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Subject[PATCH] vfs: Add PERM_* symbolic helpers for common file mode/permissions

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Mon, Nov 27, 2017 at 12:14:07AM +0100, Thomas Gleixner wrote:
> > static int __init pt_dump_debug_init(void)
> > {
> > + pe_knl = debugfs_create_file("kernel_page_tables", S_IRUSR, NULL, NULL,
> > + &ptdump_fops);
> > + if (!pe_knl)
> > return -ENOMEM;
> >
> > + pe_curknl = debugfs_create_file("current_page_tables_knl", S_IRUSR,
> > + NULL, NULL, &ptdump_curknl_fops);
> > + if (!pe_curknl)
> > + goto err;
> > +
> > +#ifdef CONFIG_KAISER
> > + pe_curusr = debugfs_create_file("current_page_tables_usr", S_IRUSR,
> > + NULL, NULL, &ptdump_curusr_fops);
> > + if (!pe_curusr)
> > + goto err;
> > +#endif
> > return 0;
> > +err:
> > + pt_dump_debug_remove_files();
> > + return -ENOMEM;
> > }
>
>
> Could we pretty please use the octal permission thing? I can't read
> thise S_crap nonsense.

They are completely unreadable to me too. So if we added these helpers I sent a
year ago:

https://lwn.net/Articles/696231/

Then the above could be written as:

pe_curknl = debugfs_create_file("current_page_tables_knl", PERM_r________,
NULL, NULL, &ptdump_curknl_fops);

... etc., which is much more readable IMHO. Not only that, it would be trivial to
_write_ permission masks as well. I just wrote this:

PERM_rw_r__r__

Which is so much more readable than "S_IRUGO|S_IWUSR" or even "0644". The former
pattern is used 527 times in the kernel ...

The patch below adds it to the current kernel.

Thanks,

Ingo
---
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/stat.h | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)

diff --git a/include/linux/stat.h b/include/linux/stat.h
index 22484e44544d..fc389c3a8692 100644
--- a/include/linux/stat.h
+++ b/include/linux/stat.h
@@ -6,6 +6,38 @@
#include <asm/stat.h>
#include <uapi/linux/stat.h>

+/*
+ * Human readable symbolic definitions for common
+ * file permissions:
+ */
+#define PERM_r________ 0400
+#define PERM_r__r_____ 0440
+#define PERM_r__r__r__ 0444
+
+#define PERM_rw_______ 0600
+#define PERM_rw_r_____ 0640
+#define PERM_rw_r__r__ 0644
+#define PERM_rw_rw_r__ 0664
+#define PERM_rw_rw_rw_ 0666
+
+#define PERM__w_______ 0200
+#define PERM__w__w____ 0220
+#define PERM__w__w__w_ 0222
+
+#define PERM_r_x______ 0500
+#define PERM_r_xr_x___ 0550
+#define PERM_r_xr_xr_x 0555
+
+#define PERM_rwx______ 0700
+#define PERM_rwxr_x___ 0750
+#define PERM_rwxr_xr_x 0755
+#define PERM_rwxrwxr_x 0775
+#define PERM_rwxrwxrwx 0777
+
+#define PERM__wx______ 0300
+#define PERM__wx_wx___ 0330
+#define PERM__wx_wx_wx 0333
+
#define S_IRWXUGO (S_IRWXU|S_IRWXG|S_IRWXO)
#define S_IALLUGO (S_ISUID|S_ISGID|S_ISVTX|S_IRWXUGO)
#define S_IRUGO (S_IRUSR|S_IRGRP|S_IROTH)
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