1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
|
/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2022, the SerenityOS developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <Kernel/API/Syscall.h>
#include <Kernel/Arch/TrapFrame.h>
#include <Kernel/Memory/MemoryManager.h>
#include <Kernel/Panic.h>
#include <Kernel/PerformanceManager.h>
#include <Kernel/Process.h>
#include <Kernel/Scheduler.h>
#include <Kernel/Sections.h>
#include <Kernel/ThreadTracer.h>
#if ARCH(X86_64)
# include <Kernel/Arch/x86_64/Interrupts.h>
#endif
namespace Kernel {
extern "C" void syscall_handler(TrapFrame*) __attribute__((used));
extern "C" void syscall_asm_entry();
NEVER_INLINE NAKED void syscall_asm_entry()
{
// clang-format off
#if ARCH(X86_64)
asm(
" pushq $0x0\n"
" pushq %r15\n"
" pushq %r14\n"
" pushq %r13\n"
" pushq %r12\n"
" pushq %r11\n"
" pushq %r10\n"
" pushq %r9\n"
" pushq %r8\n"
" pushq %rax\n"
" pushq %rcx\n"
" pushq %rdx\n"
" pushq %rbx\n"
" pushq %rsp\n"
" pushq %rbp\n"
" pushq %rsi\n"
" pushq %rdi\n"
" pushq %rsp \n" /* set TrapFrame::regs */
" subq $" __STRINGIFY(TRAP_FRAME_SIZE - 8) ", %rsp \n"
" movq %rsp, %rdi \n"
" cld\n"
" call enter_trap_no_irq \n"
" movq %rsp, %rdi \n"
" call syscall_handler\n"
" jmp common_trap_exit \n");
#endif
// clang-format on
}
namespace Syscall {
static ErrorOr<FlatPtr> handle(RegisterState&, FlatPtr function, FlatPtr arg1, FlatPtr arg2, FlatPtr arg3, FlatPtr arg4);
UNMAP_AFTER_INIT void initialize()
{
#if ARCH(X86_64)
register_user_callable_interrupt_handler(syscall_vector, syscall_asm_entry);
#endif
}
using Handler = auto(Process::*)(FlatPtr, FlatPtr, FlatPtr, FlatPtr) -> ErrorOr<FlatPtr>;
using HandlerWithRegisterState = auto(Process::*)(RegisterState&) -> ErrorOr<FlatPtr>;
struct HandlerMetadata {
Handler handler;
NeedsBigProcessLock needs_lock;
};
#define __ENUMERATE_SYSCALL(sys_call, needs_lock) { bit_cast<Handler>(&Process::sys$##sys_call), needs_lock },
static const HandlerMetadata s_syscall_table[] = {
ENUMERATE_SYSCALLS(__ENUMERATE_SYSCALL)
};
#undef __ENUMERATE_SYSCALL
ErrorOr<FlatPtr> handle(RegisterState& regs, FlatPtr function, FlatPtr arg1, FlatPtr arg2, FlatPtr arg3, FlatPtr arg4)
{
VERIFY_INTERRUPTS_ENABLED();
auto* current_thread = Thread::current();
auto& process = current_thread->process();
current_thread->did_syscall();
PerformanceManager::add_syscall_event(*current_thread, regs);
if (function >= Function::__Count) {
dbgln("Unknown syscall {} requested ({:p}, {:p}, {:p}, {:p})", function, arg1, arg2, arg3, arg4);
return ENOSYS;
}
auto const syscall_metadata = s_syscall_table[function];
if (syscall_metadata.handler == nullptr) {
dbgln("Null syscall {} requested, you probably need to rebuild this program!", function);
return ENOSYS;
}
MutexLocker mutex_locker;
auto const needs_big_lock = syscall_metadata.needs_lock == NeedsBigProcessLock::Yes;
if (needs_big_lock) {
mutex_locker.attach_and_lock(process.big_lock());
};
if (function == SC_exit || function == SC_exit_thread) {
// These syscalls need special handling since they never return to the caller.
// In these cases the process big lock will get released on the exit of the thread.
if (auto* tracer = process.tracer(); tracer && tracer->is_tracing_syscalls()) {
regs.set_return_reg(0);
tracer->set_trace_syscalls(false);
process.tracer_trap(*current_thread, regs); // this triggers SIGTRAP and stops the thread!
}
switch (function) {
case SC_exit:
process.sys$exit(arg1);
case SC_exit_thread:
process.sys$exit_thread(arg1, arg2, arg3);
default:
VERIFY_NOT_REACHED();
}
}
ErrorOr<FlatPtr> result { FlatPtr(nullptr) };
if (function == SC_fork || function == SC_sigreturn) {
// These syscalls want the RegisterState& rather than individual parameters.
auto handler = bit_cast<HandlerWithRegisterState>(syscall_metadata.handler);
result = (process.*(handler))(regs);
} else {
result = (process.*(syscall_metadata.handler))(arg1, arg2, arg3, arg4);
}
return result;
}
}
NEVER_INLINE void syscall_handler(TrapFrame* trap)
{
#if ARCH(X86_64)
// Make sure SMAP protection is enabled on syscall entry.
clac();
#elif ARCH(AARCH64)
// FIXME: Implement the security mechanism for aarch64
#else
# error Unknown architecture
#endif
auto& regs = *trap->regs;
auto* current_thread = Thread::current();
VERIFY(current_thread->previous_mode() == ExecutionMode::User);
auto& process = current_thread->process();
if (process.is_dying()) {
// It's possible this thread is just about to make a syscall while another is
// is killing our process.
current_thread->die_if_needed();
return;
}
if (auto* tracer = process.tracer(); tracer && tracer->is_tracing_syscalls()) {
tracer->set_trace_syscalls(false);
process.tracer_trap(*current_thread, regs); // this triggers SIGTRAP and stops the thread!
}
current_thread->yield_if_stopped();
#if ARCH(X86_64)
// Apply a random offset in the range 0-255 to the stack pointer,
// to make kernel stacks a bit less deterministic.
u32 lsw;
u32 msw;
read_tsc(lsw, msw);
auto* ptr = (char*)__builtin_alloca(lsw & 0xff);
asm volatile(""
: "=m"(*ptr));
constexpr FlatPtr iopl_mask = 3u << 12;
FlatPtr flags = regs.flags();
if ((flags & (iopl_mask)) != 0) {
PANIC("Syscall from process with IOPL != 0");
}
#elif ARCH(AARCH64)
// FIXME: Implement the security mechanism for aarch64
#else
# error Unknown architecture
#endif
Memory::MemoryManager::validate_syscall_preconditions(process, regs);
FlatPtr function;
FlatPtr arg1;
FlatPtr arg2;
FlatPtr arg3;
FlatPtr arg4;
regs.capture_syscall_params(function, arg1, arg2, arg3, arg4);
auto result = Syscall::handle(regs, function, arg1, arg2, arg3, arg4);
if (result.is_error()) {
regs.set_return_reg(-result.error().code());
} else {
regs.set_return_reg(result.value());
}
if (auto* tracer = process.tracer(); tracer && tracer->is_tracing_syscalls()) {
tracer->set_trace_syscalls(false);
process.tracer_trap(*current_thread, regs); // this triggers SIGTRAP and stops the thread!
}
current_thread->yield_if_stopped();
current_thread->check_dispatch_pending_signal();
// If the previous mode somehow changed something is seriously messed up...
VERIFY(current_thread->previous_mode() == ExecutionMode::User);
// Check if we're supposed to return to userspace or just die.
current_thread->die_if_needed();
// Crash any processes which have committed a promise violation during syscall handling.
if (result.is_error() && result.error().code() == EPROMISEVIOLATION) {
VERIFY(current_thread->is_promise_violation_pending());
current_thread->set_promise_violation_pending(false);
process.crash(SIGABRT, 0);
} else {
VERIFY(!current_thread->is_promise_violation_pending());
}
VERIFY(!g_scheduler_lock.is_locked_by_current_processor());
}
}
|
