How to run assembly in gdb directly?

I can use `call` to run c functions ,but how to run assembly or even shell code directly?

I don't think gdb includes an assembler, so I wouldn't expect to be able to enter assembly directly.

You can use the <code>[shell][1]</code> gdb command to run shell commands:

(gdb) shell uname -m
x86_64



[1]:

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To execute shell code, you can edit a function's contents directly:

(gdb) b foo
Breakpoint 1 at 0x400608
(gdb) run
Breakpoint 1, 0x0000000000400608 in foo ()
(gdb) x/16bx foo
0x400604 <foo>: 0x55 0x48 0x89 0xe5 0x53 0x48 0x81 0xec
(gdb) set ((unsigned char *)foo)[6] = 0x85
(gdb) x/16bx foo
0x400604 <foo>: 0x55 0x48 0x89 0xe5 0x53 0x48 0x85 0xec
(gdb) cont

I don't know how to execute opcodes from within `gdb`, but you can certainly do whatever you want with registers. For instance, instead of `mov %rbx, %rax` you can use `set $rax = $rbx`:

(gdb) p $rax
$1 = 3671197290184
(gdb) set $rax = $rbx
(gdb) p $rax
$2 = 0
(gdb)