// SPDX-License-Identifier: GPL-2.0
#include <linux/err.h>
#include <linux/mm.h>
#include <asm/current.h>
#include <asm/traps.h>
#include <asm/vdso.h>

struct vdso_exception_table_entry {
        int insn, fixup;
};

bool fixup_vdso_exception(struct pt_regs *regs, int trapnr,
                          unsigned long error_code, unsigned long fault_addr)
{
        const struct vdso_image *image = current->mm->context.vdso_image;
        const struct vdso_exception_table_entry *extable;
        unsigned int nr_entries, i;
        unsigned long base;

        /*
         * Do not attempt to fixup #DB or #BP.  It's impossible to identify
         * whether or not a #DB/#BP originated from within an SGX enclave and
         * SGX enclaves are currently the only use case for vDSO fixup.
         */
        if (trapnr == X86_TRAP_DB || trapnr == X86_TRAP_BP)
                return false;

        if (!current->mm->context.vdso)
                return false;

        base =  (unsigned long)current->mm->context.vdso + image->extable_base;
        nr_entries = image->extable_len / (sizeof(*extable));
        extable = image->extable;

        for (i = 0; i < nr_entries; i++) {
                if (regs->ip == base + extable[i].insn) {
                        regs->ip = base + extable[i].fixup;
                        regs->di = trapnr;
                        regs->si = error_code;
                        regs->dx = fault_addr;
                        return true;
                }
        }

        return false;
}