/*
 * Copyright 2010 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/module.h>
#include <linux/pfn.h>
#include <linux/kallsyms.h>
#include <linux/stacktrace.h>
#include <linux/uaccess.h>
#include <linux/mmzone.h>
#include <asm/backtrace.h>
#include <asm/page.h>
#include <asm/tlbflush.h>
#include <asm/ucontext.h>
#include <asm/sigframe.h>
#include <asm/stack.h>
#include <arch/abi.h>
#include <arch/interrupts.h>

#define KBT_ONGOING     0  /* Backtrace still ongoing */
#define KBT_DONE        1  /* Backtrace cleanly completed */
#define KBT_RUNNING     2  /* Can't run backtrace on a running task */
#define KBT_LOOP        3  /* Backtrace entered a loop */

/* Is address on the specified kernel stack? */
static int in_kernel_stack(struct KBacktraceIterator *kbt, unsigned long sp)
{
        ulong kstack_base = (ulong) kbt->task->stack;
        if (kstack_base == 0)  /* corrupt task pointer; just follow stack... */
                return sp >= PAGE_OFFSET && sp < (unsigned long)high_memory;
        return sp >= kstack_base && sp < kstack_base + THREAD_SIZE;
}

/* Is address valid for reading? */
static int valid_address(struct KBacktraceIterator *kbt, unsigned long address)
{
        HV_PTE *l1_pgtable = kbt->pgtable;
        HV_PTE *l2_pgtable;
        unsigned long pfn;
        HV_PTE pte;
        struct page *page;

        if (l1_pgtable == NULL)
                return 0;       /* can't read user space in other tasks */

#ifdef CONFIG_64BIT
        /* Find the real l1_pgtable by looking in the l0_pgtable. */
        pte = l1_pgtable[HV_L0_INDEX(address)];
        if (!hv_pte_get_present(pte))
                return 0;
        pfn = hv_pte_get_pfn(pte);
        if (pte_huge(pte)) {
                if (!pfn_valid(pfn)) {
                        pr_err("L0 huge page has bad pfn %#lx\n", pfn);
                        return 0;
                }
                return hv_pte_get_present(pte) && hv_pte_get_readable(pte);
        }
        page = pfn_to_page(pfn);
        BUG_ON(PageHighMem(page));  /* No HIGHMEM on 64-bit. */
        l1_pgtable = (HV_PTE *)pfn_to_kaddr(pfn);
#endif
        pte = l1_pgtable[HV_L1_INDEX(address)];
        if (!hv_pte_get_present(pte))
                return 0;
        pfn = hv_pte_get_pfn(pte);
        if (pte_huge(pte)) {
                if (!pfn_valid(pfn)) {
                        pr_err("huge page has bad pfn %#lx\n", pfn);
                        return 0;
                }
                return hv_pte_get_present(pte) && hv_pte_get_readable(pte);
        }

        page = pfn_to_page(pfn);
        if (PageHighMem(page)) {
                pr_err("L2 page table not in LOWMEM (%#llx)\n",
                       HV_PFN_TO_CPA(pfn));
                return 0;
        }
        l2_pgtable = (HV_PTE *)pfn_to_kaddr(pfn);
        pte = l2_pgtable[HV_L2_INDEX(address)];
        return hv_pte_get_present(pte) && hv_pte_get_readable(pte);
}

/* Callback for backtracer; basically a glorified memcpy */
static bool read_memory_func(void *result, unsigned long address,
                             unsigned int size, void *vkbt)
{
        int retval;
        struct KBacktraceIterator *kbt = (struct KBacktraceIterator *)vkbt;
        if (__kernel_text_address(address)) {
                /* OK to read kernel code. */
        } else if (address >= PAGE_OFFSET) {
                /* We only tolerate kernel-space reads of this task's stack */
                if (!in_kernel_stack(kbt, address))
                        return 0;
        } else if (!valid_address(kbt, address)) {
                return 0;       /* invalid user-space address */
        }
        pagefault_disable();
        retval = __copy_from_user_inatomic(result,
                                           (void __user __force *)address,
                                           size);
        pagefault_enable();
        return (retval == 0);
}

/* Return a pt_regs pointer for a valid fault handler frame */
static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
{
        const char *fault = NULL;  /* happy compiler */
        char fault_buf[64];
        unsigned long sp = kbt->it.sp;
        struct pt_regs *p;

        if (!in_kernel_stack(kbt, sp))
                return NULL;
        if (!in_kernel_stack(kbt, sp + C_ABI_SAVE_AREA_SIZE + PTREGS_SIZE-1))
                return NULL;
        p = (struct pt_regs *)(sp + C_ABI_SAVE_AREA_SIZE);
        if (p->faultnum == INT_SWINT_1 || p->faultnum == INT_SWINT_1_SIGRETURN)
                fault = "syscall";
        else {
                if (kbt->verbose) {     /* else we aren't going to use it */
                        snprintf(fault_buf, sizeof(fault_buf),
                                 "interrupt %ld", p->faultnum);
                        fault = fault_buf;
                }
        }
        if (EX1_PL(p->ex1) == KERNEL_PL &&
            __kernel_text_address(p->pc) &&
            in_kernel_stack(kbt, p->sp) &&
            p->sp >= sp) {
                if (kbt->verbose)
                        pr_err("  <%s while in kernel mode>\n", fault);
        } else if (EX1_PL(p->ex1) == USER_PL &&
            p->pc < PAGE_OFFSET &&
            p->sp < PAGE_OFFSET) {
                if (kbt->verbose)
                        pr_err("  <%s while in user mode>\n", fault);
        } else if (kbt->verbose) {
                pr_err("  (odd fault: pc %#lx, sp %#lx, ex1 %#lx?)\n",
                       p->pc, p->sp, p->ex1);
                p = NULL;
        }
        if (!kbt->profile || (INT_MASK(p->faultnum) & QUEUED_INTERRUPTS) == 0)
                return p;
        return NULL;
}

/* Is the pc pointing to a sigreturn trampoline? */
static int is_sigreturn(unsigned long pc)
{
        return (pc == VDSO_BASE);
}

/* Return a pt_regs pointer for a valid signal handler frame */
static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt)
{
        BacktraceIterator *b = &kbt->it;

        if (b->pc == VDSO_BASE) {
                struct rt_sigframe *frame;
                unsigned long sigframe_top =
                        b->sp + sizeof(struct rt_sigframe) - 1;
                if (!valid_address(kbt, b->sp) ||
                    !valid_address(kbt, sigframe_top)) {
                        if (kbt->verbose)
                                pr_err("  (odd signal: sp %#lx?)\n",
                                       (unsigned long)(b->sp));
                        return NULL;
                }
                frame = (struct rt_sigframe *)b->sp;
                if (kbt->verbose) {
                        pr_err("  <received signal %d>\n",
                               frame->info.si_signo);
                }
                return (struct pt_regs *)&frame->uc.uc_mcontext;
        }
        return NULL;
}

static int KBacktraceIterator_is_sigreturn(struct KBacktraceIterator *kbt)
{
        return is_sigreturn(kbt->it.pc);
}

static int KBacktraceIterator_restart(struct KBacktraceIterator *kbt)
{
        struct pt_regs *p;

        p = valid_fault_handler(kbt);
        if (p == NULL)
                p = valid_sigframe(kbt);
        if (p == NULL)
                return 0;
        backtrace_init(&kbt->it, read_memory_func, kbt,
                       p->pc, p->lr, p->sp, p->regs[52]);
        kbt->new_context = 1;
        return 1;
}

/* Find a frame that isn't a sigreturn, if there is one. */
static int KBacktraceIterator_next_item_inclusive(
        struct KBacktraceIterator *kbt)
{
        for (;;) {
                do {
                        if (!KBacktraceIterator_is_sigreturn(kbt))
                                return KBT_ONGOING;
                } while (backtrace_next(&kbt->it));

                if (!KBacktraceIterator_restart(kbt))
                        return KBT_DONE;
        }
}

/*
 * If the current sp is on a page different than what we recorded
 * as the top-of-kernel-stack last time we context switched, we have
 * probably blown the stack, and nothing is going to work out well.
 * If we can at least get out a warning, that may help the debug,
 * though we probably won't be able to backtrace into the code that
 * actually did the recursive damage.
 */
static void validate_stack(struct pt_regs *regs)
{
        int cpu = smp_processor_id();
        unsigned long ksp0 = get_current_ksp0();
        unsigned long ksp0_base = ksp0 - THREAD_SIZE;
        unsigned long sp = stack_pointer;

        if (EX1_PL(regs->ex1) == KERNEL_PL && regs->sp >= ksp0) {
                pr_err("WARNING: cpu %d: kernel stack page %#lx underrun!\n"
                       "  sp %#lx (%#lx in caller), caller pc %#lx, lr %#lx\n",
                       cpu, ksp0_base, sp, regs->sp, regs->pc, regs->lr);
        }

        else if (sp < ksp0_base + sizeof(struct thread_info)) {
                pr_err("WARNING: cpu %d: kernel stack page %#lx overrun!\n"
                       "  sp %#lx (%#lx in caller), caller pc %#lx, lr %#lx\n",
                       cpu, ksp0_base, sp, regs->sp, regs->pc, regs->lr);
        }
}

void KBacktraceIterator_init(struct KBacktraceIterator *kbt,
                             struct task_struct *t, struct pt_regs *regs)
{
        unsigned long pc, lr, sp, r52;
        int is_current;

        /*
         * Set up callback information.  We grab the kernel stack base
         * so we will allow reads of that address range, and if we're
         * asking about the current process we grab the page table
         * so we can check user accesses before trying to read them.
         * We flush the TLB to avoid any weird skew issues.
         */
        is_current = (t == NULL);
        kbt->is_current = is_current;
        if (is_current)
                t = validate_current();
        kbt->task = t;
        kbt->pgtable = NULL;
        kbt->verbose = 0;   /* override in caller if desired */
        kbt->profile = 0;   /* override in caller if desired */
        kbt->end = KBT_ONGOING;
        kbt->new_context = 0;
        if (is_current) {
                HV_PhysAddr pgdir_pa = hv_inquire_context().page_table;
                if (pgdir_pa == (unsigned long)swapper_pg_dir - PAGE_OFFSET) {
                        /*
                         * Not just an optimization: this also allows
                         * this to work at all before va/pa mappings
                         * are set up.
                         */
                        kbt->pgtable = swapper_pg_dir;
                } else {
                        struct page *page = pfn_to_page(PFN_DOWN(pgdir_pa));
                        if (!PageHighMem(page))
                                kbt->pgtable = __va(pgdir_pa);
                        else
                                pr_err("page table not in LOWMEM"
                                       " (%#llx)\n", pgdir_pa);
                }
                local_flush_tlb_all();
                validate_stack(regs);
        }

        if (regs == NULL) {
                if (is_current || t->state == TASK_RUNNING) {
                        /* Can't do this; we need registers */
                        kbt->end = KBT_RUNNING;
                        return;
                }
                pc = get_switch_to_pc();
                lr = t->thread.pc;
                sp = t->thread.ksp;
                r52 = 0;
        } else {
                pc = regs->pc;
                lr = regs->lr;
                sp = regs->sp;
                r52 = regs->regs[52];
        }

        backtrace_init(&kbt->it, read_memory_func, kbt, pc, lr, sp, r52);
        kbt->end = KBacktraceIterator_next_item_inclusive(kbt);
}
EXPORT_SYMBOL(KBacktraceIterator_init);

int KBacktraceIterator_end(struct KBacktraceIterator *kbt)
{
        return kbt->end != KBT_ONGOING;
}
EXPORT_SYMBOL(KBacktraceIterator_end);

void KBacktraceIterator_next(struct KBacktraceIterator *kbt)
{
        unsigned long old_pc = kbt->it.pc, old_sp = kbt->it.sp;
        kbt->new_context = 0;
        if (!backtrace_next(&kbt->it) && !KBacktraceIterator_restart(kbt)) {
                kbt->end = KBT_DONE;
                return;
        }
        kbt->end = KBacktraceIterator_next_item_inclusive(kbt);
        if (old_pc == kbt->it.pc && old_sp == kbt->it.sp) {
                /* Trapped in a loop; give up. */
                kbt->end = KBT_LOOP;
        }
}
EXPORT_SYMBOL(KBacktraceIterator_next);

/*
 * This method wraps the backtracer's more generic support.
 * It is only invoked from the architecture-specific code; show_stack()
 * and dump_stack() (in entry.S) are architecture-independent entry points.
 */
void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
{
        int i;

        if (headers) {
                /*
                 * Add a blank line since if we are called from panic(),
                 * then bust_spinlocks() spit out a space in front of us
                 * and it will mess up our KERN_ERR.
                 */
                pr_err("\n");
                pr_err("Starting stack dump of tid %d, pid %d (%s)"
                       " on cpu %d at cycle %lld\n",
                       kbt->task->pid, kbt->task->tgid, kbt->task->comm,
                       smp_processor_id(), get_cycles());
        }
        kbt->verbose = 1;
        i = 0;
        for (; !KBacktraceIterator_end(kbt); KBacktraceIterator_next(kbt)) {
                char *modname;
                const char *name;
                unsigned long address = kbt->it.pc;
                unsigned long offset, size;
                char namebuf[KSYM_NAME_LEN+100];

                if (address >= PAGE_OFFSET)
                        name = kallsyms_lookup(address, &size, &offset,
                                               &modname, namebuf);
                else
                        name = NULL;

                if (!name)
                        namebuf[0] = '\0';
                else {
                        size_t namelen = strlen(namebuf);
                        size_t remaining = (sizeof(namebuf) - 1) - namelen;
                        char *p = namebuf + namelen;
                        int rc = snprintf(p, remaining, "+%#lx/%#lx ",
                                          offset, size);
                        if (modname && rc < remaining)
                                snprintf(p + rc, remaining - rc,
                                         "[%s] ", modname);
                        namebuf[sizeof(namebuf)-1] = '\0';
                }

                pr_err("  frame %d: 0x%lx %s(sp 0x%lx)\n",
                       i++, address, namebuf, (unsigned long)(kbt->it.sp));

                if (i >= 100) {
                        pr_err("Stack dump truncated"
                               " (%d frames)\n", i);
                        break;
                }
        }
        if (kbt->end == KBT_LOOP)
                pr_err("Stack dump stopped; next frame identical to this one\n");
        if (headers)
                pr_err("Stack dump complete\n");
}
EXPORT_SYMBOL(tile_show_stack);


/* This is called from show_regs() and _dump_stack() */
void dump_stack_regs(struct pt_regs *regs)
{
        struct KBacktraceIterator kbt;
        KBacktraceIterator_init(&kbt, NULL, regs);
        tile_show_stack(&kbt, 1);
}
EXPORT_SYMBOL(dump_stack_regs);

static struct pt_regs *regs_to_pt_regs(struct pt_regs *regs,
                                       ulong pc, ulong lr, ulong sp, ulong r52)
{
        memset(regs, 0, sizeof(struct pt_regs));
        regs->pc = pc;
        regs->lr = lr;
        regs->sp = sp;
        regs->regs[52] = r52;
        return regs;
}

/* This is called from dump_stack() and just converts to pt_regs */
void _dump_stack(int dummy, ulong pc, ulong lr, ulong sp, ulong r52)
{
        struct pt_regs regs;
        dump_stack_regs(regs_to_pt_regs(&regs, pc, lr, sp, r52));
}

/* This is called from KBacktraceIterator_init_current() */
void _KBacktraceIterator_init_current(struct KBacktraceIterator *kbt, ulong pc,
                                      ulong lr, ulong sp, ulong r52)
{
        struct pt_regs regs;
        KBacktraceIterator_init(kbt, NULL,
                                regs_to_pt_regs(&regs, pc, lr, sp, r52));
}

/* This is called only from kernel/sched.c, with esp == NULL */
void show_stack(struct task_struct *task, unsigned long *esp)
{
        struct KBacktraceIterator kbt;
        if (task == NULL || task == current)
                KBacktraceIterator_init_current(&kbt);
        else
                KBacktraceIterator_init(&kbt, task, NULL);
        tile_show_stack(&kbt, 0);
}

#ifdef CONFIG_STACKTRACE

/* Support generic Linux stack API too */

void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
{
        struct KBacktraceIterator kbt;
        int skip = trace->skip;
        int i = 0;

        if (task == NULL || task == current)
                KBacktraceIterator_init_current(&kbt);
        else
                KBacktraceIterator_init(&kbt, task, NULL);
        for (; !KBacktraceIterator_end(&kbt); KBacktraceIterator_next(&kbt)) {
                if (skip) {
                        --skip;
                        continue;
                }
                if (i >= trace->max_entries || kbt.it.pc < PAGE_OFFSET)
                        break;
                trace->entries[i++] = kbt.it.pc;
        }
        trace->nr_entries = i;
}
EXPORT_SYMBOL(save_stack_trace_tsk);

void save_stack_trace(struct stack_trace *trace)
{
        save_stack_trace_tsk(NULL, trace);
}

#endif

/* In entry.S */
EXPORT_SYMBOL(KBacktraceIterator_init_current);