Kernel/riscv64: Add support for SRST "System Reset" SBI extension

This extension will be used for rebooting and shutting down.

Kernel/Arch/riscv64/SBI.cpp

@@ -44,6 +44,22 @@ static SBIErrorOr<long> sbi_ecall1(EID extension_id, u32 function_id, unsigned l
     return static_cast<SBIError>(a0);
 }
 
+static SBIErrorOr<long> sbi_ecall2(EID extension_id, u32 function_id, unsigned long arg0, unsigned long arg1)
+{
+    register unsigned long a0 asm("a0") = arg0;
+    register unsigned long a1 asm("a1") = arg1;
+    register unsigned long a6 asm("a6") = function_id;
+    register unsigned long a7 asm("a7") = to_underlying(extension_id);
+    asm volatile("ecall"
+                 : "+r"(a0), "+r"(a1)
+                 : "r"(a0), "r"(a1), "r"(a6), "r"(a7)
+                 : "memory");
+    if (a0 == to_underlying(SBIError::Success))
+        return static_cast<long>(a1);
+
+    return static_cast<SBIError>(a0);
+}
+
 namespace Base {
 
 SBIErrorOr<SpecificationVersion> get_spec_version()
@@ -145,6 +161,20 @@ SBIErrorOr<void> set_timer(u64 stime_value)
 
 }
 
+namespace SystemReset {
+
+SBIError system_reset(ResetType reset_type, ResetReason reset_reason)
+{
+    auto const res = SBI::sbi_ecall2(EID::SystemReset, to_underlying(FID::SystemReset), to_underlying(reset_type), to_underlying(reset_reason));
+
+    // This SBI call shold only return if it didn't succeed
+    VERIFY(res.is_error());
+
+    return res.error();
+}
+
+}
+
 namespace DBCN {
 
 SBIErrorOr<void> debug_console_write_byte(u8 byte)

Kernel/Arch/riscv64/SBI.h

@@ -46,6 +46,8 @@ enum class EID : i32 {
     Base = 0x10,
     // Debug Console Extension ("DBCN")
     DebugConsole = 0x4442434E,
+    // System Reset Extension ("SRST")
+    SystemReset = 0x53525354,
     // Timer Extension ("TIME")
     Timer = 0x54494D45,
 };
@@ -155,6 +157,32 @@ SBIErrorOr<void> set_timer(u64 stime_value);
 
 }
 
+// Chapter 10. System Reset Extension (EID #0x53525354 "SRST")
+// Since SBI v0.2
+namespace SystemReset {
+
+enum class FID : i32 {
+    SystemReset = 0,
+};
+
+enum class ResetType : u32 {
+    Shutdown = 0x0,
+    ColdReboot = 0x1,
+    WarmReboot = 0x2,
+};
+
+enum class ResetReason : u32 {
+    NoReason = 0x0,
+    SystemFailure = 0x1,
+};
+
+// System reset (FID #0)
+// Reset the system based on provided reset_type and reset_reason. This is a synchronous call and
+// does not return if it succeeds.
+SBIError system_reset(ResetType reset_type, ResetReason reset_reason);
+
+}
+
 // Chapter 12. Debug Console Extension (EID #0x4442434E "DBCN")
 // Since SBI v2.0
 namespace DBCN {