mmap locking API: convert mmap_sem comments

[thirdparty/linux.git] / arch / sparc / mm / fault_64.c

// SPDX-License-Identifier: GPL-2.0
/*
 * arch/sparc64/mm/fault.c: Page fault handlers for the 64-bit Sparc.
 *
 * Copyright (C) 1996, 2008 David S. Miller (davem@davemloft.net)
 * Copyright (C) 1997, 1999 Jakub Jelinek (jj@ultra.linux.cz)
 */

#include <asm/head.h>

#include <linux/string.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/signal.h>
#include <linux/mm.h>
#include <linux/extable.h>
#include <linux/init.h>
#include <linux/perf_event.h>
#include <linux/interrupt.h>
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/percpu.h>
#include <linux/context_tracking.h>
#include <linux/uaccess.h>

#include <asm/page.h>
#include <asm/openprom.h>
#include <asm/oplib.h>
#include <asm/asi.h>
#include <asm/lsu.h>
#include <asm/sections.h>
#include <asm/mmu_context.h>
#include <asm/setup.h>

int show_unhandled_signals = 1;

static void __kprobes unhandled_fault(unsigned long address,
                                      struct task_struct *tsk,
                                      struct pt_regs *regs)
{
        if ((unsigned long) address < PAGE_SIZE) {
                printk(KERN_ALERT "Unable to handle kernel NULL "
                       "pointer dereference\n");
        } else {
                printk(KERN_ALERT "Unable to handle kernel paging request "
                       "at virtual address %016lx\n", (unsigned long)address);
        }
        printk(KERN_ALERT "tsk->{mm,active_mm}->context = %016lx\n",
               (tsk->mm ?
                CTX_HWBITS(tsk->mm->context) :
                CTX_HWBITS(tsk->active_mm->context)));
        printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %016lx\n",
               (tsk->mm ? (unsigned long) tsk->mm->pgd :
                          (unsigned long) tsk->active_mm->pgd));
        die_if_kernel("Oops", regs);
}

static void __kprobes bad_kernel_pc(struct pt_regs *regs, unsigned long vaddr)
{
        printk(KERN_CRIT "OOPS: Bogus kernel PC [%016lx] in fault handler\n",
               regs->tpc);
        printk(KERN_CRIT "OOPS: RPC [%016lx]\n", regs->u_regs[15]);
        printk("OOPS: RPC <%pS>\n", (void *) regs->u_regs[15]);
        printk(KERN_CRIT "OOPS: Fault was to vaddr[%lx]\n", vaddr);
        dump_stack();
        unhandled_fault(regs->tpc, current, regs);
}

/*
 * We now make sure that mmap_lock is held in all paths that call
 * this. Additionally, to prevent kswapd from ripping ptes from
 * under us, raise interrupts around the time that we look at the
 * pte, kswapd will have to wait to get his smp ipi response from
 * us. vmtruncate likewise. This saves us having to get pte lock.
 */
static unsigned int get_user_insn(unsigned long tpc)
{
        pgd_t *pgdp = pgd_offset(current->mm, tpc);
        p4d_t *p4dp;
        pud_t *pudp;
        pmd_t *pmdp;
        pte_t *ptep, pte;
        unsigned long pa;
        u32 insn = 0;

        if (pgd_none(*pgdp) || unlikely(pgd_bad(*pgdp)))
                goto out;
        p4dp = p4d_offset(pgdp, tpc);
        if (p4d_none(*p4dp) || unlikely(p4d_bad(*p4dp)))
                goto out;
        pudp = pud_offset(p4dp, tpc);
        if (pud_none(*pudp) || unlikely(pud_bad(*pudp)))
                goto out;

        /* This disables preemption for us as well. */
        local_irq_disable();

        pmdp = pmd_offset(pudp, tpc);
        if (pmd_none(*pmdp) || unlikely(pmd_bad(*pmdp)))
                goto out_irq_enable;

#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
        if (is_hugetlb_pmd(*pmdp)) {
                pa  = pmd_pfn(*pmdp) << PAGE_SHIFT;
                pa += tpc & ~HPAGE_MASK;

                /* Use phys bypass so we don't pollute dtlb/dcache. */
                __asm__ __volatile__("lduwa [%1] %2, %0"
                                     : "=r" (insn)
                                     : "r" (pa), "i" (ASI_PHYS_USE_EC));
        } else
#endif
        {
                ptep = pte_offset_map(pmdp, tpc);
                pte = *ptep;
                if (pte_present(pte)) {
                        pa  = (pte_pfn(pte) << PAGE_SHIFT);
                        pa += (tpc & ~PAGE_MASK);

                        /* Use phys bypass so we don't pollute dtlb/dcache. */
                        __asm__ __volatile__("lduwa [%1] %2, %0"
                                             : "=r" (insn)
                                             : "r" (pa), "i" (ASI_PHYS_USE_EC));
                }
                pte_unmap(ptep);
        }
out_irq_enable:
        local_irq_enable();
out:
        return insn;
}

static inline void
show_signal_msg(struct pt_regs *regs, int sig, int code,
                unsigned long address, struct task_struct *tsk)
{
        if (!unhandled_signal(tsk, sig))
                return;

        if (!printk_ratelimit())
                return;

        printk("%s%s[%d]: segfault at %lx ip %px (rpc %px) sp %px error %x",
               task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
               tsk->comm, task_pid_nr(tsk), address,
               (void *)regs->tpc, (void *)regs->u_regs[UREG_I7],
               (void *)regs->u_regs[UREG_FP], code);

        print_vma_addr(KERN_CONT " in ", regs->tpc);

        printk(KERN_CONT "\n");
}

static void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
                             unsigned long fault_addr, unsigned int insn,
                             int fault_code)
{
        unsigned long addr;

        if (fault_code & FAULT_CODE_ITLB) {
                addr = regs->tpc;
        } else {
                /* If we were able to probe the faulting instruction, use it
                 * to compute a precise fault address.  Otherwise use the fault
                 * time provided address which may only have page granularity.
                 */
                if (insn)
                        addr = compute_effective_address(regs, insn, 0);
                else
                        addr = fault_addr;
        }

        if (unlikely(show_unhandled_signals))
                show_signal_msg(regs, sig, code, addr, current);

        force_sig_fault(sig, code, (void __user *) addr, 0);
}

static unsigned int get_fault_insn(struct pt_regs *regs, unsigned int insn)
{
        if (!insn) {
                if (!regs->tpc || (regs->tpc & 0x3))
                        return 0;
                if (regs->tstate & TSTATE_PRIV) {
                        insn = *(unsigned int *) regs->tpc;
                } else {
                        insn = get_user_insn(regs->tpc);
                }
        }
        return insn;
}

static void __kprobes do_kernel_fault(struct pt_regs *regs, int si_code,
                                      int fault_code, unsigned int insn,
                                      unsigned long address)
{
        unsigned char asi = ASI_P;
 
        if ((!insn) && (regs->tstate & TSTATE_PRIV))
                goto cannot_handle;

        /* If user insn could be read (thus insn is zero), that
         * is fine.  We will just gun down the process with a signal
         * in that case.
         */

        if (!(fault_code & (FAULT_CODE_WRITE|FAULT_CODE_ITLB)) &&
            (insn & 0xc0800000) == 0xc0800000) {
                if (insn & 0x2000)
                        asi = (regs->tstate >> 24);
                else
                        asi = (insn >> 5);
                if ((asi & 0xf2) == 0x82) {
                        if (insn & 0x1000000) {
                                handle_ldf_stq(insn, regs);
                        } else {
                                /* This was a non-faulting load. Just clear the
                                 * destination register(s) and continue with the next
                                 * instruction. -jj
                                 */
                                handle_ld_nf(insn, regs);
                        }
                        return;
                }
        }
                
        /* Is this in ex_table? */
        if (regs->tstate & TSTATE_PRIV) {
                const struct exception_table_entry *entry;

                entry = search_exception_tables(regs->tpc);
                if (entry) {
                        regs->tpc = entry->fixup;
                        regs->tnpc = regs->tpc + 4;
                        return;
                }
        } else {
                /* The si_code was set to make clear whether
                 * this was a SEGV_MAPERR or SEGV_ACCERR fault.
                 */
                do_fault_siginfo(si_code, SIGSEGV, regs, address, insn, fault_code);
                return;
        }

cannot_handle:
        unhandled_fault (address, current, regs);
}

static void noinline __kprobes bogus_32bit_fault_tpc(struct pt_regs *regs)
{
        static int times;

        if (times++ < 10)
                printk(KERN_ERR "FAULT[%s:%d]: 32-bit process reports "
                       "64-bit TPC [%lx]\n",
                       current->comm, current->pid,
                       regs->tpc);
        show_regs(regs);
}

asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
{
        enum ctx_state prev_state = exception_enter();
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        unsigned int insn = 0;
        int si_code, fault_code;
        vm_fault_t fault;
        unsigned long address, mm_rss;
        unsigned int flags = FAULT_FLAG_DEFAULT;

        fault_code = get_thread_fault_code();

        if (kprobe_page_fault(regs, 0))
                goto exit_exception;

        si_code = SEGV_MAPERR;
        address = current_thread_info()->fault_address;

        if ((fault_code & FAULT_CODE_ITLB) &&
            (fault_code & FAULT_CODE_DTLB))
                BUG();

        if (test_thread_flag(TIF_32BIT)) {
                if (!(regs->tstate & TSTATE_PRIV)) {
                        if (unlikely((regs->tpc >> 32) != 0)) {
                                bogus_32bit_fault_tpc(regs);
                                goto intr_or_no_mm;
                        }
                }
                if (unlikely((address >> 32) != 0))
                        goto intr_or_no_mm;
        }

        if (regs->tstate & TSTATE_PRIV) {
                unsigned long tpc = regs->tpc;

                /* Sanity check the PC. */
                if ((tpc >= KERNBASE && tpc < (unsigned long) __init_end) ||
                    (tpc >= MODULES_VADDR && tpc < MODULES_END)) {
                        /* Valid, no problems... */
                } else {
                        bad_kernel_pc(regs, address);
                        goto exit_exception;
                }
        } else
                flags |= FAULT_FLAG_USER;

        /*
         * If we're in an interrupt or have no user
         * context, we must not take the fault..
         */
        if (faulthandler_disabled() || !mm)
                goto intr_or_no_mm;

        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);

        if (!mmap_read_trylock(mm)) {
                if ((regs->tstate & TSTATE_PRIV) &&
                    !search_exception_tables(regs->tpc)) {
                        insn = get_fault_insn(regs, insn);
                        goto handle_kernel_fault;
                }

retry:
                mmap_read_lock(mm);
        }

        if (fault_code & FAULT_CODE_BAD_RA)
                goto do_sigbus;

        vma = find_vma(mm, address);
        if (!vma)
                goto bad_area;

        /* Pure DTLB misses do not tell us whether the fault causing
         * load/store/atomic was a write or not, it only says that there
         * was no match.  So in such a case we (carefully) read the
         * instruction to try and figure this out.  It's an optimization
         * so it's ok if we can't do this.
         *
         * Special hack, window spill/fill knows the exact fault type.
         */
        if (((fault_code &
              (FAULT_CODE_DTLB | FAULT_CODE_WRITE | FAULT_CODE_WINFIXUP)) == FAULT_CODE_DTLB) &&
            (vma->vm_flags & VM_WRITE) != 0) {
                insn = get_fault_insn(regs, 0);
                if (!insn)
                        goto continue_fault;
                /* All loads, stores and atomics have bits 30 and 31 both set
                 * in the instruction.  Bit 21 is set in all stores, but we
                 * have to avoid prefetches which also have bit 21 set.
                 */
                if ((insn & 0xc0200000) == 0xc0200000 &&
                    (insn & 0x01780000) != 0x01680000) {
                        /* Don't bother updating thread struct value,
                         * because update_mmu_cache only cares which tlb
                         * the access came from.
                         */
                        fault_code |= FAULT_CODE_WRITE;
                }
        }
continue_fault:

        if (vma->vm_start <= address)
                goto good_area;
        if (!(vma->vm_flags & VM_GROWSDOWN))
                goto bad_area;
        if (!(fault_code & FAULT_CODE_WRITE)) {
                /* Non-faulting loads shouldn't expand stack. */
                insn = get_fault_insn(regs, insn);
                if ((insn & 0xc0800000) == 0xc0800000) {
                        unsigned char asi;

                        if (insn & 0x2000)
                                asi = (regs->tstate >> 24);
                        else
                                asi = (insn >> 5);
                        if ((asi & 0xf2) == 0x82)
                                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:
        si_code = SEGV_ACCERR;

        /* If we took a ITLB miss on a non-executable page, catch
         * that here.
         */
        if ((fault_code & FAULT_CODE_ITLB) && !(vma->vm_flags & VM_EXEC)) {
                WARN(address != regs->tpc,
                     "address (%lx) != regs->tpc (%lx)\n", address, regs->tpc);
                WARN_ON(regs->tstate & TSTATE_PRIV);
                goto bad_area;
        }

        if (fault_code & FAULT_CODE_WRITE) {
                if (!(vma->vm_flags & VM_WRITE))
                        goto bad_area;

                /* Spitfire has an icache which does not snoop
                 * processor stores.  Later processors do...
                 */
                if (tlb_type == spitfire &&
                    (vma->vm_flags & VM_EXEC) != 0 &&
                    vma->vm_file != NULL)
                        set_thread_fault_code(fault_code |
                                              FAULT_CODE_BLKCOMMIT);

                flags |= FAULT_FLAG_WRITE;
        } else {
                /* Allow reads even for write-only mappings */
                if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
                        goto bad_area;
        }

        fault = handle_mm_fault(vma, address, flags);

        if (fault_signal_pending(fault, regs))
                goto exit_exception;

        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 (flags & FAULT_FLAG_ALLOW_RETRY) {
                if (fault & VM_FAULT_MAJOR) {
                        current->maj_flt++;
                        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
                                      1, regs, address);
                } else {
                        current->min_flt++;
                        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
                                      1, regs, address);
                }
                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);

        mm_rss = get_mm_rss(mm);
#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
        mm_rss -= (mm->context.thp_pte_count * (HPAGE_SIZE / PAGE_SIZE));
#endif
        if (unlikely(mm_rss >
                     mm->context.tsb_block[MM_TSB_BASE].tsb_rss_limit))
                tsb_grow(mm, MM_TSB_BASE, mm_rss);
#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
        mm_rss = mm->context.hugetlb_pte_count + mm->context.thp_pte_count;
        mm_rss *= REAL_HPAGE_PER_HPAGE;
        if (unlikely(mm_rss >
                     mm->context.tsb_block[MM_TSB_HUGE].tsb_rss_limit)) {
                if (mm->context.tsb_block[MM_TSB_HUGE].tsb)
                        tsb_grow(mm, MM_TSB_HUGE, mm_rss);
                else
                        hugetlb_setup(regs);

        }
#endif
exit_exception:
        exception_exit(prev_state);
        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:
        insn = get_fault_insn(regs, insn);
        mmap_read_unlock(mm);

handle_kernel_fault:
        do_kernel_fault(regs, si_code, fault_code, insn, address);
        goto exit_exception;

/*
 * 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:
        insn = get_fault_insn(regs, insn);
        mmap_read_unlock(mm);
        if (!(regs->tstate & TSTATE_PRIV)) {
                pagefault_out_of_memory();
                goto exit_exception;
        }
        goto handle_kernel_fault;

intr_or_no_mm:
        insn = get_fault_insn(regs, 0);
        goto handle_kernel_fault;

do_sigbus:
        insn = get_fault_insn(regs, insn);
        mmap_read_unlock(mm);

        /*
         * Send a sigbus, regardless of whether we were in kernel
         * or user mode.
         */
        do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, address, insn, fault_code);

        /* Kernel mode? Handle exceptions or die */
        if (regs->tstate & TSTATE_PRIV)
                goto handle_kernel_fault;
}