Android procfs demystified – cpuinfo

From cpuinfo in procfs, we get a lot information about the cpu on board, how many cores, architecture etc, here is an example output of cpuinfo of RPI 3B+:

# cat /proc/cpuinfo
processor	: 0
model name	: ARMv7 Processor rev 4 (v7l)
BogoMIPS	: 89.60
Features	: half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
CPU implementer	: 0x41
CPU architecture: 7
CPU variant	: 0x0
CPU part	: 0xd03
CPU revision	: 4

processor	: 1
model name	: ARMv7 Processor rev 4 (v7l)
BogoMIPS	: 89.60
Features	: half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
CPU implementer	: 0x41
CPU architecture: 7
CPU variant	: 0x0
CPU part	: 0xd03
CPU revision	: 4

processor	: 2
model name	: ARMv7 Processor rev 4 (v7l)
BogoMIPS	: 89.60
Features	: half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
CPU implementer	: 0x41
CPU architecture: 7
CPU variant	: 0x0
CPU part	: 0xd03
CPU revision	: 4

processor	: 3
model name	: ARMv7 Processor rev 4 (v7l)
BogoMIPS	: 89.60
Features	: half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm crc32
CPU implementer	: 0x41
CPU architecture: 7
CPU variant	: 0x0
CPU part	: 0xd03
CPU revision	: 4

Hardware	: BCM2835
Revision	: a020d3
Serial		: 000000008210e7dd

The above output has hexidecimal code which are not understandable for us, these info can be interpreted by looking up the Main ID Register, EL1, below is taken from arm infocenter describing this register:

util-linux maintains a list of part number and its model name in lscpu-arm.c, this is an excerption of that list:

    { 0xc05, "Cortex-A5" },
    { 0xc07, "Cortex-A7" },
    { 0xc08, "Cortex-A8" },
    { 0xc09, "Cortex-A9" },
    { 0xc0d, "Cortex-A17" },	/* Originally A12 */
    { 0xc0f, "Cortex-A15" },
    { 0xc0e, "Cortex-A17" },
    { 0xc14, "Cortex-R4" },
    { 0xc15, "Cortex-R5" },
    { 0xc17, "Cortex-R7" },
    { 0xc18, "Cortex-R8" },
    { 0xc20, "Cortex-M0" },
    { 0xc21, "Cortex-M1" },
    { 0xc23, "Cortex-M3" },
    { 0xc24, "Cortex-M4" },
    { 0xc27, "Cortex-M7" },
    { 0xc60, "Cortex-M0+" },
    { 0xd01, "Cortex-A32" },
    { 0xd03, "Cortex-A53" },
    { 0xd04, "Cortex-A35" },
    { 0xd05, "Cortex-A55" },
    { 0xd07, "Cortex-A57" },
    { 0xd08, "Cortex-A72" },
    { 0xd09, "Cortex-A73" },
    { 0xd0a, "Cortex-A75" },
    { 0xd0b, "Cortex-A76" },

Another way to interprete those information is by using lscpu, which is part of util-linux, first download archive from kernel.org, or clone source code from github, then build as a static executable:

$ ./configure --host=arm-linux-gnueabihf --disable-shared --enable-static-programs=lscpu
$ make LDFLAGS=--static CC=arm-linux-gnueabihf-gcc lscpu

Now do lscpu can show human readable info:

# lscpu
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:         1400.0000
CPU min MHz:         600.0000
BogoMIPS:            38.40
Flags:               half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idi
                     vt vfpd32 lpae evtstrm crc32

ARM Features

Up until now, there is one more thing that was not made clear, what does those features mean, what are they stand for, below table was taken from WikiChip: