user_memory.h revision c7c3973e
1/*
2 * Copyright 2018, J��r��me Duval, jerome.duval@gmail.com.
3 * Copyright 2014, Pawe�� Dziepak, pdziepak@quarnos.org.
4 * Distributed under the terms of the MIT License.
5 */
6#ifndef _KERNEL_ARCH_GENERIC_USER_MEMORY_H
7#define _KERNEL_ARCH_GENERIC_USER_MEMORY_H
8
9
10#include <atomic>
11
12#include <setjmp.h>
13#include <string.h>
14
15#include <thread.h>
16
17
18namespace {
19
20
21struct FaultHandlerGuard {
22	FaultHandlerGuard()
23	{
24		old_handler = thread_get_current_thread()->fault_handler;
25		if (old_handler != nullptr) {
26			memcpy(old_handler_state,
27				thread_get_current_thread()->fault_handler_state,
28				sizeof(jmp_buf));
29		}
30		thread_get_current_thread()->fault_handler = HandleFault;
31		std::atomic_signal_fence(std::memory_order_acq_rel);
32	}
33
34
35	~FaultHandlerGuard()
36	{
37		std::atomic_signal_fence(std::memory_order_acq_rel);
38		thread_get_current_thread()->fault_handler = old_handler;
39		if (old_handler != nullptr) {
40			memcpy(thread_get_current_thread()->fault_handler_state,
41				old_handler_state,
42				sizeof(jmp_buf));
43		}
44
45	}
46
47
48	[[noreturn]] static void HandleFault()
49	{
50		longjmp(thread_get_current_thread()->fault_handler_state, 1);
51	}
52
53	void 		(*old_handler)(void);
54	jmp_buf		old_handler_state;
55};
56
57
58template<typename Function>
59bool user_access(Function function)
60{
61	FaultHandlerGuard guard;
62	// TODO: try { } catch (...) { } would be much nicer, wouldn't it?
63	// And faster... And world wouldn't end in a terrible disaster if function()
64	// or anything it calls created on stack an object with non-trivial
65	// destructor.
66	auto fail = setjmp(thread_get_current_thread()->fault_handler_state);
67	if (fail == 0) {
68		set_ac();
69		function();
70		clear_ac();
71		return true;
72	}
73	return false;
74}
75
76
77inline status_t
78arch_cpu_user_memcpy(void* src, const void* dst, size_t n)
79{
80	return user_access([=] { memcpy(src, dst, n); }) ? B_OK : B_ERROR;
81}
82
83
84inline status_t
85arch_cpu_user_memset(void* src, char v, size_t n)
86{
87	return user_access([=] { memset(src, v, n); }) ? B_OK : B_ERROR;
88}
89
90
91inline ssize_t
92arch_cpu_user_strlcpy(char* src, const char* dst, size_t n)
93{
94	ssize_t result;
95	return user_access([=, &result] { result = strlcpy(src, dst, n); })
96		? result : B_ERROR;
97}
98
99}
100
101#endif	// _KERNEL_ARCH_GENERIC_USER_MEMORY_H
102
103