Trying to decode:
0x15882BCD0xC3A01B28
I keep on getting the LDMDAHS instruction, but I know that isn't right. Could someone help?
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1
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Can you explain the steps you took which led you to that conclusion? – Jeff Apr 13 '20 at 19:25
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I get `stcgt 8, cr8, [fp, #-84]!; ldmdacs fp, {r0, r1, r6, r7, sp, pc}` in little endian and `strne r2, [r8, #3021]; movgt r1, #40, 22` in big endian. I suppose you got the byte order wrong. – fuz Apr 13 '20 at 19:28
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@fuz I was looking at big Endian, I arrived at MOVGT r1 for the 2nd answer but I was unsure how to align it. do you shift the last 12 or last 8? Also you're right, I did get the byte order wrong.. – R B Apr 13 '20 at 19:37
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1@RB I used `objdump` to disassemble the instructions. I did not attempt to disassemble them myself. – fuz Apr 13 '20 at 19:40
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For the 1st one, it seems the Big Endian format is ORRPL R2, R8, SP, ASR #23 (according to an online converter). http://armconverter.com/hextoarm/ not sure which is right then – R B Apr 13 '20 at 19:45
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big endian I dont think the instructions change byte order. if you read them from wherever with a data access then perhaps they are reversed... – old_timer Apr 13 '20 at 20:01
1 Answers
1
.inst 0x15882BCD
.inst 0xC3A01B28
.thumb
.inst 0x2BCD
.inst 0x1588
.inst 0x1B28
.inst 0xC3A0
arm-none-eabi-as so.s -o so.o
arm-none-eabi-objdump -D so.o
so.o: file format elf32-littlearm
Disassembly of section .text:
00000000 <.text>:
0: 15882bcd strne r2, [r8, #3021] ; 0xbcd
4: c3a01b28 movgt r1, #40, 22 ; 0xa000
8: 2bcd cmp r3, #205 ; 0xcd
a: 1588 asrs r0, r1, #22
c: 1b28 subs r0, r5, r4
e: c3a0 stmia r3!, {r5, r7}
does this resemble what you were looking for?
byteswapped
.inst 0xcd2b8815
.inst 0x281ba0c3
.thumb
.inst 0x8815
.inst 0xcd2b
.inst 0xa0c3
.inst 0x281b
00000000 <.text>:
0: cd2b8815 stcgt 8, cr8, [r11, #-84]! ; 0xffffffac
4: 281ba0c3 ldmdacs r11, {r0, r1, r6, r7, sp, pc}
8: 8815 ldrh r5, [r2, #0]
a: cd2b ldmia r5, {r0, r1, r3, r5}
c: a0c3 add r0, pc, #780 ; (adr r0, 31c <.text+0x31c>)
e: 281b cmp r0, #27
Note that depending on which version of binutils you might need to mess with .word, .hword, .inst.n, .inst.w wait that reminds me...
.thumb
.syntax unified
.inst.w 0x15882BCD
.inst.w 0xC3A01B28
Disassembly of section .text:
00000000 <.text>:
0: 1588 asrs r0, r1, #22
2: 2bcd cmp r3, #205 ; 0xcd
4: c3a0 stmia r3!, {r5, r7}
6: 1b28 subs r0, r5, r4
Yes, those are not thumb2 instructions (distinct pattern) and they don't look like aarch32, but...
so.o: file format elf64-littleaarch64
Disassembly of section .text:
0000000000000000 <.text>:
0: 15882bcd b 620af34 <.text+0x620af34>
4: c3a01b28 .inst 0xc3a01b28 ; undefined
I don't think its aarch64.
