Android cpu信息获取/修改

信息获取/修改"/>

Android cpu信息获取/修改

CPU信息查看

通过 cat proc/cpuinfo 查看

processor       : 7
BogoMIPS        : 38.40
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 cpuid
CPU implementer : 0x51
CPU architecture: 8
CPU variant     : 0xa
CPU part        : 0x800
CPU revision    : 2Hardware        : Qualcomm Technologies, Inc

应用端，类似某兔兔中CPU信息应该也是从这里获取的

CPU信息修改 

 cpuinfo 文件内容是在 kernel/msm-4.19/arch/arm64/kernel/cpuinfo.c 中 c_show 函数中写入的

static int c_show(struct seq_file *m, void *v)
{int i, j;bool compat = personality(current->personality) == PER_LINUX32;seq_printf(m, "Processor\t: AArch64 Processor rev %d (%s)\n",read_cpuid_id() & 15, ELF_PLATFORM);for_each_present_cpu(i) {struct cpuinfo_arm64 *cpuinfo = &per_cpu(cpu_data, i);u32 midr = cpuinfo->reg_midr;/** glibc reads /proc/cpuinfo to determine the number of* online processors, looking for lines beginning with* "processor".  Give glibc what it expects.*/seq_printf(m, "processor\t: %d\n", i);if (compat)seq_printf(m, "model name\t: ARMv8 Processor rev %d (%s)\n",MIDR_REVISION(midr), COMPAT_ELF_PLATFORM);seq_printf(m, "BogoMIPS\t: %lu.%02lu\n",loops_per_jiffy / (500000UL/HZ),loops_per_jiffy / (5000UL/HZ) % 100);/** Dump out the common processor features in a single line.* Userspace should read the hwcaps with getauxval(AT_HWCAP)* rather than attempting to parse this, but there's a body of* software which does already (at least for 32-bit).*/seq_puts(m, "Features\t:");if (compat) {
#ifdef CONFIG_COMPATfor (j = 0; compat_hwcap_str[j]; j++)if (compat_elf_hwcap & (1 << j))seq_printf(m, " %s", compat_hwcap_str[j]);for (j = 0; compat_hwcap2_str[j]; j++)if (compat_elf_hwcap2 & (1 << j))seq_printf(m, " %s", compat_hwcap2_str[j]);
#endif /* CONFIG_COMPAT */} else {for (j = 0; hwcap_str[j]; j++)if (elf_hwcap & (1 << j))seq_printf(m, " %s", hwcap_str[j]);}seq_puts(m, "\n");seq_printf(m, "CPU implementer\t: 0x%02x\n",MIDR_IMPLEMENTOR(midr));seq_printf(m, "CPU architecture: 8\n");seq_printf(m, "CPU variant\t: 0x%x\n", MIDR_VARIANT(midr));seq_printf(m, "CPU part\t: 0x%03x\n", MIDR_PARTNUM(midr));seq_printf(m, "CPU revision\t: %d\n\n", MIDR_REVISION(midr));}if (!arch_read_hardware_id)seq_printf(m, "Hardware\t: %s\n", machine_name);elseseq_printf(m, "Hardware\t: %s\n", arch_read_hardware_id());return 0;
}

注：上面 arch_read_hardware_id 函数，高通平台是在 kernel/msm-4.19/drivers/soc/qcom/socinfo.c 文件中，等于 msm_read_hardware_id 函数

static char *msm_read_hardware_id(void)
{static char msm_soc_str[256] = "Qualcomm Technologies, Inc ";static bool string_generated;int ret = 0;if (string_generated)return msm_soc_str;if (!socinfo)goto err_path;if (!cpu_of_id[socinfo->v0_1.id].soc_id_string)goto err_path;ret = strlcat(msm_soc_str, cpu_of_id[socinfo->v0_1.id].soc_id_string,sizeof(msm_soc_str));if (ret > sizeof(msm_soc_str))goto err_path;string_generated = true;return msm_soc_str;
err_path:return "UNKNOWN SOC TYPE";
}

这里就是将高通和芯片名称 soc_id_string 进行拼接下。上面 msm_soc_info cpu_of_id[] 中枚举了相关芯片信息

static struct msm_soc_info cpu_of_id[] = {[0]  = {MSM_CPU_UNKNOWN, "Unknown CPU"},/* 8960 IDs */[87] = {MSM_CPU_8960, "MSM8960"},/* 8064 IDs */[109] = {MSM_CPU_8064, "APQ8064"},[122] = {MSM_CPU_8960, "MSM8960"},... ...

根据 socinfo->v0_1.id 进行匹配，这个 id 等于项目的 dtsi 中配置的 qcom,msm-id 

/ {model = "Qualcomm Technologies, Inc. xxx";compatible = "xxx";qcom,msm-id = <xxx 0x10000>, <xxx 0x10000>;

注意：

高Android版本，修改 cpu_of_id 可能会影响CTS testConfigHardwareMitigations 此项。相关源码cts/hostsidetests/security/src/android/security/cts/KernelConfigTest.java

    private Map<String, String[]> hardwareMitigations = new HashMap<String, String[]>() {{put("EXYNOS990", null);put("EXYNOS980", null);put("EXYNOS850", null);put("EXYNOS3830", null);put("EXYNOS9630", null);put("EXYNOS9830", null);put("EXYNOS7870", null);put("EXYNOS7880", null);put("EXYNOS7570", null);put("EXYNOS7872", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("EXYNOS7885", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("EXYNOS9610", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("Kirin980", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("Kirin970", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("Kirin810", null);put("Kirin710", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("SDMMAGPIE", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("SM6150", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("SM7150", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("LITO", null);put("SM8150", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("SM8150P", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("KONA", null);put("SDM429", null);put("SDM439", null);put("QM215", null);put("BENGAL", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y"});put("DEFAULT", new String[]{"CONFIG_HARDEN_BRANCH_PREDICTOR=y","CONFIG_UNMAP_KERNEL_AT_EL0=y"});}};private String[] lookupMitigations() throws Exception {return hardwareMitigations.get(getHardware());}/*** Test that the kernel has Spectre/Meltdown mitigations for architectures and kernel versions* that support it. Exempt platforms which are known to not be vulnerable.** @throws Exception*/@CddTest(requirement="9.7")public void testConfigHardwareMitigations() throws Exception {String mitigations[];if (PropertyUtil.getFirstApiLevel(mDevice) < 28) {return;}if (CpuFeatures.isArm64(mDevice) && !CpuFeatures.kernelVersionLessThan(mDevice, 4, 4)) {mitigations = lookupMitigations();if (mitigations != null) {for (String mitigation : mitigations) {assertTrue("Linux kernel must have " + mitigation + " enabled.",configSet.contains(mitigation));}}} else if (CpuFeatures.isX86(mDevice)) {assertTrue("Linux kernel must have KPTI enabled: CONFIG_PAGE_TABLE_ISOLATION=y",configSet.contains("CONFIG_PAGE_TABLE_ISOLATION=y"));}}

测试会根据 hardwareMitigations 中CPU型号，确认需要开启的宏，所以修改CPU名称后需要确认相关宏是否开启。