OpenSBI RISC-V ISA 扩展检测与支持方式分析

/* lib/sbi/sbi_init.c:152 */

static void sbi_boot_print_hart(struct sbi_scratch *scratch, u32 hartid)
{
	int xlen;
	char str[128];
	const struct sbi_domain *dom = sbi_domain_thishart_ptr();

	if (scratch->options & SBI_SCRATCH_NO_BOOT_PRINTS)
		return;

	/* Determine MISA XLEN and MISA string */
	xlen = misa_xlen();
	if (xlen < 1) {
		sbi_printf("Error %d getting MISA XLEN\n", xlen);
		sbi_hart_hang();
	}

	/* Boot HART details */
	sbi_printf("Boot HART ID              : %u\n", hartid);
	sbi_printf("Boot HART Domain          : %s\n", dom->name);
	sbi_hart_get_priv_version_str(scratch, str, sizeof(str));
	sbi_printf("Boot HART Priv Version    : %s\n", str);
	misa_string(xlen, str, sizeof(str));
	sbi_printf("Boot HART Base ISA        : %s\n", str);
	sbi_hart_get_extensions_str(scratch, str, sizeof(str));
	sbi_printf("Boot HART ISA Extensions  : %s\n", str);
	sbi_printf("Boot HART PMP Count       : %d\n",
		   sbi_hart_pmp_count(scratch));
	sbi_printf("Boot HART PMP Granularity : %lu\n",
		   sbi_hart_pmp_granularity(scratch));
	sbi_printf("Boot HART PMP Address Bits: %d\n",
		   sbi_hart_pmp_addrbits(scratch));
	sbi_printf("Boot HART MHPM Count      : %d\n",
		   sbi_hart_mhpm_count(scratch));
	sbi_hart_delegation_dump(scratch, "Boot HART ", "         ");
}

/* lib/sbi/riscv_asm.c:53 */

void misa_string(int xlen, char *out, unsigned int out_sz)
{
	unsigned int i, pos = 0;
	const char valid_isa_order[] = "iemafdqclbjtpvnhkorwxyzg";

	if (!out)
		return;

	if (5 <= (out_sz - pos)) {
		out[pos++] = 'r';
		out[pos++] = 'v';
		switch (xlen) {
		case 1:
			out[pos++] = '3';
			out[pos++] = '2';
			break;
		case 2:
			out[pos++] = '6';
			out[pos++] = '4';
			break;
		case 3:
			out[pos++] = '1';
			out[pos++] = '2';
			out[pos++] = '8';
			break;
		default:
			sbi_panic("%s: Unknown misa.MXL encoding %d",
				   __func__, xlen);
			return;
		}
	}

	for (i = 0; i < array_size(valid_isa_order) && (pos < out_sz); i++) {
		if (misa_extension_imp(valid_isa_order[i]))
			out[pos++] = valid_isa_order[i];
	}

	if (pos < out_sz)
		out[pos++] = '\0';
}

/* lib/sbi/riscv_asm.c:16 */

/* determine CPU extension, return non-zero support */
int misa_extension_imp(char ext)
{
	unsigned long misa = csr_read(CSR_MISA);

	if (misa) {
		if ('A' <= ext && ext <= 'Z')
			return misa & (1 << (ext - 'A'));
		if ('a' <= ext && ext <= 'z')
			return misa & (1 << (ext - 'a'));
		return 0;
	}

	return sbi_platform_misa_extension(sbi_platform_thishart_ptr(), ext);
}

/* include/sbi/sbi_platform.h:461 */

/**
 * Check CPU extension in MISA
 *
 * @param plat pointer to struct sbi_platform
 * @param ext shorthand letter for CPU extensions
 *
 * @return zero for not-supported and non-zero for supported
 */
static inline int sbi_platform_misa_extension(const struct sbi_platform *plat,
					      char ext)
{
	if (plat && sbi_platform_ops(plat)->misa_check_extension)
		return sbi_platform_ops(plat)->misa_check_extension(ext);
	return 0;
}

/* lib/sbi/sbi_hart.c:463 */

/**
 * Get the hart extensions in string format
 *
 * @param scratch pointer to the HART scratch space
 * @param extensions_str pointer to a char array where the extensions string
 *			 will be updated
 * @param nestr length of the features_str. The feature string will be
 *		truncated if nestr is not long enough.
 */
void sbi_hart_get_extensions_str(struct sbi_scratch *scratch,
				 char *extensions_str, int nestr)
{
	struct sbi_hart_features *hfeatures =
			sbi_scratch_offset_ptr(scratch, hart_features_offset);
	int offset = 0, ext = 0;
	char *temp;

	if (!extensions_str || nestr <= 0)
		return;
	sbi_memset(extensions_str, 0, nestr);

	if (!hfeatures->extensions)
		goto done;

	do {
		if (hfeatures->extensions & BIT(ext)) {
			temp = sbi_hart_extension_id2string(ext);
			if (temp) {
				sbi_snprintf(extensions_str + offset,
					     nestr - offset,
					     "%s,", temp);
				offset = offset + sbi_strlen(temp) + 1;
			}
		}

		ext++;
	} while (ext < SBI_HART_EXT_MAX);

done:
	if (offset)
		extensions_str[offset - 1] = '\0';
	else
		sbi_strncpy(extensions_str, "none", nestr);
}

/* include/sbi/sbi_hart.h:27 */

/** Possible ISA extensions of a hart */
enum sbi_hart_extensions {
	/** Hart has Sscofpmt extension */
	SBI_HART_EXT_SSCOFPMF = 0,
	/** HART has HW time CSR (extension name not available) */
	SBI_HART_EXT_TIME,
	/** HART has AIA M-mode CSRs */
	SBI_HART_EXT_SMAIA,
	/** HART has Smstateen CSR **/
	SBI_HART_EXT_SMSTATEEN,
	/** HART has Sstc extension */
	SBI_HART_EXT_SSTC,

	/** Maximum index of Hart extension */
	SBI_HART_EXT_MAX,
};

/* include/sbi/sbi_hart.h:27 */

/** Possible ISA extensions of a hart */
enum sbi_hart_extensions {
	/** HART has AIA M-mode CSRs */
	SBI_HART_EXT_SMAIA = 0,
	/** HART has Smepmp */
	SBI_HART_EXT_SMEPMP,
	/** HART has Smstateen CSR **/
	SBI_HART_EXT_SMSTATEEN,
	/** Hart has Sscofpmt extension */
	SBI_HART_EXT_SSCOFPMF,
	/** HART has Sstc extension */
	SBI_HART_EXT_SSTC,
	/** HART has Zicntr extension (i.e. HW cycle, time & instret CSRs) */
	SBI_HART_EXT_ZICNTR,
	/** HART has Zihpm extension */
	SBI_HART_EXT_ZIHPM,
	/** Hart has Smcntrpmf extension */
	SBI_HART_EXT_SMCNTRPMF,

	/** Maximum index of Hart extension */
	SBI_HART_EXT_MAX,
};