[PATCH v2 3/8] xen/riscv: introduce stack stuff

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

The patch introduces and sets up a stack in order to go to C environment

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in V2:
    - introduce STACK_SIZE define.
    - use consistent padding between instruction mnemonic and operand(s)
---
 xen/arch/riscv/Makefile             | 1 +
 xen/arch/riscv/include/asm/config.h | 2 ++
 xen/arch/riscv/riscv64/head.S       | 8 +++++++-
 xen/arch/riscv/setup.c              | 6 ++++++
 4 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 xen/arch/riscv/setup.c

diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
index 248f2cbb3e..5a67a3f493 100644
--- a/xen/arch/riscv/Makefile
+++ b/xen/arch/riscv/Makefile
@@ -1,4 +1,5 @@
 obj-$(CONFIG_RISCV_64) += riscv64/
+obj-y += setup.o
 
 $(TARGET): $(TARGET)-syms
        $(OBJCOPY) -O binary -S $< $@
diff --git a/xen/arch/riscv/include/asm/config.h 
b/xen/arch/riscv/include/asm/config.h
index 0370f865f3..bdd2237f01 100644
--- a/xen/arch/riscv/include/asm/config.h
+++ b/xen/arch/riscv/include/asm/config.h
@@ -43,6 +43,8 @@
 
 #define SMP_CACHE_BYTES (1 << 6)
 
+#define STACK_SIZE (PAGE_SIZE)
+
 #endif /* __RISCV_CONFIG_H__ */
 /*
  * Local variables:
diff --git a/xen/arch/riscv/riscv64/head.S b/xen/arch/riscv/riscv64/head.S
index 990edb70a0..c1f33a1934 100644
--- a/xen/arch/riscv/riscv64/head.S
+++ b/xen/arch/riscv/riscv64/head.S
@@ -1,4 +1,10 @@
         .section .text.header, "ax", %progbits
 
 ENTRY(start)
-        j  start
+        la      sp, cpu0_boot_stack
+        li      t0, STACK_SIZE
+        add     sp, sp, t0
+
+_start_hang:
+        wfi
+        j       _start_hang
diff --git a/xen/arch/riscv/setup.c b/xen/arch/riscv/setup.c
new file mode 100644
index 0000000000..41ef4912bd
--- /dev/null
+++ b/xen/arch/riscv/setup.c
@@ -0,0 +1,6 @@
+#include <xen/init.h>
+#include <xen/compile.h>
+
+/* Xen stack for bringing up the first CPU. */
+unsigned char __initdata cpu0_boot_stack[STACK_SIZE]
+    __aligned(STACK_SIZE);
-- 
2.38.1