diff options
Diffstat (limited to 'md/writeup/arm64_assembly_crc32.md')
| -rw-r--r-- | md/writeup/arm64_assembly_crc32.md | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/md/writeup/arm64_assembly_crc32.md b/md/writeup/arm64_assembly_crc32.md new file mode 100644 index 0000000..c284349 --- /dev/null +++ b/md/writeup/arm64_assembly_crc32.md @@ -0,0 +1,241 @@ +title:ARM64 assembly crc32 +keywords:assembly,m1,arm64,macos,linux + +# ARM64 assembly crc32 + +## Intro + +Latest ARM64 processors support hardware crc32 instruction, since architecture version __ARMv8.1-A__ . +Raspbery pi have architecture version __ARMv8-A__ version and Apple M1 __ARMv8.4-A__. Both of those +have hardware accelerated crc32 instruction. In example is shown how to use software and hardware implementation of +that functionality for macos and linux. + +## Verify architecture + +### Raspberry Pi 4 + +Run command +``` +uname -a +Linux raspberrypi 5.4.42-v8+ #1319 SMP PREEMPT Wed May 20 14:18:56 BST 2020 aarch64 GNU/Linux +``` +There is substring "aarch64" that indicates that os bitnes is 64bit + +To check if CPU supports crc32 instructions run +``` +cat /proc/cpuinfo | grep crc +``` +check for "crc32" substring + +### Apple M1 + +If you have Apple M1 then you already know it. If not sure run one of those commands to verify archirecture + +``` +uname -a +``` + +or +``` +arch +``` + +in output string should be "arm64" + +## ARM64 crc32 instructions + +Wiki have table with all different kind of implementation of crc32 https://en.wikipedia.org/wiki/Cyclic_redundancy_check +arm64 crc32 implementation reffered in wiki table as __CRC-32__. There is support also for __CRC-32C__. + +There is 4 types of crc32 instruction for 1,2,4,8 byte of data that are marked with +postfix b,h,w,x. +Wraped up examples of instructions: +```c +#define CRC32X(crc, value) __asm__("crc32x %w[c], %w[c], %x[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32W(crc, value) __asm__("crc32w %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32H(crc, value) __asm__("crc32h %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32B(crc, value) __asm__("crc32b %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32CX(crc, value) __asm__("crc32cx %w[c], %w[c], %x[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32CW(crc, value) __asm__("crc32cw %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32CH(crc, value) __asm__("crc32ch %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32CB(crc, value) __asm__("crc32cb %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +``` + +https://android.googlesource.com/platform/external/linux-kselftest/+/d97034ccdf0a13ad86f00945df245bbaf0780478/arch/arm64/crypto/crc32-arm64.c + +## Software implementation + +Found crc32 software implementation as its helps verify HW instruction results. It verify that +algorithm used is correct against CRC32 table in wiki and that there is no other quirks for using crc32. + +Short implementation of crc32 with initial table generation + +http://home.thep.lu.se/~bjorn/crc/ + +There is implementation from BSD kernel where crc32 value tables are precalculated. + +https://web.mit.edu/freebsd/head/sys/libkern/crc32.c + +```c +uint32_t crc32_for_byte(uint32_t r) { + for(int j = 0; j < 8; ++j) + r = (r & 1? 0: (uint32_t)0xEDB88320L) ^ r >> 1; + return r ^ (uint32_t)0xFF000000L; +} + +void crc32(const void *data, size_t n_bytes, uint32_t* crc) { + static uint32_t table[0x100]; + if(!*table) + for(size_t i = 0; i < 0x100; ++i) + table[i] = crc32_for_byte(i); + for(size_t i = 0; i < n_bytes; ++i) + *crc = table[(uint8_t)*crc ^ ((uint8_t*)data)[i]] ^ *crc >> 8; +} +``` + +## HW and SW implementation differences + +when using assembly instruction please note that initial value of crc is __crc=0xffffffff__ +and final result should be inverted __~crc__ to match software implementation where +initial values is __crc=0x0__ and final result not need to be preprocessed. + + +## Source code +```c +#include <stdlib.h> +#include <stdio.h> +#include <unistd.h> +#include <stdint.h> + +/* +https://android.googlesource.com/platform/external/linux-kselftest/+/d97034ccdf0a13ad86f00945df245bbaf0780478/arch/arm64/crypto/crc32-arm64.c +*/ +#define CRC32X(crc, value) __asm__("crc32x %w[c], %w[c], %x[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32W(crc, value) __asm__("crc32w %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32H(crc, value) __asm__("crc32h %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32B(crc, value) __asm__("crc32b %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32CX(crc, value) __asm__("crc32cx %w[c], %w[c], %x[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32CW(crc, value) __asm__("crc32cw %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32CH(crc, value) __asm__("crc32ch %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) +#define CRC32CB(crc, value) __asm__("crc32cb %w[c], %w[c], %w[v]":[c]"+r"(crc):[v]"r"(value)) + +/* +http://home.thep.lu.se/~bjorn/crc/ +*/ + +uint32_t crc32_for_byte(uint32_t r) { + for(int j = 0; j < 8; ++j) + r = (r & 1? 0: (uint32_t)0xEDB88320L) ^ r >> 1; + return r ^ (uint32_t)0xFF000000L; +} + +static uint32_t crc32_tab_ver1[0x100]; +void crc32_ver1(const void *data, size_t n_bytes, uint32_t* crc) { + static uint32_t table[0x100]; + if(!*table) + for(size_t i = 0; i < 0x100; ++i) + crc32_tab_ver1[i] = crc32_for_byte(i); + for(size_t i = 0; i < n_bytes; ++i) + *crc = crc32_tab_ver1[(uint8_t)*crc ^ ((uint8_t*)data)[i]] ^ *crc >> 8; +} + +/* +https://web.mit.edu/freebsd/head/sys/libkern/crc32.c +*/ +const uint32_t crc32_tab_ver2[] = { + 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, + 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, + 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2, + 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, + 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, + 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, + 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c, + 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, + 0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, + 0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, + 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106, + 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433, + 0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, + 0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, + 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, + 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, + 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, + 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, + 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, + 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, + 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, + 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, + 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84, + 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, + 0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, + 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, + 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e, + 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b, + 0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, + 0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, + 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28, + 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, + 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, + 0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, + 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242, + 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, + 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, + 0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, + 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, + 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, + 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, + 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, + 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d +}; + +uint32_t crc32_ver2(const void *buf, size_t size) +{ + const uint8_t *p = buf; + uint32_t crc; + + crc = ~0U; + while (size--) + crc = crc32_tab_ver2[(crc ^ *p++) & 0xFF] ^ (crc >> 8); + return crc ^ ~0U; +} + +static uint8_t test_data[] = {0xaa,0xbb,0xcc,0xdd,0xee,0xff,0x00,0x11}; + +int main() { + size_t i=0; + + uint32_t crc_1=0x00000000, crc_2=0x00000000, crc_3=0xffffffff; + + printf("Initial values: SW1:%08x SW2:%08x HW:%08x\n",crc_1,crc_2,crc_3); + for (i=0;i<sizeof(test_data);i++) { + CRC32B(crc_3,test_data[i]); + } + crc32_ver1(test_data, sizeof(test_data),&crc_1); + crc_2 = crc32_ver2(test_data,sizeof(test_data)); + printf("Final result: SW1:%08x SW2:%08x HW:%08x\n",crc_1,crc_2,~crc_3); +} +``` +## Compile + +### Raspbery Pi 4 + +``` +gcc asm_crc32.c -o asm_crc32 -march=armv8.1-a +``` + +### Apple M1 + +``` +gcc asm_crc32.c -o asm_crc32 +``` + +## Links + +[01]https://en.wikipedia.org/wiki/Cyclic_redundancy_check +[02]http://home.thep.lu.se/~bjorn/crc/ +[03]https://web.mit.edu/freebsd/head/sys/libkern/crc32.c +[04]https://developer.arm.com/documentation/dui0801/g/A32-and-T32-Instructions/CRC32 +[05]https://en.wikipedia.org/wiki/Mathematics_of_cyclic_redundancy_checks#Polynomial_representations +[06]https://stackoverflow.com/questions/60693089/what-initial-value-should-i-pass-to-the-aarch64-crc32-instructions +[07]https://gcc.gnu.org/onlinedocs/gcc/AArch64-Options.html +[08][main.lv/writeup/arm64_assembly_hello_world.md](/writeup/arm64_assembly_hello_world.md) |