scripts/coccinelle: Find PTR_ERR() to %pe candidates

Add a new Coccinelle script to identify places where PTR_ERR() is used
in print functions and suggest using the %pe format specifier instead.

For printing error pointers (i.e., a pointer for which IS_ERR() is true)
%pe will print a symbolic error name (e.g,. -EINVAL), opposed to the raw
errno (e.g,. -22) produced by PTR_ERR().
It also makes the code cleaner by saving a redundant call to PTR_ERR().

The script supports context, report, and org modes.

Example transformation:
    printk("Error: %ld\n", PTR_ERR(ptr));  // Before
    printk("Error: %pe\n", ptr);          // After

Signed-off-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Alexei Lazar <alazar@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/1758192227-701925-2-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/scripts/coccinelle/misc/ptr_err_to_pe.cocci b/scripts/coccinelle/misc/ptr_err_to_pe.cocci
new file mode 100644 (file)
index 0000000..0494c77
--- /dev/null
+++ b/scripts/coccinelle/misc/ptr_err_to_pe.cocci
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/// Use %pe format specifier instead of PTR_ERR() for printing error pointers.
+///
+/// For printing error pointers (i.e., a pointer for which IS_ERR() is true)
+/// %pe will print a symbolic error name (e.g., -EINVAL), opposed to the raw
+/// errno (e.g., -22) produced by PTR_ERR().
+/// It also makes the code cleaner by saving a redundant call to PTR_ERR().
+///
+// Confidence: High
+// Copyright: (C) 2025 NVIDIA CORPORATION & AFFILIATES.
+// URL: https://coccinelle.gitlabpages.inria.fr/website
+// Options: --no-includes --include-headers
+
+virtual context
+virtual org
+virtual report
+
+@r@
+expression ptr;
+constant fmt;
+position p;
+identifier print_func;
+@@
+* print_func(..., fmt, ..., PTR_ERR@p(ptr), ...)
+
+@script:python depends on r && report@
+p << r.p;
+@@
+coccilib.report.print_report(p[0], "WARNING: Consider using %pe to print PTR_ERR()")
+
+@script:python depends on r && org@
+p << r.p;
+@@
+coccilib.org.print_todo(p[0], "WARNING: Consider using %pe to print PTR_ERR()")