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kernel: Add stack diagnostics to userspace fault reporting

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This commit is contained in:
apio 2024-01-04 11:14:19 +01:00
parent f34dd56375
commit 1208d94b37
Signed by: apio
GPG Key ID: B8A7D06E42258954
2 changed files with 24 additions and 8 deletions
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19
kernel/src/arch/x86_64/CPU.cpp
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@ -75,6 +75,16 @@ void decode_page_fault_error_code(u64 code)
(code & PF_RESERVED) ? " | Reserved bits set" : "", (code & PF_NX_VIOLATION) ? " | NX violation" : "");
}
static void check_stack(Thread* current, Registers* regs)
{
if (regs->rsp < current->stack.bottom() || regs->rsp >= current->stack.top())
kerrorln("Abnormal stack (RSP outside the normal range, %.16lx-%.16lx)", current->stack.bottom(),
current->stack.top());
if (regs->rsp >= (current->stack.bottom() - ARCH_PAGE_SIZE) && regs->rsp < current->stack.bottom())
kerrorln("Likely stack overflow (CPU exception inside guard page)");
}
void handle_cpu_exception(int signo, const char* err, Registers* regs)
{
if (err) kerrorln("Caught CPU exception: %s", err);
@ -89,8 +99,11 @@ void handle_cpu_exception(int signo, const char* err, Registers* regs)
if (!is_in_kernel(regs))
{
Scheduler::current()->send_signal(signo);
Scheduler::current()->process_pending_signals(regs);
auto* current = Scheduler::current();
check_stack(current, regs);
current->send_signal(signo);
current->process_pending_signals(regs);
return;
}
@ -103,6 +116,8 @@ void handle_page_fault(Registers* regs)
asm volatile("mov %%cr2, %0" : "=r"(cr2));
kerrorln("Page fault while accessing %lx!", cr2);
if (cr2 <= ARCH_PAGE_SIZE) kerrorln("Looks like a null pointer dereference!");
decode_page_fault_error_code(regs->error);
handle_cpu_exception(SIGSEGV, nullptr, regs);

13
kernel/src/thread/ThreadImage.cpp
View File

@ -11,16 +11,17 @@ static constexpr u64 THREAD_STACK_BASE = 0x10000;
static Result<void> create_user_stack(Stack& user_stack, AddressSpace* space)
{
TRY(MemoryManager::alloc_at_zeroed(THREAD_STACK_BASE, DEFAULT_USER_STACK_PAGES,
MMU::ReadWrite | MMU::NoExecute | MMU::User));
auto guard = make_scope_guard([] { MemoryManager::unmap_owned(THREAD_STACK_BASE, DEFAULT_USER_STACK_PAGES); });
if (!TRY(space->test_and_alloc_region(THREAD_STACK_BASE, DEFAULT_USER_STACK_PAGES, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, 0, true)))
return err(ENOMEM);
guard.deactivate();
// Stack overflow guard page, remains unmapped.
if (!TRY(space->test_and_alloc_region(THREAD_STACK_BASE - ARCH_PAGE_SIZE, 1, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS,
0, 0, true)))
return err(ENOMEM);
TRY(MemoryManager::alloc_at_zeroed(THREAD_STACK_BASE, DEFAULT_USER_STACK_PAGES,
MMU::ReadWrite | MMU::NoExecute | MMU::User));
user_stack = { THREAD_STACK_BASE, DEFAULT_USER_STACK_SIZE };