forked from luck/tmp_suning_uos_patched
eeabac7386
In order to handle all of the cases of address calculation overflow properly, we run sparc 32-bit processes in "address masking" mode when running on a 64-bit kernel. Address masking mode zeros out the top 32-bits of the address calculated for every load and store instruction. However, when we're in privileged mode we have to run with that address masking mode disabled even when accessing userspace from the kernel. To "simulate" the address masking mode we clear the top-bits by hand for 32-bit processes in the fault handler. It is the responsibility of code in the compat layer to properly zero extend addresses used to access userspace. If this isn't followed properly we can get into a fault loop. Say that the user address is 0xf0000000 but for whatever reason the kernel code sign extends this to 64-bit, and then the kernel tries to access the result. In such a case we'll fault on address 0xfffffffff0000000 but the fault handler will process that fault as if it were to address 0xf0000000. We'll loop faulting forever because the fault never gets satisfied. So add a check specifically for this case, when the kernel is faulting on a user address access and the addresses don't match up. This code path is sufficiently slow path, and this bug is sufficiently painful to diagnose, that this kind of bug check is warranted. Signed-off-by: David S. Miller <davem@davemloft.net>
452 lines
12 KiB
C
452 lines
12 KiB
C
/*
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* arch/sparc64/mm/fault.c: Page fault handlers for the 64-bit Sparc.
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*
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* Copyright (C) 1996, 2008 David S. Miller (davem@davemloft.net)
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* Copyright (C) 1997, 1999 Jakub Jelinek (jj@ultra.linux.cz)
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*/
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#include <asm/head.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/sched.h>
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#include <linux/ptrace.h>
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#include <linux/mman.h>
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#include <linux/signal.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/kprobes.h>
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#include <linux/kdebug.h>
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#include <linux/percpu.h>
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#include <asm/page.h>
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#include <asm/pgtable.h>
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#include <asm/openprom.h>
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#include <asm/oplib.h>
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#include <asm/uaccess.h>
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#include <asm/asi.h>
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#include <asm/lsu.h>
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#include <asm/sections.h>
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#include <asm/mmu_context.h>
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#ifdef CONFIG_KPROBES
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static inline int notify_page_fault(struct pt_regs *regs)
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{
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int ret = 0;
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/* kprobe_running() needs smp_processor_id() */
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if (!user_mode(regs)) {
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preempt_disable();
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if (kprobe_running() && kprobe_fault_handler(regs, 0))
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ret = 1;
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preempt_enable();
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}
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return ret;
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}
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#else
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static inline int notify_page_fault(struct pt_regs *regs)
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{
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return 0;
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}
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#endif
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static void __kprobes unhandled_fault(unsigned long address,
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struct task_struct *tsk,
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struct pt_regs *regs)
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{
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if ((unsigned long) address < PAGE_SIZE) {
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printk(KERN_ALERT "Unable to handle kernel NULL "
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"pointer dereference\n");
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} else {
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printk(KERN_ALERT "Unable to handle kernel paging request "
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"at virtual address %016lx\n", (unsigned long)address);
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}
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printk(KERN_ALERT "tsk->{mm,active_mm}->context = %016lx\n",
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(tsk->mm ?
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CTX_HWBITS(tsk->mm->context) :
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CTX_HWBITS(tsk->active_mm->context)));
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printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %016lx\n",
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(tsk->mm ? (unsigned long) tsk->mm->pgd :
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(unsigned long) tsk->active_mm->pgd));
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die_if_kernel("Oops", regs);
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}
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static void bad_kernel_pc(struct pt_regs *regs, unsigned long vaddr)
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{
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printk(KERN_CRIT "OOPS: Bogus kernel PC [%016lx] in fault handler\n",
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regs->tpc);
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printk(KERN_CRIT "OOPS: RPC [%016lx]\n", regs->u_regs[15]);
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printk("OOPS: RPC <%pS>\n", (void *) regs->u_regs[15]);
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printk(KERN_CRIT "OOPS: Fault was to vaddr[%lx]\n", vaddr);
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dump_stack();
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unhandled_fault(regs->tpc, current, regs);
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}
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/*
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* We now make sure that mmap_sem is held in all paths that call
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* this. Additionally, to prevent kswapd from ripping ptes from
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* under us, raise interrupts around the time that we look at the
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* pte, kswapd will have to wait to get his smp ipi response from
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* us. vmtruncate likewise. This saves us having to get pte lock.
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*/
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static unsigned int get_user_insn(unsigned long tpc)
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{
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pgd_t *pgdp = pgd_offset(current->mm, tpc);
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pud_t *pudp;
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pmd_t *pmdp;
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pte_t *ptep, pte;
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unsigned long pa;
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u32 insn = 0;
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unsigned long pstate;
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if (pgd_none(*pgdp))
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goto outret;
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pudp = pud_offset(pgdp, tpc);
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if (pud_none(*pudp))
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goto outret;
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pmdp = pmd_offset(pudp, tpc);
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if (pmd_none(*pmdp))
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goto outret;
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/* This disables preemption for us as well. */
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__asm__ __volatile__("rdpr %%pstate, %0" : "=r" (pstate));
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__asm__ __volatile__("wrpr %0, %1, %%pstate"
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: : "r" (pstate), "i" (PSTATE_IE));
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ptep = pte_offset_map(pmdp, tpc);
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pte = *ptep;
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if (!pte_present(pte))
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goto out;
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pa = (pte_pfn(pte) << PAGE_SHIFT);
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pa += (tpc & ~PAGE_MASK);
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/* Use phys bypass so we don't pollute dtlb/dcache. */
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__asm__ __volatile__("lduwa [%1] %2, %0"
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: "=r" (insn)
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: "r" (pa), "i" (ASI_PHYS_USE_EC));
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out:
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pte_unmap(ptep);
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__asm__ __volatile__("wrpr %0, 0x0, %%pstate" : : "r" (pstate));
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outret:
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return insn;
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}
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extern unsigned long compute_effective_address(struct pt_regs *, unsigned int, unsigned int);
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static void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
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unsigned int insn, int fault_code)
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{
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siginfo_t info;
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info.si_code = code;
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info.si_signo = sig;
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info.si_errno = 0;
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if (fault_code & FAULT_CODE_ITLB)
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info.si_addr = (void __user *) regs->tpc;
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else
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info.si_addr = (void __user *)
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compute_effective_address(regs, insn, 0);
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info.si_trapno = 0;
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force_sig_info(sig, &info, current);
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}
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extern int handle_ldf_stq(u32, struct pt_regs *);
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extern int handle_ld_nf(u32, struct pt_regs *);
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static unsigned int get_fault_insn(struct pt_regs *regs, unsigned int insn)
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{
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if (!insn) {
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if (!regs->tpc || (regs->tpc & 0x3))
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return 0;
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if (regs->tstate & TSTATE_PRIV) {
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insn = *(unsigned int *) regs->tpc;
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} else {
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insn = get_user_insn(regs->tpc);
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}
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}
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return insn;
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}
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static void do_kernel_fault(struct pt_regs *regs, int si_code, int fault_code,
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unsigned int insn, unsigned long address)
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{
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unsigned char asi = ASI_P;
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if ((!insn) && (regs->tstate & TSTATE_PRIV))
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goto cannot_handle;
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/* If user insn could be read (thus insn is zero), that
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* is fine. We will just gun down the process with a signal
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* in that case.
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*/
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if (!(fault_code & (FAULT_CODE_WRITE|FAULT_CODE_ITLB)) &&
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(insn & 0xc0800000) == 0xc0800000) {
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if (insn & 0x2000)
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asi = (regs->tstate >> 24);
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else
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asi = (insn >> 5);
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if ((asi & 0xf2) == 0x82) {
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if (insn & 0x1000000) {
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handle_ldf_stq(insn, regs);
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} else {
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/* This was a non-faulting load. Just clear the
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* destination register(s) and continue with the next
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* instruction. -jj
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*/
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handle_ld_nf(insn, regs);
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}
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return;
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}
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}
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/* Is this in ex_table? */
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if (regs->tstate & TSTATE_PRIV) {
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const struct exception_table_entry *entry;
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entry = search_exception_tables(regs->tpc);
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if (entry) {
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regs->tpc = entry->fixup;
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regs->tnpc = regs->tpc + 4;
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return;
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}
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} else {
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/* The si_code was set to make clear whether
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* this was a SEGV_MAPERR or SEGV_ACCERR fault.
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*/
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do_fault_siginfo(si_code, SIGSEGV, regs, insn, fault_code);
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return;
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}
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cannot_handle:
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unhandled_fault (address, current, regs);
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}
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asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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unsigned int insn = 0;
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int si_code, fault_code, fault;
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unsigned long address, mm_rss;
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fault_code = get_thread_fault_code();
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if (notify_page_fault(regs))
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return;
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si_code = SEGV_MAPERR;
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address = current_thread_info()->fault_address;
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if ((fault_code & FAULT_CODE_ITLB) &&
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(fault_code & FAULT_CODE_DTLB))
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BUG();
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if (test_thread_flag(TIF_32BIT)) {
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if (!(regs->tstate & TSTATE_PRIV))
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regs->tpc &= 0xffffffff;
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address &= 0xffffffff;
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}
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if (regs->tstate & TSTATE_PRIV) {
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unsigned long eaddr, tpc = regs->tpc;
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/* Sanity check the PC. */
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if ((tpc >= KERNBASE && tpc < (unsigned long) __init_end) ||
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(tpc >= MODULES_VADDR && tpc < MODULES_END)) {
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/* Valid, no problems... */
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} else {
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bad_kernel_pc(regs, address);
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return;
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}
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insn = get_fault_insn(regs, insn);
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eaddr = compute_effective_address(regs, insn, 0);
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if (WARN_ON_ONCE((eaddr & PAGE_MASK) != (address & PAGE_MASK))){
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printk(KERN_ERR "FAULT: Mismatch kernel fault "
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"address: addr[%lx] eaddr[%lx] TPC[%lx]\n",
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address, eaddr, tpc);
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show_regs(regs);
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goto handle_kernel_fault;
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}
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}
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/*
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* If we're in an interrupt or have no user
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* context, we must not take the fault..
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*/
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if (in_atomic() || !mm)
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goto intr_or_no_mm;
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if (!down_read_trylock(&mm->mmap_sem)) {
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if ((regs->tstate & TSTATE_PRIV) &&
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!search_exception_tables(regs->tpc)) {
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insn = get_fault_insn(regs, insn);
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goto handle_kernel_fault;
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}
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down_read(&mm->mmap_sem);
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}
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vma = find_vma(mm, address);
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if (!vma)
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goto bad_area;
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/* Pure DTLB misses do not tell us whether the fault causing
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* load/store/atomic was a write or not, it only says that there
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* was no match. So in such a case we (carefully) read the
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* instruction to try and figure this out. It's an optimization
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* so it's ok if we can't do this.
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*
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* Special hack, window spill/fill knows the exact fault type.
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*/
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if (((fault_code &
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(FAULT_CODE_DTLB | FAULT_CODE_WRITE | FAULT_CODE_WINFIXUP)) == FAULT_CODE_DTLB) &&
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(vma->vm_flags & VM_WRITE) != 0) {
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insn = get_fault_insn(regs, 0);
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if (!insn)
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goto continue_fault;
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/* All loads, stores and atomics have bits 30 and 31 both set
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* in the instruction. Bit 21 is set in all stores, but we
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* have to avoid prefetches which also have bit 21 set.
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*/
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if ((insn & 0xc0200000) == 0xc0200000 &&
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(insn & 0x01780000) != 0x01680000) {
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/* Don't bother updating thread struct value,
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* because update_mmu_cache only cares which tlb
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* the access came from.
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*/
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fault_code |= FAULT_CODE_WRITE;
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}
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}
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continue_fault:
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if (vma->vm_start <= address)
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goto good_area;
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if (!(vma->vm_flags & VM_GROWSDOWN))
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goto bad_area;
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if (!(fault_code & FAULT_CODE_WRITE)) {
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/* Non-faulting loads shouldn't expand stack. */
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insn = get_fault_insn(regs, insn);
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if ((insn & 0xc0800000) == 0xc0800000) {
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unsigned char asi;
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if (insn & 0x2000)
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asi = (regs->tstate >> 24);
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else
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asi = (insn >> 5);
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if ((asi & 0xf2) == 0x82)
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goto bad_area;
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}
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}
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if (expand_stack(vma, address))
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goto bad_area;
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/*
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* Ok, we have a good vm_area for this memory access, so
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* we can handle it..
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*/
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good_area:
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si_code = SEGV_ACCERR;
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/* If we took a ITLB miss on a non-executable page, catch
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* that here.
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*/
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if ((fault_code & FAULT_CODE_ITLB) && !(vma->vm_flags & VM_EXEC)) {
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BUG_ON(address != regs->tpc);
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BUG_ON(regs->tstate & TSTATE_PRIV);
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goto bad_area;
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}
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if (fault_code & FAULT_CODE_WRITE) {
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if (!(vma->vm_flags & VM_WRITE))
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goto bad_area;
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/* Spitfire has an icache which does not snoop
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* processor stores. Later processors do...
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*/
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if (tlb_type == spitfire &&
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(vma->vm_flags & VM_EXEC) != 0 &&
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vma->vm_file != NULL)
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set_thread_fault_code(fault_code |
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FAULT_CODE_BLKCOMMIT);
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} else {
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/* Allow reads even for write-only mappings */
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if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
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goto bad_area;
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}
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fault = handle_mm_fault(mm, vma, address, (fault_code & FAULT_CODE_WRITE));
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if (unlikely(fault & VM_FAULT_ERROR)) {
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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 do_sigbus;
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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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mm_rss = get_mm_rss(mm);
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#ifdef CONFIG_HUGETLB_PAGE
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mm_rss -= (mm->context.huge_pte_count * (HPAGE_SIZE / PAGE_SIZE));
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#endif
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if (unlikely(mm_rss >
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mm->context.tsb_block[MM_TSB_BASE].tsb_rss_limit))
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tsb_grow(mm, MM_TSB_BASE, mm_rss);
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#ifdef CONFIG_HUGETLB_PAGE
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mm_rss = mm->context.huge_pte_count;
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if (unlikely(mm_rss >
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mm->context.tsb_block[MM_TSB_HUGE].tsb_rss_limit))
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tsb_grow(mm, MM_TSB_HUGE, mm_rss);
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#endif
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return;
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/*
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* Something tried to access memory that isn't in our memory map..
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* Fix it, but check if it's kernel or user first..
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*/
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bad_area:
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insn = get_fault_insn(regs, insn);
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up_read(&mm->mmap_sem);
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handle_kernel_fault:
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do_kernel_fault(regs, si_code, fault_code, insn, address);
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return;
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/*
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* We ran out of memory, or some other thing happened to us that made
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* us unable to handle the page fault gracefully.
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*/
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out_of_memory:
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insn = get_fault_insn(regs, insn);
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up_read(&mm->mmap_sem);
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printk("VM: killing process %s\n", current->comm);
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if (!(regs->tstate & TSTATE_PRIV))
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do_group_exit(SIGKILL);
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goto handle_kernel_fault;
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intr_or_no_mm:
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insn = get_fault_insn(regs, 0);
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goto handle_kernel_fault;
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do_sigbus:
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insn = get_fault_insn(regs, insn);
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up_read(&mm->mmap_sem);
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/*
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* Send a sigbus, regardless of whether we were in kernel
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* or user mode.
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*/
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do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, insn, fault_code);
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/* Kernel mode? Handle exceptions or die */
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if (regs->tstate & TSTATE_PRIV)
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goto handle_kernel_fault;
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}
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