Turn off segmented stack support and use stack probes instead

Fixes rust-lang#10781, rust-lang#11359, rust-lang#13259, rust-lang#14742 and rust-lang#16012.

src/librustc/middle/lang_items.rs

@@ -300,6 +300,4 @@ lets_do_this! {
     ManagedItem,                     "managed_bound",           managed_bound;
 
     IteratorItem,                    "iterator",                iterator;
-
-    StackExhaustedLangItem,          "stack_exhausted",         stack_exhausted;
 }

src/librustc/middle/trans/base.rs

@@ -204,8 +204,8 @@ fn decl_fn(ccx: &CrateContext, name: &str, cc: llvm::CallConv,
     // Function addresses in Rust are never significant, allowing functions to be merged.
     llvm::SetUnnamedAddr(llfn, true);
 
-    if ccx.is_split_stack_supported() {
-        set_split_stack(llfn);
+    if ccx.is_probe_stack_supported() {
+        set_probe_stack(llfn);
     }
 
     llfn
@@ -429,11 +429,6 @@ pub fn set_llvm_fn_attrs(attrs: &[ast::Attribute], llfn: ValueRef) {
         InlineNone   => { /* fallthrough */ }
     }
 
-    // Add the no-split-stack attribute if requested
-    if contains_name(attrs, "no_split_stack") {
-        unset_split_stack(llfn);
-    }
-
     if contains_name(attrs, "cold") {
         unsafe {
             llvm::LLVMAddFunctionAttribute(llfn,
@@ -447,14 +442,14 @@ pub fn set_always_inline(f: ValueRef) {
     llvm::SetFunctionAttribute(f, llvm::AlwaysInlineAttribute)
 }
 
-pub fn set_split_stack(f: ValueRef) {
-    "split-stack".with_c_str(|buf| {
+pub fn set_probe_stack(f: ValueRef) {
+    "probe-stack".with_c_str(|buf| {
         unsafe { llvm::LLVMAddFunctionAttrString(f, llvm::FunctionIndex as c_uint, buf); }
     })
 }
 
-pub fn unset_split_stack(f: ValueRef) {
-    "split-stack".with_c_str(|buf| {
+pub fn unset_probe_stack(f: ValueRef) {
+    "probe-stack".with_c_str(|buf| {
         unsafe { llvm::LLVMRemoveFunctionAttrString(f, llvm::FunctionIndex as c_uint, buf); }
     })
 }
@@ -2009,14 +2004,8 @@ fn finish_register_fn(ccx: &CrateContext, sp: Span, sym: String, node_id: ast::N
         llvm::SetLinkage(llfn, llvm::InternalLinkage);
     }
 
-    // The stack exhaustion lang item shouldn't have a split stack because
-    // otherwise it would continue to be exhausted (bad), and both it and the
-    // eh_personality functions need to be externally linkable.
+    // The eh_personality function need to be externally linkable.
     let def = ast_util::local_def(node_id);
-    if ccx.tcx.lang_items.stack_exhausted() == Some(def) {
-        unset_split_stack(llfn);
-        llvm::SetLinkage(llfn, llvm::ExternalLinkage);
-    }
     if ccx.tcx.lang_items.eh_personality() == Some(def) {
         llvm::SetLinkage(llfn, llvm::ExternalLinkage);
     }
@@ -2729,13 +2718,9 @@ pub fn trans_crate(krate: ast::Crate,
     });
 
     // Make sure that some other crucial symbols are not eliminated from the
-    // module. This includes the main function, the crate map (used for debug
-    // log settings and I/O), and finally the curious rust_stack_exhausted
-    // symbol. This symbol is required for use by the libmorestack library that
-    // we link in, so we must ensure that this symbol is not internalized (if
-    // defined in the crate).
+    // module. This includes the main function and the crate map (used for debug
+    // log settings and I/O)
     reachable.push("main".to_string());
-    reachable.push("rust_stack_exhausted".to_string());
 
     // referenced from .eh_frame section on some platforms
     reachable.push("rust_eh_personality".to_string());

src/librustc/middle/trans/context.rs

@@ -32,7 +32,6 @@ use std::c_str::ToCStr;
 use std::ptr;
 use std::rc::Rc;
 use std::collections::{HashMap, HashSet};
-use syntax::abi;
 use syntax::ast;
 use syntax::parse::token::InternedString;
 
@@ -275,16 +274,8 @@ impl CrateContext {
         }
     }
 
-    // Although there is an experimental implementation of LLVM which
-    // supports SS on armv7 it wasn't approved by Apple, see:
-    // http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20140505/216350.html
-    // It looks like it might be never accepted to upstream LLVM.
-    //
-    // So far the decision was to disable them in default builds
-    // but it could be enabled (with patched LLVM)
-    pub fn is_split_stack_supported(&self) -> bool {
-        let ref cfg = self.sess().targ_cfg;
-        cfg.os != abi::OsiOS || cfg.arch != abi::Arm
+    pub fn is_probe_stack_supported(&self) -> bool {
+        true
     }
 }
 

src/librustc/middle/weak_lang_items.rs

@@ -38,9 +38,6 @@ pub fn check_crate(krate: &ast::Crate,
     // These are never called by user code, they're generated by the compiler.
     // They will never implicitly be added to the `missing` array unless we do
     // so here.
-    if items.stack_exhausted().is_none() {
-        items.missing.push(lang_items::StackExhaustedLangItem);
-    }
     if items.eh_personality().is_none() {
         items.missing.push(lang_items::EhPersonalityLangItem);
     }
@@ -119,6 +116,5 @@ impl<'a> Visitor<()> for Context<'a> {
 
 weak_lang_items!(
     begin_unwind,       BeginUnwindLangItem,        rust_begin_unwind;
-    stack_exhausted,    StackExhaustedLangItem,     rust_stack_exhausted;
     eh_personality,     EhPersonalityLangItem,      rust_eh_personality;
 )

src/rt/arch/arm/morestack.S

@@ -16,13 +16,10 @@
 
 #if defined(__APPLE__)
 #define MORESTACK ___morestack
-#define STACK_EXHAUSTED _rust_stack_exhausted
 #else
 #define MORESTACK __morestack
-#define STACK_EXHAUSTED rust_stack_exhausted
 #endif
 
-.global STACK_EXHAUSTED
 .global MORESTACK
 
 // Unfortunately LLVM yet doesn't support emitting correct debug
@@ -48,23 +45,5 @@
 // ARMFrameLowering::adjustForSegmentedStacks() implementation.
 MORESTACK:
     UNWIND .fnstart
-
-    // Save frame pointer and return address
-    UNWIND .save {r4, r5}
-    UNWIND .save {lr}
-    UNWIND .save {r6, fp, lr}
-    push {r6, fp, lr}
-
-    UNWIND .movsp r6
-    mov r6, sp
-    UNWIND .setfp fp, sp, #4
-    add fp, sp, #4
-
-    // Save argument registers of the original function
-    push {r0, r1, r2, r3, lr}
-
-    // Create new stack
-    bl STACK_EXHAUSTED@plt
-
-    // the above function ensures that it never returns
+    b   MORESTACK
     UNWIND  .fnend

src/rt/arch/i386/morestack.S

@@ -71,14 +71,11 @@
 
 #if defined(__APPLE__)
 #define MORESTACK               ___morestack
-#define EXHAUSTED               _rust_stack_exhausted
 #else
 #if defined(__linux__) || defined(__FreeBSD__)
 #define MORESTACK               __morestack
-#define EXHAUSTED               rust_stack_exhausted
 #else
 #define MORESTACK               ___morestack
-#define EXHAUSTED               _rust_stack_exhausted
 #endif
 #endif
 
@@ -100,45 +97,5 @@
 
 MORESTACK:
 	.cfi_startproc
-
-	// This base pointer setup differs from most in that we are
-	// telling the unwinder to consider the Canonical Frame
-	// Address (CFA) for this frame to be the value of the stack
-	// pointer prior to entry to the original function, whereas
-	// the CFA would typically be the value of the stack
-	// pointer prior to entry to this function. This will allow
-	// the unwinder to understand how to skip the tiny partial
-	// frame that the original function created by calling
-	// __morestack.
-
-	// In practical terms, our CFA is 12 bytes greater than it
-	// would normally be, accounting for the two arguments to
-	// __morestack, and an extra return address.
-
-        // FIXME(#9854) these cfi directives don't work on windows.
-
-	pushl %ebp
-
-#if defined(__APPLE__)
-	// The pattern of the return address being saved twice to the same location
-	// tells the OS X linker that it should not attempt to convert the DWARF
-	// unwind information to the compact format.
-	.cfi_offset %eip, -4
-	.cfi_offset %eip, -4
-#endif
-
-	// The CFA is 20 bytes above the register that it is
-	// associated with for this frame (which will be %ebp)
-	.cfi_def_cfa_offset 20
-	// %ebp is -20 bytes from the CFA
-	.cfi_offset %ebp, -20
-	movl %esp, %ebp
-	// Calculate the CFA as an offset from %ebp
-	.cfi_def_cfa_register %ebp
-
-        // re-align the stack
-        subl $12,%esp
-        calll EXHAUSTED
-        // the exhaustion function guarantees that it can't return
-
+	jmp MORESTACK
 	.cfi_endproc

src/rt/arch/mips/morestack.S

@@ -7,7 +7,6 @@
 
 .text
 
-.globl rust_stack_exhausted
 .globl __morestack
 
 .hidden __morestack
@@ -19,25 +18,8 @@ __morestack:
         .set noreorder
         .set nomacro
 
-        addiu $29, $29, -4
-        sw $30, 0($29)
-
-        // 16 = 4 (current) + 12 (previous)
-        .cfi_def_cfa_offset 16
-        .cfi_offset 31, -4
-        .cfi_offset 30, -16
-
-        move $30, $29
-        .cfi_def_cfa_register 30
-
-        // O32 ABI always reserves 16 bytes for arguments
-        addiu $29, $29, -16
-
-        lw $25, %call16(rust_stack_exhausted)($28)
-        jalr $25
+        b       __morestack
         nop
 
-        // the above function make sure that we never get here
-
 .end __morestack
 .cfi_endproc

src/rt/arch/mipsel/morestack.S

@@ -7,7 +7,6 @@
 
 .text
 
-.globl rust_stack_exhausted
 .globl __morestack
 
 .hidden __morestack
@@ -19,25 +18,8 @@ __morestack:
         .set noreorder
         .set nomacro
 
-        addiu $29, $29, -4
-        sw $30, 0($29)
-
-        // 16 = 4 (current) + 12 (previous)
-        .cfi_def_cfa_offset 16
-        .cfi_offset 31, -4
-        .cfi_offset 30, -16
-
-        move $30, $29
-        .cfi_def_cfa_register 30
-
-        // O32 ABI always reserves 16 bytes for arguments
-        addiu $29, $29, -16
-
-        lw $25, %call16(rust_stack_exhausted)($28)
-        jalr $25
+        b       __morestack
         nop
 
-        // the above function make sure that we never get here
-
 .end __morestack
 .cfi_endproc

src/rt/arch/x86_64/morestack.S

@@ -13,14 +13,6 @@
 #define MORESTACK               __morestack
 #endif
 
-#if defined(__APPLE__)
-#define EXHAUSTED               _rust_stack_exhausted
-#elif defined(__linux__) || defined(__FreeBSD__) || defined(__DragonFly__)
-#define EXHAUSTED               rust_stack_exhausted@PLT
-#else
-#define EXHAUSTED               rust_stack_exhausted
-#endif
-
 #if defined(__linux__) || defined(__FreeBSD__) || defined(__DragonFly__)
 	.hidden MORESTACK
 #else
@@ -36,34 +28,5 @@
 .globl MORESTACK
 MORESTACK:
 	.cfi_startproc
-
-	pushq %rbp
-	// The CFA is 24 bytes above the register that it will
-	// be associated with for this frame (%rbp). That is 8
-	// bytes greater than a normal frame, to allow the unwinder
-	// to skip the partial frame of the original function.
-	.cfi_def_cfa_offset 24
-
-#if defined(__APPLE__)
-	// The pattern of the return address being saved twice to the same location
-	// tells the OS X linker that it should not attempt to convert the DWARF
-	// unwind information to the compact format.
-	.cfi_offset %rip, -8
-	.cfi_offset %rip, -8
-#endif
-
-	// %rbp is -24 bytes from the CFA
-	.cfi_offset %rbp, -24
-	movq %rsp, %rbp
-	// Calculate the CFA as on offset from %ebp
-	.cfi_def_cfa_register %rbp
-
-        // re-align the stack
-        subq $8, %rsp
-
-        // kill this program
-        call EXHAUSTED
-
-        // the exhaustion function guarantees that it can't return
-
+	jmp MORESTACK
 	.cfi_endproc