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![Kyle McMartin](/assets/img/avatar_default.png)
On Wed, Dec 17, 2008 at 11:46:05PM +0100, Helge Deller wrote: > Honestly, I can't decide whether to apply this. It really should never happen in the kernel, since the kernel can guarantee it won't get the access rights failure (highest privilege level, and can set %sr and %protid to whatever it wants.) It really genuinely is a bug that probably should panic the kernel. The only precedent I can easily see is x86 fixing up a bad iret with a general protection fault, which is more or less analogous to code 27 here. On the other hand, taking the exception on a userspace access really isn't all that critical, and there's fundamentally little reason for the kernel not to SIGSEGV the process, and continue... Argh. (btw, I've instrumented my do_sys_poll with a pile of assertions that %cr8 << 1 == %sr3 == current->mm.context... let's see if where we're getting corrupted is deterministic, though, I would guess that it won't be.) Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>
272 lines
7 KiB
C
272 lines
7 KiB
C
/* $Id: fault.c,v 1.5 2000/01/26 16:20:29 jsm Exp $
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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*
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* Copyright (C) 1995, 1996, 1997, 1998 by Ralf Baechle
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* Copyright 1999 SuSE GmbH (Philipp Rumpf, prumpf@tux.org)
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* Copyright 1999 Hewlett Packard Co.
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*
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*/
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#include <linux/mm.h>
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#include <linux/ptrace.h>
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#include <linux/sched.h>
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#include <linux/interrupt.h>
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#include <linux/module.h>
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#include <asm/uaccess.h>
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#include <asm/traps.h>
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#define PRINT_USER_FAULTS /* (turn this on if you want user faults to be */
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/* dumped to the console via printk) */
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/* Various important other fields */
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#define bit22set(x) (x & 0x00000200)
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#define bits23_25set(x) (x & 0x000001c0)
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#define isGraphicsFlushRead(x) ((x & 0xfc003fdf) == 0x04001a80)
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/* extended opcode is 0x6a */
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#define BITSSET 0x1c0 /* for identifying LDCW */
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DEFINE_PER_CPU(struct exception_data, exception_data);
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/*
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* parisc_acctyp(unsigned int inst) --
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* Given a PA-RISC memory access instruction, determine if the
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* the instruction would perform a memory read or memory write
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* operation.
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*
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* This function assumes that the given instruction is a memory access
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* instruction (i.e. you should really only call it if you know that
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* the instruction has generated some sort of a memory access fault).
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*
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* Returns:
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* VM_READ if read operation
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* VM_WRITE if write operation
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* VM_EXEC if execute operation
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*/
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static unsigned long
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parisc_acctyp(unsigned long code, unsigned int inst)
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{
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if (code == 6 || code == 16)
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return VM_EXEC;
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switch (inst & 0xf0000000) {
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case 0x40000000: /* load */
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case 0x50000000: /* new load */
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return VM_READ;
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case 0x60000000: /* store */
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case 0x70000000: /* new store */
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return VM_WRITE;
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case 0x20000000: /* coproc */
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case 0x30000000: /* coproc2 */
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if (bit22set(inst))
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return VM_WRITE;
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case 0x0: /* indexed/memory management */
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if (bit22set(inst)) {
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/*
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* Check for the 'Graphics Flush Read' instruction.
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* It resembles an FDC instruction, except for bits
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* 20 and 21. Any combination other than zero will
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* utilize the block mover functionality on some
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* older PA-RISC platforms. The case where a block
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* move is performed from VM to graphics IO space
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* should be treated as a READ.
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*
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* The significance of bits 20,21 in the FDC
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* instruction is:
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*
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* 00 Flush data cache (normal instruction behavior)
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* 01 Graphics flush write (IO space -> VM)
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* 10 Graphics flush read (VM -> IO space)
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* 11 Graphics flush read/write (VM <-> IO space)
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*/
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if (isGraphicsFlushRead(inst))
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return VM_READ;
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return VM_WRITE;
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} else {
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/*
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* Check for LDCWX and LDCWS (semaphore instructions).
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* If bits 23 through 25 are all 1's it is one of
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* the above two instructions and is a write.
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*
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* Note: With the limited bits we are looking at,
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* this will also catch PROBEW and PROBEWI. However,
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* these should never get in here because they don't
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* generate exceptions of the type:
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* Data TLB miss fault/data page fault
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* Data memory protection trap
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*/
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if (bits23_25set(inst) == BITSSET)
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return VM_WRITE;
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}
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return VM_READ; /* Default */
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}
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return VM_READ; /* Default */
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}
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#undef bit22set
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#undef bits23_25set
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#undef isGraphicsFlushRead
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#undef BITSSET
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#if 0
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/* This is the treewalk to find a vma which is the highest that has
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* a start < addr. We're using find_vma_prev instead right now, but
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* we might want to use this at some point in the future. Probably
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* not, but I want it committed to CVS so I don't lose it :-)
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*/
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while (tree != vm_avl_empty) {
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if (tree->vm_start > addr) {
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tree = tree->vm_avl_left;
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} else {
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prev = tree;
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if (prev->vm_next == NULL)
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break;
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if (prev->vm_next->vm_start > addr)
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break;
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tree = tree->vm_avl_right;
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}
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}
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#endif
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int fixup_exception(struct pt_regs *regs)
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{
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const struct exception_table_entry *fix;
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fix = search_exception_tables(regs->iaoq[0]);
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if (fix) {
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struct exception_data *d;
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d = &__get_cpu_var(exception_data);
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d->fault_ip = regs->iaoq[0];
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d->fault_space = regs->isr;
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d->fault_addr = regs->ior;
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regs->iaoq[0] = ((fix->fixup) & ~3);
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/*
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* NOTE: In some cases the faulting instruction
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* may be in the delay slot of a branch. We
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* don't want to take the branch, so we don't
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* increment iaoq[1], instead we set it to be
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* iaoq[0]+4, and clear the B bit in the PSW
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*/
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regs->iaoq[1] = regs->iaoq[0] + 4;
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regs->gr[0] &= ~PSW_B; /* IPSW in gr[0] */
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return 1;
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}
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return 0;
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}
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void do_page_fault(struct pt_regs *regs, unsigned long code,
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unsigned long address)
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{
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struct vm_area_struct *vma, *prev_vma;
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struct task_struct *tsk = current;
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struct mm_struct *mm = tsk->mm;
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unsigned long acc_type;
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int fault;
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if (in_atomic() || !mm)
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goto no_context;
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down_read(&mm->mmap_sem);
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vma = find_vma_prev(mm, address, &prev_vma);
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if (!vma || address < vma->vm_start)
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goto check_expansion;
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/*
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* Ok, we have a good vm_area for this memory access. We still need to
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* check the access permissions.
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*/
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good_area:
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acc_type = parisc_acctyp(code,regs->iir);
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if ((vma->vm_flags & acc_type) != acc_type)
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goto bad_area;
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/*
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* If for any reason at all we couldn't handle the fault, make
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* sure we exit gracefully rather than endlessly redo the
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* fault.
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*/
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fault = handle_mm_fault(mm, vma, address, (acc_type & VM_WRITE) != 0);
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if (unlikely(fault & VM_FAULT_ERROR)) {
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/*
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* We hit a shared mapping outside of the file, or some
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* other thing happened to us that made us unable to
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* handle the page fault gracefully.
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*/
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if (fault & VM_FAULT_OOM)
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goto out_of_memory;
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else if (fault & VM_FAULT_SIGBUS)
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goto bad_area;
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BUG();
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}
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if (fault & VM_FAULT_MAJOR)
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current->maj_flt++;
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else
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current->min_flt++;
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up_read(&mm->mmap_sem);
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return;
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check_expansion:
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vma = prev_vma;
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if (vma && (expand_stack(vma, address) == 0))
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goto good_area;
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/*
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* Something tried to access memory that isn't in our memory map..
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*/
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bad_area:
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up_read(&mm->mmap_sem);
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if (user_mode(regs)) {
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struct siginfo si;
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#ifdef PRINT_USER_FAULTS
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printk(KERN_DEBUG "\n");
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printk(KERN_DEBUG "do_page_fault() pid=%d command='%s' type=%lu address=0x%08lx\n",
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task_pid_nr(tsk), tsk->comm, code, address);
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if (vma) {
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printk(KERN_DEBUG "vm_start = 0x%08lx, vm_end = 0x%08lx\n",
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vma->vm_start, vma->vm_end);
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}
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show_regs(regs);
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#endif
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/* FIXME: actually we need to get the signo and code correct */
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si.si_signo = SIGSEGV;
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si.si_errno = 0;
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si.si_code = SEGV_MAPERR;
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si.si_addr = (void __user *) address;
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force_sig_info(SIGSEGV, &si, current);
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return;
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}
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no_context:
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if (!user_mode(regs) && fixup_exception(regs)) {
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return;
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}
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parisc_terminate("Bad Address (null pointer deref?)", regs, code, address);
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out_of_memory:
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up_read(&mm->mmap_sem);
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printk(KERN_CRIT "VM: killing process %s\n", current->comm);
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if (user_mode(regs))
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do_group_exit(SIGKILL);
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goto no_context;
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}
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