https://github.com/torvalds/linux
Tip revision: d07f6ca923ea0927a1024dfccafc5b53b61cfecc authored by Linus Torvalds on 16 May 2021, 22:27:44 UTC
Linux 5.13-rc2
Linux 5.13-rc2
Tip revision: d07f6ca
fault.c
// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
#include <linux/extable.h>
#include <linux/kprobes.h>
#include <linux/mmu_context.h>
#include <linux/perf_event.h>
int fixup_exception(struct pt_regs *regs)
{
const struct exception_table_entry *fixup;
fixup = search_exception_tables(instruction_pointer(regs));
if (fixup) {
regs->pc = fixup->fixup;
return 1;
}
return 0;
}
static inline bool is_write(struct pt_regs *regs)
{
switch (trap_no(regs)) {
case VEC_TLBINVALIDS:
return true;
case VEC_TLBMODIFIED:
return true;
}
return false;
}
#ifdef CONFIG_CPU_HAS_LDSTEX
static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
{
return;
}
#else
extern unsigned long csky_cmpxchg_ldw;
extern unsigned long csky_cmpxchg_stw;
static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
{
if (trap_no(regs) != VEC_TLBMODIFIED)
return;
if (instruction_pointer(regs) == csky_cmpxchg_stw)
instruction_pointer_set(regs, csky_cmpxchg_ldw);
return;
}
#endif
static inline void no_context(struct pt_regs *regs, unsigned long addr)
{
current->thread.trap_no = trap_no(regs);
/* 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 paging request at virtual "
"addr 0x%08lx, pc: 0x%08lx\n", addr, regs->pc);
die(regs, "Oops");
do_exit(SIGKILL);
}
static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
{
current->thread.trap_no = trap_no(regs);
if (fault & VM_FAULT_OOM) {
/*
* 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, addr);
return;
}
pagefault_out_of_memory();
return;
} else if (fault & VM_FAULT_SIGBUS) {
/* Kernel mode? Handle exceptions or die */
if (!user_mode(regs)) {
no_context(regs, addr);
return;
}
do_trap(regs, SIGBUS, BUS_ADRERR, addr);
return;
}
BUG();
}
static inline void bad_area(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr)
{
/*
* Something tried to access memory that isn't in our memory map.
* Fix it, but check if it's kernel or user first.
*/
mmap_read_unlock(mm);
/* User mode accesses just cause a SIGSEGV */
if (user_mode(regs)) {
do_trap(regs, SIGSEGV, code, addr);
return;
}
no_context(regs, addr);
}
static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
{
pgd_t *pgd, *pgd_k;
pud_t *pud, *pud_k;
pmd_t *pmd, *pmd_k;
pte_t *pte_k;
int offset;
/* User mode accesses just cause a SIGSEGV */
if (user_mode(regs)) {
do_trap(regs, SIGSEGV, code, addr);
return;
}
/*
* 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..
*/
offset = pgd_index(addr);
pgd = get_pgd() + offset;
pgd_k = init_mm.pgd + offset;
if (!pgd_present(*pgd_k)) {
no_context(regs, addr);
return;
}
set_pgd(pgd, *pgd_k);
pud = (pud_t *)pgd;
pud_k = (pud_t *)pgd_k;
if (!pud_present(*pud_k)) {
no_context(regs, addr);
return;
}
pmd = pmd_offset(pud, addr);
pmd_k = pmd_offset(pud_k, addr);
if (!pmd_present(*pmd_k)) {
no_context(regs, addr);
return;
}
set_pmd(pmd, *pmd_k);
pte_k = pte_offset_kernel(pmd_k, addr);
if (!pte_present(*pte_k)) {
no_context(regs, addr);
return;
}
flush_tlb_one(addr);
}
static inline bool access_error(struct pt_regs *regs, struct vm_area_struct *vma)
{
if (is_write(regs)) {
if (!(vma->vm_flags & VM_WRITE))
return true;
} else {
if (unlikely(!vma_is_accessible(vma)))
return true;
}
return false;
}
/*
* 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)
{
struct task_struct *tsk;
struct vm_area_struct *vma;
struct mm_struct *mm;
unsigned long addr = read_mmu_entryhi() & PAGE_MASK;
unsigned int flags = FAULT_FLAG_DEFAULT;
int code = SEGV_MAPERR;
vm_fault_t fault;
tsk = current;
mm = tsk->mm;
csky_cmpxchg_fixup(regs);
if (kprobe_page_fault(regs, tsk->thread.trap_no))
return;
/*
* 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((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) {
vmalloc_fault(regs, code, addr);
return;
}
/* Enable interrupts if they were enabled in the parent context. */
if (likely(regs->sr & BIT(6)))
local_irq_enable();
/*
* If we're in an interrupt, have no user context, or are running
* in an atomic region, then we must not take the fault.
*/
if (unlikely(faulthandler_disabled() || !mm)) {
no_context(regs, addr);
return;
}
if (user_mode(regs))
flags |= FAULT_FLAG_USER;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
if (is_write(regs))
flags |= FAULT_FLAG_WRITE;
retry:
mmap_read_lock(mm);
vma = find_vma(mm, addr);
if (unlikely(!vma)) {
bad_area(regs, mm, code, addr);
return;
}
if (likely(vma->vm_start <= addr))
goto good_area;
if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
bad_area(regs, mm, code, addr);
return;
}
if (unlikely(expand_stack(vma, addr))) {
bad_area(regs, mm, code, addr);
return;
}
/*
* Ok, we have a good vm_area for this memory access, so
* we can handle it.
*/
good_area:
code = SEGV_ACCERR;
if (unlikely(access_error(regs, vma))) {
bad_area(regs, mm, code, addr);
return;
}
/*
* If for any reason at all we could not handle the fault,
* make sure we exit gracefully rather than endlessly redo
* the fault.
*/
fault = handle_mm_fault(vma, addr, flags, regs);
/*
* If we need to retry but a fatal signal is pending, handle the
* signal first. We do not need to release the mmap_lock because it
* would already be released in __lock_page_or_retry in mm/filemap.c.
*/
if (fault_signal_pending(fault, regs)) {
if (!user_mode(regs))
no_context(regs, addr);
return;
}
if (unlikely((fault & VM_FAULT_RETRY) && (flags & FAULT_FLAG_ALLOW_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;
}
mmap_read_unlock(mm);
if (unlikely(fault & VM_FAULT_ERROR)) {
mm_fault_error(regs, addr, fault);
return;
}
return;
}