From eb2e6c3a8d66ff37b2ee26cd32334ae0e05fd596 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= Date: Sun, 3 Nov 2024 17:03:38 +0000 Subject: [PATCH] sysfs: bin_attribute: add const read/write callback variants MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit To make it possible to put struct bin_attribute into read-only memory, the sysfs core has to stop passing mutable pointers to the read() and write() callbacks. As there are numerous implementors of these callbacks throughout the tree it's not possible to change all of them at once. To enable a step-by-step transition, add new variants of the read() and write() callbacks which differ only in the constness of the struct bin_attribute argument. As most binary attributes are defined through macros, extend these macros to transparently handle both variants of callbacks to minimize the churn during the transition. As soon as all handlers are switch to the const variant, the non-const one can be removed together with the transition machinery. Signed-off-by: Thomas Weißschuh Acked-by: Krzysztof Wilczyński Link: https://lore.kernel.org/r/20241103-sysfs-const-bin_attr-v2-9-71110628844c@weissschuh.net Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/file.c | 22 +++++++++++++++++----- include/linux/sysfs.h | 25 +++++++++++++++++++++++-- 2 files changed, 40 insertions(+), 7 deletions(-) diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index 6d39696b4306..785408861c01 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -91,9 +91,12 @@ static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf, count = size - pos; } - if (!battr->read) + if (!battr->read && !battr->read_new) return -EIO; + if (battr->read_new) + return battr->read_new(of->file, kobj, battr, buf, pos, count); + return battr->read(of->file, kobj, battr, buf, pos, count); } @@ -152,9 +155,12 @@ static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf, if (!count) return 0; - if (!battr->write) + if (!battr->write && !battr->write_new) return -EIO; + if (battr->write_new) + return battr->write_new(of->file, kobj, battr, buf, pos, count); + return battr->write(of->file, kobj, battr, buf, pos, count); } @@ -323,13 +329,19 @@ int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent, const struct kernfs_ops *ops; struct kernfs_node *kn; + if (battr->read && battr->read_new) + return -EINVAL; + + if (battr->write && battr->write_new) + return -EINVAL; + if (battr->mmap) ops = &sysfs_bin_kfops_mmap; - else if (battr->read && battr->write) + else if ((battr->read || battr->read_new) && (battr->write || battr->write_new)) ops = &sysfs_bin_kfops_rw; - else if (battr->read) + else if (battr->read || battr->read_new) ops = &sysfs_bin_kfops_ro; - else if (battr->write) + else if (battr->write || battr->write_new) ops = &sysfs_bin_kfops_wo; else ops = &sysfs_file_kfops_empty; diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h index d17c473c1ef2..d713a6445a62 100644 --- a/include/linux/sysfs.h +++ b/include/linux/sysfs.h @@ -305,8 +305,12 @@ struct bin_attribute { struct address_space *(*f_mapping)(void); ssize_t (*read)(struct file *, struct kobject *, struct bin_attribute *, char *, loff_t, size_t); + ssize_t (*read_new)(struct file *, struct kobject *, const struct bin_attribute *, + char *, loff_t, size_t); ssize_t (*write)(struct file *, struct kobject *, struct bin_attribute *, char *, loff_t, size_t); + ssize_t (*write_new)(struct file *, struct kobject *, + const struct bin_attribute *, char *, loff_t, size_t); loff_t (*llseek)(struct file *, struct kobject *, const struct bin_attribute *, loff_t, int); int (*mmap)(struct file *, struct kobject *, const struct bin_attribute *attr, @@ -325,11 +329,28 @@ struct bin_attribute { */ #define sysfs_bin_attr_init(bin_attr) sysfs_attr_init(&(bin_attr)->attr) +typedef ssize_t __sysfs_bin_rw_handler_new(struct file *, struct kobject *, + const struct bin_attribute *, char *, loff_t, size_t); + /* macros to create static binary attributes easier */ #define __BIN_ATTR(_name, _mode, _read, _write, _size) { \ .attr = { .name = __stringify(_name), .mode = _mode }, \ - .read = _read, \ - .write = _write, \ + .read = _Generic(_read, \ + __sysfs_bin_rw_handler_new * : NULL, \ + default : _read \ + ), \ + .read_new = _Generic(_read, \ + __sysfs_bin_rw_handler_new * : _read, \ + default : NULL \ + ), \ + .write = _Generic(_write, \ + __sysfs_bin_rw_handler_new * : NULL, \ + default : _write \ + ), \ + .write_new = _Generic(_write, \ + __sysfs_bin_rw_handler_new * : _write, \ + default : NULL \ + ), \ .size = _size, \ }