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- // SPDX-License-Identifier: GPL-2.0
- /*
- * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
- *
- * Derived from MIPS:
- * Copyright (C) 1995 - 2000 by Ralf Baechle
- */
- #include <linux/context_tracking.h>
- #include <linux/signal.h>
- #include <linux/sched.h>
- #include <linux/interrupt.h>
- #include <linux/kernel.h>
- #include <linux/entry-common.h>
- #include <linux/errno.h>
- #include <linux/string.h>
- #include <linux/types.h>
- #include <linux/ptrace.h>
- #include <linux/ratelimit.h>
- #include <linux/mman.h>
- #include <linux/mm.h>
- #include <linux/smp.h>
- #include <linux/kdebug.h>
- #include <linux/kprobes.h>
- #include <linux/perf_event.h>
- #include <linux/uaccess.h>
- #include <asm/branch.h>
- #include <asm/mmu_context.h>
- #include <asm/ptrace.h>
- int show_unhandled_signals = 1;
- static void __kprobes no_context(struct pt_regs *regs, unsigned long address)
- {
- const int field = sizeof(unsigned long) * 2;
- /* Are we prepared to handle this kernel fault? */
- if (fixup_exception(regs))
- return;
- /*
- * Oops. The kernel tried to access some bad page. We'll have to
- * terminate things with extreme prejudice.
- */
- bust_spinlocks(1);
- pr_alert("CPU %d Unable to handle kernel paging request at "
- "virtual address %0*lx, era == %0*lx, ra == %0*lx\n",
- raw_smp_processor_id(), field, address, field, regs->csr_era,
- field, regs->regs[1]);
- die("Oops", regs);
- }
- static void __kprobes do_out_of_memory(struct pt_regs *regs, unsigned long address)
- {
- /*
- * We ran out of memory, call the OOM killer, and return the userspace
- * (which will retry the fault, or kill us if we got oom-killed).
- */
- if (!user_mode(regs)) {
- no_context(regs, address);
- return;
- }
- pagefault_out_of_memory();
- }
- static void __kprobes do_sigbus(struct pt_regs *regs,
- unsigned long write, unsigned long address, int si_code)
- {
- /* Kernel mode? Handle exceptions or die */
- if (!user_mode(regs)) {
- no_context(regs, address);
- return;
- }
- /*
- * Send a sigbus, regardless of whether we were in kernel
- * or user mode.
- */
- current->thread.csr_badvaddr = address;
- current->thread.trap_nr = read_csr_excode();
- force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
- }
- static void __kprobes do_sigsegv(struct pt_regs *regs,
- unsigned long write, unsigned long address, int si_code)
- {
- const int field = sizeof(unsigned long) * 2;
- static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
- /* Kernel mode? Handle exceptions or die */
- if (!user_mode(regs)) {
- no_context(regs, address);
- return;
- }
- /* User mode accesses just cause a SIGSEGV */
- current->thread.csr_badvaddr = address;
- if (!write)
- current->thread.error_code = 1;
- else
- current->thread.error_code = 2;
- current->thread.trap_nr = read_csr_excode();
- if (show_unhandled_signals &&
- unhandled_signal(current, SIGSEGV) && __ratelimit(&ratelimit_state)) {
- pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n",
- current->comm,
- write ? "write access to" : "read access from",
- field, address);
- pr_info("era = %0*lx in", field,
- (unsigned long) regs->csr_era);
- print_vma_addr(KERN_CONT " ", regs->csr_era);
- pr_cont("\n");
- pr_info("ra = %0*lx in", field,
- (unsigned long) regs->regs[1]);
- print_vma_addr(KERN_CONT " ", regs->regs[1]);
- pr_cont("\n");
- }
- force_sig_fault(SIGSEGV, si_code, (void __user *)address);
- }
- /*
- * This routine handles page faults. It determines the address,
- * and the problem, and then passes it off to one of the appropriate
- * routines.
- */
- static void __kprobes __do_page_fault(struct pt_regs *regs,
- unsigned long write, unsigned long address)
- {
- int si_code = SEGV_MAPERR;
- unsigned int flags = FAULT_FLAG_DEFAULT;
- struct task_struct *tsk = current;
- struct mm_struct *mm = tsk->mm;
- struct vm_area_struct *vma = NULL;
- vm_fault_t fault;
- /*
- * We fault-in kernel-space virtual memory on-demand. The
- * 'reference' page table is init_mm.pgd.
- *
- * NOTE! We MUST NOT take any locks for this case. We may
- * be in an interrupt or a critical region, and should
- * only copy the information from the master page table,
- * nothing more.
- */
- if (address & __UA_LIMIT) {
- if (!user_mode(regs))
- no_context(regs, address);
- else
- do_sigsegv(regs, write, address, si_code);
- return;
- }
- /*
- * If we're in an interrupt or have no user
- * context, we must not take the fault..
- */
- if (faulthandler_disabled() || !mm) {
- do_sigsegv(regs, write, address, si_code);
- return;
- }
- if (user_mode(regs))
- flags |= FAULT_FLAG_USER;
- perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
- retry:
- vma = lock_mm_and_find_vma(mm, address, regs);
- if (unlikely(!vma))
- goto bad_area_nosemaphore;
- goto good_area;
- /*
- * Something tried to access memory that isn't in our memory map..
- * Fix it, but check if it's kernel or user first..
- */
- bad_area:
- mmap_read_unlock(mm);
- bad_area_nosemaphore:
- do_sigsegv(regs, write, address, si_code);
- return;
- /*
- * Ok, we have a good vm_area for this memory access, so
- * we can handle it..
- */
- good_area:
- si_code = SEGV_ACCERR;
- if (write) {
- flags |= FAULT_FLAG_WRITE;
- if (!(vma->vm_flags & VM_WRITE))
- goto bad_area;
- } else {
- if (!(vma->vm_flags & VM_READ) && address != exception_era(regs))
- goto bad_area;
- if (!(vma->vm_flags & VM_EXEC) && address == exception_era(regs))
- goto bad_area;
- }
- /*
- * If for any reason at all we couldn't handle the fault,
- * make sure we exit gracefully rather than endlessly redo
- * the fault.
- */
- fault = handle_mm_fault(vma, address, flags, regs);
- if (fault_signal_pending(fault, regs)) {
- if (!user_mode(regs))
- no_context(regs, address);
- return;
- }
- /* The fault is fully completed (including releasing mmap lock) */
- if (fault & VM_FAULT_COMPLETED)
- return;
- if (unlikely(fault & VM_FAULT_RETRY)) {
- flags |= FAULT_FLAG_TRIED;
- /*
- * No need to mmap_read_unlock(mm) as we would
- * have already released it in __lock_page_or_retry
- * in mm/filemap.c.
- */
- goto retry;
- }
- if (unlikely(fault & VM_FAULT_ERROR)) {
- mmap_read_unlock(mm);
- if (fault & VM_FAULT_OOM) {
- do_out_of_memory(regs, address);
- return;
- } else if (fault & VM_FAULT_SIGSEGV) {
- do_sigsegv(regs, write, address, si_code);
- return;
- } else if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
- do_sigbus(regs, write, address, si_code);
- return;
- }
- BUG();
- }
- mmap_read_unlock(mm);
- }
- asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
- unsigned long write, unsigned long address)
- {
- irqentry_state_t state = irqentry_enter(regs);
- /* Enable interrupt if enabled in parent context */
- if (likely(regs->csr_prmd & CSR_PRMD_PIE))
- local_irq_enable();
- __do_page_fault(regs, write, address);
- local_irq_disable();
- irqentry_exit(regs, state);
- }
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