如何使用gdb讀取所有寄存器的值？

Question

我正在調試程序集以瞭解gcc編譯器如何工作。我想讀取我的$ fs段寄存器，所以我使用x/x $ fs，但它告訴我它不能訪問內存。如何在i386：86_64上讀取任何包含段，通用和控制寄存器的寄存器？

Answer 1

info registers打印出寄存器中的值對我來說這是你問我在想什麼：

(gdb) info registers 
rax   0x7ffff7731ec8 140737344904904 
rbx   0x0 0 
rcx   0x0 0 
rdx   0x7fffffffd618 140737488344600 
rsi   0x7fffffffd608 140737488344584 
rdi   0x1 1 
rbp   0x0 0x0 
rsp   0x7fffffffd528 0x7fffffffd528 
r8    0x7ffff7730300 140737344897792 
r9    0x7ffff7dec250 140737351959120 
r10   0x7fffffffd390 140737488343952 
r11   0x7ffff73d0b50 140737341360976 
r12   0x400be0 4197344 
r13   0x7fffffffd600 140737488344576 
r14   0x0 0 
r15   0x0 0 
rip   0x402330 0x402330 <main> 
eflags   0x246 [ PF ZF IF ] 
cs    0x33 51 
ss    0x2b 43 
ds    0x0 0 
es    0x0 0 
fs    0x0 0 
gs    0x0 0 
(gdb) 

Answer 2

您必須使用p和set命令讀取/設置寄存器。每臺機器的寄存器名稱不同;使用信息寄存器來查看您的機器上使用的名稱。有關示例，請參閱GDB手冊的registers部分以獲取詳細信息。

要打印$fs寄存器的值，你可以這樣做：

(gdb) p/x $fs 
$1 = 0x0 

什麼x命令不被檢查的存儲器中。但是，有些情況下，你不能這樣做。例如，如果地址指向的內存受到保護。所以，如果你嘗試檢查，在一個虛擬地址0x0內存，GDB顯然拒絕的話，例如：

(gdb) x/x $fs 
0x0: Cannot access memory at address 0x0 

希望它能幫助。祝你好運！

Answer 3

info all-registers 

給你所有的寄存器值，包括FPU寄存器堆棧，XMM寄存器。

(gdb) i all-r 
rax   0x2aaaaace62ce 46912498459342 
rbx   0x2aab18e71290 46914345570960 
rcx   0x2aaab2020d60 46912619285856 
rdx   0xffffffffffd934ee  -2542354 
rsi   0x2aab18ec7a40 46914345925184 
rdi   0xa  10 
rbp   0x2aab18e6f000 0x2aab18e6f000 
rsp   0x2aab18e6f000 0x2aab18e6f000 
r8    0xe  14 
r9    0x2aab18eb1f08 46914345836296 
r10   0x2aaab9085000 46912737136640 
r11   0x0  0 
r12   0x2aab18ec7170 46914345922928 
r13   0x477f3280  1199518336 
r14   0x7  7 
r15   0x2aaada787000 46913298132992 
rip   0x2aaaaae3b18e 0x2aaaaae3b18e <flt_fadd+4> 
eflags   0x283 643 
ds    0x0  0 
es    0x0  0 
fs    0x0  0 
gs    0x0  0 
st0   10  (raw 0x4002a000000000000000) 
st1   3  (raw 0x4000c000000000000000) 
st2   0  (raw 0x00000000000000000000) 
st3   0  (raw 0x00000000000000000000) 
st4   0  (raw 0x00000000000000000000) 
st5   0  (raw 0x00000000000000000000) 
st6   0  (raw 0x00000000000000000000) 
st7   0  (raw 0x00000000000000000000) 
fctrl   0x137f 4991 
fstat   0x7000 28672 
ftag   0xc0  192 
fiseg   0xaae3afe5  -1427918875 
fioff   0x2aaa 10922 
foseg   0x18e6ee48  417787464 
fooff   0x2aab 10923 
fop   0x704 1796 
xmm0   {f = {0x0, 0x6, 0x0, 0x0}}  {f = {0, 6.48876953, 0, 0}} 
xmm1   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm2   {f = {0x0, 0x1c0, 0x0, 0x0}}  {f = {0, 448, 0, 0}} 
xmm3   {f = {0x0, 0x1, 0x0, 0x0}}  {f = {0, 1.75, 0, 0}} 
xmm4   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm5   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm6   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm7   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm8   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm9   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm10   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm11   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm12   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm13   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm14   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
xmm15   {f = {0x0, 0x0, 0x0, 0x0}}  {f = {0, 0, 0, 0}} 
mxcsr   0x1fa0 8096