1 // Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
13 use std::mem::transmute;
16 #[cfg(target_arch = "x86_64")]
20 // FIXME #7761: Registers is boxed so that it is 16-byte aligned, for storing
21 // SSE regs. It would be marginally better not to do this. In C++ we
22 // use an attribute on a struct.
23 // FIXME #7761: It would be nice to define regs as `Box<Option<Registers>>`
24 // since the registers are sometimes empty, but the discriminant would
25 // then misalign the regs again.
27 /// Hold the registers while the task or scheduler is suspended
29 /// Lower bound and upper bound for the stack
30 stack_bounds: Option<(uint, uint)>,
33 pub type InitFn = extern "C" fn(uint, *mut (), *mut ()) -> !;
36 pub fn empty() -> Context {
43 /// Create a new context that will resume execution by running proc()
45 /// The `init` function will be run with `arg` and the `start` procedure
46 /// split up into code and env pointers. It is required that the `init`
47 /// function never return.
49 /// FIXME: this is basically an awful the interface. The main reason for
50 /// this is to reduce the number of allocations made when a green
51 /// task is spawned as much as possible
52 pub fn new(init: InitFn, arg: uint, start: proc():Send,
53 stack: &mut Stack) -> Context {
55 let sp: *const uint = stack.end();
56 let sp: *mut uint = sp as *mut uint;
57 // Save and then immediately load the current context,
58 // which we will then modify to call the given function when restored
59 let mut regs = new_regs();
61 initialize_call_frame(&mut *regs,
64 unsafe { transmute(start) },
67 // Scheduler tasks don't have a stack in the "we allocated it" sense,
68 // but rather they run on pthreads stacks. We have complete control over
69 // them in terms of the code running on them (and hopefully they don't
70 // overflow). Additionally, their coroutine stacks are listed as being
71 // zero-length, so that's how we detect what's what here.
72 let stack_base: *const uint = stack.start();
73 let bounds = if sp as libc::uintptr_t == stack_base as libc::uintptr_t {
76 Some((stack_base as uint, sp as uint))
86 Suspend the current execution context and resume another by
87 saving the registers values of the executing thread to a Context
88 then loading the registers from a previously saved Context.
90 pub fn swap(out_context: &mut Context, in_context: &Context) {
91 rtdebug!("swapping contexts");
92 let out_regs: &mut Registers = match out_context {
93 &Context { regs: box ref mut r, .. } => r
95 let in_regs: &Registers = match in_context {
96 &Context { regs: box ref r, .. } => r
99 rtdebug!("noting the stack limit and doing raw swap");
102 // Right before we switch to the new context, set the new context's
103 // stack limit in the OS-specified TLS slot. This also means that
104 // we cannot call any more rust functions after record_stack_bounds
105 // returns because they would all likely fail due to the limit being
106 // invalid for the current task. Lucky for us `rust_swap_registers`
107 // is a C function so we don't have to worry about that!
108 match in_context.stack_bounds {
109 Some((lo, hi)) => stack::record_rust_managed_stack_bounds(lo, hi),
110 // If we're going back to one of the original contexts or
111 // something that's possibly not a "normal task", then reset
112 // the stack limit to 0 to make morestack never fail
113 None => stack::record_rust_managed_stack_bounds(0, uint::MAX),
115 rust_swap_registers(out_regs, in_regs);
120 #[link(name = "context_switch", kind = "static")]
122 fn rust_swap_registers(out_regs: *mut Registers, in_regs: *const Registers);
125 // Register contexts used in various architectures
127 // These structures all represent a context of one task throughout its
128 // execution. Each struct is a representation of the architecture's register
129 // set. When swapping between tasks, these register sets are used to save off
130 // the current registers into one struct, and load them all from another.
132 // Note that this is only used for context switching, which means that some of
133 // the registers may go unused. For example, for architectures with
134 // callee/caller saved registers, the context will only reflect the callee-saved
135 // registers. This is because the caller saved registers are already stored
136 // elsewhere on the stack (if it was necessary anyway).
138 // Additionally, there may be fields on various architectures which are unused
139 // entirely because they only reflect what is theoretically possible for a
140 // "complete register set" to show, but user-space cannot alter these registers.
141 // An example of this would be the segment selectors for x86.
143 // These structures/functions are roughly in-sync with the source files inside
144 // of src/rt/arch/$arch. The only currently used function from those folders is
145 // the `rust_swap_registers` function, but that's only because for now segmented
146 // stacks are disabled.
148 #[cfg(target_arch = "x86")]
151 eax: u32, ebx: u32, ecx: u32, edx: u32,
152 ebp: u32, esi: u32, edi: u32, esp: u32,
153 cs: u16, ds: u16, ss: u16, es: u16, fs: u16, gs: u16,
154 eflags: u32, eip: u32
157 #[cfg(target_arch = "x86")]
158 fn new_regs() -> Box<Registers> {
160 eax: 0, ebx: 0, ecx: 0, edx: 0,
161 ebp: 0, esi: 0, edi: 0, esp: 0,
162 cs: 0, ds: 0, ss: 0, es: 0, fs: 0, gs: 0,
167 #[cfg(target_arch = "x86")]
168 fn initialize_call_frame(regs: &mut Registers, fptr: InitFn, arg: uint,
169 procedure: raw::Procedure, sp: *mut uint) {
170 let sp = sp as *mut uint;
171 // x86 has interesting stack alignment requirements, so do some alignment
172 // plus some offsetting to figure out what the actual stack should be.
173 let sp = align_down(sp);
174 let sp = mut_offset(sp, -4);
176 unsafe { *mut_offset(sp, 2) = procedure.env as uint };
177 unsafe { *mut_offset(sp, 1) = procedure.code as uint };
178 unsafe { *mut_offset(sp, 0) = arg as uint };
179 let sp = mut_offset(sp, -1);
180 unsafe { *sp = 0 }; // The final return address
182 regs.esp = sp as u32;
183 regs.eip = fptr as u32;
185 // Last base pointer on the stack is 0
189 // windows requires saving more registers (both general and XMM), so the windows
190 // register context must be larger.
191 #[cfg(all(windows, target_arch = "x86_64"))]
194 gpr:[libc::uintptr_t, ..14],
195 _xmm:[simd::u32x4, ..10]
197 #[cfg(all(not(windows), target_arch = "x86_64"))]
200 gpr:[libc::uintptr_t, ..10],
201 _xmm:[simd::u32x4, ..6]
204 #[cfg(all(windows, target_arch = "x86_64"))]
205 fn new_regs() -> Box<Registers> {
208 _xmm:[simd::u32x4(0,0,0,0),..10]
211 #[cfg(all(not(windows), target_arch = "x86_64"))]
212 fn new_regs() -> Box<Registers> {
215 _xmm:[simd::u32x4(0,0,0,0),..6]
219 #[cfg(target_arch = "x86_64")]
220 fn initialize_call_frame(regs: &mut Registers, fptr: InitFn, arg: uint,
221 procedure: raw::Procedure, sp: *mut uint) {
222 extern { fn rust_bootstrap_green_task(); }
224 // Redefinitions from rt/arch/x86_64/regs.h
225 static RUSTRT_RSP: uint = 1;
226 static RUSTRT_IP: uint = 8;
227 static RUSTRT_RBP: uint = 2;
228 static RUSTRT_R12: uint = 4;
229 static RUSTRT_R13: uint = 5;
230 static RUSTRT_R14: uint = 6;
231 static RUSTRT_R15: uint = 7;
233 let sp = align_down(sp);
234 let sp = mut_offset(sp, -1);
236 // The final return address. 0 indicates the bottom of the stack
239 rtdebug!("creating call frame");
240 rtdebug!("fptr {:#x}", fptr as libc::uintptr_t);
241 rtdebug!("arg {:#x}", arg);
242 rtdebug!("sp {}", sp);
244 // These registers are frobbed by rust_bootstrap_green_task into the right
245 // location so we can invoke the "real init function", `fptr`.
246 regs.gpr[RUSTRT_R12] = arg as libc::uintptr_t;
247 regs.gpr[RUSTRT_R13] = procedure.code as libc::uintptr_t;
248 regs.gpr[RUSTRT_R14] = procedure.env as libc::uintptr_t;
249 regs.gpr[RUSTRT_R15] = fptr as libc::uintptr_t;
251 // These registers are picked up by the regular context switch paths. These
252 // will put us in "mostly the right context" except for frobbing all the
253 // arguments to the right place. We have the small trampoline code inside of
254 // rust_bootstrap_green_task to do that.
255 regs.gpr[RUSTRT_RSP] = sp as libc::uintptr_t;
256 regs.gpr[RUSTRT_IP] = rust_bootstrap_green_task as libc::uintptr_t;
258 // Last base pointer on the stack should be 0
259 regs.gpr[RUSTRT_RBP] = 0;
262 #[cfg(target_arch = "arm")]
263 type Registers = [libc::uintptr_t, ..32];
265 #[cfg(target_arch = "arm")]
266 fn new_regs() -> Box<Registers> { box {[0, .. 32]} }
268 #[cfg(target_arch = "arm")]
269 fn initialize_call_frame(regs: &mut Registers, fptr: InitFn, arg: uint,
270 procedure: raw::Procedure, sp: *mut uint) {
271 extern { fn rust_bootstrap_green_task(); }
273 let sp = align_down(sp);
274 // sp of arm eabi is 8-byte aligned
275 let sp = mut_offset(sp, -2);
277 // The final return address. 0 indicates the bottom of the stack
280 // ARM uses the same technique as x86_64 to have a landing pad for the start
281 // of all new green tasks. Neither r1/r2 are saved on a context switch, so
282 // the shim will copy r3/r4 into r1/r2 and then execute the function in r5
283 regs[0] = arg as libc::uintptr_t; // r0
284 regs[3] = procedure.code as libc::uintptr_t; // r3
285 regs[4] = procedure.env as libc::uintptr_t; // r4
286 regs[5] = fptr as libc::uintptr_t; // r5
287 regs[13] = sp as libc::uintptr_t; // #52 sp, r13
288 regs[14] = rust_bootstrap_green_task as libc::uintptr_t; // #56 pc, r14 --> lr
291 #[cfg(any(target_arch = "mips", target_arch = "mipsel"))]
292 type Registers = [libc::uintptr_t, ..32];
294 #[cfg(any(target_arch = "mips", target_arch = "mipsel"))]
295 fn new_regs() -> Box<Registers> { box {[0, .. 32]} }
297 #[cfg(any(target_arch = "mips", target_arch = "mipsel"))]
298 fn initialize_call_frame(regs: &mut Registers, fptr: InitFn, arg: uint,
299 procedure: raw::Procedure, sp: *mut uint) {
300 let sp = align_down(sp);
301 // sp of mips o32 is 8-byte aligned
302 let sp = mut_offset(sp, -2);
304 // The final return address. 0 indicates the bottom of the stack
307 regs[4] = arg as libc::uintptr_t;
308 regs[5] = procedure.code as libc::uintptr_t;
309 regs[6] = procedure.env as libc::uintptr_t;
310 regs[29] = sp as libc::uintptr_t;
311 regs[25] = fptr as libc::uintptr_t;
312 regs[31] = fptr as libc::uintptr_t;
315 fn align_down(sp: *mut uint) -> *mut uint {
316 let sp = (sp as uint) & !(16 - 1);
320 // ptr::mut_offset is positive ints only
322 pub fn mut_offset<T>(ptr: *mut T, count: int) -> *mut T {
323 use std::mem::size_of;
324 (ptr as int + count * (size_of::<T>() as int)) as *mut T