Implement backtrace support for RISCV64

kernel/src/backtrace.rs

@@ -5,44 +5,60 @@ extern "C" {
 
 /// Returns the current frame pointer.
 #[inline(always)]
-#[cfg(target_arch = "aarch64")]
+#[cfg(any(target_arch = "aarch64", target_arch = "riscv64"))]
 pub fn fp() -> usize {
     let ptr: usize;
+    #[cfg(target_arch = "aarch64")]
     unsafe {
         asm!("mov $0, x29" : "=r"(ptr));
     }
+    #[cfg(target_arch = "riscv64")]
+    unsafe {
+        asm!("mv $0, s0" : "=r"(ptr));
+    }
 
     ptr
 }
 
 /// Returns the current link register.
 #[inline(always)]
-#[cfg(target_arch = "aarch64")]
+#[cfg(any(target_arch = "aarch64", target_arch = "riscv64"))]
 pub fn lr() -> usize {
     let ptr: usize;
+    #[cfg(target_arch = "aarch64")]
     unsafe {
         asm!("mov $0, x30" : "=r"(ptr));
     }
+    #[cfg(target_arch = "riscv64")]
+    unsafe {
+        asm!("mv $0, ra" : "=r"(ptr));
+    }
 
     ptr
 }
 
 // Print the backtrace starting from the caller
 pub fn backtrace() {
-    #[cfg(target_arch = "aarch64")]
+    #[cfg(any(target_arch = "aarch64", target_arch = "riscv64"))]
     unsafe {
         let mut current_pc = lr();
         let mut current_fp = fp();
         let mut stack_num = 0;
-        println!("pc {:#018X} fp {:#018X}", current_pc, current_fp);
         while current_pc >= stext as usize && current_pc <= etext as usize && current_fp as usize != 0 {
-            println!("#{} {:#018X}", stack_num, current_pc);
+            println!("#{} {:#018X} fp {:#18X}", stack_num, current_pc - 4, current_fp);
             stack_num = stack_num + 1;
-            current_fp = *(current_fp as *const usize);
+            #[cfg(target_arch = "riscv64")]
-            if current_fp as usize != 0 {
+            {
-                current_pc = *(current_fp as *const usize).offset(1);
+                current_fp = *((current_fp - 16) as *const usize);
+                current_pc = *(current_fp as *const usize).offset(-1);
+            }
+            #[cfg(target_arch = "aarch64")]
+            {
+                current_fp = *(current_fp as *const usize);
+                if current_fp != 0 {
+                    current_pc = *(current_fp as *const usize).offset(1);
+                }
             }
-            println!("pc {:#018X} fp {:#018X}", current_pc, current_fp);
         }
     }
 }

kernel/targets/riscv64.json

@@ -31,5 +31,6 @@
     "ptx-kernel",
     "msp430-interrupt",
     "x86-interrupt"
-  ]
+  ],
+  "eliminate-frame-pointer": false
 }