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0c710050c4
Handle VM_FAULT_SIGSEGV in the page fault path so that we correctly
kill the process and we don't BUG() the kernel.
Fixes: 07037db5d4
("RISC-V: Paging and MMU")
Signed-off-by: Zhe Qiao <qiaozhe@iscas.ac.cn>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240731084547.85380-1-qiaozhe@iscas.ac.cn
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
384 lines
8.8 KiB
C
384 lines
8.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
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* Lennox Wu <lennox.wu@sunplusct.com>
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* Chen Liqin <liqin.chen@sunplusct.com>
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* Copyright (C) 2012 Regents of the University of California
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*/
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#include <linux/mm.h>
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#include <linux/kernel.h>
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#include <linux/interrupt.h>
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#include <linux/perf_event.h>
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#include <linux/signal.h>
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#include <linux/uaccess.h>
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#include <linux/kprobes.h>
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#include <linux/kfence.h>
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#include <linux/entry-common.h>
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#include <asm/ptrace.h>
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#include <asm/tlbflush.h>
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#include "../kernel/head.h"
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static void die_kernel_fault(const char *msg, unsigned long addr,
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struct pt_regs *regs)
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{
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bust_spinlocks(1);
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pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", msg,
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addr);
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bust_spinlocks(0);
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die(regs, "Oops");
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make_task_dead(SIGKILL);
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}
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static inline void no_context(struct pt_regs *regs, unsigned long addr)
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{
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const char *msg;
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/* Are we prepared to handle this kernel fault? */
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if (fixup_exception(regs))
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return;
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/*
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* Oops. The kernel tried to access some bad page. We'll have to
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* terminate things with extreme prejudice.
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*/
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if (addr < PAGE_SIZE)
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msg = "NULL pointer dereference";
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else {
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if (kfence_handle_page_fault(addr, regs->cause == EXC_STORE_PAGE_FAULT, regs))
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return;
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msg = "paging request";
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}
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die_kernel_fault(msg, addr, regs);
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}
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static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
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{
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if (!user_mode(regs)) {
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no_context(regs, addr);
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return;
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}
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if (fault & VM_FAULT_OOM) {
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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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pagefault_out_of_memory();
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return;
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} else if (fault & (VM_FAULT_SIGBUS | VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) {
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/* Kernel mode? Handle exceptions or die */
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do_trap(regs, SIGBUS, BUS_ADRERR, addr);
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return;
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} else if (fault & VM_FAULT_SIGSEGV) {
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do_trap(regs, SIGSEGV, SEGV_MAPERR, addr);
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return;
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}
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BUG();
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}
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static inline void
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bad_area_nosemaphore(struct pt_regs *regs, int code, unsigned long addr)
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{
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/*
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* Something tried to access memory that isn't in our memory map.
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* Fix it, but check if it's kernel or user first.
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*/
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/* User mode accesses just cause a SIGSEGV */
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if (user_mode(regs)) {
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do_trap(regs, SIGSEGV, code, addr);
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return;
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}
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no_context(regs, addr);
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}
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static inline void
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bad_area(struct pt_regs *regs, struct mm_struct *mm, int code,
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unsigned long addr)
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{
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mmap_read_unlock(mm);
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bad_area_nosemaphore(regs, code, addr);
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}
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static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
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{
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pgd_t *pgd, *pgd_k;
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pud_t *pud_k;
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p4d_t *p4d_k;
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pmd_t *pmd_k;
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pte_t *pte_k;
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int index;
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unsigned long pfn;
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/* User mode accesses just cause a SIGSEGV */
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if (user_mode(regs))
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return do_trap(regs, SIGSEGV, code, addr);
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/*
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* Synchronize this task's top level page-table
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* with the 'reference' page table.
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*
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* Do _not_ use "tsk->active_mm->pgd" here.
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* We might be inside an interrupt in the middle
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* of a task switch.
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*/
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index = pgd_index(addr);
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pfn = csr_read(CSR_SATP) & SATP_PPN;
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pgd = (pgd_t *)pfn_to_virt(pfn) + index;
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pgd_k = init_mm.pgd + index;
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if (!pgd_present(pgdp_get(pgd_k))) {
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no_context(regs, addr);
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return;
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}
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set_pgd(pgd, pgdp_get(pgd_k));
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p4d_k = p4d_offset(pgd_k, addr);
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if (!p4d_present(p4dp_get(p4d_k))) {
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no_context(regs, addr);
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return;
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}
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pud_k = pud_offset(p4d_k, addr);
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if (!pud_present(pudp_get(pud_k))) {
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no_context(regs, addr);
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return;
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}
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if (pud_leaf(pudp_get(pud_k)))
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goto flush_tlb;
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/*
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* Since the vmalloc area is global, it is unnecessary
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* to copy individual PTEs
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*/
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pmd_k = pmd_offset(pud_k, addr);
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if (!pmd_present(pmdp_get(pmd_k))) {
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no_context(regs, addr);
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return;
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}
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if (pmd_leaf(pmdp_get(pmd_k)))
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goto flush_tlb;
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/*
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* Make sure the actual PTE exists as well to
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* catch kernel vmalloc-area accesses to non-mapped
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* addresses. If we don't do this, this will just
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* silently loop forever.
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*/
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pte_k = pte_offset_kernel(pmd_k, addr);
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if (!pte_present(ptep_get(pte_k))) {
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no_context(regs, addr);
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return;
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}
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/*
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* The kernel assumes that TLBs don't cache invalid
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* entries, but in RISC-V, SFENCE.VMA specifies an
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* ordering constraint, not a cache flush; it is
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* necessary even after writing invalid entries.
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*/
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flush_tlb:
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local_flush_tlb_page(addr);
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}
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static inline bool access_error(unsigned long cause, struct vm_area_struct *vma)
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{
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switch (cause) {
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case EXC_INST_PAGE_FAULT:
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if (!(vma->vm_flags & VM_EXEC)) {
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return true;
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}
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break;
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case EXC_LOAD_PAGE_FAULT:
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/* Write implies read */
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if (!(vma->vm_flags & (VM_READ | VM_WRITE))) {
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return true;
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}
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break;
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case EXC_STORE_PAGE_FAULT:
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if (!(vma->vm_flags & VM_WRITE)) {
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return true;
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}
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break;
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default:
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panic("%s: unhandled cause %lu", __func__, cause);
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}
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return false;
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}
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/*
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* This routine handles page faults. It determines the address and the
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* problem, and then passes it off to one of the appropriate routines.
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*/
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void handle_page_fault(struct pt_regs *regs)
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{
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struct task_struct *tsk;
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struct vm_area_struct *vma;
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struct mm_struct *mm;
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unsigned long addr, cause;
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unsigned int flags = FAULT_FLAG_DEFAULT;
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int code = SEGV_MAPERR;
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vm_fault_t fault;
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cause = regs->cause;
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addr = regs->badaddr;
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tsk = current;
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mm = tsk->mm;
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if (kprobe_page_fault(regs, cause))
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return;
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/*
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* Fault-in kernel-space virtual memory on-demand.
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* The 'reference' page table is init_mm.pgd.
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*
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* NOTE! We MUST NOT take any locks for this case. We may
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* be in an interrupt or a critical region, and should
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* only copy the information from the master page table,
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* nothing more.
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*/
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if ((!IS_ENABLED(CONFIG_MMU) || !IS_ENABLED(CONFIG_64BIT)) &&
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unlikely(addr >= VMALLOC_START && addr < VMALLOC_END)) {
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vmalloc_fault(regs, code, addr);
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return;
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}
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/* Enable interrupts if they were enabled in the parent context. */
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if (!regs_irqs_disabled(regs))
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local_irq_enable();
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/*
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* If we're in an interrupt, have no user context, or are running
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* in an atomic region, then we must not take the fault.
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*/
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if (unlikely(faulthandler_disabled() || !mm)) {
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tsk->thread.bad_cause = cause;
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no_context(regs, addr);
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return;
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}
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if (user_mode(regs))
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flags |= FAULT_FLAG_USER;
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if (!user_mode(regs) && addr < TASK_SIZE && unlikely(!(regs->status & SR_SUM))) {
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if (fixup_exception(regs))
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return;
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die_kernel_fault("access to user memory without uaccess routines", addr, regs);
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}
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perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
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if (cause == EXC_STORE_PAGE_FAULT)
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flags |= FAULT_FLAG_WRITE;
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else if (cause == EXC_INST_PAGE_FAULT)
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flags |= FAULT_FLAG_INSTRUCTION;
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if (!(flags & FAULT_FLAG_USER))
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goto lock_mmap;
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vma = lock_vma_under_rcu(mm, addr);
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if (!vma)
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goto lock_mmap;
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if (unlikely(access_error(cause, vma))) {
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vma_end_read(vma);
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count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
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tsk->thread.bad_cause = cause;
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bad_area_nosemaphore(regs, SEGV_ACCERR, addr);
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return;
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}
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fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
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if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
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vma_end_read(vma);
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if (!(fault & VM_FAULT_RETRY)) {
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count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
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goto done;
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}
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count_vm_vma_lock_event(VMA_LOCK_RETRY);
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if (fault & VM_FAULT_MAJOR)
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flags |= FAULT_FLAG_TRIED;
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if (fault_signal_pending(fault, regs)) {
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if (!user_mode(regs))
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no_context(regs, addr);
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return;
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}
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lock_mmap:
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retry:
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vma = lock_mm_and_find_vma(mm, addr, regs);
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if (unlikely(!vma)) {
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tsk->thread.bad_cause = cause;
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bad_area_nosemaphore(regs, code, addr);
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return;
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}
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/*
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* Ok, we have a good vm_area for this memory access, so
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* we can handle it.
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*/
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code = SEGV_ACCERR;
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if (unlikely(access_error(cause, vma))) {
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tsk->thread.bad_cause = cause;
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bad_area(regs, mm, code, addr);
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return;
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}
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/*
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* If for any reason at all we could not handle the fault,
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* make sure we exit gracefully rather than endlessly redo
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* the fault.
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*/
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fault = handle_mm_fault(vma, addr, flags, regs);
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/*
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* If we need to retry but a fatal signal is pending, handle the
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* signal first. We do not need to release the mmap_lock because it
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* would already be released in __lock_page_or_retry in mm/filemap.c.
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*/
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if (fault_signal_pending(fault, regs)) {
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if (!user_mode(regs))
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no_context(regs, addr);
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return;
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}
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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;
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if (unlikely(fault & VM_FAULT_RETRY)) {
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flags |= FAULT_FLAG_TRIED;
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/*
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* No need to mmap_read_unlock(mm) as we would
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* have already released it in __lock_page_or_retry
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* in mm/filemap.c.
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*/
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goto retry;
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}
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mmap_read_unlock(mm);
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done:
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if (unlikely(fault & VM_FAULT_ERROR)) {
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tsk->thread.bad_cause = cause;
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mm_fault_error(regs, addr, fault);
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return;
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}
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return;
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}
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