Merge branch 'LemonBoy-guard-pages-in-threads'
This commit is contained in:
commit
568dc56232
13
std/os.zig
13
std/os.zig
|
@ -1883,20 +1883,29 @@ pub fn inotify_rm_watch(inotify_fd: i32, wd: i32) void {
|
|||
}
|
||||
|
||||
pub const MProtectError = error{
|
||||
/// The memory cannot be given the specified access. This can happen, for example, if you
|
||||
/// mmap(2) a file to which you have read-only access, then ask mprotect() to mark it
|
||||
/// PROT_WRITE.
|
||||
AccessDenied,
|
||||
|
||||
/// Changing the protection of a memory region would result in the total number of map‐
|
||||
/// pings with distinct attributes (e.g., read versus read/write protection) exceeding the
|
||||
/// allowed maximum. (For example, making the protection of a range PROT_READ in the mid‐
|
||||
/// dle of a region currently protected as PROT_READ|PROT_WRITE would result in three map‐
|
||||
/// pings: two read/write mappings at each end and a read-only mapping in the middle.)
|
||||
OutOfMemory,
|
||||
Unexpected,
|
||||
};
|
||||
|
||||
/// `memory.len` must be page-aligned.
|
||||
pub fn mprotect(memory: [*]align(mem.page_size) u8, protection: u32) MProtectError!void {
|
||||
pub fn mprotect(memory: []align(mem.page_size) u8, protection: u32) MProtectError!void {
|
||||
assert(mem.isAligned(memory.len, mem.page_size));
|
||||
switch (errno(system.mprotect(memory.ptr, memory.len, protection))) {
|
||||
0 => return,
|
||||
EINVAL => unreachable,
|
||||
EACCES => return error.AccessDenied,
|
||||
ENOMEM => return error.OutOfMemory,
|
||||
else => return unexpectedErrno(err),
|
||||
else => |err| return unexpectedErrno(err),
|
||||
}
|
||||
}
|
||||
|
||||
|
|
|
@ -223,15 +223,17 @@ pub const Thread = struct {
|
|||
}
|
||||
};
|
||||
|
||||
const MAP_GROWSDOWN = if (os.linux.is_the_target) os.linux.MAP_GROWSDOWN else 0;
|
||||
|
||||
var guard_end_offset: usize = undefined;
|
||||
var stack_end_offset: usize = undefined;
|
||||
var thread_start_offset: usize = undefined;
|
||||
var context_start_offset: usize = undefined;
|
||||
var tls_start_offset: usize = undefined;
|
||||
const mmap_len = blk: {
|
||||
// First in memory will be the stack, which grows downwards.
|
||||
var l: usize = mem.alignForward(default_stack_size, mem.page_size);
|
||||
var l: usize = mem.page_size;
|
||||
// Allocate a guard page right after the end of the stack region
|
||||
guard_end_offset = l;
|
||||
// The stack itself, which grows downwards.
|
||||
l = mem.alignForward(l + default_stack_size, mem.page_size);
|
||||
stack_end_offset = l;
|
||||
// Above the stack, so that it can be in the same mmap call, put the Thread object.
|
||||
l = mem.alignForward(l, @alignOf(Thread));
|
||||
|
@ -253,20 +255,32 @@ pub const Thread = struct {
|
|||
}
|
||||
break :blk l;
|
||||
};
|
||||
// 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_READ | os.PROT_WRITE,
|
||||
os.MAP_PRIVATE | os.MAP_ANONYMOUS | MAP_GROWSDOWN,
|
||||
os.PROT_NONE,
|
||||
os.MAP_PRIVATE | os.MAP_ANONYMOUS,
|
||||
-1,
|
||||
0,
|
||||
) catch |err| switch (err) {
|
||||
error.MemoryMappingNotSupported => unreachable, // no file descriptor
|
||||
error.AccessDenied => unreachable, // no file descriptor
|
||||
error.PermissionDenied => unreachable, // no file descriptor
|
||||
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_addr = @ptrToInt(mmap_slice.ptr);
|
||||
|
||||
const thread_ptr = @alignCast(@alignOf(Thread), @intToPtr(*Thread, mmap_addr + thread_start_offset));
|
||||
|
|
Loading…
Reference in New Issue
Block a user