// TODO VM_EXEC flag work-around, cache aliasing
/*
* arch/xtensa/mm/fault.c
*
* 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.
*
* Copyright (C) 2001 - 2010 Tensilica Inc.
*
* Chris Zankel <[email protected]>
* Joe Taylor <[email protected], [email protected]>
*/
#include <linux/mm.h>
#include <linux/extable.h>
#include <linux/hardirq.h>
#include <linux/perf_event.h>
#include <linux/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/cacheflush.h>
#include <asm/hardirq.h>
#include <asm/traps.h>
void bad_page_fault(struct pt_regs*, unsigned long, int);
static void vmalloc_fault(struct pt_regs *regs, unsigned int address)
{
#ifdef CONFIG_MMU
/* Synchronize this task's top level page-table
* with the 'reference' page table.
*/
struct mm_struct *act_mm = current->active_mm;
int index = pgd_index(address);
pgd_t *pgd, *pgd_k;
p4d_t *p4d, *p4d_k;
pud_t *pud, *pud_k;
pmd_t *pmd, *pmd_k;
pte_t *pte_k;
if (act_mm == NULL)
goto bad_page_fault;
pgd = act_mm->pgd + index;
pgd_k = init_mm.pgd + index;
if (!pgd_present(*pgd_k))
goto bad_page_fault;
pgd_val(*pgd) = pgd_val(*pgd_k);
p4d = p4d_offset(pgd, address);
p4d_k = p4d_offset(pgd_k, address);
if (!p4d_present(*p4d) || !p4d_present(*p4d_k))
goto bad_page_fault;
pud = pud_offset(p4d, address);
pud_k = pud_offset(p4d_k, address);
if (!pud_present(*pud) || !pud_present(*pud_k))
goto bad_page_fault;
pmd = pmd_offset(pud, address);
pmd_k = pmd_offset(pud_k, address);
if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
goto bad_page_fault;
pmd_val(*pmd) = pmd_val(*pmd_k);
pte_k = pte_offset_kernel(pmd_k, address);
if (!pte_present(*pte_k))
goto bad_page_fault;
return;
bad_page_fault:
bad_page_fault(regs, address, SIGKILL);
#else
WARN_ONCE(1, "%s in noMMU configuration\n", __func__);
#endif
}
/*
* This routine handles page faults. It determines the address,
* and the problem, and then passes it off to one of the appropriate
* routines.
*
* Note: does not handle Miss and MultiHit.
*/
void do_page_fault(struct pt_regs *regs)
{
struct vm_area_struct * vma;
struct mm_struct *mm = current->mm;
unsigned int exccause = regs->exccause;
unsigned int address = regs->excvaddr;
int code;
int is_write, is_exec;
vm_fault_t fault;
unsigned int flags = FAULT_FLAG_DEFAULT;
code = SEGV_MAPERR;
/* We fault-in kernel-space virtual memory on-demand. The
* 'reference' page table is init_mm.pgd.
*/
if (address >= TASK_SIZE && !user_mode(regs)) {
vmalloc_fault(regs, address);
return;
}
/* If we're in an interrupt or have no user
* context, we must not take the fault..
*/
if (faulthandler_disabled() || !mm) {
bad_page_fault(regs, address, SIGSEGV);
return;
}
is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
exccause == EXCCAUSE_ITLB_MISS ||
exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
current->comm, current->pid,
address, exccause, regs->pc,
is_write ? "w" : "", is_exec ? "x" : "");
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 (!vma)
goto bad_area_nosemaphore;
/* Ok, we have a good vm_area for this memory access, so
* we can handle it..
*/
code = SEGV_ACCERR;
if (is_write) {
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
flags |= FAULT_FLAG_WRITE;
} else if (is_exec) {
if (!(vma->vm_flags & VM_EXEC))
goto bad_area;
} else /* Allow read even from write-only pages. */
if (!(vma->vm_flags & (VM_READ | 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(vma, address, flags, regs);
if (fault_signal_pending(fault, regs)) {
if (!user_mode(regs))
bad_page_fault(regs, address, SIGKILL);
return;
}
/* The fault is fully completed (including releasing mmap lock) */
if (fault & VM_FAULT_COMPLETED)
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();
}
if (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;
}
mmap_read_unlock(mm);
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:
mmap_read_unlock(mm);
bad_area_nosemaphore:
if (user_mode(regs)) {
force_sig_fault(SIGSEGV, code, (void *) address);
return;
}
bad_page_fault(regs, address, SIGSEGV);
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:
mmap_read_unlock(mm);
if (!user_mode(regs))
bad_page_fault(regs, address, SIGKILL);
else
pagefault_out_of_memory();
return;
do_sigbus:
mmap_read_unlock(mm);
/* Send a sigbus, regardless of whether we were in kernel
* or user mode.
*/
force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address);
/* Kernel mode? Handle exceptions or die */
if (!user_mode(regs))
bad_page_fault(regs, address, SIGBUS);
return;
}
void
bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
{
extern void __noreturn die(const char*, struct pt_regs*, long);
const struct exception_table_entry *entry;
/* Are we prepared to handle this kernel fault? */
if ((entry = search_exception_tables(regs->pc)) != NULL) {
pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
current->comm, regs->pc, entry->fixup);
regs->pc = entry->fixup;
return;
}
/* Oops. The kernel tried to access some bad page. We'll have to
* terminate things with extreme prejudice.
*/
pr_alert("Unable to handle kernel paging request at virtual "
"address %08lx\n pc = %08lx, ra = %08lx\n",
address, regs->pc, regs->areg[0]);
die("Oops", regs, sig);
}
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