void __init riscv_fill_hwcap()

in kernel/cpufeature.c [62:151]

• 66 lines of code
• 17 McCabe index (conditional complexity)

void __init riscv_fill_hwcap(void)
{
	struct device_node *node;
	const char *isa;
	char print_str[BITS_PER_LONG + 1];
	size_t i, j, isa_len;
	static unsigned long isa2hwcap[256] = {0};

	isa2hwcap['i'] = isa2hwcap['I'] = COMPAT_HWCAP_ISA_I;
	isa2hwcap['m'] = isa2hwcap['M'] = COMPAT_HWCAP_ISA_M;
	isa2hwcap['a'] = isa2hwcap['A'] = COMPAT_HWCAP_ISA_A;
	isa2hwcap['f'] = isa2hwcap['F'] = COMPAT_HWCAP_ISA_F;
	isa2hwcap['d'] = isa2hwcap['D'] = COMPAT_HWCAP_ISA_D;
	isa2hwcap['c'] = isa2hwcap['C'] = COMPAT_HWCAP_ISA_C;

	elf_hwcap = 0;

	bitmap_zero(riscv_isa, RISCV_ISA_EXT_MAX);

	for_each_of_cpu_node(node) {
		unsigned long this_hwcap = 0;
		unsigned long this_isa = 0;

		if (riscv_of_processor_hartid(node) < 0)
			continue;

		if (of_property_read_string(node, "riscv,isa", &isa)) {
			pr_warn("Unable to find \"riscv,isa\" devicetree entry\n");
			continue;
		}

		i = 0;
		isa_len = strlen(isa);
#if IS_ENABLED(CONFIG_32BIT)
		if (!strncmp(isa, "rv32", 4))
			i += 4;
#elif IS_ENABLED(CONFIG_64BIT)
		if (!strncmp(isa, "rv64", 4))
			i += 4;
#endif
		for (; i < isa_len; ++i) {
			this_hwcap |= isa2hwcap[(unsigned char)(isa[i])];
			/*
			 * TODO: X, Y and Z extension parsing for Host ISA
			 * bitmap will be added in-future.
			 */
			if ('a' <= isa[i] && isa[i] < 'x')
				this_isa |= (1UL << (isa[i] - 'a'));
		}

		/*
		 * All "okay" hart should have same isa. Set HWCAP based on
		 * common capabilities of every "okay" hart, in case they don't
		 * have.
		 */
		if (elf_hwcap)
			elf_hwcap &= this_hwcap;
		else
			elf_hwcap = this_hwcap;

		if (riscv_isa[0])
			riscv_isa[0] &= this_isa;
		else
			riscv_isa[0] = this_isa;
	}

	/* We don't support systems with F but without D, so mask those out
	 * here. */
	if ((elf_hwcap & COMPAT_HWCAP_ISA_F) && !(elf_hwcap & COMPAT_HWCAP_ISA_D)) {
		pr_info("This kernel does not support systems with F but not D\n");
		elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
	}

	memset(print_str, 0, sizeof(print_str));
	for (i = 0, j = 0; i < BITS_PER_LONG; i++)
		if (riscv_isa[0] & BIT_MASK(i))
			print_str[j++] = (char)('a' + i);
	pr_info("riscv: ISA extensions %s\n", print_str);

	memset(print_str, 0, sizeof(print_str));
	for (i = 0, j = 0; i < BITS_PER_LONG; i++)
		if (elf_hwcap & BIT_MASK(i))
			print_str[j++] = (char)('a' + i);
	pr_info("riscv: ELF capabilities %s\n", print_str);

#ifdef CONFIG_FPU
	if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D))
		static_branch_enable(&cpu_hwcap_fpu);
#endif
}