Auto merge of #801 - RalfJung:num_cpus, r=RalfJung

support num_cpus crate and test that

Also make some magic numbers into proper global constants.

src/fn_call.rs

@@ -622,11 +622,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let name = this.read_scalar(args[0])?.to_i32()?;
 
                 trace!("sysconf() called with name {}", name);
-                // Cache the sysconf integers via Miri's global cache.
+                // TODO: Cache the sysconf integers via Miri's global cache.
                 let paths = &[
-                    (&["libc", "_SC_PAGESIZE"], Scalar::from_int(4096, dest.layout.size)),
+                    (&["libc", "_SC_PAGESIZE"], Scalar::from_int(PAGE_SIZE, dest.layout.size)),
                     (&["libc", "_SC_GETPW_R_SIZE_MAX"], Scalar::from_int(-1, dest.layout.size)),
-                    (&["libc", "_SC_NPROCESSORS_ONLN"], Scalar::from_int(1, dest.layout.size)),
+                    (&["libc", "_SC_NPROCESSORS_ONLN"], Scalar::from_int(NUM_CPUS, dest.layout.size)),
                 ];
                 let mut result = None;
                 for &(path, path_value) in paths {
@@ -648,6 +648,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 }
             }
 
+            "sched_getaffinity" => {
+                // Return an error; `num_cpus` then falls back to `sysconf`.
+                this.write_scalar(Scalar::from_int(-1, dest.layout.size), dest)?;
+            }
+
             "isatty" => {
                 this.write_null(dest)?;
             }
@@ -722,14 +727,14 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 // Second argument is where we are supposed to write the stack size.
                 let ptr = this.deref_operand(args[1])?;
                 // Just any address.
-                let stack_addr = Scalar::from_int(0x80000, args[1].layout.size);
+                let stack_addr = Scalar::from_uint(STACK_ADDR, args[1].layout.size);
                 this.write_scalar(stack_addr, ptr.into())?;
                 // Return success (`0`).
                 this.write_null(dest)?;
             }
             "pthread_get_stackaddr_np" => {
                 // Just any address.
-                let stack_addr = Scalar::from_int(0x80000, dest.layout.size);
+                let stack_addr = Scalar::from_uint(STACK_ADDR, dest.layout.size);
                 this.write_scalar(stack_addr, dest)?;
             }
 
@@ -838,14 +843,14 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 // Initialize with `0`.
                 this.memory_mut().get_mut(system_info_ptr.alloc_id)?
                     .write_repeat(tcx, system_info_ptr, 0, system_info.layout.size)?;
-                // Set number of processors to `1`.
+                // Set number of processors.
                 let dword_size = Size::from_bytes(4);
                 let offset = 2*dword_size + 3*tcx.pointer_size();
                 this.memory_mut().get_mut(system_info_ptr.alloc_id)?
                     .write_scalar(
                         tcx,
                         system_info_ptr.offset(offset, tcx)?,
-                        Scalar::from_int(1, dword_size).into(),
+                        Scalar::from_int(NUM_CPUS, dword_size).into(),
                         dword_size,
                     )?;
             }

src/intptrcast.rs

@@ -6,8 +6,7 @@ use rustc::mir::interpret::{AllocId, Pointer, InterpResult};
 use rustc_mir::interpret::Memory;
 use rustc_target::abi::Size;
 
-use crate::stacked_borrows::Tag;
-use crate::Evaluator;
+use crate::{Evaluator, Tag, STACK_ADDR};
 
 pub type MemoryExtra = RefCell<GlobalState>;
 
@@ -27,11 +26,10 @@ pub struct GlobalState {
 }
 
 impl Default for GlobalState {
-    // FIXME: Query the page size in the future
     fn default() -> Self {
         GlobalState {
             int_to_ptr_map: Vec::default(),
-            next_base_addr: 2u64.pow(16)
+            next_base_addr: STACK_ADDR,
         }
     }
 }

src/lib.rs

@@ -37,7 +37,10 @@ pub use crate::range_map::RangeMap;
 pub use crate::helpers::{EvalContextExt as HelpersEvalContextExt};
 pub use crate::mono_hash_map::MonoHashMap;
 pub use crate::stacked_borrows::{EvalContextExt as StackedBorEvalContextExt, Tag, Permission, Stack, Stacks, Item};
-pub use crate::machine::{MemoryExtra, AllocExtra, MiriMemoryKind, Evaluator, MiriEvalContext, MiriEvalContextExt};
+pub use crate::machine::{
+    PAGE_SIZE, STACK_ADDR, NUM_CPUS,
+    MemoryExtra, AllocExtra, MiriMemoryKind, Evaluator, MiriEvalContext, MiriEvalContextExt,
+};
 pub use crate::eval::{eval_main, create_ecx, MiriConfig};
 
 /// Insert rustc arguments at the beginning of the argument list that Miri wants to be

src/machine.rs

@@ -13,6 +13,11 @@ use rustc::mir;
 
 use crate::*;
 
+// Some global facts about the emulated machine.
+pub const PAGE_SIZE: u64 = 4*1024; // FIXME: adjust to target architecture
+pub const STACK_ADDR: u64 = 16*PAGE_SIZE; // not really about the "stack", but where we start assigning integer addresses to allocations
+pub const NUM_CPUS: u64 = 1;
+
 /// Extra memory kinds
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub enum MiriMemoryKind {