Add x86-64-v3 CPU pre-flight check to soup

Upstream Elastic now ships binaries built for the x86-64-v3
micro-architecture level. This is not a Security Onion choice: nodes whose
CPUs predate x86-64-v3 can no longer run Elastic's own builds, so those
nodes break once they are upgraded.

Check for support before soup modifies anything, and require the operator
to type "override" to proceed when a node is unsupported or offline.

Runs after upgrade_check so a grid that is already current exits without
prompting. Targets only the roles that run a container built from the
so-elastic-agent image, using the role lists already maintained in
salt/reactor/pillar_push_map.yaml. Adds --skip-cpu-check to bypass the gate
for automation, and exit code 162 when the operator declines to override.

salt/manager/tools/sbin/soup

@@ -120,6 +120,9 @@ check_err() {
       161)
         echo 'Required intermediate Elasticsearch upgrade not complete'
       ;;
+      162)
+        echo 'One or more Elastic Agent nodes do not support the x86-64-v3 CPU instruction set'
+      ;;
       170)
         echo "Intermediate upgrade completed successfully to $next_step_so_version, but next soup to Security Onion $originally_requested_so_version could not be started automatically."
         echo "Start soup again manually to continue the upgrade to Security Onion $originally_requested_so_version."
@@ -347,6 +350,83 @@ check_cluster_health() {
   exit 0
 }
 
+no_soup_for_you() {
+  echo ""
+  echo "No soup for you!"
+  exit 162
+}
+
+check_cpu_compatibility() {
+  # Roles running a container built from the so-elastic-agent image; mirrors the
+  # elasticagent and elasticfleet entries in salt/reactor/pillar_push_map.yaml.
+  local cpu_target='G@role:so-heavynode or G@role:so-eval or G@role:so-fleet or G@role:so-import or G@role:so-manager or G@role:so-managerhype or G@role:so-managersearch or G@role:so-standalone'
+  local expected_nodes cpu_results node result confirm
+  local -a unsupported=() offline=()
+
+  echo "Checking that Elastic Agent nodes support the x86-64-v3 CPU instruction set now required by Elastic."
+
+  if [[ "$SKIP_CPU_CHECK" == "true" ]]; then
+    printf "\nSkipping the x86-64-v3 CPU check because --skip-cpu-check was specified.\n\n"
+    return
+  fi
+
+  # Nodes that never answer are absent from the results, so diff against who should have.
+  expected_nodes=$(salt -C "$cpu_target" --preview-target --out=json 2>/dev/null | jq -r '.[]?') || true
+  if [[ -z "$expected_nodes" ]]; then
+    printf "\nCould not determine which nodes run the Elastic Agent, so the x86-64-v3 CPU check cannot run.\n"
+    no_soup_for_you
+  fi
+
+  cpu_results=$(salt -t 30 -C "$cpu_target" cmd.run "/lib64/ld-linux-x86-64.so.2 --help | grep x86-64-v3" --out=json 2>/dev/null) || true
+
+  while IFS= read -r node; do
+    [[ -z "$node" ]] && continue
+    result=$(jq -r --arg node "$node" '.[$node] // empty' <<< "$cpu_results" 2>/dev/null)
+    if [[ -z "$result" || "$result" == *"did not return"* ]]; then
+      offline+=("$node")
+    elif [[ "$result" != *"x86-64-v3 (supported"* ]]; then
+      # glibc appends "(supported, searched)" only when supported; the open paren keeps
+      # this from matching a future "(unsupported".
+      unsupported+=("$node")
+    fi
+  done <<< "$expected_nodes"
+
+  if [[ ${#unsupported[@]} -eq 0 && ${#offline[@]} -eq 0 ]]; then
+    printf "\nAll Elastic Agent nodes support x86-64-v3. We can proceed with SOUP.\n\n"
+    return
+  fi
+
+  echo ""
+  if [[ ${#unsupported[@]} -gt 0 ]]; then
+    echo "The following node(s) do NOT support the x86-64-v3 CPU instruction set:"
+    printf '  %s\n' "${unsupported[@]}"
+    echo ""
+    echo "Upstream Elastic now builds its binaries for x86-64-v3, so these nodes can no"
+    echo "longer run Elastic. Upgrading them WILL BREAK them."
+    echo ""
+  fi
+  if [[ ${#offline[@]} -gt 0 ]]; then
+    echo "The following node(s) did not respond and could not be checked:"
+    printf '  %s\n' "${offline[@]}"
+    echo ""
+    echo "These nodes are offline, so we cannot confirm they support x86-64-v3, which"
+    echo "upstream Elastic now requires."
+    echo ""
+  fi
+
+  if [[ -n $UNATTENDED ]]; then
+    echo "Unattended mode cannot prompt for an override. Re-run soup interactively, or pass --skip-cpu-check to bypass this check."
+    no_soup_for_you
+  fi
+
+  read -rp "Type 'override' to continue anyway, or press Enter to exit: " confirm
+  if [[ "${confirm,,}" == "override" ]]; then
+    printf "\nOverride accepted. Continuing at your own risk.\n\n"
+  else
+    no_soup_for_you
+  fi
+}
+
 check_fleet_server() {
   echo "Checking that Elastic Fleet Server is responding."
   # Modeled on the wait_for_so-elastic-fleet state check in elasticfleet/enabled.sls,
@@ -1977,6 +2057,9 @@ main() {
 
   echo "Let's see if we need to update Security Onion."
   upgrade_check
+
+  check_cpu_compatibility
+
   upgrade_space
 
   echo "Verifying Elasticsearch version compatibility across the grid before upgrading."
@@ -2255,6 +2338,17 @@ fi
   echo "### soup has been served at $(date) ###"
 }
 
+SKIP_CPU_CHECK=false
+declare -a SOUP_ARGS=()
+for arg in "$@"; do
+  if [[ "$arg" == "--skip-cpu-check" ]]; then
+    SKIP_CPU_CHECK=true
+  else
+    SOUP_ARGS+=("$arg")
+  fi
+done
+set -- "${SOUP_ARGS[@]}"
+
 while getopts ":b:f:y" opt; do
   case ${opt} in
     b )
@@ -2278,7 +2372,7 @@ while getopts ":b:f:y" opt; do
       ISOLOC="$OPTARG"
     ;;
     \? )
-      echo "Usage: soup [-b] [-y] [-f <iso location>]"
+      echo "Usage: soup [-b] [-y] [-f <iso location>] [--skip-cpu-check]"
       exit 1
     ;;
     : )