Implement backtrace support for AArch64

kernel/src/backtrace.rs

@@ -0,0 +1,48 @@
+extern "C" {
+    fn stext();
+    fn etext();
+}
+
+/// Returns the current frame pointer.
+#[inline(always)]
+#[cfg(target_arch = "aarch64")]
+pub fn fp() -> usize {
+    let ptr: usize;
+    unsafe {
+        asm!("mov $0, x29" : "=r"(ptr));
+    }
+
+    ptr
+}
+
+/// Returns the current link register.
+#[inline(always)]
+#[cfg(target_arch = "aarch64")]
+pub fn lr() -> usize {
+    let ptr: usize;
+    unsafe {
+        asm!("mov $0, x30" : "=r"(ptr));
+    }
+
+    ptr
+}
+
+// Print the backtrace starting from the caller
+pub fn backtrace() {
+    #[cfg(target_arch = "aarch64")]
+    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);
+            stack_num = stack_num + 1;
+            current_fp = *(current_fp as *const usize);
+            if current_fp as usize != 0 {
+                current_pc = *(current_fp as *const usize).offset(1);
+            }
+            println!("pc {:#018X} fp {:#018X}", current_pc, current_fp);
+        }
+    }
+}

kernel/src/lang.rs

@@ -3,6 +3,7 @@
 use core::panic::PanicInfo;
 use core::alloc::Layout;
 use log::*;
+use crate::backtrace;
 
 #[lang = "eh_personality"] 
 extern fn eh_personality() {
@@ -13,6 +14,7 @@ fn panic(info: &PanicInfo) -> ! {
     let location = info.location().unwrap();
     let message = info.message().unwrap();
     error!("\n\nPANIC in {} at line {}\n    {}", location.file(), location.line(), message);
+    backtrace::backtrace();
     loop { crate::arch::cpu::halt() }
 }
 

kernel/src/lib.rs

@@ -28,6 +28,7 @@ mod fs;
 mod sync;
 mod trap;
 mod shell;
+mod backtrace;
 
 #[allow(dead_code)]
 #[cfg(target_arch = "x86_64")]

kernel/targets/aarch64.json

@@ -31,5 +31,6 @@
   "target-endian": "little",
   "target-pointer-width": "64",
   "target-family": "unix",
-  "disable-redzone": true
+  "disable-redzone": true,
+  "eliminate-frame-pointer": false
 }