316 lines
7.9 KiB
C
316 lines
7.9 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
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*/
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#include <linux/mm.h>
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#include <linux/sched/signal.h>
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#include <linux/hardirq.h>
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#include <linux/module.h>
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#include <linux/uaccess.h>
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#include <linux/sched/debug.h>
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#include <asm/current.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, -EACCES, -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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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_DEFAULT;
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*code_out = SEGV_MAPERR;
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/*
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* If the fault was with pagefaults disabled, don't take the fault, just
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* fail.
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*/
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if (faulthandler_disabled())
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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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mmap_read_lock(mm);
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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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if (vma->vm_start <= address)
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goto good_area;
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if (!(vma->vm_flags & VM_GROWSDOWN))
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goto out;
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if (is_user && !ARCH_IS_STACKGROW(address))
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goto out;
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vma = expand_stack(mm, address);
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if (!vma)
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goto out_nosemaphore;
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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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vm_fault_t fault;
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fault = handle_mm_fault(vma, address, flags, NULL);
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if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
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goto out_nosemaphore;
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/* The fault is fully completed (including releasing mmap lock) */
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if (fault & VM_FAULT_COMPLETED)
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return 0;
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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_SIGSEGV) {
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goto out;
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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 (fault & VM_FAULT_RETRY) {
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flags |= FAULT_FLAG_TRIED;
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goto retry;
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}
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pmd = pmd_off(mm, 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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mmap_read_unlock(mm);
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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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mmap_read_unlock(mm);
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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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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 %px sp %px 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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current->thread.arch.faultinfo = fi;
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force_sig_fault(SIGSEGV, SEGV_ACCERR, (void __user *) FAULT_ADDRESS(fi));
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}
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void fatal_sigsegv(void)
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{
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force_fatal_sig(SIGSEGV);
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do_signal(¤t->thread.regs);
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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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/**
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* segv_handler() - the SIGSEGV handler
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* @sig: the signal number
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* @unused_si: the signal info struct; unused in this handler
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* @regs: the ptrace register information
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*
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* The handler first extracts the faultinfo from the UML ptrace regs struct.
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* If the userfault did not happen in an UML userspace process, bad_segv is called.
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* Otherwise the signal did happen in a cloned userspace process, handle it.
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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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jmp_buf *catcher;
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int si_code;
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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 (!is_user && 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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else if (!is_user && address > PAGE_SIZE && address < TASK_SIZE) {
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show_regs(container_of(regs, struct pt_regs, regs));
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panic("Kernel tried to access user memory at addr 0x%lx, ip 0x%lx",
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address, ip);
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}
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if (SEGV_IS_FIXABLE(&fi))
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err = handle_page_fault(address, ip, is_write, is_user,
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&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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current->thread.arch.faultinfo = fi;
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force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
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} else {
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BUG_ON(err != -EFAULT);
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current->thread.arch.faultinfo = fi;
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force_sig_fault(SIGSEGV, si_code, (void __user *) address);
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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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int code, err;
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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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/* Is the signal layout for the signal known?
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* Signal data must be scrubbed to prevent information leaks.
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*/
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code = si->si_code;
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err = si->si_errno;
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if ((err == 0) && (siginfo_layout(sig, code) == SIL_FAULT)) {
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struct faultinfo *fi = UPT_FAULTINFO(regs);
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current->thread.arch.faultinfo = *fi;
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force_sig_fault(sig, code, (void __user *)FAULT_ADDRESS(*fi));
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} else {
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printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d) with errno %d\n",
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sig, code, err);
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force_sig(sig);
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}
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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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