RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-06-30 10:22:13 +00:00
Code Issues Activity Actions

Kernel: Share the "return to ring 0/3 from signal" trampolines globally.

Browse source 
Generate a special page containing the "return from signal" trampoline code
on startup and then route signalled threads to it. This avoids a page
allocation in every process that ever receives a signal.
This commit is contained in:
Andreas Kling 2019-07-19 17:01:16 +02:00
parent fdf931cfce
commit f8beb0f665
5 changed files with 36 additions and 21 deletions
Download patch file Download diff file Expand all files Collapse all files

27
Kernel/Process.cpp
View file

@ -35,10 +35,14 @@
//#define SIGNAL_DEBUG
//#define SHARED_BUFFER_DEBUG
static void create_signal_trampolines();
static pid_t next_pid;
InlineLinkedList<Process>* g_processes;
static String* s_hostname;
static Lock* s_hostname_lock;
VirtualAddress g_return_to_ring3_from_signal_trampoline;
VirtualAddress g_return_to_ring0_from_signal_trampoline;
void Process::initialize()
{
@ -46,6 +50,8 @@ void Process::initialize()
g_processes = new InlineLinkedList<Process>;
s_hostname = new String("courage");
s_hostname_lock = new Lock;
create_signal_trampolines();
}
Vector<pid_t> Process::all_pids()
@ -673,15 +679,15 @@ void Process::sys$exit(int status)
ASSERT_NOT_REACHED();
}
void Process::create_signal_trampolines_if_needed()
void create_signal_trampolines()
{
if (!m_return_to_ring3_from_signal_trampoline.is_null())
return;
// FIXME: This should be a global trampoline shared by all processes, not one created per process!
// FIXME: Remap as read-only after setup.
auto* region = allocate_region(VirtualAddress(), PAGE_SIZE, "Signal trampolines", PROT_READ | PROT_WRITE | PROT_EXEC);
m_return_to_ring3_from_signal_trampoline = region->vaddr();
u8* code_ptr = m_return_to_ring3_from_signal_trampoline.as_ptr();
InterruptDisabler disabler;
// NOTE: We leak this region.
auto* trampoline_region = MM.allocate_user_accessible_kernel_region(PAGE_SIZE, "Signal trampolines").leak_ref();
g_return_to_ring3_from_signal_trampoline = trampoline_region->vaddr();
u8* code_ptr = (u8*)trampoline_region->vaddr().as_ptr();
*code_ptr++ = 0x58; // pop eax (Argument to signal handler (ignored here))
*code_ptr++ = 0x5a; // pop edx (Original signal mask to restore)
*code_ptr++ = 0xb8; // mov eax, <u32>
@ -700,7 +706,7 @@ void Process::create_signal_trampolines_if_needed()
*code_ptr++ = 0x0f; // ud2
*code_ptr++ = 0x0b;
m_return_to_ring0_from_signal_trampoline = VirtualAddress((u32)code_ptr);
g_return_to_ring0_from_signal_trampoline = VirtualAddress((u32)code_ptr);
*code_ptr++ = 0x58; // pop eax (Argument to signal handler (ignored here))
*code_ptr++ = 0x5a; // pop edx (Original signal mask to restore)
*code_ptr++ = 0xb8; // mov eax, <u32>
@ -717,6 +723,9 @@ void Process::create_signal_trampolines_if_needed()
*code_ptr++ = 0x82;
*code_ptr++ = 0x0f; // ud2
*code_ptr++ = 0x0b;
trampoline_region->set_writable(false);
MM.remap_region(*trampoline_region->page_directory(), *trampoline_region);
}
int Process::sys$restore_signal_mask(u32 mask)