/*
 * Performance counter callchain support - powerpc architecture code
 *
 * Copyright © 2009 Paul Mackerras, IBM Corporation.
 *
 * 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; either version
 * 2 of the License, or (at your option) any later version.
 */
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/perf_event.h>
#include <linux/percpu.h>
#include <linux/uaccess.h>
#include <linux/mm.h>
#include <asm/ptrace.h>
#include <asm/pgtable.h>
#include <asm/sigcontext.h>
#include <asm/ucontext.h>
#include <asm/vdso.h>
#ifdef CONFIG_PPC64
#include "../kernel/ppc32.h"
#endif


/*
 * Is sp valid as the address of the next kernel stack frame after prev_sp?
 * The next frame may be in a different stack area but should not go
 * back down in the same stack area.
 */
static int valid_next_sp(unsigned long sp, unsigned long prev_sp)
{
        if (sp & 0xf)
                return 0;               /* must be 16-byte aligned */
        if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
                return 0;
        if (sp >= prev_sp + STACK_FRAME_MIN_SIZE)
                return 1;
        /*
         * sp could decrease when we jump off an interrupt stack
         * back to the regular process stack.
         */
        if ((sp & ~(THREAD_SIZE - 1)) != (prev_sp & ~(THREAD_SIZE - 1)))
                return 1;
        return 0;
}

void
perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
{
        unsigned long sp, next_sp;
        unsigned long next_ip;
        unsigned long lr;
        long level = 0;
        unsigned long *fp;

        lr = regs->link;
        sp = regs->gpr[1];
        perf_callchain_store(entry, perf_instruction_pointer(regs));

        if (!validate_sp(sp, current, STACK_FRAME_OVERHEAD))
                return;

        for (;;) {
                fp = (unsigned long *) sp;
                next_sp = fp[0];

                if (next_sp == sp + STACK_INT_FRAME_SIZE &&
                    fp[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
                        /*
                         * This looks like an interrupt frame for an
                         * interrupt that occurred in the kernel
                         */
                        regs = (struct pt_regs *)(sp + STACK_FRAME_OVERHEAD);
                        next_ip = regs->nip;
                        lr = regs->link;
                        level = 0;
                        perf_callchain_store(entry, PERF_CONTEXT_KERNEL);

                } else {
                        if (level == 0)
                                next_ip = lr;
                        else
                                next_ip = fp[STACK_FRAME_LR_SAVE];

                        /*
                         * We can't tell which of the first two addresses
                         * we get are valid, but we can filter out the
                         * obviously bogus ones here.  We replace them
                         * with 0 rather than removing them entirely so
                         * that userspace can tell which is which.
                         */
                        if ((level == 1 && next_ip == lr) ||
                            (level <= 1 && !kernel_text_address(next_ip)))
                                next_ip = 0;

                        ++level;
                }

                perf_callchain_store(entry, next_ip);
                if (!valid_next_sp(next_sp, sp))
                        return;
                sp = next_sp;
        }
}

#ifdef CONFIG_PPC64
/*
 * On 64-bit we don't want to invoke hash_page on user addresses from
 * interrupt context, so if the access faults, we read the page tables
 * to find which page (if any) is mapped and access it directly.
 */
static int read_user_stack_slow(void __user *ptr, void *buf, int nb)
{
        int ret = -EFAULT;
        pgd_t *pgdir;
        pte_t *ptep, pte;
        unsigned shift;
        unsigned long addr = (unsigned long) ptr;
        unsigned long offset;
        unsigned long pfn, flags;
        void *kaddr;

        pgdir = current->mm->pgd;
        if (!pgdir)
                return -EFAULT;

        local_irq_save(flags);
        ptep = find_linux_pte_or_hugepte(pgdir, addr, &shift);
        if (!ptep)
                goto err_out;
        if (!shift)
                shift = PAGE_SHIFT;

        /* align address to page boundary */
        offset = addr & ((1UL << shift) - 1);

        pte = READ_ONCE(*ptep);
        if (!pte_present(pte) || !(pte_val(pte) & _PAGE_USER))
                goto err_out;
        pfn = pte_pfn(pte);
        if (!page_is_ram(pfn))
                goto err_out;

        /* no highmem to worry about here */
        kaddr = pfn_to_kaddr(pfn);
        memcpy(buf, kaddr + offset, nb);
        ret = 0;
err_out:
        local_irq_restore(flags);
        return ret;
}

static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
{
        if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned long) ||
            ((unsigned long)ptr & 7))
                return -EFAULT;

        pagefault_disable();
        if (!__get_user_inatomic(*ret, ptr)) {
                pagefault_enable();
                return 0;
        }
        pagefault_enable();

        return read_user_stack_slow(ptr, ret, 8);
}

static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
{
        if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
            ((unsigned long)ptr & 3))
                return -EFAULT;

        pagefault_disable();
        if (!__get_user_inatomic(*ret, ptr)) {
                pagefault_enable();
                return 0;
        }
        pagefault_enable();

        return read_user_stack_slow(ptr, ret, 4);
}

static inline int valid_user_sp(unsigned long sp, int is_64)
{
        if (!sp || (sp & 7) || sp > (is_64 ? TASK_SIZE : 0x100000000UL) - 32)
                return 0;
        return 1;
}

/*
 * 64-bit user processes use the same stack frame for RT and non-RT signals.
 */
struct signal_frame_64 {
        char            dummy[__SIGNAL_FRAMESIZE];
        struct ucontext uc;
        unsigned long   unused[2];
        unsigned int    tramp[6];
        struct siginfo  *pinfo;
        void            *puc;
        struct siginfo  info;
        char            abigap[288];
};

static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
{
        if (nip == fp + offsetof(struct signal_frame_64, tramp))
                return 1;
        if (vdso64_rt_sigtramp && current->mm->context.vdso_base &&
            nip == current->mm->context.vdso_base + vdso64_rt_sigtramp)
                return 1;
        return 0;
}

/*
 * Do some sanity checking on the signal frame pointed to by sp.
 * We check the pinfo and puc pointers in the frame.
 */
static int sane_signal_64_frame(unsigned long sp)
{
        struct signal_frame_64 __user *sf;
        unsigned long pinfo, puc;

        sf = (struct signal_frame_64 __user *) sp;
        if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
            read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
                return 0;
        return pinfo == (unsigned long) &sf->info &&
                puc == (unsigned long) &sf->uc;
}

static void perf_callchain_user_64(struct perf_callchain_entry *entry,
                                   struct pt_regs *regs)
{
        unsigned long sp, next_sp;
        unsigned long next_ip;
        unsigned long lr;
        long level = 0;
        struct signal_frame_64 __user *sigframe;
        unsigned long __user *fp, *uregs;

        next_ip = perf_instruction_pointer(regs);
        lr = regs->link;
        sp = regs->gpr[1];
        perf_callchain_store(entry, next_ip);

        while (entry->nr < PERF_MAX_STACK_DEPTH) {
                fp = (unsigned long __user *) sp;
                if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
                        return;
                if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
                        return;

                /*
                 * Note: the next_sp - sp >= signal frame size check
                 * is true when next_sp < sp, which can happen when
                 * transitioning from an alternate signal stack to the
                 * normal stack.
                 */
                if (next_sp - sp >= sizeof(struct signal_frame_64) &&
                    (is_sigreturn_64_address(next_ip, sp) ||
                     (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
                    sane_signal_64_frame(sp)) {
                        /*
                         * This looks like an signal frame
                         */
                        sigframe = (struct signal_frame_64 __user *) sp;
                        uregs = sigframe->uc.uc_mcontext.gp_regs;
                        if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
                            read_user_stack_64(&uregs[PT_LNK], &lr) ||
                            read_user_stack_64(&uregs[PT_R1], &sp))
                                return;
                        level = 0;
                        perf_callchain_store(entry, PERF_CONTEXT_USER);
                        perf_callchain_store(entry, next_ip);
                        continue;
                }

                if (level == 0)
                        next_ip = lr;
                perf_callchain_store(entry, next_ip);
                ++level;
                sp = next_sp;
        }
}

static inline int current_is_64bit(void)
{
        /*
         * We can't use test_thread_flag() here because we may be on an
         * interrupt stack, and the thread flags don't get copied over
         * from the thread_info on the main stack to the interrupt stack.
         */
        return !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
}

#else  /* CONFIG_PPC64 */
/*
 * On 32-bit we just access the address and let hash_page create a
 * HPTE if necessary, so there is no need to fall back to reading
 * the page tables.  Since this is called at interrupt level,
 * do_page_fault() won't treat a DSI as a page fault.
 */
static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
{
        int rc;

        if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
            ((unsigned long)ptr & 3))
                return -EFAULT;

        pagefault_disable();
        rc = __get_user_inatomic(*ret, ptr);
        pagefault_enable();

        return rc;
}

static inline void perf_callchain_user_64(struct perf_callchain_entry *entry,
                                          struct pt_regs *regs)
{
}

static inline int current_is_64bit(void)
{
        return 0;
}

static inline int valid_user_sp(unsigned long sp, int is_64)
{
        if (!sp || (sp & 7) || sp > TASK_SIZE - 32)
                return 0;
        return 1;
}

#define __SIGNAL_FRAMESIZE32    __SIGNAL_FRAMESIZE
#define sigcontext32            sigcontext
#define mcontext32              mcontext
#define ucontext32              ucontext
#define compat_siginfo_t        struct siginfo

#endif /* CONFIG_PPC64 */

/*
 * Layout for non-RT signal frames
 */
struct signal_frame_32 {
        char                    dummy[__SIGNAL_FRAMESIZE32];
        struct sigcontext32     sctx;
        struct mcontext32       mctx;
        int                     abigap[56];
};

/*
 * Layout for RT signal frames
 */
struct rt_signal_frame_32 {
        char                    dummy[__SIGNAL_FRAMESIZE32 + 16];
        compat_siginfo_t        info;
        struct ucontext32       uc;
        int                     abigap[56];
};

static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
{
        if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))
                return 1;
        if (vdso32_sigtramp && current->mm->context.vdso_base &&
            nip == current->mm->context.vdso_base + vdso32_sigtramp)
                return 1;
        return 0;
}

static int is_rt_sigreturn_32_address(unsigned int nip, unsigned int fp)
{
        if (nip == fp + offsetof(struct rt_signal_frame_32,
                                 uc.uc_mcontext.mc_pad))
                return 1;
        if (vdso32_rt_sigtramp && current->mm->context.vdso_base &&
            nip == current->mm->context.vdso_base + vdso32_rt_sigtramp)
                return 1;
        return 0;
}

static int sane_signal_32_frame(unsigned int sp)
{
        struct signal_frame_32 __user *sf;
        unsigned int regs;

        sf = (struct signal_frame_32 __user *) (unsigned long) sp;
        if (read_user_stack_32((unsigned int __user *) &sf->sctx.regs, &regs))
                return 0;
        return regs == (unsigned long) &sf->mctx;
}

static int sane_rt_signal_32_frame(unsigned int sp)
{
        struct rt_signal_frame_32 __user *sf;
        unsigned int regs;

        sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
        if (read_user_stack_32((unsigned int __user *) &sf->uc.uc_regs, &regs))
                return 0;
        return regs == (unsigned long) &sf->uc.uc_mcontext;
}

static unsigned int __user *signal_frame_32_regs(unsigned int sp,
                                unsigned int next_sp, unsigned int next_ip)
{
        struct mcontext32 __user *mctx = NULL;
        struct signal_frame_32 __user *sf;
        struct rt_signal_frame_32 __user *rt_sf;

        /*
         * Note: the next_sp - sp >= signal frame size check
         * is true when next_sp < sp, for example, when
         * transitioning from an alternate signal stack to the
         * normal stack.
         */
        if (next_sp - sp >= sizeof(struct signal_frame_32) &&
            is_sigreturn_32_address(next_ip, sp) &&
            sane_signal_32_frame(sp)) {
                sf = (struct signal_frame_32 __user *) (unsigned long) sp;
                mctx = &sf->mctx;
        }

        if (!mctx && next_sp - sp >= sizeof(struct rt_signal_frame_32) &&
            is_rt_sigreturn_32_address(next_ip, sp) &&
            sane_rt_signal_32_frame(sp)) {
                rt_sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
                mctx = &rt_sf->uc.uc_mcontext;
        }

        if (!mctx)
                return NULL;
        return mctx->mc_gregs;
}

static void perf_callchain_user_32(struct perf_callchain_entry *entry,
                                   struct pt_regs *regs)
{
        unsigned int sp, next_sp;
        unsigned int next_ip;
        unsigned int lr;
        long level = 0;
        unsigned int __user *fp, *uregs;

        next_ip = perf_instruction_pointer(regs);
        lr = regs->link;
        sp = regs->gpr[1];
        perf_callchain_store(entry, next_ip);

        while (entry->nr < PERF_MAX_STACK_DEPTH) {
                fp = (unsigned int __user *) (unsigned long) sp;
                if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
                        return;
                if (level > 0 && read_user_stack_32(&fp[1], &next_ip))
                        return;

                uregs = signal_frame_32_regs(sp, next_sp, next_ip);
                if (!uregs && level <= 1)
                        uregs = signal_frame_32_regs(sp, next_sp, lr);
                if (uregs) {
                        /*
                         * This looks like an signal frame, so restart
                         * the stack trace with the values in it.
                         */
                        if (read_user_stack_32(&uregs[PT_NIP], &next_ip) ||
                            read_user_stack_32(&uregs[PT_LNK], &lr) ||
                            read_user_stack_32(&uregs[PT_R1], &sp))
                                return;
                        level = 0;
                        perf_callchain_store(entry, PERF_CONTEXT_USER);
                        perf_callchain_store(entry, next_ip);
                        continue;
                }

                if (level == 0)
                        next_ip = lr;
                perf_callchain_store(entry, next_ip);
                ++level;
                sp = next_sp;
        }
}

void
perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
{
        if (current_is_64bit())
                perf_callchain_user_64(entry, regs);
        else
                perf_callchain_user_32(entry, regs);
}