return 4; //Selenocystein -> Cystein
0x5555555552ea <+ 289> b8 04 00 00 00 mov $0x4,%eax
0x5555555552ef <+ 294> eb 3b jmp 0x55555555532c <aa2i(char)+355>
60 [1] return 3; //D (or N)
0x5555555552f1 <+ 296> b8 03 00 00 00 mov $0x3,%eax
0x5555555552f6 <+ 301> eb 34 jmp 0x55555555532c <aa2i(char)+355>
62 [1] return 6; //E (or Q)
0x5555555552f8 <+ 303> b8 06 00 00 00 mov $0x6,%eax
0x5555555552fd <+ 308> eb 2d jmp 0x55555555532c <aa2i(char)+355>
64 [1] return GAP;
0x5555555552ff <+ 310> b8 15 00 00 00 mov $0x15,%eax
0x555555555304 <+ 315> eb 26 jmp 0x55555555532c <aa2i(char)+355>
66 [1] return GAP;
0x555555555306 <+ 317> b8 15 00 00 00 mov $0x15,%eax
0x55555555530b <+ 322> eb 1f jmp 0x55555555532c <aa2i(char)+355>
68 [1] return GAP;
0x55555555530d <+ 324> b8 15 00 00 00 mov $0x15,%eax
0x555555555312 <+ 329> eb 18 jmp 0x55555555532c <aa2i(char)+355>
70 [1] if (c >= 0 && c <= 32) return -1; // white space and control characters
0x555555555314 <+ 331> 80 7d fc 00 cmpb $0x0,-0x4(%rbp)
0x555555555318 <+ 335> 78 0d js 0x555555555327 <aa2i(char)+350>
0x55555555531a <+ 337> 80 7d fc 20 cmpb $0x20,-0x4(%rbp)
0x55555555531e <+ 341> 7f 07 jg 0x555555555327 <aa2i(char)+350>
0x555555555320 <+ 343> b8 ff ff ff ff mov $0xffffffff,%eax
0x555555555325 <+ 348> eb 05 jmp 0x55555555532c <aa2i(char)+355>
71 [1] return -2;
0x555555555327 <+ 350> b8 fe ff ff ff mov $0xfffffffe,%eax
72 [1] }
0x55555555532c <+ 355> 5d pop %rbp
0x55555555532d <+ 356> c3 retq
1条答案
按热度按时间kdfy810k1#
这就是所谓的RIP相对寻址（详见英特尔第二卷www.example.com一2.2.1.6）。基本上就是将偏移量（
0xe07和0xdfb）加到下一条指令的地址上。这很可能是跳转表所在的位置，看起来就在函数代码之后。在第一种情况下，下一条指令的地址是
0x55555555520d+0xe07=0x555555556014，在第二种情况下，下一条指令的地址是0x555555555219+0xdfb=0x555555556014。