How do I parse raw MIPS code?
Similarly How to parse raw x86 code? but then for the MIPS architecture: how to parse the raw MIPS code with objdump
? I want to check the instructions in the vmlinux image, but for that I now need:
: > x.c
mipsel-linux-gnu-gcc -c -o x.o x.c
mipsel-linux-gnu-objcopy --add-section raw=vmlinux x.o
mipsel-linux-gnu-objcopy --remove-section .comment x.o
mipsel-linux-gnu-objdump -D x.o | less
Is there an easier way to do this? I have tried the following to no avail:
mipsel-linux-gnu-objdump -b elf32-tradlittlemips -mmips -Mgpr-names=O32,cp0-names=mips1,cp0-names=mips1,hwr-names=mips1,reg-names=mips1 -D vmlinux | less
It just spits out:
mipsel-linux-gnu-objdump: vmlinux: File format not recognized
If that helps, here's the output of some commands:
$ file x.o
x.o: ELF 32-bit LSB relocatable, MIPS, MIPS-I version 1 (SYSV), with unknown capability 0xf41 = 0x756e6700, with unknown capability 0x70100 = 0x1040000, not stripped
$ mipsel-linux-gnu-objdump -p x.o
x.o: file format elf32-tradlittlemips
private flags = 1006: [abi=O32] [mips1] [not 32bitmode] [PIC] [CPIC]
Target - AR7 processor.
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Hmm, it seems easier. -b elf32-tradlittlemips
doesn't work because the file is not an ELF executable but a binary one. So, the correct option to be used is -b binary
. Another option -mmips
makes objdump recognize the file as binary for MIPS. Since the target machine is slightly oriented, I also had to add -EL
to make the output match the output for x.o
.
-mmips
includes only a basic set of commands. The AR7 has a MIPS32 processor that has more instructions than just mips. To decode these new MIPS32 instructions use -mmips:isa32
. The list of available ISAs can be specified with objdump -i -m
.
Final command:
mipsel-linux-gnu-objdump -b binary -mmips:isa32 -EL -D vmlinux
This will cause type registers to appear $3
instead of their names. To configure this, I used the following additional options, which are listed in mipsel-linux-gnu-objdump --help
:
-Mgpr-names=32,cp0-names=mips32,cp0-names=mips32,hwr-names=mips32,reg-names=mips32
I chose for mips32
after reading:
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??? What's wrong:
mipsel-linux-gnu-gcc -c -o x.o x.c
mipsel-linux-gnu-objdump -D x.o
Is it a problem that -D
all sections are flattened out by code or not? Then use -D
. Or -S
to show an assembly alternating with a source (implied -D
).
or how to get the assembly code from gcc:
mipsel-linux-gnu-gcc -S x.c
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