// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Performance counter callchain support - powerpc architecture code
 *
 * Copyright © 2009 Paul Mackerras, IBM Corporation.
 */
#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/sigcontext.h>
#include <asm/ucontext.h>
#include <asm/vdso.h>
#include <asm/pte-walk.h>

#include "callchain.h"

static int read_user_stack_64(const unsigned long __user *ptr, unsigned long *ret)
{
        return __read_user_stack(ptr, ret, sizeof(*ret));
}

/*
 * 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 (current->mm->context.vdso &&
            nip == VDSO64_SYMBOL(current->mm->context.vdso, sigtramp_rt64))
                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;
}

void perf_callchain_user_64(struct perf_callchain_entry_ctx *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_arch_instruction_pointer(regs);
        lr = regs->link;
        sp = regs->gpr[1];

        while (entry->nr < entry->max_stack) {
                fp = (unsigned long __user *) sp;
                if (invalid_user_sp(sp) || 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_context(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;
        }
}