linux-kernel - [PATCH 3/4] btf: Switch vmlinux BTF attribute to sysfs_bin_attr_simple

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Message-Id: <20241205-sysfs-const-bin_attr-simple-v1-3-4a4e4ced71e3@weissschuh.net>
Date: Thu, 05 Dec 2024 18:35:15 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Michael Ellerman <mpe@...erman.id.au>, 
 Nicholas Piggin <npiggin@...il.com>, 
 Christophe Leroy <christophe.leroy@...roup.eu>, 
 Naveen N Rao <naveen@...nel.org>, Madhavan Srinivasan <maddy@...ux.ibm.com>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, 
 Luis Chamberlain <mcgrof@...nel.org>, Petr Pavlu <petr.pavlu@...e.com>, 
 Sami Tolvanen <samitolvanen@...gle.com>, 
 Daniel Gomez <da.gomez@...sung.com>, Armin Wolf <W_Armin@....de>, 
 Hans de Goede <hdegoede@...hat.com>, 
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
 Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, 
 linux-modules@...r.kernel.org, platform-driver-x86@...r.kernel.org, 
 bpf@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH 3/4] btf: Switch vmlinux BTF attribute to
 sysfs_bin_attr_simple_read()

The generic function from the sysfs core can replace the custom one.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>

---
This is a replacement for [0], as Alexei was not happy about BIN_ATTR_SIMPLE_RO()

[0] https://lore.kernel.org/lkml/20241122-sysfs-const-bin_attr-bpf-v1-1-823aea399b53@weissschuh.net/
---
 kernel/bpf/sysfs_btf.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c
index fedb54c94cdb830a4890d33677dcc5a6e236c13f..81d6cf90584a7157929c50f62a5c6862e7a3d081 100644
--- a/kernel/bpf/sysfs_btf.c
+++ b/kernel/bpf/sysfs_btf.c
@@ -12,24 +12,16 @@
 extern char __start_BTF[];
 extern char __stop_BTF[];

-static ssize_t
-btf_vmlinux_read(struct file *file, struct kobject *kobj,
-		 struct bin_attribute *bin_attr,
-		 char *buf, loff_t off, size_t len)
-{
-	memcpy(buf, __start_BTF + off, len);
-	return len;
-}
-
 static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {
 	.attr = { .name = "vmlinux", .mode = 0444, },
-	.read = btf_vmlinux_read,
+	.read_new = sysfs_bin_attr_simple_read,
 };

 struct kobject *btf_kobj;

 static int __init btf_vmlinux_init(void)
 {
+	bin_attr_btf_vmlinux.private = __start_BTF;
 	bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF;

 	if (bin_attr_btf_vmlinux.size == 0)

-- 
2.47.1