diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index d352fb4b7709e101861c398b5ade7c9c0fc0b2bf..27bf203ef05a2cc5e1d1a0449f659b5bf54cecdc 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7583,6 +7583,91 @@ static const struct file_operations snapshot_raw_fops = { #endif /* CONFIG_TRACER_SNAPSHOT */ +/* + * trace_min_max_write - Write a u64 value to a trace_min_max_param struct + * @filp: The active open file structure + * @ubuf: The userspace provided buffer to read value into + * @cnt: The maximum number of bytes to read + * @ppos: The current "file" position + * + * This function implements the write interface for a struct trace_min_max_param. + * The filp->private_data must point to a trace_min_max_param structure that + * defines where to write the value, the min and the max acceptable values, + * and a lock to protect the write. + */ +static ssize_t +trace_min_max_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos) +{ + struct trace_min_max_param *param = filp->private_data; + u64 val; + int err; + + if (!param) + return -EFAULT; + + err = kstrtoull_from_user(ubuf, cnt, 10, &val); + if (err) + return err; + + if (param->lock) + mutex_lock(param->lock); + + if (param->min && val < *param->min) + err = -EINVAL; + + if (param->max && val > *param->max) + err = -EINVAL; + + if (!err) + *param->val = val; + + if (param->lock) + mutex_unlock(param->lock); + + if (err) + return err; + + return cnt; +} + +/* + * trace_min_max_read - Read a u64 value from a trace_min_max_param struct + * @filp: The active open file structure + * @ubuf: The userspace provided buffer to read value into + * @cnt: The maximum number of bytes to read + * @ppos: The current "file" position + * + * This function implements the read interface for a struct trace_min_max_param. + * The filp->private_data must point to a trace_min_max_param struct with valid + * data. + */ +static ssize_t +trace_min_max_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) +{ + struct trace_min_max_param *param = filp->private_data; + char buf[U64_STR_SIZE]; + int len; + u64 val; + + if (!param) + return -EFAULT; + + val = *param->val; + + if (cnt > sizeof(buf)) + cnt = sizeof(buf); + + len = snprintf(buf, sizeof(buf), "%llu\n", val); + + return simple_read_from_buffer(ubuf, cnt, ppos, buf, len); +} + +const struct file_operations trace_min_max_fops = { + .open = tracing_open_generic, + .read = trace_min_max_read, + .write = trace_min_max_write, +}; + #define TRACING_LOG_ERRS_MAX 8 #define TRACING_LOG_LOC_MAX 128 diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index cd80d046c7a5d413225951ef90746c8c10a44185..22f8c652ef8b40a64ab7b866458c6601d0a1c206 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1952,4 +1952,22 @@ static inline bool is_good_name(const char *name) return true; } +/* + * This is a generic way to read and write a u64 value from a file in tracefs. + * + * The value is stored on the variable pointed by *val. The value needs + * to be at least *min and at most *max. The write is protected by an + * existing *lock. + */ +struct trace_min_max_param { + struct mutex *lock; + u64 *val; + u64 *min; + u64 *max; +}; + +#define U64_STR_SIZE 24 /* 20 digits max */ + +extern const struct file_operations trace_min_max_fops; + #endif /* _LINUX_KERNEL_TRACE_H */