From 671b7c7b54fcab46b6e8bfc8c2d661fe55df0bf5 Mon Sep 17 00:00:00 2001
From: Jiajie Chen <noc@jiegec.ac.cn>
Date: Tue, 26 Feb 2019 23:59:18 +0800
Subject: [PATCH] Implement backtrace support for x86_64

---
 kernel/src/arch/x86_64/linker.ld |  2 ++
 kernel/src/backtrace.rs          | 26 +++++++++++++++++++++-----
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/kernel/src/arch/x86_64/linker.ld b/kernel/src/arch/x86_64/linker.ld
index a84b37d0..a03f48ec 100644
--- a/kernel/src/arch/x86_64/linker.ld
+++ b/kernel/src/arch/x86_64/linker.ld
@@ -13,7 +13,9 @@ SECTIONS {
 
   .text ALIGN(4K):
   {
+    stext = .;
     *(.text .text.*)
+    etext = .;
   }
 
   .data ALIGN(4K):
diff --git a/kernel/src/backtrace.rs b/kernel/src/backtrace.rs
index abf95fb5..3d569166 100644
--- a/kernel/src/backtrace.rs
+++ b/kernel/src/backtrace.rs
@@ -1,13 +1,13 @@
 use core::mem::size_of;
+use rcore_memory::PAGE_SIZE;
 
 extern "C" {
     fn stext();
     fn etext();
 }
 
-/// Returns the current frame pointer.
+/// Returns the current frame pointer.or stack base pointer
 #[inline(always)]
-#[cfg(any(target_arch = "aarch64", target_arch = "riscv32", target_arch = "riscv64"))]
 pub fn fp() -> usize {
     let ptr: usize;
     #[cfg(target_arch = "aarch64")]
@@ -18,13 +18,16 @@ pub fn fp() -> usize {
     unsafe {
         asm!("mv $0, s0" : "=r"(ptr));
     }
+    #[cfg(target_arch = "x86_64")]
+    unsafe {
+        asm!("mov %rbp, $0" : "=r"(ptr));
+    }
 
     ptr
 }
 
-/// Returns the current link register.
+/// Returns the current link register.or return address
 #[inline(always)]
-#[cfg(any(target_arch = "aarch64", target_arch = "riscv32", target_arch = "riscv64"))]
 pub fn lr() -> usize {
     let ptr: usize;
     #[cfg(target_arch = "aarch64")]
@@ -35,13 +38,16 @@ pub fn lr() -> usize {
     unsafe {
         asm!("mv $0, ra" : "=r"(ptr));
     }
+    #[cfg(target_arch = "x86_64")]
+    unsafe {
+        asm!("movq 8(%rbp), $0" : "=r"(ptr));
+    }
 
     ptr
 }
 
 // Print the backtrace starting from the caller
 pub fn backtrace() {
-    #[cfg(any(target_arch = "aarch64", target_arch = "riscv32", target_arch = "riscv64"))]
     unsafe {
         let mut current_pc = lr();
         let mut current_fp = fp();
@@ -61,6 +67,16 @@ pub fn backtrace() {
                     current_pc = *(current_fp as *const usize).offset(1);
                 }
             }
+            #[cfg(target_arch = "x86_64")]
+            {
+                // Kernel stack at 0x0000_57ac_0000_0000 (defined in bootloader crate)
+                // size = 512 pages
+                current_fp = *(current_fp as *const usize).offset(0);
+                if (current_fp >= 0x0000_57ac_0000_0000 + 512 * PAGE_SIZE - size_of::<usize>()) {
+                    break;
+                }
+                current_pc = *(current_fp as *const usize).offset(1);
+            }
         }
     }
 }