src/shims/mod.rs

   1 pub mod dlsym;
   2 pub mod env;
   3 pub mod foreign_items;
   4 pub mod intrinsics;
   5 pub mod tls;
   6
   7 use rustc::{mir, ty};
   8
   9 use crate::*;
  10
  11 impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
  12 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
  13     fn find_fn(
  14         &mut self,
  15         instance: ty::Instance<'tcx>,
  16         args: &[OpTy<'tcx, Tag>],
  17         dest: Option<PlaceTy<'tcx, Tag>>,
  18         ret: Option<mir::BasicBlock>,
  19     ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> {
  20         let this = self.eval_context_mut();
  21         trace!(
  22             "eval_fn_call: {:#?}, {:?}",
  23             instance,
  24             dest.map(|place| *place)
  25         );
  26
  27         // First, run the common hooks also supported by CTFE.
  28         if this.hook_fn(instance, args, dest)? {
  29             this.goto_block(ret)?;
  30             return Ok(None);
  31         }
  32         // There are some more lang items we want to hook that CTFE does not hook (yet).
  33         if this.tcx.lang_items().align_offset_fn() == Some(instance.def.def_id()) {
  34             let dest = dest.unwrap();
  35             let n = this
  36                 .align_offset(args[0], args[1])?
  37                 .unwrap_or_else(|| this.truncate(u128::max_value(), dest.layout));
  38             this.write_scalar(Scalar::from_uint(n, dest.layout.size), dest)?;
  39             this.goto_block(ret)?;
  40             return Ok(None);
  41         }
  42
  43         // Try to see if we can do something about foreign items.
  44         if this.tcx.is_foreign_item(instance.def_id()) {
  45             // An external function that we cannot find MIR for, but we can still run enough
  46             // of them to make miri viable.
  47             this.emulate_foreign_item(instance.def_id(), args, dest, ret)?;
  48             // `goto_block` already handled.
  49             return Ok(None);
  50         }
  51
  52         // Otherwise, load the MIR.
  53         Ok(Some(this.load_mir(instance.def, None)?))
  54     }
  55
  56     fn align_offset(
  57         &mut self,
  58         ptr_op: OpTy<'tcx, Tag>,
  59         align_op: OpTy<'tcx, Tag>,
  60     ) -> InterpResult<'tcx, Option<u128>> {
  61         let this = self.eval_context_mut();
  62
  63         let req_align = this.force_bits(
  64             this.read_scalar(align_op)?.not_undef()?,
  65             this.pointer_size(),
  66         )? as usize;
  67
  68         // FIXME: This should actually panic in the interpreted program
  69         if !req_align.is_power_of_two() {
  70             throw_unsup_format!("Required alignment should always be a power of two")
  71         }
  72
  73         let ptr_scalar = this.read_scalar(ptr_op)?.not_undef()?;
  74
  75         if let Ok(ptr) = this.force_ptr(ptr_scalar) {
  76             let cur_align = this.memory().get(ptr.alloc_id)?.align.bytes() as usize;
  77             if cur_align >= req_align {
  78                 // if the allocation alignment is at least the required alignment we use the
  79                 // libcore implementation
  80                 return Ok(Some(
  81                     (this.force_bits(ptr_scalar, this.pointer_size())? as *const i8)
  82                         .align_offset(req_align) as u128,
  83                 ));
  84             }
  85         }
  86         // If the allocation alignment is smaller than then required alignment or the pointer was
  87         // actually an integer, we return `None`
  88         Ok(None)
  89     }
  90 }