homework #2 - ProcFs

.gitignore

@@ -0,0 +1,52 @@
+# Prerequisites
+*.d
+
+# Object files
+*.o
+*.ko
+*.obj
+*.elf
+
+# Linker output
+*.ilk
+*.map
+*.exp
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Libraries
+*.lib
+*.a
+*.la
+*.lo
+
+# Shared objects (inc. Windows DLLs)
+*.dll
+*.so
+*.so.*
+*.dylib
+
+# Executables
+*.exe
+*.out
+*.app
+*.i*86
+*.x86_64
+*.hex
+
+# Debug files
+*.dSYM/
+*.su
+*.idb
+*.pdb
+
+# Kernel Module Compile Results
+*.mod*
+*.cmd
+.tmp_versions/
+modules.order
+Module.symvers
+Mkfile.old
+dkms.conf

01_Homework_proc/Makefile

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+ifneq ($(KERNELRELEASE),)
+# kbuild part of makefile
+obj-m := my_module.o
+else
+# normal makefile
+
+KDIR = /lib/modules/$(shell uname -r)/build
+
+all:
+	make -C $(KDIR)  M=$$PWD modules
+clean:
+	make -C $(KDIR)  M=$$PWD clean
+
+endif

01_Homework_proc/README.md

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+# Kernel modules: homework #2
+
+Add proc functionality (read only handler)
+
+Filelist 
+
+my_module.c
+
+Makefile
+

01_Homework_proc/my_module.c

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+// SPDX-License-Identifier: GPL-2.0+
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/proc_fs.h>
+#include <linux/uaccess.h>
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Yurii Bezkor");
+MODULE_DESCRIPTION("Proc module");
+MODULE_VERSION("0.1");
+
+#define PROC_BUFFER_SIZE 100
+
+static char procfs_buffer[PROC_BUFFER_SIZE] = { 0 };
+static size_t procfs_buffer_size;
+
+static struct proc_dir_entry *proc_file;
+static struct proc_dir_entry *proc_dir;
+
+#define PROC_FILE_NAME "hello"
+#define PROC_DIR_NAME "bezkor"
+
+static ssize_t procfs_read(struct file *file, char __user *buffer,
+			   size_t count_bytes, loff_t *offset)
+{
+	pr_info("Read info from procfs\n");
+
+	if (*offset > 0 || count_bytes < procfs_buffer_size) {
+		pr_err("Illegal buffer\n");
+		return 0;
+	}
+
+	if (copy_to_user(buffer, procfs_buffer, procfs_buffer_size)) {
+		pr_err("Error copy_to_user\n");
+		return -EFAULT;
+	};
+	*offset = procfs_buffer_size;
+	return procfs_buffer_size;
+}
+
+static ssize_t procfs_write(struct file *file, const char __user *buffer,
+			    size_t count_bytes, loff_t *offset)
+{
+	pr_info("Write info to procfs\n");
+
+	if (*offset > 0 || count_bytes > PROC_BUFFER_SIZE) {
+		pr_err("Illegal buffer\n");
+		return -EFAULT;
+	}
+
+	if (copy_from_user(procfs_buffer, buffer, count_bytes)) {
+		pr_err("Error copy_from_user\n");
+		return -EFAULT;
+	};
+
+	procfs_buffer_size = count_bytes;
+	pr_info("Buffer is %s\n", procfs_buffer);
+
+	return procfs_buffer_size;
+}
+
+static const struct file_operations fops = {
+				.owner = THIS_MODULE,
+				.read = procfs_read,
+				.write = procfs_write };
+
+static int __init hello_init(void)
+{
+	proc_dir = proc_mkdir(PROC_DIR_NAME, NULL);
+	if (proc_dir == NULL) {
+		pr_err("PROC module: Could not create /proc/%s/ folder !\n",
+		       PROC_DIR_NAME);
+		return -ENOMEM;
+	}
+	proc_file = proc_create(PROC_FILE_NAME, 0666, proc_dir, &fops);
+	if (proc_file == NULL) {
+		pr_err("PROC module: Could not create /proc/%s/%s !\n",
+		       PROC_DIR_NAME, PROC_FILE_NAME);
+		proc_remove(proc_file);
+		proc_remove(proc_dir);
+		return -ENOMEM;
+	}
+	procfs_buffer_size = 0;
+	pr_info("PROC module: Hello /proc/%s/%s !\n", PROC_DIR_NAME,
+		PROC_FILE_NAME);
+	return 0;
+}
+
+static void __exit hello_exit(void)
+{
+	proc_remove(proc_file);
+	proc_remove(proc_dir);
+	pr_info("PROC module: Goodbye /proc/%s/%s !\n", PROC_DIR_NAME,
+		PROC_FILE_NAME);
+}
+
+module_init(hello_init);
+module_exit(hello_exit);

Makefile

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+
+CF = clang-format-12 -i
+
+.PHONY: format check-format check-arg
+
+check-arg:
+	@if test "$(DIR)" = "" ; then \
+		echo DIR not set; \
+		echo Use:;\
+		echo make cmd DIR=...;\
+		echo ;\
+		exit 1; \
+	fi
+
+format: check-arg
+	@echo format SRC
+	$(CF) $(DIR)/*.[ch]
+
+check-format: check-arg
+	@echo "\n\e[32m*** Check format of source code ***\e[0m\n"
+	@utils/checkpatch.pl --no-tree -f $(DIR)/*.[ch]

Task00_HW_kernel_module/Makefile

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+ifneq ($(KERNELRELEASE),)
+# kbuild part of makefile
+obj-m := hello.o
+else
+# normal makefile
+
+KDIR = /lib/modules/$(shell uname -r)/build
+
+all:
+	make -C $(KDIR)  M=$$PWD modules
+clean:
+	make -C $(KDIR)  M=$$PWD clean
+
+endif

Task00_HW_kernel_module/README.md

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+# Home work
+[x] Write hello_world module: fill module author, description, version e.t.c.
+
+[x] Write into the console
+
+- [x] module initialization;
+
+- [x] module de-initialization;
+
+[x] Use module parameters to write simple calculator: module should print sum,
+substraction and multiplication of two numbers passed as parameters.
+
+[x] Don’t forget to use checkpatch.pl – all not-corresponding drivers will be
+rejected.
+
+[x] Github: hello.c, hello.ko, Makefile
+
+## Sample commands
+
+```shell
+insmod hello.ko
+rmmod hello
+```
+
+```shell
+insmod hello.ko sum=1,2
+```
+
+```shell
+insmod hello.ko sum=1,2 subst=2,4 prod=3,3
+```
+
+dmesg results:
+
+```shell
+[  +7,950982] HELLO: Hello Kernel!
+[  +0,000001] SUM(1,2) = 3
+[  +0,000001] SUBST(2,4) = -2
+[  +0,000000] PROD(3,3) = 9
+[  +7,678936] HELLO: Goodbye Kernel!
+```

Task00_HW_kernel_module/hello.c

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+// SPDX-License-Identifier: GPL-2.0+
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/kernel.h>
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Yurii Bezkor");
+MODULE_DESCRIPTION("Hello world kernel module");
+MODULE_VERSION("0.2");
+
+static int sum[2];
+static int sum_count;
+module_param_array(sum, int, &sum_count, 0);
+MODULE_PARM_DESC(sum, "Sum of two integers");
+
+static int subst[2];
+static int subst_count;
+module_param_array(subst, int, &subst_count, 0);
+MODULE_PARM_DESC(subst, "Substraction of two integers");
+
+static int prod[2];
+static int prod_count;
+module_param_array(prod, int, &prod_count, 0);
+MODULE_PARM_DESC(prod, "Substraction of two integers");
+
+static int __init hello_init(void)
+{
+	int result;
+
+	pr_info("HELLO: Hello Kernel!\n");
+	if (sum_count) {
+		if (sum_count == 2) {
+			result = sum[0] + sum[1];
+			pr_info("SUM(%d,%d) = %d\n", sum[0], sum[1], result);
+		} else {
+			pr_err("SUM passed %d parameters, must be 2!\n",
+			       sum_count);
+			return -EINVAL;
+		}
+	}
+
+	if (subst_count) {
+		if (subst_count == 2) {
+			result = subst[0] - subst[1];
+			pr_info("SUBST(%d,%d) = %d\n", subst[0], subst[1], result);
+		} else {
+			pr_err("SUBST passed %d parameters, must be 2!\n",
+			       subst_count);
+			return -EINVAL;
+		}
+	}
+
+	if (prod_count) {
+		if (prod_count == 2) {
+			result = prod[0] * prod[1];
+			pr_info("PROD(%d,%d) = %d\n", prod[0], prod[1], result);
+		} else {
+			pr_err("PRODT passed %d parameters, must be 2!\n",
+			       prod_count);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+static void __exit hello_exit(void)
+{
+	pr_info("HELLO: Goodbye Kernel!\n");
+}
+
+module_init(hello_init);
+module_exit(hello_exit);