[riscv] Add support for the RISC-V CPU architecture

Add support for building iPXE as a 64-bit or 32-bit RISC-V binary, for
either UEFI or Linux userspace platforms.  For example:

  # RISC-V 64-bit UEFI
  make CROSS=riscv64-linux-gnu- bin-riscv64-efi/ipxe.efi

  # RISC-V 32-bit UEFI
  make CROSS=riscv64-linux-gnu- bin-riscv32-efi/ipxe.efi

  # RISC-V 64-bit Linux
  make CROSS=riscv64-linux-gnu- bin-riscv64-linux/tests.linux
  qemu-riscv64 -L /usr/riscv64-linux-gnu/sys-root \
               ./bin-riscv64-linux/tests.linux

  # RISC-V 32-bit Linux
  make CROSS=riscv64-linux-gnu- SYSROOT=/usr/riscv32-linux-gnu/sys-root \
       bin-riscv32-linux/tests.linux
  qemu-riscv32 -L /usr/riscv32-linux-gnu/sys-root \
               ./bin-riscv32-linux/tests.linux

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 89 insertions, 0 deletions

diff --git a/src/arch/riscv/include/bits/string.h b/src/arch/riscv/include/bits/string.h
new file mode 100644
index 000000000..3f78b351d
--- /dev/null
+++ b/src/arch/riscv/include/bits/string.h
@@ -0,0 +1,89 @@
+#ifndef _BITS_STRING_H
+#define _BITS_STRING_H
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * String functions
+ *
+ */
+
+extern void riscv_bzero ( void *dest, size_t len );
+extern void riscv_memset ( void *dest, size_t len, int character );
+extern void riscv_memcpy ( void *dest, const void *src, size_t len );
+extern void riscv_memmove_forwards ( void *dest, const void *src, size_t len );
+extern void riscv_memmove_backwards ( void *dest, const void *src, size_t len );
+extern void riscv_memmove ( void *dest, const void *src, size_t len );
+
+/**
+ * Fill memory region
+ *
+ * @v dest		Destination region
+ * @v character		Fill character
+ * @v len		Length
+ * @ret dest		Destination region
+ */
+static inline __attribute__ (( always_inline )) void *
+memset ( void *dest, int character, size_t len ) {
+
+	/* For zeroing larger or non-constant lengths, use the
+	 * optimised variable-length zeroing code.
+	 */
+	if ( __builtin_constant_p ( character ) && ( character == 0 ) ) {
+		riscv_bzero ( dest, len );
+		return dest;
+	}
+
+	/* Not necessarily zeroing: use basic variable-length code */
+	riscv_memset ( dest, len, character );
+	return dest;
+}
+
+/**
+ * Copy memory region
+ *
+ * @v dest		Destination region
+ * @v src		Source region
+ * @v len		Length
+ * @ret dest		Destination region
+ */
+static inline __attribute__ (( always_inline )) void *
+memcpy ( void *dest, const void *src, size_t len ) {
+
+	/* Otherwise, use variable-length code */
+	riscv_memcpy ( dest, src, len );
+	return dest;
+}
+
+/**
+ * Copy (possibly overlapping) memory region
+ *
+ * @v dest		Destination region
+ * @v src		Source region
+ * @v len		Length
+ * @ret dest		Destination region
+ */
+static inline __attribute__ (( always_inline )) void *
+memmove ( void *dest, const void *src, size_t len ) {
+	ssize_t offset = ( dest - src );
+
+	/* If required direction of copy is known at build time, then
+	 * use the appropriate forwards/backwards copy directly.
+	 */
+	if ( __builtin_constant_p ( offset ) ) {
+		if ( offset <= 0 ) {
+			riscv_memmove_forwards ( dest, src, len );
+			return dest;
+		} else {
+			riscv_memmove_backwards ( dest, src, len );
+			return dest;
+		}
+	}
+
+	/* Otherwise, use ambidirectional copy */
+	riscv_memmove ( dest, src, len );
+	return dest;
+}
+
+#endif /* _BITS_STRING_H */