我正在修改一些汇编代码来执行printf。第一次调用printf时，它工作得很好。但是第二次，对printf的调用感到很糟糕。我正在使用gdb进行调试。
原始部分代码是
movq 192(%rsp), %rax # 8-byte Reload
movq (%rax), %rcx
movq 200(%rsp), %rdx # 8-byte Reload
movq (%rdx), %rsi
movq %rcx, %rdi
movq 24(%rsp), %r8 # 8-byte Reload
addq %r8, %rdi
movq $0, (%rsi)
movq 216(%rsp), %r9 # 8-byte Reload
movq (%r9), %r10
movq 208(%rsp), %r11 # 8-byte Reload
movq (%r11,%rdi,8), %rbx
修改后的代码是
movq 192(%rsp), %rax # 8-byte Reload
movq (%rax), %rcx
movq 200(%rsp), %rdx # 8-byte Reload
movq (%rdx), %rsi
movq %rcx, %rdi
movq 24(%rsp), %r8 # 8-byte Reload
addq %r8, %rdi
pushq %rax
pushq %rsi
pushq %rdi
movq %rsi, %rax
movl $.LCdddd, %edi
movl $0, %eax
call printf
popq %rdi
popq %rsi
popq %rax
movq $0, (%rsi)
movq 216(%rsp), %r9 # 8-byte Reload
movq (%r9), %r10
movq 208(%rsp), %r11 # 8-byte Reload
movq (%r11,%rdi,8), %rbx
当我在gdb中遇到Ctrl + C时，它会显示在
__lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:93
感谢任何帮助。
编辑：gdb跟踪如下。在最后一行之后，它只是等待
196 movq %rsi, %rax
(gdb)
197 movl $.LCdddd, %edi
(gdb)
198 movl $0, %eax
(gdb)
199 call printf
(gdb)
__printf (format=0x40969e "\nmeow %p\n") at printf.c:30
30 printf.c: No such file or directory.
(gdb) s
34 in printf.c
(gdb) s
30 in printf.c
(gdb) s
35 in printf.c
(gdb) s
34 in printf.c
(gdb)
35 in printf.c
(gdb)
_IO_vfprintf_internal (s=0x7ffff7ba8280 <_IO_2_1_stdout_>, format=0x40969e "\nmeow %p\n", ap=0x7fffffffdfc0) at vfprintf.c:246
246 vfprintf.c: No such file or directory.
(gdb)
211 in vfprintf.c
(gdb)
246 in vfprintf.c
(gdb)
1298 in vfprintf.c
(gdb)
1302 in vfprintf.c
(gdb)
1313 in vfprintf.c
(gdb)
1324 in vfprintf.c
(gdb)
1335 in vfprintf.c
(gdb)
__find_specmb (format=<optimized out>) at printf-parse.h:99
99 printf-parse.h: No such file or directory.
(gdb)
_IO_vfprintf_internal (s=0x7ffff7ba8280 <_IO_2_1_stdout_>, format=0x40969e "\nmeow %p\n", ap=0x7fffffffdfc0) at vfprintf.c:1324
1324 vfprintf.c: No such file or directory.
(gdb)
1335 in vfprintf.c
(gdb)
__find_specmb (format=0x40969e "\nmeow %p\n") at printf-parse.h:99
99 printf-parse.h: No such file or directory.
(gdb)
strchrnul () at ../sysdeps/x86_64/strchrnul.S:27
27 ../sysdeps/x86_64/strchrnul.S: No such file or directory.
(gdb)
28 in ../sysdeps/x86_64/strchrnul.S
(gdb)
29 in ../sysdeps/x86_64/strchrnul.S
(gdb)
30 in ../sysdeps/x86_64/strchrnul.S
(gdb)
31 in ../sysdeps/x86_64/strchrnul.S
(gdb)
32 in ../sysdeps/x86_64/strchrnul.S
(gdb)
33 in ../sysdeps/x86_64/strchrnul.S
(gdb)
34 in ../sysdeps/x86_64/strchrnul.S
(gdb)
35 in ../sysdeps/x86_64/strchrnul.S
(gdb)
36 in ../sysdeps/x86_64/strchrnul.S
(gdb)
37 in ../sysdeps/x86_64/strchrnul.S
(gdb)
38 in ../sysdeps/x86_64/strchrnul.S
(gdb)
39 in ../sysdeps/x86_64/strchrnul.S
(gdb)
40 in ../sysdeps/x86_64/strchrnul.S
(gdb)
41 in ../sysdeps/x86_64/strchrnul.S
(gdb)
42 in ../sysdeps/x86_64/strchrnul.S
(gdb)
43 in ../sysdeps/x86_64/strchrnul.S
(gdb)
44 in ../sysdeps/x86_64/strchrnul.S
(gdb)
45 in ../sysdeps/x86_64/strchrnul.S
(gdb)
46 in ../sysdeps/x86_64/strchrnul.S
(gdb)
48 in ../sysdeps/x86_64/strchrnul.S
(gdb)
49 in ../sysdeps/x86_64/strchrnul.S
(gdb)
50 in ../sysdeps/x86_64/strchrnul.S
(gdb)
51 in ../sysdeps/x86_64/strchrnul.S
(gdb)
52 in ../sysdeps/x86_64/strchrnul.S
(gdb)
53 in ../sysdeps/x86_64/strchrnul.S
(gdb)
54 in ../sysdeps/x86_64/strchrnul.S
(gdb)
55 in ../sysdeps/x86_64/strchrnul.S
(gdb)
56 in ../sysdeps/x86_64/strchrnul.S
(gdb)
58 in ../sysdeps/x86_64/strchrnul.S
(gdb)
59 in ../sysdeps/x86_64/strchrnul.S
(gdb)
strchrnul () at ../sysdeps/x86_64/strchrnul.S:60
60 in ../sysdeps/x86_64/strchrnul.S
(gdb)
_IO_vfprintf_internal (s=0x7ffff7ba8280 <_IO_2_1_stdout_>, format=0x40969e "\nmeow %p\n", ap=0x7fffffffdfc0) at vfprintf.c:1339
1339 vfprintf.c: No such file or directory.
(gdb)
1335 in vfprintf.c
(gdb)
__find_specmb (format=0x40969e "\nmeow %p\n") at printf-parse.h:99
99 printf-parse.h: No such file or directory.
(gdb)
_IO_vfprintf_internal (s=0x7ffff7ba8280 <_IO_2_1_stdout_>, format=0x40969e "\nmeow %p\n", ap=0x7fffffffdfc0) at vfprintf.c:1339
1339 vfprintf.c: No such file or directory.
(gdb)
_pthread_cleanup_push_defer (buffer=0x7fffffffde78, routine=0x7ffff784cf70 <__funlockfile>, arg=0x7ffff7ba8280 <_IO_2_1_stdout_>) at cleanup_defer_compat.c:31
31 cleanup_defer_compat.c: No such file or directory.
(gdb)
32 in cleanup_defer_compat.c
(gdb)
33 in cleanup_defer_compat.c
(gdb)
35 in cleanup_defer_compat.c
(gdb)
38 in cleanup_defer_compat.c
(gdb)
55 in cleanup_defer_compat.c
(gdb)
57 in cleanup_defer_compat.c
(gdb)
58 in cleanup_defer_compat.c
(gdb)
_IO_vfprintf_internal (s=0x7ffff7ba8280 <_IO_2_1_stdout_>, format=0x40969e "\nmeow %p\n", ap=0x7fffffffdfc0) at vfprintf.c:1340
1340 vfprintf.c: No such file or directory.
(gdb)
0x00007ffff783d325 in _L_lock_927 () from /lib/x86_64-linux-gnu/libc.so.6
(gdb)
Single stepping until exit from function _L_lock_927,
which has no line number information.
__lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:77
77 ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S: No such file or directory.
(gdb)
79 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
(gdb)
83 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
(gdb)
84 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
(gdb)
85 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
(gdb)
87 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
(gdb)
88 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
(gdb)
93 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
(gdb)
94 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
(gdb)
96 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
(gdb)
97 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
(gdb)
90 in ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S
答案 0 :(得分：1)
AFAIK，printf有CCALL调用约定。因此，在printf返回后，您可能必须从堆栈中手动删除推送的参数。
答案 1 :(得分：1)
我认为你错过了堆栈保护。请尝试使用__printf_chk，同时保存框架并将其恢复，例如：
pushq %rbp
movq %rsp, %rbp
pushq %rax
pushq %rdx
pushq %rsi
pushq %rdi
xorl %edx, %edx
movl $.LCdddd, %esi
movl $1, %edi
xorl %eax, %eax
call __printf_chk
popq %rdi
popq %rsi
popq %rdx
popq %rax
leave
__ printf_chk是非标准的，但必须在libc中。 Vararg函数有时很棘手。使用选中的printf，您至少会收到警告。
movl $1, %edi
是标记值（请参阅something like specification），因此您可以尝试传递2或更高版本。由于这是非标准功能，很难说你会在系统上看到什么。