Merge branch 'riscv' into riscv

1 files changed, 18 insertions, 11 deletions

diff --git a/kernel/trap.c b/kernel/trap.c
index ca732f2..a63249e 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -48,7 +48,7 @@ usertrap(void)
   struct proc *p = myproc();
   
   // save user program counter.
-  p->tf->epc = r_sepc();
+  p->trapframe->epc = r_sepc();
   
   if(r_scause() == 8){
     // system call
@@ -58,7 +58,7 @@ usertrap(void)
 
     // sepc points to the ecall instruction,
     // but we want to return to the next instruction.
-    p->tf->epc += 4;
+    p->trapframe->epc += 4;
 
     // an interrupt will change sstatus &c registers,
     // so don't enable until done with those registers.
@@ -91,8 +91,9 @@ usertrapret(void)
 {
   struct proc *p = myproc();
 
-  // turn off interrupts, since we're switching
-  // now from kerneltrap() to usertrap().
+  // we're about to switch the destination of traps from
+  // kerneltrap() to usertrap(), so turn off interrupts until
+  // we're back in user space, where usertrap() is correct.
   intr_off();
 
   // send syscalls, interrupts, and exceptions to trampoline.S
@@ -100,10 +101,10 @@ usertrapret(void)
 
   // set up trapframe values that uservec will need when
   // the process next re-enters the kernel.
-  p->tf->kernel_satp = r_satp();         // kernel page table
-  p->tf->kernel_sp = p->kstack + PGSIZE; // process's kernel stack
-  p->tf->kernel_trap = (uint64)usertrap;
-  p->tf->kernel_hartid = r_tp();         // hartid for cpuid()
+  p->trapframe->kernel_satp = r_satp();         // kernel page table
+  p->trapframe->kernel_sp = p->kstack + PGSIZE; // process's kernel stack
+  p->trapframe->kernel_trap = (uint64)usertrap;
+  p->trapframe->kernel_hartid = r_tp();         // hartid for cpuid()
 
   // set up the registers that trampoline.S's sret will use
   // to get to user space.
@@ -115,7 +116,7 @@ usertrapret(void)
   w_sstatus(x);
 
   // set S Exception Program Counter to the saved user pc.
-  w_sepc(p->tf->epc);
+  w_sepc(p->trapframe->epc);
 
   // tell trampoline.S the user page table to switch to.
   uint64 satp = MAKE_SATP(p->pagetable);
@@ -129,7 +130,6 @@ usertrapret(void)
 
 // interrupts and exceptions from kernel code go here via kernelvec,
 // on whatever the current kernel stack is.
-// must be 4-byte aligned to fit in stvec.
 void 
 kerneltrap()
 {
@@ -189,9 +189,16 @@ devintr()
       uartintr();
     } else if(irq == VIRTIO0_IRQ){
       virtio_disk_intr();
+    } else if(irq){
+      printf("unexpected interrupt irq=%d\n", irq);
     }
 
-    plic_complete(irq);
+    // the PLIC allows each device to raise at most one
+    // interrupt at a time; tell the PLIC the device is
+    // now allowed to interrupt again.
+    if(irq)
+      plic_complete(irq);
+
     return 1;
   } else if(scause == 0x8000000000000001L){
     // software interrupt from a machine-mode timer interrupt,