add new version of backtrace api using flags=1

Author: beepster4096

src/shims/backtrace.rs

@@ -1,29 +1,49 @@
 use crate::*;
 use rustc_ast::ast::Mutability;
 use rustc_middle::ty::layout::LayoutOf as _;
-use rustc_middle::ty::{self, TypeAndMut};
-use rustc_span::{BytePos, Symbol};
+use rustc_middle::ty::{self, Instance, TypeAndMut};
+use rustc_span::{BytePos, Loc, Symbol};
 use rustc_target::{abi::Size, spec::abi::Abi};
 use std::convert::TryInto as _;
 
 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
-    fn handle_miri_get_backtrace(
+    fn handle_miri_backtrace_size(
         &mut self,
         abi: Abi,
         link_name: Symbol,
         args: &[OpTy<'tcx, Tag>],
         dest: &PlaceTy<'tcx, Tag>,
     ) -> InterpResult<'tcx> {
         let this = self.eval_context_mut();
-        let tcx = this.tcx;
         let &[ref flags] = this.check_shim(abi, Abi::Rust, link_name, args)?;
 
         let flags = this.read_scalar(flags)?.to_u64()?;
-        if flags != 0 {
-            throw_unsup_format!("unknown `miri_get_backtrace` flags {}", flags);
+        if flags != 1 {
+            throw_unsup_format!("unknown `miri_backtrace_size` flags {}", flags);
         }
 
+        let frame_count = this.active_thread_stack().len();
+
+        this.write_scalar(Scalar::from_machine_usize(frame_count.try_into().unwrap(), this), dest)
+    }
+
+    fn handle_miri_get_backtrace(
+        &mut self,
+        abi: Abi,
+        link_name: Symbol,
+        args: &[OpTy<'tcx, Tag>],
+        dest: &PlaceTy<'tcx, Tag>,
+    ) -> InterpResult<'tcx> {
+        let this = self.eval_context_mut();
+        let tcx = this.tcx;
+
+        let flags = if let Some(flags_op) = args.get(0) {
+            this.read_scalar(flags_op)?.to_u64()?
+        } else {
+            throw_ub_format!("expected at least 1 argument")
+        };
+
         let mut data = Vec::new();
         for frame in this.active_thread_stack().iter().rev() {
             let mut span = frame.current_span();
@@ -49,46 +69,69 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             })
             .collect();
 
-        let len = ptrs.len();
+        let len = ptrs.len().try_into().unwrap();
 
         let ptr_ty = tcx.mk_ptr(TypeAndMut { ty: tcx.types.unit, mutbl: Mutability::Mut });
 
-        let array_ty = tcx.mk_array(ptr_ty, ptrs.len().try_into().unwrap());
+        let array_ty = this.layout_of(tcx.mk_array(ptr_ty, len)).unwrap();
 
-        // Write pointers into array
-        let alloc =
-            this.allocate(this.layout_of(array_ty).unwrap(), MiriMemoryKind::Rust.into())?;
-        for (i, ptr) in ptrs.into_iter().enumerate() {
-            let place = this.mplace_index(&alloc, i as u64)?;
-            this.write_pointer(ptr, &place.into())?;
-        }
+        match flags {
+            // storage for pointers is allocated by miri
+            // deallocating the slice is undefined behavior with a custom global allocator
+            0 => {
+                let &[_] = this.check_shim(abi, Abi::Rust, link_name, args)?;
+
+                let alloc = this.allocate(array_ty, MiriMemoryKind::Rust.into())?;
+
+                // Write pointers into array
+                for (i, ptr) in ptrs.into_iter().enumerate() {
+                    let place = this.mplace_index(&alloc, i as u64)?;
+
+                    this.write_pointer(ptr, &place.into())?;
+                }
+
+                this.write_immediate(
+                    Immediate::new_slice(Scalar::from_maybe_pointer(alloc.ptr, this), len, this),
+                    dest,
+                )?;
+            }
+            // storage for pointers is allocated by the caller
+            1 => {
+                let &[_, ref buf] = this.check_shim(abi, Abi::Rust, link_name, args)?;
+
+                this.memory.check_ptr_access_align(
+                    this.read_pointer(buf)?,
+                    array_ty.size,
+                    array_ty.align.abi,
+                    CheckInAllocMsg::MemoryAccessTest,
+                )?;
+
+                let ptr_layout = this.layout_of(ptr_ty)?;
+
+                for (i, ptr) in ptrs.into_iter().enumerate() {
+                    let offset = ptr_layout.size * i.try_into().unwrap();
+
+                    let op_place = this.deref_operand(buf)?.offset(
+                        offset,
+                        MemPlaceMeta::None,
+                        ptr_layout,
+                        this,
+                    )?;
+
+                    this.write_pointer(ptr, &op_place.into())?;
+                }
+            }
+            _ => throw_unsup_format!("unknown `miri_get_backtrace` flags {}", flags),
+        };
 
-        this.write_immediate(
-            Immediate::new_slice(
-                Scalar::from_maybe_pointer(alloc.ptr, this),
-                len.try_into().unwrap(),
-                this,
-            ),
-            dest,
-        )?;
         Ok(())
     }
 
-    fn handle_miri_resolve_frame(
+    fn resolve_frame_pointer(
         &mut self,
-        abi: Abi,
-        link_name: Symbol,
-        args: &[OpTy<'tcx, Tag>],
-        dest: &PlaceTy<'tcx, Tag>,
-    ) -> InterpResult<'tcx> {
+        ptr: &OpTy<'tcx, Tag>,
+    ) -> InterpResult<'tcx, (Instance<'tcx>, Loc)> {
         let this = self.eval_context_mut();
-        let tcx = this.tcx;
-        let &[ref ptr, ref flags] = this.check_shim(abi, Abi::Rust, link_name, args)?;
-
-        let flags = this.read_scalar(flags)?.to_u64()?;
-        if flags != 0 {
-            throw_unsup_format!("unknown `miri_resolve_frame` flags {}", flags);
-        }
 
         let ptr = this.read_pointer(ptr)?;
         // Take apart the pointer, we need its pieces.
@@ -101,6 +144,26 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 throw_ub_format!("expected function pointer, found {:?}", ptr);
             };
 
+        let lo =
+            this.tcx.sess.source_map().lookup_char_pos(BytePos(offset.bytes().try_into().unwrap()));
+
+        Ok((fn_instance, lo))
+    }
+
+    fn handle_miri_resolve_frame(
+        &mut self,
+        abi: Abi,
+        link_name: Symbol,
+        args: &[OpTy<'tcx, Tag>],
+        dest: &PlaceTy<'tcx, Tag>,
+    ) -> InterpResult<'tcx> {
+        let this = self.eval_context_mut();
+        let &[ref ptr, ref flags] = this.check_shim(abi, Abi::Rust, link_name, args)?;
+
+        let flags = this.read_scalar(flags)?.to_u64()?;
+
+        let (fn_instance, lo) = this.resolve_frame_pointer(ptr)?;
+
         // Reconstruct the original function pointer,
         // which we pass to user code.
         let fn_ptr = this.memory.create_fn_alloc(FnVal::Instance(fn_instance));
@@ -115,23 +178,13 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             );
         }
 
-        let pos = BytePos(offset.bytes().try_into().unwrap());
         let name = fn_instance.to_string();
 
-        let lo = tcx.sess.source_map().lookup_char_pos(pos);
-
         let filename = lo.file.name.prefer_remapped().to_string();
         let lineno: u32 = lo.line as u32;
         // `lo.col` is 0-based - add 1 to make it 1-based for the caller.
         let colno: u32 = lo.col.0 as u32 + 1;
 
-        // These are "mutable" allocations as we consider them to be owned by the callee.
-        let name_alloc = this.allocate_str(&name, MiriMemoryKind::Rust.into(), Mutability::Mut);
-        let filename_alloc =
-            this.allocate_str(&filename, MiriMemoryKind::Rust.into(), Mutability::Mut);
-        let lineno_alloc = Scalar::from_u32(lineno);
-        let colno_alloc = Scalar::from_u32(colno);
-
         let dest = this.force_allocation(dest)?;
         if let ty::Adt(adt, _) = dest.layout.ty.kind() {
             if !adt.repr.c() {
@@ -141,10 +194,38 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             }
         }
 
-        this.write_immediate(name_alloc.to_ref(this), &this.mplace_field(&dest, 0)?.into())?;
-        this.write_immediate(filename_alloc.to_ref(this), &this.mplace_field(&dest, 1)?.into())?;
-        this.write_scalar(lineno_alloc, &this.mplace_field(&dest, 2)?.into())?;
-        this.write_scalar(colno_alloc, &this.mplace_field(&dest, 3)?.into())?;
+        match flags {
+            0 => {
+                // These are "mutable" allocations as we consider them to be owned by the callee.
+                let name_alloc =
+                    this.allocate_str(&name, MiriMemoryKind::Rust.into(), Mutability::Mut);
+                let filename_alloc =
+                    this.allocate_str(&filename, MiriMemoryKind::Rust.into(), Mutability::Mut);
+
+                this.write_immediate(
+                    name_alloc.to_ref(this),
+                    &this.mplace_field(&dest, 0)?.into(),
+                )?;
+                this.write_immediate(
+                    filename_alloc.to_ref(this),
+                    &this.mplace_field(&dest, 1)?.into(),
+                )?;
+            }
+            1 => {
+                this.write_scalar(
+                    Scalar::from_machine_usize(name.len().try_into().unwrap(), this),
+                    &this.mplace_field(&dest, 0)?.into(),
+                )?;
+                this.write_scalar(
+                    Scalar::from_machine_usize(filename.len().try_into().unwrap(), this),
+                    &this.mplace_field(&dest, 1)?.into(),
+                )?;
+            }
+            _ => throw_unsup_format!("unknown `miri_resolve_frame` flags {}", flags),
+        }
+
+        this.write_scalar(Scalar::from_u32(lineno), &this.mplace_field(&dest, 2)?.into())?;
+        this.write_scalar(Scalar::from_u32(colno), &this.mplace_field(&dest, 3)?.into())?;
 
         // Support a 4-field struct for now - this is deprecated
         // and slated for removal.
@@ -154,4 +235,32 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
         Ok(())
     }
+
+    fn handle_miri_resolve_frame_names(
+        &mut self,
+        abi: Abi,
+        link_name: Symbol,
+        args: &[OpTy<'tcx, Tag>],
+        dest: &PlaceTy<'tcx, Tag>,
+    ) -> InterpResult<'tcx> {
+        let this = self.eval_context_mut();
+
+        let &[ref ptr, ref flags, ref name_ptr, ref filename_ptr] =
+            this.check_shim(abi, Abi::Rust, link_name, args)?;
+
+        let flags = this.read_scalar(flags)?.to_u64()?;
+        if flags != 1 {
+            throw_unsup_format!("unknown `miri_backtrace_size` flags {}", flags);
+        }
+
+        let (fn_instance, lo) = this.resolve_frame_pointer(ptr)?;
+
+        let name = fn_instance.to_string();
+        let filename = lo.file.name.prefer_remapped().to_string();
+
+        this.memory.write_bytes(this.read_pointer(name_ptr)?, name.bytes())?;
+        this.memory.write_bytes(this.read_pointer(filename_ptr)?, filename.bytes())?;
+
+        Ok(())
+    }
 }

src/shims/foreign_items.rs

@@ -380,6 +380,10 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 this.machine.static_roots.push(alloc_id);
             }
 
+            "miri_backtrace_size" => {
+                this.handle_miri_backtrace_size(abi, link_name, args, dest)?;
+            }
+
             // Obtains a Miri backtrace. See the README for details.
             "miri_get_backtrace" => {
                 // `check_shim` happens inside `handle_miri_get_backtrace`.
@@ -392,6 +396,9 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 this.handle_miri_resolve_frame(abi, link_name, args, dest)?;
             }
 
+            "miri_resolve_frame_names" => {
+                this.handle_miri_resolve_frame_names(abi, link_name, args, dest)?;
+            }
 
             // Standard C allocation
             "malloc" => {

tests/run-pass/backtrace-api.rs renamed to tests/run-pass/backtrace-api-v0.rs

@@ -1,8 +1,8 @@
-$DIR/backtrace-api.rs:13:59 (func_d)
-$DIR/backtrace-api.rs:12:50 (func_c)
-$DIR/backtrace-api.rs:6:53 (func_b)
-$DIR/backtrace-api.rs:5:50 (func_a)
-$DIR/backtrace-api.rs:17:18 (main)
+$DIR/backtrace-api-v0.rs:13:59 (func_d)
+$DIR/backtrace-api-v0.rs:12:50 (func_c)
+$DIR/backtrace-api-v0.rs:6:53 (func_b)
+$DIR/backtrace-api-v0.rs:5:50 (func_a)
+$DIR/backtrace-api-v0.rs:17:18 (main)
 RUSTLIB/core/src/ops/function.rs:LL:COL (<fn() as std::ops::FnOnce<()>>::call_once - shim(fn()))
 RUSTLIB/std/src/sys_common/backtrace.rs:LL:COL (std::sys_common::backtrace::__rust_begin_short_backtrace)
 RUSTLIB/std/src/rt.rs:LL:COL (std::rt::lang_start::{closure#0})

tests/run-pass/backtrace-api.stderr renamed to tests/run-pass/backtrace-api-v0.stderr

@@ -0,0 +1,5 @@
+$DIR/backtrace-api-v0.rs:13:59 (func_d)
+$DIR/backtrace-api-v0.rs:12:50 (func_c)
+$DIR/backtrace-api-v0.rs:6:53 (func_b::<u8>)
+$DIR/backtrace-api-v0.rs:5:50 (func_a)
+$DIR/backtrace-api-v0.rs:17:18 (main)

tests/run-pass/backtrace-api-v0.stdout

@@ -0,0 +1,65 @@
+// normalize-stderr-test ".*/(rust[^/]*|checkout)/library/" -> "RUSTLIB/"
+// normalize-stderr-test "RUSTLIB/(.*):\d+:\d+ "-> "RUSTLIB/$1:LL:COL "
+// normalize-stderr-test "::<.*>" -> ""
+
+#[inline(never)] fn func_a() -> Box<[*mut ()]> { func_b::<u8>() }
+#[inline(never)] fn func_b<T>() -> Box<[*mut ()]> { func_c() }
+
+macro_rules! invoke_func_d {
+    () => { func_d() }
+}
+
+#[inline(never)] fn func_c() -> Box<[*mut ()]> { invoke_func_d!() }
+#[inline(never)] fn func_d() -> Box<[*mut ()]> { unsafe { let count = miri_backtrace_size(1); let mut buf = vec![std::ptr::null_mut(); count]; miri_get_backtrace(1, buf.as_mut_ptr()); buf.into() } }
+
+fn main() {
+    let mut seen_main = false;
+    let frames = func_a();
+    for frame in frames.into_iter() {
+        let miri_frame = unsafe { miri_resolve_frame(*frame, 1) };
+
+        let mut name = vec![0; miri_frame.name_len];
+        let mut filename = vec![0; miri_frame.filename_len];
+
+        unsafe {
+            miri_resolve_frame_names(*frame, 1, name.as_mut_ptr(), filename.as_mut_ptr());
+        }
+        
+        let name = String::from_utf8(name).unwrap();
+        let filename = String::from_utf8(filename).unwrap();
+
+        if name == "func_a" {
+            assert_eq!(func_a as *mut (), miri_frame.fn_ptr);
+        }
+
+        // Print every frame to stderr.
+        let out = format!("{}:{}:{} ({})", filename, miri_frame.lineno, miri_frame.colno, name);
+        eprintln!("{}", out);
+        // Print the 'main' frame (and everything before it) to stdout, skipping
+        // the printing of internal (and possibly fragile) libstd frames.
+        if !seen_main {
+            println!("{}", out);
+            seen_main = name == "main";
+        }
+    }
+}
+
+// This goes at the bottom of the file so that we can change it
+// without disturbing line numbers of the functions in the backtrace.
+
+extern "Rust" {
+    fn miri_backtrace_size(flags: u64) -> usize;
+    fn miri_get_backtrace(flags: u64, buf: *mut *mut ());
+    fn miri_resolve_frame(ptr: *mut (), flags: u64) -> MiriFrame;
+    fn miri_resolve_frame_names(ptr: *mut (), flags: u64, name_buf: *mut u8, filename_buf: *mut u8);
+}
+
+#[derive(Debug)]
+#[repr(C)]
+struct MiriFrame {
+    name_len: usize,
+    filename_len: usize,
+    lineno: u32,
+    colno: u32,
+    fn_ptr: *mut (),
+}