lazy stack: new tracepoint for stack pre-faults

This last patch of the series adds new tracepoint - mmu_vm_stack_fault -
which when enabled allows one to see how particular app triggers
the stack page faults. The tracepoint captures the stack fault address,
the thread id and number of the page (0 being the 1st page).

Please note this does not capture the 1st page of the stack (page_no 0) as this one
pre-faulted by the parent thread that creates a new one.

./scripts/run.py -e /tests/tst-pipe.so --trace=mmu_vm_stack_fault --trace-backtrace -H
./scripts/trace.py extract && ./scripts/trace.py list -bl

0xffff8000016b7040 >init            0         0.002215401 mmu_vm_stack_fault   thread=32, addr=0x00002000000ff9d0, page_no=1
  mmu::vm_fault(unsigned long, exception_frame*)
  page_fault
  ex_pf
  std_malloc(unsigned long, unsigned long)
  malloc
  operator new(unsigned long)
  do_main_thread(void*)
  std::_Function_handler<void (), pthread_private::pthread::pthread(void* (*)(void*), void*, sigset_t, pthread_private::thread_attr const*)::{lambda()#1}>::_M_invoke(std::_Any_data const&) __invoke_impl<void, pthread_private::pthread::pthread(void* (*)(void*), void*, sigset_t, const pthread_private::thread_attr*)::<lambda()>&>__invoke_r<void, pthread_private::pthread::pthread(void* (*)(void*), void*, sigset_t, const pthread_private::thread_attr*)::<lambda()>&> _M_invoke
  sched::thread::main()
  thread_main_c

...

0xffff8000016b7040 >init            0         0.084799151 mmu_vm_stack_fault   thread=32, addr=0x00002000000f8440, page_no=8
  mmu::vm_fault(unsigned long, exception_frame*)
  page_fault
  ex_pf
  memory::page_pool::l1::alloc_page()
  untracked_alloc_page
  memory::alloc_page()
  std_malloc(unsigned long, unsigned long)
  malloc
  operator new(unsigned long)
  lookup
  sys_lstat

Signed-off-by: Waldemar Kozaczuk <[email protected]>

Author: wkozaczuk

core/mmu.cc

@@ -1413,6 +1413,9 @@ bool access_fault(vma& vma, unsigned int error_code)
 TRACEPOINT(trace_mmu_vm_fault, "addr=%p, error_code=%x", uintptr_t, unsigned int);
 TRACEPOINT(trace_mmu_vm_fault_sigsegv, "addr=%p, error_code=%x, %s", uintptr_t, unsigned int, const char*);
 TRACEPOINT(trace_mmu_vm_fault_ret, "addr=%p, error_code=%x", uintptr_t, unsigned int);
+#if CONF_lazy_stack
+TRACEPOINT(trace_mmu_vm_stack_fault, "thread=%d, addr=%p, page_no=%d", unsigned int, uintptr_t, unsigned int);
+#endif
 
 static void vm_sigsegv(uintptr_t addr, exception_frame* ef)
 {
@@ -1438,6 +1441,14 @@ void vm_fault(uintptr_t addr, exception_frame* ef)
         trace_mmu_vm_fault_sigsegv(addr, ef->get_error(), "fast");
         return;
     }
+#if CONF_lazy_stack
+    auto stack = sched::thread::current()->get_stack_info();
+    void *v_addr = reinterpret_cast<void*>(addr);
+    if (v_addr >= stack.begin && v_addr < stack.begin + stack.size) {
+        trace_mmu_vm_stack_fault(sched::thread::current()->id(), addr,
+            ((u64)(stack.begin + stack.size - addr)) / 4096);
+    }
+#endif
     addr = align_down(addr, mmu::page_size);
     WITH_LOCK(vma_list_mutex.for_read()) {
         auto vma = find_intersecting_vma(addr);