test: rework test_error_code to not need a separate initrd image

Add the source of the binary since it was missing, and include it in our
rootfs images. This avoids the need for a separate initrd image.

Signed-off-by: Pablo Barbáchano <pablob@amazon.com>

Author: pb8o

resources/overlay/usr/local/bin/devmemread.c

@@ -0,0 +1,31 @@
+#include <assert.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sys/mount.h>
+
+/*
+ * We try to trigger ENOSYS by mapping a file into memory and then tries to
+ * load the content from an offset in the file bigger than its length into a
+ * register asm volatile ("ldr %0, [%1], 4" : "=r" (ret), "+r" (buf));
+ */
+
+int main()
+{
+	int ret, fd;
+	char *buf;
+
+	// Assume /dev is mounted
+	fprintf(stderr, "open /dev/mem\n");
+	fd = open("/dev/mem", O_RDWR);
+	assert(fd > 0);
+
+	buf = mmap(NULL, 65536, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0xf0000);
+	assert(buf != MAP_FAILED);
+
+	fprintf(stderr, "try to ldr\n");
+	asm volatile("ldr %0, [%1], 4" : "=r" (ret), "+r" (buf));
+
+	fprintf(stderr, "success\n");
+	return 0;
+}

resources/rebuild.sh

@@ -167,6 +167,9 @@ BIN=overlay/usr/local/bin
 compile_and_install $BIN/init.c    $BIN/init
 compile_and_install $BIN/fillmem.c $BIN/fillmem
 compile_and_install $BIN/readmem.c $BIN/readmem
+if [ $ARCH == "aarch64" ]; then
+    compile_and_install $BIN/devmemread.c $BIN/devmemread
+fi
 
 # build_rootfs ubuntu-18.04 bionic
 # build_rootfs ubuntu-20.04 focal

tests/integration_tests/functional/test_error_code.py

@@ -14,32 +14,27 @@
     reason="The error code returned on aarch64 will not be returned on x86 "
     "under the same conditions.",
 )
-def test_enosys_error_code(uvm_plain, artifact_dir):
+def test_enosys_error_code(uvm_plain):
     """
     Test that ENOSYS error is caught and firecracker exits gracefully.
     """
-    # On aarch64 we trigger this error by adding to initrd a C program that
+    # On aarch64 we trigger this error by running a C program that
     # maps a file into memory and then tries to load the content from an
     # offset in the file bigger than its length into a register asm volatile
     # ("ldr %0, [%1], 4" : "=r" (ret), "+r" (buf));
     vm = uvm_plain
-    vm.jailer.daemonize = False
     vm.spawn()
     vm.memory_monitor = None
-
-    vm.initrd_file = artifact_dir / "initrd_enosys.img"
     vm.basic_config(
-        add_root_device=False,
         vcpu_count=1,
-        boot_args="console=ttyS0 reboot=k panic=1 pci=off",
-        use_initrd=True,
+        boot_args="reboot=k panic=1 pci=off init=/usr/local/bin/devmemread",
     )
     vm.start()
 
     # Check if FC process is closed
     wait_process_termination(vm.jailer_clone_pid)
 
     vm.check_log_message(
-        "Received ENOSYS error because KVM failed to" " emulate an instruction."
+        "Received ENOSYS error because KVM failed to emulate an instruction."
     )
     vm.check_log_message("Vmm is stopping.")