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https://github.com/LadybirdBrowser/ladybird.git
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794758df3a
VM regions can now be marked as stack regions, which is then validated on syscall, and on page fault. If a thread is caught with its stack pointer pointing into anything that's *not* a Region with its stack bit set, we'll crash the whole process with SIGSTKFLT. Userspace must now allocate custom stacks by using mmap() with the new MAP_STACK flag. This mechanism was first introduced in OpenBSD, and now we have it too, yay! :^)
114 lines
3.2 KiB
C++
114 lines
3.2 KiB
C++
#include <Kernel/Arch/i386/CPU.h>
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#include <Kernel/Process.h>
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#include <Kernel/ProcessTracer.h>
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#include <Kernel/Syscall.h>
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#include <Kernel/VM/MemoryManager.h>
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extern "C" void syscall_trap_entry(RegisterDump);
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extern "C" void syscall_trap_handler();
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asm(
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".globl syscall_trap_handler \n"
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"syscall_trap_handler:\n"
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" pushl $0x0\n"
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" pusha\n"
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" pushw %ds\n"
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" pushw %es\n"
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" pushw %fs\n"
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" pushw %gs\n"
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" pushw %ss\n"
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" pushw %ss\n"
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" pushw %ss\n"
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" pushw %ss\n"
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" pushw %ss\n"
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" popw %ds\n"
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" popw %es\n"
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" popw %fs\n"
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" popw %gs\n"
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" cld\n"
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" call syscall_trap_entry\n"
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" popw %gs\n"
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" popw %gs\n"
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" popw %fs\n"
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" popw %es\n"
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" popw %ds\n"
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" popa\n"
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" add $0x4, %esp\n"
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" iret\n");
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namespace Syscall {
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static int handle(RegisterDump&, u32 function, u32 arg1, u32 arg2, u32 arg3);
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void initialize()
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{
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register_user_callable_interrupt_handler(0x82, syscall_trap_handler);
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kprintf("Syscall: int 0x82 handler installed\n");
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}
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#pragma GCC diagnostic ignored "-Wcast-function-type"
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typedef int (Process::*Handler)(u32, u32, u32);
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#define __ENUMERATE_SYSCALL(x) reinterpret_cast<Handler>(&Process::sys$##x),
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static Handler s_syscall_table[] = {
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ENUMERATE_SYSCALLS
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};
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#undef __ENUMERATE_SYSCALL
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int handle(RegisterDump& regs, u32 function, u32 arg1, u32 arg2, u32 arg3)
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{
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ASSERT_INTERRUPTS_ENABLED();
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auto& process = current->process();
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process.did_syscall();
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if (function == SC_exit || function == SC_exit_thread) {
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// These syscalls need special handling since they never return to the caller.
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cli();
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if (auto* tracer = process.tracer())
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tracer->did_syscall(function, arg1, arg2, arg3, 0);
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if (function == SC_exit)
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process.sys$exit((int)arg1);
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else
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process.sys$exit_thread((void*)arg1);
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ASSERT_NOT_REACHED();
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return 0;
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}
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if (function == SC_fork)
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return process.sys$fork(regs);
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if (function == SC_sigreturn)
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return process.sys$sigreturn(regs);
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if (function >= Function::__Count) {
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dbg() << process << ": Unknown syscall %u requested (" << arg1 << ", " << arg2 << ", " << arg3 << ")";
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return -ENOSYS;
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}
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return (process.*(s_syscall_table[function]))(arg1, arg2, arg3);
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}
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}
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void syscall_trap_entry(RegisterDump regs)
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{
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auto& process = current->process();
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if (!MM.validate_user_stack(process, VirtualAddress(regs.esp_if_crossRing))) {
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dbgprintf("Invalid stack pointer: %p\n", regs.esp_if_crossRing);
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handle_crash(regs, "Bad stack on syscall entry", SIGSTKFLT);
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ASSERT_NOT_REACHED();
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}
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process.big_lock().lock();
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u32 function = regs.eax;
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u32 arg1 = regs.edx;
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u32 arg2 = regs.ecx;
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u32 arg3 = regs.ebx;
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regs.eax = (u32)Syscall::handle(regs, function, arg1, arg2, arg3);
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if (auto* tracer = process.tracer())
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tracer->did_syscall(function, arg1, arg2, arg3, regs.eax);
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process.big_lock().unlock();
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// Check if we're supposed to return to userspace or just die.
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current->die_if_needed();
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}
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