rename kernel_module to kernel_modules, start README mass factorings

packages/kernel_modules/user/virt_to_phys_user.c

@@ -0,0 +1,26 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#userland-physical-address-experiments */
+
+#define _XOPEN_SOURCE 700
+#include <stdio.h> /* printf */
+#include <stdlib.h> /* EXIT_SUCCESS, EXIT_FAILURE, strtoull */
+
+#include "common.h" /* virt_to_phys_user */
+
+int main(int argc, char **argv)
+{
+	pid_t pid;
+	uintptr_t vaddr, paddr = 0;
+
+	if (argc < 3) {
+		printf("Usage: %s pid vaddr\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+	pid = strtoull(argv[1], NULL, 0);
+	vaddr = strtoull(argv[2], NULL, 0);
+	if (virt_to_phys_user(&paddr, pid, vaddr)) {
+		fprintf(stderr, "error: virt_to_phys_user\n");
+		return EXIT_FAILURE;
+	};
+	printf("0x%jx\n", (uintmax_t)paddr);
+	return EXIT_SUCCESS;
+}