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linux/arch/frv/mm/fault.c
Linus Torvalds 33692f2759 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 fee7e49d45 ("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>
2015-01-29 10:51:32 -08:00

330 lines
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/*
* linux/arch/frv/mm/fault.c
*
* Copyright (C) 2003 Red Hat, Inc. All Rights Reserved.
* - Written by David Howells (dhowells@redhat.com)
* - Derived from arch/m68knommu/mm/fault.c
* - Copyright (C) 1998 D. Jeff Dionne <jeff@lineo.ca>,
* - Copyright (C) 2000 Lineo, Inc. (www.lineo.com)
*
* Based on:
*
* linux/arch/m68k/mm/fault.c
*
* Copyright (C) 1995 Hamish Macdonald
*/
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/hardirq.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/gdb-stub.h>
/*****************************************************************************/
/*
* This routine handles page faults. It determines the problem, and
* then passes it off to one of the appropriate routines.
*/
asmlinkage void do_page_fault(int datammu, unsigned long esr0, unsigned long ear0)
{
struct vm_area_struct *vma;
struct mm_struct *mm;
unsigned long _pme, lrai, lrad, fixup;
unsigned long flags = 0;
siginfo_t info;
pgd_t *pge;
pud_t *pue;
pte_t *pte;
int fault;
#if 0
const char *atxc[16] = {
[0x0] = "mmu-miss", [0x8] = "multi-dat", [0x9] = "multi-sat",
[0xa] = "tlb-miss", [0xc] = "privilege", [0xd] = "write-prot",
};
printk("do_page_fault(%d,%lx [%s],%lx)\n",
datammu, esr0, atxc[esr0 >> 20 & 0xf], ear0);
#endif
mm = current->mm;
/*
* 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 (!user_mode(__frame) && (esr0 & ESR0_ATXC) == ESR0_ATXC_AMRTLB_MISS) {
if (ear0 >= VMALLOC_START && ear0 < VMALLOC_END)
goto kernel_pte_fault;
if (ear0 >= PKMAP_BASE && ear0 < PKMAP_END)
goto kernel_pte_fault;
}
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 (user_mode(__frame))
flags |= FAULT_FLAG_USER;
down_read(&mm->mmap_sem);
vma = find_vma(mm, ear0);
if (!vma)
goto bad_area;
if (vma->vm_start <= ear0)
goto good_area;
if (!(vma->vm_flags & VM_GROWSDOWN))
goto bad_area;
if (user_mode(__frame)) {
/*
* accessing the stack below %esp is always a bug.
* The "+ 32" is there due to some instructions (like
* pusha) doing post-decrement on the stack and that
* doesn't show up until later..
*/
if ((ear0 & PAGE_MASK) + 2 * PAGE_SIZE < __frame->sp) {
#if 0
printk("[%d] ### Access below stack @%lx (sp=%lx)\n",
current->pid, ear0, __frame->sp);
show_registers(__frame);
printk("[%d] ### Code: [%08lx] %02x %02x %02x %02x %02x %02x %02x %02x\n",
current->pid,
__frame->pc,
((u8*)__frame->pc)[0],
((u8*)__frame->pc)[1],
((u8*)__frame->pc)[2],
((u8*)__frame->pc)[3],
((u8*)__frame->pc)[4],
((u8*)__frame->pc)[5],
((u8*)__frame->pc)[6],
((u8*)__frame->pc)[7]
);
#endif
goto bad_area;
}
}
if (expand_stack(vma, ear0))
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 (esr0 & ESR0_ATXC) {
default:
/* handle write to write protected page */
case ESR0_ATXC_WP_EXCEP:
#ifdef TEST_VERIFY_AREA
if (!(user_mode(__frame)))
printk("WP fault at %08lx\n", __frame->pc);
#endif
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
flags |= FAULT_FLAG_WRITE;
break;
/* handle read from protected page */
case ESR0_ATXC_PRIV_EXCEP:
goto bad_area;
/* handle read, write or exec on absent page
* - can't support write without permitting read
* - don't support execute without permitting read and vice-versa
*/
case ESR0_ATXC_AMRTLB_MISS:
if (!(vma->vm_flags & (VM_READ | VM_WRITE | 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, ear0, flags);
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_MAJOR)
current->maj_flt++;
else
current->min_flt++;
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 (user_mode(__frame)) {
info.si_signo = SIGSEGV;
info.si_errno = 0;
/* info.si_code has been set above */
info.si_addr = (void *) ear0;
force_sig_info(SIGSEGV, &info, current);
return;
}
no_context:
/* are we prepared to handle this kernel fault? */
if ((fixup = search_exception_table(__frame->pc)) != 0) {
__frame->pc = fixup;
return;
}
/*
* Oops. The kernel tried to access some bad page. We'll have to
* terminate things with extreme prejudice.
*/
bust_spinlocks(1);
if (ear0 < 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 addr %08lx\n", ear0);
printk(" PC : %08lx\n", __frame->pc);
printk(" EXC : esr0=%08lx ear0=%08lx\n", esr0, ear0);
asm("lrai %1,%0,#1,#0,#0" : "=&r"(lrai) : "r"(ear0));
asm("lrad %1,%0,#1,#0,#0" : "=&r"(lrad) : "r"(ear0));
printk(KERN_ALERT " LRAI: %08lx\n", lrai);
printk(KERN_ALERT " LRAD: %08lx\n", lrad);
__break_hijack_kernel_event();
pge = pgd_offset(current->mm, ear0);
pue = pud_offset(pge, ear0);
_pme = pue->pue[0].ste[0];
printk(KERN_ALERT " PGE : %8p { PME %08lx }\n", pge, _pme);
if (_pme & xAMPRx_V) {
unsigned long dampr, damlr, val;
asm volatile("movsg dampr2,%0 ! movgs %2,dampr2 ! movsg damlr2,%1"
: "=&r"(dampr), "=r"(damlr)
: "r" (_pme | xAMPRx_L|xAMPRx_SS_16Kb|xAMPRx_S|xAMPRx_C|xAMPRx_V)
);
pte = (pte_t *) damlr + __pte_index(ear0);
val = pte_val(*pte);
asm volatile("movgs %0,dampr2" :: "r" (dampr));
printk(KERN_ALERT " PTE : %8p { %08lx }\n", pte, val);
}
die_if_kernel("Oops\n");
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 (!user_mode(__frame))
goto no_context;
pagefault_out_of_memory();
return;
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 *) ear0;
force_sig_info(SIGBUS, &info, current);
/* Kernel mode? Handle exceptions or die */
if (!user_mode(__frame))
goto no_context;
return;
/*
* The fault was caused by a kernel PTE (such as installed by vmalloc or kmap)
*/
kernel_pte_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(ear0);
pgd_t *pgd, *pgd_k;
pud_t *pud, *pud_k;
pmd_t *pmd, *pmd_k;
pte_t *pte_k;
pgd = (pgd_t *) __get_TTBR();
pgd = (pgd_t *)__va(pgd) + index;
pgd_k = ((pgd_t *)(init_mm.pgd)) + index;
if (!pgd_present(*pgd_k))
goto no_context;
//set_pgd(pgd, *pgd_k); /////// gcc ICE's on this line
pud_k = pud_offset(pgd_k, ear0);
if (!pud_present(*pud_k))
goto no_context;
pmd_k = pmd_offset(pud_k, ear0);
if (!pmd_present(*pmd_k))
goto no_context;
pud = pud_offset(pgd, ear0);
pmd = pmd_offset(pud, ear0);
set_pmd(pmd, *pmd_k);
pte_k = pte_offset_kernel(pmd_k, ear0);
if (!pte_present(*pte_k))
goto no_context;
return;
}
} /* end do_page_fault() */
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