cregit-Linux how code gets into the kernel

Release 4.14 arch/nios2/mm/fault.c

Directory: arch/nios2/mm
 * Copyright (C) 2009 Wind River Systems Inc
 *   Implemented by and
 * based on arch/mips/mm/fault.c which is:
 * Copyright (C) 1995-2000 Ralf Baechle
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.

#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/extable.h>
#include <linux/uaccess.h>
#include <linux/ptrace.h>

#include <asm/mmu_context.h>
#include <asm/traps.h>

/* Supervisor only instruction address */

/* Supervisor only data address */

/* TLB permission violation (x) */

/* TLB permission violation (r) */

/* TLB permission violation (w) */

 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.

asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause, unsigned long address) { struct vm_area_struct *vma = NULL; struct task_struct *tsk = current; struct mm_struct *mm = tsk->mm; int code = SEGV_MAPERR; int fault; unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; cause >>= 2; /* Restart the instruction */ regs->ea -= 4; /* * 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 (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) { if (user_mode(regs)) goto bad_area_nosemaphore; else goto vmalloc_fault; } if (unlikely(address >= TASK_SIZE)) goto bad_area_nosemaphore; /* * If we're in an interrupt or have no user * context, we must not take the fault.. */ if (faulthandler_disabled() || !mm) goto bad_area_nosemaphore; if (user_mode(regs)) flags |= FAULT_FLAG_USER; if (!down_read_trylock(&mm->mmap_sem)) { if (!user_mode(regs) && !search_exception_tables(regs->ea)) goto bad_area_nosemaphore; retry: down_read(&mm->mmap_sem); } vma = find_vma(mm, address); if (!vma) goto bad_area; if (vma->vm_start <= address) goto good_area; if (!(vma->vm_flags & VM_GROWSDOWN)) goto bad_area; if (expand_stack(vma, address)) goto bad_area; /* * Ok, we have a good vm_area for this memory access, so * we can handle it.. */ good_area: code = SEGV_ACCERR; switch (cause) { case EXC_SUPERV_INSN_ACCESS: goto bad_area; case EXC_SUPERV_DATA_ACCESS: goto bad_area; case EXC_X_PROTECTION_FAULT: if (!(vma->vm_flags & VM_EXEC)) goto bad_area; break; case EXC_R_PROTECTION_FAULT: if (!(vma->vm_flags & VM_READ)) goto bad_area; break; case EXC_W_PROTECTION_FAULT: if (!(vma->vm_flags & VM_WRITE)) goto bad_area; flags = FAULT_FLAG_WRITE; break; } /* * 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); if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) return; if (unlikely(fault & VM_FAULT_ERROR)) { if (fault & VM_FAULT_OOM) goto out_of_memory; else if (fault & VM_FAULT_SIGSEGV) goto bad_area; else if (fault & VM_FAULT_SIGBUS) goto do_sigbus; BUG(); } /* * Major/minor page fault accounting is only done on the * initial attempt. If we go through a retry, it is extremely * likely that the page will be found in page cache at that point. */ if (flags & FAULT_FLAG_ALLOW_RETRY) { if (fault & VM_FAULT_MAJOR) current->maj_flt++; else current->min_flt++; if (fault & VM_FAULT_RETRY) { /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk * of starvation. */ flags &= ~FAULT_FLAG_ALLOW_RETRY; flags |= FAULT_FLAG_TRIED; /* * No need to up_read(&mm->mmap_sem) as we would * have already released it in __lock_page_or_retry * in mm/filemap.c. */ goto retry; } } up_read(&mm->mmap_sem); return; /* * 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: up_read(&mm->mmap_sem); bad_area_nosemaphore: /* User mode accesses just cause a SIGSEGV */ if (user_mode(regs)) { if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) { pr_info("%s: unhandled page fault (%d) at 0x%08lx, " "cause %ld\n", current->comm, SIGSEGV, address, cause); show_regs(regs); } _exception(SIGSEGV, regs, code, address); return; } no_context: /* 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("Unable to handle kernel %s at virtual address %08lx", address < PAGE_SIZE ? "NULL pointer dereference" : "paging request", address); pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra, cause); panic("Oops"); return; /* * We ran out of memory, or some other thing happened to us that made * us unable to handle the page fault gracefully. */ out_of_memory: up_read(&mm->mmap_sem); if (!user_mode(regs)) goto no_context; pagefault_out_of_memory(); return; do_sigbus: up_read(&mm->mmap_sem); /* Kernel mode? Handle exceptions or die */ if (!user_mode(regs)) goto no_context; _exception(SIGBUS, regs, BUS_ADRERR, address); return; vmalloc_fault: { /* * Synchronize this task's top level page-table * with the 'reference' page table. * * Do _not_ use "tsk" here. We might be inside * an interrupt in the middle of a task switch.. */ int offset = pgd_index(address); pgd_t *pgd, *pgd_k; pud_t *pud, *pud_k; pmd_t *pmd, *pmd_k; pte_t *pte_k; pgd = pgd_current + offset; pgd_k = init_mm.pgd + offset; if (!pgd_present(*pgd_k)) goto no_context; set_pgd(pgd, *pgd_k); pud = pud_offset(pgd, address); pud_k = pud_offset(pgd_k, address); if (!pud_present(*pud_k)) goto no_context; pmd = pmd_offset(pud, address); pmd_k = pmd_offset(pud_k, address); if (!pmd_present(*pmd_k)) goto no_context; set_pmd(pmd, *pmd_k); pte_k = pte_offset_kernel(pmd_k, address); if (!pte_present(*pte_k)) goto no_context; flush_tlb_one(address); return; } }


Ley Foon Tan76396.70%240.00%
Chung-Ling Tang151.90%120.00%
Linus Torvalds101.27%120.00%
David Hildenbrand10.13%120.00%

Overall Contributors

Ley Foon Tan83496.53%228.57%
Chung-Ling Tang151.74%114.29%
Linus Torvalds101.16%114.29%
Ingo Molnar30.35%114.29%
David Hildenbrand10.12%114.29%
Paul Gortmaker10.12%114.29%
Directory: arch/nios2/mm
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