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
   8 struct vdso_exception_table_entry {
   9         int insn, fixup;
  10 };
  11
  12 bool 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 }