From 71bca532c568106a25a16154d83a5819ad314592 Mon Sep 17 00:00:00 2001
From: andy <1414772332@qq.com>
Date: Sat, 29 Mar 2025 13:01:18 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20entry.S=20=E6=96=87?=
 =?UTF-8?q?=E4=BB=B6=E7=9A=84=E4=B8=80=E4=BA=9B=E6=B3=A8=E9=87=8A?=
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---
 startup/riscv3/src/entry.S | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/startup/riscv3/src/entry.S b/startup/riscv3/src/entry.S
index 46d1a23..653868a 100755
--- a/startup/riscv3/src/entry.S
+++ b/startup/riscv3/src/entry.S
@@ -218,9 +218,12 @@ interrupt:
 .global entry_mip
 .global entry_mcause
 
+
+// cpu产生异常时会自动进入这个入口
 trap_entry:
 
     /* Interrupt trap */
+    // 把t0的值暂时保存到临时寄存器中
     csrw    mscratch, t0
     /* 保存mcause && mip 到pmpaddr中 */
     csrr    t0, mcause
@@ -228,11 +231,15 @@ trap_entry:
     csrr    t0, mip
     csrw    pmpaddr15, t0
 
+    // 在线程栈中直接处理中断
     andi    t0, t0, -1912 // -1912 = 0x888
+    // bnez不会更新返回地址 jal x1 会把返回地址更新到ra
     bnez    t0, interrupt
 
     /* System call and other traps */
+    // 把mscratch的值拷贝到t0中 然后把sp的值写入到mscratch
     csrrw   t0, mscratch, sp
+    // 切到异常处理栈
     la      sp, _trap_sp
 #ifndef __riscv_float_abi_soft
     addi    sp, sp, -REGBYTES*64