![Richard Weinberger](/assets/img/avatar_default.png)
As UML uses an alternative signal stack we cannot use the current stack pointer for stack dumping if UML itself dies by SIGSEGV. To bypass this issue we save regs taken from mcontext in our segv handler into thread_struct and use these regs to obtain the stack pointer in show_stack(). Signed-off-by: Richard Weinberger <richard@nod.at>
331 lines
7.7 KiB
C
331 lines
7.7 KiB
C
/*
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* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
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* Licensed under the GPL
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*/
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/hardirq.h>
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#include <linux/module.h>
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#include <asm/current.h>
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#include <asm/pgtable.h>
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#include <asm/tlbflush.h>
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#include <arch.h>
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#include <as-layout.h>
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#include <kern_util.h>
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#include <os.h>
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#include <skas.h>
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/*
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* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by
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* segv().
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*/
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int handle_page_fault(unsigned long address, unsigned long ip,
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int is_write, int is_user, int *code_out)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte;
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int err = -EFAULT;
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unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
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*code_out = SEGV_MAPERR;
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/*
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* If the fault was during atomic operation, don't take the fault, just
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* fail.
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*/
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if (in_atomic())
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goto out_nosemaphore;
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if (is_user)
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flags |= FAULT_FLAG_USER;
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retry:
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down_read(&mm->mmap_sem);
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vma = find_vma(mm, address);
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if (!vma)
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goto out;
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else if (vma->vm_start <= address)
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goto good_area;
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else if (!(vma->vm_flags & VM_GROWSDOWN))
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goto out;
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else if (is_user && !ARCH_IS_STACKGROW(address))
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goto out;
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else if (expand_stack(vma, address))
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goto out;
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good_area:
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*code_out = SEGV_ACCERR;
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if (is_write) {
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if (!(vma->vm_flags & VM_WRITE))
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goto out;
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flags |= FAULT_FLAG_WRITE;
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} else {
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/* Don't require VM_READ|VM_EXEC for write faults! */
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if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
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goto out;
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}
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do {
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int fault;
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fault = handle_mm_fault(mm, vma, address, flags);
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if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
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goto out_nosemaphore;
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if (unlikely(fault & VM_FAULT_ERROR)) {
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if (fault & VM_FAULT_OOM) {
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goto out_of_memory;
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} else if (fault & VM_FAULT_SIGBUS) {
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err = -EACCES;
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goto out;
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}
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BUG();
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}
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if (flags & FAULT_FLAG_ALLOW_RETRY) {
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if (fault & VM_FAULT_MAJOR)
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current->maj_flt++;
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else
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current->min_flt++;
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if (fault & VM_FAULT_RETRY) {
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flags &= ~FAULT_FLAG_ALLOW_RETRY;
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flags |= FAULT_FLAG_TRIED;
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goto retry;
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}
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}
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pgd = pgd_offset(mm, address);
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pud = pud_offset(pgd, address);
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pmd = pmd_offset(pud, address);
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pte = pte_offset_kernel(pmd, address);
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} while (!pte_present(*pte));
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err = 0;
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/*
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* The below warning was added in place of
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* pte_mkyoung(); if (is_write) pte_mkdirty();
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* If it's triggered, we'd see normally a hang here (a clean pte is
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* marked read-only to emulate the dirty bit).
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* However, the generic code can mark a PTE writable but clean on a
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* concurrent read fault, triggering this harmlessly. So comment it out.
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*/
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#if 0
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WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
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#endif
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flush_tlb_page(vma, address);
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out:
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up_read(&mm->mmap_sem);
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out_nosemaphore:
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return err;
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out_of_memory:
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/*
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* We ran out of memory, call the OOM killer, and return the userspace
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* (which will retry the fault, or kill us if we got oom-killed).
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*/
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up_read(&mm->mmap_sem);
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if (!is_user)
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goto out_nosemaphore;
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pagefault_out_of_memory();
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return 0;
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}
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EXPORT_SYMBOL(handle_page_fault);
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static void show_segv_info(struct uml_pt_regs *regs)
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{
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struct task_struct *tsk = current;
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struct faultinfo *fi = UPT_FAULTINFO(regs);
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if (!unhandled_signal(tsk, SIGSEGV))
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return;
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if (!printk_ratelimit())
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return;
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printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x",
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task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
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tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
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(void *)UPT_IP(regs), (void *)UPT_SP(regs),
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fi->error_code);
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print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
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printk(KERN_CONT "\n");
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}
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static void bad_segv(struct faultinfo fi, unsigned long ip)
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{
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struct siginfo si;
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si.si_signo = SIGSEGV;
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si.si_code = SEGV_ACCERR;
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si.si_addr = (void __user *) FAULT_ADDRESS(fi);
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current->thread.arch.faultinfo = fi;
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force_sig_info(SIGSEGV, &si, current);
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}
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void fatal_sigsegv(void)
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{
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force_sigsegv(SIGSEGV, current);
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do_signal();
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/*
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* This is to tell gcc that we're not returning - do_signal
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* can, in general, return, but in this case, it's not, since
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* we just got a fatal SIGSEGV queued.
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*/
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os_dump_core();
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}
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void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
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{
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struct faultinfo * fi = UPT_FAULTINFO(regs);
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if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
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show_segv_info(regs);
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bad_segv(*fi, UPT_IP(regs));
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return;
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}
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segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
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}
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/*
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* We give a *copy* of the faultinfo in the regs to segv.
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* This must be done, since nesting SEGVs could overwrite
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* the info in the regs. A pointer to the info then would
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* give us bad data!
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*/
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unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
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struct uml_pt_regs *regs)
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{
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struct siginfo si;
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jmp_buf *catcher;
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int err;
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int is_write = FAULT_WRITE(fi);
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unsigned long address = FAULT_ADDRESS(fi);
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if (regs)
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current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
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if (!is_user && (address >= start_vm) && (address < end_vm)) {
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flush_tlb_kernel_vm();
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goto out;
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}
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else if (current->mm == NULL) {
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show_regs(container_of(regs, struct pt_regs, regs));
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panic("Segfault with no mm");
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}
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if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
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err = handle_page_fault(address, ip, is_write, is_user,
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&si.si_code);
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else {
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err = -EFAULT;
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/*
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* A thread accessed NULL, we get a fault, but CR2 is invalid.
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* This code is used in __do_copy_from_user() of TT mode.
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* XXX tt mode is gone, so maybe this isn't needed any more
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*/
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address = 0;
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}
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catcher = current->thread.fault_catcher;
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if (!err)
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goto out;
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else if (catcher != NULL) {
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current->thread.fault_addr = (void *) address;
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UML_LONGJMP(catcher, 1);
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}
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else if (current->thread.fault_addr != NULL)
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panic("fault_addr set but no fault catcher");
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else if (!is_user && arch_fixup(ip, regs))
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goto out;
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if (!is_user) {
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show_regs(container_of(regs, struct pt_regs, regs));
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panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
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address, ip);
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}
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show_segv_info(regs);
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if (err == -EACCES) {
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si.si_signo = SIGBUS;
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si.si_errno = 0;
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si.si_code = BUS_ADRERR;
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si.si_addr = (void __user *)address;
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current->thread.arch.faultinfo = fi;
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force_sig_info(SIGBUS, &si, current);
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} else {
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BUG_ON(err != -EFAULT);
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si.si_signo = SIGSEGV;
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si.si_addr = (void __user *) address;
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current->thread.arch.faultinfo = fi;
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force_sig_info(SIGSEGV, &si, current);
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}
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out:
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if (regs)
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current->thread.segv_regs = NULL;
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return 0;
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}
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void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
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{
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struct faultinfo *fi;
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struct siginfo clean_si;
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if (!UPT_IS_USER(regs)) {
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if (sig == SIGBUS)
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printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
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"mount likely just ran out of space\n");
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panic("Kernel mode signal %d", sig);
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}
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arch_examine_signal(sig, regs);
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memset(&clean_si, 0, sizeof(clean_si));
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clean_si.si_signo = si->si_signo;
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clean_si.si_errno = si->si_errno;
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clean_si.si_code = si->si_code;
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switch (sig) {
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case SIGILL:
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case SIGFPE:
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case SIGSEGV:
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case SIGBUS:
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case SIGTRAP:
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fi = UPT_FAULTINFO(regs);
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clean_si.si_addr = (void __user *) FAULT_ADDRESS(*fi);
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current->thread.arch.faultinfo = *fi;
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#ifdef __ARCH_SI_TRAPNO
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clean_si.si_trapno = si->si_trapno;
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#endif
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break;
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default:
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printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d)\n",
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sig, si->si_code);
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}
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force_sig_info(sig, &clean_si, current);
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}
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void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
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{
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if (current->thread.fault_catcher != NULL)
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UML_LONGJMP(current->thread.fault_catcher, 1);
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else
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relay_signal(sig, si, regs);
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}
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void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
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{
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do_IRQ(WINCH_IRQ, regs);
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}
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void trap_init(void)
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{
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}
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