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// SPDX-License-Identifier: MIT
// Copyright (c) 2015-2021 Zig Contributors
// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
// The MIT license requires this copyright notice to be included in all copies
// and substantial portions of the software.
const builtin = @import("builtin");
// Zig's own stack-probe routine (available only on x86 and x86_64)
pub fn zig_probe_stack() callconv(.Naked) void {
@setRuntimeSafety(false);
// Versions of the Linux kernel before 5.1 treat any access below SP as
// invalid so let's update it on the go, otherwise we'll get a segfault
// instead of triggering the stack growth.
switch (builtin.arch) {
.x86_64 => {
// %rax = probe length, %rsp = stack pointer
asm volatile (
\\ push %%rcx
\\ mov %%rax, %%rcx
\\ cmp $0x1000,%%rcx
\\ jb 2f
\\ 1:
\\ sub $0x1000,%%rsp
\\ orl $0,16(%%rsp)
\\ sub $0x1000,%%rcx
\\ cmp $0x1000,%%rcx
\\ ja 1b
\\ 2:
\\ sub %%rcx, %%rsp
\\ orl $0,16(%%rsp)
\\ add %%rax,%%rsp
\\ pop %%rcx
\\ ret
);
},
.i386 => {
// %eax = probe length, %esp = stack pointer
asm volatile (
\\ push %%ecx
\\ mov %%eax, %%ecx
\\ cmp $0x1000,%%ecx
\\ jb 2f
\\ 1:
\\ sub $0x1000,%%esp
\\ orl $0,8(%%esp)
\\ sub $0x1000,%%ecx
\\ cmp $0x1000,%%ecx
\\ ja 1b
\\ 2:
\\ sub %%ecx, %%esp
\\ orl $0,8(%%esp)
\\ add %%eax,%%esp
\\ pop %%ecx
\\ ret
);
},
else => {},
}
unreachable;
}
fn win_probe_stack_only() void {
@setRuntimeSafety(false);
switch (builtin.arch) {
.x86_64 => {
asm volatile (
\\ push %%rcx
\\ push %%rax
\\ cmp $0x1000,%%rax
\\ lea 24(%%rsp),%%rcx
\\ jb 1f
\\ 2:
\\ sub $0x1000,%%rcx
\\ test %%rcx,(%%rcx)
\\ sub $0x1000,%%rax
\\ cmp $0x1000,%%rax
\\ ja 2b
\\ 1:
\\ sub %%rax,%%rcx
\\ test %%rcx,(%%rcx)
\\ pop %%rax
\\ pop %%rcx
\\ ret
);
},
.i386 => {
asm volatile (
\\ push %%ecx
\\ push %%eax
\\ cmp $0x1000,%%eax
\\ lea 12(%%esp),%%ecx
\\ jb 1f
\\ 2:
\\ sub $0x1000,%%ecx
\\ test %%ecx,(%%ecx)
\\ sub $0x1000,%%eax
\\ cmp $0x1000,%%eax
\\ ja 2b
\\ 1:
\\ sub %%eax,%%ecx
\\ test %%ecx,(%%ecx)
\\ pop %%eax
\\ pop %%ecx
\\ ret
);
},
else => {},
}
unreachable;
}
fn win_probe_stack_adjust_sp() void {
@setRuntimeSafety(false);
switch (builtin.arch) {
.x86_64 => {
asm volatile (
\\ push %%rcx
\\ cmp $0x1000,%%rax
\\ lea 16(%%rsp),%%rcx
\\ jb 1f
\\ 2:
\\ sub $0x1000,%%rcx
\\ test %%rcx,(%%rcx)
\\ sub $0x1000,%%rax
\\ cmp $0x1000,%%rax
\\ ja 2b
\\ 1:
\\ sub %%rax,%%rcx
\\ test %%rcx,(%%rcx)
\\
\\ lea 8(%%rsp),%%rax
\\ mov %%rcx,%%rsp
\\ mov -8(%%rax),%%rcx
\\ push (%%rax)
\\ sub %%rsp,%%rax
\\ ret
);
},
.i386 => {
asm volatile (
\\ push %%ecx
\\ cmp $0x1000,%%eax
\\ lea 8(%%esp),%%ecx
\\ jb 1f
\\ 2:
\\ sub $0x1000,%%ecx
\\ test %%ecx,(%%ecx)
\\ sub $0x1000,%%eax
\\ cmp $0x1000,%%eax
\\ ja 2b
\\ 1:
\\ sub %%eax,%%ecx
\\ test %%ecx,(%%ecx)
\\
\\ lea 4(%%esp),%%eax
\\ mov %%ecx,%%esp
\\ mov -4(%%eax),%%ecx
\\ push (%%eax)
\\ sub %%esp,%%eax
\\ ret
);
},
else => {},
}
unreachable;
}
// Windows has a multitude of stack-probing functions with similar names and
// slightly different behaviours: some behave as alloca() and update the stack
// pointer after probing the stack, other do not.
//
// Function name | Adjusts the SP? |
// | x86 | x86_64 |
// ----------------------------------------
// _chkstk (_alloca) | yes | yes |
// __chkstk | yes | no |
// __chkstk_ms | no | no |
// ___chkstk (__alloca) | yes | yes |
// ___chkstk_ms | no | no |
pub fn _chkstk() callconv(.Naked) void {
@setRuntimeSafety(false);
@call(.{ .modifier = .always_inline }, win_probe_stack_adjust_sp, .{});
}
pub fn __chkstk() callconv(.Naked) void {
@setRuntimeSafety(false);
switch (builtin.arch) {
.i386 => @call(.{ .modifier = .always_inline }, win_probe_stack_adjust_sp, .{}),
.x86_64 => @call(.{ .modifier = .always_inline }, win_probe_stack_only, .{}),
else => unreachable,
}
}
pub fn ___chkstk() callconv(.Naked) void {
@setRuntimeSafety(false);
@call(.{ .modifier = .always_inline }, win_probe_stack_adjust_sp, .{});
}
pub fn __chkstk_ms() callconv(.Naked) void {
@setRuntimeSafety(false);
@call(.{ .modifier = .always_inline }, win_probe_stack_only, .{});
}
pub fn ___chkstk_ms() callconv(.Naked) void {
@setRuntimeSafety(false);
@call(.{ .modifier = .always_inline }, win_probe_stack_only, .{});
}
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