AArch64 - wa write assembly instruction gives wrong results
#14052
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because in the r2 prompt, the # is considered a comment, so just do 'wa add x0, x1, 3'
about the neg and sub, feel free to submit a PR fixing them, otherwise just wait until someone have 5 spare free minutes to implement that
you can also install the keystone assembler plugin for r2
… On 13 May 2019, at 18:38, MatejKastak ***@***.***> wrote:
Work environment
Questions Answers
OS/arch/bits (mandatory) Linux kali 4.14.71-v8 #1 <#1> SMP PREEMPT Wed Oct 31 21:41:06 UTC 2018 aarch64 GNU/Linux
File format of the file you reverse (mandatory) ELF
Architecture/bits of the file (mandatory) ARMv8-A AArch64
r2 -v full output, not truncated (mandatory) radare2 3.6.0-git 21712 @ linux-arm-64 git.3.5.0-9-g34f2f9f25 commit: 34f2f9f <34f2f9f> build: 2019-05-13__16:01:05
Expected behavior
I was using the wa ( wa write opcode, separated by ';' (use '"' around the command) command to write a instruction to binary that I am debugging. It seems like the assembler is giving the wrong results.
Write the instruction wa add x0, x1, #3
Step the debugger ds
The written instruction should be add x0, x1, #3 (but its add x0, x1, #0)
Print the registers drj and see x0 == 5 (given everything is zero)
I tried this also on x86 and it seems to work.
Actual behavior
For example:
wa add x0, x1, #3 -> "add x0, x1, #0"
wa neg x0, x1 -> Cannot assemble 'neg x0, x1' at line 3
wa sub x0, xzr, x1 -> "sub x0, x0, x1"
Steps to reproduce the behavior
***@***.***:[insrunner]# r2 -d source
Process with PID 18235 started...
= attach 18235 18235
bin.baddr 0x00400000
Using 0x400000
asm.bits 64
-- (gdb) ^D
[0x00400078]> dr pc = main
0x00400078 ->0x00400078
[0x00400078]> s main
[0x00400078]> wa add x0, x1, #3
Written 4 byte(s) (add x0, x1, #3) = wx 20000091
[0x00400078]> pd 1 @ pc
;-- main:
;-- entry0:
;-- section..text:
;-- .text:
;-- $d:
;-- __start:
;-- _start:
;-- pc:
0x00400078 20000091 add x0, x1, 0 ; [01] -r-x section size 512 named .text
[0x00400078]> ds
[0x00400078]> drj
{"x0":0,"x1":0,"x2":0,"x3":0,"x4":0,"x5":0,"x6":0,"x7":0,"x8":0,"x9":0,"x10":0,"x11":0,"x12":0,"x13":0,"x14":0,"x15":0,"x16":0,"x17":0,"x18":0,"x19":0,"x20":0,"x21":0,"x22":0,"x23":0,"x24":0,"x25":0,"x26":0,"x27":0,"x28":0,"x29":0,"x30":0,"sp":549076061536,"pc":4194428,"d0":0,"d1":0,"d2":0,"d3":0,"d4":0,"d5":0,"d6":0,"d7":0,"d8":0,"d9":0,"d10":0,"d11":0,"d12":0,"d13":0,"d14":0,"d15":0,"d16":0,"d17":0,"d18":0,"d19":0,"d20":0,"d21":0,"d22":0,"d23":0,"d24":0,"d25":0,"d26":0,"d27":0,"d28":0,"d29":0,"d30":0,"dsp":549076061536,"pstate":2097152,"fstate":2097152}
[0x00400078]>
or
***@***.***:[insrunner]# r2 source
-- What do you want to debug today?
[0x00400078]> ood
Process with PID 18256 started...
File dbg:///root/dev/insrunner/source reopened in read-write mode
= attach 18256 18256
ptrace (PT_ATTACH): Operation not permitted
18256
[0x00400078]> dr pc = main
0x00400078 ->0x00400078
[0x00400078]> s main
[0x00400078]> wa neg x0, x1
Cannot assemble 'neg x0, x1' at line 3
[0x00400078]> wa sub x0, xzr, x1
Written 4 byte(s) (sub x0, xzr, x1) = wx 000001cb
[0x00400078]> pd 1 @ pc
;-- main:
;-- entry0:
;-- section..text:
;-- .text:
;-- $d:
;-- __start:
;-- _start:
;-- pc:
0x00400078 000001cb sub x0, x0, x1 ; [01] -r-x section size 512 named .text
[0x00400078]> ds
[0x00400078]> drj
{"x0":0,"x1":0,"x2":0,"x3":0,"x4":0,"x5":0,"x6":0,"x7":0,"x8":0,"x9":0,"x10":0,"x11":0,"x12":0,"x13":0,"x14":0,"x15":0,"x16":0,"x17":0,"x18":0,"x19":0,"x20":0,"x21":0,"x22":0,"x23":0,"x24":0,"x25":0,"x26":0,"x27":0,"x28":0,"x29":0,"x30":0,"sp":549705955536,"pc":4194428,"d0":0,"d1":0,"d2":0,"d3":0,"d4":0,"d5":0,"d6":0,"d7":0,"d8":0,"d9":0,"d10":0,"d11":0,"d12":0,"d13":0,"d14":0,"d15":0,"d16":0,"d17":0,"d18":0,"d19":0,"d20":0,"d21":0,"d22":0,"d23":0,"d24":0,"d25":0,"d26":0,"d27":0,"d28":0,"d29":0,"d30":0,"dsp":549705955536,"pstate":2097152,"fstate":2097152}
[0x00400078]>
source.zip <https://github.com/radare/radare2/files/3173907/source.zip>
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Oh, thanks for quick response. I forgot/didn't know that r2 is I guess assembling those instructions on its own. If I will have some free time I will definitely look into that. Thanks. |
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r2pm -i keystone and then use e asm.assembler=arm.ks and you may be able to assemble them using keystone inside r2. But its desirable to avoid this dependency and use our own assembler to not depend on c++ |
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Just tested them , and they all work fine, closing |
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Work environment
Expected behavior
I was using the
wa( wa write opcode, separated by ';' (use '"' around the command) command to write a instruction to binary that I am debugging. It seems like the assembler is giving the wrong results.wa add x0, x1, #3dsadd x0, x1, #3(but itsadd x0, x1, #0)drjand seex0 == 3(given everything is zero)I tried this also on x86 and it seems to work.
Actual behavior
For example:
wa add x0, x1, #3-> "add x0, x1, #0"wa neg x0, x1-> Cannot assemble 'neg x0, x1' at line 3wa sub x0, xzr, x1-> "sub x0, x0, x1"Steps to reproduce the behavior
or
source.zip
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