RISC-V: Add a syscall for HW probing

We don't have enough space for these all in ELF_HWCAP{,2} and there's no
system call that quite does this, so let's just provide an arch-specific
one to probe for hardware capabilities.  This currently just provides
m{arch,imp,vendor}id, but with the key-value pairs we can pass more in
the future.

Co-developed-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Evan Green <evan@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Tested-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Reviewed-by: Paul Walmsley <paul.walmsley@sifive.com>
Link: https://lore.kernel.org/r/20230407231103.2622178-3-evan@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
new file mode 100644
index 000000000000..b79be00920db
--- /dev/null
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Copyright 2023 Rivos, Inc
+ */
+
+#ifndef _UAPI_ASM_HWPROBE_H
+#define _UAPI_ASM_HWPROBE_H
+
+#include <linux/types.h>
+
+/*
+ * Interface for probing hardware capabilities from userspace, see
+ * Documentation/riscv/hwprobe.rst for more information.
+ */
+struct riscv_hwprobe {
+	__s64 key;
+	__u64 value;
+};
+
+#define RISCV_HWPROBE_KEY_MVENDORID	0
+#define RISCV_HWPROBE_KEY_MARCHID	1
+#define RISCV_HWPROBE_KEY_MIMPID	2
+/* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
+
+#endif