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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <Kernel/API/Syscall.h>
#include <Kernel/Arch/x86/Interrupts.h>
#include <Kernel/Arch/x86/TrapFrame.h>
#include <Kernel/Panic.h>
#include <Kernel/Process.h>
#include <Kernel/Sections.h>
#include <Kernel/ThreadTracer.h>
#include <Kernel/VM/MemoryManager.h>
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(I386)
asm(
" pushl $0x0\n"
" pusha\n"
" pushl %ds\n"
" pushl %es\n"
" pushl %fs\n"
" pushl %gs\n"
" pushl %ss\n"
" mov $" __STRINGIFY(GDT_SELECTOR_DATA0) ", %ax\n"
" mov %ax, %ds\n"
" mov %ax, %es\n"
" mov $" __STRINGIFY(GDT_SELECTOR_PROC) ", %ax\n"
" mov %ax, %gs\n"
" cld\n"
" xor %esi, %esi\n"
" xor %edi, %edi\n"
" pushl %esp \n" // set TrapFrame::regs
" subl $" __STRINGIFY(TRAP_FRAME_SIZE - 4) ", %esp \n"
" movl %esp, %ebx \n"
" pushl %ebx \n" // push pointer to TrapFrame
" call enter_trap_no_irq \n"
" movl %ebx, 0(%esp) \n" // push pointer to TrapFrame
" call syscall_handler \n"
" movl %ebx, 0(%esp) \n" // push pointer to TrapFrame
" jmp common_trap_exit \n");
#elif 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 $" __STRINGIFY(TRAP_FRAME_SIZE - 8) ", %rsp \n"
" movq %rsp, %rdi \n"
" cld\n"
" call enter_trap_no_irq \n"
" movq %rsp, %rdi \n"
" call syscall_handler\n"
" jmp common_trap_exit \n");
#endif
// clang-format on
}
namespace Syscall {
static KResultOr<FlatPtr> handle(RegisterState&, FlatPtr function, FlatPtr arg1, FlatPtr arg2, FlatPtr arg3, FlatPtr arg4);
UNMAP_AFTER_INIT void initialize()
{
register_user_callable_interrupt_handler(syscall_vector, syscall_asm_entry);
}
#pragma GCC diagnostic ignored "-Wcast-function-type"
typedef KResultOr<FlatPtr> (Process::*Handler)(FlatPtr, FlatPtr, FlatPtr, FlatPtr);
typedef KResultOr<FlatPtr> (Process::*HandlerWithRegisterState)(RegisterState&);
struct HandlerMetadata {
Handler handler;
NeedsBigProcessLock needs_lock;
};
#define __ENUMERATE_SYSCALL(sys_call, needs_lock) { reinterpret_cast<Handler>(&Process::sys$##sys_call), needs_lock },
static const HandlerMetadata s_syscall_table[] = {
ENUMERATE_SYSCALLS(__ENUMERATE_SYSCALL)
};
#undef __ENUMERATE_SYSCALL
KResultOr<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();
if (function >= Function::__Count) {
dbgln("Unknown syscall {} requested ({:p}, {:p}, {:p}, {:p})", function, arg1, arg2, arg3, arg4);
return ENOSYS;
}
const auto 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;
const auto 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$exit(arg1);
break;
case SC_exit_thread:
process.sys$exit_thread(arg1, arg2, arg3);
break;
default:
VERIFY_NOT_REACHED();
}
}
KResultOr<FlatPtr> result { FlatPtr(nullptr) };
if (function == SC_fork || function == SC_sigreturn) {
// These syscalls want the RegisterState& rather than individual parameters.
auto handler = (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)
{
auto& regs = *trap->regs;
auto current_thread = Thread::current();
VERIFY(current_thread->previous_mode() == Thread::PreviousMode::UserMode);
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();
// Make sure SMAP protection is enabled on syscall entry.
clac();
// 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));
static constexpr FlatPtr iopl_mask = 3u << 12;
FlatPtr flags = regs.flags();
if ((flags & (iopl_mask)) != 0) {
PANIC("Syscall from process with IOPL != 0");
}
MM.validate_syscall_preconditions(process.space(), 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());
} 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() == Thread::PreviousMode::UserMode);
// Check if we're supposed to return to userspace or just die.
current_thread->die_if_needed();
VERIFY(!g_scheduler_lock.own_lock());
}
}
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