// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2005-2017 Andes Technology Corporation
#include <linux/extable.h>
#include <linux/module.h>
#include <linux/signal.h>
#include <linux/ptrace.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/hardirq.h>
#include <linux/uaccess.h>
#include <linux/perf_event.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
extern void die(const char *str, struct pt_regs *regs, long err);
/*
* This is useful to dump out the page tables associated with
* 'addr' in mm 'mm'.
*/
void show_pte(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
if (!mm)
mm = &init_mm;
pr_alert("pgd = %p\n", mm->pgd);
pgd = pgd_offset(mm, addr);
pr_alert("[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
do {
pmd_t *pmd;
if (pgd_none(*pgd))
break;
if (pgd_bad(*pgd)) {
pr_alert("(bad)");
break;
}
pmd = pmd_offset(pgd, addr);
#if PTRS_PER_PMD != 1
pr_alert(", *pmd=%08lx", pmd_val(*pmd));
#endif
if (pmd_none(*pmd))
break;
if (pmd_bad(*pmd)) {
pr_alert("(bad)");
break;
}
if (IS_ENABLED(CONFIG_HIGHMEM))
{
pte_t *pte;
/* We must not map this if we have highmem enabled */
pte = pte_offset_map(pmd, addr);
pr_alert(", *pte=%08lx", pte_val(*pte));
pte_unmap(pte);
}
} while (0);
pr_alert("\n");
}
void do_page_fault(unsigned long entry, unsigned long addr,
unsigned int error_code, struct pt_regs *regs)
{
struct task_struct *tsk;
struct mm_struct *mm;
struct vm_area_struct *vma;
int si_code;
vm_fault_t fault;
unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
error_code = error_code & (ITYPE_mskINST | ITYPE_mskETYPE);
tsk = current;
mm = tsk->mm;
si_code = SEGV_MAPERR;
/*
* 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 (addr >= TASK_SIZE) {
if (user_mode(regs))
goto bad_area_nosemaphore;
if (addr >= TASK_SIZE && addr < VMALLOC_END
&& (entry == ENTRY_PTE_NOT_PRESENT))
goto vmalloc_fault;
else
goto no_context;
}
/* Send a signal to the task for handling the unalignment access. */
if (entry == ENTRY_GENERAL_EXCPETION
&& error_code == ETYPE_ALIGNMENT_CHECK) {
if (user_mode(regs))
goto bad_area_nosemaphore;
else
goto no_context;
}
/*
* If we're in an interrupt or have no user
* context, we must not take the fault..
*/
if (unlikely(faulthandler_disabled() || !mm))
goto no_context;
/*
* As per x86, we may deadlock here. However, since the kernel only
* validly references user space from well defined areas of the code,
* we can bug out early if this is from code which shouldn't.
*/
if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
if (!user_mode(regs) &&
!search_exception_tables(instruction_pointer(regs)))
goto no_context;
retry:
down_read(&mm->mmap_sem);
} else {
/*
* The above down_read_trylock() might have succeeded in which
* case, we'll have missed the might_sleep() from down_read().
*/
might_sleep();
if (IS_ENABLED(CONFIG_DEBUG_VM)) {
if (!user_mode(regs) &&
!search_exception_tables(instruction_pointer(regs)))
goto no_context;
}
}
vma = find_vma(mm, addr);
if (unlikely(!vma))
goto bad_area;
if (vma->vm_start <= addr)
goto good_area;
if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
goto bad_area;
if (unlikely(expand_stack(vma, addr)))
goto bad_area;
/*
* Ok, we have a good vm_area for this memory access, so
* we can handle it..
*/
good_area:
si_code = SEGV_ACCERR;
/* first do some preliminary protection checks */
if (entry == ENTRY_PTE_NOT_PRESENT) {
if (error_code & ITYPE_mskINST)
mask = VM_EXEC;
else {
mask = VM_READ | VM_WRITE;
}
} else if (entry == ENTRY_TLB_MISC) {
switch (error_code & ITYPE_mskETYPE) {
case RD_PROT:
mask = VM_READ;
break;
case WRT_PROT:
mask = VM_WRITE;
flags |= FAULT_FLAG_WRITE;
break;
case NOEXEC:
mask = VM_EXEC;
break;
case PAGE_MODIFY:
mask = VM_WRITE;
flags |= FAULT_FLAG_WRITE;
break;
case ACC_BIT:
BUG();
default:
break;
}
}
if (!(vma->vm_flags & mask))
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, addr, flags);
/*
* If we need to retry but a fatal signal is pending, handle the
* signal first. We do not need to release the mmap_sem because it
* would already be released in __lock_page_or_retry in mm/filemap.c.
*/
if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
if (!user_mode(regs))
goto no_context;
return;
}
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM)
goto out_of_memory;
else if (fault & VM_FAULT_SIGBUS)
goto do_sigbus;
else
goto bad_area;
}
/*
* 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.
*/
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
if (flags & FAULT_FLAG_ALLOW_RETRY) {
if (fault & VM_FAULT_MAJOR) {
tsk->maj_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
1, regs, addr);
} else {
tsk->min_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
1, regs, addr);
}
if (fault & VM_FAULT_RETRY) {
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)) {
tsk->thread.address = addr;
tsk->thread.error_code = error_code;
tsk->thread.trap_no = entry;
force_sig_fault(SIGSEGV, si_code, (void __user *)addr);
return;
}
no_context:
/* Are we prepared to handle this kernel fault?
*
* (The kernel has valid exception-points in the source
* when it acesses user-memory. When it fails in one
* of those points, we find it in a table and do a jump
* to some fixup code that loads an appropriate error
* code)
*/
{
const struct exception_table_entry *entry;
if ((entry =
search_exception_tables(instruction_pointer(regs))) !=
NULL) {
/* Adjust the instruction pointer in the stackframe */
instruction_pointer(regs) = entry->fixup;
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\n",
(addr < PAGE_SIZE) ? "NULL pointer dereference" :
"paging request", addr);
show_pte(mm, addr);
die("Oops", regs, error_code);
bust_spinlocks(0);
do_exit(SIGKILL);
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;
/*
* Send a sigbus
*/
tsk->thread.address = addr;
tsk->thread.error_code = error_code;
tsk->thread.trap_no = entry;
force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)addr);
return;
vmalloc_fault:
{
/*
* Synchronize this task's top level page-table
* with the 'reference' page table.
*
* Use current_pgd instead of tsk->active_mm->pgd
* since the latter might be unavailable if this
* code is executed in a misfortunately run irq
* (like inside schedule() between switch_mm and
* switch_to...).
*/
unsigned int index = pgd_index(addr);
pgd_t *pgd, *pgd_k;
pud_t *pud, *pud_k;
pmd_t *pmd, *pmd_k;
pte_t *pte_k;
pgd = (pgd_t *) __va(__nds32__mfsr(NDS32_SR_L1_PPTB)) + index;
pgd_k = init_mm.pgd + index;
if (!pgd_present(*pgd_k))
goto no_context;
pud = pud_offset(pgd, addr);
pud_k = pud_offset(pgd_k, addr);
if (!pud_present(*pud_k))
goto no_context;
pmd = pmd_offset(pud, addr);
pmd_k = pmd_offset(pud_k, addr);
if (!pmd_present(*pmd_k))
goto no_context;
if (!pmd_present(*pmd))
set_pmd(pmd, *pmd_k);
else
BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
/*
* Since the vmalloc area is global, we don't
* need to copy individual PTE's, it is enough to
* copy the pgd pointer into the pte page of the
* root task. If that is there, we'll find our pte if
* it exists.
*/
/* Make sure the actual PTE exists as well to
* catch kernel vmalloc-area accesses to non-mapped
* addres. If we don't do this, this will just
* silently loop forever.
*/
pte_k = pte_offset_kernel(pmd_k, addr);
if (!pte_present(*pte_k))
goto no_context;
return;
}
}
