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>
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@ -2302,7 +2302,7 @@ osnoise_cpus_read(struct file *filp, char __user *ubuf, size_t count,
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* osnoise_cpus_write - Write function for "cpus" entry
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* @filp: The active open file structure
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* @ubuf: The user buffer that contains the value to write
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* @cnt: The maximum number of bytes to write to "file"
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* @count: The maximum number of bytes to write to "file"
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* @ppos: The current position in @file
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*
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* This function provides a write implementation for the "cpus"
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@ -2320,10 +2320,11 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count,
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{
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cpumask_var_t osnoise_cpumask_new;
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int running, err;
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char buf[256];
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char *buf __free(kfree) = NULL;
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if (count >= 256)
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return -EINVAL;
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buf = kmalloc(count, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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if (copy_from_user(buf, ubuf, count))
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return -EFAULT;
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