On Tue, 18 Aug 2026 01:53:18 +0000 Bradley Morgan <[email protected]> wrote:
> This enabled knob is a disgusting terrible hack. It has rolled its > own read/write pair since 2007, writing '1' or '0' into a three byte > buffer by hand just to print a single character, with an XXX comment > begging debugfs for write callbacks on bool files. > DEFINE_DEBUGFS_ATTRIBUTE showed up in 2016 and does exactly that, so > the disgusting terrible hack has outlived its excuse for nine years. > Kill it, and the stale comment with it. In other words, does this mean something like the following? This "enable" knob implemented custom read/write logic, manually writing "1" or "0" to a 3-byte buffer solely to output a single character. As suggested by comments calling for `debugfs` to support write callbacks for boolean files, using `DEFINE_DEBUGFS_ATTRIBUTE` eliminates the need for these callbacks. Thanks, > > The behavior does not change, except the write only accepts 0/1 now > instead of y/n/on/off, and nothing uses anything else. > > Signed-off-by: Bradley Morgan <[email protected]> > --- > Changes since v1: > - Added the missing Signed-off-by, sorry. > > kernel/kprobes.c | 43 +++++++++---------------------------------- > 1 file changed, 9 insertions(+), 34 deletions(-) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index bfc89083daa9..044c6b5fd2aa 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -3013,47 +3013,22 @@ static int disarm_all_kprobes(void) > return ret; > } > > -/* > - * XXX: The debugfs bool file interface doesn't allow for callbacks > - * when the bool state is switched. We can reuse that facility when > - * available > - */ > -static ssize_t read_enabled_file_bool(struct file *file, > - char __user *user_buf, size_t count, loff_t *ppos) > +static int kprobes_enabled_set(void *data, u64 val) > { > - char buf[3]; > + if (val) > + return arm_all_kprobes(); > > - if (!kprobes_all_disarmed) > - buf[0] = '1'; > - else > - buf[0] = '0'; > - buf[1] = '\n'; > - buf[2] = 0x00; > - return simple_read_from_buffer(user_buf, count, ppos, buf, 2); > + return disarm_all_kprobes(); > } > > -static ssize_t write_enabled_file_bool(struct file *file, > - const char __user *user_buf, size_t count, loff_t *ppos) > +static int kprobes_enabled_get(void *data, u64 *val) > { > - bool enable; > - int ret; > - > - ret = kstrtobool_from_user(user_buf, count, &enable); > - if (ret) > - return ret; > - > - ret = enable ? arm_all_kprobes() : disarm_all_kprobes(); > - if (ret) > - return ret; > - > - return count; > + *val = !kprobes_all_disarmed; > + return 0; > } > > -static const struct file_operations fops_kp = { > - .read = read_enabled_file_bool, > - .write = write_enabled_file_bool, > - .llseek = default_llseek, > -}; > +DEFINE_DEBUGFS_ATTRIBUTE(fops_kp, kprobes_enabled_get, > + kprobes_enabled_set, "%llu\n"); > > static int __init debugfs_kprobe_init(void) > { > -- > 2.47.3 > -- Masami Hiramatsu (Google) <[email protected]>
