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SubjectRe: [PATCH] proc/wchan: Use printk format instead of lookup_symbol_name()
On Thu, 17 Dec 2020 17:54:13 +0100 Helge Deller <deller@gmx.de> wrote:

> To resolve the symbol fuction name for wchan, use the printk format
> specifier %ps instead of manually looking up the symbol function name
> via lookup_symbol_name().
>
> Signed-off-by: Helge Deller <deller@gmx.de>
>

Please don't forget the "^---$" to separate the changelog from the
diff.

> #include <linux/module.h>
> @@ -386,19 +385,17 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
> struct pid *pid, struct task_struct *task)
> {
> unsigned long wchan;
> - char symname[KSYM_NAME_LEN];
>
> - if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
> - goto print0;
> + if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
> + wchan = get_wchan(task);
> + else
> + wchan = 0;
>
> - wchan = get_wchan(task);
> - if (wchan && !lookup_symbol_name(wchan, symname)) {
> - seq_puts(m, symname);
> - return 0;
> - }
> + if (wchan)
> + seq_printf(m, "%ps", (void *) wchan);
> + else
> + seq_putc(m, '0');
>
> -print0:
> - seq_putc(m, '0');
> return 0;
> }

We can simplify this further?

static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
seq_printf(m, "%ps", (void *)get_wchan(task));
else
seq_putc(m, '0');

return 0;
}


--- a/fs/proc/base.c~proc-wchan-use-printk-format-instead-of-lookup_symbol_name-fix
+++ a/fs/proc/base.c
@@ -384,15 +384,8 @@ static const struct file_operations proc
static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
- unsigned long wchan;
-
if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
- wchan = get_wchan(task);
- else
- wchan = 0;
-
- if (wchan)
- seq_printf(m, "%ps", (void *) wchan);
+ seq_printf(m, "%ps", (void *)get_wchan(task));
else
seq_putc(m, '0');

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