CP-52524: Generate an alert when various host kernel taints are set (xapi-project#6128)

Issue an alert about a broken host kernel if bits 4, 5, 7, 9, or 14 are
set in
`/proc/sys/kernel/tainted`, indicating some kind of error was
encountered and the
future behaviour of the kernel might not be predictable or safe anymore
(though
it generally should reasonably recover).

Only one alert per tainted bit per boot should be issued.

Distinguish between Major (4,5,7 - these are all things that might cause
a
host crash, but are unlikely to corrupt whatever data has been written
out) and
Warning (9, 14 - might be a concern and could be raised to Support but
usually
are not severe enough to crash the host) levels of errors as
suggested by the Foundations team.

This should serve as an indicator during issue investigation to look for
the
cause of the taint.

Author: last-genius

ocaml/xapi-consts/api_messages.ml

@@ -360,6 +360,12 @@ let host_internal_certificate_expiring_07 =
 
 let failed_login_attempts = addMessage "FAILED_LOGIN_ATTEMPTS" 3L
 
+let kernel_is_broken which =
+  addMessage ("HOST_KERNEL_ENCOUNTERED_ERROR_" ^ which) 2L
+
+let kernel_is_broken_warning which =
+  addMessage ("HOST_KERNEL_ENCOUNTERED_WARNING_" ^ which) 3L
+
 let tls_verification_emergency_disabled =
   addMessage "TLS_VERIFICATION_EMERGENCY_DISABLED" 3L
 

ocaml/xapi/dbsync_slave.ml

@@ -63,21 +63,24 @@ let create_localhost ~__context info =
     in
     ()
 
-(* TODO cat /proc/stat for btime ? *)
 let get_start_time () =
   try
-    debug "Calculating boot time..." ;
-    let now = Unix.time () in
-    let uptime = Unixext.string_of_file "/proc/uptime" in
-    let uptime = String.trim uptime in
-    let uptime = String.split ' ' uptime in
-    let uptime = List.hd uptime in
-    let uptime = float_of_string uptime in
-    let boot_time = Date.of_unix_time (now -. uptime) in
-    debug " system booted at %s" (Date.to_rfc3339 boot_time) ;
-    boot_time
+    match
+      Unixext.string_of_file "/proc/stat"
+      |> String.trim
+      |> String.split '\n'
+      |> List.find (fun s -> String.starts_with ~prefix:"btime" s)
+      |> String.split ' '
+    with
+    | _ :: btime :: _ ->
+        let boot_time = Date.of_unix_time (float_of_string btime) in
+        debug "%s: system booted at %s" __FUNCTION__ (Date.to_rfc3339 boot_time) ;
+        boot_time
+    | _ ->
+        failwith "Couldn't parse /proc/stat"
   with e ->
-    debug "Calculating boot time failed with '%s'" (ExnHelper.string_of_exn e) ;
+    debug "%s: Calculating boot time failed with '%s'" __FUNCTION__
+      (ExnHelper.string_of_exn e) ;
     Date.epoch
 
 (* not sufficient just to fill in this data on create time [Xen caps may change if VT enabled in BIOS etc.] *)

ocaml/xapi/xapi_host.ml

@@ -2923,6 +2923,81 @@ let emergency_reenable_tls_verification ~__context =
   Helpers.touch_file Constants.verify_certificates_path ;
   Db.Host.set_tls_verification_enabled ~__context ~self ~value:true
 
+(** Issue an alert if /proc/sys/kernel/tainted indicates particular kernel
+    errors. Will send only one alert per reboot *)
+let alert_if_kernel_broken =
+  let __context = Context.make "host_kernel_error_alert_startup_check" in
+  (* Only add an alert if
+     (a) an alert wasn't already issued for the currently booted kernel *)
+  let possible_alerts =
+    ref
+      ( lazy
+        ((* Check all the alerts since last reboot. Only done once at toolstack
+            startup, we track if alerts have been issued afterwards internally *)
+         let self = Helpers.get_localhost ~__context in
+         let boot_time =
+           Db.Host.get_other_config ~__context ~self
+           |> List.assoc "boot_time"
+           |> float_of_string
+         in
+         let all_alerts =
+           [
+             (* processor reported a Machine Check Exception (MCE) *)
+             (4, Api_messages.kernel_is_broken "MCE")
+           ; (* bad page referenced or some unexpected page flags *)
+             (5, Api_messages.kernel_is_broken "BAD_PAGE")
+           ; (* kernel died recently, i.e. there was an OOPS or BUG *)
+             (7, Api_messages.kernel_is_broken "BUG")
+           ; (* kernel issued warning *)
+             (9, Api_messages.kernel_is_broken_warning "WARN")
+           ; (* soft lockup occurred *)
+             (14, Api_messages.kernel_is_broken_warning "SOFT_LOCKUP")
+           ]
+         in
+         all_alerts
+         |> List.filter (fun (_, alert_message) ->
+                let alert_already_issued_for_this_boot =
+                  Helpers.call_api_functions ~__context (fun rpc session_id ->
+                      Client.Client.Message.get_all_records ~rpc ~session_id
+                      |> List.exists (fun (_, record) ->
+                             record.API.message_name = fst alert_message
+                             && API.Date.is_later
+                                  ~than:(API.Date.of_unix_time boot_time)
+                                  record.API.message_timestamp
+                         )
+                  )
+                in
+                alert_already_issued_for_this_boot
+            )
+        )
+        )
+  in
+  (* and (b) if we found a problem *)
+  fun ~__context ->
+    let self = Helpers.get_localhost ~__context in
+    possible_alerts :=
+      Lazy.from_val
+        (Lazy.force !possible_alerts
+        |> List.filter (fun (alert_bit, alert_message) ->
+               let is_bit_tainted =
+                 Unixext.string_of_file "/proc/sys/kernel/tainted"
+                 |> int_of_string
+               in
+               let is_bit_tainted = (is_bit_tainted lsr alert_bit) land 1 = 1 in
+               if is_bit_tainted then (
+                 let host = Db.Host.get_name_label ~__context ~self in
+                 let body =
+                   Printf.sprintf "<body><host>%s</host></body>" host
+                 in
+                 Xapi_alert.add ~msg:alert_message ~cls:`Host
+                   ~obj_uuid:(Db.Host.get_uuid ~__context ~self)
+                   ~body ;
+                 false (* alert issued, remove from the list *)
+               ) else
+                 true (* keep in the list, alert can be issued later *)
+           )
+        )
+
 let alert_if_tls_verification_was_emergency_disabled ~__context =
   let tls_verification_enabled_locally =
     Stunnel_client.get_verify_by_default ()

ocaml/xapi/xapi_host.mli

@@ -540,6 +540,8 @@ val set_numa_affinity_policy :
 
 val emergency_disable_tls_verification : __context:Context.t -> unit
 
+val alert_if_kernel_broken : __context:Context.t -> unit
+
 val alert_if_tls_verification_was_emergency_disabled :
   __context:Context.t -> unit
 

ocaml/xapi/xapi_periodic_scheduler_init.ml

@@ -106,6 +106,13 @@ let register ~__context =
         (Xapi_periodic_scheduler.Periodic freq) freq
         Xapi_pool.alert_failed_login_attempts
   ) ;
+  Xapi_periodic_scheduler.add_to_queue "broken_kernel"
+    (Xapi_periodic_scheduler.Periodic 600.) 600. (fun () ->
+      Server_helpers.exec_with_new_task
+        "Periodic alert if the running kernel is broken in some serious way."
+        (fun __context -> Xapi_host.alert_if_kernel_broken ~__context
+      )
+  ) ;
   Xapi_periodic_scheduler.add_to_queue
     "Period alert if TLS verification emergency disabled"
     (Xapi_periodic_scheduler.Periodic 600.) 600. (fun () ->

ocaml/xenopsd/xc/domain.ml

@@ -835,12 +835,12 @@ let create_channels ~xc uuid domid =
 let numa_hierarchy =
   let open Xenctrlext in
   let open Topology in
-  Lazy.from_fun (fun () ->
-      let xcext = get_handle () in
-      let distances = (numainfo xcext).distances in
-      let cpu_to_node = cputopoinfo xcext |> Array.map (fun t -> t.node) in
-      NUMA.make ~distances ~cpu_to_node
-  )
+  lazy
+    (let xcext = get_handle () in
+     let distances = (numainfo xcext).distances in
+     let cpu_to_node = cputopoinfo xcext |> Array.map (fun t -> t.node) in
+     NUMA.make ~distances ~cpu_to_node
+    )
 
 let numa_mutex = Mutex.create ()
 

quality-gate.sh

@@ -3,7 +3,7 @@
 set -e
 
 list-hd () {
-  N=294
+  N=293
   LIST_HD=$(git grep -r --count 'List.hd' -- **/*.ml | cut -d ':' -f 2 | paste -sd+ - | bc)
   if [ "$LIST_HD" -eq "$N" ]; then
     echo "OK counted $LIST_HD List.hd usages"