adopt github PR98 (No need to store TRAPFRAME in sscratch register)

1 files changed, 6 insertions, 5 deletions

diff --git a/kernel/trap.c b/kernel/trap.c
index a63249e..75fb3ec 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -96,8 +96,9 @@ usertrapret(void)
   // we're back in user space, where usertrap() is correct.
   intr_off();
 
-  // send syscalls, interrupts, and exceptions to trampoline.S
-  w_stvec(TRAMPOLINE + (uservec - trampoline));
+  // send syscalls, interrupts, and exceptions to uservec in trampoline.S
+  uint64 trampoline_uservec = TRAMPOLINE + (uservec - trampoline);
+  w_stvec(trampoline_uservec);
 
   // set up trapframe values that uservec will need when
   // the process next re-enters the kernel.
@@ -121,11 +122,11 @@ usertrapret(void)
   // tell trampoline.S the user page table to switch to.
   uint64 satp = MAKE_SATP(p->pagetable);
 
-  // jump to trampoline.S at the top of memory, which 
+  // jump to userret in trampoline.S at the top of memory, which 
   // switches to the user page table, restores user registers,
   // and switches to user mode with sret.
-  uint64 fn = TRAMPOLINE + (userret - trampoline);
-  ((void (*)(uint64,uint64))fn)(TRAPFRAME, satp);
+  uint64 trampoline_userret = TRAMPOLINE + (userret - trampoline);
+  ((void (*)(uint64))trampoline_userret)(satp);
 }
 
 // interrupts and exceptions from kernel code go here via kernelvec,