linux/arch/mn10300/mm/fault.c

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/* MN10300 MMU Fault handler
*
* Copyright (C) 2007 Matsushita Electric Industrial Co., Ltd.
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Modified by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/signal.h>
#include <linux/sched.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/smp.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/vt_kern.h> /* For unblank_screen() */
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
#include <asm/hardirq.h>
#include <asm/cpu-regs.h>
#include <asm/debugger.h>
#include <asm/gdb-stub.h>
/*
* Unlock any spinlocks which will prevent us from getting the
* message out
*/
void bust_spinlocks(int yes)
{
if (yes) {
oops_in_progress = 1;
} else {
int loglevel_save = console_loglevel;
#ifdef CONFIG_VT
unblank_screen();
#endif
oops_in_progress = 0;
/*
* OK, the message is on the console. Now we call printk()
* without oops_in_progress set so that printk will give klogd
* a poke. Hold onto your hats...
*/
console_loglevel = 15; /* NMI oopser may have shut the console
* up */
printk(" ");
console_loglevel = loglevel_save;
}
}
void do_BUG(const char *file, int line)
{
bust_spinlocks(1);
printk(KERN_EMERG "------------[ cut here ]------------\n");
printk(KERN_EMERG "kernel BUG at %s:%d!\n", file, line);
}
#if 0
static void print_pagetable_entries(pgd_t *pgdir, unsigned long address)
{
pgd_t *pgd;
pmd_t *pmd;
pte_t *pte;
pgd = pgdir + __pgd_offset(address);
printk(KERN_DEBUG "pgd entry %p: %016Lx\n",
pgd, (long long) pgd_val(*pgd));
if (!pgd_present(*pgd)) {
printk(KERN_DEBUG "... pgd not present!\n");
return;
}
pmd = pmd_offset(pgd, address);
printk(KERN_DEBUG "pmd entry %p: %016Lx\n",
pmd, (long long)pmd_val(*pmd));
if (!pmd_present(*pmd)) {
printk(KERN_DEBUG "... pmd not present!\n");
return;
}
pte = pte_offset(pmd, address);
printk(KERN_DEBUG "pte entry %p: %016Lx\n",
pte, (long long) pte_val(*pte));
if (!pte_present(*pte))
printk(KERN_DEBUG "... pte not present!\n");
}
#endif
/*
* This routine handles page faults. It determines the address,
* and the problem, and then passes it off to one of the appropriate
* routines.
*
* fault_code:
* - LSW: either MMUFCR_IFC or MMUFCR_DFC as appropriate
* - MSW: 0 if data access, 1 if instruction access
* - bit 0: TLB miss flag
* - bit 1: initial write
* - bit 2: page invalid
* - bit 3: protection violation
* - bit 4: accessor (0=user 1=kernel)
* - bit 5: 0=read 1=write
* - bit 6-8: page protection spec
* - bit 9: illegal address
* - bit 16: 0=data 1=ins
*
*/
asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long fault_code,
unsigned long address)
{
struct vm_area_struct *vma;
struct task_struct *tsk;
struct mm_struct *mm;
unsigned long page;
siginfo_t info;
int fault;
unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
#ifdef CONFIG_GDBSTUB
/* handle GDB stub causing a fault */
if (gdbstub_busy) {
gdbstub_exception(regs, TBR & TBR_INT_CODE);
return;
}
#endif
#if 0
printk(KERN_DEBUG "--- do_page_fault(%p,%s:%04lx,%08lx)\n",
regs,
fault_code & 0x10000 ? "ins" : "data",
fault_code & 0xffff, address);
#endif
tsk = current;
/*
* 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.
*
* This verifies that the fault happens in kernel space
* and that the fault was a page not present (invalid) error
*/
if (address >= VMALLOC_START && address < VMALLOC_END &&
(fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR &&
(fault_code & MMUFCR_xFC_PGINVAL) == MMUFCR_xFC_PGINVAL
)
goto vmalloc_fault;
mm = tsk->mm;
info.si_code = SEGV_MAPERR;
/*
* If we're in an interrupt or have no user
* context, we must not take the fault..
*/
if (in_atomic() || !mm)
goto no_context;
if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR)
flags |= FAULT_FLAG_USER;
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 ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
/* accessing the stack below the stack pointer is always a
* bug */
if ((address & PAGE_MASK) + 2 * PAGE_SIZE < regs->sp) {
#if 0
printk(KERN_WARNING
"[%d] ### Access below stack @%lx (sp=%lx)\n",
current->pid, address, regs->sp);
printk(KERN_WARNING
"vma [%08x - %08x]\n",
vma->vm_start, vma->vm_end);
show_registers(regs);
printk(KERN_WARNING
"[%d] ### Code: [%08lx]"
" %02x %02x %02x %02x %02x %02x %02x %02x\n",
current->pid,
regs->pc,
((u8 *) regs->pc)[0],
((u8 *) regs->pc)[1],
((u8 *) regs->pc)[2],
((u8 *) regs->pc)[3],
((u8 *) regs->pc)[4],
((u8 *) regs->pc)[5],
((u8 *) regs->pc)[6],
((u8 *) regs->pc)[7]
);
#endif
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:
info.si_code = SEGV_ACCERR;
switch (fault_code & (MMUFCR_xFC_PGINVAL|MMUFCR_xFC_TYPE)) {
default: /* 3: write, present */
case MMUFCR_xFC_TYPE_WRITE:
#ifdef TEST_VERIFY_AREA
if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR)
printk(KERN_DEBUG "WP fault at %08lx\n", regs->pc);
#endif
/* write to absent page */
case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_WRITE:
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
flags |= FAULT_FLAG_WRITE;
break;
/* read from protected page */
case MMUFCR_xFC_TYPE_READ:
goto bad_area;
/* read from absent page present */
case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_READ:
if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
goto bad_area;
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(mm, 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;
vm: add VM_FAULT_SIGSEGV handling support The core VM already knows about VM_FAULT_SIGBUS, but cannot return a "you should SIGSEGV" error, because the SIGSEGV case was generally handled by the caller - usually the architecture fault handler. That results in lots of duplication - all the architecture fault handlers end up doing very similar "look up vma, check permissions, do retries etc" - but it generally works. However, there are cases where the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV. In particular, when accessing the stack guard page, libsigsegv expects a SIGSEGV. And it usually got one, because the stack growth is handled by that duplicated architecture fault handler. However, when the generic VM layer started propagating the error return from the stack expansion in commit fee7e49d4514 ("mm: propagate error from stack expansion even for guard page"), that now exposed the existing VM_FAULT_SIGBUS result to user space. And user space really expected SIGSEGV, not SIGBUS. To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those duplicate architecture fault handlers about it. They all already have the code to handle SIGSEGV, so it's about just tying that new return value to the existing code, but it's all a bit annoying. This is the mindless minimal patch to do this. A more extensive patch would be to try to gather up the mostly shared fault handling logic into one generic helper routine, and long-term we really should do that cleanup. Just from this patch, you can generally see that most architectures just copied (directly or indirectly) the old x86 way of doing things, but in the meantime that original x86 model has been improved to hold the VM semaphore for shorter times etc and to handle VM_FAULT_RETRY and other "newer" things, so it would be a good idea to bring all those improvements to the generic case and teach other architectures about them too. Reported-and-tested-by: Takashi Iwai <tiwai@suse.de> Tested-by: Jan Engelhardt <jengelh@inai.de> Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> # "s390 still compiles and boots" Cc: linux-arch@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-01-30 02:51:32 +08:00
else if (fault & VM_FAULT_SIGSEGV)
goto bad_area;
else if (fault & VM_FAULT_SIGBUS)
goto do_sigbus;
BUG();
}
if (flags & FAULT_FLAG_ALLOW_RETRY) {
if (fault & VM_FAULT_MAJOR)
current->maj_flt++;
else
current->min_flt++;
if (fault & VM_FAULT_RETRY) {
flags &= ~FAULT_FLAG_ALLOW_RETRY;
/* 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);
/* User mode accesses just cause a SIGSEGV */
if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
info.si_signo = SIGSEGV;
info.si_errno = 0;
/* info.si_code has been set above */
info.si_addr = (void *)address;
force_sig_info(SIGSEGV, &info, tsk);
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);
if (address < PAGE_SIZE)
printk(KERN_ALERT
"Unable to handle kernel NULL pointer dereference");
else
printk(KERN_ALERT
"Unable to handle kernel paging request");
printk(" at virtual address %08lx\n", address);
printk(" printing pc:\n");
printk(KERN_ALERT "%08lx\n", regs->pc);
debugger_intercept(fault_code & 0x00010000 ? EXCEP_IAERROR : EXCEP_DAERROR,
SIGSEGV, SEGV_ACCERR, regs);
page = PTBR;
page = ((unsigned long *) __va(page))[address >> 22];
printk(KERN_ALERT "*pde = %08lx\n", page);
if (page & 1) {
page &= PAGE_MASK;
address &= 0x003ff000;
page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
printk(KERN_ALERT "*pte = %08lx\n", page);
}
die("Oops", regs, fault_code);
do_exit(SIGKILL);
/*
* 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 ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
pagefault_out_of_memory();
return;
}
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 = (void *)address;
force_sig_info(SIGBUS, &info, tsk);
/* Kernel mode? Handle exceptions or die */
if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR)
goto no_context;
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 index = pgd_index(address);
pgd_t *pgd, *pgd_k;
pud_t *pud, *pud_k;
pmd_t *pmd, *pmd_k;
pte_t *pte_k;
pgd_k = init_mm.pgd + index;
if (!pgd_present(*pgd_k))
goto no_context;
pud_k = pud_offset(pgd_k, address);
if (!pud_present(*pud_k))
goto no_context;
pmd_k = pmd_offset(pud_k, address);
if (!pmd_present(*pmd_k))
goto no_context;
pgd = (pgd_t *) PTBR + index;
pud = pud_offset(pgd, address);
pmd = pmd_offset(pud, address);
set_pmd(pmd, *pmd_k);
pte_k = pte_offset_kernel(pmd_k, address);
if (!pte_present(*pte_k))
goto no_context;
return;
}
}