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Kernel: Map signal trampoline into each process's address space

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The signal trampoline was previously in kernelspace memory, but with
a special exception to make it user-accessible.

This patch moves it into each process's regular address space so we
can stop supporting user-allowed memory above 0xc0000000.
This commit is contained in:
Andreas Kling 2021-02-14 00:53:53 +01:00
parent 3551198f99
commit 1593219a41
4 changed files with 30 additions and 17 deletions
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24
Kernel/Process.cpp
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@ -58,15 +58,15 @@
namespace Kernel {
static void create_signal_trampolines();
static void create_signal_trampoline();
RecursiveSpinLock g_processes_lock;
static Atomic<pid_t> next_pid;
InlineLinkedList<Process>* g_processes;
String* g_hostname;
Lock* g_hostname_lock;
VirtualAddress g_return_to_ring3_from_signal_trampoline;
HashMap<String, OwnPtr<Module>>* g_modules;
Region* g_signal_trampoline_region;
ProcessID Process::allocate_pid()
{
@ -88,7 +88,7 @@ void Process::initialize()
g_hostname = new String("courage");
g_hostname_lock = new Lock;
create_signal_trampolines();
create_signal_trampoline();
}
Vector<ProcessID> Process::all_pids()
@ -285,25 +285,21 @@ void signal_trampoline_dummy()
extern "C" void asm_signal_trampoline(void);
extern "C" void asm_signal_trampoline_end(void);
void create_signal_trampolines()
void create_signal_trampoline()
{
// NOTE: We leak this region.
auto* trampoline_region = MM.allocate_user_accessible_kernel_region(PAGE_SIZE, "Signal trampolines", Region::Access::Read | Region::Access::Write | Region::Access::Execute, false).leak_ptr();
trampoline_region->set_syscall_region(true);
g_return_to_ring3_from_signal_trampoline = trampoline_region->vaddr();
g_signal_trampoline_region = MM.allocate_kernel_region(PAGE_SIZE, "Signal trampolines", Region::Access::Read | Region::Access::Write, false).leak_ptr();
g_signal_trampoline_region->set_syscall_region(true);
u8* trampoline = (u8*)asm_signal_trampoline;
u8* trampoline_end = (u8*)asm_signal_trampoline_end;
size_t trampoline_size = trampoline_end - trampoline;
{
SmapDisabler disabler;
u8* code_ptr = (u8*)trampoline_region->vaddr().as_ptr();
memcpy(code_ptr, trampoline, trampoline_size);
}
u8* code_ptr = (u8*)g_signal_trampoline_region->vaddr().as_ptr();
memcpy(code_ptr, trampoline, trampoline_size);
trampoline_region->set_writable(false);
trampoline_region->remap();
g_signal_trampoline_region->set_writable(false);
g_signal_trampoline_region->remap();
}
void Process::crash(int signal, u32 eip, bool out_of_memory)