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https://github.com/RGBCube/serenity
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UserspaceEmulator: Update signal handlers to use the new stack layout
The kernel sets up the stack like this, so set it up the same way.
This commit is contained in:
Ali Mohammad Pur
Andreas Kling
parent
baf7038919
commit
1125cbe336
2 changed files with 122 additions and 48 deletions
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@ -616,31 +616,81 @@ void Emulator::dispatch_one_pending_signal()
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reportln("\n=={}== Got signal {} ({}), handler at {:p}", getpid(), signum, strsignal(signum), handler.handler);
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reportln("\n=={}== Got signal {} ({}), handler at {:p}", getpid(), signum, strsignal(signum), handler.handler);
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auto old_esp = m_cpu->esp();
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auto old_esp = m_cpu->esp().value();
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u32 stack_alignment = (m_cpu->esp().value() - 52) % 16;
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ucontext_t ucontext {
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m_cpu->set_esp(shadow_wrap_as_initialized(m_cpu->esp().value() - stack_alignment));
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.uc_link = nullptr,
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.uc_sigmask = m_signal_mask,
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.uc_stack = {
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.ss_sp = bit_cast<void*>(old_esp),
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.ss_flags = 0,
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.ss_size = 0,
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},
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.uc_mcontext = {
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.eax = m_cpu->eax().value(),
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.ecx = m_cpu->ecx().value(),
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.edx = m_cpu->edx().value(),
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.ebx = m_cpu->ebx().value(),
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.esp = m_cpu->esp().value(),
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.ebp = m_cpu->ebp().value(),
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.esi = m_cpu->esi().value(),
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.edi = m_cpu->edi().value(),
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.eip = m_cpu->eip(),
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.eflags = m_cpu->eflags(),
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.cs = m_cpu->cs(),
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.ss = m_cpu->ss(),
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.ds = m_cpu->ds(),
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.es = m_cpu->es(),
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// ???
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.fs = 0,
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.gs = 0,
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},
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};
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m_cpu->push32(shadow_wrap_as_initialized(m_cpu->eflags()));
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// FIXME: Set these fields.
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m_cpu->push32(shadow_wrap_as_initialized(m_cpu->eip()));
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siginfo_t signal_info {
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m_cpu->push32(m_cpu->eax());
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.si_signo = signum,
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m_cpu->push32(m_cpu->ecx());
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.si_code = 0,
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m_cpu->push32(m_cpu->edx());
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.si_errno = 0,
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m_cpu->push32(m_cpu->ebx());
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.si_pid = 0,
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m_cpu->push32(old_esp);
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.si_uid = 0,
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m_cpu->push32(m_cpu->ebp());
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.si_addr = 0,
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m_cpu->push32(m_cpu->esi());
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.si_status = 0,
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m_cpu->push32(m_cpu->edi());
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.si_band = 0,
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.si_value = {
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.sival_int = 0,
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},
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};
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// FIXME: Push old signal mask here.
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// Align the stack to 16 bytes.
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// Note that we push some elements on to the stack before the return address,
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// so we need to account for this here.
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constexpr static FlatPtr elements_pushed_on_stack_before_handler_address = 1; // one slot for a saved register
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FlatPtr const extra_bytes_pushed_on_stack_before_handler_address = sizeof(ucontext_t) + sizeof(siginfo_t);
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FlatPtr stack_alignment = (old_esp - elements_pushed_on_stack_before_handler_address * sizeof(FlatPtr) + extra_bytes_pushed_on_stack_before_handler_address) % 16;
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// Also note that we have to skip the thread red-zone (if needed), so do that here.
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old_esp -= stack_alignment;
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m_cpu->set_esp(shadow_wrap_with_taint_from(old_esp, m_cpu->esp()));
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m_cpu->push32(shadow_wrap_as_initialized(0u)); // syscall return value slot
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m_cpu->push_buffer(bit_cast<u8 const*>(&ucontext), sizeof(ucontext_t));
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auto pointer_to_ucontext = m_cpu->esp().value();
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m_cpu->push_buffer(bit_cast<u8 const*>(&signal_info), sizeof(siginfo_t));
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auto pointer_to_signal_info = m_cpu->esp().value();
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// FPU state, leave a 512-byte gap. FIXME: Fill this in.
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m_cpu->set_esp({ m_cpu->esp().value() - 512, m_cpu->esp().shadow() });
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// Leave one empty slot to align the stack for a handler call.
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m_cpu->push32(shadow_wrap_as_initialized(0u));
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m_cpu->push32(shadow_wrap_as_initialized(0u));
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m_cpu->push32(shadow_wrap_as_initialized(pointer_to_ucontext));
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m_cpu->push32(shadow_wrap_as_initialized(pointer_to_signal_info));
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m_cpu->push32(shadow_wrap_as_initialized(static_cast<u32>(signum)));
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m_cpu->push32(shadow_wrap_as_initialized((u32)signum));
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m_cpu->push32(shadow_wrap_as_initialized<u32>(handler.handler));
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m_cpu->push32(shadow_wrap_as_initialized(handler.handler));
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VERIFY((m_cpu->esp().value() % 16) == 0);
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m_cpu->push32(shadow_wrap_as_initialized(0u));
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m_cpu->set_eip(m_signal_trampoline);
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m_cpu->set_eip(m_signal_trampoline);
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}
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}
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@ -654,21 +704,34 @@ NEVER_INLINE void signal_trampoline_dummy()
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// blocking syscall, that syscall may return some special error code in eax;
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// blocking syscall, that syscall may return some special error code in eax;
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// This error code would likely be overwritten by the signal handler, so it's
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// This error code would likely be overwritten by the signal handler, so it's
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// necessary to preserve it here.
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// necessary to preserve it here.
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constexpr static auto offset_to_first_register_slot = sizeof(__ucontext) + sizeof(siginfo) + 512 + 4 * sizeof(FlatPtr);
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asm(
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asm(
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".intel_syntax noprefix\n"
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".intel_syntax noprefix\n"
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".globl asm_signal_trampoline\n"
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"asm_signal_trampoline:\n"
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"asm_signal_trampoline:\n"
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"push ebp\n"
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// stack state: 0, ucontext, signal_info, (alignment = 16), fpu_state (alignment = 16), 0, ucontext*, siginfo*, signal, (alignment = 16), handler
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"mov ebp, esp\n"
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"push eax\n" // we have to store eax 'cause it might be the return value from a syscall
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// Pop the handler into ecx
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"sub esp, 4\n" // align the stack to 16 bytes
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"pop ecx\n" // save handler
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"mov eax, [ebp+12]\n" // push the signal code
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// we have to save eax 'cause it might be the return value from a syscall
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"push eax\n"
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"mov [esp+%P2], eax\n"
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"call [ebp+8]\n" // call the signal handler
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// Note that the stack is currently aligned to 16 bytes as we popped the extra entries above.
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"add esp, 8\n"
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// and it's already setup to call the handler with the expected values on the stack.
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// call the signal handler
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"call ecx\n"
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// drop the 4 arguments
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"add esp, 16\n"
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// Current stack state is just saved_eax, ucontext, signal_info, fpu_state?.
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// syscall SC_sigreturn
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"mov eax, %P0\n"
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"mov eax, %P0\n"
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"int 0x82\n" // sigreturn syscall
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"int 0x82\n"
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".globl asm_signal_trampoline_end\n"
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"asm_signal_trampoline_end:\n"
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"asm_signal_trampoline_end:\n"
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".att_syntax" ::"i"(Syscall::SC_sigreturn));
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".att_syntax"
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:
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: "i"(Syscall::SC_sigreturn),
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"i"(offset_to_first_register_slot),
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"i"(offset_to_first_register_slot - sizeof(FlatPtr)));
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}
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}
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extern "C" void asm_signal_trampoline(void);
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extern "C" void asm_signal_trampoline(void);
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@ -1400,32 +1400,43 @@ int Emulator::virt$sigprocmask(int how, FlatPtr set, FlatPtr old_set)
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int Emulator::virt$sigreturn()
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int Emulator::virt$sigreturn()
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{
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{
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u32 stack_ptr = m_cpu->esp().value();
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u32 stack_ptr = m_cpu->esp().value();
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auto local_pop = [&]() -> ValueWithShadow<u32> {
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auto local_pop = [&]<typename T>() {
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auto value = m_cpu->read_memory32({ m_cpu->ss(), stack_ptr });
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auto value = m_cpu->read_memory<T>({ m_cpu->ss(), stack_ptr });
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stack_ptr += sizeof(u32);
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stack_ptr += sizeof(T);
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return value;
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return value;
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};
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};
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auto smuggled_eax = local_pop();
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// State from signal trampoline (note that we're assuming i386 here):
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// saved_ax, ucontext, signal_info, fpu_state.
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stack_ptr += 4 * sizeof(u32);
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// Drop the FPU state
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// FIXME: Read and restore from this.
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stack_ptr += 512;
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m_signal_mask = local_pop().value();
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// Drop the signal info
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stack_ptr += sizeof(siginfo_t);
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m_cpu->set_edi(local_pop());
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auto ucontext = local_pop.operator()<ucontext_t>();
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m_cpu->set_esi(local_pop());
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m_cpu->set_ebp(local_pop());
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m_cpu->set_esp(local_pop());
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m_cpu->set_ebx(local_pop());
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m_cpu->set_edx(local_pop());
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m_cpu->set_ecx(local_pop());
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m_cpu->set_eax(local_pop());
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m_cpu->set_eip(local_pop().value());
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auto eax = local_pop.operator()<u32>();
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m_cpu->set_eflags(local_pop());
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// FIXME: We're losing shadow bits here.
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m_signal_mask = ucontext.value().uc_sigmask;
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return smuggled_eax.value();
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auto mcontext_slice = ucontext.slice<&ucontext_t::uc_mcontext>();
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m_cpu->set_edi(mcontext_slice.slice<&__mcontext::edi>());
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m_cpu->set_esi(mcontext_slice.slice<&__mcontext::esi>());
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m_cpu->set_ebp(mcontext_slice.slice<&__mcontext::ebp>());
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m_cpu->set_esp(mcontext_slice.slice<&__mcontext::esp>());
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m_cpu->set_ebx(mcontext_slice.slice<&__mcontext::ebx>());
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m_cpu->set_edx(mcontext_slice.slice<&__mcontext::edx>());
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m_cpu->set_ecx(mcontext_slice.slice<&__mcontext::ecx>());
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m_cpu->set_eax(mcontext_slice.slice<&__mcontext::eax>());
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m_cpu->set_eip(mcontext_slice.value().eip);
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m_cpu->set_eflags(mcontext_slice.slice<&__mcontext::eflags>());
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// FIXME: We're dropping the shadow bits here.
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return eax.value();
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}
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}
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int Emulator::virt$getpgrp()
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int Emulator::virt$getpgrp()
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