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tracing/osnoise: Allow arbitrarily long CPU string 

Allocate kernel memory for processing CPU string
(/sys/kernel/tracing/osnoise/cpus) also in osnoise_cpus_write to allow
the writing of a CPU string of an arbitrary length.

This replaces the 256-byte buffer, which is insufficient with the rising
number of CPUs. For example, if I wanted to measure on every even CPU
on a system with 256 CPUs, the string would be 456 characters long.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250425091839.343289-1-tglozar@redhat.com
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Tomas Glozar 2025-04-25 11:18:39 +02:00 committed by Steven Rostedt (Google)
parent a54665ab7c
commit 17f89102fe
1 changed files with 5 additions and 4 deletions
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9
kernel/trace/trace_osnoise.c
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@ -2302,7 +2302,7 @@ osnoise_cpus_read(struct file *filp, char __user *ubuf, size_t count,
* osnoise_cpus_write - Write function for "cpus" entry
* @filp: The active open file structure
* @ubuf: The user buffer that contains the value to write
* @cnt: The maximum number of bytes to write to "file"
* @count: The maximum number of bytes to write to "file"
* @ppos: The current position in @file
*
* This function provides a write implementation for the "cpus"
@ -2320,10 +2320,11 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count,
{
cpumask_var_t osnoise_cpumask_new;
int running, err;
char buf[256];
char *buf __free(kfree) = NULL;
if (count >= 256)
return -EINVAL;
buf = kmalloc(count, GFP_KERNEL);
if (!buf)
return -ENOMEM;
if (copy_from_user(buf, ubuf, count))
return -EFAULT;