Target stack-probe support configurable finely

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -13,6 +13,7 @@ use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::config::{OptLevel, SanitizerSet};
 use rustc_session::Session;
+use rustc_target::spec::StackProbeType;
 
 use crate::attributes;
 use crate::llvm::AttributePlace::Function;
@@ -98,12 +99,6 @@ fn set_instrument_function(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
 }
 
 fn set_probestack(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
-    // Only use stack probes if the target specification indicates that we
-    // should be using stack probes
-    if !cx.sess().target.stack_probes {
-        return;
-    }
-
     // Currently stack probes seem somewhat incompatible with the address
     // sanitizer and thread sanitizer. With asan we're already protected from
     // stack overflow anyway so we don't really need stack probes regardless.
@@ -127,19 +122,31 @@ fn set_probestack(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
         return;
     }
 
-    llvm::AddFunctionAttrStringValue(
-        llfn,
-        llvm::AttributePlace::Function,
-        const_cstr!("probe-stack"),
-        if llvm_util::get_version() < (11, 0, 1) {
-            // Flag our internal `__rust_probestack` function as the stack probe symbol.
-            // This is defined in the `compiler-builtins` crate for each architecture.
-            const_cstr!("__rust_probestack")
-        } else {
-            // On LLVM 11+, emit inline asm for stack probes instead of a function call.
-            const_cstr!("inline-asm")
-        },
-    );
+    let attr_value = match cx.sess().target.stack_probes {
+        StackProbeType::None => None,
+        // Request LLVM to generate the probes inline. If the given LLVM version does not support
+        // this, no probe is generated at all (even if the attribute is specified).
+        StackProbeType::Inline => Some(const_cstr!("inline-asm")),
+        // Flag our internal `__rust_probestack` function as the stack probe symbol.
+        // This is defined in the `compiler-builtins` crate for each architecture.
+        StackProbeType::Call => Some(const_cstr!("__rust_probestack")),
+        // Pick from the two above based on the LLVM version.
+        StackProbeType::InlineOrCall { min_llvm_version_for_inline } => {
+            if llvm_util::get_version() < min_llvm_version_for_inline {
+                Some(const_cstr!("__rust_probestack"))
+            } else {
+                Some(const_cstr!("inline-asm"))
+            }
+        }
+    };
+    if let Some(attr_value) = attr_value {
+        llvm::AddFunctionAttrStringValue(
+            llfn,
+            llvm::AttributePlace::Function,
+            const_cstr!("probe-stack"),
+            attr_value,
+        );
+    }
 }
 
 pub fn llvm_target_features(sess: &Session) -> impl Iterator<Item = &str> {

compiler/rustc_target/src/spec/i386_apple_ios.rs

@@ -1,5 +1,5 @@
 use super::apple_sdk_base::{opts, Arch};
-use crate::spec::{Target, TargetOptions};
+use crate::spec::{StackProbeType, Target, TargetOptions};
 
 pub fn target() -> Target {
     let base = opts("ios", Arch::I386);
@@ -10,6 +10,10 @@ pub fn target() -> Target {
             f64:32:64-f80:128-n8:16:32-S128"
             .to_string(),
         arch: "x86".to_string(),
-        options: TargetOptions { max_atomic_width: Some(64), stack_probes: true, ..base },
+        options: TargetOptions {
+            max_atomic_width: Some(64),
+            stack_probes: StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) },
+            ..base
+        },
     }
 }

compiler/rustc_target/src/spec/i686_apple_darwin.rs

@@ -1,12 +1,12 @@
-use crate::spec::{LinkerFlavor, Target, TargetOptions};
+use crate::spec::{LinkerFlavor, StackProbeType, Target, TargetOptions};
 
 pub fn target() -> Target {
     let mut base = super::apple_base::opts("macos");
     base.cpu = "yonah".to_string();
     base.max_atomic_width = Some(64);
     base.pre_link_args.insert(LinkerFlavor::Gcc, vec!["-m32".to_string()]);
     base.link_env_remove.extend(super::apple_base::macos_link_env_remove());
-    base.stack_probes = true;
+    base.stack_probes = StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) };
     base.eliminate_frame_pointer = false;
 
     // Clang automatically chooses a more specific target based on

compiler/rustc_target/src/spec/i686_linux_android.rs

@@ -1,4 +1,4 @@
-use crate::spec::Target;
+use crate::spec::{StackProbeType, Target};
 
 // See https://developer.android.com/ndk/guides/abis.html#x86
 // for target ABI requirements.
@@ -11,7 +11,7 @@ pub fn target() -> Target {
     // http://developer.android.com/ndk/guides/abis.html#x86
     base.cpu = "pentiumpro".to_string();
     base.features = "+mmx,+sse,+sse2,+sse3,+ssse3".to_string();
-    base.stack_probes = true;
+    base.stack_probes = StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) };
 
     Target {
         llvm_target: "i686-linux-android".to_string(),

compiler/rustc_target/src/spec/i686_unknown_freebsd.rs

@@ -1,4 +1,4 @@
-use crate::spec::{LinkerFlavor, Target};
+use crate::spec::{LinkerFlavor, StackProbeType, Target};
 
 pub fn target() -> Target {
     let mut base = super::freebsd_base::opts();
@@ -7,7 +7,7 @@ pub fn target() -> Target {
     let pre_link_args = base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap();
     pre_link_args.push("-m32".to_string());
     pre_link_args.push("-Wl,-znotext".to_string());
-    base.stack_probes = true;
+    base.stack_probes = StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) };
 
     Target {
         llvm_target: "i686-unknown-freebsd".to_string(),

compiler/rustc_target/src/spec/i686_unknown_haiku.rs

@@ -1,11 +1,11 @@
-use crate::spec::{LinkerFlavor, Target};
+use crate::spec::{LinkerFlavor, StackProbeType, Target};
 
 pub fn target() -> Target {
     let mut base = super::haiku_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = Some(64);
     base.pre_link_args.insert(LinkerFlavor::Gcc, vec!["-m32".to_string()]);
-    base.stack_probes = true;
+    base.stack_probes = StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) };
 
     Target {
         llvm_target: "i686-unknown-haiku".to_string(),

compiler/rustc_target/src/spec/i686_unknown_linux_gnu.rs

@@ -1,11 +1,11 @@
-use crate::spec::{LinkerFlavor, Target};
+use crate::spec::{LinkerFlavor, StackProbeType, Target};
 
 pub fn target() -> Target {
     let mut base = super::linux_gnu_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = Some(64);
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m32".to_string());
-    base.stack_probes = true;
+    base.stack_probes = StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) };
 
     Target {
         llvm_target: "i686-unknown-linux-gnu".to_string(),

compiler/rustc_target/src/spec/i686_unknown_linux_musl.rs

@@ -1,12 +1,12 @@
-use crate::spec::{LinkerFlavor, Target};
+use crate::spec::{LinkerFlavor, StackProbeType, Target};
 
 pub fn target() -> Target {
     let mut base = super::linux_musl_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = Some(64);
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m32".to_string());
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-Wl,-melf_i386".to_string());
-    base.stack_probes = true;
+    base.stack_probes = StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) };
 
     // The unwinder used by i686-unknown-linux-musl, the LLVM libunwind
     // implementation, apparently relies on frame pointers existing... somehow.

compiler/rustc_target/src/spec/i686_unknown_netbsd.rs

@@ -1,11 +1,11 @@
-use crate::spec::{LinkerFlavor, Target, TargetOptions};
+use crate::spec::{LinkerFlavor, StackProbeType, Target, TargetOptions};
 
 pub fn target() -> Target {
     let mut base = super::netbsd_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = Some(64);
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m32".to_string());
-    base.stack_probes = true;
+    base.stack_probes = StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) };
 
     Target {
         llvm_target: "i686-unknown-netbsdelf".to_string(),

compiler/rustc_target/src/spec/i686_unknown_openbsd.rs

@@ -1,12 +1,12 @@
-use crate::spec::{LinkerFlavor, Target};
+use crate::spec::{LinkerFlavor, StackProbeType, Target};
 
 pub fn target() -> Target {
     let mut base = super::openbsd_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = Some(64);
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m32".to_string());
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-fuse-ld=lld".to_string());
-    base.stack_probes = true;
+    base.stack_probes = StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) };
 
     Target {
         llvm_target: "i686-unknown-openbsd".to_string(),

compiler/rustc_target/src/spec/i686_wrs_vxworks.rs

@@ -1,11 +1,11 @@
-use crate::spec::{LinkerFlavor, Target};
+use crate::spec::{LinkerFlavor, StackProbeType, Target};
 
 pub fn target() -> Target {
     let mut base = super::vxworks_base::opts();
     base.cpu = "pentium4".to_string();
     base.max_atomic_width = Some(64);
     base.pre_link_args.get_mut(&LinkerFlavor::Gcc).unwrap().push("-m32".to_string());
-    base.stack_probes = true;
+    base.stack_probes = StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) };
 
     Target {
         llvm_target: "i686-unknown-linux-gnu".to_string(),

compiler/rustc_target/src/spec/linux_kernel_base.rs

@@ -1,4 +1,6 @@
-use crate::spec::{LinkArgs, LinkerFlavor, PanicStrategy, RelocModel, RelroLevel, TargetOptions};
+use crate::spec::{
+    LinkArgs, LinkerFlavor, PanicStrategy, RelocModel, RelroLevel, StackProbeType, TargetOptions,
+};
 
 pub fn opts() -> TargetOptions {
     let mut pre_link_args = LinkArgs::new();
@@ -11,7 +13,7 @@ pub fn opts() -> TargetOptions {
         env: "gnu".to_string(),
         disable_redzone: true,
         panic_strategy: PanicStrategy::Abort,
-        stack_probes: true,
+        stack_probes: StackProbeType::InlineOrCall { min_llvm_version_for_inline: (11, 0, 1) },
         eliminate_frame_pointer: false,
         linker_is_gnu: true,
         position_independent_executables: true,

compiler/rustc_target/src/spec/mod.rs

@@ -40,6 +40,7 @@ use crate::spec::crt_objects::{CrtObjects, CrtObjectsFallback};
 use rustc_serialize::json::{Json, ToJson};
 use rustc_span::symbol::{sym, Symbol};
 use std::collections::BTreeMap;
+use std::convert::TryFrom;
 use std::ops::{Deref, DerefMut};
 use std::path::{Path, PathBuf};
 use std::str::FromStr;
@@ -479,6 +480,83 @@ macro_rules! supported_targets {
     };
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum StackProbeType {
+    /// Don't emit any stack probes.
+    None,
+    /// It is harmless to use this option even on targets that do not have backend support for
+    /// stack probes as the failure mode is the same as if no stack-probe option was specified in
+    /// the first place.
+    Inline,
+    /// Call `__rust_probestack` whenever stack needs to be probed.
+    Call,
+    /// Use inline option for LLVM versions later than specified in `min_llvm_version_for_inline`
+    /// and call `__rust_probestack` otherwise.
+    InlineOrCall { min_llvm_version_for_inline: (u32, u32, u32) },
+}
+
+impl StackProbeType {
+    fn from_json(json: &Json) -> Result<Self, String> {
+        let object = json.as_object().ok_or_else(|| "expected a JSON object")?;
+        let kind = object
+            .get("kind")
+            .and_then(|o| o.as_string())
+            .ok_or_else(|| "expected `kind` to be a string")?;
+        match kind {
+            "none" => Ok(StackProbeType::None),
+            "inline" => Ok(StackProbeType::Inline),
+            "call" => Ok(StackProbeType::Call),
+            "inline-or-call" => {
+                let min_version = object
+                    .get("min-llvm-version-for-inline")
+                    .and_then(|o| o.as_array())
+                    .ok_or_else(|| "expected `min-llvm-version-for-inline` to be an array")?;
+                let mut iter = min_version.into_iter().map(|v| {
+                    let int = v.as_u64().ok_or_else(
+                        || "expected `min-llvm-version-for-inline` values to be integers",
+                    )?;
+                    u32::try_from(int)
+                        .map_err(|_| "`min-llvm-version-for-inline` values don't convert to u32")
+                });
+                let min_llvm_version_for_inline = (
+                    iter.next().unwrap_or(Ok(11))?,
+                    iter.next().unwrap_or(Ok(0))?,
+                    iter.next().unwrap_or(Ok(0))?,
+                );
+                Ok(StackProbeType::InlineOrCall { min_llvm_version_for_inline })
+            }
+            _ => Err(String::from(
+                "`kind` expected to be one of `inline-or-none`, `call` or `inline-or-call`",
+            )),
+        }
+    }
+}
+
+impl ToJson for StackProbeType {
+    fn to_json(&self) -> Json {
+        Json::Object(match self {
+            StackProbeType::None => {
+                vec![(String::from("kind"), "none".to_json())].into_iter().collect()
+            }
+            StackProbeType::Inline => {
+                vec![(String::from("kind"), "inline".to_json())].into_iter().collect()
+            }
+            StackProbeType::Call => {
+                vec![(String::from("kind"), "call".to_json())].into_iter().collect()
+            }
+            StackProbeType::InlineOrCall { min_llvm_version_for_inline } => vec![
+                (String::from("kind"), "inline-or-call".to_json()),
+                (
+                    String::from("min-llvm-version-for-inline"),
+                    min_llvm_version_for_inline.to_json(),
+                ),
+            ]
+            .into_iter()
+            .collect(),
+        })
+    }
+}
+
 supported_targets! {
     ("x86_64-unknown-linux-gnu", x86_64_unknown_linux_gnu),
     ("x86_64-unknown-linux-gnux32", x86_64_unknown_linux_gnux32),
@@ -926,8 +1004,8 @@ pub struct TargetOptions {
     /// Whether or not crt-static is respected by the compiler (or is a no-op).
     pub crt_static_respected: bool,
 
-    /// Whether or not stack probes (__rust_probestack) are enabled
-    pub stack_probes: bool,
+    /// The implementation of stack probes to use.
+    pub stack_probes: StackProbeType,
 
     /// The minimum alignment for global symbols.
     pub min_global_align: Option<u64>,
@@ -1085,7 +1163,7 @@ impl Default for TargetOptions {
             crt_static_allows_dylibs: false,
             crt_static_default: false,
             crt_static_respected: false,
-            stack_probes: false,
+            stack_probes: StackProbeType::None,
             min_global_align: None,
             default_codegen_units: None,
             trap_unreachable: true,
@@ -1361,6 +1439,18 @@ impl Target {
                     Some(Ok(()))
                 })).unwrap_or(Ok(()))
             } );
+            ($key_name:ident, StackProbeType) => ( {
+                let name = (stringify!($key_name)).replace("_", "-");
+                obj.find(&name[..]).and_then(|o| match StackProbeType::from_json(o) {
+                    Ok(v) => {
+                        base.$key_name = v;
+                        Some(Ok(()))
+                    },
+                    Err(s) => Some(Err(
+                        format!("`{:?}` is not a valid value for `{}`: {}", o, name, s)
+                    )),
+                }).unwrap_or(Ok(()))
+            } );
             ($key_name:ident, crt_objects_fallback) => ( {
                 let name = (stringify!($key_name)).replace("_", "-");
                 obj.find(&name[..]).and_then(|o| o.as_string().and_then(|s| {
@@ -1516,7 +1606,7 @@ impl Target {
         key!(crt_static_allows_dylibs, bool);
         key!(crt_static_default, bool);
         key!(crt_static_respected, bool);
-        key!(stack_probes, bool);
+        key!(stack_probes, StackProbeType)?;
         key!(min_global_align, Option<u64>);
         key!(default_codegen_units, Option<u64>);
         key!(trap_unreachable, bool);

compiler/rustc_target/src/spec/uefi_msvc_base.rs

@@ -9,7 +9,7 @@
 // the timer-interrupt. Device-drivers are required to use polling-based models. Furthermore, all
 // code runs in the same environment, no process separation is supported.
 
-use crate::spec::{LinkerFlavor, LldFlavor, PanicStrategy, TargetOptions};
+use crate::spec::{LinkerFlavor, LldFlavor, PanicStrategy, StackProbeType, TargetOptions};
 
 pub fn opts() -> TargetOptions {
     let mut base = super::msvc_base::opts();
@@ -43,7 +43,9 @@ pub fn opts() -> TargetOptions {
         exe_suffix: ".efi".to_string(),
         allows_weak_linkage: false,
         panic_strategy: PanicStrategy::Abort,
-        stack_probes: true,
+        // LLVM does not emit inline assembly because the LLVM target does not get considered as…
+        // "Windows".
+        stack_probes: StackProbeType::Call,
         singlethread: true,
         linker: Some("rust-lld".to_string()),
         ..base