linux-kernel - [PATCH] kheaders: Move from proc to sysfs

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Message-Id: <20190503182459.159121-1-joel@joelfernandes.org>
Date:   Fri,  3 May 2019 14:24:59 -0400
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Adrian Ratiu <adrian.ratiu@...labora.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>, atishp04@...il.com,
        bpf@...r.kernel.org, Brendan Gregg <bgregg@...flix.com>,
        Brendan Gregg <brendan.d.gregg@...il.com>, dancol@...gle.com,
        Daniel Borkmann <daniel@...earbox.net>,
        Dan Williams <dan.j.williams@...el.com>,
        dietmar.eggemann@....com, duyuchao <yuchao.du@...soc.com>,
        gregkh@...uxfoundation.org, Guenter Roeck <groeck@...omium.org>,
        Jonathan Corbet <corbet@....net>,
        Karim Yaghmour <karim.yaghmour@...rsys.com>,
        Kees Cook <keescook@...omium.org>, kernel-team@...roid.com,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-trace-devel@...r.kernel.org,
        Manjo Raja Rao <linux@...ojrajarao.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Michał Gregorczyk <michalgr@...com>,
        Michal Gregorczyk <michalgr@...e.com>,
        Mohammad Husain <russoue@...il.com>,
        Olof Johansson <olof@...om.net>, qais.yousef@....com,
        rdunlap@...radead.org, Shuah Khan <shuah@...nel.org>,
        Srinivas Ramana <sramana@...eaurora.org>,
        Tamir Carmeli <carmeli.tamir@...il.com>, yhs@...com
Subject: [PATCH] kheaders: Move from proc to sysfs

The kheaders archive consisting of the kernel headers used for compiling
bpf programs is in /proc. However there is concern that moving it here
will make it permanent. Let us move it to /sys/kernel as discussed [1].

[1] https://lore.kernel.org/patchwork/patch/1067310/#1265969

Suggested-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
This patch applies on top of the previous patch that was applied to the
driver tree:
https://lore.kernel.org/patchwork/patch/1067310/

 kernel/kheaders.c | 40 ++++++++++++++++------------------------
 1 file changed, 16 insertions(+), 24 deletions(-)

diff --git a/kernel/kheaders.c b/kernel/kheaders.c
index 70ae6052920d..6a16f8f6898d 100644
--- a/kernel/kheaders.c
+++ b/kernel/kheaders.c
@@ -8,9 +8,8 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
-#include <linux/proc_fs.h>
+#include <linux/kobject.h>
 #include <linux/init.h>
-#include <linux/uaccess.h>
 
 /*
  * Define kernel_headers_data and kernel_headers_data_end, within which the
@@ -31,39 +30,32 @@ extern char kernel_headers_data;
 extern char kernel_headers_data_end;
 
 static ssize_t
-ikheaders_read_current(struct file *file, char __user *buf,
-		      size_t len, loff_t *offset)
+ikheaders_read(struct file *file,  struct kobject *kobj,
+	       struct bin_attribute *bin_attr,
+	       char *buf, loff_t off, size_t len)
 {
-	return simple_read_from_buffer(buf, len, offset,
-				       &kernel_headers_data,
-				       &kernel_headers_data_end -
-				       &kernel_headers_data);
+	memcpy(buf, &kernel_headers_data + off, len);
+	return len;
 }
 
-static const struct file_operations ikheaders_file_ops = {
-	.read = ikheaders_read_current,
-	.llseek = default_llseek,
+static struct bin_attribute kheaders_attr __ro_after_init = {
+	.attr = {
+		.name = "kheaders.tar.xz",
+		.mode = S_IRUGO,
+	},
+	.read = &ikheaders_read,
 };
 
 static int __init ikheaders_init(void)
 {
-	struct proc_dir_entry *entry;
-
-	/* create the current headers file */
-	entry = proc_create("kheaders.tar.xz", S_IRUGO, NULL,
-			    &ikheaders_file_ops);
-	if (!entry)
-		return -ENOMEM;
-
-	proc_set_size(entry,
-		      &kernel_headers_data_end -
-		      &kernel_headers_data);
-	return 0;
+	kheaders_attr.size = (&kernel_headers_data_end -
+			      &kernel_headers_data);
+	return sysfs_create_bin_file(kernel_kobj, &kheaders_attr);
 }
 
 static void __exit ikheaders_cleanup(void)
 {
-	remove_proc_entry("kheaders.tar.xz", NULL);
+	sysfs_remove_bin_file(kernel_kobj, &kheaders_attr);
 }
 
 module_init(ikheaders_init);
-- 
2.21.0.1020.gf2820cf01a-goog