supervisor: Add an example on the HSM extension

The HSM extension from SBI v2.0 allows a supervisor to manage the state
of harts on the system. Moreover, it also guarantees that only one hart
makes it into the booting stages of the supervisor, and it's up to the
supervisor to wake up the rest through the HSM extension.

I have added an example which showcases this extension in different
ways, and it finally shuts down the machine.

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/arch/riscv/supervisor/hsm/hsm.ld.S b/arch/riscv/supervisor/hsm/hsm.ld.S
new file mode 100644
index 0000000..db83dc9
--- /dev/null
+++ b/arch/riscv/supervisor/hsm/hsm.ld.S
@@ -0,0 +1,48 @@
+#define PAGE_SIZE 0x1000
+#define STACK_SIZE PAGE_SIZE
+
+#define LOAD_BASE_ADDR 0x80000000
+#define LOAD_BASE_OFFSET 0x00200000
+#define LOAD_OFFSET (LOAD_BASE_ADDR + LOAD_BASE_OFFSET)
+
+OUTPUT_ARCH(riscv)
+ENTRY(_start)
+
+SECTIONS {
+	. = LOAD_OFFSET;
+	_start = .;
+	. = ALIGN(PAGE_SIZE);
+
+	.text : {
+		_text = .;
+		KEEP(*(.head.text))
+		. = ALIGN(PAGE_SIZE);
+    	*(.text)
+	}
+	. = ALIGN(PAGE_SIZE);
+
+	.data : {
+    	*(.data)
+	}
+	. = ALIGN(8);
+
+	.rodata : {
+    	*(.rodata)
+	}
+	. = ALIGN(8);
+
+	.sdata : {
+		*(.sdata*)
+	}
+	. = ALIGN(8);
+
+	.bss : {
+    	*(.bss)
+	}
+
+	. = ALIGN(8);
+	. = . + STACK_SIZE;
+	_STACK_PTR = .;
+
+	_end = .;
+}