tools: add deny_sched_setattr

A tool to test if inside QM it's possible to use the
deny_sched_setattr() syscall to set SCHED_DEADLINE.

Fixes: #376

Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>

tests/e2e/tools/FFI/deny_sched_setattr/README

@@ -0,0 +1,23 @@
+# What is execute_sched_setattr ?
+
+A test tool to validate if SCHED_DEADLINE can be set via sched_setattr() syscall.
+
+## Why?
+QM environment should not allow SCHED_DEADLINE be set via sched_setattr() syscall  
+and must validated via FFI tests.
+
+## How to deny is made?
+During the QM service startup it passes arguments to Podman. One of these arguments is `seccomp=/usr/share/qm/seccomp.json` which contains rules that deny the `sched_setattr()`.
+
+## How to test? 
+
+```
+host> gcc -o execute_sched_setattr execute_sched_setattr.c -Wall  # build the bin
+host> cp execute_sched_setattr /usr/lib/qm/rootfs/root/  # copy the bin to QM partition
+
+# podman exec -it qm bash  # Execute the test, it must fail in recent versions of QM
+bash-5.1# cd /root && ./execute_sched_setattr
+Current Scheduling Policy: SCHED_OTHER
+Current Priority: 0
+sched_setattr failed: Operation not permitted
+```

tests/e2e/tools/FFI/deny_sched_setattr/execute_sched_setattr.c

@@ -0,0 +1,91 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <linux/sched.h>
+#include <sys/syscall.h>
+#include <linux/types.h>
+#include <sched.h>
+
+struct sched_attr {
+    __u32 size;
+
+    __u32 sched_policy;
+    __u64 sched_flags;
+
+    // SCHED_NORMAL, SCHED_BATCH
+    __s32 sched_nice;
+
+    // SCHED_FIFO, SCHED_RR
+    __u32 sched_priority;
+
+    // SCHED_DEADLINE
+    __u64 sched_runtime;
+    __u64 sched_deadline;
+    __u64 sched_period;
+};
+
+int sched_setattr(pid_t pid, const struct sched_attr *attr, unsigned int flags) {
+    return syscall(SYS_sched_setattr, pid, attr, flags);
+}
+
+// Function to get the scheduling policy and priority of the current process
+void get_sched() {
+    int policy;
+    struct sched_param param;
+
+    // Get current scheduling policy
+    policy = sched_getscheduler(0);
+    if (policy == -1) {
+        perror("sched_getscheduler");
+        exit(EXIT_FAILURE);
+    }
+
+    // Get the current priority
+    if (sched_getparam(0, &param) == -1) {
+        perror("sched_getparam");
+        exit(EXIT_FAILURE);
+    }
+
+    printf("Current Scheduling Policy: ");
+    switch (policy) {
+        case SCHED_OTHER:
+            printf("SCHED_OTHER\n");
+            break;
+        case SCHED_FIFO:
+            printf("SCHED_FIFO\n");
+            break;
+        case SCHED_RR:
+            printf("SCHED_RR\n");
+            break;
+        case SCHED_DEADLINE:
+            printf("SCHED_DEADLINE\n");
+            break;
+        default:
+            printf("Unknown\n");
+    }
+
+    printf("Current Priority: %d\n", param.sched_priority);
+}
+
+int main() {
+    struct sched_attr attr;
+    memset(&attr, 0, sizeof(attr));  // initialization
+    attr.size = sizeof(attr);
+    attr.sched_policy = SCHED_DEADLINE;
+    attr.sched_runtime = 10 * 1000 * 1000;  // 10 ms
+    attr.sched_deadline = 20 * 1000 * 1000;  // 20 ms
+    attr.sched_period = 30 * 1000 * 1000;  // 30 ms
+
+    get_sched();
+
+    if (sched_setattr(0, &attr, 0) == -1) {
+        perror("sched_setattr failed");
+        return 1;
+    }
+
+    // Now the thread should be running under SCHED_DEADLINE
+    get_sched();
+
+    return 0;
+}