// SPDX-License-Identifier: GPL-2.0
#include <linux/compat.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/perf_event.h>
#include <linux/bug.h>
#include <linux/sched/task_stack.h>

#include <asm/perf_regs.h>
#include <asm/ptrace.h>

static u64 perf_ext_regs_value(int idx)
{
        switch (idx) {
        case PERF_REG_ARM64_VG:
                if (WARN_ON_ONCE(!system_supports_sve()))
                        return 0;

                /*
                 * Vector granule is current length in bits of SVE registers
                 * divided by 64.
                 */
                return (task_get_sve_vl(current) * 8) / 64;
        default:
                WARN_ON_ONCE(true);
                return 0;
        }
}

u64 perf_reg_value(struct pt_regs *regs, int idx)
{
        if (WARN_ON_ONCE((u32)idx >= PERF_REG_ARM64_EXTENDED_MAX))
                return 0;

        /*
         * Our handling of compat tasks (PERF_SAMPLE_REGS_ABI_32) is weird, but
         * we're stuck with it for ABI compatibility reasons.
         *
         * For a 32-bit consumer inspecting a 32-bit task, then it will look at
         * the first 16 registers (see arch/arm/include/uapi/asm/perf_regs.h).
         * These correspond directly to a prefix of the registers saved in our
         * 'struct pt_regs', with the exception of the PC, so we copy that down
         * (x15 corresponds to SP_hyp in the architecture).
         *
         * So far, so good.
         *
         * The oddity arises when a 64-bit consumer looks at a 32-bit task and
         * asks for registers beyond PERF_REG_ARM_MAX. In this case, we return
         * SP_usr, LR_usr and PC in the positions where the AArch64 SP, LR and
         * PC registers would normally live. The initial idea was to allow a
         * 64-bit unwinder to unwind a 32-bit task and, although it's not clear
         * how well that works in practice, somebody might be relying on it.
         *
         * At the time we make a sample, we don't know whether the consumer is
         * 32-bit or 64-bit, so we have to cater for both possibilities.
         */
        if (compat_user_mode(regs)) {
                if ((u32)idx == PERF_REG_ARM64_SP)
                        return regs->compat_sp;
                if ((u32)idx == PERF_REG_ARM64_LR)
                        return regs->compat_lr;
                if (idx == 15)
                        return regs->pc;
        }

        if ((u32)idx == PERF_REG_ARM64_SP)
                return regs->sp;

        if ((u32)idx == PERF_REG_ARM64_PC)
                return regs->pc;

        if ((u32)idx >= PERF_REG_ARM64_MAX)
                return perf_ext_regs_value(idx);

        return regs->regs[idx];
}

#define REG_RESERVED (~((1ULL << PERF_REG_ARM64_MAX) - 1))

int perf_reg_validate(u64 mask)
{
        u64 reserved_mask = REG_RESERVED;

        if (system_supports_sve())
                reserved_mask &= ~(1ULL << PERF_REG_ARM64_VG);

        if (!mask || mask & reserved_mask)
                return -EINVAL;

        return 0;
}

u64 perf_reg_abi(struct task_struct *task)
{
        if (is_compat_thread(task_thread_info(task)))
                return PERF_SAMPLE_REGS_ABI_32;
        else
                return PERF_SAMPLE_REGS_ABI_64;
}

void perf_get_regs_user(struct perf_regs *regs_user,
                        struct pt_regs *regs)
{
        regs_user->regs = task_pt_regs(current);
        regs_user->abi = perf_reg_abi(current);
}