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/*
* Meta page fault handling.
*
* Copyright (C) 2005-2012 Imagination Technologies Ltd.
*/
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/interrupt.h>
#include <linux/uaccess.h>
#include <asm/tlbflush.h>
#include <asm/mmu.h>
#include <asm/traps.h>
/* Clear any pending catch buffer state. */
static void clear_cbuf_entry(struct pt_regs *regs, unsigned long addr,
unsigned int trapno)
{
PTBICTXEXTCB0 cbuf = regs->extcb0;
switch (trapno) {
/* Instruction fetch faults leave no catch buffer state. */
case TBIXXF_SIGNUM_IGF:
case TBIXXF_SIGNUM_IPF:
return;
default:
if (cbuf[0].CBAddr == addr) {
cbuf[0].CBAddr = 0;
cbuf[0].CBFlags &= ~TXCATCH0_FAULT_BITS;
/* And, as this is the ONLY catch entry, we
* need to clear the cbuf bit from the context!
*/
regs->ctx.SaveMask &= ~(TBICTX_CBUF_BIT |
TBICTX_XCBF_BIT);
return;
}
pr_err("Failed to clear cbuf entry!\n");
}
}
int show_unhandled_signals = 1;
int do_page_fault(struct pt_regs *regs, unsigned long address,
unsigned int write_access, unsigned int trapno)
{
struct task_struct *tsk;
struct mm_struct *mm;
struct vm_area_struct *vma, *prev_vma;
siginfo_t info;
int fault;
unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
tsk = current;
if ((address >= VMALLOC_START) && (address < VMALLOC_END)) {
/*
* 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_t *)mmu_get_base()) + offset;
pgd_k = swapper_pg_dir + offset;
/* This will never happen with the folded page table. */
if (!pgd_present(*pgd)) {
if (!pgd_present(*pgd_k))
goto bad_area_nosemaphore;
set_pgd(pgd, *pgd_k);
return 0;
}
pud = pud_offset(pgd, address);
pud_k = pud_offset(pgd_k, address);
if (!pud_present(*pud_k))
goto bad_area_nosemaphore;
set_pud(pud, *pud_k);
pmd = pmd_offset(pud, address);
pmd_k = pmd_offset(pud_k, address);
if (!pmd_present(*pmd_k))
goto bad_area_nosemaphore;
set_pmd(pmd, *pmd_k);
pte_k = pte_offset_kernel(pmd_k, address);
if (!pte_present(*pte_k))
goto bad_area_nosemaphore;
/* May only be needed on Chorus2 */
flush_tlb_all();
return 0;
}
mm = tsk->mm;
if (in_atomic() || !mm)
goto no_context;
if (user_mode(regs))
flags |= FAULT_FLAG_USER;
retry:
down_read(&mm->mmap_sem);
vma = find_vma_prev(mm, address, &prev_vma);
if (!vma || address < vma->vm_start)
goto check_expansion;
good_area:
if (write_access) {
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
flags |= FAULT_FLAG_WRITE;
} else {
if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
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(mm, vma, address, flags);
if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
return 0;
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM)
goto out_of_memory;
else if (fault & VM_FAULT_SIGBUS)
goto do_sigbus;
BUG();
}
if (flags & FAULT_FLAG_ALLOW_RETRY) {
if (fault & VM_FAULT_MAJOR)
tsk->maj_flt++;
else
tsk->min_flt++;
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 0;
check_expansion:
vma = prev_vma;
if (vma && (expand_stack(vma, address) == 0))
goto good_area;
bad_area:
up_read(&mm->mmap_sem);
bad_area_nosemaphore:
if (user_mode(regs)) {
info.si_signo = SIGSEGV;
info.si_errno = 0;
info.si_code = SEGV_MAPERR;
info.si_addr = (__force void __user *)address;
info.si_trapno = trapno;
if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
printk_ratelimit()) {
pr_info("%s%s[%d]: segfault at %lx pc %08x sp %08x write %d trap %#x (%s)",
task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
tsk->comm, task_pid_nr(tsk), address,
regs->ctx.CurrPC, regs->ctx.AX[0].U0,
write_access, trapno, trap_name(trapno));
print_vma_addr(" in ", regs->ctx.CurrPC);
print_vma_addr(" rtp in ", regs->ctx.DX[4].U1);
printk("\n");
show_regs(regs);
}
force_sig_info(SIGSEGV, &info, tsk);
return 1;
}
goto no_context;
do_sigbus:
up_read(&mm->mmap_sem);
/*
* Send a sigbus, regardless of whether we were in kernel
* or user mode.
*/
info.si_signo = SIGBUS;
info.si_errno = 0;
info.si_code = BUS_ADRERR;
info.si_addr = (__force void __user *)address;
info.si_trapno = trapno;
force_sig_info(SIGBUS, &info, tsk);
/* Kernel mode? Handle exceptions or die */
if (!user_mode(regs))
goto no_context;
return 1;
/*
* 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)) {
pagefault_out_of_memory();
return 1;
}
no_context:
/* Are we prepared to handle this kernel fault? */
if (fixup_exception(regs)) {
clear_cbuf_entry(regs, address, trapno);
return 1;
}
die("Oops", regs, (write_access << 15) | trapno, address);
do_exit(SIGKILL);
}
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