diff options
| -rw-r--r-- | vm.c | 11 |
1 files changed, 8 insertions, 3 deletions
@@ -163,17 +163,22 @@ switchkvm(void) void switchuvm(struct proc *p) { + if(p == 0) + panic("switchuvm: no process"); + if(p->kstack == 0) + panic("switchuvm: no kstack"); + if(p->pgdir == 0) + panic("switchuvm: no pgdir"); + pushcli(); cpu->gdt[SEG_TSS] = SEG16(STS_T32A, &cpu->ts, sizeof(cpu->ts)-1, 0); cpu->gdt[SEG_TSS].s = 0; cpu->ts.ss0 = SEG_KDATA << 3; - cpu->ts.esp0 = (uint)proc->kstack + KSTACKSIZE; + cpu->ts.esp0 = (uint)p->kstack + KSTACKSIZE; // setting IOPL=0 in eflags *and* iomb beyond the tss segment limit // forbids I/O instructions (e.g., inb and outb) from user space cpu->ts.iomb = (ushort) 0xFFFF; ltr(SEG_TSS << 3); - if(p->pgdir == 0) - panic("switchuvm: no pgdir"); lcr3(V2P(p->pgdir)); // switch to process's address space popcli(); } |