separate windows heap functions from C heap shims

Author: RalfJung

src/tools/miri/src/lib.rs

@@ -12,6 +12,7 @@
 #![feature(let_chains)]
 #![feature(lint_reasons)]
 #![feature(trait_upcasting)]
+#![feature(strict_overflow_ops)]
 // Configure clippy and other lints
 #![allow(
     clippy::collapsible_else_if,

src/tools/miri/src/shims/alloc.rs

@@ -19,8 +19,8 @@ pub(super) fn check_alloc_request<'tcx>(size: u64, align: u64) -> InterpResult<'
 
 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriInterpCx<'mir, 'tcx> {}
 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
-    /// Returns the minimum alignment for the target architecture for allocations of the given size.
-    fn min_align(&self, size: u64, kind: MiriMemoryKind) -> Align {
+    /// Returns the alignment that `malloc` would guarantee for requests of the given size.
+    fn malloc_align(&self, size: u64) -> Align {
         let this = self.eval_context_ref();
         // The C standard says: "The pointer returned if the allocation succeeds is suitably aligned
         // so that it may be assigned to a pointer to any type of object with a fundamental
@@ -43,9 +43,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         // - https://github.com/jemalloc/jemalloc/issues/1533
         // - https://github.com/llvm/llvm-project/issues/53540
         // - https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2293.htm
-        // However, Windows `HeapAlloc` always aligns, even small allocations, so it gets different treatment here.
-        // Source: <https://learn.microsoft.com/en-us/windows/win32/api/heapapi/nf-heapapi-heapalloc>
-        if kind == MiriMemoryKind::WinHeap || size >= max_fundamental_align {
+        if size >= max_fundamental_align {
             return Align::from_bytes(max_fundamental_align).unwrap();
         }
         // C doesn't have zero-sized types, so presumably nothing is guaranteed here.
@@ -98,11 +96,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         &mut self,
         size: u64,
         zero_init: bool,
-        kind: MiriMemoryKind,
     ) -> InterpResult<'tcx, Pointer<Option<Provenance>>> {
         let this = self.eval_context_mut();
-        let align = this.min_align(size, kind);
-        let ptr = this.allocate_ptr(Size::from_bytes(size), align, kind.into())?;
+        let align = this.malloc_align(size);
+        let ptr = this.allocate_ptr(Size::from_bytes(size), align, MiriMemoryKind::C.into())?;
         if zero_init {
             // We just allocated this, the access is definitely in-bounds and fits into our address space.
             this.write_bytes_ptr(
@@ -114,14 +111,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         Ok(ptr.into())
     }
 
-    fn free(
-        &mut self,
-        ptr: Pointer<Option<Provenance>>,
-        kind: MiriMemoryKind,
-    ) -> InterpResult<'tcx> {
+    fn free(&mut self, ptr: Pointer<Option<Provenance>>) -> InterpResult<'tcx> {
         let this = self.eval_context_mut();
         if !this.ptr_is_null(ptr)? {
-            this.deallocate_ptr(ptr, None, kind.into())?;
+            this.deallocate_ptr(ptr, None, MiriMemoryKind::C.into())?;
         }
         Ok(())
     }
@@ -130,13 +123,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         &mut self,
         old_ptr: Pointer<Option<Provenance>>,
         new_size: u64,
-        kind: MiriMemoryKind,
     ) -> InterpResult<'tcx, Pointer<Option<Provenance>>> {
         let this = self.eval_context_mut();
-        let new_align = this.min_align(new_size, kind);
+        let new_align = this.malloc_align(new_size);
         if this.ptr_is_null(old_ptr)? {
             // Here we must behave like `malloc`.
-            self.malloc(new_size, /*zero_init*/ false, kind)
+            self.malloc(new_size, /*zero_init*/ false)
         } else {
             if new_size == 0 {
                 // C, in their infinite wisdom, made this UB.
@@ -148,7 +140,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                     None,
                     Size::from_bytes(new_size),
                     new_align,
-                    kind.into(),
+                    MiriMemoryKind::C.into(),
                 )?;
                 Ok(new_ptr.into())
             }

src/tools/miri/src/shims/foreign_items.rs

@@ -421,7 +421,7 @@ trait EvalContextExtPriv<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
             "malloc" => {
                 let [size] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let size = this.read_target_usize(size)?;
-                let res = this.malloc(size, /*zero_init:*/ false, MiriMemoryKind::C)?;
+                let res = this.malloc(size, /*zero_init:*/ false)?;
                 this.write_pointer(res, dest)?;
             }
             "calloc" => {
@@ -432,20 +432,20 @@ trait EvalContextExtPriv<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                 let size = items
                     .checked_mul(len)
                     .ok_or_else(|| err_ub_format!("overflow during calloc size computation"))?;
-                let res = this.malloc(size, /*zero_init:*/ true, MiriMemoryKind::C)?;
+                let res = this.malloc(size, /*zero_init:*/ true)?;
                 this.write_pointer(res, dest)?;
             }
             "free" => {
                 let [ptr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let ptr = this.read_pointer(ptr)?;
-                this.free(ptr, MiriMemoryKind::C)?;
+                this.free(ptr)?;
             }
             "realloc" => {
                 let [old_ptr, new_size] =
                     this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let old_ptr = this.read_pointer(old_ptr)?;
                 let new_size = this.read_target_usize(new_size)?;
-                let res = this.realloc(old_ptr, new_size, MiriMemoryKind::C)?;
+                let res = this.realloc(old_ptr, new_size)?;
                 this.write_pointer(res, dest)?;
             }
 

src/tools/miri/src/shims/unix/foreign_items.rs

@@ -310,7 +310,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                         this.write_null(dest)?;
                     }
                     Some(len) => {
-                        let res = this.realloc(ptr, len, MiriMemoryKind::C)?;
+                        let res = this.realloc(ptr, len)?;
                         this.write_pointer(res, dest)?;
                     }
                 }

src/tools/miri/src/shims/windows/foreign_items.rs

@@ -5,10 +5,9 @@ use std::path::{self, Path, PathBuf};
 use std::str;
 
 use rustc_span::Symbol;
-use rustc_target::abi::Size;
+use rustc_target::abi::{Align, Size};
 use rustc_target::spec::abi::Abi;
 
-use crate::shims::alloc::EvalContextExt as _;
 use crate::shims::os_str::bytes_to_os_str;
 use crate::shims::windows::*;
 use crate::*;
@@ -248,32 +247,63 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                 let size = this.read_target_usize(size)?;
                 let heap_zero_memory = 0x00000008; // HEAP_ZERO_MEMORY
                 let zero_init = (flags & heap_zero_memory) == heap_zero_memory;
-                let res = this.malloc(size, zero_init, MiriMemoryKind::WinHeap)?;
-                this.write_pointer(res, dest)?;
+                // Alignment is twice the pointer size.
+                // Source: <https://learn.microsoft.com/en-us/windows/win32/api/heapapi/nf-heapapi-heapalloc>
+                let align = this.tcx.pointer_size().bytes().strict_mul(2);
+                let ptr = this.allocate_ptr(
+                    Size::from_bytes(size),
+                    Align::from_bytes(align).unwrap(),
+                    MiriMemoryKind::WinHeap.into(),
+                )?;
+                if zero_init {
+                    this.write_bytes_ptr(
+                        ptr.into(),
+                        iter::repeat(0u8).take(usize::try_from(size).unwrap()),
+                    )?;
+                }
+                this.write_pointer(ptr, dest)?;
             }
             "HeapFree" => {
                 let [handle, flags, ptr] =
                     this.check_shim(abi, Abi::System { unwind: false }, link_name, args)?;
                 this.read_target_isize(handle)?;
                 this.read_scalar(flags)?.to_u32()?;
                 let ptr = this.read_pointer(ptr)?;
-                this.free(ptr, MiriMemoryKind::WinHeap)?;
+                // "This pointer can be NULL." It doesn't say what happens then, but presumably nothing.
+                // (https://learn.microsoft.com/en-us/windows/win32/api/heapapi/nf-heapapi-heapfree)
+                if !this.ptr_is_null(ptr)? {
+                    this.deallocate_ptr(ptr, None, MiriMemoryKind::WinHeap.into())?;
+                }
                 this.write_scalar(Scalar::from_i32(1), dest)?;
             }
             "HeapReAlloc" => {
-                let [handle, flags, ptr, size] =
+                let [handle, flags, old_ptr, size] =
                     this.check_shim(abi, Abi::System { unwind: false }, link_name, args)?;
                 this.read_target_isize(handle)?;
                 this.read_scalar(flags)?.to_u32()?;
-                let ptr = this.read_pointer(ptr)?;
+                let old_ptr = this.read_pointer(old_ptr)?;
                 let size = this.read_target_usize(size)?;
-                let res = this.realloc(ptr, size, MiriMemoryKind::WinHeap)?;
-                this.write_pointer(res, dest)?;
+                let align = this.tcx.pointer_size().bytes().strict_mul(2); // same as above
+                // The docs say that `old_ptr` must come from an earlier HeapAlloc or HeapReAlloc,
+                // so unlike C `realloc` we do *not* allow a NULL here.
+                // (https://learn.microsoft.com/en-us/windows/win32/api/heapapi/nf-heapapi-heaprealloc)
+                let new_ptr = this.reallocate_ptr(
+                    old_ptr,
+                    None,
+                    Size::from_bytes(size),
+                    Align::from_bytes(align).unwrap(),
+                    MiriMemoryKind::WinHeap.into(),
+                )?;
+                this.write_pointer(new_ptr, dest)?;
             }
             "LocalFree" => {
                 let [ptr] = this.check_shim(abi, Abi::System { unwind: false }, link_name, args)?;
                 let ptr = this.read_pointer(ptr)?;
-                this.free(ptr, MiriMemoryKind::WinLocal)?;
+                // "If the hMem parameter is NULL, LocalFree ignores the parameter and returns NULL."
+                // (https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-localfree)
+                if !this.ptr_is_null(ptr)? {
+                    this.deallocate_ptr(ptr, None, MiriMemoryKind::WinLocal.into())?;
+                }
                 this.write_null(dest)?;
             }