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#include <Kernel/Arch/i386/CPU.h>
#include <Kernel/Process.h>
#include <Kernel/ProcessTracer.h>
#include <Kernel/Random.h>
#include <Kernel/Syscall.h>
#include <Kernel/VM/MemoryManager.h>
extern "C" void syscall_handler(RegisterDump);
extern "C" void syscall_asm_entry();
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 $0x10, %ax\n"
" mov %ax, %ds\n"
" mov %ax, %es\n"
" cld\n"
" call syscall_handler\n"
" add $0x4, %esp\n"
" popl %gs\n"
" popl %fs\n"
" popl %es\n"
" popl %ds\n"
" popa\n"
" add $0x4, %esp\n"
" iret\n");
namespace Syscall {
static int handle(RegisterDump&, u32 function, u32 arg1, u32 arg2, u32 arg3);
void initialize()
{
register_user_callable_interrupt_handler(0x82, syscall_asm_entry);
kprintf("Syscall: int 0x82 handler installed\n");
}
#pragma GCC diagnostic ignored "-Wcast-function-type"
typedef int (Process::*Handler)(u32, u32, u32);
#define __ENUMERATE_REMOVED_SYSCALL(x) nullptr,
#define __ENUMERATE_SYSCALL(x) reinterpret_cast<Handler>(&Process::sys$##x),
static Handler s_syscall_table[] = {
ENUMERATE_SYSCALLS
};
#undef __ENUMERATE_SYSCALL
#undef __ENUMERATE_REMOVED_SYSCALL
int handle(RegisterDump& regs, u32 function, u32 arg1, u32 arg2, u32 arg3)
{
ASSERT_INTERRUPTS_ENABLED();
auto& process = current->process();
current->did_syscall();
if (function == SC_exit || function == SC_exit_thread) {
// These syscalls need special handling since they never return to the caller.
cli();
if (auto* tracer = process.tracer())
tracer->did_syscall(function, arg1, arg2, arg3, 0);
if (function == SC_exit)
process.sys$exit((int)arg1);
else
process.sys$exit_thread((void*)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) {
dbg() << process << ": Unknown syscall %u requested (" << arg1 << ", " << arg2 << ", " << arg3 << ")";
return -ENOSYS;
}
if (s_syscall_table[function] == nullptr) {
dbg() << process << ": Null syscall " << function << " requested: \"" << to_string((Function)function) << "\", you probably need to rebuild this program.";
return -ENOSYS;
}
return (process.*(s_syscall_table[function]))(arg1, arg2, arg3);
}
}
void syscall_handler(RegisterDump regs)
{
// 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.
auto* ptr = (char*)__builtin_alloca(get_fast_random<u8>());
asm volatile(""
: "=m"(*ptr));
auto& process = current->process();
if (!MM.validate_user_stack(process, VirtualAddress(regs.userspace_esp))) {
dbgprintf("Invalid stack pointer: %p\n", regs.userspace_esp);
handle_crash(regs, "Bad stack on syscall entry", SIGSTKFLT);
ASSERT_NOT_REACHED();
}
auto* calling_region = MM.region_from_vaddr(process, VirtualAddress(regs.eip));
if (!calling_region) {
dbgprintf("Syscall from %p which has no region\n", regs.eip);
handle_crash(regs, "Syscall from unknown region", SIGSEGV);
ASSERT_NOT_REACHED();
}
if (calling_region->is_writable()) {
dbgprintf("Syscall from writable memory at %p\n", regs.eip);
handle_crash(regs, "Syscall from writable memory", SIGSEGV);
ASSERT_NOT_REACHED();
}
process.big_lock().lock();
u32 function = regs.eax;
u32 arg1 = regs.edx;
u32 arg2 = regs.ecx;
u32 arg3 = regs.ebx;
regs.eax = (u32)Syscall::handle(regs, function, arg1, arg2, arg3);
if (auto* tracer = process.tracer())
tracer->did_syscall(function, arg1, arg2, arg3, regs.eax);
process.big_lock().unlock();
// Check if we're supposed to return to userspace or just die.
current->die_if_needed();
}
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