2015-10-01 10:57 GMT+03:00 Ingo Molnar <[email protected]>:
> diff --git a/Documentation/filesystems/proc.txt
> b/Documentation/filesystems/proc.txt
> index d411ca63c8b6..db64f7d6492d 100644
> --- a/Documentation/filesystems/proc.txt
> +++ b/Documentation/filesystems/proc.txt
> @@ -140,7 +140,8 @@ Table 1-1: Process specific entries in /proc
> stat Process status
> statm Process memory status information
> status Process status in human readable form
> - wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
> + wchan If CONFIG_KALLSYMS=y, wchan (the kernel function the process
> is
> + blocked in) symbol string. "0" if not blocked or !KALLSYMS.
/proc/PID/wchan is under #ifdef CONFIG_KALLSYMS.
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index b25eee4cead5..6f05aabce3aa 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -430,13 +430,10 @@ static int proc_pid_wchan(struct seq_file *m, struct
> pid_namespace *ns,
>
> wchan = get_wchan(task);
>
> - if (lookup_symbol_name(wchan, symname) < 0) {
> - if (!ptrace_may_access(task, PTRACE_MODE_READ))
> - return 0;
> - seq_printf(m, "%lu", wchan);
> - } else {
> + if (!lookup_symbol_name(wchan, symname))
> seq_printf(m, "%s", symname);
> - }
> + else
> + seq_putc(m, '0');
Maybe we should respect 'kptr_restrict' sysctl when we use '%ps', '%pB' etc.
printk formats (AFAIK %ps just prints address if KALLSYMS=n, or lookup failed).
In that case you could just do 'seq_printf(m, "%ps", wchan)'.
OTOH, %ps, %pS are used mostly in debugging, so investigating some crash
in production kernel with no !KALLSYMS and with kptr_restrict != 0
will be a nightmare.
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