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llarm CPU C Documentation

Contents


llarm_cpu_fetch_midr()

This is the core function of the library. It reads the Main ID Register (MIDR) directly from the CPU via the mrc p15 coprocessor instruction and returns a unsigned int. All other fetch functions derive their data from this value.

#include "llarm_cpu.h"

int main() {
    unsigned int midr = llarm_cpu_fetch_midr();
    printf("MIDR: 0x%08X\n", midr);
    return 0;
}

Note

On x86 platforms, this function always returns 0. All dependent functions return neutral/unknown values as a result.


llarm_cpu_is_pre_arm7(), llarm_cpu_is_arm7(), and llarm_cpu_is_post_arm7()

Returns a bool indicating whether its release date relative to the ARM7 architecture.

#include "llarm_cpu.h"

int main() {
    if (llarm_cpu_is_arm7()) {
        printf("This CPU is ARM7.\n");
    }

    if (llarm_cpu_is_post_arm7()) {
        printf("This CPU is newer than ARM7.\n");
    }


    if (llarm_cpu_is_pre_arm7()) {
        printf("This CPU is older than ARM7.\n");
    }
    return 0;
}

llarm_cpu_fetch_revision()

Returns an unsigned int representing the revision field of the MIDR (bits 3:0). This is the minor stepping of the CPU, distinct from the variant.

unsigned int rev = llarm_cpu_fetch_revision();
printf("CPU revision: r%u\n", rev);

llarm_cpu_fetch_ppn()

Returns an unsigned int representing the Primary Part Number (PPN). This is the main identifier used to distinguish specific CPU products within a given implementor.

Note

Returns 0 for pre-ARM7 CPUs, as the MIDR format is different for those parts.


llarm_cpu_fetch_variant()

Returns an unsigned int for the variant field of the MIDR. This represents the major stepping of the CPU.


llarm_cpu_fetch_implementor()

Returns an enum implementor identifying the company that manufactured the CPU.

#include "llarm_cpu.h"

int main() {
    enum implementor impl = llarm_cpu_fetch_implementor();

    if (impl == IMPL_APPLE) {
        // Apple Silicon specific path
    } else if (impl == IMPL_QUALCOMM) {
        // Qualcomm Snapdragon specific path
    }

    return 0;
}

If the implementor byte does not match any known value, the function returns IMPL_UNKNOWN. See the implementor table for all supported values.


llarm_cpu_fetch_implementor_string()

Returns a const char* string name for the current CPU's implementor. This is a convenience wrapper around llarm_cpu_fetch_implementor().

printf("Implementor: %s\n", llarm_cpu_fetch_implementor_string());
// example output: "APPLE"

llarm_cpu_fetch_product()

Returns an enum product identifying the specific CPU core. It combines the implementor, the generation check, and the PPN to produce a precise product match.

#include "llarm_cpu.h"

int main() {
    enum product prod = llarm_cpu_fetch_product();

    switch (prod) {
        case PROD_CORTEX_A76:
            printf("Cortex-A76 detected\n");
            break;
        case PROD_APPLE_FIRESTORM:
            printf("Apple M1 performance core detected\n");
            break;
        case PROD_UNKNOWN:
        default:
            printf("Product not recognised\n");
            break;
    }

    return 0;
}

See the product table for all supported products.

Important

A result of PROD_UNKNOWN does not mean the CPU is invalid. It means the specific part is not in the library's database. This is common for very old pre-ARM7 parts and newer unreleased silicon, but the lib will do its best to be as up-to-date as possible.


llarm_cpu_fetch_product_string()

Returns a const char* string for a given enum product. Unlike most other fetch functions, this one takes an explicit product argument rather than reading the MIDR itself.

enum product prod = llarm_cpu_fetch_product();
const char* name = llarm_cpu_fetch_product_string(prod);
printf("Product: %s\n", name);
// example output: "CORTEX_A76"

llarm_cpu_fetch_arch()

Returns an enum arch identifying the ARM architecture version of the current CPU.

#include "llarm_cpu.h"

int main() {
    enum arch a = llarm_cpu_fetch_arch();

    if (a == ARCH_ARMv8_A) {
        printf("64-bit capable ARMv8-A CPU\n");
    }

    return 0;
}

See the architecture table for all supported archs


llarm_cpu_fetch_arch_string()

Returns a const char* string for a given enum arch. Takes an explicit arch argument.

enum arch a = llarm_cpu_fetch_arch();
printf("Architecture: %s\n", llarm_cpu_fetch_arch_string(a));
// example output: "ARMv8-A"

Enum tables

Implementor table

Enum Implementor ID byte
IMPL_ARM ARM 0x41
IMPL_BRCM Broadcom 0x42
IMPL_DEC Digital Equipment Corporation 0x44
IMPL_MOTOROLA Motorola 0x4D
IMPL_QUALCOMM Qualcomm 0x51
IMPL_MARVELL Marvell 0x56
IMPL_INTEL Intel 0x69
IMPL_CAVIUM Cavium 0x43
IMPL_FUJITSU Fujitsu 0x46
IMPL_INFINEON Infineon 0x49
IMPL_NVIDIA NVIDIA 0x4E
IMPL_APM Applied Micro Circuits Corporation 0x50
IMPL_SAMSUNG Samsung 0x53
IMPL_TI Texas Instruments 0x54
IMPL_APPLE Apple 0x61
IMPL_FARADAY Faraday 0x66
IMPL_AMPERE Ampere 0xC0
IMPL_HISI HiSilicon 0x48
IMPL_MICROSOFT Microsoft 0x6D
IMPL_LLARM LLARM (custom) 0x4C
IMPL_UNKNOWN Unknown —

Product table

ARM Classic

Enum Product PPN
PROD_ARM3 ARM3 —
PROD_ARM600 ARM600 —
PROD_ARM610 ARM610 —
PROD_ARM620 ARM620 —
PROD_ARM700 ARM700 —
PROD_ARM710 ARM710 —
PROD_ARM710A ARM710A —
PROD_ARM710T ARM710T —
PROD_ARM720T ARM720T —
PROD_ARM740T ARM740T —
PROD_ARM810 ARM810 0x810
PROD_ARM920T ARM920T 0x920
PROD_ARM922T ARM922T 0x922
PROD_ARM926EJ_S ARM926EJ-S 0x926
PROD_ARM940T ARM940T 0x940
PROD_ARM946E_S ARM946E-S 0x946
PROD_ARM966E_S ARM966E-S 0x966
PROD_ARM1020E ARM1020E 0xA20
PROD_ARM1022E ARM1022E 0xA22
PROD_ARM1026EJ_S ARM1026EJ-S 0xA26
PROD_ARM11MPCORE ARM11 MPCore 0xB02
PROD_ARM1136JF_S ARM1136JF-S 0xB36
PROD_ARM1156T2F_S ARM1156T2F-S 0xB56
PROD_ARM1176JZF_S ARM1176JZF-S 0xB76

ARM Cortex-M

Enum Product PPN
PROD_CORTEX_M0 Cortex-M0 0xC20
PROD_CORTEX_M0_PLUS Cortex-M0+ 0xC60
PROD_CORTEX_M1 Cortex-M1 0xC21
PROD_CORTEX_M3 Cortex-M3 0xC23
PROD_CORTEX_M4 Cortex-M4 0xC24
PROD_CORTEX_M7 Cortex-M7 0xC27
PROD_CORTEX_M23 Cortex-M23 0xD20
PROD_CORTEX_M33 Cortex-M33 0xD21
PROD_CORTEX_M35P Cortex-M35P 0xD31
PROD_CORTEX_M55 Cortex-M55 0xD50

ARM Cortex-R

Enum Product PPN
PROD_CORTEX_R4 Cortex-R4 0xC14
PROD_CORTEX_R5 Cortex-R5 0xC15
PROD_CORTEX_R7 Cortex-R7 0xC17
PROD_CORTEX_R8 Cortex-R8 0xC18
PROD_CORTEX_R52 Cortex-R52 0xD13
PROD_CORTEX_R52_PLUS Cortex-R52+ 0xD16
PROD_CORTEX_R82 Cortex-R82 0xD15

ARM Cortex-A (ARMv7)

Enum Product PPN
PROD_CORTEX_A5 Cortex-A5 0xC05
PROD_CORTEX_A7 Cortex-A7 0xC07
PROD_CORTEX_A8 Cortex-A8 0xC08
PROD_CORTEX_A9 Cortex-A9 0xC09
PROD_CORTEX_A12 Cortex-A12 0xC0D
PROD_CORTEX_A15 Cortex-A15 0xC0F
PROD_CORTEX_A17 Cortex-A17 0xC0E

ARM Cortex-A (ARMv8+)

Enum Product PPN
PROD_CORTEX_A32 Cortex-A32 0xD01
PROD_CORTEX_A34 Cortex-A34 0xD02
PROD_CORTEX_A35 Cortex-A35 0xD04
PROD_CORTEX_A53 Cortex-A53 0xD03
PROD_CORTEX_A55 Cortex-A55 0xD05
PROD_CORTEX_A57 Cortex-A57 0xD07
PROD_CORTEX_A65 Cortex-A65 0xD06
PROD_CORTEX_A65AE Cortex-A65AE 0xD43
PROD_CORTEX_A72 Cortex-A72 0xD08
PROD_CORTEX_A73 Cortex-A73 0xD09
PROD_CORTEX_A75 Cortex-A75 0xD0A
PROD_CORTEX_A76 Cortex-A76 0xD0B
PROD_CORTEX_A76AE Cortex-A76AE 0xD0E
PROD_CORTEX_A77 Cortex-A77 0xD0D
PROD_CORTEX_A78 Cortex-A78 0xD41
PROD_CORTEX_A78AE Cortex-A78AE 0xD42
PROD_CORTEX_A78C Cortex-A78C 0xD4B
PROD_CORTEX_A510 Cortex-A510 0xD46
PROD_CORTEX_A520 Cortex-A520 0xD80
PROD_CORTEX_A710 Cortex-A710 0xD47
PROD_CORTEX_A715 Cortex-A715 0xD4D
PROD_CORTEX_A720 Cortex-A720 0xD81
PROD_CORTEX_A725 Cortex-A725 0xD87

ARM Cortex-X

Enum Product PPN
PROD_CORTEX_X1 Cortex-X1 0xD44
PROD_CORTEX_X2 Cortex-X2 0xD48
PROD_CORTEX_X3 Cortex-X3 0xD4E
PROD_CORTEX_X4 Cortex-X4 0xD82
PROD_CORTEX_X925 Cortex-X925 0xD85

ARM Neoverse

Enum Product PPN
PROD_NEOVERSE_E1 Neoverse E1 0xD4A
PROD_NEOVERSE_N1 Neoverse N1 0xD0C
PROD_NEOVERSE_N2 Neoverse N2 0xD49
PROD_NEOVERSE_N3 Neoverse N3 0xD8E
PROD_NEOVERSE_V1 Neoverse V1 0xD40
PROD_NEOVERSE_V2 Neoverse V2 0xD4F
PROD_NEOVERSE_V3 Neoverse V3 0xD84

Qualcomm

Enum Product PPN Notes
PROD_QCOM_SCORPION Scorpion 0x00F Snapdragon S1/S2 (ARMv7)
PROD_QCOM_SCORPION_MP Scorpion MP 0x02D Snapdragon S3/S4 multi-core (ARMv7)
PROD_QCOM_KRAIT Krait 0x04D Snapdragon 200/400 (ARMv7)
PROD_QCOM_KRAIT_S4_PRO Krait S4 Pro 0x06F Snapdragon 600/800 (ARMv7)
PROD_QCOM_KRYO Kryo 0x200 Snapdragon 820/821 custom (ARMv8)
PROD_QCOM_FALKOR_V1 Falkor v1 0x800 Centriq 2400 early silicon (server)
PROD_QCOM_FALKOR Falkor 0xC00 Centriq 2400 (server)
PROD_QCOM_KRYO_3XX_SILVER Kryo 3xx Silver 0x803 Snapdragon 845 little (semi-custom A55)
PROD_QCOM_KRYO_4XX_GOLD Kryo 4xx Gold 0x804 Snapdragon 855/865 big (semi-custom A76)
PROD_QCOM_KRYO_4XX_SILVER Kryo 4xx Silver 0x805 Snapdragon 855/865 little (semi-custom A55)
PROD_QCOM_KRYO_5XX_GOLD Kryo 5xx Gold 0x806 Snapdragon 888 big (semi-custom A78)
PROD_QCOM_KRYO_5XX_SILVER Kryo 5xx Silver 0x807 Snapdragon 888 little (semi-custom A55)
PROD_QCOM_ORYON Oryon 0x001 Snapdragon X Elite (custom ARMv9)

Apple

Enum Product PPN Notes
PROD_APPLE_ICESTORM Icestorm 0x022 M1 efficiency core
PROD_APPLE_FIRESTORM Firestorm 0x023 M1 performance core
PROD_APPLE_ICESTORM_PRO Icestorm Pro 0x024 M1 Pro/Max efficiency core
PROD_APPLE_FIRESTORM_PRO Firestorm Pro 0x025 M1 Pro/Max performance core
PROD_APPLE_ICESTORM_MAX Icestorm Max 0x028 M1 Ultra efficiency core
PROD_APPLE_FIRESTORM_MAX Firestorm Max 0x029 M1 Ultra performance core
PROD_APPLE_BLIZZARD Blizzard 0x032 M2 efficiency core
PROD_APPLE_AVALANCHE Avalanche 0x033 M2 performance core

Note

Apple A-series identifiers (A7 through A13) are derived from reverse engineering and Asahi Linux work. They are not in the table above and are not matched by the library. The PPNs listed for M1 and M2 are confirmed via mainline kernel sources.

Samsung Mongoose

Enum Product PPN SoC
PROD_SAMSUNG_M1 Mongoose M1 0x001 Exynos 8890 (2016)
PROD_SAMSUNG_M2 Mongoose M2 0x002 Exynos 8895 (2017)
PROD_SAMSUNG_M3 Mongoose M3 0x003 Exynos 9810 (2018)
PROD_SAMSUNG_M4 Mongoose M4 0x004 Exynos 9820 (2019)
PROD_SAMSUNG_M5 Mongoose M5 0x005 Exynos 990 (2020)

Other implementors

Enum Product Implementor PPN
PROD_CAVIUM_THUNDERX ThunderX Cavium 0x0A1
PROD_CAVIUM_THUNDERX_81XX ThunderX CN81xx Cavium 0x0A2
PROD_CAVIUM_THUNDERX_83XX ThunderX CN83xx Cavium 0x0A3
PROD_CAVIUM_THUNDERX2 ThunderX2 Cavium 0x0AF
PROD_NVIDIA_DENVER Denver 2 NVIDIA 0x003
PROD_NVIDIA_CARMEL Carmel NVIDIA 0x004
PROD_FUJITSU_A64FX A64FX Fujitsu 0x001
PROD_HISI_TSV110 TSV110 / Kunpeng 920 HiSilicon 0xD01
PROD_APM_POTENZA X-Gene APM 0x000

Architecture table

Enum String Notes
ARCH_UNKNOWN UNKNOWN Default when the arch cannot be determined
ARCH_ARMv1 ARMv1
ARCH_ARMv2 ARMv2
ARCH_ARMv2a ARMv2a ARM3
ARCH_ARMv3 ARMv3 ARM600 series and base ARM7
ARCH_ARMv3M ARMv3M
ARCH_ARMv4 ARMv4
ARCH_ARMv4xM ARMv4xM
ARCH_ARMv4T ARMv4T ARM7 with Thumb support
ARCH_ARMv4TxM ARMv4TxM
ARCH_ARMv5 ARMv5
ARCH_ARMv5xM ARMv5xM
ARCH_ARMv5T ARMv5T
ARCH_ARMv5TxM ARMv5TxM
ARCH_ARMv5TE ARMv5TE
ARCH_ARMv5TExP ARMv5TExP
ARCH_ARMv5TEJ ARMv5TEJ
ARCH_ARMv6 ARMv6
ARCH_ARMv6T2 ARMv6T2
ARCH_ARMv6Z ARMv6Z
ARCH_ARMv6K ARMv6K
ARCH_ARMv6_M ARMv6-M
ARCH_ARMv7_A ARMv7-A
ARCH_ARMv7_M ARMv7-M
ARCH_ARMv7_R ARMv7-R
ARCH_ARMv7E_M ARMv7E-M
ARCH_ARMv8_A ARMv8-A
ARCH_ARMv8_R ARMv8-R
ARCH_ARMv8_M_BASELINE ARMv8-M Baseline
ARCH_ARMv8_M_MAINLINE ARMv8-M Mainline
ARCH_ARMv8_1_M_MAINLINE ARMv8.1-M Mainline
ARCH_ARMv8_2_A ARMv8.2-A
ARCH_ARMv8_3_A ARMv8.3-A
ARCH_ARMv8_4_A ARMv8.4-A
ARCH_ARMv8_5_A ARMv8.5-A
ARCH_ARMv8_6_A ARMv8.6-A
ARCH_ARMv9_A ARMv9-A
ARCH_ARMv9_2_A ARMv9.2-A

Platform notes

The library uses compile-time guards to handle cross-platform behavior cleanly.

  • x86/x86_64: All fetch functions return 0, false, IMPL_UNKNOWN, PROD_UNKNOWN, or ARCH_UNKNOWN as appropriate. llarm_cpu_fetch_bits() is not compiled at all. The library will not crash on x86, but it will not produce useful data either.
  • ARM (32-bit and 64-bit): Full functionality. The MIDR is read via the mrc p15, 0, %0, c0, c0, 0 inline assembly instruction.
  • Other architectures: Treated the same as x86. The is_x86 guard defaults to not defined, so the ARM path compiles. This may cause build errors on architectures that do not support the mrc instruction. Guard your include accordingly if targeting non-ARM, non-x86 platforms.