Human Readable Decoding of /proc/cpuinfo for Arm Processors

One of the most common way to get CPU information is to check the content of /proc/cpuinfo. For example, this is the output I get from running the command on NanoPi NEO (Allwinner H3) board:


Many fields are self-explanatory, but what about CPU implementer and CPU part numbers? Those are values stored in Arm’s CPUID Base Register, and 0x41 looks up to Arm implementer, while 0xc07 refers to Cortex A7. But I had to look it up to find out.

One solution would be to decode those values in the kernel, but the developers won’t do that probably because it may break user-space programs that rely on hexadecimal values. So instead,

In the meantime, I could try it out by compiling the code myself:


Let’s now run our freshly compiled lscpu to see if an Arm Cortex A7 processor is detected:


It works as ARM Cortex-A7 revision 5 is shown. It does not follow Arm’s new lower case logo / name, but who cares 🙂 We can see most of the information provided by /proc/cpuinfo and more, but the BogoMIPS number is different, and the last three lines with Hardware, Revision and Serial are not shown.

It’d be particular interesting to test it on products or boards with processors featuring custom Arm cores such as you should get values like “Qualcomm Krait” or “Marvell PJ4/PJ4b”.

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manuti
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Nice, really interesting to check all this Android TV with Amlogic SoC and know info without open the box.

Jason
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Jason

you could try installing the app Termux, which simulates a Debian-type Linux system. It works on Android 5.1 and up.

theguyuk
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theguyuk

Perhaps Linux and Android could take example from Windows and have a systems device program built in, to show hardware info.

I expect such a suggestion to have command line enthusiasts spitting their dummies out. Yet this is 2018, coding by hand in hex, moved on, the command line community, need to move on as well. The word of computing has got big and the one size fits all model is to anal.

Sandbender
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Sandbender
CampGareth
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CampGareth

@theguyuk
Though we can make a human-readable readout available, it can never be the only thing available. Ultimately everything’s still a bunch of 1s and 0s so some part of my PC can only process the hexadecimal form.

fossxplorer
Guest
fossxplorer

Ran it on a RK3328 SoC:
# ./lscpu
Architecture: aarch64
Byte Order: Little Endian
CPU(s): 4
On-line CPU(s) list: 0-3
Thread(s) per core: 1
Core(s) per socket: 4
Socket(s): 1
Vendor ID: ARM
Model: 4
Model name: Cortex-A53
Stepping: r0p4
CPU max MHz: 1296.0000
CPU min MHz: 408.0000
BogoMIPS: 48.00
Flags: fp asimd evtstrm aes pmull sha1 sha2 crc32
[email protected]:~/tmp/util-linux#

tkaiser
Guest
tkaiser

Weird, a tool suited for human beings displays this BogoMIPS BS (especially on ARM): en.wikipedia.org/wiki/BogoMips#Timer-based_delays

@fossxplorer
If you compare the Flags above with the following is this the same? Which kernel version are you running?

Joe Bleau
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Joe Bleau

r-pi 3 B:
Architecture: armv7l
Byte Order: Little Endian
CPU(s): 4
On-line CPU(s) list: 0-3
Thread(s) per core: 1
Core(s) per socket: 4
Socket(s): 1
Vendor ID: ARM
Model: 4
Model name: Cortex-A53
Stepping: r0p4
CPU max MHz: 1200.0000
CPU min MHz: 600.0000
BogoMIPS: 76.80
Flags: half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32

uname -a:
Linux pi7 4.9.59-v7+ #1047 SMP Sun Oct 29 12:19:23 GMT 2017 armv7l GNU/Linux

grep ‘^Features’ /proc/cpuinfo:
Features : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
Features : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
Features : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
Features : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32

Steve G
Guest
Steve G

Sheevaplug Armv5
# cat /proc/cpuinfo
processor: 0
model name: Feroceon 88FR131 rev 1 (v5l)
BogoMIPS: 400.00
Features: swp half thumb fastmult edsp
CPU implementer: 0x56
CPU architecture: 5TE
CPU variant: 0x2
CPU part: 0x131
CPU revision: 1

Hardware: Marvell Kirkwood (Flattened Device Tree)
Revision: 0000
Serial: 0000000000000000

[email protected]:/opt/util-linux# uname -a
Linux buster 4.14.0-3-marvell #1 Debian 4.14.13-1 (2018-01-14) armv5tel GNU/Linux

[email protected]:/opt/util-linux# ./lscpu
Architecture: armv5tel
Byte Order: Little Endian
CPU(s): 1
On-line CPU(s) list: 0
Thread(s) per core: 1
Core(s) per socket: 1
Socket(s): 1
Vendor ID: Marvell
Model: 1
Model name: Feroceon 88FR131
Stepping: 0x2
CPU max MHz: 1200.0000
CPU min MHz: 400.0000
BogoMIPS: 400.00
Flags: swp half thumb fastmult edsp

Steve G
Guest
Steve G

QEMU-aarch64 [Cortex53]

[email protected]:/opt/src/util-linux# cat /proc/cpuinfo
processor: 0
BogoMIPS: 125.00
Features: fp asimd evtstrm aes pmull sha1 sha2 crc32 cpuid
CPU implementer: 0x41
CPU architecture: 8
CPU variant: 0x0
CPU part: 0xd03
CPU revision: 4

processor: 1
BogoMIPS: 125.00
Features: fp asimd evtstrm aes pmull sha1 sha2 crc32 cpuid
CPU implementer: 0x41
CPU architecture: 8
CPU variant: 0x0
CPU part: 0xd03
CPU revision: 4

[email protected]:/opt/src/util-linux# uname -a
Linux busteraarch64 4.14.0-3-arm64 #1 SMP Debian 4.14.13-1 (2018-01-14) aarch64 GNU/Linux

[email protected]:/opt/src/util-linux# ./lscpu
Architecture: aarch64
Byte Order: Little Endian
CPU(s): 2
On-line CPU(s) list: 0,1
Thread(s) per core: 1
Core(s) per socket: 2
Socket(s): 1
NUMA node(s): 1
Vendor ID: ARM
Model: 4
Model name: Cortex-A53
Stepping: r0p4
BogoMIPS: 125.00
NUMA node0 CPU(s): 0,1
Flags: fp asimd evtstrm aes pmull sha1 sha2 crc32 cpuid

Riku Voipio
Guest
Riku Voipio

For the compilation instrucions, you can build just lscpu from the source tree:

make lscpu

util-linux 2.32 was just released, so you may want to nag your favourite distros to update util-linux.

tkaiser
Guest
tkaiser

@Riku Voipio
What @Steve G posted above:

Do you consider this being a bug?

Riku Voipio
Guest
Riku Voipio

@tkaiser
That doesn’t say “0 CPU(s) online”, but that “cpu number 0 is online”.

Jason
Guest
Jason

Here is the result from my Odroid XU3 (Samsung Exynos 5422 SOC)

$ ./lscpu
Architecture: armv7l
Byte Order: Little Endian
CPU(s): 8
On-line CPU(s) list: 0-7
Thread(s) per core: 1
Core(s) per socket: 4
Socket(s): 2
Vendor ID: ARM
Model: 3
Model name: Cortex-A7
Stepping: r0p3
CPU max MHz: 1800.0000
CPU min MHz: 200.0000
BogoMIPS: 36.00
Flags: half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm