lib: Fix CPU capabilities detection function

On some platforms, misa may not be implemented. On such a platform,
reading misa will get 0. At this time, platform is required to
implement a non-standard function to detect the CPU's capabilities.
Therefore, this modification add interfaces for non-standard function.

The MXL field of misa is always at the highest two bits, whether it
is a 32-bit 64-bit or a 128-bit machine. Therefore, this modification
fixes the use of a fixed offset to detect the machine length.

Signed-off-by: Xiang Wang <merle@hardenedlinux.org>
Signed-off-by: Anup Patel <anup.patel@wdc.com>

1 files changed, 6 insertions, 10 deletions

diff --git a/include/sbi/riscv_asm.h b/include/sbi/riscv_asm.h
index 4f12c03..04502e1 100644
--- a/include/sbi/riscv_asm.h
+++ b/include/sbi/riscv_asm.h
@@ -159,22 +159,18 @@ void csr_write_num(int csr_num, unsigned long val);
 		__asm__ __volatile__("wfi" ::: "memory"); \
 	} while (0)
 
-static inline int misa_extension(char ext)
-{
-	return csr_read(CSR_MISA) & (1 << (ext - 'A'));
-}
+/* Determine CPU extension, return non-zero support */
+int misa_extension(char ext);
 
-static inline int misa_xlen(void)
-{
-	return ((long)csr_read(CSR_MISA) < 0) ? 64 : 32;
-}
+/* Get MXL field of misa, return -1 on error */
+int misa_xlen(void);
 
 static inline void misa_string(char *out, unsigned int out_sz)
 {
-	unsigned long i, val = csr_read(CSR_MISA);
+	unsigned long i;
 
 	for (i = 0; i < 26; i++) {
-		if (val & (1 << i)) {
+		if (misa_extension('A' + i)) {
 			*out = 'A' + i;
 			out++;
 		}