On 19 August 2026 00:08:13 BST, Masami Hiramatsu <[email protected]> wrote: >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. >
ehhhhh, well, my description very well tells someone about why this is bad, and a hack, and everything. Your description is good though... But I love to have my personality in my descriptions :( >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 >> > > > Thanks!
