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std: Different thread stack allocation for NetBSD

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* NetBSD is stricter than other OSs and doesn't allow mprotect to mark a
  non-accessible region as RW
* Fix mprotect call over the whole stack, oops
This commit is contained in:
LemonBoy 2020-03-23 19:50:29 +01:00
parent cda73c3c18
commit 09a5f172f8
1 changed files with 61 additions and 24 deletions
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85
lib/std/thread.zig
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@ -292,32 +292,69 @@ pub const Thread = struct {
l += tls_img.alloc_size;
}
}
break :blk l;
// Round the size to the page size.
break :blk mem.alignForward(l, mem.page_size);
};
// Map the whole stack with no rw permissions to avoid committing the
// whole region right away
const mmap_slice = os.mmap(
null,
mem.alignForward(mmap_len, mem.page_size),
os.PROT_NONE,
os.MAP_PRIVATE | os.MAP_ANONYMOUS,
-1,
0,
) catch |err| switch (err) {
error.MemoryMappingNotSupported => unreachable,
error.AccessDenied => unreachable,
error.PermissionDenied => unreachable,
else => |e| return e,
};
errdefer os.munmap(mmap_slice);
// Map everything but the guard page as rw
os.mprotect(
mmap_slice,
os.PROT_READ | os.PROT_WRITE,
) catch |err| switch (err) {
error.AccessDenied => unreachable,
else => |e| return e,
const mmap_slice = mem: {
if (std.Target.current.os.tag != .netbsd) {
// Map the whole stack with no rw permissions to avoid
// committing the whole region right away
const mmap_slice = os.mmap(
null,
mmap_len,
os.PROT_NONE,
os.MAP_PRIVATE | os.MAP_ANONYMOUS,
-1,
0,
) catch |err| switch (err) {
error.MemoryMappingNotSupported => unreachable,
error.AccessDenied => unreachable,
error.PermissionDenied => unreachable,
else => |e| return e,
};
errdefer os.munmap(mmap_slice);
// Map everything but the guard page as rw
os.mprotect(
mmap_slice[guard_end_offset..],
os.PROT_READ | os.PROT_WRITE,
) catch |err| switch (err) {
error.AccessDenied => unreachable,
else => |e| return e,
};
break :mem mmap_slice;
} else {
// NetBSD mprotect is very strict and doesn't allow to "upgrade"
// a PROT_NONE mapping to a RW one so let's allocate everything
// right away
const mmap_slice = os.mmap(
null,
mmap_len,
os.PROT_READ | os.PROT_WRITE,
os.MAP_PRIVATE | os.MAP_ANONYMOUS,
-1,
0,
) catch |err| switch (err) {
error.MemoryMappingNotSupported => unreachable,
error.AccessDenied => unreachable,
error.PermissionDenied => unreachable,
else => |e| return e,
};
errdefer os.munmap(mmap_slice);
// Remap the guard page with no permissions
os.mprotect(
mmap_slice[0..guard_end_offset],
os.PROT_NONE,
) catch |err| switch (err) {
error.AccessDenied => unreachable,
else => |e| return e,
};
break :mem mmap_slice;
}
};
const mmap_addr = @ptrToInt(mmap_slice.ptr);