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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <Kernel/API/Syscall.h>
#include <Kernel/Arch/i386/CPU.h>
#include <Kernel/Panic.h>
#include <Kernel/Process.h>
#include <Kernel/Random.h>
#include <Kernel/ThreadTracer.h>
#include <Kernel/VM/MemoryManager.h>
namespace Kernel {
extern "C" void syscall_handler(TrapFrame*);
extern "C" void syscall_asm_entry();
// clang-format off
asm(
".globl syscall_asm_entry\n"
"syscall_asm_entry:\n"
" 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, %fs\n"
" cld\n"
" xor %esi, %esi\n"
" xor %edi, %edi\n"
" pushl %esp \n" // set TrapFrame::regs
" subl $" __STRINGIFY(TRAP_FRAME_SIZE - 4) ", %esp \n"
" movl %esp, %ebx \n"
" pushl %ebx \n" // push pointer to TrapFrame
" call enter_trap_no_irq \n"
" movl %ebx, 0(%esp) \n" // push pointer to TrapFrame
" call syscall_handler \n"
" movl %ebx, 0(%esp) \n" // push pointer to TrapFrame
" jmp common_trap_exit \n");
// clang-format on
namespace Syscall {
static int handle(RegisterState&, u32 function, u32 arg1, u32 arg2, u32 arg3);
void initialize()
{
register_user_callable_interrupt_handler(syscall_vector, syscall_asm_entry);
klog() << "Syscall: int 0x82 handler installed";
}
#pragma GCC diagnostic ignored "-Wcast-function-type"
typedef int (Process::*Handler)(u32, u32, u32);
#define __ENUMERATE_SYSCALL(x) reinterpret_cast<Handler>(&Process::sys$##x),
static Handler s_syscall_table[] = {
ENUMERATE_SYSCALLS(__ENUMERATE_SYSCALL)
};
#undef __ENUMERATE_SYSCALL
int handle(RegisterState& regs, u32 function, u32 arg1, u32 arg2, u32 arg3)
{
ASSERT_INTERRUPTS_ENABLED();
auto current_thread = Thread::current();
auto& process = current_thread->process();
current_thread->did_syscall();
if (function == SC_exit || function == SC_exit_thread) {
// These syscalls need special handling since they never return to the caller.
if (auto* tracer = process.tracer(); tracer && tracer->is_tracing_syscalls()) {
regs.eax = 0;
tracer->set_trace_syscalls(false);
process.tracer_trap(*current_thread, regs); // this triggers SIGTRAP and stops the thread!
}
cli();
if (function == SC_exit)
process.sys$exit((int)arg1);
else
process.sys$exit_thread(arg1);
ASSERT_NOT_REACHED();
return 0;
}
if (function == SC_fork)
return process.sys$fork(regs);
if (function == SC_sigreturn)
return process.sys$sigreturn(regs);
if (function >= Function::__Count) {
dbgln("Unknown syscall {} requested ({:08x}, {:08x}, {:08x})", function, arg1, arg2, arg3);
return -ENOSYS;
}
if (s_syscall_table[function] == nullptr) {
dbgln("Null syscall {} requested, you probably need to rebuild this program!", function);
return -ENOSYS;
}
return (process.*(s_syscall_table[function]))(arg1, arg2, arg3);
}
}
constexpr int RandomByteBufferSize = 256;
u8 g_random_byte_buffer[RandomByteBufferSize];
int g_random_byte_buffer_offset = RandomByteBufferSize;
void syscall_handler(TrapFrame* trap)
{
auto& regs = *trap->regs;
auto current_thread = Thread::current();
ASSERT(current_thread->previous_mode() == Thread::PreviousMode::UserMode);
auto& process = current_thread->process();
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.
// Since this is very hot code, request random data in chunks instead of
// one byte at a time. This is a noticeable speedup.
if (g_random_byte_buffer_offset == RandomByteBufferSize) {
get_fast_random_bytes(g_random_byte_buffer, RandomByteBufferSize);
g_random_byte_buffer_offset = 0;
}
auto* ptr = (char*)__builtin_alloca(g_random_byte_buffer[g_random_byte_buffer_offset++]);
asm volatile(""
: "=m"(*ptr));
static constexpr u32 iopl_mask = 3u << 12;
if ((regs.eflags & (iopl_mask)) != 0) {
PANIC("Syscall from process with IOPL != 0");
}
// NOTE: We take the big process lock before inspecting memory regions.
process.big_lock().lock();
if (!MM.validate_user_stack(process, VirtualAddress(regs.userspace_esp))) {
dbgln("Invalid stack pointer: {:p}", regs.userspace_esp);
handle_crash(regs, "Bad stack on syscall entry", SIGSTKFLT);
}
auto* calling_region = MM.find_region_from_vaddr(process.space(), VirtualAddress(regs.eip));
if (!calling_region) {
dbgln("Syscall from {:p} which has no associated region", regs.eip);
handle_crash(regs, "Syscall from unknown region", SIGSEGV);
}
if (calling_region->is_writable()) {
dbgln("Syscall from writable memory at {:p}", regs.eip);
handle_crash(regs, "Syscall from writable memory", SIGSEGV);
}
if (process.space().enforces_syscall_regions() && !calling_region->is_syscall_region()) {
dbgln("Syscall from non-syscall region");
handle_crash(regs, "Syscall from non-syscall region", SIGSEGV);
}
u32 function = regs.eax;
u32 arg1 = regs.edx;
u32 arg2 = regs.ecx;
u32 arg3 = regs.ebx;
regs.eax = Syscall::handle(regs, function, arg1, arg2, arg3);
process.big_lock().unlock();
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...
ASSERT(current_thread->previous_mode() == Thread::PreviousMode::UserMode);
// Check if we're supposed to return to userspace or just die.
current_thread->die_if_needed();
ASSERT(!g_scheduler_lock.own_lock());
}
}
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