LXR linux/arch/x86/entry/vdso/extable.c

   1// SPDX-License-Identifier: GPL-2.0
   2#include <linux/err.h>
   3#include <linux/mm.h>
   4#include <asm/current.h>
   5#include <asm/traps.h>
   6#include <asm/vdso.h>
   7
   8struct vdso_exception_table_entry {
   9        int insn, fixup;
  10};
  11
  12bool fixup_vdso_exception(struct pt_regs *regs, int trapnr,
  13                          unsigned long error_code, unsigned long fault_addr)
  14{
  15        const struct vdso_image *image = current->mm->context.vdso_image;
  16        const struct vdso_exception_table_entry *extable;
  17        unsigned int nr_entries, i;
  18        unsigned long base;
  19
  20        /*
  21         * Do not attempt to fixup #DB or #BP.  It's impossible to identify
  22         * whether or not a #DB/#BP originated from within an SGX enclave and
  23         * SGX enclaves are currently the only use case for vDSO fixup.
  24         */
  25        if (trapnr == X86_TRAP_DB || trapnr == X86_TRAP_BP)
  26                return false;
  27
  28        if (!current->mm->context.vdso)
  29                return false;
  30
  31        base =  (unsigned long)current->mm->context.vdso + image->extable_base;
  32        nr_entries = image->extable_len / (sizeof(*extable));
  33        extable = image->extable;
  34
  35        for (i = 0; i < nr_entries; i++) {
  36                if (regs->ip == base + extable[i].insn) {
  37                        regs->ip = base + extable[i].fixup;
  38                        regs->di = trapnr;
  39                        regs->si = error_code;
  40                        regs->dx = fault_addr;
  41                        return true;
  42                }
  43        }
  44
  45        return false;
  46}
  47